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Because results of bacterial culture and antimicrobial susceptibility testing from specimens collected from the nasal cavity are difficult to interpret, monitoring the efficacy of treatment of cats with suspected chronic bacterial URI is usually based on clinical signs of disease.
Inflammation of the lungs (pneumonia) can occur after a variety of insults. In dogs and cats, although uncommon, primary bacterial pneumonia can occur after infection with B. bronchiseptica, Mycoplasma spp., S. equi zooepidemicus, S. canis, and Yersinia pestis.61, 62, 63, 64, 68
78, 79, 80 Of 65 puppies <1 year of age with “community acquired” pneumonia in the United States, 49% were infected with B. bronchiseptica.80 Dogs with B. bronchiseptica infection were younger and had more severe disease than dogs from which other bacteria were cultured. Most cases of bacterial pneumonia in dogs and cats are secondary to other primary inflammatory events like viral infections or aspiration of oral, esophageal, or gastric contents during vomiting or regurgitation (commonly associated with megaesophagus), after aspiration because of pharyngeal or laryngeal function abnormalities, during anesthesia recovery, and after inhalation of foreign bodies.81, 82, 83 In addition, bacterial pneumonia can develop in the presence of immunodeficiency syndromes. Secondary bacterial pneumonia potentially could develop as a result of other pulmonary or airway diseases like neoplasia, ciliary dyskinesia, bronchiectasis, and collapsing airways.
Common organisms isolated from dogs and cats with lower respiratory disease include E. coli, Pasteurella spp., Streptococcus spp, B. bronchiseptica, Enterococcus spp., Mycoplasma spp., S. pseudintermedius and other coagulase‐positive Staphylococcus spp., and Pseudomonas spp.78, 79, 80, 84, 85, 86, 87
Propionibacterium acnes is an aerotolerant, anaerobic, Gram-positive, rod-shaped bacterium commonly isolated from humans. It is often implicated in acne vulgaris and occasionally in postoperative and implant-associated infections. In dogs, this bacterium can be isolated as a commensal from the skin, intestinal tract, and oral cavity; however, unlike humans, there is little evidence of pathogenicity.
Urinary tract infections (UTIs) are either temporary or permanent breaches in host defense mechanisms that allow microbes, mainly bacteria, to adhere, multiply, and persist within the urinary tract. The main clinical features of UTI are dysuria, pollakiuria, and hematuria. These are most commonly caused by Escherichia coli; other uropathogens include Gram-positive cocci, Proteus spp. Klebsiella spp., Pasteurella spp., Mycoplasma spp., Enterobacter spp. and Pseudomonas spp.. However, P. acnes has not been previously reported as a causative agent of UTI in dogs.
Here we report the presentation and clinical course of a UTI in a dog due to P. acnes infection.
Bovine respiratory disease complex (BRDC) is a global problem causing severe economic losses to the cattle farming industry through mortality, loss of production, and treatment costs [1, 2]. It has a complex etiology that involves various pathogens, host factors, and environmental factors. Viruses such as bovine herpes 1 virus (BoHV-1, parainfluenza virus 3 (PBIV-3), bovine respiratory syncytial Virus (BRSV), respiratory bovine coronavirus (BoCoV) and bovine viral diarrhoea virus (BVDV) in conjunction with stress factors have been implicated as causes of respiratory tract infections of cattle by immunosuppression and damage to the respiratory epithelium. A primary viral infection can be followed by an opportunistic secondary infection with bacteria like Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, or Trueperella pyogenes [2, 4, 5], but these bacteria could also act as primary pathogen. In addition it has become increasingly clear that Mycoplasmas are important contributors to BRD, either as primary pathogens or in co-infection [2, 6–9]. M. bovis is the best known Mycoplasma species causing respiratory disease [4, 7], but also M. dispar and M. bovirhinis have been associated with BRD [2, 9–11]. M. bovis has not only been identified as a primary or opportunistic pathogen in BRD in beef cattle worldwide, but it has also been implicated in other clinical manifestations in cattle, such as mastitis, otitis, arthritis, and reproductive disorders. M. bovirhinis and M. dispar are regularly isolated from the nasal cavity of cattle with respiratory disease and are usually regarded as an opportunistic pathogen in respiratory diseases [7, 12].
Bacteriological, serological and histopathological examinations are important tools to detect particular animal-carriers of Mycoplasma, however, these assays are time-consuming, insensitive and can give false positive results. Bronchoalveolar lavage fluid (BALF) from calves with BRD may contain various potential pathogens, but additional antibiotic use in the affected herds can inhibit cultivation and thereby can cause false-negative test results. In BRD, differential diagnosis of these pathogens with rapid turnaround time procedure is essential to implement appropriate treatment and intervention measures in a timely manner. Rapid detection of these pathogens at the early stage of outbreak can contribute substantially to minimize the spread of infection and increase treatment efficiency. Today quick, highly sensitive and species-specific PCRs are used in the diagnosis of Mycoplasma-associated diseases for M. dispar [14, 15], M. bovis [4, 16] and M. bovirhinis in BALF or nasal swabs. Combining a 16S Ribosomal DNA PCR with denaturing gradient gel electrophoresis fingerprinting (PCR/DGGE) enabled the simultaneous detection of mixed Mycoplasma populations, however information about the detection limit in clinical samples is limited. Additionally, a DNA microarray assay was developed for the parallel detection of 37 Mycoplasma species, in which species-specific probes derived from the 23S rRNA and tuf genes were used for species differentiation.
Multiplex real-time PCR could be a promising and practical approach to speed up the differential diagnosis from 1 to 2 weeks for traditional culture to 24 h, with limited expenses. This will make diagnostic testing more accessible for veterinary practitioners and thereby improve BRD diagnosis. This report describes the RespoCheck triplex PCR developed by Central Veterinary Institute (CVI, Lelystad, The Netherlands) for detection of three Mycoplasma species.
Respiratory illness is traditionally regarded as the disease of the growing pig, and has historically been associated with bacterial infections such as Mycoplasma hyopneumoniae [1–3] and Actinobacillus pleuropneumoniae [4–6]. These bacteria still are of great importance, but the continuously increasing herd sizes have complicated the clinical picture. As the number of transmission events between pigs in a population is equal to the number of pigs multiplied with the number of pigs minus one [x = n * (n − 1)], they will escalate as the herd size increase. Thus, the number of transmission events between pigs will increase with a factor of around four if a population is doubled and with a factor of around 100 if a population is enlarged ten times.
The increased number of transmissions between pigs may increase the influence of other microbes. M. hyopneumoniae and A. pleuropneumoniae are important pathogenic microbes, but co-infections may intensify or prolong clinical signs of respiratory disease [8–11]. It has also been observed that the incidence of respiratory illness may vary with season. Therefore, infections in the respiratory tract of grower pigs have become regarded as a syndrome rather than linked to single microorganisms [11, 13, 14]. This syndrome is referred to as the porcine respiratory disease complex (PRDC). As stated above PRDC is regarded to be dominated by bacterial species, and important primarily pathogenic bacterial species include M. hyopneumoniae [1–3] and A. pleuropneumoniae [4–6]. The frequent demonstration of interferon-α in serum in growers during the first week after arrival to fattening herds [15, 16] suggest that PRDC can be associated with viral infections, and that PRDC can also include the influence of secondary invaders such as Pasteurella spp [17, 18].
When Sweden in 1986 as the first country in the world banned the use of low dose antibiotics in animal feed for growth promotion, some introductory health disturbances were recorded. As a consequence, a strict age segregated rearing from birth to slaughter was implemented in a large scale, which improved health as well as productivity [19, 20]. As seen in Fig. 1, the incidence of recorded pathogenic lesions in the respiratory tract at slaughter decreased during the last decade of the twentieth century. The registrations of pneumonia at slaughter has remained stable at that level since then. In contrast, the incidence of recorded pleuritis at slaughter has continuously increased since the year 2000, as has the clinical evidence of actinobacillosis. Discussions concerning the reason for this increase has included suggestions of introduction of new strains, or mutation of existing strains of A. pleuropneumoniae. However, acute actinobacillosis has in Sweden historically been dominated by serotype 2, and is still dominated by that serotype. Further, Pulse Field Gel Electrophoreses has revealed that strains isolated in the twenty-first century were identical to strains isolated in the 1970s and 1980s. As a consequence, the increase of actinobacillosis and pleuritic recordings at slaughter has merely been linked to the continuously increasing herd sizes with increasing number of transmissions of microbes between pigs, within and between units.
The aim of this study was to validate the presence of A. pleuropneumoniae and M. hyopneumoniae, as well as the secondary invaders P. multocida and Streptococcus suis in pig herds with a high incidence of pleuritic lesions at slaughter.
Pericardial disease is not commonly encountered in cats. Previous studies have reported that the overall incidence of pericardial disease
in cats ranges from 1 to 2.3% [6, 22], with congestive heart failure secondary to cardiomyopathy being the
most common cause in cats. Other causes of
pericardial disease in cats include neoplasia, trauma, peritoneopericardial diaphragmatic
hernia, feline infectious peritonitis (FIP), disseminated intravascular coagulation, renal
failure and infective pericarditis [9, 27, 29]. Infective
pericarditis has rarely been reported in cats, and the reported causes of this disease include
dental infection, pneumonia, abscess, peritonitis, pyometra or idiopathic [14, 17, 19, 22]. In these
cases, the long-term use of appropriate antibiotics could induce clinical remission [14, 19]. However,
fibrinous pericarditis, which is well recognized in cattle, has a poor prognosis and has rarely been reported in cats and dogs [20, 23].
In the present study, we described the clinical and histological findings of a feline case of
fibrinous pericarditis presumably caused by Moraxella osloensis.
A three-year-old spayed domestic short-haired cat, weighing 3.3 kg, presented to a primary
care veterinarian with a one-week history of lethargy, anorexia, dyspnea and weight loss. The
cat was group fed, liver indoors, and had no history of trauma. Thoracic radiography revealed
cardiomegaly and pleural effusion. Due to lack of response to antibiotics, the cat was
referred to the Veterinary Medical Center, Obihiro University of Agriculture and Veterinary
At the time of presentation, salient physical examination findings were tachycardia (224
beats per min), tachypnea (32 breaths per min), lethargy and thin body condition (3/9). The
remaining physical examination was unremarkable. Initial laboratory data revealed the
following abnormalities; anemia (hematocrit, 24.4%; reference limits, 34–51%), neutrophilia
(32.2 × 103/µl; reference limits, 2.3–9.8 ×
103/µl), hypoalbuminemia (2.2 g/dl; reference
limits, 2.5–3.9 g/dl), hyperglobulinemia (5.2 g/dl;
reference limits, 2.6–5.0 g/dl) and low blood urea nitrogen (8
mg/dl; reference limits, 14–28 mg/dl). Feline
immunodeficiency virus (FIV) antibody and feline leukemia virus (FeLV) antigen test (IDEXX
Laboratories, Westbrook, ME, U.S.A.) were negative. Thoracic radiography revealed an enlarged,
globoid cardiac silhouette with a large volume of pleural effusion and dorsal deviation of the
trachea (Fig. 1). Echocardiographic examination demonstrated a thickened pericardium with
mild pericardial effusion and a large volume of pleural effusion (Fig. 2). Following appropriate aseptic skin preparation, thoracocentesis was performed using a
21-gauge needle, and approximately 100 ml of pleural effusion was removed.
Fluid analysis revealed an exudate effusion with a total nucleated cell count of 162,000
cells/µl, consisting of 30% macrophages and 70% degenerative neutrophils,
and a total protein level of 3.8 g/dl. Although the pleural effusion was
submitted for aerobic and anaerobic bacterial culture tests, both cultures eventually returned
negative. Fine-needle aspiration of the thickened pericardium was performed, and cytologic
evaluation indicated a large amount of degenerative neutrophils with fewer macrophages,
lymphocytes and fibroblasts. No neoplastic cells or bacteria were identified. FIP virus
polymerase chain reaction (PCR) performed using the pleural effusion sample tested negative,
and feline coronavirus titer was medium (1:200) (IDEXX Laboratories).
The cat was treated with ampicillin (20 mg/kg IV q12h) and intravenous lactated Ringer’s
solution (3 mg/kg/hr). However, the clinical symptoms did not improve, and thoracic
radiography revealed a recurrence of the pleural effusion on day 6 of hospitalization.
Thoracocentesis was performed again, and approximately 100 ml of pleural
effusion was removed. The cat was hypothermic (35.9°C), and enrofloxacin (5 mg/kg SC q24h),
furosemide (2 mg/kg SC q12h) and benazepril hydrochloride (0.83 mg/kg PO q24h) were added to
the treatment regimen. Despite these measures, the cat developed dyspnea and died on day
Necropsy revealed a large volume of modified transudates cloudy abdominal (total nucleated
cell count of 3,200 cells/µl, and total protein level of 3.5
g/dl) and pleural effusion (total nucleated cell count of 4,400
cells/µl, and total protein level of 3.0 g/dl). The heart
was encapsulated by a pale-yellow, fibrinous substance (Fig. 3). In the cross section of the heart, the epicardium was covered with an approximately
0.5- to 1.0-cm layer of fibrin (Fig. 4). The fibrinous layer adhered to the epicardium strongly and could not be separated
easily. In addition, there was a 1.5-cm abscess adhered to the pericardium and cranial segment
of the left cranial lung lobe. Histopathological examination revealed severe exudation of
fibrin with neutrophil infiltration around the epicardium. In particular, an organized
granulation tissue was noted between the surface of the epicardium and the fibrinous layer
(Fig. 5). Bacterial colonies were also seen in the fibrinous layer (Fig. 6A). Special stains revealed that the bacterial colony consisted of small cocci that were
negatively stained with Gram’s stain (Fig. 6B and
6C). Based on these findings, the cat was diagnosed with fibrinous pericarditis
secondary to bacteria. Aerobic and anaerobic bacterial cultures were performed using samples
from the abscess, pericardial fibrinous layer, pleural effusion and ascites. The aerobic
culture performed using the abscess sample showed the growth of Moraxella
osloensis, a gram-negative coccus, and the anaerobic culture showed the growth of
Bacteroides pyogenes, a gram-negative bacillus. Moraxella
osloensis was also detected in the ascites sample. In addition,
Brevundimonas vesicularis, a gram-negative bacillus, was detected in the
abscess, ascites and pleural effusion samples. Taking into account the morphological
characteristics of the bacteria observed in the fibrinous layer, Moraxella
osloensis was suspected as the causative agent.
A previous report documented the case of cat that developed bacterial pericarditis secondary
to bacteremia from a dental procedure, which was caused by a common oropharyngeal
microorganism, Peptostreptococcus. Another case report described bacterial pericarditis in a cat with pyometra and
hematogenous spread of Escherichia coli. In addition, Enterobacteriaceae and
Staphylococcus spp. infections resulted in septic pericarditis in another
cat. Furthermore, Pasteurella multocida,
Actinomyces canis, and Fusobacterium and
Bacteroides spp. were detected in the pericardial fluid of a cat with
septic pericarditis. In the present report,
Moraxella osloensis, Bacteroides pyogenes and
Brevundimonas vesicularis were detected from the abscess, ascites and
pleural effusion. Moraxella osloensis is a normal commensal of the upper
respiratory tract in humans, and
Moraxella spp. are commonly detected in the healthy feline oral cavity
. Bacteroides spp. have been
isolated from the oral flora of cats, and
Bacteroides pyogenes has been detected in cat bite wounds in a human
vesicularis has been isolated from the external environment. It was reported that Moraxella osloensis and
Brevundimonas vesicularis could induce bacteremia and/or infective
endocarditis in immunocompromised human patients [8,
16, 28]. In
this study, histopathological examination revealed gram-negative, small cocci in the fibrinous
layer. Although Moraxella osloensis was not isolated from the bacterial
cultures of the pericardium in the present case, Moraxella osloensis was
suspected as the causative agent based on the morphologic appearance and gram staining of the
bacteria in the fibrinous pericardium. The cat reported here was not infected with FIV and
FeLV, which are known to cause immunosuppression in cats. On the other hand, a part of the
cat’s left lung was abscessed and adhered to the pericardium, suggesting a possible
respiratory origin of the bacteria. Although the infection course of these pathogens is
unidentified, it was suggested that inflammatory processes in adjacent lung parenchyma might
produce the abscess and cause the spread to the pericardium.
Previously published reports on bacterial pericarditis in cats have shown that retention of
the pericardial fluid is the main constituent, and fibrin exudation is not as severe as seen
in the present case. Based on the necropsy and histopathological examination findings, we
diagnosed this cat with fibrinous pericarditis due to bacterial infection. Fibrinous
pericarditis, which is well recognized in cattle, has rarely been reported in dogs, horses and
pigs [1, 4, 5, 23]. In cats, only
one case of the fibrinous pericarditis caused by FIP has been reported. Feline coronavirus titer of the case was medium (1:200). Therefore, we
suggested that antibody titers measured in the serum be interpreted cautiously, and that
medium titers do not have any value in diagnosing FIP. In addition, many healthy cats exposed to the feline enteric coronavirus have
titers ranging from 1:100 to 1:400. PCR
examination for the detection of FIP using a pleural effusion sample was negative. Compared
with serological tests, PCR provides the obvious advantage of directly detecting the
infection, together with higher sensitivity and specificity in case of cell-free body cavity
effusion [7, 10].
Moreover, the histopathological findings of the pericardium in the present case were not
identical to the typical findings of FIP infection.
The appropriate therapeutic approach for infective pericarditis in cats is unclear because of
the low incidence and small number of published case reports. In general, therapy for
infective pericarditis requires pericardiocentesis for drainage of the purulent effusion and
the administration of antimicrobial agents.
Appropriate antibiotic therapies have reportedly resulted in complete resolution of the
pericardial effusion in two cats [14, 19]. In contrast, pericardiectomy is the treatment of
choice for dogs and cats with evidence of infectious pericardial disease [2, 17, 25]. In human medicine, pericardiectomy is typically
reserved for people who develop constrictive pericarditis. Doppler echocardiography and cardiac catheterization have also been used for
the diagnosis of constrictive pericarditis in cats [18,
25]. In this case, aerobic and anaerobic bacterial
cultures using pleural effusion samples were performed at the time of presentation to
VMC-OUAVM. However, no bacteria were cultured and antibiotic selection based on susceptibility
testing could not be performed. Because empirically administered antibiotics could not improve
the clinical symptoms in the present case, broad-spectrum antibiotics should have been started
immediately. In this case, a large amount of ascites and pleural effusion characterized by
modified transudates were seen at necropsy. It was thought that fluid administration converted
the exudative effusion to a modified transudate. In addition, severe fibrin exudation and
subsequent organization resulted in constrictive pericarditis and induced decompensation and
congestive heart failure. It might be necessary to use cardiotonic agents for the purpose of
improvement of the heart failure, and pericardiectomy might be suitable in such cases.
Effusive-constrictive pericarditis induced by coccidioidomycosis and several neoplastic
pericardial diseases have been reported in dogs [11,
12]. However, these findings were not seen on
histological examination in the present case.
In conclusion, fibrinous pericarditis is a rare in cats, and empirical administration of
antibiotics without surgical management could be insufficient for the treatment of the
fibrinous pericarditis. This report described a rarely case of fibrinous pericarditis in a cat
secondary to bacterial infection. Based on the morphological characteristics of the bacteria,
Moraxella osloensis was suspected as the causative agent.
Respiratory infections in pigs are very important factor affecting the profitability of pig production [1, 2]. Although various bacteria or viruses could induce the respiratory infection separately, it has commonly been caused by coinfection with more pathogens under field conditions [1–3]. The most important infectious agents responsible for infection of the respiratory tract in pigs are: swine influenza virus (SIV), porcine reproductive and respiratory syndrome virus (PRRSV), Pasteurella multocida (Pm), Actinobacillus pleuropneumoniae and Mycoplasma hyopneumoniae [2, 4–6]. Besides, the above mentioned pathogens, the Haemophilus parasuis (Hps) can also be recovered from the lungs of pigs with pneumonia [1, 7–10]. In these cases Hps is often isolated along with other bacterial or viral pathogens and, therefore, the role of Hps in producing pneumonia is not clear [8, 11].
Bacterial pneumonia secondary to influenza is often observed in pigs. SIV is a significant contributor to the respiratory diseases and may predispose to secondary bacterial infection. Hps is an important and common respiratory pathogen of pigs. It can be a primary pathogen or be associated with other diseases such as SIV [3, 8]. It could be also isolated from nasal cavity, tonsils and trachea of apparently healthy pigs [8, 14]. Under favorable conditions, Hps can cause severe systemic infection characterized by fibrinous polyserositis, arthritis and meningitis [8, 11, 14]. Factors leading to systemic infection by Hps have not been clarified to date [9, 14].
Although there are previous reports of experimental reproduction of Hps or SIV infection in conventional pigs, little is known about the effect of concurrent infection with SIV and Hps on the disease severity and inflammatory response in pigs, even if this coinfection is common under field conditions [13, 15–17]. There are also limited data on the role of Hps in the production of pneumonia in the absence of other respiratory pathogens. Furthermore, the kinetics of acute phase protein (APP) response in SIV/Hps co-infected pigs has not been studied to date. As it has been shown for other pathogens, the exposure to several pathogens can lead to a stronger APP response, as compare to single infection [18–20]. Thus, in order to investigate the influence of SIV and Hps coinfection on clinical outcome, both local and systemic inflammatory response as well as pathogen shedding and load at various time points following intranasal inoculation, three experimental infections (Hps- and SIV-single infection, SIV/Hps co-infection) has been performed in the present study. The correlation between local concentration of cytokines and severity of infection (clinical score, lung score) as well as serum APP concentration has been also studied.
The acute phase response is an unspecific systemic reaction of the organism that occurs after infection or inflammation. This reaction includes changes in the concentrations of some plasma proteins called acute phase proteins (APPs). Changes of APP concentration in pigs serum have been extensively investigated during last years 2–4 but, to the best of our knowledge, no studies related to the APP behavior following influenza virus and Pasteurella multocida (Pm) coinfection has been reported.
Respiratory diseases in pigs are often considered as multifactorial problems caused by various pathogens (viral and bacterial) in combination. The most common infectious agent responsible for respiratory infection in pigs are: swine influenza virus (SIV), porcine reproductive and respiratory syndrome virus (PRRSV), Pasteurella multocida (Pm), Actinobacillus pleuropneumoniae, Mycoplasma hyopneumoniae. These pathogens may act together to increase the severity and duration of the disease. In pigs, as well as in humans, bacterial pneumonia secondary to influenza is often observed and SIV is an important contributor to the porcine respiratory disease complex (PRDC). The bacterial pathogens associated with PRDC are classified as primary or secondary pathogens, and Pm plays a key role as a secondary invader. Up to now the kinetics of acute phase response after experimental infection of pigs with SIV or Pm alone have been investigated. Exposure to multiple pathogens may result in different kinetics of APP response, as compare to monoinfection with SIV or Pm.
In this study the immune and C-reactive protein (CRP), haptoglobin (Hp), serum amyloid A (SAA) or/and pig major acute phase protein (Pig-MAP) responses after simultaneous co-infection with common porcine pathogens: SIV (H1N1 subtype) and Pm were evaluated in piglets. The correlation between concentration of investigated APP in serum and severity of infection (clinical score, lung score, turbinate score) were also studied, to estimate the utility of APP measurement in the evaluation of pigs health status.
In all coinfected pigs clinical sings including fever, coughing, nasal discharge, dyspnea and anorexia were observed. In all infected animals the rectal temperature increased over 40°C (Figure 1). Clinical score ranged between 1 and 5. In the control pigs no clinical signs of any disease were seen.
Depending upon the involvement of etiological agent, the infectious respiratory diseases of small ruminants can be categorized as follows [9, 14]:bacterial: Pasteurellosis, Ovine progressive pneumonia, mycoplasmosis, enzootic pneumonia, and caseous lymphadenitis,viral: PPR, parainfluenza, caprine arthritis encephalitis virus, and bluetongue,fungal: fungal pneumonia,parasitic: nasal myiasis and verminous pneumonia,others: enzootic nasal tumors and ovine pulmonary adenomatosis (Jaagsiekte).
Manytimes due to environmental stress, immunosuppression, and deficient managemental practices, secondary invaders more severely affect the diseased individuals; moreover, mixed infections with multiple aetiology are also common phenomena [5, 8, 13, 15].
These conditions involve respiratory tract as primary target and lesions remain confined to either upper or lower respiratory tract [7, 16]. Thus, these diseases can be grouped as follows [5, 8, 14, 17].Diseases of upper respiratory tract, namely, nasal myiasis and enzootic nasal tumors, mainly remain confined to sinus, nostrils, and nasal cavity. Various tumors like nasal polyps (adenopapillomas), squamous cell carcinomas, adenocarcinomas, lymphosarcomas, and adenomas are common in upper respiratory tracts of sheep and goats. However, the incidence rate is very low and only sporadic cases are reported.Diseases of lower respiratory tract, namely, PPR, parainfluenza, Pasteurellosis, Ovine progressive pneumonia, mycoplasmosis, caprine arthritis encephalitis virus, caseous lymphadenitis, verminous pneumonia, and many others which involve lungs and lesions, are observed in alveoli and bronchioles.
Depending upon the severity of the diseases and physical status of the infected animals, high morbidity and mortality can be recorded in animals of all age groups. These diseases alone or in combination with other associated conditions may have acute or chronic onset and are a significant cause of losses to the sheep industry [3, 10]. Thus, the respiratory diseases can also be classified on the basis of onset and duration of disease as mentioned below [3, 9, 14, 18]:acute: bluetongue, PPR, Pasteurellosis, and parainfluenza,chronic: mycoplasmosis, verminous pneumonia, nasal myiasis, and enzootic nasal tumors,progressive: Ovine progressive pneumonia, caprine arthritis encephalitis virus, caseous lymphadenitis, and pulmonary adenomatosis.
Mycoplasma alkalescens is a bovine mycoplasma species, which was originally isolated from the nasal cavity of cattle in Australia. Like many other mycoplasmas, M. alkalescens is a normal inhabitant of the upper respiratory tract, but it has also been associated with disease. M. alkalescens has mostly been implicated in mastitis in cattle. It has been isolated from bulk tank milk samples, as well as from outbreaks and sporadic cases of clinical mastitis. Furthermore, M. alkalescens has been isolated from cases of severe arthritis, and its ability to induce joint lesions has been confirmed under experimental conditions. Rosenfeld & Hill isolated M. alkalescens in pure culture from abomasum and lung of an aborted bovine foetus, while Lamm et al. found M. alkalescens in association with otitis in calves. Finally, M. alkalescens has occasionally been found in association with disorders of the respiratory tract.
Recently, 17 bronchoalveolar lavage samples from calves suffering from pneumonia in a single herd in Denmark were submitted, on two occasions, to the National Veterinary Institute for laboratory examinations. The samples were examined for the presence of bacterial pathogens, bovine respiratory mycoplasmas, as well as for the presence of bovine respiratory syncytial virus (BRSV), bovine coronavirus and parainfluenza-3 virus (PI-3). The samples were not examined for infectious bovine rhinotracheitis virus, as Denmark is considered free of this infection. Thereby, eight arginine-metabolizing mycoplasmas were isolated. In the present study the identification of the isolates as M. alkalescens is presented. This is the first report of isolation of this species in Denmark.
Bacteriological examination was performed according to standard laboratory procedures. Examination for BRSV, bovine coronavirus and PI-3 was performed using an indirect sandwich-ELISA assay. Isolation of mycoplasmas was performed according to standard laboratory procedures using a Hayflick's type of medium enriched with arginine, with and without addition of 5% of rabbit hyperimmune antiserum against Mycoplasma bovirhinis. The isolates were filtered through 0.45 μm membrane filters (Millipore), cloned and submitted to serologic identification, which was performed by the disc growth inhibition test (DGI) with 6 mm filter paper discs prepared with rabbit hyperimmune antisera against M. alkalescens PG51T (ATCC 29103; NCTC 10135), Mycoplasma arginini G230T (ATCC 23838; NCTC 10129) and Mycoplasma canadense 275CT (ATCC 29418; NCTC 10152), as well as by the indirect epi-immunofluorescence test (IF) on colonies on solid medium. Molecular identification of the isolates was performed by amplification and sequencing of their 16S rRNA genes by using universal primers.
Laboratory examinations revealed the presence of several bacterial pathogens in 15 of the 17 bronchoalveolar lavage samples, while no pathogenic bacteria were detected in the two remaining samples. Pasteurella multocida, Mannheimia haemolytica, Histophilus somni and Salmonella Dublin were found in three, three, one and one samples, respectively. Mycoplasma bovirhinis was found in five samples, while arginin-metabolizing mycoplasmas were found in eight samples. Two P. multocida, three M. bovirhinis and five arginin-metabolizing mycoplasma isolates were found as sole bacteriological findings in 10 respective samples. From five samples multiple bacterial species were isolated: M. bovirhinis was found once in combination with P. multocida and once in combination with M. haemolytica, while arginin-metabolizing mycoplasmas were found once in combination with M. haemolytica, once in combination with S. Dublin and once in combination with M. haemolytica and H. somni. No viral pathogens were detected in any of the analysed samples.
Further examinations on arginin-metabolizing mycoplasmas showed that all eight isolates could be serologically identified as M. alkalescens and that they were clearly different from the two other arginine-degrading species that are commonly found in cattle, M. canadense and M. arginini (Table 1). The reactions were clear-cut for the DGI tests showing approximately 3–5 mm broad zones of total or nearly total inhibition around the disc. In the IF test some minor cross reactions were noted when three of the isolates and the type strain of M. alkalescens PG51T were tested with anti-M. canadense 275CT hyperimmune serum. The 16S rDNA sequences of the analysed isolates were identical to each other and to the 16S rDNA sequence of the type strain M. alkalescens PG51T (GenBank accession no. U44764;), which corroborated the serological identification of the isolates as M. alkalescens.
Previous studies have shown that H. somni, M. haemolytica and P. multocida are the bacteria that are most commonly associated with bronchopneumonia in calves in Denmark, although they are also part of the normal bacterial flora of the respiratory tract. Also, S. Dublin, which is predominantly found in cattle, is capable of causing pneumonia in calves. Isolation of these bacterial species in the submitted samples most likely indicate their role as the primary cause of respiratory disease in the herd, probably in combination with unidentified environmental factors. In addition to the bacteria, M. bovirhinis and M. alkalescens were also isolated. M. bovirhinis is commonly found as a part of the normal respiratory tract microflora of cattle and is not considered to be pathogenic. M. alkalescens, however, has been found in association with disorders of the respiratory tract but its role as a respiratory pathogen remains equivocal. Experimental infections have demonstrated that M. alkalescens has the ability to colonize lung tissue, but the two strains used in the study apparently failed to produce pneumonia. In the present study, we found M. alkalescens in pure culture in five of the analysed bronchoalveolar lavage samples. This finding is, however, not sufficient to warrant a role of M. alkalescens as a cause of bronchopneumonia, since we also found two samples containing only a non-pathogenic M. bovirhinis, and two samples without any bacterial or viral pathogens, despite the fact that they derived from calves with clinical signs of a respiratory disease. The failure to detect respiratory tract pathogens in these samples may be due to i.e., their absence in a particular disease stadium when sampling took a place or due to antibiotic treatment. Taking into the consideration the overall bacteriological findings of this study, it seems likely that M. alkalescens may have had a role either as a secondary invader or as an opportunistic pathogen rather than suggesting a causal role of the organism in the pneumonia complex.
M. alkalescens is regarded as one of the most common causative agents of mastitis. So, with demonstration of the organism in a Danish cattle herd, a further member of Mycoplasma is added to the group of bovine mastitis-inducing microorganisms in Denmark. The only mycoplasma species isolated from clinical outbreaks of mastitis in Denmark so far has been Mycoplasma bovis, while other mastitis-inducing species, Mycoplasma bovigenitalium and M. canadense, have been isolated only from the respiratory and the genital tract and semen samples. Further investigations are needed in order to determine the prevalence of M. alkalescens in the Danish cattle population and, indeed, to draw a firm conclusions on its importance in disease conditions other than mastitis.
Bovine respiratory syncytial virus (BRSV) is an economically significant pathogen in cattle production, as it is one of the most important causes of lower respiratory tract infections in calves. In dairy cattle, BRSV infection usually occurs in young calves aged between 2 weeks and 9 months. Adult animals with subclinical infection are the main source of infection, since reinfections are common in the herds [1, 4, 5].
BRSV, bovine herpesvirus 1 (BoHV-1), bovine viral diarrhea virus (BVDV) and bovine parainfluenza type-3 (PI-3) are considered primary agents involved in the bovine respiratory complex. Additionally, secondary infection by Pasteurella multocida, Histophilus somni and mycoplasmas contribute to the aggravation of the disease. Clinical signs are characterized by respiratory symptoms, initially with moderated intensity, such as nasal and ocular discharges which can be aggravated leading to pneumonia. However, mainly in calves, an acute and severe onset is also observed, due to maternal antibodies not effectively protect against BRSV infection.
Considering the high prevalence of the disease, several studies determined risk factors involved in the epidemiology of BRSV. In Europe, risk factors were mainly attributed to herd size, herd density, purchasing of new animals, geographic location of the farms, herd type and concomitant BVDV infection [7–11]. Similar studies have also been performed in some Latin American countries and they showed that most of the animals probably have already been exposed to the virus with consequent high BRSV prevalence in cattle herds. In these countries, herd size, age group, presence of bordering farms, herd type and geographic location of the farms were the main risk factors associated with BRSV infection [12–16].
In Brazil, BRSV was first diagnosed in calves in the state of Rio Grande do Sul and some studies have shown that BRSV infection is widespread in Southern and Southeastern Brazil, with high serological prevalence rates [18–20]. Nevertheless, research has not been conducted in order to verify possible risk factors involved in BRSV epidemiology. Due to this, the current study aimed to determine antibody prevalence against BRSV and investigate some risk factors associated with BRSV seroprevalence in herds of an important milk producing region in São Paulo State, Brazil.
Ureaplasmas, also belong to the same family as the Mycoplasmas, and are pathogenic bacteria which were initially associated with urogenital tract infections but have also been isolated from pneumonic bovine lungs [10, 68, 75]. The species Ureaplasma diversum has been associated with clinical respiratory disease [75, 76]. As Ureaplasma was found to be present in pneumonic lung tissue samples from calves which died from BRD, this genus may be an important contributor to BRD which is often overlooked.
Respiratory diseases are induced by infectious agents, managemental conditions, and/or commingling among animals. Our preliminary studies on goats from different regions of Nigeria have shown the dynamics, pattern and type, and risk factors of pneumonia in goats. We also showed that vaccination through the intranasal route induced potent mucosal immunity in goat against peste des petits ruminants virus (PPRV). None the less, due to the complex nature of caprine pneumonia, it has defied all the attempts at control using only available vaccine hitherto. This probably may be due to the bacteria complications of primary viral infection or presence of multiple pathogens in caprine pneumonia. In Nigeria, the current vaccination for PPRV is stalled by myriad challenges, leading to continuous endemicity in goats.
Vaccination and immunity are hallmark of historical success of medicine against infectious diseases. More so, harnessing mucosal immune response is an important defense against invading pathogens. Viral pathogens including PPRV, parainfluenza-3, and respiratory syncytial viruses in caprine pneumonia have been reported in our environment, while the role of bacteria including Mannheimia haemolytica (Mh) and Pasteurella multocida (Pm) was also investigated in some of our previous studies. However, PPRV and Mh have been responsible for higher percentages of the pneumonic lesions in the goats. Thus, enhancing the mucosal immune response of goats to these organisms will considerably control losses from caprine pneumonia. It was observed that goats vaccinated intranasally against PPRV exhibited better clinical response while that against Mh was not protective in the goats when clinically challenged with PPRV. Thus, there is a need to vaccinate goats with both vaccines through the intranasal route and then challenge in an experimental model, to mimic field or natural conditions. This is to proffer different strategies and framework needed in the prevention and control of the endemic caprine pneumonia in Africa at large.
The present study evaluated the protective effect of intranasal PPRV linage 1 and bacterine vaccinations.
No gross pulmonary lesions were observed in the rats between weeks 0 and 5. Gross pulmonary lesions were first identified at week 7 and by week 10, all the rats had gross pulmonary lesions. The lungs of the rats were slightly enlarged and moderately consolidated with a mottled appearance, or interspersed with single or multiple gray or white foci of increased firmness. Grossly visible necrosis, hemorrhage or pleural thickening was absent.
Bovine respiratory disease complex (BRDC) is a major cause of economic losses in the cattle industry worldwide. The most important viral agent include bovine herpesvirus type 1 (BHV-1), bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus (BRSV), and bovine parainfluenza-3 virus (BPI-3V). BRSV, belonging to the genus Pneumovirus within the family Paramyxoviridae, and is one of the most important causes of lower respiratory tract infections in calves; however, adult animals with subclinical infection are the main source of infection, since reinfections are common in the herds. It is highly prevalent in cattle, with a significant economic impact as the most important viral cause of BRDC worldwide. BVDV is a Pestivirus from the family Flaviviridae, which affects the digestive, respiratory, and reproductive systems in different production animals. Clinical signs include pyrexia, diarrhea, reduced production, and highly morbid disease but cause low mortality of infected animals. Infectious bovine rhinotracheitis (IBR) is an important infectious disease of domestic and wild cattle caused by BHV-1. This virus is a member of genus Varicellovirus, which belongs to the Herpesviridae family. Clinical signs infection includes symptoms of inflammatory reactions in respiratory, genital tracts, abortion, and neurological disorders. Betancur et al. found a statistical association between seropositive animals for BHV-1 with respect sex and age in Colombia, while Ochoa et al. reported higher infection in cows older than 5 years of age. BPI-3V is in the genus Respirovirus of the family Paramyxoviridae, which cause serious economic losses in small and large ruminants. Clinical disease is usually mild, with symptoms of fever, nasal discharge, and cough. Betancur et al. reported a statistical association between seroprevalence values for BPI-3V and age groups.
Aguachica, Rio de Oro, and La Gloria municipalities are located in Cesar department, which, in turn, is located in the Northeast of Colombia, and is very important agricultural and fish raising region, being the dual-purpose cattle husbandry one of the most important agricultural components of the regional economy, with a participation of 8% in the cattle national inventory. According to the National Agricultural Institute, the state has a population of 1,305,984 heads of cattle, being 30% located in the three municipalities.
Information about the prevalence of these viral pathogens is available from several countries in which these diseases have been reported. Nevertheless, there is very little epidemiological information on viral pathogens in cattle, mainly in the Northeast region of Colombia. Therefore, the present study was conducted to estimate the seroprevalence of respiratory viral pathogens in dual-purpose cattle and evaluate risk factors in the municipalities of Aguachica, Rio de Oro, and La Gloria in the department of Cesar.
At week 7, the rats exhibited variable retardation in weight gain. By week 10, two rats showed moderate dyspnea and severe weight loss. None of the rats exhibited severe respiratory distress or marked changes in behavior during the experiments.
Bordetella bronchiseptica is a Gram-negative bacterium capable of colonizing the respiratory tract of a large range of mammalian hosts, including mice, rats, guinea pigs, rabbits, cats, dogs, pigs, sheep, horses, and bears. B. bronchiseptica is responsible for a wide spectrum of overt respiratory diseases such as kennel cough in dogs, atrophic rhinitis in pigs, and snuffles and pneumonia in rabbits [2–4]. B. bronchiseptica can also lead to permanent asymptomatic colonization of the respiratory tract [1, 5].
In dogs, B. bronchiseptica causes tracheobronchitis with two patterns of histological lesions. One pattern consists of focal areas of epithelial degeneration, necrosis, and cellular disorganization with vacuolation and pyknosis represented by congestion in the lamina propria, infiltrated with macrophages and lymphocytes. The second pattern consists of mucopurulent exudates that accumulate in the lumen of the airway with edema in the lamina propria, marked infiltration of polymorphonuclear leukocytes and clumps of bacteria located between the cilia of the tracheobronchial epithelium.
In piglets, B. bronchiseptica can cause upper respiratory illness, leading to nonprogressive atrophic rhinitis; histologically, other common lesions include hyperplasia of the epithelium with metaplasia and deciliated cells. In rabbits, B. bronchiseptica causes a suppurative bronchopneumonia with interstitial pneumonia; histologically, peribronchial lymphocytic cuffing has been described in [1, 11]. In species other than piglets [12–14], detailed descriptions of the initial changes in the respiratory epithelium of the nasal cavity have not been reported.
Numerous B. bronchiseptica virulence factors have been implicated as being responsible for damaging the host cells. These factors include toxins such as adenylate cyclase toxin, dermonecrotic toxin, the type III secretion system, and adhesins such as filamentous hemagglutinin, pertactin, and fimbriae [15, 16]. Most of the effects of these factors have been described from in vitro studies working with isolated cell cultures exposed to the respective virulence factor.
Despite the importance of B. bronchiseptica infection in rabbits [1, 17], as well as of the lipopolysaccharide (LPS) of B. bronchiseptica as a virulence factor, no reports on the effects of the whole microorganism or its LPS using a nasal septum culture have been documented in this species. Recent work from our group with another respiratory pathogen of rabbits, Pasteurella multocida, showed damage caused by the LPS of this pathogen to the respiratory epithelium of rabbit fetuses using the same model presented in this study. In addition, the author found that the LPS of P. multocida significantly increased the number of bacteria adhering to the epithelium when this molecule was applied 30 minutes before or simultaneously with exposure to the microorganism. A similar effect has been described for the LPS of other Gram negative bacteria, such as Salmonella enterica and Helicobacter pylori.
The goal of this work was to detail the changes caused by B. bronchiseptica in the respiratory epithelium of the nasal septum of rabbits during the first hours of infection. Additionally, we sought to examine whether the LPS of this pathogen by itself could cause lesions that would complicate the damages caused by the bacterium. To test this, a novel experimental approach more similar to natural conditions was used, namely, a tissue culture from the nasal septum of fetal rabbits.
Small ruminants particularly sheep and goats contribute significantly to the economy of farmers in Mediterranean as well as African and Southeast Asian countries. These small ruminants are valuable assets because of their significant contribution to meat, milk, and wool production, and potential to replicate and grow rapidly. The great Indian leader and freedom fighter M. K. Gandhi “father of the nation” designated goats as “poor man's cow,” emphasizing the importance of small ruminants in poor countries. In India, sheep and goats play a vital role in the economy of poor, deprived, backward classes, and landless labours. To make this small ruminant based economy viable and sustainable, development of techniques for early and accurate diagnosis holds prime importance. Respiratory diseases of small ruminants are multifactorial and there are multiple etiological agents responsible for the respiratory disease complex. Out of them, bacterial diseases have drawn attention due to variable clinical manifestations, severity of diseases, and reemergence of strains resistant to a number of chemotherapeutic agents. However, sheep and goat suffer from numerous viral diseases, namely, foot-and-mouth disease, bluetongue disease, maedi-visna, orf, Tick-borne encephalomyelitis, peste des petits ruminants, sheep pox, and goat pox, as well as bacterial diseases, namely, blackleg, foot rot, caprine pleuropneumonia, contagious bovine pleuropneumonia, Pasteurellosis, mycoplasmosis, streptococcal infections, chlamydiosis, haemophilosis, Johne's disease, listeriosis, and fleece rot [3–10].
The respiratory diseases represent 5.6 per cent of all these diseases in small ruminants. Small ruminants are especially sensitive to respiratory infections, namely, viruses, bacteria, and fungi, mostly as a result of deficient management practices that make these animals more susceptible to infectious agents. The tendency of these animals to huddle and group rearing practices further predispose small ruminants to infectious and contagious diseases [6, 9]. In both sheep and goat flocks, respiratory diseases may be encountered affecting individuals or groups, resulting in poor live weight gain and high rate of mortality. This causes considerable financial losses to shepherds and goat keepers in the form of decreased meat, milk, and wool production along with reduced number of offspring. Adverse weather conditions leading to stress often contribute to onset and progression of such diseases. The condition becomes adverse when bacterial as well as viral infections are combined particularly under adverse weather conditions. Moreover, under stress, immunocompromised, pregnant, lactating, and older animals easily fall prey to respiratory habitats, namely, Streptococcus pneumoniae, Mannheimia haemolytica, Bordetella parapertussis, Mycoplasma species, Arcanobacterium pyogenes, and Pasteurella species [2, 4, 7–9, 12, 13]. Such infections pose a major obstacle to the intensive rearing of sheep and goat and diseases like PPR, bluetongue, and ovine pulmonary adenomatosis (Jaagsiekte) adversely affect international trade [2, 9, 10, 13], ultimately hampering the economy.
BK carried out bacteriological examination of samples, isolation and cloning of mycoplasmas and drafted the manuscript.
NFF carried out identification of mycoplasma isolates by DGI test and epi-immunofluorescence.
PA carried out molecular identification of mycoplasma isolates.
All authors read and approved the final manuscript.
Domestic rabbit (Oryctolagus cuniculus), especially New Zealand white rabbit, has attracted more and more attention in biomedical, immunological and pharmaceutical research, because of its intermediate size and phylogenetic proximity to primates. It played an important role in production of antibodies, eye research as well as cardiovascular disease [2, 3]. Rabbit is one of the most commonly used experimental animals and must be free of some important pathogens.
The first outbreak of rabbit hemorrhagic disease (RHD) caused by the rabbit hemorrhagic disease virus (RHDV) occurred in 1984 in Jiangsu Province, China and spread all around the world rapidly. It’s an acute and mostly fatal contagion in both domestic and wild rabbits, characterized by acute necrotizing hepatitis and hemorrhage. Actually there are three different clinical features, the pre-acute, acute and sub-acute forms. Among which the sub-acute form causes no clinical symptoms and rabbits will recover within 2~ 3 days. Rabbit rotavirus (RRV) infection was the major cause of mild to severe diarrhea in rabbits. The rotavirus isolated from infected rabbits belongs to Group A rotaviruses (RVAs), which also infect humans and other animals. It’s a highly contagious mild virus and disseminated by fecal-oral route [9–11]. Although the infection rate of RRV is high, most infections are subclinical. However, co-infection with other bacteria or viruses may cause severe enteritis and the excretion by the infected rabbits will become the contaminate source and cause new infection. Sendai virus (SV), also known as a murine parainfluenza virus type 1, belongs to Respirovirus, Paramyxoviridae family. It causes transmitted respiratory tract infections in a variety of animals. Unlike rodents, rabbits are not sensitive to SV, and the infection will only cause fever but not respiratory tract contagious in rabbits.
Despite the asymptomatic infection and low mortality of rotavirus and Sendai virus infection, the existence of these two viruses will affect the quality of experimental animals and severely interfere with the results of animal experiments on them. To improve the quality of rabbits and ensure the accuracy of animal experiments, RHDV, SV and RRV are the required inspection items ruled by the national quality standard of China.
The traditional methods for pathogen identification include etiology diagnosis, serological diagnosis as well as molecular diagnosis [14, 15]. According to the laboratory animal microbiological quality control standards of China, the recommended test methods for these viruses mainly are the etiology and serological diagnosis. Both of them are time-consuming and laborious, compared with molecular diagnostic techniques. Polymerase chain reaction (PCR) with high sensitivity and specificity is widely used in pathogeny identification [16, 17]. Reverse transcription-PCR (RT-PCR) and quantitative reverse transcription-PCR (RT-qPCR) assays had been developed for monitoring of rabbit hemorrhagic disease virus, Sendai virus as well as rabbit rotavirus [18–20]. However, the restricted throughput limited the application of PCR, even the multiplex real-time quantitative PCR could not detect more than five pathogens in one reaction. The development of rapid and sensitive multiplex diagnostic method was extremely important for rabbit health monitoring. Compared with conventional PCR methods, the Luminex technology was a high-throughput, rapid, sensitive and labor-saving multiplex assay. Conjugation of microbeads with different fluorescent dyes could differentiate as much as 100 targets in a single reaction. This technology offered a variety of applications in pathologic diagnosis [22–24].
In this study, we developed a multiplex PCR-based MagPlex-TAG assay for simultaneous detection of rabbit hemorrhagic disease virus, rabbit rotavirus and Sendai virus.
An infectious etiology for cancer was first documented in animals during the early part of the nineteenth century with the diagnosis of pulmonary adenocarcinoma in sheep (later attributable to jaagsiekte sheep retrovirus) (5). Animals are the host species for many oncogenes. Among the most studied are rodent (Abl, Int1/Wnt1, Int2, Notch1, Pim1/2, Runx, Tpl2), fowl (Erb-b, Fos, Myc, Src), feline (Myc), and fish (cyc) (6). For example, reticuloendothesliosis virus readily induces cancer in chickens (avian leucosis/sarcoma). The virus has been found in eggs intended for human consumption and vaccines prepared in eggs (7). A wide variety of viruses, mirroring their human analogs, are ubiquitous among animals in nature and their habitat (e.g., fecal coliform contamination) (8–10). Common types include viruses in the polyoma, adeno, retro, and papilloma family.
Animal viruses potentially express oncoproteins in human cells even though stringent replicate restrictions exist in the latter (11). The “hit and run” hypothesis posits that certain viruses interfere with the hosts immune system to cause cancer, yet do not integrate into the victims DNA (leaving no detectable fingerprints) (12). Newborn hamsters infected with polyoma virus have been shown to develop cancers, even though the cells of this species do not support virus replication (13). Similarly, tumors induced in immunocompetent mammals with Rous sarcoma virus do not present neutralizing antibodies (14). In contrast, some animal viruses [e.g., feline leukemia virus (FeLV)] have been observed to replicate in vitro in human cells (15, 16). Sera collected from 69% of 107 persons among 46 households with at least 1 FeLV gs-a positive cat tested positive for antibodies against FeLV (15). Although it is unclear exactly how antibodies directed toward animal viruses could have oncogenic or mitogenic effects on host cells, these findings support the idea that long-lasting “biological memory” of animal virus exposure can exist within the host in the absence of direct effects on host DNA.
Along with equine rhinitis virus (ERV) and foot and mouth disease virus (FMDV), bovine rhinitis A and B viruses (BRAV and BRBV, respectively) are species in the genus Aphthovirus, family Picornaviridae. Two serotypes of BRAV have been identified, BRAV1 and BRAV2, while BRBV consists of a single serotype. The BRAV1 strain SD-1 was isolated in Germany in 1962 from nasal secretions from a calf with rhinitis. Additional BRAV1 strains were subsequently isolated from both healthy and diseased bovines in England, Japan, Italy and the U.S. and shown to cross react in serum neutralization assays [3–6]. The sole BRBV isolate EC-11 was isolated in England in 1964 by Reed from the lung of a specific pathogen free calf with respiratory disease. Likewise, BRAV2 consists of a single specimen, strain H-1, isolated from an outbreak of respiratory disease in cattle in 1984. Despite numerous studies on bovine rhinitis viruses (BRV) in the 1960’s through mid-1980’s, little work has been published on their epidemiology and ecology the past several decades.
Bovine respiratory disease complex (BRDC) is the most economically significant disease of the cattle industry, leading to losses due to mortality, morbidity, treatment costs and feed inefficiency in excess of $750 million dollars per year in the U.S. alone. BRDC has a multifactorial etiology involving a variety of bacteria and viruses in addition to host and environmental factors. Numerous commercial vaccines including both killed and attenuated live bacteria are available. Viruses commonly included in commercial vaccine include bovine viral diarrhea virus (BVDV), bovine herpes virus 1 (BHV1), parainfluenza virus 3 (PI3) and bovine respiratory syncytial virus (BRSV). Despite their widespread use, BRDC incidence has increased over the past 20 years. BRDC pathogenesis often involves a primary viral infection which damages respiratory mucosa and alters host immune responses leading to secondary bacterial pneumonia caused by commensal bacteria already present in the respiratory tract.
Both BRAV and BRBV are established but rarely studied etiologic agents of BRDC. Experimental inoculation of calves with BRAV1 via intranasal (IN) or intratracheal (IT) routes, either singly or in combination, resulted in variable clinical signs of respiratory disease and histologic lesions consistent with pneumonia. BRAV1 was also recovered from nasal swabs of IN inoculated animals and all animals inoculated or exposed by contact seroconverted to BRAV1 by day seven post inoculation. A similar experiment using a different BRAV1 strain (RS 3x) and colostrum deprived calves failed to reproduce clinical disease but was successful in isolating BRAV1 from nasal swabs post inoculation and found histological lesions of focal rhinitis and a neutralizing antibody response in all inoculated calves. BRBV pathogenesis was investigated using intranasal inoculation of gnotobiotic calves. Clinical signs including fever, nasal discharge and increased respiration rate were observed. Foci of epithelial necrosis were observed histologically in the turbinates and trachea and interstitial pneumonia was evident in the lungs. Virus was isolated from multiple tissues and was neutralized by convalescent antiserum. In addition to controlled studies, numerous investigations of acute respiratory disease in cattle resulted in the isolation of bovine rhinitis viruses where paired acute and convalescent sera suggested a causative role for bovine rhinitis virus.
Metagenomic sequencing on nasal swabs obtained from BRDC diagnostic submissions were performed to survey viruses present. Contigs with high identity to BRAV2 and BRBV were identified in one swab. To further our understanding of the epidemiology and ecology of bovine rhinitis viruses in BRDC, a more comprehensive survey was performed.
BoHV-1 infection can cause conjunctivitis, pneumonia, genital disorders, abortions, and an upper respiratory infection known as bovine respiratory disease (BRD) or “Shipping Fever”. BoHV-1 initiates BRD by immunosuppressing cattle [24,48–50,152], which can lead to pneumonia as a result of secondary bacterial infections. BoHV-1 induced immune-suppression can result in secondary bacterial infections (Pasteurella haemolytica, Pasteurella multocida, and Haemophilus somnus for example) that cause life-threatening pneumonia. BRDC and BoHV-1 infections costs the cattle industry at least $3 billion/year in the United States [1,15,24,48–50,71,79,122,136]. Modified live vaccines are available, and in general, they prevent clinical disease in adults. However, the same vaccine strains are immunosuppressive and can cause serious disease in young calves or abortions in pregnant cows.
Like other α-herpesvirinae subfamily members, BoHV-1 establishes lifelong latency in ganglionic neurons of the peripheral nervous system following acute replication in mucosal epithelium. Virus reactivation and spread to other susceptible cattle occur after stress or corticosteroid treatment, which resembles stress. There have been increases in BoHV-1 outbreaks in vaccinated feedlot cattle, which are the result of vaccine strains reactivating from latency. The viral protein, bICP0, is crucial for productive infection and reactivation from latency. The bICP0 protein has two known functions that are important for stimulating productive infection and promoting viral pathogenesis: stimulating the activity of all viral promoters and inhibiting interferon dependent transcription. These bICP0 functions are the focus of this review.