Mycotic rumenitis in American bison (Bison bison).

Necropsies were performed on 2 American bison (Bison bison) cows, I of which died acutely and the other that died after a week of illness. Gross and microscopic lesions were consistent with severe mycotic infection of the forestomachs. Both animals had been abruptly placed on a breeder ration 1 month after calving, and had developed acidosis and subsequent fungal invasion of tissues. History and lesions in this case indicate that bison are susceptible to rumen acidosis and its sequelae.     

Haemophilus somnus bronchopneumonia in American bison (Bison bison).

Immunoperoxidase assays were performed on 21 archived formalin-fixed, paraffin-embedded tissues from from American bison (Bison bison) with bronchopneumonia. Seven of the 21 bison had positive staining for Haemophilus somnus in alveolar exudate, visceral pleura, lung parenchyma, and chronic necrotic lesions, and H. somnus was isolated from tissues from 1 of these 7 animals. Results suggest that H. somnus is a respiratory pathogen in bison.     

Chronic pneumonia and polyarthritis syndrome in a feedlot calf

A feedlot heifer was diagnosed with chronic pneumonia and polyarthritis syndrome (CPPS), which was confirmed on postmortem examination. The syndrome is caused by Mycoplasma bovis; however, available data support the theory that other pathogens play a role in predisposing to this disease. Continued research on CPPS focuses on pathogenesis, treatment, and prevention.     

Hepatic lipidosis in pregnant captive American bison (Bison bison).

Hepatic lipidosis, a hallmark lesion of lipid mobilization disorders in ruminants, was noted in four 3-year-old, pregnant bison (Bison bison) after periods of anorexia that progressed to recumbency and death. The affected bison were part of a herd at the National Animal Disease Center (NADC) that was used for brucellosis vaccine research. Microscopically, the liver contained swollen hepatocytes with numerous, variably sized, round, smoothly contoured vacuoles that displaced cytoplasmic structures. Hepatocytes in all zones of the lobule were affected equally. Hypoglycemia, decreased total carbon dioxide, elevated gamma-glutamyltransferase, elevated alkaline phosphatase, and increased nonesterified fatty acid levels were noted. As in the case of cattle, altered nutritional demands of late gestation combined with management factors such as obesity, nutrition, stress, and concomitant disease may be critical in the pathophysiology of lipid mobilization disorders in bison. Additionally, stressors unique to this research herd likely contributed to fatal hepatic lipidosis.     

Coinfection with bovine viral diarrhea virus and Mycoplasma bovis in feedlot cattle with chronic pneumonia

Chronic, antibiotic-resistant pneumonia, sometimes with concurrent polyarthritis, occurs in feedlot cattle in western Canada. The prevalence of Mycoplasma bovis, bovine viral diarrhea virus, and Haemophilus somnus was determined by using immunohistochemical staining of lung and heart tissue from 2 groups of animals with this history. Mycoplasma bovis antigen was present in 44/48 cases submitted between 1995 and 1998 (retrospective group) and 15/16 of cases from 1999 (prospective group), and was associated with pulmonary necrosis. Bovine viral diarrhea virus antigen was present in association with microscopic vascular lesions in 31/48 retrospective and 9/16 of prospective cases. Types Ib and II bovine viral diarrhea virus were isolated from 4/16 prospective cases. Haemophilus somnus antigen was present in heart, lung, or both of 15/48 retrospective and 8/16 prospective cases. The results suggest that there may be synergism between bovine viral diarrhea virus and M. bovis in this pneumonia with arthritis syndrome.     

Naturally occurring Mycoplasma bovis-associated pneumonia and polyarthritis in feedlot beef calves.

Mycoplasma bovis is perceived as an emerging cause of mortality in feedlot beef cattle. This study examined the lesions and infectious agents in naturally occurring M. bovis-associated bronchopneumonia and arthritis and the relationship of this condition with bovine viral diarrhea virus (BVDV) infection. Standardized pathologic, immunohistochemical, and microbiologic investigations were conducted on 99 calves that died or were euthanized within 60 days after arrival in 72 feedlots. Cranioventral bronchopneumonia with multiple foci of caseous necrosis was identified in 54 of 99 calves, including 30 with concurrent fibrinosuppurative bronchopneumonia typical of pneumonic pasteurellosis. Mycoplasma bovis was consistently identified in these lesions by culture and immunohistochemistry, but also commonly in healthy lungs and those with pneumonia of other causes. Focal lesions of coagulation necrosis, typical of pneumonic pasteurellosis, were often infected with both Mannheimia haemolytica and M. bovis. Arthritis was present in 25 of 54 (46%) calves with M. bovis pneumonia, and all calves with arthritis had pneumonia. BVDV infection was more common in calves with lesions of bacterial pneumonia than in those dying of other causes, but BVDV infection was not more common in calves with caseonecrotic bronchopneumonia than those with fibrinosuppurative bronchopneumonia. Retrospective analysis identified cases of M. bovis pneumonia in the early 1980s that had milder lesions than the current cases. The findings suggest that, in at least some calves, M. bovis induces caseonecrotic bronchopneumonia within the lesions of pneumonic pasteurellosis.     

Malignant catarrhal fever in a bison (Bison bison) feedlot, 1993-2000.

A fatal enteric syndrome was identified in American bison (Bison bison) at a large feedlot in the American Midwest in early 1998. An estimated 150 bison died of the syndrome between January 1998 and December 1999. The syndrome was identified as malignant catarrhal fever (MCF), primarily the alimentary form. Clinical onset was acute, and most affected bison died within 1-3 days; none recovered. Consistent lesions were hemorrhagic cystitis, ulcerative enterotyphlocolitis, and arteritis-phlebitis. Vasculitis was milder and more localized than that in cattle with MCF, and in contrast to the situation in cattle, lymphadenomegaly was minimal. Virtually all affected bison examined were positive for ovine herpesvirus 2 (OvHV-2) by polymerase chain reaction (PCR) assay. A retrospective study of archived tissues established that MCF occurred in the yard as early as 1993. A prospective study was undertaken to establish the importance of MCF relative to other fatal diseases at the feedlot. The fate of a group of 300 healthy male bison in a consignment of 1,101 animals was followed for up to 7 months to slaughter. At entry, 23% (71/300) of bison were seropositive for MCF viruses, and 11% (8/71) of these seropositive bison were PCR positive for OvHV-2. Forty seronegative bison were selected at random from the group, and all were PCR negative for OvHV-2. There was no change in seroprevalence in the group during the investigation. The minimum infection rate for MCF virus was 36.3% (93/256). Twenty-two (7.3%) of the 300 bison in the feedlot died. Of these, 15 had MCF, 4 had acute or chronic pneumonia, and 3 were unexamined. Losses in the entire consignment were higher (98/1,101; 8.8% death loss); 76% of deaths were attributable to MCF. The study failed to reveal a relationship between subclinical infection and development of clinical disease.     

Pasteurellaceae isolated from tonsillar samples of commercially-reared American bison (Bison bison).

As commercial producers of American bison (Bison bison) become more numerous, concerns relative to bison health management increase. Since loss due to respiratory disease associated with Pasteurella and related Pasteurellaceae is a major concern for cattle producers, a study was conducted to determine what types of Pasteurellaceae are carried by bison to evaluate the potential of pneumonic pasteurellosis in bison herds where management practices are comparable to those used for cattle. Tonsillar biopsies, collected in May (n = 29) and August (n = 25) 1997 from 24- to 30-month-old bison bulls, at the time of slaughter were cultured for Pasteurellaceae. Pasteurella spp. were isolated from all the samples collected in May. These included isolates identified as P. haemolytica, trehalosi, testudinis, and multocida subsp. multocida a and multocida b. Actinobacillus spp. and Haemophilus somnus were also isolated from some samples. Pasteurella spp., haemolytica, trehalosi, and multocida subsp. multocida a, multocida b and septica, plus 2 nonspeciated indole-positive biotypes, U2 and U16, were isolated from the second group of tonsil samples. Most of these organisms, including P. haemolytica, P. multocida subsp., and H. somnus are associated with disease in domestic livestock and should be regarded as potential pathogens for bison, particularly in animals which become stressed by management practices commonly used with cattle such as herding, crowding, and shipping.     

Characterization of putative Haemophilus somnus isolates from tonsils of American bison (Bison bison).

Three Haemophilus somnus isolates (2a, 3a, and 27b) and one H. somnus-like (13b) isolate from tonsils of commercially reared American bison were compared with 2 known H. somnus isolates from cattle, namely, 2336, shown to cause respiratory disease, and 129Pt, from the prepuce of an asymptomatic bull. All H. somnus isolates, but not the H. somnus-like isolate, required CO2 for growth. Biochemical utilization profiles were identical for bison and bovine H. somnus isolates with the exception of alpha-fucosidase production by isolate 3a. Isolate 27a varied from 2a, 2336 and 129Pt by hemolysis of bovine erythrocytes. Isolate 13b hemolyzed sheep but not bovine or bison erythrocytes and varied from other isolates in biochemical utilization tests. Outer membrane protein profiles of 2a, 3a and 27a were almost identical with those of bovine isolate 2336 and similar to that of 129Pt, but quite different from that of 13b. Western blots of bison isolates were similar to that of the virulent bovine 2336 isolate, including detection of high molecular mass antigens above 100 kDa and the 76 kDa antigens associated with bovine IgG2 Fc binding characteristic of virulent strains, as well as antigens of approximately 78, 60 and 40 kDa. Producers and veterinarians should be aware that H. somnus may be carried by bison and may have potential for causing diseases in bison similar to those described in cattle and sheep.     

Seasonal incidence and antibiotic susceptibility patterns of Pasteurellaceae isolated from American bison (Bison bison).

Ninety pharyngeal tonsils were collected from 2-year-old American bison (Bison bison) bulls and sampled for members of the Pasteurellaceae family. Particular attention was paid to seasonal incidence and antimicrobial resistance in serotypes and biovariants. Multiple strains of Pasteurella haemolytica (39%), P. trehalosi (68%), P. multocida (34%) and Haemophilus somnus (13%) were cultured from 86 out of the 90 (96%) tonsil samples. Pasteurella trehalosi was the most common and evenly distributed of the organisms recovered. Pasteurella haemolytica was found in fewer numbers than P. trehalosi, but showed an increase in number of isolates recovered with each sampling period. Pasteurella multocida, both A and D capsular types, was recovered from all sampling periods. No serotype pattern was observed in any of the animal groups sampled. One hundred twenty-seven of 147 (86%) of the isolates were resistant to at least 1 antibiotic, 95/147 (65%) to at least 2 different antibiotics, and 16/147 (11%) to at least 3 antibiotics. The most common resistance pattern observed was to neomycin and spectinomycin (73/147) (49%).     

Persistent right aortic arch in a yearling captive wood bison (Bison bison athabascae).

An undersized, 16-mo-old, captive wood bison (Bison bison athabascae) was observed with dysphagia and postprandial regurgitation. The animal died shortly after anesthesia was initiated for diagnostic purposes. At necropsy, a persistent right aortic arch and aberrant left subclavian artery were diagnosed. The vascular ring structure around the esophagus and the trachea caused a megaesophagus with complete esophageal obstipation and ulcerative esophagitis. The aberrant left subclavian artery did not significantly compromise the esophagus. Persistence of the right aortic arch is relatively rare in ruminants and has not previously been reported in a bison.     

Recovery and Cryopreservation of Epididymal Sperm of Plains Bison (Bison bison bison) as a Model for Salvaging the Genetics of Wood Bison (Bison bison athabascae)

The objective of this study was to optimize recovery and cryopreservation of epididymal sperm from plains bison, as a model for wood bison. In Phase 1, cauda epididymides were recovered from bison (n = 14) immediately after slaughter, minced and incubated in Sp-TALPH buffer for 3 h at 36°C. The resulting sperm suspensions were cryopreserved in Triladyl^®, using a protocol for bovine semen. In Phase 2, epididymal sperm were cryopreserved in either Triladyl^® or Andromed^®. The mean (±SD) estimated number of sperm recovered was 468 ± 207 × 10⁶. There was an increase (p < 0.05) in the proportion of sperm with normal morphology between initial recovery and after extension (52.4 ± 4.6 vs 69.7 ± 2.4%), with a concurrent decrease (p < 0.05) in the proportion of sperm with distal droplets. Median values for progressively motile sperm in post-thaw samples (60%) were lower (p < 0.05) than that after extension or after chilling (70% for both). The mean percentages of viable sperm and of sperm with an intact acrosome were lower (p < 0.05) for frozen-thawed samples (38.7 ± 2.8 and 85.2 ± 1.1) compared with extended (66.2 ± 2.2 and 92.4 ± 0.9) or chilled (63.7 ± 2.5 and 90.0 ± 1.0) samples. Rates of cleavage, morulae and blastocyst production were not significantly different for chilled (70.9, 38.7 and 8.0%) vs post-thaw sperm (73.0, 46.0 and 6.3%). There was no significant difference between extenders for most sperm characteristics. In conclusion, we developed a functional protocol for the recovery and cryopreservation of epididymal sperm from plains bison, which may have implications for the genetic preservation of wood bison.     

An outbreak of sheep-associated malignant catarrhal fever in bison (Bison bison) after exposure to sheep at a public auction sale.

An outbreak of malignant catarrhal fever (MCF) among bison sold at an auction market was studied for an 18-month period. Forty-five of 163 bison submitted for sale from 8 different bison farms died on 7 other destination farms. The outbreak began on day 50 after the sale, peaked between days 60 and 70, and ended on day 220. Twenty-one dead bison were confirmed to be MCF cases by clinical histories, pathology, and detection of ovine herpesvirus-2 DNA in their tissues with polymerase chain reaction assays. Twenty-four dead bison were classified as suspect MCF cases from clinical histories. No cases of MCF were observed among bison remaining on originating farms or resident bison mixed with sale bison on destination farms. There were no sheep reported within 3 km of originating or destination farms, limiting bison exposure to sheep to the auction facility, where sheep were present for less than 1 day. The outbreak provides an illustration of the temporal distribution of MCF mortality expected in bison and an estimate of the time from exposure until death from MCF after a single short exposure to sheep. The study provides evidence that bison with MCF do not transmit MCF to other bison.     

Polymerase chain reaction and DNA sequencing for detection of ovine herpesvirus 2 in American bison (Bison bison).

Serum samples were collected at slaughter from 226 24-30-month-old ranch-raised, clinically normal American bison (Bison bison) bulls from North Dakota, Minnesota, Kansas, and Manitoba to assess the presence of antibodies to ovine herpesvirus 2 (OHV-2). Antibodies to OHV-2 were detected by competitive inhibition enzyme-linked immunosorbent assay in 10 of 226 (4.40%) samples. Polymerase chain reaction (PCR) analysis of sera positive for OHV-2 DNA demonstrated a 238 kilobase fragment. The nucleotide sequence of the PCR-positive samples in comparison to the reported OHV-2 nucleotide sequence resulted in a homology range of 82.8-95.4%.     

Seroprevalence of OHV-2, BVDV, BHV-1, and BRSV in ranch-raised bison (Bison bison).

Serum samples were collected at slaughter from 226 24-30-month-old American bison (Bison bison) bulls from Kansas, Minnesota, North Dakota, and Manitoba and assayed for antibodies to ovine herpesvirus type-2 (OHV-2), bovine viral diarrhea virus (BVDV), bovine herpesvirus type-1 (BHV-1), and bovine respiratory syncytial virus (BRSV). Antibodies were detected by serum neutralization for BVDV, BHV-1, and BRSV, while antibodies to OHV-2 were detected by competitive inhibition-ELISA (CI-ELISA). Detectable antibodies were found against all viruses: 10 of 226 (4.40%) against OHV-2, 125 of 226 (55.3%) against BVDV, 99 of 226 (43.8%) against BHV-1, and 208 of 226 (92.0%) against BRSV. Titers from 93.6% of the BVDV-positive animals, 79.8% of the BHV-1-positive animals, and 98.1% of the BRSV-positive animals were > or = 1.25. These data indicate that a low percentage of clinically normal bison are seropositive for OHV-2 while a high percentage of bison sampled are seropositive for BVDV, BHV-1, and BRSV.     

The efficacy of pour-on ivermectin in bison (Bison bison)

To test the effectiveness of pour-on ivermectin in parasitized bison, changes in fecal parasite egg counts after treatment with ivermectin injectable or pour-on preparations were compared to a negative control group. There was no difference between the two ivermectin groups, and both forms of ivermectin were effective in reducing fecal parasite egg counts in parasitized bison.     

Effect of Reproductive Seasonality on Gamete Quality in the North American Bison (Bison bison bison)

The objective was to investigate the effects of reproductive seasonality on gamete quality in plains bison (Bison bison bison). Epididymal sperm (n = 61 per season), collected during the breeding season (July–September), had significantly higher post‐thaw total motility (36.76 ± 14.18 vs 31.24 ± 12.74%), and lower linearity (0.36 ± 0.06 vs 0.39 ± 0.04) and wobbliness (0.49 ± 0.04 vs 0.51 ± 0.03; mean ± SD) compared to non‐breeding season (January–March) samples. Representative samples (n = 4) from each season were used in heterologous IVF trials using cattle oocytes. Cleavage, morulae and blastocyst percentage were higher for breeding vs non‐breeding season sperm samples (81.88 ± 6.8 vs 49.94 ± 6.77; 41.89 ± 13.40 vs 27.08 ± 23.21; and 30.49 ± 17.87 vs 13.72 ± 18.98%, respectively). Plains bison ovaries collected during the breeding (n = 97 pairs) and non‐breeding (n = 100 pairs) seasons were classified as luteal or follicular. Oocytes recovered from these ovaries were classified into five grades based on morphology. There was no significant difference in the number of luteal ovaries or grades of oocytes recovered. Oocytes were matured, fertilized (with frozen sperm from three bison bulls) and cultured in vitro. Cleavage percentage was higher for oocytes collected during breeding vs non‐breeding season (83.72 ± 6.42 vs 73.98 ± 6.43), with no significant difference in subsequent development to blastocysts. In summary, epididymal sperm from non‐breeding season had decreased total motility and resulted in reduced embryo production in vitro. Oocytes collected during non‐breeding season had reduced ability to be matured, fertilized and/or undergo cleavage in vitro. Data suggested that season influenced gamete quality in plains bison.     

Bronchopneumonia and polyarthritis due to Mycoplasma bovis in a calf

This case report describes gross lesions and histopathological findings in a 3-months-old calf originating from a feedlot with approximately 400 cattle. In this animal and additional 14 cattle of similar age, which were kept together in the same stable, swollen joints had occurred suddenly. The examination of this calf showed that a severe polyarthritis induced by haematogenous spread of Mycoplasma bovis following bronchopenumonia was present, which was characterised by necrotising lesions of the joint capsules and severe cartilage erosions.