David L. Hunter

SEROLOGIC SURVEY AND SERUM BIOCHEMICAL REFERENCE RANGES OF THE FREE-RANGING MOUNTAIN LION (FELIS CONCOLOR) IN CALIFORNIA

Serum samples from 58 mountain lions (Felis concolor) in California (USA) were collected between April 1987 and February 1990. Nineteen serum samples were used for serum biochemistry determinations; the ranges were similar to reference values in domestic cats, captive exotic felidae and free-ranging mountain lions. A serological survey was conducted to determine whether antibodies were present against selected infectious agents. Fifty-four (93%) of 58 sera had antibodies against feline panleukopenia virus. Fifteen (68%) of 22, 16 (28%) of 58, 11 (19%) of 58, and 10 (17%) of 58 had serum antibodies against feline reovirus, feline coronavirus, feline herpes virus, and feline calicivirus, respectively. Twenty-three (40%) of 58 and 21 (58%) of 36 had serum antibodies against Yersinia pestis and Toxoplasma gondii, respectively. Only one of 22 sera had antibodies against the somatic antigen of Dirofilaria immitis. Feline leukemia virus and feline immunodeficiency virus antigens were not detected in any mountain lions sera. All 58 sera samples were negative for antibodies to feline immunodeficiency virus and Chlamydia psittaci

Serologic survey for infectious pathogens in free-ranging American bison

From November 1991 through March 1992, we evaluated 101 free-ranging American bison (Bison bison) from Yellowstone National Park, Wyoming (USA) for exposure to infectious organisms that commonly infect cattle. No titers were detected for bluetongue virus, bovine leukemia virus, or Campylobacter fetus in these 101 bison. Detectable antibodies occurred against Anaplasma marginale (eight of 76, 11%), bovine respiratory syncytial virus (31 of 101, 31%), bovine viral diarrhea (31 of 101, 31%), bovine herpesvirus 1 (29 of 76, 38%), Leptospira interrogans icterohaemorrhagiae (four of 101, 4%), L. interrogans hardjo (seven of 101, 7%), L. interrogans autumnalis (one of 101, 1%), L. interrogans bratislava (seven of 101, 7%), L. interrogans australis (one of 101, 1%), and parainfluenza 3 virus (27 of 75, 36%). The low antibody titers and the lack of gross lesions are evidence that while previous exposure to infectious organisms may have occurred, none appeared to have active infections.

MICROORGANISMS ASSOCIATED WITH A PNEUMONIC EPIZOOTIC IN ROCKY MOUNTAIN BIGHORN SHEEP (OVIS CANADENSIS CANADENSIS)

Abstract A comprehensive study of a pneumonic epizootic was initiated when the first signs of disease were noted in a metapopulation of bighorn sheep inhabiting Hells Canyon, bordering Idaho, Oregon, and Washington. A total of 92 bighorn sheep were tested for etiologic agents during the following 6-mo study period. The study population included bighorn sheep believed to be the subpopulation in which disease was first noted, and these sheep were translocated to a holding facility in an effort to contain the disease (group A1, n = 72); bighorn sheep in other subpopulations (group A2) with evidence of clinical disease were captured, sampled, given antibiotics, and released (n = 8) and those that were found dead were necropsied (n = 12). Samples, including oropharyngeal and nasal swabs, and lung and liver tissue were collected from the bighorn sheep identified above. Tissue was collected at necropsy from 60 group A1 bighorn sheep that died following translocation, and samples were cultured for bacteria and viruses. Blood samples were tested for antibodies against known respiratory viruses, and histopathology was conducted on tissue samples. The major cause of death in both group A1 and group A2 bighorn sheep was a rapidly developing fibrinous bronchopneumonia. Multiple biovariants of Pasteurella were isolated from oropharyngeal and nasal samples from both groups, and Mycoplasma ovipneumonia was isolated from five group A1 oropharyngeal samples. Organisms isolated from lung tissue included Pasteurella multocida multocida a and Pasteurella trehalosi, both of which differentiated into multiple strains by restriction enzyme analysis, and parainfluenza-3 virus (PI-3). Paired serum samples revealed >fourfold increases in titers against PI-3 and bovine respiratory syncytial viruses. It was concluded that this epizootic resulted from a complex of factors including multiple potential respiratory pathogens, none of which were identified as a primary pathogen, and possible stress factors.

EVALUATION OF EWE VACCINATION AS A TOOL FOR INCREASING BIGHORN LAMB SURVIVAL FOLLOWING PASTEURELLOSIS EPIZOOTICS

We conducted field and laboratory experiments to evaluate whether treating pregnant bighorn ewes with a combination of an experimental Pasteurella trehalosi and Mannheimia haemolytica (formerly P. haemolytica) vaccine and a commercially-available bovine P. multocida and M. haemolytica vaccine would increase lamb survival following a pneumonia epidemic. Three free-ranging bighorn herds affected by pasteurellosis outbreaks between November 1995 and June 1996 were included in the field experiment. Post-epidemic lamb survival was low in all three herds in 1996, with November lamb:ewe ratios of ≤8:100. In March 1997, thirty-six ewes (12/herd) were captured and radiocollared. Half of the ewes captured in each herd were randomly selected to receive both vaccines; the other half were injected with 0.9% saline solution as controls. Lambs born to radiocollared ewes were observed two or more times per week and were considered to have survived if they were alive in October 1997, about 6 mo after birth. Lamb survival differed among herds (range 22% to 100%), and survival of lambs born to vaccinated ewes was lower (P = 0.08) than survival of lambs born to unvaccinated ewes. Bronchopneumonia (pasteurellosis) was the dominant cause of mortality among lambs examined. We concurrently evaluated vaccine effects on survival of lambs born to seven captive ewes removed from the wild during the 1995–96 epidemic. Antibody titers were high in captive ewes prior to vaccination, and vaccines failed to enhance antibody titers in treated captive ewes. None of the captive-born lambs survived. These data suggest that, using existing technology, vaccinating bighorn ewes following pneumonia epidemics has little chance of increasing neonatal survival and population recovery.

BACTERIA ISOLATED FROM NASAL AND TONSILLAR SAMPLES OF CLINICALLY HEALTHY ROCKY MOUNTAIN BIGHORN AND DOMESTIC SHEEP

Nasal and tonsillar samples were collected from 14 free-ranging clinically healthy Rocky Mountain bighorn sheep (Ovis canadensis canadensis) and 10 domestic sheep (Ovis aries). We identified 194 bacterial isolates, including 101 from bighorn and 93 from domestic sheep. Of these isolates, 115 were gram-positive and 79 were gram-negative. Staphylococcus species were the most numerous gram-positive organisms and had a higher incidence in samples from domestic than from bighorn sheep. In contrast Streptococcus species were present in higher numbers in samples from bighorn sheep. Pasteurella haemolytica, the most common gram-negative bacterium, was isolated from five of five tonsillar but from none of ten nasal samples of domestic sheep, and from seven of eight tonsillar and three of ten nasal samples of bighorn sheep. Most bacteria isolated were considered opportunistic pathogens. However, of the bacteria isolated, P. haemolytica, P. multocida, and Actinomyces pyogenes are most frequently associated with respiratory disease.

Sharing of Pasteurella spp. between free-ranging bighorn sheep and feral goats.

Pasteurella spp. were isolated from feral goats and free-ranging bighorn sheep (Ovis canadensis canadensis) in the Hells Canyon National Recreation Area bordering Idaho, Oregon, and Washington (USA). Biovariant 1 Pasteurella haemolytica organisms were isolated from one goat and one of two bighorn sheep found in close association. Both isolates produced leukotoxin and had identical electrophoretic patterns of DNA fragments following cutting with restriction endonuclease HaeIII. Similarly Pasteurella multocida multocida a isolates cultured from the goat and one of the bighorn sheep had D type capsules, serotype 4 somatic antigens, produced dermonecrotoxin and had identical HaeIII electrophoretic profiles. A biovariant Uβ P. haemolytica strain isolated from two other feral goats, not known to have been closely associated with bighorn sheep, did not produce leukotoxin but had biochemical utilization and HaeIII electrophoretic profiles identical to those of isolates from bighorn sheep. It was concluded that identical Pasteurella strains were shared by the goats and bighorn sheep. Although the direction of transmission could not be established, evidence suggests transmission of strains from goats to bighorn sheep. Goats may serve as a reservoir of Pasteurella strains that may be virulent in bighorn sheep; therefore, goats in bighorn sheep habitat should be managed to prevent contact with bighorn sheep. Bighorn sheep which have nose-to-nose contact with goats should be removed from the habitat.

SUSCEPTIBILITY OF ELK (CERVUS ELAPHUS) TO EXPERIMENTAL INFECTION WITH ANAPLASMA MARGINALE AND A. OVIS

Anaplasma ovis was experimentally transmitted from domestic sheep to elk (Cervus elaphus) and hack to splenectomized sheep. No rickettsemias were detected but serum from three of seven experimentally inoculated elk developed Anaplasma spp.-reactive antibody as measured by indirect immunofluorescence (IIF) or by the rapid card agglutination and complement fixation assays. Three elk were experimentally infected with A. marginale. The rickettsiae were detected in blood of these elk and caused disease in a splenectomized domestic bovine calf after subinoculation of blood from the elk. All three elk had positive titers with IIF. No clinical signs of illness were noted in any elk inoculated with either Anaplasma species.

IMMUNOLOGIC RESPONSES OF DOMESTIC AND BIGHORN SHEEP TO A MULTIVALENT PASTEURELLA HAEMOLYTICA VACCINE

The efficacy of a Pasteurella haemolytica vaccine (serotypes A1, A2, and T10) to induce humoral antibodies and alter colonization of the upper respiratory tract by related P. haemolytica spp. strains was evaluated in 10 bighorn (Ovis canadensis canadensis) and 10 domestic (Ovis aries) sheep. Sheep of each species were divided into five pairs based on age and history of respiratory disease. One sheep in each pair was vaccinated twice 2 wk apart with 2 ml of vaccine (VAC group) and the remaining animals (NV group) were injected with 2 ml of sterile saline. Mild, transient lameness was the only observed adverse effect. Blood sera from the sheep were tested for agglutinating antibodies against whole cells of A1, A2, and T10 and for leukotoxin neutralizing antibodies. Antibody titers were expressed as the reciprocal log2 of the highest reactive dilutions. Domestic sheep >1-yr-old and two bighorn sheep with a history of A1 infection had higher titers throughout the study against A1 cells than domestic sheep <1-yr-old and big-horns without a history of A1 infection. Both domestic and bighorn sheep had log2 titers of 8 to 12 against A2 cells and 6 to 12 against T10 cells during this time. Bighorn sheep in the VAC group had 2 to 32 fold titer increases for A1 cells by 2 wk post-vaccination (PV) compared to 0 to 2 fold increases in VAC domestic sheep. Two to 16 and 0 to 8 fold increases in antibodies titers to A2 and T10 cells, respectively, were detected in sera of both VAC groups. Sera of bighorn sheep with a history of respiratory disease and all domestic sheep had log2 leukotoxin neutralizing antibody titers of 4 to 14 in contrast to ≤2 in sera of bighorn sheep without a history of respiratory disease. Neutralizing antibody titers of two bighorns without a history of respiratory disease in the VAC group increased from log2 0 to 5 in one and from 0 to 9 in the other 2 wk PV. Antibody increases in these animals were no longer evident at 16 wk PV while titers of animals with histories of disease remained relatively stable. The types and numbers of Pasteurella spp. isolated from nasal and pharyngeal swabs varied throughout the study without conclusive evidence of suppression of colonization. Although the animals were not experimentally challenged to determine the efficacy of the vaccine, one VAC and one NV bighorn sheep died following introduction of an A2 P. haemolytica strain when leukotoxin neutralizing antibodies had returned to pre-vaccination levels. This vaccine appeared to be safe for use in bighorn sheep and stimulated moderate but transient increases in antibody levels which should provide some protection against naturally occurring disease. A vaccine which would induce production of high and maintained antibodies against multiple strains of P. haemolytica would be valuable for use in bighorn sheep maintained in captivity or when captured for relocation.

HEMATOLOGIC, SEROLOGIC VALUES, HISTOPATHOLOGIC AND FECAL EVALUATIONS OF BISON FROM YELLOWSTONE PARK

Hematologic and blood chemistry parameters were measured in 149 free-ranging American bison (Bison bison) from Yellowstone National Park, Wyoming (USA). Additionally, histopathologic evaluations of lung, liver, spleen, kidney, and mesenteric and bronchial lymph nodes were made from ten animals. Forty-five fecal samples were screened for the presence of helminth ova. Leukopenia and markedly low blood urea nitrogen concentrations were the most notable differences observed from other bison populations. All tissues examined were essentially normal; there was evidence of moderate intestinal parasite burdens.

SUSCEPTIBILITY OF ELK TO LUNGWORMS FROM CATTLE

Two studies were conducted to determine the infectivity of the lungworm, (Dictyocaulus viviparus) of cattle origin, in Rocky Mountain elk (Cervus elaphus nelsoni) or wapiti. In the first study, each of three 9-mo-old elk was administered 3,000 D. viviparus larvae from cattle using a nasogastric tube. In the second study, four 16-mo-old elk were each inoculated with 2,000 D. viviparus from cattle using a nasogastric tube. Elk were observed daily for signs of respiratory disease, and fecal samples were collected during the studies and evaluated for lungworm larvae using a modified Baermann technique. One elk was euthanatized during the patent period for recovery of adult lungworms, and three elk were euthanatized after larvae were no longer detected in feces. Lungworm larvae were not detected before inoculation in any of the 16-mo-old elk, but were detected 22 days after inoculation in one elk, 23 days after inoculation in two elk and 24 days after inoculation in all four elk. The prepatent period of this cattle isolate of D. viviparus in elk is therefore 22 to 24 days. The precise prepatent period was not determined in the three 9-mo-old elk, but larvae were detected in all three elk 25 days after inoculation. Numbers of larvae ranged from 1/to 101/g feces with peak larval detection occurring 32 to 50 days after inoculation. Elk shed larvae from 22 to 83 days after inoculation, and patent periods of the parasite ranged from 24 to 62 days. Clinical signs of respiratory disease, with the exception of mild coughing after exercise, were not observed during the infections. Results from this experiment indicated that D. viviparus larvae of cattle origin can mature in elk and larvae can be passed in large numbers in feces, but this cattle isolate of D. viviparus was not highly pathogenic in elk.