Control of anthelmintic resistant endoparasites in a commercial sheep flock through parasite community replacement.

An effort was undertaken to replace a community of sheep endoparasites that had been classified as resistant to levamisole and albendazole with a community of more susceptible parasites using a dilution approach that could be integrated into the management of a commercial flock. For this study, pastures on this sheep farm were divided into two areas: north and south. Strategically timed anthelmintic treatments combined with pasture management reduced to nondetectable levels the endemic community of anthelmintic resistant parasites in this flock and on these pastures by early summer. A group of 102 ewes, lambs, and rams were experimentally infected with third stage larvae from the more susceptible community of parasites. These sheep then seeded the south pastures with the new parasite community, while sheep on the north pastures maintained the endemic resistant community. Despite its insensitivity as a technique for detecting anthelmintic resistance, fecal egg count reduction tests at the end of the grazing season indicated that the more susceptible parasites were present on the south pastures while resistant parasites were present on the north. The following grazing season, similar protocols were used to introduce the more susceptible parasites onto the north pastures. At the end of the grazing season, fecal egg count reduction tests indicated that the new community of parasites had become established on both groups of pastures of the farm.

Evaluation of a commercial ELISA for diagnosis of paratuberculosis in cattle.

OBJECTIVE: To evaluate sensitivity and specificity of a new ELISA for antibodies against Mycobacterium avium subsp paratuberculosis. DESIGN: Cross-sectional observational survey. SAMPLE POPULATION: Serum samples from 590 cattle that were infected with M avium subsp paratuberculosis and 723 cattle that were not infected. PROCEDURE: Serum samples were tested by use of an ELISA for antibodies against M avium subsp paratuberculosis. RESULTS: Sensitivity of the test varied from 15.4 to 88.1%, depending on the clinical stage and bacterial shedding status of the cattle. CONCLUSIONS AND CLINICAL RELEVANCE: Results obtained with use of the new ELISA agreed favorably with those of a previous ELISA. Practitioners must be aware of variability in the sensitivity of the test, which depends on the clinical and shedding status of the cattle, because this may affect interpretation of test results.

Evaluation of the ability of orally administered aspirin to mitigate effects of 3-methylindole in feedlot cattle.

OBJECTIVE: To evaluate the ability of orally administered aspirin to mitigate 3-methylindole (3MI)-induced respiratory tract disease and reduced rate of gain in feedlot cattle. ANIMALS: 244 beef cattle. PROCEDURE: In a masked, randomized, controlled field trial, calves were untreated (controls) or received a single orally administered dose of aspirin (31.2 g) on entry into a feedlot. Serum 3MI concentrations were measured on days 0, 3, and 6. Rumen 3MI concentration was measured on day 3. Cattle were observed daily for clinical signs of respiratory tract disease. Lungs were evaluated at slaughter for gross pulmonary lesions. RESULTS: Mean daily gain (MDG) in cattle treated with aspirin, compared with control cattle, was 0.06 kg greater in the backgrounding unit and 0.03 kg greater for the overall feeding period. Neither serum nor rumen 3MI concentrations appeared to modify this effect. Cattle treated with aspirin were more likely to be treated for respiratory tract disease. Mortality rate, gross pulmonary lesions, and serum and rumen 3MI concentrations were similar between groups. Increased rumen 3MI concentration was associated with a small difference in risk of lung fibrosis. CONCLUSIONS AND CLINICAL RELEVANCE: Cattle given a single orally administered dose of aspirin on feedlot entry had higher MDG in the backgrounding unit and for the overall feeding period, but this finding could not be attributed to mitigation of effects of 3MI. This may have been influenced by low peak 3MI production and slow rates of gain.

Effects of 3-methylindole production and immunity against bovine respiratory syncytial virus on development of respiratory tract disease and rate of gain of feedlot cattle.

OBJECTIVE: To determine whether immunity against bovine respiratory syncytial virus (BRSV) mitigates the effects of 3-methylindole (3MI) on occurrence of bovine respiratory tract disease (BRD) and rate of gain in feedlot cattle. ANIMALS: 254 mixed-breed beef cattle. PROCEDURE: Cattle were randomly assigned to 1 of 3 groups at the time of arrival at the feedlot. One group was vaccinated with an inactivated BRSV vaccine, another was vaccinated with a modified-live BRSV vaccine, and the third was maintained as unvaccinated control cattle. On days 0 and 28, serum BRSV antibody concentrations were measured, using serum neutralizing and ELISA techniques. Serum 3MI concentrations were measured at feedlot arrival and 3 days later. Cattle were monitored for development of BRD. At slaughter, lungs were evaluated grossly for chronic lesions. RESULTS: Higher serum 3MI concentrations early in the feeding period were associated with lower mean daily gain. Control cattle were more likely to be treated for BRD after day 3, compared with cattle vaccinated with the modified-live BRSV vaccine. Humoral immunity against BRSV did not appear to modify the effect of 3MI on development of BRD or mean daily gain. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that abrogating the effects of 3MI and BRSV infection may improve the health and growth performance of feedlot cattle. However, in this study, immunity against BRSV did not appear to protect against the potential synergism between 3MI and BRSV infection, possibly because of the slow rates of gain of cattle included in the study or timing of sample collection.

Survival of Mycobacterium paratuberculosis and preservation of immunoglobulin G in bovine colostrum under experimental conditions simulating pasteurization.

OBJECTIVE: To determine whether Mycobacterium paratuberculosis could survive in colostrum after pasteurization. Additionally, this study investigated the effect pasteurization had on IgG concentration in colostrum. ANIMALS: Colostrum samples were collected from cattle (beef and dairy) owned by the state of Ohio. PROCEDURE: Colostrum was divided into aliquots and inoculated with variable concentrations of M paratuberculosis (ATCC No. 19698: 10(4), 10(3), and 10(2) colony-forming units/ml). Half the samples at each concentration were subjected to pasteurization temperatures (63 C) for 30 minutes and the remainder were kept at approximately 20 to 23 C. All samples were incubated (Herrold's egg yolk medium with and without mycobactin J) and observed for growth during the next 16 weeks. Additionally, the IgG concentration of colostrum was determined by radioimmunoassay before and after pasteurization. Samples that coagulated at pasteurization temperatures were mechanically resuspended before measurement of IgG concentration. RESULTS: Growth of M paratuberculosis was retarded but not eliminated by pasteurization. Growth was observed in all unpasteurized samples incubated on Herrold's egg yolk medium with mycobactin J but in only 2 of 18 pasteurized samples similarly cultured. Growth from pasteurized samples appeared 5 to 9 weeks after growth was observed from nonpasteurized samples. Mean colostral IgG concentration was 44.4 g/L in nonpasteurized samples and 37.2 g/L in pasteurized samples, a decrease of 12.3%. High-quality colostrum (> 48 g of IgG/L) had a significantly greater loss of IgG concentration than did colostrum of lesser quality (P = 0.002). CONCLUSIONS: Pasteurization lessened, but did not eliminate, growth of M paratuberculosis from experimentally inoculated colostrum samples. Pasteurization resulted in a significant decrease in colostral IgG concentration but not to an unmanageable level that would preclude the colostrum's use for passive transfer of immunity. CLINICAL RELEVANCE: Colostrum is macrophage rich and may serve as a source of M paratuberculosis infection to calves. Pasteurization of colostrum may lessen the risk of infection, but will not totally eliminate M paratuberculosis.

Evaluation of an agar gel immunodiffusion test kit for detection of antibodies to Mycobacterium paratuberculosis in sheep.

OBJECTIVE: To determine whether a commercially available agar gel immunodiffusion test approved for detecting antibodies to Mycobacterium paratuberculosis in cattle could be used for sheep. DESIGN: Experimental trial. SAMPLE POPULATION: Serum samples from 27 sheep confirmed to have paratuberculosis by means of acid-fast staining of smears of ileal mucosa, histologic examination of tissues, or bacteriologic culture; 7 sheep with clinical signs of paratuberculosis; and 55 sheep from 5 uninfected flocks. PROCEDURE: Serum samples were tested concurrently with the commercially available test and with a previously validated agar gel immunodiffusion test. Multiple samples collected from 13 infected sheep over a period of 6 years were also tested so that each test's ability to detect onset of seropositivity could be compared. RESULTS: For both tests, results for samples from all 55 uninfected sheep were negative, results for samples from 32 of the 34 sheep with paratuberculosis were positive, and results for the remaining 2 sheep with paratuberculosis were negative. Results of both tests were in agreement for 50 of 54 samples obtained from 13 infected sheep over time. The 4 samples for which results of the 2 tests disagreed were the fourth, eighth, and ninth of 10 samples from 1 sheep and the first of 6 samples from a second sheep. For all 4 samples, the commercially available assay yielded a weak-positive result, but the previously described test yielded a negative result. CLINICAL IMPLICATIONS: The commercially available agar gel immunodiffusion test approved for use in cattle may be useful in the differential diagnosis of paratuberculosis in sheep.

Beef Quality Assurance education via satellite videoconference.

A 1.5-h satellite video program was developed for a statewide Beef Quality Assurance (BQA) producer education activity. Twenty-seven downlink sites were identified across the state, and additional known downlink sites included one each in Minnesota, Indiana, and Monterrey, Mexico. The videoconference was formally evaluated by viewers and resource people at each site. Program participants included representatives of the Ohio and National Cattlemen's Associations and two producers currently implementing BQA programs. A toll-free telephone number was available for viewer's questions during the last 15 min of air time and following the video program. A demographic data form and pre- and postconference evaluations were completed by 368 participants. Twenty-seven percent of the respondents were age 56 or older; 76% were age 36 or older. A one to five scale (strongly disagree to strongly agree) was used for evaluation. Beef Quality Assurance was considered by viewers to be an important consideration for the future in pre- (mean = 4.5, SD = .99) and post-evaluations (mean = 4.6, SD = .83). The mean response to the question regarding using more videoconferencing for agriculture programming was 3.9 (SD = .91). Four percent of participants indicated less or no videoconferencing should be used, 24% were neutral, and 72% felt more videoconferencing should be done. Comments were neutral with regard to the length of the conference (mean = 3.5, SD = .86) and the complexity of the subject matter (mean = 3.1, SD = .64). More than 88% of the participants agreed or strongly agreed that they intended to examine their overall production strategies to see where they could improve the quality of beef they produce (mean = 4.3, SD = .85). After the videoconference, 2.6% of respondents still strongly believed that BQA was not an important consideration for the future of the beef industry. The cost of all activities associated with this satellite video program was $13,000.

Isolation of Mycobacterium paratuberculosis from colostrum and milk of subclinically infected cows.

Mycobacterial culture was performed on colostrum, milk, and feces from 126 clinically normal cows of a single herd with high prevalence of Mycobacterium paratuberculosis infection. Thirty-six (28.6%) cows were determined to be shedding the organism in the feces. Of the 36 fecal Culture positive cows, M paratuberculosis was isolated from the colostrum of 8 (22.2%) and from the milk of 3 (8.3%). Cows that were heavy fecal shedders were more likely to shed the organism in the colostrum than were light fecal shedders.

Evaluation of an enzyme-linked immunosorbent assay licensed by the USDA for use in cattle for diagnosis of ovine paratuberculosis.

A commercially available Mycobacterium phlei-absorbed enzyme-linked immunosorbent assay (ELISA) approved to detect antibodies to Mycobacterium paratuberculosis in cattle was evaluated for its applicability in sheep. The potential for interference with ELISA results from cross-reacting antibodies to Corynebacterium pseudotuberculosis was also investigated. Serum samples were randomly selected from a collection of samples obtained in 1986-1991 from 6 infected and 5 noninfected sheep flocks varying in breed, age, and geographic origin. Tests were performed on sera from 27 paratuberculous sheep, confirmed by histopathology, bacteriologic culture, and/or acid-fast staining of ileal mucosal smears, and on sera from 246 noninfected sheep. The optical density of each sample was expressed as a percentage of the optical density of a known positive sheep serum sample tested on the same plate. These values were log-transformed to achieve normality of distribution, and sensitivity and specificity estimates were calculated based on 2 and 3 standard deviations above the mean of the percent positive value (PPV) of the noninfected sheep. A cutoff value of PPV > or = 55.74 resulted in an estimated sensitivity of 0.48 and a specificity of 0.95. Sera from 10 noninfected sheep with PPV above the cutoff level of 55.74% were absorbed with heat-treated C. pseudotuberculosis organisms in addition to M. phlei antigens. Sera from 14 ELISA-positive paratuberculous sheep and 23 ELISA-negative noninfected sheep were similarly treated, and results were compared. Absorption with C. pseudotuberculosis resulted in a significant decrease in PPV in all 3 groups of sheep sera, but a greater decrease was observed in the noninfected sheep with PPV above the cutoff level when compared with noninfected sheep with PPV below that level. Results of this study suggest that ELISA may be of value in screening sheep flocks for paratuberculosis, but further experimentation is needed to optimize the sensitivity and specificity of the assay. Exposure to C. pseudotuberculosis may confound results obtained by M. phlei-absorbed ELISA for paratuberculosis.

Mycobacterium paratuberculosis infection in two llamas.

Mycobacterium paratuberculosis was diagnosed in 2 llamas by bacteriologic culturing and DNA probe testing of fecal and intestinal specimens. Diarrhea and weight loss were observed in both animals. Lesions in the gastrointestinal tracts of the 2 llamas were similar to pathologic changes reported in cattle infected with M paratuberculosis.

Isolation of Mycobacterium paratuberculosis from mononuclear cells in tissues, blood, and mammary glands of cows with advanced paratuberculosis.

Seven mature dairy cows from 6 herds were obtained with history, clinical signs of disease, and laboratory findings suggestive of advanced paratuberculosis. A surgically implanted collection chamber was used to obtain peripheral tissue fluid. Blood, mammary gland flush fluid, and collection chamber flush fluid (CCFF) samples were obtained 6 times over a 2-week period from each cow. Mononuclear cell-rich portions of these fluids obtained by gradient centrifugation were submitted for bacteriologic culture of Mycobacterium paratuberculosis and for total and differential cell counts. Bacteriologic culture of feces for M paratuberculosis and complete necropsy performed on each cow at the conclusion of the study confirmed the diagnosis of paratuberculosis. Numbers of tissue macrophages obtained from CCFF samples were lower than expected. Mean (+/- SD) differential count of tissue macrophages collected from CCFF was 65.57 (+/- 23.39). Mean calculated tissue macrophages (total cell count x differential count) collected from CCFF samples was 623.1 (+/- 784.55) cells/microliters. Mycobacterium paratuberculosis was isolated from 1 of 42 (2.4%) collections of mononuclear cell-rich portions of plasma and from 2 of 42 (4.8%) CCFF samples. Mycobacterium paratuberculosis was not isolated from any collections of mammary gland flush fluid. The collection and processing techniques used in this study did not enhance detection of M paratuberculosis infection in cows with advanced paratuberculosis, beyond that of ileocecal lymph node biopsy or fecal culture.

Use of a dot enzyme-linked immunosorbent assay on absorbed sera for the diagnosis of bovine paratuberculosis.

This study describes the response of cattle to a dot enzyme-linked immunosorbent assay (ELISA) using sera absorbed with Mycobacterium phlei. Results obtained by visual observation are compared with those obtained using a densitometer. Infection status of cattle was determined by faecal culture. Cattle of different levels of exposure and disease manifestation were examined. A significantly higher dot ELISA response was observed (using both absorbed and non-absorbed sera) in animals with heavy shedding of M. paratuberculosis than in animals which tested negative by faecal culture or shed M. paratuberculosis at lower levels (P < 0.05). Paratuberculosis was diagnosed by visual determination of dot ELISA results using non-absorbed sera in 29 of 44 (65.9%) clinically-suspect animals giving positive results by faecal culture, and 85 of 93 (91.4%) cattle testing negative by faecal culture. With absorbed sera, the sensitivity of visual determination decreased to 15 of 44 (34.1%), while specificity increased to 91 of 93 (97.8%). Approximately 75% of cattle yielding positive results by dot ELISA were heavy bacterial shedders (> 1,500 colonies/g of faeces) at the time of serological testing. Comparison of the dot ELISA results determined visually with results obtained by objective densitometric measurement showed compatible specificity. Sensitivity of the dot ELISA was 65.9% for non-absorbed sera using visual evaluation and 87.5% using densitometric evaluation at a cut-off optical density value of 0.2. For absorbed sera, the values were 34.1% and 82.5%, respectively.

Serodiagnosis of paratuberculosis in sheep by use of agar gel immunodiffusion.

An agar gel immunodiffusion (AGID) test was used over a 3-year period to examine 1,871 serum samples from sheep representing 5 Mycobacterium paratuberculosis-infected flocks and 4 flocks presumed to be uninfected. Of 1,032 sheep, 31 had positive AGID test results (scoring 1 to 5), and 23 of these 31 were necropsied. Infection with M paratuberculosis was confirmed by 1 or more of the following findings: observation of typical lesions on histologic examination of sections of ileum or ileocecal lymph nodes, observation of clumps of acid-fast bacteria in mucosal smears of ileum, and isolation of the organism from feces or tissue. False-positive results on AGID testing were not found in sheep from flocks known to have exposure to Corynebacterium pseudotuberculosis. Diarrhea in infected sheep was observed infrequently; chronic, severe weight loss was the most common sign observed. On histologic examination of tissues from 20 infected sheep, 16 (80%) had diffuse lesions of the ileum and 13 (65%) had acid-fast bacteria in areas of ileal inflammation; 4 had discrete granulomas and peripheral lymphocytic infiltrates in the ileum. Sheep with diffuse lesions tended to have higher mean scores on AGID testing and examination for acid-fast bacteria, compared with those from sheep with more discrete lesions. Bacteriologic culture yielded M paratuberculosis from only 3 sheep with paratuberculosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Concurrent experimentally induced infection with Eimeria bovis and coronavirus in unweaned dairy calves.

Over a period of 3 summers, 21 colostrum-fed Holstein bull calves, 1 to 3 days old, were assigned to 7 replicates, each consisting of 3 calves. Within each replicate of 3 calves, 2 were selected at random, to be given 100,000 to 146,000 sporulated coccidia oocysts (principally Eimeria bovis) orally 60 hours after arrival at the college research farm. On the thirteenth day after coccidia inoculation, 1 of the 2 calves that had been given coccidia and the third calf that had not been inoculated, were given coronavirus by intranasal and oral routes. Calves were observed daily, and consistency of feces was scored visually. Nasal swab specimens for indirect immunofluorescent antibody testing for coronavirus and fecal samples for oocyst determination were obtained approximately every third day. Of 7 calves that were given only coronavirus, 3 developed diarrhea of short duration. Of 7 calves that were given only coccidia oocysts, 6 developed diarrhea. All 7 calves inoculated initially with coccidia and subsequently with coronavirus developed diarrhea. For 5 of 7 replicates, calves that were given coccidia and coronavirus developed diarrhea first. When overall severity, measured by fecal score and by blood in the feces, was compared, calves inoculated with coccidia followed by coronavirus were more severely affected (P less than 0.05) than were calves that were given only coronavirus. Calves that were given only coccidia oocysts appeared more severely affected than calves that were given only coronavirus, but differences were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of subjective and objective test evaluations for use of Mycobacterium phlei-adsorbed serum in a dot-enzyme-linked immunosorbent assay for diagnosis of paratuberculosis in cattle.

Use of a dot-ELISA with serum adsorbed with Mycobacterium phlei or with nonadsorbed serum was compared. In addition, results attained using visual observation were compared with those obtained using a densitometer. Infection status of cattle was determined by results of culture of feces from a number of cattle with various degrees of exposure (low prevalence and test-negative) and disease manifestation (clinical suspect vs subclinical infection). Two paratuberculosis-negative herds, fecal culture-confirmed clinically suspect cases of paratuberculosis, and cows from 2 paratuberculosis-infected herds with diagnosis confirmed on the farm (low infection rate) were tested. Significant (P less than 0.05) increase in the dot-ELISA response was found in cattle with heavy M paratuberculosis shedding when nonadsorbed and adsorbed sera were used, compared with the response in cattle that were fecal culture-negative or were shedding M paratuberculosis at lower amounts. Paratuberculosis was diagnosed by visual determination in 29 of 44 (65.9%) of fecal culture-positive, clinically suspect cattle when nonadsorbed serum was used. Results of the visual test were negative in 85 of 93 (91.4%) of the fecal culture-negative cattle when nonadsorbed serum was used. However, when using M phlei-adsorbed serum, the sensitivity of the visual determination decreased to 34.1% (15/44), and the specificity increased to 97.8% (91/93).(ABSTRACT TRUNCATED AT 250 WORDS)

Serodiagnosis of bovine paratuberculosis by use of a dot enzyme-linked immunosorbent assay.

A dot ELISA was developed for detection of antibodies to Mycobacterium paratuberculosis. The assay was evaluated by testing sera from cattle that were determined, by bacteriologic culturing of feces, to be infected with M paratuberculosis and were suspected of having clinical disease. Further evaluation involved testing sera from cattle in which M paratuberculosis had not been isolated from feces on several attempts. Results of the dot ELISA were positive for sera from 86 of 101 infected cattle, and results were negative for sera from 64 of 64 noninfected cattle. Results of conventional ELISA and agar gel immunodiffusion (AGID) tests were positive for 79 of 99 and for 51 of 101 infected cattle, respectively. The dot ELISA also was evaluated by comparing results of testing 708 sera with results of bacteriologic culturing of matched fecal samples from 262 cattle in 3 central Ohio dairy herds known to include cattle infected with M paratuberculosis. Results of the dot ELISA were positive for 25 of 39 sera from cattle with positive results on culturing of concurrently obtained fecal specimens. The dot ELISA results were negative for 661 of 669 sera from cattle with negative results to culturing of concurrently obtained fecal specimens. The 39 sera from cattle with positive results on bacteriologic culturing of matched fecal specimens had positive results for ELISA and the AGID test 25 and 14 times, respectively. The 669 sera from cattle with concurrently negative results on bacteriologic culturing of feces had negative results to ELISA and the AGID test 559 and 668 times, respectively.

Isolation of Mycobacterium paratuberculosis from the uterine flush fluids of cows with clinical paratuberculosis.

Mycobacterium paratuberculosis was isolated from the uterine flush fluids obtained from 3 to 4 cows with clinical paratuberculosis. Four cows with clinical paratuberculosis were subjected to uterine lavage, using an established embryo recovery technique, and the recovered fluids were cultured for M paratuberculosis. Mycobacterium paratuberculosis has previously been demonstrated to adhere to bovine ova. Embryos within the uterus of a superovulated cow infected with M paratuberculosis could be exposed to the organism.

Isolation of Mycobacterium paratuberculosis from washed bovine ova after in vitro exposure.

To establish whether Mycobacterium paratuberculosis could be cultured from Dulbecco phosphate-buffered saline solution (DPBSS) and to test 3 sampling methods, DPBSS supplemented with 2% fetal bovine serum was inoculated with M paratuberculosis at concentrations of 10(4), 10(3), 10(2), 10(1), and 10(0) colony-forming units/ml. The inoculated media was sampled after mixing, after centrifugation, and after centrifugation and decontamination with 0.75% hexadecylpyridinium chloride. The samples were inoculated onto 3 slants of Herrolds egg yolk medium supplemented with sodium pyruvate and mycobactin J and 1 slant without mycobactin J. Mycobacterium paratuberculosis was isolated following all 3 sampling methods for all concentrations. Treatment with hexadecylpyridinium chloride decreased the number of colonies isolated. To test the efficacy of a 10-step wash procedure for removing M paratuberculosis from bovine ova, washed zona pellucida intact bovine ova were incubated in DPBSS supplemented with 2% fetal bovine serum containing concentrations of 10(4), 10(3), 10(2), 10(1), and 10(0) colony-forming units of M paratuberculosis/ml for 12 hours at 22 C. Ten zona pellucida intact ova were removed from each concentration and washed by passing through 10 changes of DPBSS supplemented with 15% fetal bovine serum. The media from each wash step was inoculated onto slants of Herrolds egg yolk medium. The ova were included with the tenth wash step. Mycobacterium paratuberculosis was isolated from 1 of 10 tenth-wash steps at the 10(4) concentration and 5 of 10 tenth-wash steps at 10(3).

An unusual clinical and pathological variant of malignant catarrhal fever in a white-tailed deer.

A captive male white-tailed deer (Odocoileus virginianus) developed an acute illness over a 3-day period characterized predominantly by neurological, ocular and respiratory signs which were accompanied by prominent gross lesions of multiple organ systems. Histologically, a proliferative vasculitis consisting primarily of lymphocytic-lymphoblastic cellular infiltration was found in ocular, oral, respiratory, cardiac and neural tissues. The extensive nature of these infiltrations resulted in grossly apparent nodular foci in the lung, lymphoid tissue and myocardium which were suggestive of a lymphoproliferative disorder. This is contrasted to the more necrotizing nature of the vasculitis observed in other reported cases of malignant catarrhal fever in white-tailed deer. Although virus isolation was not attempted, serologic findings of antibodies to malignant catarrhal fever virus detected by indirect immunofluorescence and virus neutralization supported a diagnosis of malignant catarrhal fever in this deer.

Evidence of paratuberculosis in Ohio's white-tailed deer, as determined by an enzyme-linked immunosorbent assay.

An enzyme-linked immunosorbent assay (ELISA) was developed and used to detect antibodies to Mycobacterium paratuberculosis in serum samples obtained in December of 1983 from 954 hunter-killed white-tailed deer (Odocoileus virginianus) in 13 Ohio counties. Positive or negative status was determined by calculating a signal-to-noise ratio, a ratio between the optical density of the test serum and negative reference sera; a ratio of greater than or equal to 3.0 was considered positive. Twenty-four samples (2.5%) were found to be assay positive, using this method. A statistically significant difference among age groups was found, with those less than or equal to 6 months of age having a lower proportion of positives. Differences by sex were not observed. To determine the validity of the ELISA in deer, serum samples from 46 fallow (Dama dama) and axis deer (Axis axis) harvested from a known infected population were tested by ELISA and agar-gel immunodiffusion. The agar-gel immunodiffusion test showed evidence of exposure of the deer to M paratuberculosis or a related antigen. The ELISA closely approximated the prevalence of paratuberculosis infection as previously determined by fecal culture in this population. As a result of these tests, it was concluded that free-ranging Ohio deer have been infected with M paratuberculosis or exposed to a closely related antigen.