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Objective—To determine whether cows with evidence of previous infection with Neospora caninum were less likely to abort or give birth prematurely during an outbreak of neosporosis, compared with herdmates with evidence of primary infection.

Design—Cohort study.

Animals—208 pregnant beef cows.

Procedure—Aborted fetuses and calves born prematurely were examined during an outbreak of neosporosis in a herd of beef cows. Sera were collected from all cows during the outbreak and again 71 days later. Cows were classified into groups on the basis of normal and abnormal reproductive outcomes. Sera were examined, using an avidity ELISA procedure for N caninum, and results were compared between groups and among time points.

Results—Antibody concentrations decreased significantly and IgG avidity values increased significantly over time. During the outbreak, cows with normal reproductive outcomes were significantly more likely to have high IgG avidity values than cows with abnormal reproductive outcomes.

Conclusions and Clinical Relevance—The herd had numerous abortions and premature births with evidence of recent point-source exposure to N caninum. Therefore, to reduce risk of transmission of N caninum to cattle, attempts should be made to prevent canine feces from contaminating feed, especially feedstuffs used to prepare mixed rations for cattle. Cows with evidence of previous exposure to N caninum were less likely to abort or give birth prematurely during the outbreak than cows with primary infections with N caninum; this finding suggests development of protective immunity in previously infected cows. (J Am Vet Med Assoc 2000;217:881–887)

Full access
in Journal of the American Veterinary Medical Association


Nine 115- to 180-kg, hay-adapted, Holstein steers were fed an experimental diet with added sodium sulfate that induces polioencephalomalacia (pem). Five calves developed the disease. Thiamine concentrations in blood, csf, brain, and liver were not indicative of thiamine deficiency. The odor of hydrogen sulfide in eructated rumen gas was associated with the onset of pem. Sulfide concentrations in rumen fluid were measured 1 or 2 times a week by 2 techniques. Sulfide concentrations progressively increased in all 9 calves after the feeding of the pem-inducing diet commenced. The highest concentrations coincided with the onset of clinical signs of pem and were significantly higher in the calves that developed pem than in those that did not. This suggests that pem can result from sulfide toxicosis following excess production of sulfide in the rumen.

Free access
in American Journal of Veterinary Research



To test the hypothesis that cats are definitive hosts of Neospora caninum.


6 weaned male kittens obtained from 2 sources, and several dozen outbred mice.


Cats were fed large numbers of 3 strains of N caninum: tissue cysts in buffered saline solution, mouse brain homogenates, and whole carcass homogenates from seropositive mice. Fecal specimens were examined for 4 weeks by use of flotation tests, and bioassays were performed in mice. One cat was inoculated parenterally with tachyzoites, to determine whether cats could respond serologically to N caninum. Tissue cysts from portions of oral inocula were cultured to verify viability. Indirect fluorescent antibody serologic testing, histologic and immunohistologic examinations, cell culture, and polymerase chain reaction procedures were performed 4 to 8 weeks after oral exposure, to seek evidence of infection of cats and mice.


None of the cats or mice seroconverted to N caninum, with the exception of the single cat inoculated parenterally. Fecal shedding of oocysts was not observed, except for Isospora felis oocysts that were shed by 2 cats beginning prior to oral challenge exposure. Evidence of infection was not detected in tissues of cats or mice, with the exception of the parenterally inoculated cat.


The hypothesis that cats are definitive hosts of N caninum is not supported.

Clinical Relevance

Extermination of cats in efforts to control bovine neosporosis is not warranted. (Am J Vet Res 1998;59:441–444)

Free access
in American Journal of Veterinary Research


To measure concentrations of thiamine in blood and sulfide in ruminal fluid in cattle with polioencephalomalacia (PEM) and to evaluate temporal associations between PEM and risk factors.


Epidemiologic analysis.

Sample Population

14 steers with acute signs of PEM, 26 clinically normal steers, and records of all cattle in a feedlot for the past 6 years.


Concentrations of thiamine in blood and sulfide in ruminal fluid were measured. Values were compared between healthy steers that had been in the feedlot for 3 weeks or 2 months. Records were used to estimate the incidence of PEM and the time when cattle were at greatest risk of developing PEM.


Thiamine concentrations in steers with PEM were within reference ranges. Healthy steers had significantly greater sulfide concentrations 3 weeks after entering the feedlot, when the incidence of PEM was greatest, than 2 months after entering the feed-lot, when risk of developing PEM was low. Thiamine concentrations were within reference ranges at these times. Annually recurrent outbreaks of PEM during the summer began after initiating use of a water well containing a high content of sulfate.

Clinical Implications

Excessive ruminal sulfide production is an important factor in the pathogenesis of PEM, without concurrent thiamine deficiency. Most cases of PEM developed between 15 and 30 days after introduction to a high-sulfur diet. When water is an important source of dietary sulfur, risk of PEM may increase during hot weather. (J Am Vet Med Assoc 1997;211:1275–1279)

Free access
in Journal of the American Veterinary Medical Association


To estimate the minimum rate of abortion attributable to infection with Neospora sp in selected California dairy herds.


Prospective study.


Twenty-six dairy herds containing 19,708 cows were studied. Fourteen herds had a history of abortions attributable to neosporosis, and 12 were herds in which neosporosis had not been identified as a cause of abortions.


During a 1-year period, all available aborted fetuses were submitted to veterinary diagnostic laboratories to determine the cause of abortion. Reproductive records of cows that aborted were reviewed.


Neospora sp infection was the major cause of abortion identified (113/266 abortions, 42.5%). The majority (232/266, 87.2%) of the aborted fetuses were submitted from herds with a history of abortions attributable to neosporosis, and Neospora sp infection was identified as the causative agent in 101 of 232 (43.5%) of the abortions from these herds. Fewer aborted fetuses were submitted from the 12 herds that did not have a history of abortion attributable to Neospora sp; however, neosporosis was confirmed as a cause of abortion in 6 of these 12 herds and was identified as the causative agent in 12 of 34 (35.3%) abortions from these herds. The disease was widespread throughout the state (19/26 herds in our study). Available reproductive histories of cows that had abortions attributed to neosporosis were evaluated, and 4 cows were identified that twice aborted Neospora-in-fected fetuses.

Free access
in Journal of the American Veterinary Medical Association