Evidence of point-source exposure to Neospora caninum and protective immunity in a herd of beef cows.
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.


METHODS
Cohort study.


METHODS
208 pregnant beef cows.


METHODS
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
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.
McAllister
M M
MM
Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Illinois, Urbana 61802, USA.
Björkman
C
C
Anderson-Sprecher
R
R
Rogers
D G
DG
D000022:Abortion, Spontaneous / Q000453:epidemiology / Q000469:parasitology; D000034:Abortion, Veterinary / Q000453:epidemiology / Q000469:parasitology*; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000276:immunology* / Q000469:parasitology; D003048:Coccidiosis / Q000453:epidemiology / Q000276:immunology / Q000662:veterinary*; D015331:Cohort Studies; D004196:Disease Outbreaks / Q000662:veterinary*; D004285:Dogs; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect / Q000662:veterinary; D007074:Immunoglobulin G / Q000737:chemistry; D008297:Male; D009329:Nebraska / Q000453:epidemiology; D018688:Neospora / Q000472:pathogenicity*; D011247:Pregnancy
D000913:Antibodies, Protozoan; D007074:Immunoglobulin G