title: Application of the Neospora caninum IgG avidity ELISA in assessment of chronic reproductive losses after an outbreak of neosporosis in a herd of beef cattle.
abstract: Point-source infections are most likely the cause for Neospora caninum-induced abortion outbreaks in cattle, whereas an increased annual abortion rate may be a consequence of vertical transmission. The aims of the present study were to examine the reproductive effects of neosporosis in a beef herd for 3 years, after a point-source outbreak and to use IgG avidity serology to examine the chronicity of infections and patterns of transmission. During the study, 76-78% of animals were seropositive for N. caninum. The pregnancy rate varied from 88% to 94%, without any reduction in the pregnancy rate of seropositive cows compared with seronegative cows. The annual abortion rate was 2.5-5.5%, and all but 1 abortion occurred in seropositive dams. The efficiency of vertical transmission was estimated to be 85%. Several calves, born to seronegative dams, were seropositive at 6-13 months of age, indicating a 22% mean annual rate of horizontal transmission. The mean avidity in seropositive cows increased from 30 during the initial outbreak to 74 after 3 years. The mode of IgG avidity was 21-40 during the initial abortion outbreak, 41-60 after 1 year, and 61-80 after 2 and 3 years. The results reveal high annual rates of both vertical and horizontal transmission of N. caninum in a herd of beef cows and provide further validation on the ability of the N. caninum IgG avidity ELISA to accurately assess the chronicity of infection.
authors.affiliation: Department of Ruminant Medicine and Veterinary Epidemiology, Swedish University of Agricultural Sciences, PO Box 7019, SE-750 07 Uppsala, Sweden.
authors.forename: Camilla
authors.initials: C
authors.lastname: Björkman
authors.forename: Milton M
authors.initials: MM
authors.lastname: McAllister
authors.forename: Jenny
authors.initials: J
authors.lastname: Frössling
authors.forename: Katarina
authors.initials: K
authors.lastname: Näslund
authors.forename: Felicia
authors.initials: F
authors.lastname: Leung
authors.forename: Arvid
authors.initials: A
authors.lastname: Uggla
mesh_terms: D000034:Abortion, Veterinary / Q000150:complications / Q000276:immunology / Q000469:parasitology / Q000635:transmission; D000818:Animals; D000915:Antibody Affinity; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology* / Q000276:immunology / Q000469:parasitology / Q000635:transmission*; D002908:Chronic Disease; D003048:Coccidiosis / Q000150:complications / Q000453:epidemiology / Q000635:transmission* / Q000662:veterinary*; D004196:Disease Outbreaks / Q000662:veterinary; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D007074:Immunoglobulin G / Q000097:blood*; D018688:Neospora / Q000276:immunology*; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000276:immunology / Q000469:parasitology / Q000662:veterinary*; D013997:Time Factors
chemical_list: D007074:Immunoglobulin G