p38-avidity-ELISA: examination of herds experiencing epidemic or endemic Neospora caninum-associated bovine abortion.
An enzyme-linked immunosorbent assay (ELISA) was established to measure the avidity of bovine IgG directed against p38, a surface antigen (NCSRS2) of Neospora caninum tachyzoites. In the sera of dams intravenously infected with N. caninum NC-1, the p38-specific avidity increased from initially below 40% up to avidity indices between 50 and 80% after days 23 and 91 p.i. The p38-avidity-ELISA was used to examine various herds that had experienced endemic and epidemic N. caninum-associated bovine abortions. In herds with endemic abortion, generally high avidity indices of N. caninum-specific IgG were detected. This finding and the observation of an association between the seropositivity of dams and that of their offspring suggested a predominantly vertical transmission of the parasite among the animals of these herds, thus indicating chronic infection of these cattle. In contrast, for herds experiencing epidemic abortion: (i) an association regarding seropositivity of dams and their daughters could not be shown and (ii) a generally low avidity of p38-specific IgG in the sera from aborting dams was determined. This indicates recent postnatal transmission of N. caninum in these herds. A linear regression model explaining the avidity of p38-specific IgG was significantly influenced by the time span between sampling and the occurrence of the first abortion of the epidemic in herds with an N. caninum-associated abortion storm. Another factor significantly contributing to the model was the proportion of dams at risk that had aborted in the herds (i.e. the severity of the abortion epidemic). A possible explanation for this observation is that herds experiencing heavy abortion are sampled earlier after the onset of the epidemic than others that have a less severe abortion storm.
Schares
G
G
Federal Research Centre for Virus Diseases of Animals, Institute for Epidemiological Diagnostics and Institute for Epidemiology, Seestrasse 55, D-16868, Wusterhausen, Germany. g.schares@wus.bfav.de
Bärwald
A
A
Staubach
C
C
Söndgen
P
P
Rauser
M
M
Schröder
R
R
Peters
M
M
Wurm
R
R
Selhorst
T
T
Conraths
F J
FJ
D000034:Abortion, Veterinary / Q000097:blood / Q000453:epidemiology / Q000469:parasitology*; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood / Q000276:immunology*; D000915:Antibody Affinity; D000953:Antigens, Protozoan; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000469:parasitology* / Q000635:transmission; D003048:Coccidiosis / Q000097:blood / Q000453:epidemiology / Q000469:parasitology / Q000662:veterinary*; D004196:Disease Outbreaks / Q000662:veterinary*; D019353:Endemic Diseases / Q000662:veterinary; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005260:Female; D005858:Germany / Q000453:epidemiology; D007074:Immunoglobulin G / Q000276:immunology; D018445:Infectious Disease Transmission, Vertical / Q000662:veterinary; D018688:Neospora / Q000254:growth & development; D011247:Pregnancy; D012044:Regression Analysis; D016036:Seroepidemiologic Studies
D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D007074:Immunoglobulin G