Diagnostic significance of Neospora caninum DNA detected by PCR in cattle serum.
A nested PCR that successfully detected Neospora caninum DNA in serum of cattle was used for investigation of selected abortion cases and in a study of healthy pregnant cows at an abattoir. N. caninum DNA was not detected in serum from antibody positive dams that aborted due to N. caninum, but was present in serum of some antibody negative dams that aborted due to other causes. N. caninum DNA was also found in the serum of about half of the animals that aborted of undetermined cause, but was not detected in cow sera from two beef cattle herds in Western Australia with no recent history of abortion. In the abattoir study of 79 dams and their foetuses N. caninum DNA was found in serum of 3 dams and in material from 11 foetuses. The majority of the cows and all foetuses were antibody negative. Our findings suggest that there is no obvious relationship between the presence or absence of N. caninum DNA in serum and the presence of antibodies to N. caninum in dams, the presence of N. caninum DNA in foetuses or abortion due to N. caninum. This is the first report of the detection of N. caninum DNA in serum of cattle rather than the white blood cell fraction. It indicates the presence of free tachyzoites and/or parasite DNA in circulation. The results suggest that persistent infection in the absence of antibodies is a possible outcome of N. caninum infection. Infection of foetuses in the absence of antibodies supports the possibility of persistent infection due to immunotolerance to an early in utero infection. It is therefore important to test for N. caninum DNA as well as antibodies for the detection of exposed and/or infected animals. However, the presence or absence of N. caninum antibodies or DNA did not support nor exclude N. caninum as the cause of abortion. Additional criteria are required for a positive diagnosis of abortion caused by N. caninum.
McInnes
Linda M
LM
Division of Health Sciences, School of Veterinary and Biomedical Science, Murdoch University, South Street, Murdoch, Western Australia 6150, Australia.
Ryan
Una M
UM
O'Handley
Ryan
R
Sager
Heinz
H
Forshaw
David
D
Palmer
Dieter G
DG
D000003:Abattoirs; D000034:Abortion, Veterinary / Q000209:etiology / Q000469:parasitology*; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D002417:Cattle; D002418:Cattle Diseases / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D003048:Coccidiosis / Q000097:blood / Q000175:diagnosis / Q000276:immunology / Q000662:veterinary*; D017931:DNA Primers / Q000737:chemistry; D016054:DNA, Protozoan / Q000097:blood*; D005260:Female; D005333:Fetus / Q000469:parasitology; D019084:Fluorescent Antibody Technique, Indirect / Q000662:veterinary; D018688:Neospora / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D016133:Polymerase Chain Reaction / Q000662:veterinary; D011247:Pregnancy; D015597:Pregnancy Complications, Parasitic / Q000097:blood / Q000175:diagnosis / Q000276:immunology / Q000662:veterinary; D012680:Sensitivity and Specificity; D013997:Time Factors
D000913:Antibodies, Protozoan; D017931:DNA Primers; D016054:DNA, Protozoan