Vaccination of ewes for prevention of vertical transmission of Neospora caninum.
OBJECTIVE
To evaluate the immunologic response of a killed tachyzoite vaccine against Neospora caninum and its effectiveness in preventing vertical transmission of N caninum in sheep.


METHODS
40 Dorset ewes seronegative for N caninum.


METHODS
Group-A ewes (n = 20) were vaccinated on days 1 and 126 with a killed N caninum tachyzoite preparation in a commercially available adjuvant. Group-B ewes (n = 20) were sham vaccinated. Blood samples were collected from ewes every 2 weeks and a recombinant ELISA (rELISA) was used to determine serum antibody titers against N caninum. During pregnancy, ewes were challenged with live N caninum tachyzoites. Precolostral serum was collected from lambs and tested for antibodies against N caninum by use of an indirect fluorescence antibody test and the rELISA. Tissue specimens from stillborn lambs or lambs that died within 2 weeks of birth were collected and examined for N caninum antigen and DNA by use of immunohistochemistry and polymerase chain reaction assay, respectively.


RESULTS
Serum antibody titers against N caninum were significantly higher in group-A ewes, compared with group B ewes, following vaccination. Serum antibodies against N caninum were detected in 100% (33/33) of group-B lambs and 75% (18/24) of group-A lambs. In tissue specimens, N caninum DNA was detected in 9 of 11 group-B lambs and 0 of 10 group-A lambs. Histologically, N caninum tachyzoites were observed in 4 group-A lambs and 3 group-B lambs.


CONCLUSIONS
The killed tachyzoite vaccine against N caninum stimulated a humoral immune response in sheep and provided partial protection against vertical transmission.
O'Handley
R M
RM
Parasite Biology, Epidemiology and Systematics Laboratory, Animal and Natural Resources Institute, Agricultural Research Service, United States Department of Agriculture, Beltsville, MD 20705, USA.
Morgan
S A
SA
Parker
C
C
Jenkins
M C
MC
Dubey
J P
JP
D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood / Q000276:immunology; D003048:Coccidiosis / Q000517:prevention & control* / Q000635:transmission / Q000662:veterinary*; D016054:DNA, Protozoan / Q000032:analysis; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D018445:Infectious Disease Transmission, Vertical / Q000517:prevention & control* / Q000662:veterinary*; D018688:Neospora / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D011247:Pregnancy; D016052:Protozoan Vaccines / Q000276:immunology*; D012757:Sheep Diseases / Q000276:immunology / Q000469:parasitology / Q000517:prevention & control* / Q000635:transmission; D034561:Sheep, Domestic / Q000276:immunology / Q000469:parasitology; D013997:Time Factors
D000913:Antibodies, Protozoan; D016054:DNA, Protozoan; D016052:Protozoan Vaccines