Submitted to: American Journal of Veterinary Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/10/2004
Publication Date: 10/5/2004
Citation: Jenkins, M.C., Tuo, W., Dubey, J.P. 2004. Vaccination of sheep with neospora caninum protein products against fetal loss associated with experimental neosporosis. American Journal of Veterinary Research 65:1404-1408. Interpretive Summary: Neospora caninum is a major cause of abortion in dairy cattle worldwide. The fetus becomes infected by virtue of the parasite transferring from the mother via the placenta during specific times of gestation. The parasites arise in the mother from either a reactivated latent infection or by ingestion of parasite stages in the environment. In the present study, pregnant ewes were immunized with an extract of N. caninum parasites. The sheep were then infected several months later with live N. caninum tachyzoites to determine if vaccination prevented clinical signs (e.g. fetal abortion) associated with neosporosis. Immunization with N. caninum tachyzoite protein improved reproductive success of vaccinated ewes two-fold over control ewes that were not given the vaccine. Also, the lambing rate in vaccinated ewes was equal to the lambing rate in ewes that were not infected with N. caninum. These results indicate that vaccination can protect sheep against congenital neosporosis, and provide a basis for testing similar vaccines in cows.
Technical Abstract: The purpose of this study was to evaluate the immunological response of a killed Neospora caninum tachyzoite vaccine and its effectiveness in preventing fetal loss associated with experimental neosporosis in an ovine model. Dorset ewes (n=15/group) were randomly allocated to 2 study groups (Groups A or B). Ewes in Group A were vaccinated on days 1 and 60 of the study with a killed N caninum tachyzoite preparation in a comercially available adjuvant. Ewes in group B were sham vaccinated with a mixture of sterile saline and adjuvant. At day 90 of pregnancy, ewes in Group A and Group B were challenged with live N caninum tachyzoites. Vaccination of ewes with N caninum antigen protected against fetal loss arising from an experimental N caninum tachyzoite challenge. Of the pregnant vaccinated ewes, 86% (12/14) gave birth to live-born lambs which was nearly 2-fold greater than the 45% lambing rate (5/11) in control ewes. The N caninum tachyzoite vaccine used in this study provided nearly 2-fold greater protection against fetal loss associated with experimental neosporosis in pregnant ewes.