Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2010
Publication Date: 5/11/2010
Citation: Almeria, S., Araujo, R., Tuo, W., Lopez-Gatius, F., Dubey, J.P., Gasbarre, L.C. 2010. Fetal death in cows experimentally infected with Neospora caninum at 110 days of gestation. Veterinary Parasitology. 169:304-311. Interpretive Summary: Neospora caninum is a single celled parasite. It causes abortion in cattle worldwide. Pathogenesos of N. caninum induced abortion is not fully understood. In the present study scientists report induction of abortion in cows experimentally inoculated with N. caninum.. The results will be of interest to biologists, parasitologists, and veterinarians.
Technical Abstract: Neospora caninum is a major cause of abortion in cattle, but the reasons why some animals abort and not others remain unclear. Most of the N. caninum experimental primary infections in cattle late in gestation, after 120 days of pregnancy, results in birth of full-term congenitally infected fetuses. In the present study, the distribution of parasites and pathogenesis of infection in both dams and fetuses after inoculation with N. caninum NC-Illinois cattle-derived strain tachyzoites at 110 days of gestation were analyzed at 3 weeks, 6 weeks and 9 weeks after infection (WAI) in eight Angus heifers. One dam from the group euthanized at 6 WAI had a dead fetus at necropsy. Extensive lesions were observed in the placenta and tachyzoites were detected in both the placenta and the fetus. The fetus was seropositive and had high IFN-' production in fetal fluids. Another fetus, still alive when euthanized at 3 WAI, had severe lesions and high IFN-' production and a similar fate could have been expected if the experimental period would have been longer. Lesions in the placenta of the remaining six dams that had live fetuses at necropsy were mild. In those dams, the fetal and maternal placentas had not separated and contained focal areas of placentitis at the materno-fetal junction. Transplacental infection took place on all fetuses based on detection of parasitic DNA in fetal tissues. The present study shows that experimental N. caninum infection of naïve dams late in pregnancy, after 110 days of pregnancy can lead to fetal death. The results suggest that the severity of placental lesions and the strong IFN-g response in some fetuses, possibly as part of the immune response trying to control the high parasitemia, might, in fact, be the cause of their death.