BARCELONA/SPAIN, May 10th (Biermann) – Neospora caninum is a major cause of abortion in cattle, Dr. S. Almeria and colleagues note. However, they add, the reasons why some animals abort and not others remain unclear. Based on the fact that most Neospora caninum experimental primary infections in cattle late in gestation (after 120 days) result in birth of full-term congenitally infected fetuses, the team from Universitat Autònoma de Barcelona conducted a small study in 8 Angus heifers.

They analyzed the distribution of parasites and pathogenesis of infection in both dams and fetuses after inoculation with 107 culture derived tachyzoites of Neospora caninum (NC-Illinois cattle strain) at 110 days of gestation. Analysis took place at 3, 6 and 9 weeks after infection.

Almeria and colleagues report that 1 dam from the group euthanized at 6 weeks after infection had a dead fetus at necropsy. The researchers found extensive lesions in the placenta and tachyzoites were detected in both the placenta and the fetus. The fetus was seropositive and had high IFN-γ production in fetal fluids.

As appears from the article in Veterinary Parasitology, another fetus, still alive when euthanized at 3 weeks after infection, had severe lesions and high IFN-γ production. The authors say that “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 researchers write, 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 team adds.

They conclude that “experimental Neospora caninum infection of naïve dams after 110 days of pregnancy can lead to fetal death.” Furthermore, they say, the results suggest that the severity of placental lesions and the strong IFN- γ 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.

References

• Veterinary Parasitology, Volume 169, Issues 3-4, 11 May 2010, Pages 304-311