Neosporosis

Neospora caninum is an apicomplexan parasite first associated with bovine abortion in the USA in 1989 ( Bjerkas et al., 1984; Thilsted and Dubey 1989) . Since this observation N. caninum has been implicated as one major cause of infectious abortion of cattle worldwide.

Abortion due to neosporosis can occur at any stage of pregnancy but is most likely to occur between 5–7 months of gestation (Dubey et al., 1996). Cows that aborted in a previous pregnancy due to neosporosis can abort again. They can also give birth to diseased calves, calves with a sub-clinical N. caninum infection, or uninfected calves.

Neospora caninum is a cyst-forming coccidian parasite. Two asexual stages (tachyzoite and bradyzoite) of development occurs in the intermediate host (cattle, horse) and one sexual stage (oocyst) occurs in the definitive host (dog) (McAllister et al 1998).

Routine diagnosis of N. caninum infection is made by observation of clinical signs (abortion, peaking between the fifth and seventh month of gestation) , by histology of fœtal tissue and by indirect fluorescent antibody (IFAT), and ELISA tests on maternal and foetal blood. But abortion is not always related to the presence of antibody.

In 1996, a shift of biologists of Berne Institute of Parasitology conducted by the Professor Kaufmann identified a repetitive genomic fragment called Nc5, specific of N. caninum (Kaufmann et al., 1996). Since, the sequence has been used as probe in molecular test as PCR test ( Muller et al., 1996 ; Yamage et al., 1996).

The PCR test allows the specific and sensitive detection of the parasite from fœtal tissues.