Neospora caninumInfection and Repeated Abortions in Humans

DispatchesNeospora caninum, an intracellular protozoan parasite closely related to Toxoplasma gondii (1,2), was first described in dogs in Norway in 1984 and later in a wide range of other mammals including cattle, goats, horses, and sheep.The life cycle of N. caninum is only partially known, but the dog has recently been established as its definitive host (3).The pathogens only known natural route of transmission (which can occur during sequential pregnancies in cattle) is transplacental (4).N. caninum is now recognized as the most common cause of repeated abortions and stillbirths in cattle, and infected herds have been reported in most parts of the world, including Scandinavia (4-6).Infected, live-borne offspring may have neurologic symptoms including progressive paralysis.When experimentally transferred to pregnant nonhuman primates, N. caninum has caused fetal infection.The fetal lesions closely resembled those in congenital toxoplasmosis (7).N. caninum organisms are morphologically very similar to T. gondii, the pathogen responsible for toxoplasmosis; however, the two species have distinct antigenic characteristics and can be distinguished by serologic and immunohistochemical methods (4).No case of N. caninum infection has been described in humans.However, because of the organisms close phylogenetic relationship to T. gondii and its wide range of potential hosts, the possibility of human N. caninum infection cannot be excluded.We investigated serologically the possible presence of N. caninum infection in Danish women who had repeated abortions of unknown cause. The StudyThe study included 76 women (mean age 30.8 years, range 19 to 41 years) who had had repeated abortions or intrauterine death of the fetus.Blood samples were obtained at the time of abortion or within 3 months of fetal death.The study participants had been referred to the Department of Gynecology and Obstetrics, Rigshospitalet, Copenhagen, Denmark, between 1 September 1991 and 31 October 1992 as part of a larger study of pregnant women with repeated primary or secondary abortions or repeated intrauterine fetal deaths.Serum specimens were tested for antibodies to N. caninum and T. gondii as described below.