Introduction and objective: Toxoplasma gondii and Neospora caninum are two closely related cyst forming apicomplexean protozoa that infect a wide range of warm-blooded animals. N. caninum has similar morphologic and biologic characteristics to T. gondii and until 1988 was misdiagnosed as T. gondii. Tachyzoites and tissue cysts of both parasites are found intracellularly in the intermediate hosts. The aim of this study was to determine the seroprevalence rate of anti-Neospora caninum and anti-Toxoplasma gondii antibodies in feral cats (Felis catus) in Ahvaz, Iran.

Materials and methods: Antibodies to N. caninum and T. gondii were determined in serum samples of 100 feral cats in Ahvaz, Khuzestan province, Iran. IgG antibodies were assayed by the modified agglutination test using whole tachyzoites of T. gondii and N. caninum, incorporating 2-mercaptoethanol, modified agglutination test and Neospora agglutination test, for T. gondii and N. caninum, respectively.

Results: Anti-T. gondii antibodies were found in 54 (54%) of 100 cats but anti-N. caninum antibodies were detected in 19 (19%) of 100 cats. There was no difference between the presence of antibodies for both parasites in male and female cats (P