Toxoplasmosis and neosporosis are closely related protozoan diseases that lead to important
economic impacts in farm ruminants. Toxoplasma gondii infection mainly causes reproductive failure in
small ruminants and is a widespread zoonosis, whereas Neospora caninum infection is one of the most
important causes of abortion in cattle worldwide. Vaccination has been considered the most economic
measure for controlling these diseases. However, despite vaccine development efforts, only a liveattenuated
T. gondii vaccine has been licensed for veterinary use, and no promising vaccines against
neosporosis have been developed; therefore, vaccine development remains a key goal. Additionally,
drug therapy could be a valuable strategy for disease control in farm ruminants, as several drugs that
limit T. gondii and N. caninum proliferation and dissemination have been evaluated. This approach may
also be relevant to performing an initial drug screening for potential human therapy for zoonotic parasites.
Treatments can be applied against infections in adult ruminants to minimize the outcomes of a
primo-infection or the reactivation of a chronic infection during gestation or in newborn ruminants to
avoid infection chronification. In this review, the current status of drug development against toxoplasmosis
and neosporosis in farm ruminants is presented, and in an effort to promote additional treatment
options, prospective drugs that have shown efficacy in vitro and in laboratory animal models of
toxoplasmosis and neosporosis are examined.
Neospora caninum Infection in a Litter of Labrador Retriever Dogs in Denmark