Toxoplasmosis is caused by Toxoplasma gondii, a protozoan parasite that infects humans and other warmblooded animals. It is found worldwide.

Felines (members of the cat family) are the only definitive hosts of the parasite. Both wild and domestic cats serve as the main reservoir of infection (see Disorders Affecting Multiple Body Systems of Cats: Toxoplasmosis in Cats). In dogs, a generalized infection may occur as the parasites travel through the body and invade the tissues.

Adult animals with vigorous immune systems control the spread of the parasite efficiently; therefore, toxoplasmosis usually causes no signs in healthy dogs. However, in puppies, the parasites may spread throughout the body. Signs of infection include fever, diarrhea, cough, difficulty breathing, jaundice, seizures, and death. Adult animals with weakened immune systems are extremely susceptible to developing sudden, generalized toxoplasmosis.

In many cases, treatment is not necessary. If warranted, your veterinarian will prescribe antibiotics to treat toxoplasmosis. Anticonvulsant medications may be used to control seizures. Fluids or other medication given by intravenous injection may be necessary for animals that are dehydrated or severely debilitated due to the infection.

Last full review/revision July 2011 by Otto M. Radostits, CM, DVM, MSc, DACVIM (Deceased); David A. Ashford, DVM, MPH, DS; Craig E. Greene, DVM, MS; Eugene D. Janzen, DVM, MVS; Bert E. Stromberg, PhD; Max J. Appel, DMV, PhD; Stephen C. Barr, BVSc, MVS, PhD, DACVIM; J. P. Dubey, MVSc, PhD; Paul Ettestad, DVM, MS; Kenneth R. Harkin, DVM, DACVIM; Delores E. Hill, PhD; Johnny D. Hoskins, DVM, PhD; Jodie Low Choy, BVMS; Barton W. Rohrbach, VMD, MPH, DACVPM; J. Glenn Songer, PhD; Joseph Taboada, DVM, DACVIM; Charles O. Thoen, DVM, PhD; John F. Timoney, MVB, PhD, Dsc, MRCVS; Ian Tizard, BVMS, PhD, DACVM