Division of Disease Control and Health Protection

Toxoplasmosis

Background and Symptoms

Toxoplasma gondii is very wide-spread in nature, and infects virtually all mammalian species.¹ This obligate intracellular protozoan was first discovered in gondis, a small cricetine rodent, maintained at the Pasteur Institute of Tunis.² Toxoplasmoisis remained an obscure disease of laboratory rabbits and guinea pigs at the Pasteur institute in Paris until 1937, when it was identified as a cause of congenital meningoencephalitis in infants. The majority of Toxoplasma infections are asymptomatic and undiagnosed, although a clinically acute acquired infection is characterized by fever, headache, swollen lymph nodes, or pneumonia, and often resembles infectious mononucleosis.³ Pregnant patients with acute infection can transmit the disease to the fetus causing abortion, stillbirth or severe congenital abnormalities.

Serological surveys have shown that by the age of 50 the prevalence of infection can range from 30-40% in adult populations in some areas of the United States.⁴ Toxoplasmosis is usually transmitted to people in poorly cooked or raw meat, or by exposure to Toxoplasma oocysts in the feces of infected cats.⁵ Latent infections may become active in immunocompromised individuals and can cause neurologic or pulmonary disease.³

Toxoplasmosis in Florida

Toxoplasmosis was declared a reportable disease in Florida in 1964. During the next decade, six human cases were reported. The number of cases averaged 10 per year from 1974-93, however, 44 cases were reported in 1994 and 1995 (22 each year). An analysis of these cases showed that most were black (64%) and male (57%), with a median age of 36 (range 6 to 84 years). Cases occurred in 13 counties throughout the state, but 18 (41%) were reported by St. Lucie County. The vast majority of the St. Lucie County cases were black (89%), and evenly divided by sex, with a median age of 36 (range 23-72 years). The presumed source of infection or immune status of these cases was not recorded. The most recent five-year figures (2000-2005) show an average of 18 cases per year confirmed within the state of Florida.

While it has been assumed that most cases result from exposure to Toxoplasma oocysts from cats, serologic surveys have shown relatively high prevalence of T. gondii antibodies in horses (18%), armadillos (19%), raccoons (18%), black rats (13%) and opossums (11%).^6,7

References

1. Mahmoud, AAF, and Warren, KS, Algorithims in the diagnosis and management of exotic diseases: XX Toxoplasmosis. J. Inf. Dis. 1977;135: 493-96.

2. Frenkel, JK, Pursuing toxoplasma. J. Inf. Dis. 1970;122: 553-59.

3. Melvin, DM et al. Blood and tissue parasites. In Diagnostic Procedures for Bacterial, Mycotic and Parasitic Infections, Balows, A and Hausler, WJ, (eds) Am. Pub. Hlth. Assn. 6th edition, 1981; pp.1117-52.

4. Welch, PC et al. Serologic Diagnosis of Acute Lymphadenopathic Toxoplasmosis. J. Inf. Dis. 1980;142:256-64.

5. Stagno, S et al. An outbreak of toxoplasmosis linked to cats. Pediatrics, 1980;65: 706-12.

6. Riemann, HP, et al. A survey for antibodies to Toxoplasma gondii in horses. Am. J. Vet. Res. 1975;36: 1797-1800.

7. Burridge, MJ, et al. Serologic Survey for Toxoplasma gondii in wild animals in Florida. JAVMA, 1979;175: 964-67.