Trends in Parasitology
ReviewSpecial Issue: Zoonoses of people and pets in the USAToxoplasma gondii: epidemiology, feline clinical aspects, and prevention
Section snippets
Toxoplasmosis in cats and other animals
Toxoplasma gondii is a widespread zoonotic protozoan that infects most, if not all, species of birds and mammals. As the definitive hosts for this organism, felines are the only animals that pass oocysts in their feces (Table 1; Box 1), although intermediate hosts can harbor infective tissue cysts. Most feline infections occur post-natally through ingestion of infected tissue cysts or rarely oocysts, although congenital infections can occur [1]. Feline infections are typically subclinical;
Prevalence and risk factors for feline and human infection
The estimated seroprevalance for T. gondii in domestic cats (Felis catus), worldwide, is 30–40% [2]. There has been no national estimate of T. gondii prevalence in cats in the USA; however, local seroprevalences have varied from ∼16% to 80% [3]. Serologic testing of clinically ill cats with toxoplasmosis as a differential diagnosis resulted in an overall seroprevalence of 31.6% [4]. Regional prevalences varied in conformance with different climates; prevalence in the drier southwest (New
Diagnosis and treatment of infection in cats
Options for ante-mortem diagnosis in cats include fecal examination for oocysts (Figure 2) and serologic testing; definitive diagnosis of toxoplasmosis can be difficult to accomplish [18]. Most infected cats will shed oocysts only at a single point in their lifetime, generally for a period of one to two weeks, and it has been estimated that only ∼1% of cats at any given time are actively shedding (Table 2) [1]; this estimate was supported through the observation of T. gondii-like oocysts in a
Prevention of infection in cats and humans
In the absence of an effective vaccine in humans, prevention of zoonotic transmission might be the best way to approach the problem of toxoplasmosis, and must be done by limiting exposure to oocysts or tissue cysts. Recommendations for accomplishing this include practicing good hygiene (e.g. hand washing after soil contact, washing fruits and vegetables that are eaten raw), freezing meat at −12 °C for 24 hours [13] and/or cooking meat until an internal temperature of 66 °C is reached, and not
Future research
Toxoplasmosis is a potentially serious disease, but one that is largely preventable. Informed clinicians—both in the human and veterinary medical professions—can decrease disease transmission while recognizing and helping to maintain the relationships that many people have with their domestic cats. The increased understanding of T. gondii infection provides exciting new opportunities for research, both in the veterinary and human medical fields (Box 2). Because the ingestion of oocysts is an
Acknowledgements
This material developed out of a workshop held at the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia in 2008 with invited representatives from the Companion Animal Parasite Council (CAPC), the CDC, the American Association of Veterinary Parasitologists (AAVP), and others. Many people made this publication possible; Lora Ballweber assisted with the original drafts of this document and critical help was provided by Lonnie King and Mary Bartlett of the CDC, and Sonya
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