Toxoplasma gondii: epidemiology, feline clinical aspects, and prevention

doi:10.1016/j.pt.2010.01.009

Trends in Parasitology

Volume 26, Issue 4, April 2010, Pages 190-196

https://doi.org/10.1016/j.pt.2010.01.009 Get rights and content

Toxoplasma gondii is a parasite of birds and mammals. Cats are the only definitive host and thus the only source of infective oocysts, but other mammals and birds can develop tissue cysts. Although feline infections are typically asymptomatic, infection during human pregnancy can cause severe disease in the fetus. Cat owners can reduce their pets’ exposure risk by keeping all cats indoors and not feeding them raw meat. Humans usually become infected through ingestion of oocyst-contaminated soil and water, tissue cysts in undercooked meat, or congenitally. Because of their fastidious nature, the passing of non-infective oocysts, and the short duration of oocyst shedding, direct contact with cats is not thought to be a primary risk for human infection.

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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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

Prevalence and risk factors for feline and human infection

Diagnosis and treatment of infection in cats

Prevention of infection in cats and humans

Future research

Acknowledgements

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Zoonoses and Public Health.

Experimental reinfection of BALB/c mice with different recombinant type I/III strains of Toxoplasma gondii: involvement of IFN-γ and IL-10

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Risk factors for Toxoplasma gondii infection in wild rodents from central coastal California and a review of T. gondii prevalence in rodents

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Seroprevalences of antibodies against Bartonella henselae and Toxoplasma gondii and fecal shedding of Cryptosporidium spp, Giardia spp, and Toxocara cati in feral and pet domestic cats

JAVMA

Toxoplasma gondii infection in the United States, 1999-2004, decline from the prior decade

Am. J. Trop. Med. Hyg.

Risk Factors for Toxoplasma gondii infection in the United States

Clin. Infect. Dis.

Risk factors for toxoplasmosis in pregnant women in Kent, United Kingdom

Epidemiol. Infect.

Risk factors for Toxoplasma gondii in pregnancy: results of a prospective case-control study in Norway

Am. J. Epidemiol.

Antemortem diagnosis and treatment of toxoplasmosis in two cats on cyclosporin therapy

Aust. Vet. J.

Detection of Toxoplasma gondii-like oocysts in cat feces and estimates of the environmental oocyst burden

JAVMA

Efficacy of ponazuril in vitro and in preventing and treating Toxoplasma gondii infections in mice

J. Parasitol.

Prevention of recrudescent toxoplasmic encephalitis using ponazuril in an immunodeficient mouse model

J. Euk. Microbiol.

Veterinary vaccines against Toxoplasma gondii

Memorias Inst Oswaldo Cruz.

A field trial of the effectiveness of a feline Toxoplasma gondii vaccine in reducing T. gondii exposure for swine

J. Parasitol.

The Toxoplasma gondii oocyst from cat feces

J. Exp. Med.

Population structure of Toxoplasma gondii: clonal expansion driven by infrequent recombination and selective sweeps

Annu. Rev. Microbiol.

Review
Special Issue: Zoonoses of people and pets in the USA
Toxoplasma gondii: epidemiology, feline clinical aspects, and prevention