Toxoplasmosis

Excerpt

Toxoplasmosis is a zoonotic infection caused by Toxoplasma gondii, an obligate intracellular parasitic protozoan. T gondii can infect all warm-blooded vertebrates, including humans. Domestic and wild felids are the definitive hosts, shedding unsporulated oocysts with their feces into the environment. Transmission of infection often occurs through ingesting tissue cysts via improperly cooked or raw meat or contaminated food or water. Other routes of transmission include vertical transmission, causing miscarriage or congenital toxoplasmosis, and via transplantation, by T gondii from either the host or donor organ.

Although T gondii is present worldwide, it rarely causes clinically significant disease in immunocompetent people; those with primary infections are usually asymptomatic and may have subclinical infections. Those who are immunocompetent can, however, develop acute toxoplasmosis that can manifest with nonspecific, constitutional symptoms, such as fever, malaise, and lymphadenopathy, as well as central nervous system pathology and ocular disease, usually posterior uveitis. The parasite is considered neurotropic and oculotropic. After the initial infection, T gondii enters latency and persists for the host's life. T gondii latent tissue cysts can reactivate in profoundly immunosuppressed people, including patients receiving chemotherapy, organ transplants, or those with human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS), causing severe disseminated infection. Reactivation can also occur during transplantation from reactivation from the host, from the donor organ, or primary infection.

T gondii is a ubiquitous parasite that can cause severe disease in humans and even be fatal in patients with fulminant disease. Clinicians aren't highly aware of the presence of toxoplasmosis and its clinical presentation, especially in patients who are immunocompetent and have few symptoms. Thus, the disease burden is underestimated. A high index of suspicion is necessary, and appropriate evaluation, timely diagnosis, and treatment of patients with toxoplasmosis are essential.