References
Toxoplasma gondii – the facts
Abstract
The protozoan parasite Toxoplasma gondii was initially isolated from the rodent Ctenodactylus gundi, and it has been found worldwide from Alaska to Australia with nearly one third of the human population having been exposed to this parasite. All warm-blooded hosts, including humans, can be infected by any one of its three infective stages: tachyzoites, bradyzoites, and sporozoites. Felids are the definitive hosts of this intracellular pathogen. Although it usually causes mild disease or asymptomatic infection in immunocompetent adults, this parasite can cause devastating disease in congenitally infected children and those with depressed immunity. Because of its zoonotic potential, toxoplasmosis triggers the interest of the diverse medical and veterinary specialities. Consciousness needs to be increased that this disease can produce clinical cases not only in immunocompromised patients or through vertical transmission, but also in healthy patients. In this article, we will review the biology and the epidemiology of this parasite.
Toxoplasma gondii is a single-celled coccidian parasite. Coccidia in general have very complicated life cycles, with most of them being host-specific and transmitted via the faeco-oral route. Toxoplasma gondii is one of the most important parasites of animals, with felids as the definitive hosts and warm-blooded animals as intermediate hosts (Figure 1). It has three infectious stages: tachyzoites (in groups), bradyzoites (in tissue cysts) and sporozoites (in oocysts). It can also be transmitted through the consumption of infected meat and vegetables, as well as vertically (Frenkel et al, 1970; Dubey, 2010).
Toxoplasma is an obligate intracellular parasite, infecting most nucleated cells of warm-blooded animals. This parasite (toxon=arc, plasma=form) derives its name from the crescent shape of the tachyzoite stage (Figure 2a), (the approximate size of an erythrocyte, 2 x 6 μm), and gundi from Ctenodactylus gundi, the North African rodent from which this parasite was first isolated in 1908 by Nicolle and Manceaux (Dubey, 2008).
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