Article

Toxoplasma gondii: From animals to humans

Institut für Parasitologie, Tierärztliche Hochschule Hannover, Bünteweg 17, D-30559, Hannover, Germany.
International Journal for Parasitology (Impact Factor: 3.87). 11/2000; 30(12-13):1217-58. DOI: 10.1016/S0020-7519(00)00124-7
Source: PubMed

ABSTRACT

Toxoplasmosis is one of the more common parasitic zoonoses world-wide. Its causative agent, Toxoplasma gondii, is a facultatively heteroxenous, polyxenous protozoon that has developed several potential routes of transmission within and between different host species. If first contracted during pregnancy, T. gondii may be transmitted vertically by tachyzoites that are passed to the foetus via the placenta. Horizontal transmission of T. gondii may involve three life-cycle stages, i.e. ingesting infectious oocysts from the environment or ingesting tissue cysts or tachyzoites which are contained in meat or primary offal (viscera) of many different animals. Transmission may also occur via tachyzoites contained in blood products, tissue transplants, or unpasteurised milk. However, it is not known which of these routes is more important epidemiologically. In the past, the consumption of raw or undercooked meat, in particular of pigs and sheep, has been regarded as a major route of transmission to humans. However, recent studies showed that the prevalence of T. gondii in meat-producing animals decreased considerably over the past 20 years in areas with intensive farm management. For example, in several countries of the European Union prevalences of T. gondii in fattening pigs are now <1%. Considering these data it is unlikely that pork is still a major source of infection for humans in these countries. However, it is likely that the major routes of transmission are different in human populations with differences in culture and eating habits. In the Americas, recent outbreaks of acute toxoplasmosis in humans have been associated with oocyst contamination of the environment. Therefore, future epidemiological studies on T. gondii infections should consider the role of oocysts as potential sources of infection for humans, and methods to monitor these are currently being developed. This review presents recent epidemiological data on T. gondii, hypotheses on the major routes of transmission to humans in different populations, and preventive measures that may reduce the risk of contracting a primary infection during pregnancy.

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Available from: ncbi.nlm.nih.gov
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    • "Additionally, T. gondii infection causes economic losses due to the abortion and neonatal loss in livestock, especially in sheep and goats. Even worse than this is the fact that human can be infected by ingesting undercooked or raw meat containing tissue cysts, or by ingesting food or water contaminated with oocysts345. At present, prevention and treatment of toxoplasmosis mainly depends on chemotherapeutics that acting on the acute phase of the infection. "

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    • "Toxoplasmosis caused by Toxoplasma gondii is a severe public problem with a 53 world-wide distribution (Tenter et al., 2001; Montoya and Liesenfeld, 2004). Nearly one third 54 of the human population has been infected by T. gondii in the world, and about 7.9% in China 55 was exposed to T. gondii with a sustained growing in the recent years (Dubey, 2010; Zhou et 56 al., 2011). "
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    • "Toxoplasma gondii is an obligate, intracellular, parasitic protozoan that causes the disease toxoplasmosis (Hill & Dubey 2002). Found worldwide, T. gondii is capable of infecting virtually all warmblooded animals(Tenter et al. 2000), although felids such as domestic cats are the only known definitive hosts in which the parasite can undergo sexual reproduction(Elmore et al. 2010). serological studies estimate that 30–50% of the global population has been exposed to and may be chronically infected with T. gondii, although infection rates differ significantly from country to country(Flegr et al. 2014). "
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