A brief history and overview of Toxoplasma gondii.

Toxoplasma gondii was discovered by scientists working in North Africa and Brazil around 100 years ago. The parasite has since been found to be capable of infecting all warm-blooded animals including humans making it one of the most successful parasitic organisms worldwide. The pathogenic potential of T. gondii was recognized in the 1920s and 1930s, in congenitally infected children presenting with the classic triad of symptoms, namely hydrocephalus, retinochoroiditis and encephalitis. In addition, around the same time T. gondii parasites were found to be associated with severe intraocular inflammation. In the 1980s, T. gondii emerged as a major cause of death in patients with acquired immunodeficiency syndrome, illustrating the importance of the immune system in controlling T. gondii infection. T. gondii was reported as a major cause of abortion in sheep in New Zealand in the 1950s, which raised questions about potential new transmission routes for the parasite. The discovery of the cat as the definitive host in the 1960s was a very important finding as it helped to complete our understanding of the parasite's life cycle, and the oocyst stage of T. gondii shed in the faeces of infected cats was found to be an important source of infection for many intermediate hosts and helped to explain infection in herbivorous animals and people with a vegetarian diet. In addition, this stage of the parasite was very robust and could survive in the environment, depending on the climatic conditions, for up to 12-18 months. Knowledge of the parasite's life cycle, transmission routes, risk groups and host immune responses has helped in the development of strategies to control the disease, reduce transmission of the parasite and limit environmental contamination.

History of the discovery of the life cycle of Toxoplasma gondii.

It has been 100 years since the discovery of Toxoplasma gondii in 1908. Its full life cycle was not discovered until 1970 when it was found that it is a coccidian parasite of cats with all non-feline warm blooded animals (including humans) as intermediate hosts. The discovery of the environmentally resistant stage of the parasite, the oocyst, made it possible to explain its worldwide prevalence. In the present paper, events associated with the discovery of its life cycle are recalled.

Identification of faecal transmission of Toxoplasma gondii: Small science, large characters.

The first clue to the elucidation of the complete life cycle of Toxoplasma gondii was the identification of an infectious form in cat faeces that could be transmitted orally and could survive in the external environment for extended periods. This personal review describes the scientist (W.M. Hutchison) and the background to the initial discovery and covers the period to the complete elucidation of the life cycle of T. gondii.

The history of Toxoplasma gondii--the first 100 years.

In this paper the history of Toxoplasma gondii and toxoplasmosis is reviewed. This protozoan parasite was first discovered in 1908 and named a year later. Its medical importance remained unknown until 1939 when T. gondii was identified in tissues of a congenitally infected infant, and veterinary importance became known when it was found to cause abortion storms in sheep in 1957. The discovery of a T. gondii specific antibody test, Sabin-Feldman dye test in 1948 led to the recognition that T. gondii is a common parasite of warm-blooded hosts with a worldwide distribution. Its life cycle was not discovered until 1970 when it was found that felids are its definitive host and an environmentally resistant stage (oocyst) is excreted in feces of infected cats. The recent discovery of its common infection in certain marine wildlife (sea otters) indicates contamination of our seas with T. gondii oocysts washed from land. Hygiene remains the best preventive measure because currently there is no vaccine to prevent toxoplasmosis in humans.

[Toxoplasmosis: historical summary and bibliographic review]. / Toxoplasmosis: resumen histórico y revisión bibliográfica.

A chronologic description of the principal events and discoveries related to toxoplasmosis from 1908 when the causal agent was discovered up to date is performed. The main data with a parasitic interest are summarized, and the endodiogenic multiplication is explained. The cat is the definitive host for this protozoan. Its evolutive cycle in the intestinal epithelium of this domestic animal is commented. The oocyst is recognized as the main infecting form of this microorganism. The classical concepts of congenital and acquired histoplasmosis are briefly exposed. A brief comment of the ophthalmic and gyneco-obstetric complications from the disease is made. Possible relationships between toxoplasmic adenopathies and neurotic states in psychiatry are emphasized.