Toxoplasmosis is a foodborne disease that is estimated to have infected one third of the human population (2). Not only does Toxoplasmosis infect humans, but it is also been found in almost all of the warm-blooded animals, primarily cats (3). Toxoplasmosis was first found in 1908 by Nicolle and Manceaux in the cells of the gundi, a type of rodent, in Brazil. It was also found by Splendore to be in the tissues of a rabbit. Fifteen years later, in 1923, a fatal case of toxoplasmosis was reported in a child. Finally in 1939, toxoplasmosis was identified as a cause of human disease (2).
Toxoplasmosis seemed to first be described by Toxoplasmosis is caused by a parasite called Toxoplasma gondii. Toxoplasma gondii has two types of hosts, a definitive and an intermediate. Cats are the only definitive hosts for Toxoplasma gondii meaning that only when the parasite infects the cat will it produce oocysts (eggs). Toxoplasma gondii will not produce eggs in other warm-blooded animals. When the cat digests food that contains this parasite, the Toxoplasma gondii inside of the cat will be released into the digestive tract where it will then multiply and produce oocysts in the small intestine. This process is called intraintestinal infection cycle.
The parasite is released in large quantities through the feces. The cat will also start shedding oocysts after 3 days of being infected and will continue to shed for 10 to 14 days. T he oocysts are very resilient and can survive up to a year. Other oocysts in the cat penetrate deeper into the intestine and develop tachyzoite which is the parasite’s form of rapid growth. The tachyzoite spreads throughout the body and start the extraintestinal infection cycle. When the immune system responds, the tachyzoite go into their resting stage and become bradyzoites, which is a slow growing form (3). A human or any other intermediate host can then be exposed to the parasite through either eating meat contaminated with the parasite or accidently (or not) swallowing cat feces (1).
The oocysts are not immediately infectious as they must first go through a process called sporulation which takes from one to five days. Once the sporulated oocysts are in the intermediate host, they develop tissue cysts which stay in the host for life (3). When Toxoplasma gondii enters the human host, tachyzoites begin to develop and infect various organs.
The parasite then enters the brain and creates oocysts. It then establishes a “chronic infection” which taxes the immune system (4). Toxoplasmosis usually doesn’t show any for most people. Severe cases of toxoplasmosis usually develop in babies whose mother was infected by toxoplasmosis or by people with compromised immune systems such as people with HIV. Some people with mild cases of toxoplasmosis may exhibit flu-like symptoms with swollen nymph glands along with sore muscles for a month or more. However, the severe cases can cause individuals to develop encephalitis along with eye and other organ damage. Patients may begin to experience pain that is accompanied by a bright light along with reduced vision and redness of the eye (1).
2 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2704023/?tool=pubmed 3 http://www.vet.cornell.edu/fhc/brochures/toxo.html
6 http://www.biology.ed.ac.uk/research/groups/jdeacon/microbes/penicill.htm 7 http://bioweb.uwlax.edu/bio203/s2008/kitzmann_step/
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Topic: A foodborne disease that is estimated to have infected one third of the human population
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