Archive Number 20050327.0884 Published Date 27-MAR-2005 Subject PRO> Trypanosomiasis, foodborne - South America (03)
TRYPANOSOMIASIS, FOODBORNE - SOUTH AMERICA (03) *********************************************** A ProMED-mail post http://www.promedmail.org ProMED-mail is a program of the International Society for Infectious Diseases http://www.isid.org
Date: Sun 27 Mar 2005 From: Luiz Jacintho da Silva luiz_jacintho@uol.com.br Source: Fiocruz.br [translated from Portuguese by Mod.LJS, edited] http://www.fiocruz.br/ccs/novidades/dez04/chagas_fer.htm
Study confirms a different form of Chagas? disease transmission ----------------------------------------------- When one hears of the transmission of the protozoan _Trypanosoma cruzi_, the 1st thing that comes to the mind is the Reduviid bug vector. This insect, when biting an individual, eliminates parasite-contaminated feces that, as the individual scratches himself, penetrates through abraded skin or mucosa [intact]. This is the most common route, but the occurrence of certain outbreaks has led scientists to consider the possibility of oral transmission of _T.cruzi_.
A study by the Goncalo Muniz Research Center, a FIOCRUZ unit in Bahia, presents evidence that this protozoan can indeed be transmitted by the ingestion of contaminated food [or beverages]. On Sun 20 Mar 2005, an episode in Santa Catarina confirmed the results of the research.
The deaths of 3 [now 5] persons, and the report of another 15 cases of the disease in the state, have led health authorities in the state to prohibit the sale of sugarcane juice. The infection seems to have been transmitted by this beverage.
In 1968, a member of a farming community in Teotonia (Rio Grande do Sul) fell ill with a severe febrile illness. No one suspected Chagas disease, as there were no Reduviid bug vectors in the local dwellings. After much investigation, food borne transmission through vegetables served in the common dining-room was accepted as the cause. Possibly, marsupials had contaminated the vegetables by droppings from their anal glands, usually rich in _T.cruzi_.
Years later [1986], another outbreak occurred, this time in Catole do Rocha (Paraiba). A large wedding anniversary party had been held on a farm. Days later, some of the guests fell ill with a febrile illness, similar to the one in Teotonia. Sugarcane juice and other foodstuffs or beverages had been contaminated by animal droppings. The couple that had celebrated their 50th anniversary eventually died as a consequence of Chagas disease acquired at the party.
Recently, oral transmission of _T. cruzi_ has been responsible for small outbreaks in the state of Para. Entire families acquired Chagas disease in the absence of insect vectors in their homes. These insects live in palm trees and, attracted by the lights, fall into the machinery used to grind acai to obtain juice (much the way sugarcane juice is obtained). The insects are ground and contaminate the juice with _T. cruzi_, transmitting the infection to those drinking it.
All of these cases in Rio Grande do Sul, Paraiba and Para attracted the attention of scientists. The question which was brought forward was why didn't gastric juice destroy _T. cruzi_? The physician Sonia Gomes Andrade from CPqGM, who specializes in experimental pathology, formulated an experiment:
- We introduced _T. cruzi_ through a tube directly into the stomach of mice, she says. She studied the strains isolated from cases in Paraiba and Para. - We observed that the parasite not only survived gastric juice but was able to infect the mice. They developed disease identical to the one produced when mice are infected directly via the bloodstream. The findings of the researcher confirm that _T. cruzi_, when swallowed, can cause infection through the digestive system. - In the most common manner of infection, scratching, _T. cruzi_ is able to penetrate the skin. [It is easy to] imagine [that], when someone ingests a large quantity of parasites, the [infection] will be more severe, says Sonia. The researcher stated that there is no reason to stop eating vegetables or drinking sugarcane or acai juice. - The problem lies not with the kind of food but with _T. cruzi_. These are mainly parasites of biodem type III -- from wildlife -- that are able to cause infection through the digestive system. A biodem is a group of [genetically close] _T.cruzi_ strains with similar characteristics. Biodem type III strains are, as a rule, highly pathogenic. In the experiment, a strain of this type showed a higher capacity to cross the gastric barrier and cause infection in mice than strains from biodems I and II. - It is significant to point out that biodem III strains are associated with wildlife disease cycles, causing outbreaks in places where Reduviid bugs are not domiciled.
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[It seems beyond doubt that _T. cruzi_ can infect hosts, including humans, by the oral route, but it still remains unclear how important this route of transmission is for maintaining infections in humans and causing outbreaks like the present one. The mouse experiment cited above confirms previous reports [cited in ProMED-mail, Trypanosomiasis, foodborne - South America 20050324.0847; Hoft et al. Infect Immun 1996,64:3800-10] that _T. cruzi_ can indeed infect the host through the gastric mucosa. The key question is how long a time _T. cruzi_ can survive in feces outside the triatomid bug, and how long a time in different forms of fluids after the triatomid bugs have been crushed. Oral transmission, either from bug feces or from crushed bugs, presumes that _T. cruzi_ can survive for at least several hours, possibly days, in juice. Information on this survival time is key to determining whether the present outbreak is a rare coincidence or just part of a more widespread problem. - Mod.EP]
[see also: Trypanosomiasis, foodborne - South America (02) 20050325.0870 Trypanosomiasis, foodborne - South America 20050324.0847 1998 ---- Trypanosomiasis - Brazil: RFI 19980306.0426 1997 ---- Chagas disease - Latin America 19970114.0066 Chagas disease vector (05) 19970118.0105 1996 ---- Trypanosomes, New World, Symposium - Guyana 1996 19960830.1493] ...............ep/msp/lm
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