Oral and Organ Transmission

Some less‑frequent forms of transmission are by direct ingestion, organ transplant, and skin contact with infected material (Bittencourt 1975; Katz, Despommier, and Gwadz 1989; Schofield, Apt, and Miles 1982). Oral transmission to humans is not well documented, although it is easy to infect animals by this route (Marsden 1967).[23]Because vinchucas defecate in domiciliary and peridomiciliary areas, the possibility of contamination through contact with the insect’s feces and subsequent ingestion of the parasite exists but is not likely.

Three microepidemics in Brazil are attributed to oral transmission (NeryGuimaraes et al. 1968). Schoolchildren became infected with T. cruzi from drinking contaminated milk in Estrella, Rio Grande do Sul, Brazil, an area where triatomines were not found (Calvo et al. 1978:80). The milk had been transported from an endemic area.

In an agricultural school in Rio Grande do Sul, seventeen people were infected and six died from T. cruzi transmitted through food contaminated with opossum urine infected with T. cruzi. The initial misdiagnosis of the illness and the patients’ treatment with steroids aggravated the infection (Di Primio 1971). Trypanosomes can be found in the saliva and urine of animals suffering from acute parasitemia. This constitutes an infective risk for humans working with these animals (Marsden and Hagstrom 1968).

A third instance was in Belem, Para, Brazil, at the mouth of the Amazon, where human Chagas’ disease is rare (Lainson et al. 1979) because only sylvatic species of bugs in this area are known to be infected. It is possible that an infected bug entered the house and fell in a cold soup customarily prepared (Lainson et al. 1980) and infected it with T. cruzi. Because contamination is the major route of transmission, many other possibilities exist for humans coming in contact with T. cruzi through vinchuca feces falling from the ceiling, getting into clothing, and being deposited on tools, among other things. As already mentioned, the periodic washing of the body and clothes is important in combatting the disease, as are good house hygienic practices.

Animals can transmit T. cruzi to humans by licking their skin, and nursing mothers can pass it on to their babies in lactation, possibly through the milk but more likely through sores or inflammations on the breast (Carrasco and Antezana 1991). The parasite’s presence in maternal milk has been confirmed by Medina (1983), but the incidence of transmission by this route has not been reported, probably due to the problem of differentiating it from congenital transmission (Moya 1994).

Transmission by breast‑feeding appears to be highly unlikely, and infected mothers need not restrict breast‑feeding their infants (WHO 1991:33). This conclusion was based on a systematic parasitological study of 100 milk, or colostrum, samples from seventy‑eight mothers with chronic Chagas’ disease in Bahia, Brazil. Even though five mothers had detectable parasitemia, all samples were negative (Bittencourt et al. 1988). In another study in Córdoba, Argentina, and Santa Cruz, Bolivia, ninety‑seven children (100 percent of the sample) born free of the infection from infected mothers and subsequently breast‑fed tested serologically negative (WHO 1991:33).

Organ transplants from infected donors is an increasing route of T. cruzi transmission for recipients in the United States and Europe. There is an increasing number of organs being sold through the “black market” to patients in the United States from Latin American countries. Americans also travel to clinics in Latin America for organ transplants. Kidney transplants have been shown to be a source of T. cruzi infection, and organ recipients have developed acute episodes of Chagas’ disease (Chocair et al. 1981). In certain transplants, fatality has been attributed to donated organs infected with T. cruzi, because recipients are under immunosuppressive therapy (WHO 1991:34). Conversely, Chagas’ disease patients who receive organ transplants can suffer exacerbation of the infection when given immunosuppressive treatment (Leiguarda et al. 1990).

Laboratories treat T. cruzi with respect. It is the most infectious of the human blood protozoa. By 1976 more than fifty lab technicians had been infected with Chagas’ disease; they suffered meningoencephalitis and megasyndromes (Marsden 1976). Since this time, technicians have learned how to better handle high‑risk organisms, but certain research hospitals still refuse to do research on T. cruzi because of its risk factor. Laboratory infections are usually due to punctures with infected needles, contact with contaminated materials, breathing T. cruzi cultures while pipetting, and splashing T. cruzi suspensions on the conjunctivae. Measures for prevention and control are outlined in WHO (1991).

Laboratories in Bolivia present great risks for contracting Chagas’ disease because of their often rudimentary facilities, inadequately trained staff, and insufficient funds to provide protective measures. The exception is the Instituto Boliviano de Biologia de Altura (IBBA), located in La Paz and affiliated with the Pasteur Institute in Paris. Eminent French and Bolivian scientists direct this research laboratory and have done leading work on parasitology. Other, much less developed, laboratories are under control of the Secretaria Nacional de Salud and are funded with minimal budgets. Nonetheless, technicians make do. One technician observed that he was not worried about Chagas’ disease, being already infectedwhich perhaps is the case for many Bolivian researchers.