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Congenital Chagas’ disease: diagnostic and clinical aspects in an area without vectorial transmission, Bermejo, Bolivia

27 Mar 2008

Marcia Triunfol

Source: Acta Tropica (see original article)

Citation: Brutus L, Schneider D, Postigo J, Romero M, Santalla J, Chippaux JP (2008). Congenital Chagas disease: diagnostic and clinical aspects in an area without vectorial transmission, Bermejo, Bolivia. Acta Trop. Mar 27. [Article in Press]

Ten million people are estimated to be infected with Trypanossoma cruzi in Latin America countries, from Mexico to Argentina. In Bolivia, a country endemic for Chagas’ disease, around two-thirds of the population are infected. Now scientists are finding out that, besides the vector, Triatoma infestans, other factors are contributing to maintain disease transmission.

As new ways of controlling the life-cycle of the vector are developed, the transmission of Chagas’ disease other than by its vector has become an increasingly important issue. In the United States and some European countries, following migrations of infected populations from endemic countries, Chagas’ disease has become a major public health concern.

Researchers in Bolivia have now shown that a similar phenomenon also occurs in this country, where internal migrations of people from infected areas to previously Chagas-free areas are promoting disease transmission through congenital transmission and blood transfusion.

During December 2002 to January 2004, a survey was conducted in the southern city of Bermejo, located on the border with Argentina and with a population of 30,000. The city, which has no vectorial transmission of Chagas’ disease, has a significant seasonal migration of workers in the sugar-cane plantations. During the period, all women who went through labour at the Hospital Virgen de Chaguaya were asked to be tested for Chagas’ disease through a blood test.

Of the 508 women tested, 172 (33.9%) were seropositive for T. cruzi, an incidence much higher than that found in pregnant women in neighbouring Argentina (4.4- 5.7%). Of 115 pregnant women randomly chosen, 38 showed seroprevalence of Chagas’ disease but only 3.5% had circulating T. cruzi in the blood. Interestingly, the rate of pregnant women showing circulating T. cruzi increased to 10% at time of delivery. The authors believe that this is related to pregnancy-associated parasitaemia, rather than to re-infection previous to labour, since these women were in a vector-free area and the probability that they had travelled back and forth to the original endemic area is remote, due to their advanced pregnancy.

Of 153 newborns tested, only eight (5.2%) were positive for circulating T. cruzi, which translates into an incidence of congenital Chagas’ disease of 150 in 10,000 newborns. However, researchers believe that this number may be underestimated due to: (i) a low sensitivity of the kit used to detect T. cruzi, (ii) lack of parasitological diagnosis in 1-month newborns, followed by serological test nine months later, and (iii) the low number of samples.

Nevertheless, congenital transmission does represent an issue in non-endemic areas and women with higher parasitic load were shown to be at greater risk of transmitting the parasite to their babies. However, this study should be repeated using a large number of samples, more sensitive diagnostic kits and better testing regimes, to allow for a better understanding of the impact of congenital Chagas’ disease in non-endemic areas in Bolivia.

Note: This article is published in a journal which is not open access. To see the full article a subscription to Acta Tropica is therefore required. Readers in some developing countries readers who are based in institutions may be able to access it through the HINARI initiative.