Control of congenital transmission of Trypanosoma cruzi in Argentina

The vertical transmission of Trypanosoma cruzi has been augmenting its rela tive importance as vector and transfusion-mediated transmission routes have been, and continue to be, increasingly controlled. The vertical transmissi on of T. cruzi cannot be prevented, but early detection and treatment of co ngenital infection achieve cure rates close to 100%. In Argentina, the Subp rogram of Control of Pregnant Women examined 58 196 women from 13 provinces in 1997 and found a 9% seropositivity to T. cruzi In spite of such high ma ternal prevalence rates of T. cruzi, only a small proportion of live newbor ns to infected mothers acquires the infection. The probability of vertical transmission was 1.9% (range: 0.1% to 3.5%) in surveys carried out in the ' 70s, and 2.5% (range: 0.7% to 10.4%) in others conducted in the '70-'80s. O ther more recent studies in Argentina estimated the probability of transmis sion in 2.6%-6.7%, but studies from Paraguay estimated 10.5% by PCR or sero diagnosis. The microhematocrit technique is the recommended parasitologic m ethod to detect congenital infection. Routine serodiagnosis that detects Ig G against T. cruzi is only helpful after the newborn reaches 6 months of ag e. Detection of specific IgM using recombinant antigens and PCR constitute excellent alternatives, but their feasibility from operational and cost-eff ective viewpoints in affected endemic areas remains to be considered. In a longitudinal project carried out in Maternidad Nuestra Senora de la Merced in the city of Tucuman between 1992-1994, the majority of congenital cases were asymptomatic. They were diagnosed through the microhematocrit techniqu e, but a number of cases could only be detected later as a result of the pa rasitological and/or serological follow-up. Of a total of 32 newborns infec ted with T. cruzi who were treated with nifurtimox or benznidazole, 30 had a negative microhematocrit and serodiagnosis between 6 months and 2 years p ost-treatment. The magnitude of congenital transmission, and its associated morbidity and mortalidad, largely justify the efforts needed to detect T. cruzi infection in the mothers and newborns. This project demonstrated that the transmission of T. cruzi can be succesfully controlled at a provincial scale through a specific program inserted in the primary health care syste m or at the first level of attention. The congenital transmission of T. cru zi clearly represents a public health problem in areas that in the past wer e of active transmission, even years after being under entomologic surveill ance.