[Control of congenital transmission of Trypanosoma cruzi in Argentina].

The vertical transmission of Trypanosoma cruzi has been augmenting its relative importance as vector and transfusion-mediated transmission routes have been, and continue to be, increasingly controlled. The vertical transmission of T. cruzi cannot be prevented; but early detection and treatment of congenital infection achieve cure rates close to 100%. In Argentina, the Subprogram 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 maternal prevalence rates of T. cruzi, only a small proportion of live newborns 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. Other more recent studies in Argentina estimated the probability of transmission in 2.6%-6.7%, but studies from Paraguay estimated 10.5% by PCR or serodiagnosis. The microhematocrit technique is the recommended parasitologic method to detect congenital infection. Routine serodiagnosis that detects IgG against T. cruzi is only helpful after the newborn reaches 6 months of age. Detection of specific IgM using recombinant antigens and PCR constitute excellent alternatives, but their feasibility from operational and cost-effective viewpoints in affected endemic areas remains to be considered. In a longitudinal project carried out in Maternidad Nuestra Señora de la Merced in the city of Tucumán between 1992-1994, the majority of congenital cases were asymptomatic. They were diagnosed through the microhematocrit technique, but a number of cases could only be detected later as a result of the parasitological and/or serological follow-up. Of a total of 32 newborns infected with T. cruzi who were treated with nifurtimox or benznidazole, 30 had a negative microhematocrit and serodiagnosis between 6 months and 2 years post-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 successfully controlled at a provincial scale through a specific program inserted in the primary health care system or at the first level of attention. The congenital transmission of T. cruzi clearly represents a public health problem in areas that in the past were of active transmission, even years after being under entomologic surveillance.

Blanco SB ，Segura EL ，Gürtler RE 《MEDICINA-BUENOS AIRES》

High prevalence of congenital Trypanosoma cruzi infection and family clustering in Salta, Argentina.

Trypanosoma cruzi, the causative agent of Chagas' disease, is transmitted mainly by insect vectors, but congenital and transfusion-borne infections occasionally occur. The factors that are involved in transmission from mother to offspring are not well understood. The objective of this study was to study the presence of T cruzi infection in children who were born to infected mothers and in the children's siblings to evaluate the epidemiologic risk factors associated with congenital transmission of Chagas' disease. Congenital T cruzi infection was studied in 340 children who were born to chronically infected mothers in Salta, Argentina. Infection was detected in 31 children, who were selected for additional study as infected index cases (IIC). Of the 309 noninfected children, 31 were taken as noninfected index cases (NIIC). We compared the prevalence of congenital T cruzi transmission in the remaining siblings of the IIC and NIIC. Data and blood samples were collected in house-to-house visits. Diagnosis of infection was established mainly by serologic methods, indirect hemmagglutination, and enzyme-linked immunosorbent assay. The prevalence was 31.4% (32 of 102 children) for IIC siblings, whereas no infected siblings were found in families with NIIC (0 of 112). Clustering of congenital infection was found in 14 families, in which >1 child was infected. Second-generation congenital transmission (from grandmother to mother to newborn) was established in 4 families. The association among low weight at birth, prematurity, and congenital transmission was highly significant. An important observation was the absence of pathologic findings in a high proportion of infected children. The detection of asymptomatic infections was a consequence of population screening, as opposed to hospital-based diagnosis, for which symptomatic cases predominate. Congenital transmission was associated with the geographic origin of mothers: women from areas where insect vectors proliferate were less likely to give birth to infected offspring than women from areas under active vector control. Siblings of an infant infected with T cruzi are at high risk for infection themselves and, even in the absence of symptoms, should also be screened for infection. The findings of family clustering of infection and of second-generation congenital infection in vector-free areas suggest that new modalities of transmission, other than classic vector-borne spread, may occur both in endemic and in nonendemic areas.

Sánchez Negrette O ，Mora MC ，Basombrío MA 《-》

[Congenital transmission of Trypanosoma cruzi infection in Argentina].

Congenital transmission of Trypanosoma cruzi infection in Argentina has being increasing its relative importance with control of vectorial and transfusional transmission growth. It is for this reason that vertical transmission is seen, in the future, as a continuous source of infected newborns, even with vectorial and transfusional transmission completely controlled. Preventing vertical transmission of T.cruzi is not possible, but it can be precociously detected, permitting mother and child to be incorporated into the medical attention system, and so allowing the newbornś treatment with practically 100% efficacy. It is estimated that between 800 and 1700 children infected with T. cruzi by congenital transmission are born in Argentina, per year. The implementation of an early strategy of detection for an effective and opportune treatment acquires great relevance as a Public Health measure.

Sosa-Estani S 《Revista da Sociedade Brasileira de Medicina Tropical》

[Control of the transmission of Trypanosoma cruzi in Argentina 1999].

Approximately 2 million people in Argentina are infected with Trypanosoma cruzi, the etiologic agent of Chagas disease, thereby constituting the major tropical disease in the country. As in other six Southern Cone countries, Triatoma infestans is the only or major vector of T. cruzi among human and domestic animals. In Argentina, a vertically structured National Chagas Control Program was established in 1962. Such a program pursued the elimination of domestic and peri-domestic populations of T. infestans through insecticidal spraying, and the serological control of blood donors to prevent transfusion-related infections. This program strongly reduced the nation-wide serological prevalence of T. cruzi in the population. For example, in 18 or 20 year-old men drafted into military service, the seroprevalence decreased from 10.1% in 1964 for those who had been born in 1944 to 1.9% in 1993 for those born in 1975. However, the vertical strategy failed to reach and sustain the surveillance phase in widespread rural areas with disperse populations due to its intrinsic limitations and the reduced priority level assigned to rural health programs. An alternative, horizontally-structured control strategy of T. infestans was developed and assayed in the Province of Santiago del Estero between 1985-1989, and 1991-1992. The projects demonstrated that insecticidal spraying carried out with community participation combined effectiveness and commitment in such a way as to produce a strong impact on house reinfestation and the extension of the area under entomological surveillance. This experience has been transferred in a chain of responsibilities to the personnel of the National Chagas Control Program, using participating workshops, procedural guidelines, and practical training. This personnel transferred the strategy using similar methods to the field health care agents and volunteers chosen by their own communities (community leaders). After the workshops, the leaders received all the materials needed to install and develop the ongoing surveillance activities: third generation pyrethroid insecticides, manuals, hand-operated sprayers, and sensor boxes to detect domiciliary infestations. From 1993 to 1998, a total of 15,000 health care agents or community leaders were trained. A total of 675,000 houses were sprayed with residual insecticides in the attack phase, and 850,000 houses entered the surveillance phase. This is the first time that such large coverage has been accomplished in Argentina. The network of laboratories installed a quality assurance program to current serological procedures applied to blood donors, organ transplant, and the detection and treatment of newborns to women sero-reactive for T. cruzi in Argentina. We expect to interrupt the vector-mediated transmission of T. cruzi in the next 18 months, but the sustainability of such a program depends on, at least, additional work with the community to achieve a change of attitudes and practices related to house infestation for the next 10 years. A social effort will be needed to cover those expenses, but the expected economic returns exceed largely the cost of any such program, as suggested by cost-benefit studies. To illustrate, the annual treatment costs of one Chagas patient can help maintain 25 households free from triatomine bugs in Argentina.

Segura EL ，Sosa Estani S ，Esquivel ML ，Gómez A ，Salomon OD ... -  《MEDICINA-BUENOS AIRES》

Direct molecular profiling of minicircle signatures and lineages of Trypanosoma cruzi bloodstream populations causing congenital Chagas disease.

Congenital transmission of Trypanosoma cruzi may occur in some or all the gestations from a T. cruzi-infected mother. Variable rates of congenital transmission have been reported in different geographical areas where different parasitic strains predominate, suggesting that parasitic genotypes might play a role in the risk of congenital transmission. Moreover, in cases of transmission it is unknown if the whole maternal T. cruzi population or certain clones are preferentially transmitted by the transplacental route. In this study, bloodstream T. cruzi lineages were identified in blood samples from congenitally infected children, transmitting and non-transmitting mothers and unrelated Chagas disease patients, using improved PCR strategies targeted to nuclear genomic markers. T. cruzi IId was the prevalent genotype among 36/38 PCR-positive congenitally infected infants, 5/5 mothers who transmitted congenital Chagas disease, 12/13 mothers who delivered non-infected children and 28/34 unrelated Chagas disease patients, all coming from endemic localities of Argentina and Bolivia. These figures indicate no association between a particular genotype and vertical transmission. Furthermore, minicircle signatures from the maternal and infants' bloodstream trypanosomes were profiled by restriction fragment length polymorphism of the 330-bp PCR-amplified variable regions in seven cases of mothers and congenitally infected infants. Minicircle signatures were nearly identical between each mother and her infant/s and unique to each mother-infant/s case, a feature that was also observed in twin deliveries. Moreover, allelic size polymorphism analysis of microsatellite loci from populations transmitted to twins showed that all clones from the maternal polyclonal population were equally infective to both siblings.

Burgos JM ，Altcheh J ，Bisio M ，Duffy T ，Valadares HM ，Seidenstein ME ，Piccinali R ，Freitas JM ，Levin MJ ，Macchi L ，Macedo AM ，Freilij H ，Schijman AG ... -  《INTERNATIONAL JOURNAL FOR PARASITOLOGY》