Primer hallazgo de vectores de la enfermedad de Chagas asociados a matorrales silvestres en la Región Metropolitana, Chile / First finding of Chagas disease vectors associated with wild bushes in the Metropolitan Region of Chile

Background: Insects of the subfamily triatominae are the biological vectors of Trypanosoma cruzi, the causal agent of Chagas disease. Aim: To search for wild colonies of triatomines in the Metropolitan Region of Chile. Material and Methods: Ad hoc traps were placed in two endemic zones of the Metropolitan Region of Chile, during 30 nights. The dejections of 16 T infestans and 43 M spinolai specimens were examined under the microscope, searching for live metacyclic trypomastigotes. A polymerase chain reaction (PCR) was performed in macerates of all insects looking for T cruzi DNA. Results: A total of 269 bugs were captured. Forty four were Triatoma infestans and 225 were Mepraia spinolai. They were not syntopic, since T infestans was restricted to a Southern zone (Calera de Tango) while M spinolai was only found in the Northern zone (Til-Til). Both species were found associated to terrestrial bromeliads (Puya sp) but M spinolai was also detected in stony grounds. Microscopic examination of dejections yielded a trypano-triatomine index of 56.3 and 32.6 for T infestans and M spinolai, respectively. PCR detected T cruzi DNA in 41 and 43 percent of T infestans and M spinolai specimens, respectively. Conclusions: The finding of T infestans in a wild habitat is noticeable. This is the first report of such phenomenon in Chile. The high infection rates with T cruzi, explains the maintenance of Chagas disease wild cycle in Chile.

Certificación serológica de la interrupción de la transmisión vectorial de la enfermedad de Chagas en Chile / Serological certification of the interruption of the vectorial transmission of Chagas disease in Chile

Background: In 1999 an International Commission of Experts evaluated the sanitary interventions that started in 1980 to eliminate Triatoma infestans, the biological vector of Chagas disease, to certify if the conditions needed to interrupt the transmission, were achieved. Aim: To report the data used by the International certification commission to certify the interruption of vectorial transmission of Chagas disease in Chile. Material and methods : A comparative evaluation of the prevalence of Trypanosoma cruzi antibodies in children surveyed between 1994 and 1995 and between 1995 and 1999. Results : In the first period, 5.948 children were surveyed and in the second, 5.069 children were studied. Twenty children (0.4 percent) were positive for Trypanosoma cruzi antibodies in the second survey. These figures were significantly lower than the 1.1 percent prevalence detected between 1994 and 1995. In only three of the 20 cases, the transmission through vectors was confirmed, which represents a 99.4 percent reduction of this way of transmission. Conclusions: Based on these findings, the Commission certified that Chile is the second country in Latin America to interrupt the vector transmission of Chagas disease. The successful public health program for Chagas disease will have a positive impact improving the quality of life of rural populations, that are most exposed to the disease

Estudio clínico y epidemiológico en donantes de sangre seropositivos por trypanosoma cruzi / Clinical and epidemiological study of blood donors seropositive for Chagas disease

One hundred eleven seropositive donors, detected between 1994 and 1996, were studied. Serological reactions were confirmed with ELISA and indirect immunofluorescence reactions. Those confirmed as positive were subjected to a clinical-epidemiological questionnaire, physical examination, EKG and barium enema or swallow according to symptoms. Results: Seventy individuals were confirmed as positive for Chagas disease. Most of them lived at least once in an endemic zone for Chagas positive for Chagas disease. Most of them lived at least once in an endemic zone for Chagas disease or in a sun-dried clay brick house. Forty percent of individuals knew reduviid bugs and 14 pecent had been bitten by these insects. Twenty six percent of these subjects had an abnormal EKG (6 percent with bradicardia). No digestive diseases attributable to Chagas disease were detected. Conclusions: The high prevalence of problems attributable to Chagas disease among seropositive blood donors underscores the need of an epidermiological follow up of these individuals

Evaluación de reactivos comerciales empleados en el diagnóstico de la enfermedad de Chagas en bancos de sangre de Chile: II aplicación rutinaria / Assesement of comercial kits used for Chagas' diseases diagnosis in blood banks: II routinary use

Aiming to study the applicability and reproducibility of four comercial kits used for the serological detection of Chagas disease (Chagatest-Inst Invest Paraguay, Ortho Chagas, Abbott Chagas (ELISA tests) and Estabilgen Hemo Chagas (indirect hemagglutination test), a comparative serological study was performed in 256 sera samples coming from a highly endemic area, 249 samples from a low endemic area, 180 reference sera and 2264 samples coming from three blood banks. Specificity of the kits was excellent and sensitivity ranged from 60 to 100 percent. The indirect hemagglutination test has the lower sensitivity. Some disagreements in the results were observed in the three blood banks, probably due to an unsatisfactory reactive management. We conclude that ELISA tests should be recommended for routine detection of Chagas disease and that for this purpose, a net of laboratories under the direction of a national reference center should exist. This center should assess new commercial products, train technicians and supervise the laboratories