Abstract
Trypanosoma cruzi, the etiologic agent of Chagas disease, is widely distributed in nature, circulating between triatomine bugs and sylvatic mammals, and has large genetic diversity. Both the vector species and the genetic lineages of T. cruzi present a varied geographical distribution. This study aimed to verify the influence of sympatry in the interaction of T. cruzi with triatomines. Methods: The behavior of the strains PR2256 (T. cruzi II) and AM14 (T. cruzi IV) was studied in Triatoma sordida (TS) and Rhodnius robustus (RR). Eleven fifth-stage nymphs were fed by artificial xenodiagnosis with 5.6 × 103 blood trypomastigotes/0.1mL of each T. cruzi strain. Every 20 days, their excreta were examined for up to 100 days, and every 30 days, the intestinal content was examined for up to 120 days, by parasitological (fresh examination and differential count with Giemsa-stained smears) and molecular (PCR) methods. Rates of infectivity, metacyclogenesis and mortality, and mean number of parasites per insect and of excreted parasites were determined. Sympatric groups RR+AM14 and TS+PR2256 showed higher values of the four parameters, except for mortality rate, which was higher (27.3%) in the TS+AM14 group. General infectivity was 72.7%, which was mainly proven by PCR, showing the following decreasing order: RR+AM14 (100%), TS+PR2256 (81.8%), RR+PR2256 (72.7%) and TS+AM14 (36.4%). Our working hypothesis was confirmed once higher infectivity and vector capacity (flagellate production and elimination of infective metacyclic forms) were recorded in the groups that contained sympatric T. cruzi lineages and triatomine species.
Highlights
Trypanosoma cruzi, the etiologic agent of Chagas disease, is widely distributed in nature, circulating between triatomine bugs and sylvatic mammals, and has large genetic diversity
Mean number of ingested parasites was 10,202 and 8,334 parasites for the groups formed by R. robustus + T. cruzi II (RR+PR2256) and R. robustus + T. cruzi IV (RR+AM14), respectively
In T. sordida + T. cruzi II (TS+PR2256), insects ingested an average of 2,464 parasites, a higher number when compared to that of T. sordida + T. cruzi IV (TS+AM14) which was 1,182 parasites, with a high standard deviation in the first group
Summary
Trypanosoma cruzi, the etiologic agent of Chagas disease, is widely distributed in nature, circulating between triatomine bugs and sylvatic mammals, and has large genetic diversity. Triatomines (Hemiptera: Reduviidae) are recognized as vectors of Trypanosoma cruzi, the etiologic agent of Chagas disease or American trypanosomiasis in Latin America[1,2] This disease is considered to be the fourth most prevalent parasitic disease, with approximately 300,000 new cases registered annually. Transmission of T. cruzi occurs through vectorial route, which involves contact of the vertebrate hosts with the excreta of vector bugs, contaminated with metacyclic trypomastigotes. This is the primary mechanism for the spread of the disease. The other mechanisms of transmission, referred to as the secondary mechanisms[5], such as infections caused by blood transfusion, congenital transmission, and
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