Sympatry influence in the interaction of Trypanosoma cruzi with triatomine

Abstract INTRODUCTION: 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. RESULTS: 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%). CONCLUSIONS: 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.

The relationship of sex and ectoparasite infestation in the water rat Scapteromys aquaticus (Rodentia: Cricetidae) in La Plata, Argentina

I studied the relationship between sex and infestation with ectoparasites in the water rat Scapteromys aquaticus from La Plata river marshland, Argentina. The Relative Density's Index (RDI) for males was 3.90% (females 3.60%). A total of 2653 ectoparasites were collected on 33 male hosts, and 1945 on 31 females. Ectoparasite specific richness (S) and diversity (H) were S = 14, H = 1.17 on males, and S = 10, H = 1.52 on females. The similarity between male and female rodents according to their ectoparasites was 75.00%. Although no ectoparasite species showed significant mean abundance (MA) differences between host sexes (p < 0.05), and only Laelaps manguinhosi prevalence was significantly higher on male hosts (N = 2.01, p < 0.05) in this study, there are reasons to think that the sex of the water rat affects ectoparasite burden and specific richness. This information has epidemiological potential because the closely related Scapteromys tumidus is involved in the transmission of Rickettsia coronii, which causes Marsella fever in humans.

Se estudió la interrelación entre el sexo de la rata de agua Scapteromys aquaticus y su infestación por ectoparásitos en la ribera del Río de la Plata, Argentina. El índice de densidad relativa de los machos fue 3.90 % y el de las hembras 3.60%. Se recolectó 2653 ectoparásitos de 33 machos y 1945 de 31 hembras. La riqueza (S) y diversidad específicas (H) de los ectoparásitos fueron S = 14, H = 1.17 en los machos y S = 10, H = 1.52 en las hembras. La similitud entre sexos fue del 75.00%. Si bien ningún ectoparásito en este estudio mostró diferencias significativas en su abundancia media entre los hospedadores de diferente sexo (p<0.05) y sólo la prevalencia de Laelaps manguinhosi fue significativamente mayor en los machos (N = 2.01, p<0.05), otros datos sugieren que sí existe un patrón de diferencias sexuales.