Compared vectorial transmissibility of pure and mixed clonal genotypes of Trypanosoma cruzi in Triatoma infestans

Abstract

A total of 15 mixtures involving 9 different stocks attributed to the 19/20, 32 and 39 major clonal genotypes of Trypanosoma cruzi were used to infect third-instar nymphs of Triatoma infestans via an artificial feeding device. Three biological parameters were considered: (1) the percentage of infected insects (%II), (2) the number of flagellates per insect (NFI), and (3) the percentage of trypomastigotes per insect (%DIF). Genetic characterization by both multilocus enzyme electrophoresis (MLEE) and random amplification of polymorphic DNA (RAPD) indicated that in almost all cases (87%), mixtures remained present after completion of the whole cycle in the insect vector. Two lines of comparison were performed: (1) pure clonal genotypes versus corresponding mixed clonal genotypes and (2) the actual behavior of mixed clonal genotypes versus the expected behavior of the theoretical mixture (i.e. the arithmetic mean of the results observed for each of the two clonal genotypes taken separately). Statistical analyses of the variables were made difficult because of the presence of large standard deviations. Nevertheless, in several cases, mixtures differed significantly from pure clonal genotypes, and in one case the actual mixture differed significantly from the theoretical mixture. In some cases, interaction (either potentialization or reciprocal inhibition) could be suspected.

Differential Pattern of Infection of Sylvatic Nymphs and Domiciliary Adults of Triatoma infestans with Trypanosoma cruzi Genotypes in Chile

“…58,60 Moreover, under long periods of starvation, 99.5% of T. cruzi in the rectum of an infected triatomine can be killed, and T. cruzi population density in the small intestine and rectum is reduced. 61 Thus, adults probably undergo this process several times during their lifetime, which filters many genotypes and retains and proliferates those genotypes that are more resistant to adverse situations, both from the vector, such as trypanolytic compounds, digestive enzymes, and lectins, 62 and environmental ones, such as resident bacteria in the gut, temperature variation, 62 and resource shortage.…”

Impact of Dual Infections on Chemotherapeutic Efficacy in BALB/c Mice Infected with Major Genotypes ofTrypanosoma cruzi

“…Our group verified that in mixed infections, interactions between populations of T. cruzi may occur, resulting in important changes in the biological characteristics of the parasite and the evolution of the infection (12,25,32). Moreover, the importance of mixed infections in the epidemiology of Chagas' disease (8,35) and the evidence that they may result in significant alterations in the host-parasite relationship motivated the studies on the efficacy of chemotherapy in dual infections.…”

“…Interactions between T. cruzi clonal stocks of different genotypes suggesting reciprocal stimulation or inhibition were already demonstrated in experimental infections of Triatoma infestans (12,32) and mice (25). Those authors observed that clones with a low ability to develop in invertebrate or vertebrate hosts in monoclonal infections were able to multiply and to remain in mixed infections (19 or 20 ϩ 32) at levels even higher than that of the most virulent clone.…”

“…At least in experimental mixed infections, important interactions between subpopulations of the mixtures resulted in changes in parasite biological properties (12,13,25,32). This suggests that mixed infections might have important consequences for morbidity, the dynamics of parasite transmission, and the response to chemotherapy, since individuals in areas where the disease is endemic may have undergone several reinfections (10).…”

Xenodiagnosis

“…Comparing two fresh isolates, both originating from T. vitticeps, one isolate infected 61% and the other one 39% of T. infestans (Kollien et al 1998). Clone or strain specificities are indicated not only by different numbers of parasites in the gut but also by different percentages of metacyclic trypomastigotes (e.g., Perlowagora-Szumlewicz et al 1990;Perlowagora-Szumlewicz and Moreira 1994;Alvarenga and Bronfen 1997;Pinto et al 1998;Lana et al 1998;Lima et al 1999). Using two T. cruzi strains from the same locality and T. infestans also originating from there, the number of metacyclics differed strongly .…”