A preliminary assessment of genetic differentiation of Triatoma dimidiata (Hemiptera: Reduviidae) in Guatemala by random amplification of polymorphic DNA-polymerase chain reaction.

The population genetics of Triatoma dimidiata (Latreille, 1811) from five different provinces in Guatemala, including three sylvan and three domestic populations, was investigated by random amplification of polymorphic DNA-polymerase chain reaction. There is a high degree of genetic variation in all of the T. dimidiata populations as evidenced by high levels of average expected heterozygosity and polymorphism. Domestic populations are more closely related to each other (D = 0.05-0.085, Nei's genetic distance) than are the sylvan (D = 0.121-0.189). Within the limited sample size of three populations, there was a correlation with geographic and genetic distance for the domestic populations, but not for the sylvan. Surprisingly, one of the sylvan populations was genetically very similar to the domestic populations. The FST demonstrated a high degree of differentiation at the country-wide level (FST = 0.175) and a moderate degree of differentiation within the sylvan (FST = 0.135) or domestic (FST = 0.097) populations. Although these results demonstrated that gene flow is limited between different provinces in Guatemala, hierarchical analysis showed that barriers between the Atlantic and Pacific drainage slopes were not biologically significant limiters of gene flow.

Dispersion and colonization of Triatoma ryckmani (Hemiptera: Reduviidae) in artificial environments in a semiarid region of a Chagas disease endemic area in Guatemala.

The colonization capacity and dispersal of sylvatic populations of Triatoma ryckmani Zeledón and Ponce were investigated by means of experimental chicken coops installed within the semiarid region in the Department of El Progreso, Guatemala. In the four artificial habitats a total of 672 T. ryckmani was found as well as two males of T. dimidiata (Latreille). Triatomine densities were not the same in the four chicken coops. From one chicken coop 53.4% (359) of the triatomines were collected. Full colonization, i.e. all stages from egg to adult found at the same time, took place in the fourth month after the first female's arrival. High dispersal and colonization capacity of T. ryckmani was evident; adult dispersal occurs mainly during the dry and coolest season (November-February). The overall female/male sex ratio was 2:1; more females than males were found throughout the year. Most of the triatomines in the shelter inside the chicken coops were found on the northern (43%; with less heat and sunlight) and eastern side (35%; more windy). This is the first report on the colonization capacity and population dynamics of T. ryckmani in artificial habitats in a Chagas disease endemic area of Central America.

The Chagas vector, Triatoma dimidiata (Hemiptera: Reduviidae), is panmictic within and among adjacent villages in Guatemala.

Trypanosoma cruzi, the hemoflagellate parasite and cause of Chagas disease in Latin America, is carried by Triatomine vectors, principally Triatoma dimidiata and Rhodnius prolixus in Central America. To assist control efforts and to understand the epidemiology of the disease in Guatemala, the population genetics of T. dimidiata was analyzed among three houses within a village and two adjacent villages in Guatemala. Eleven Randomly Amplified Polymorphic DNA-polymerase chain reaction (RAPD-PCR) primers were screened and three used to amplify bands, 29 of which were scored, from T. dimidiata DNA of approximately 50 bugs per house from three houses within a village and from 66 and 33 bugs, respectively, from adjacent villages. Results show very small genetic distances among the three T. dimidiata subpopulations from the houses (D = 0.013-0.022) and the two villages (D = 0.0199). The amount of differentiation among houses (fixation index, F(ST)) was also very small, F(ST) = 0.025 among the houses and the two villages F(ST) = 0.019. These fixation indices give an average number of mating migrants per generation (Nm) of 9.7 (among houses) and 12 (among villages). Average heterozygosity (H) appears to be high, ranging from H = 0.299-0.325 among the houses and H = 0.273 among the villages. The low genetic distance and fixation indices, and high heterozygosity suggest that the subpopulations in the houses and in the adjacent villages are not reproductively isolated but are in fact, one large panmictic population. Therefore the geographic coverage necessary for effective control must include, at least, the area encompassing adjacent villages.

Epidemiology of Chagas disease in Guatemala: infection rate of Triatoma dimidiata, Triatoma nitida and Rhodnius prolixus (Hemiptera, Reduviidae) with Trypanosoma cruzi and Trypanosoma rangeli (Kinetoplastida, Trypanosomatidae).

A five-year domiciliary collection in the 22 departments of Guatemala showed that out of 4,128 triatomines collected, 1,675 were Triatoma dimidiata (Latreille, 1811), 2,344 were Rhodnius prolixus Stal 1859, and only 109 were T. nitida Usinger 1939. The Chagas disease parasite, Trypanosoma cruzi, was found in all three species. Their natural infection rates were similar in the first two species (20.6%; 19.1%) and slightly lower in T. nitida(13.8%). However there was no significant difference in the infection rates in the three species (p = 0.131). T. dimidiata males have higher infection rates than females (p = 0.030), whereas for R. prolixus there is no difference in infection rates between males and females (p = 0.114). The sex ratios for all three species were significantly skewed. More males than females were found inside houses for T. dimidiata (p < 0.0001) and T. nitida (p = 0.011); a different pattern was seen for R. prolixus (p = 0.037) where more females were found. Sex ratio is proposed as an index to show the mobility of T. dimidiata in different populations. T. dimidiata is widely distributed in the country, and is also the main vector in at least ten departments, but R. prolixus with higher vectorial capacity is an important vector in at least two departments.

Geographic distribution and morphometric differentiation of Triatoma nitida usinger 1939 (Hemiptera: Reduviidae: Triatominae) in Guatemala.

Triatoma nitida was found in 14 (0.4%) out of 3,726 houses located in six departments across Guatemala, which were surveyed from 1994 to 1998 by the man-hour collection method. Compared to previous information, the distribution of T. nitida in Guatemala has increased from five to nine departments; the species is present in mild climates at altitudes from 960 to 1,500 m. Fourteen percent of the intradomestic T. nitida were infected with Trypanosoma cruzi. The species was often found in conjunction with other triatomines (T. dimidiata and Rhodnius prolixus). The domestic and peridomestic presence of T. nitida in Guatemala was rare, but occasionally this species was colonizing human-made constructions. T. nitida appears to have a low importance as Chagas disease vector in Guatemala, as indicated by its scarce presence in the domestic habitats and defecation patterns. However, it clearly has potential to become a Chagas vector so we recommend an on-going study of the intradomestic presence of T. nitida following the control programs in Guatemala. Morphometric analysis of 47 T. nitida males from three localities showed quantitative differences between the populations, which indicates that geographic distance is an important factor in the structuring of T. nitida populations.

Geographic distribution and morphometric differentiation of Triatoma nitida usinger 1939 (Hemiptera: Reduviidae: Triatominae) in Guatemala

Triatoma nitida was found in 14 (0.4 percent) out of 3,726 houses located in six departments across Guatemala, which were surveyed from 1994 to 1998 by the man-hour collection method. Compared to previous information, the distribution of T. nitida in Guatemala has increased from five to nine departments; the species is present in mild climates at altitudes from 960 to 1,500 m. Fourteen percent of the intradomestic T. nitida were infected with Trypanosoma cruzi. The species was often found in conjunction with other triatomines (T. dimidiata and Rhodnius prolixus). The domestic and peridomestic presence of T. nitida in Guatemala was rare, but occasionally this species was colonizing human-made constructions. T. nitida appears to have a low importance as Chagas disease vector in Guatemala, as indicated by its scarce presence in the domestic habitats and defecation patterns. However, it clearly has potential to become a Chagas vector so we recommend an on-going study of the intradomestic presence of T. nitida following the control programs in Guatemala. Morphometric analysis of 47 T. nitida males from three localities showed quantitative differences between the populations, which indicates that geographic distance is an important factor in the structuring of T. nitida populations

Habitats, dispersion and invasion of sylvatic Triatoma dimidiata (Hemiptera: Reduviidae: Triatominae) in Petén, Guatemala.

Dispersion and invasion capacity of sylvatic populations of Triatoma dimidiata (Latreille) were investigated during 14 mo by means of experimental chicken coops installed in a nature reserve within the Maya Biosphere, Petén, Guatemala. In addition, palm trees, underground archeological holes (chultunes) and piles of limestones within the forest were inspected as potential sylvatic habitats of T. dimidiata. From the three types of sylvatic habitats we inspected, all served as shelter and breeding sites for T dimidiata. The natural infection of these bugs (n = 72) with Trypanosoma cruzi (Chagas) was high (25%) and represent a risk for humans who colonize the forest. T. dimidiata quickly invaded the experimental chicken coops installed in the primary forest, albeit at very low densities. However, only one adult bug was encountered in the chicken coops installed in a secondary forest. Dispersal of adult T. dimidiata was most apparent at the end of the dry season. Overall, our results indicate a potential risk for invasion by sylvatic T. dimidiata of domestic environments in this area, with a risk of T. cruzi transmission to humans. We suggest that a system of community-based surveillance should be developed to detect new infestations and organize prompt treatment of any new cases of acute Chagas disease that may result.