The fauna and the geographical distribution of vectors of Chagas' disease were investigated based on the man-hour collection, from mud walls or palm-thatched houses in 236 villages, from the year 1995 through 1997, throughout Guaternala. A total of 1,131 vectors cornprising 731 (64,6%) of Triatoma dimidiata, 53 (4,7%) of Tl nitida and 347 (30,7%) ofRhodniusProlixus were found. 71 dimidiata was collected in 16 eut of 22 departments, whereas R. Prolixus was collected in five departments, and T nitida was collected only in three departments. The total number of R, prolixus was not small, 85% of the bugs was collected frorn 800 m to 1,400 m above sea level in the present study areas. We collected more bugs in the east and the southeast departrnents of the country, such as in the borders with Honduras and El Salvador. The rate of positive houses with bugs is the highest in Jutiapa, followed by Alta Verapaz, Chiquimula, Santa Rosa, and Quiche. The bug density in the investigated houses is the highest in Chiquimula, while the geographical dispersion of bugs is the widest in Jutiapa. The natural infection of bugs with Trypanosoma cntzi is the highest in Zacapa. Based on the above-rnentioned positive rate of bugs and from the data of the 1994 National Census in Guatemala, we concluded

Many genetic studies using human mtDNA or the Y chromosome have been conducted to elucidate the relationships among the three Native American groups speaking Amerind, Na-Dene, and Eskimo-Aleut. Human polyomavirus JC (JCV) may also help to gain insights into this issue. JCV isolates are classified into more than 10 geographically distinct genotypes (designated subtypes here), which were generated by splits in the three superclusters, Types A, B, and C. A particular subtype of JCV (named MY) belonging to Type B is spread in both Japanese/Koreans and Native Americans speaking Amerind or Na-Dene. In this study, we evaluated the phylogenetic relationships among MY isolates worldwide, using the whole-genome approach, with which a highly reliable phylogeny of JCV isolates can be reconstructed. Thirty-six complete sequences belonging to MY (10 from Japanese/Koreans, 24 from Native Americans, and 2 from others), together with 54 belonging to other subtypes around the world, were aligned and subjected to phylogenetic analysis using the neighbor-joining and maximum-likelihood methods. In the resultant phylogenetic trees, the MY sequences diverged into two Japanese/Korean and five Native American clades with high bootstrap probabilities. Two of the Native American clades contained isolates mainly from Na-Denes and the others contained isolates mainly from Amerinds. The Na-Dene clades were not clustered together, nor were the Amerind clades. In contrast, the two Japanese/Korean clades were clustered at a high bootstrap probability. We concluded that there is no distinction between Amerinds and Na-Denes in terms of indigenous JCVs, although they are linguistically distinguished from each other.

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. Key words: Trypanosoma infection rate -Triatoma dimidiata -Triatoma nitida -Rhodnius prolixus -vectors' sex ratioGuatemalaTrypanosoma cruzi and Trypanosomana rangeli are parasitic protozoans of insect vectors of the Triatominae subfamily and vertebrates, specifically mammals. T. cruzi is the causative agent of Chagas disease, while T. rangeli is non pathogenic to humans and other vertebrate hosts. In the vector, T. cruzi develops in the intestinal tract, while T. rangeli has the ability to invade and develop in the hemolymph and salivary glands (Grisard et al. 1999). In Guatemala, the first reports of the presence of T. cruzi and T. rangeli in humans were in 1932 and 1934, respectively (Reichnow 1933, Blanco 1943, De León 1949.Reports of T. cruzi and T. rangeli infection in triatomine vectors of Central America, suggest that rates of infection differ among species and regions. For example, in Panama, Sousa and Johnson (1973) Reports of the infection rates of T. rangeli in the vectors from South America also give some idea of differences between regions. Marinkelle (1968), in Colombia, reported five out of 29 T. dimidiata capitata infected with T. rangeli in the salivary glands.In addition to variable rates of parasite infection among vectors, different rates of human infection are related with different vector species or populations, suggesting that vectors may differ in their ability to transmit T. cruzi. For example, in Guatemala, T. dimidiata appears to be associated with lower levels of human seroprevalence compared to R. prolixus. In one village of the department of Zacapa where R. prolixus was the principal vector, the seroprevalence amongst 373 people tested was 38.8%. In another village in the department of Santa Rosa, where the only vector found was T. dimidiata, a much lower seroprevelance rate was found: 8.9% of the 428 people tested were seropositive for T. cruzi (Paz-Bailey et al. 2002). This trend was also noted in Honduras in a region where 35% of houses were infested with R. prolixus, seroprevalence in the population was 40%, while in another area, where only T. dimidiata was present, the prevalence of human infection was only 15% (Ponce et al. 1995). These results suggest that R. prolixus is a more efficient vector than T. dimidiata.

The number of Triatoma dimidiata found per rnan-hour of collection in each of the three mud-walled houses were 4, 1 and 37, In the third house 8 of T nitida were also collected.When the walls of these houses were dismantled, an additional 1 14, !41 and 307 of Tl dimidiata were cellected along with 34 of T nitida in the third house, In the palm-thatch roofed huts only Rhodnius Protixus were collected. The numbers per man-hour collected were 1 1, 27 and 26. When the roofs were dismantled and searched 75, 449 and 978 bugs were found in the respective houses. These results indicate that the numbers collected by the traditional method did not accurately refiect the population density in the houses, The collections indicate that the hiding places of 71 dimidiata and R, Prolixus were very lirnited within the houses, An average of 31% of T dimidinta were collected in only two dismantled block sections (2m2) which were close to the beds and chicken nest and 40% of R. protixus in the last house were obtained in the lower section of the palm-thatched roofs just abeve a bed, This area occupied only 4.2% area in total space of the house, These results suggest that insecticidal treatments would be most effective if they focused on the places where more bugs concentrate.

Chemical control of Tn'atoma dimidiata and Rhodnius prolixus