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)

Abstract

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.

Triatomine Infestation in Guatemala: Spatial Assessment after Two Rounds of Vector Control

“…11,12 These two vectors have distinct ecological characteristics, although they have similar rates of natural infection. 13 The former is a nonnative species that the PAHO officially regards as eliminable from Central America, because they can only survive in domestic settings. 8 The latter can live in both the natural environment and domestic settings, making it especially difficult to control and impossible to eliminate.…”

Environmental determinants of the distribution of Chagas disease vectors in south-eastern Guatemala

“…These are Triatoma dimidiata, Rhodnius prolixus, and T. nitida (Tabaru et al, 1999). The former two species are considered the principal Chagas disease vectors in the country based on their distribution and vector capacity (Schofield and Dujardin, 1997;Monroy et al, 2003c). T. nitida appears to have less vector importance due to its scarce presence in domestic habitats and inefficient defecation patterns (Monroy et al, 2003b).…”

The number of families of Triatoma dimidiata in a Guatemalan house

“…It is found in 21 of the 22 provinces of the country (Monroy et al 2003a) with the highest house infestation indices (12-45%) in the Eastern region. This is also the region which also has the highest prevalence of the disease (Monroy et al 2003a).…”

“…If vectors migrate frequently between houses, the degree of kinship between individuals within one house can be expected to decrease. A high migration rate would indicate high capacity to spread the disease (Monroy et al 2003a).…”

“…In this study the population dynamics of T. dimidiata was examined using random amplification of polymorphic DNA based on the polymerase chain reaction (RAPD-PCR), a technique previously shown to be useful for vector population studies (Monroy et al 2003a). RAPD-PCR has been used to estimate the number of full-sib families of mosquitoes in oviposition sites (Apostol et al 1993, 1994, Monroy et al 1998, with similar results to those observed with codominant markers (Colton et al 2003).…”