Comprehensive Survey of Domiciliary Triatomine Species Capable of Transmitting Chagas Disease in Southern Ecuador

<div><p>Background</p><p>Chagas disease is endemic to the southern Andean region of Ecuador, an area with one of the highest poverty rates in the country. However, few studies have looked into the epidemiology, vectors and transmission risks in this region. In this study we describe the triatomine household infestation in Loja province, determine the rate of <i>Trypanosoma cruzi</i> infection in triatomines and study the risk factors associated with infestation.</p><p>Methodology/Principal Findings</p><p>An entomological survey found four triatomine species (<i>Rhodnius ecuadoriensis</i>, <i>Triatoma carrioni</i>, <i>Panstrongylus chinai</i>, and <i>P</i>. <i>rufotuberculatus)</i> infesting domiciles in 68% of the 92 rural communities examined. Nine percent of domiciles were infested, and nymphs were observed in 80% of the infested domiciles. Triatomines were found in all ecological regions below 2,200 masl. We found <i>R</i>. <i>ecuadoriensis</i> (275 to 1948 masl) and <i>T</i>. <i>carrioni</i> (831 to 2242 masl) mostly in bedrooms within the domicile, and they were abundant in chicken coops near the domicile. Established colonies of <i>P</i>. <i>chinai</i> (175 to 2003 masl) and <i>P</i>. <i>rufotuberculatus</i> (404 to 1613 masl) also were found in the domicile. Triatomine infestation was associated with surrogate poverty indicators, such as poor sanitary infrastructure (lack of latrine/toilet [w = 0.95], sewage to environment [<i>w</i> = 1.0]). Vegetation type was a determinant of infestation [<i>w</i> = 1.0] and vector control program insecticide spraying was a protective factor [<i>w</i> = 1.0]. Of the 754 triatomines analyzed, 11% were infected with <i>Trypanosoma cruzi</i> and 2% were infected with <i>T</i>. <i>rangeli</i>.</p><p>Conclusions/Significance</p><p>To date, only limited vector control efforts have been implemented. Together with recent reports of widespread sylvatic triatomine infestation and frequent post-intervention reinfestation, these results show that an estimated 100,000 people living in rural areas of southern Ecuador are at high risk for <i>T</i>. <i>cruzi</i> infection. Therefore, there is a need for a systematic, sustained, and monitored vector control intervention that is coupled with improvement of socio-economic conditions.</p></div

Triatomine infestation in Loja Province, a region of southern Ecuador having several ecological regions.

<p>Location of each community surveyed is marked. The size of the symbol corresponds to the % of houses infested with triatomines in each community. The colors represent the four triatomine species found: Red = <i>R</i>. <i>ecuadoriensis</i>, blue = <i>T</i>. <i>carrioni</i>, green = <i>P</i>. <i>rufotuberculatus</i> and yellow = <i>P</i>. <i>chinai</i>. Classification of ecological regions as per Sierra et al [<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0004142#pntd.0004142.ref014" target="_blank">14</a>].</p

Livestock found in rural communities of Loja Province.

<p>^a total n varies among each item from 3,015 to 3,032 due to missing values.</p><p>^b Median and Interquartile Range (IR) of animals per domicile</p><p>Livestock found in rural communities of Loja Province.</p

Peridomestic materials and vegetation, found in rural communities of Loja Province.

<p>^a total n varies among each item from 2,078 to 2,097 due to missing values.</p><p>^b Median and Interquartile Range of distance in meters from domicile (IR)</p><p>Peridomestic materials and vegetation, found in rural communities of Loja Province.</p

Comparison of PCR and Microscopy for <i>T</i>. <i>cruzi</i> and <i>T</i>. <i>rangeli</i> detection in triatomines.

<p>ME: microscopy examination;</p><p>PCR: Polymerase Chain Reaction</p><p>Comparison of PCR and Microscopy for <i>T</i>. <i>cruzi</i> and <i>T</i>. <i>rangeli</i> detection in triatomines.</p

Population structure of triatomines collected in rural communities of Loja Province, Ecuador.

<p>Number of live Nymphal I—V instars and adult female and male bugs collected in domestic (Dom) and peridomestic (Peri) habitats. A) <i>R</i>. <i>ecuadoriensis</i>, B) <i>T</i>. <i>carrioni</i>, C) <i>P</i>. <i>chinai</i> and D) <i>P</i>. <i>rufotuberculatus</i>.</p

Characteristic of domiciles from 92 communities located in rural areas of Loja Province.

<p>^a total n varies among each item from 2.996 to 3,039 due missing values.</p><p>^b total n varies among each item from 2,099 to 2,204 due to a change on the questionnaire form in 2008 and some missing values.</p><p>^c Inhabitant crowding = more than 3 people per bedroom.</p><p>Characteristic of domiciles from 92 communities located in rural areas of Loja Province.</p

Distribution of triatomine species in domestic and peridomestic environments in central coastal Ecuador

Although the central coast of the Ecuador is considered endemic for Chagas disease, few studies have focused on determining the risk of transmission in this region. In this study we describe the triatomine household infestation in Manabí province (Central Coast region), determine the rate of Trypanosoma cruzi infection and study the risk factors associated with infestation by Rhodnius ecuadoriensis.An entomological survey found three triatomine species (Rhodnius ecuadoriensis, Panstrongylus rufotuberculatus and P. howardi) infesting domiciles in 47.4% of the 78 communities visited (total infestation rate of 4.5%). Four percent of domiciles were infested, and nymphs were observed in 77% of those domiciles. The three species were found in altitudes below 500 masl and in all ecological zones except cloud forest. Within the domicile, we found the three species mostly in bedrooms. Rhodnius ecuadoriensis and P. rufotuberculatus were abundant in bird nests, including chicken coops and P. howardi associated with rats in piles of bricks, in the peridomicile. Triatomine infestation was characterized by high rates of colonization, especially in peridomicile. Flagelates infection was detected in only 12% of the samples by microscopy and Trypanosoma cruzi infection in 42% of the examined triatomines by PCR (n = 372). The most important risk factors for house infestation by R. ecuadoriensis were ecological zone (w = 0.99) and presence of chickens (w = 0.96). Determinants of secondary importance were reporting no insecticide applications over the last twelve months (w = 0.86) and dirt floor (w = 0.70). On the other hand, wood as wall material was a protective factor (w = 0.85).According the results, approximately 571,000 people would be at high risk for T. cruzi infection in Manabí province. A multidisciplinary approximation and the adhesion to a periodic integrated vector management (IVM) program are essential to guarantee sustainable preventive and control strategies for Chagas disease in this region