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ARTICLE Sylvatic Triatominae of the Phyllosoma Complex (Hemiptera: Reduviidae) Around the Community of Carrillo Puerto, Nayarit, Mexico EZEQUIEL MAGALLÓN-GASTÉLUM,1 FELIPE LOZANO-KASTEN,1 ANGELICA FLORES-PÉREZ,2 MARIE-FRANCE BOSSENO,3 AND SIMONE F. BRENIÈRE3 J. Med. Entomol. 38(5): 638Ð640 (2001) KEY WORDS Triatoma longipennis, Triatoma picturata, sylvatic cycle, domestic cycle, Mexico VECTOR CONTROL HAS interrupted the transmission of Trypanosoma cruzi (L.) in most countries of South America (Dias 1993). Health authorities are attempting to establish similar programs in Central and North America; however, in these areas, the repopulation of treated communities by residual domestic populations or by the immigration of bugs from sylvatic foci have been reported (Harry et al. 1992; SchoÞeld 1995). A complete understanding of sylvatic triatomine life cycles will facilitate the modiÞcation of current control strategies to accommodate possible immigration into communities. In Mexico, 28 species of triatomine are known to occur, of which 18 have been found to be infected naturally with Trypanosoma cruzi. The majority of species found in human dwellings also are sylvatic, complicating control (Zárate and Zárate 1985; Velasco-Castrejón and Guzmán-Bracho 1986). However, the existence of sylvatic populations has not been well investigated in Mexico, and few studies have found reservoir populations of sylvatic bugs (Rojas et al. 1989; Dominguez Vasquez et al. 1990; Galaviz-Silva and Arredondo Cantu 1992; Jaime-Andrade et al. 1997; Bautista et al. 1999). In Nayarit state, eight species of triatomine have been reported, including three species in the Phyllosoma complex: Triatoma longipennis (Usinger), T. mazzottii (Burmeister), and T. picturata (Usinger). However, the epidemiological importance of these species has not been well investigated (Sil1 Centro Universitario de Ciencias de la Salud, AP 2Ð136, Universidad de Guadalajara, Jalisco, Mexico. 2 Instituto de Investigaciones Biomédicas, UNAM, AP 70228, CP 04510, Mexico DF. 3 Institut de Recherche pour le Développement (IRD), UR 008, Pathogénie des Trypanosomatidae, 911 Av. Agropolis, BP 5045, 34032 Montpellier Cedex 1. veira 1993). Herein, we describe an epidemiological situation where sylvatic and peridomestic triatomine populations cohabit adjacent habitats within a rural community. Materials and Methods Between February 1999 and January 2000, the community of Carrillo Puerto and its surroundings were surveyed for the presence of triatomine bugs. This community is located in the state of Nayarit, Mexico, 12.6 km south of Compostela (21⬚ 08⬘ N, 104⬚ 50⬘ W) within a semiarid region, annual rainfall averaging 1,336 mm, with a dry season between October and June, and a annual mean temperature of 20.4⬚C. The vegetation is deciduous seasonal forest and the main agricultural crop is corn, Zea mays. The community was composed of ⬇250 houses, each surrounded by a small enclosed Þeld where several domestic animals were kept (peridomestic habitat). In February 1999, bugs were collected manually during the day with the aid of ßashlights in peridomestic (e.g., piles of tiles, Þrewood, inside chicken-houses, near cattle) and domestic (e.g., mattresses, bed frames, posters, and wall clefts) habitats. Each search lasted ⬇0.5 person hours per compound. During June 1999 and January 2000, three sylvatic sites adjoining the community (300 Ð 1,000 m away from human dwellings) were visited and several habitats (hollow trees, burrows, cave, and cliffs) sampled for bugs. In addition, 40 small wirenetting bait-traps covered with double-coated adhesive tape and containing two mice (balb/c adults) were left for one night in 25 different sites, including tree holes, burrows, and hollows within the cave and cliff. One armadillo, Dasypus sp., burrow was excavated and the soil searched for triatomines. Adult 0022-2585/01/0638Ð0640$02.00/0 䉷 2001 Entomological Society of America Downloaded from http://jme.oxfordjournals.org/ by guest on October 28, 2016 ABSTRACT Research on domestic and sylvatic triatomines within the community of Carrillo Puerto and neighboring areas of Nayarit, Mexico, documented that Triatoma longipennis (Usinger) and Triatoma picturata (Usinger) were infected with Trypanosoma cruzi (L.) in both habitats. T. picturata was the predominant species in both habitats. Mouse baited-traps increased the effectiveness of collecting sylvatic triatomines, which were difÞcult to sample by inspecting habitats such as burrows, caves, and cliffs. The colonization of sylvatic and peridomestic habitats by Triatoma, the occurrence of high rates of infection with T. cruzi and the possibility that bugs move between habitats may require modiÞcation of current control strategies in Mexico. September 2001 MAGALLÓN-GASTÉLUM ET AL.: SYLVATIC CYCLE OF CHAGAS DISEASE IN MEXICO Table 1. Distribution of triatomines in domestic and peridomestic habitats at the community of Carrillo Puerto, Nayarit, Mexico Habitat Domestic Species T. longipennis T. picturata T. sp. (instars) Total Peridomestic No. Infected per examined 1 2 0/1 0/1 3 0/2 No. Infected per examined 5 23 93 121 1/5 10/19 58/90 69/114 (60.5%) Results and Discussion Overall, 191 bugs belonging to the genus Triatoma were collected, including Triatoma longipennis (4.2%), T. picturata (28.1%), and T. sp (nymphs, 67.7%). Most specimens (64.9%) were collected within the community; 67 triatomines (35.1%) were captured in sylvan habitats. Triatomines were collected from nine of 23 compounds; 121 specimens were collected from peridomestic habitats and three from domestic habitats inside two different houses (Table 1). Bugs also were collected from four natural habitats (Table 2), including the base of a tree, Ficus insipida (seven bugs), a cave (22 bugs), wild animal burrows (18 bugs), and a cliff face (20 bugs). In sylvatic habitats, ⬇30% of the bugs were collected by mouse-baited traps, 14 adhered to the tape and nine others were found near the traps. Both T. longipennis and T. picturata were found in domestic, peridomestic, and sylvatic habitats. Each sylvatic habitat contained nymphs and therefore should be considered as breeding sites. Nymphs were collected in peridomestic (78.1%) and sylvatic (57.5%) areas, showing the full establishment of bugs within these two areas. However, the distribution of breeding sites of the two species could not be delinTable 2. Distribution of triatomines at sylvatic habitats surrounding the community of Carrillo Puerto, Nayarit, Mexico Species T. longipennis T. picturata T. sp. (instars) Instars Total eated, because the nymphs were morphologically indistinguishable. In contrast, the low number of triatomines found inside houses indicated that this habitat may not be permanently colonized. Occasional movement of triatomines into houses, probably from peridomestic populations, could present a risk for parasite transmission to humans. Overall, 177 fecal specimens from both species were examined for T. cruzi infection (Tables 1 and 2). Both species were infected naturally with ßagellated protozoans, and the infection rate of T. picturata from sylvatic habitats was signiÞcantly greater than the rate from peridomestic habitats (2 ⫽ 4.77, P ⬍ 0.05). Nymphs also showed elevated infection rates. Four parasite strains were isolated from bugs from Carrillo Puerto (1 and 3 collected in sylvatic and peridomestic environments, respectively) and were identiÞed as T. cruzi (Sanchez et al. 1999), conÞrming the circulation of T. cruzi in both peridomestic and sylvatic habitats. Sampling triatomines in natural habitats was facilitated by using small bait-traps, especially in the hollows of cliffs and caves, where half of bugs where collected by traps, as previously done in hollow trees (Noireau et al. 1999). Burrows probably are very important sylvatic habitats, and the sampling of these sites should be extended using bait-traps and by excavation. To our knowledge, this was the Þrst detection of bugs in sylvatic habitats near an infested community in Mexico. The success of the current sylvatic collections of triatomines probably was related with their abundance. Moreover, the presence of T. longipennis and T. picturata in sylvatic and peridomestic habitats allowed us to propose that sylvatic populations could play a signiÞcant role as a reservoir to repopulate peridomestic habitats. Further studies are needed to examine such hypothesis. Genetic markers appeared as the most appropriate tools to identify the two species using speciÞc markers and detect gene ßow between populations as previously done for other triatomines (Dujardin et al. 1987, Pereira et al. 1996, Gorla et al. 1997, Brenière et al. 1998, Garcia et al. 1998, Monteiro et al. 1999). In the future, this approach will be developed for the species of Phyllosoma complex to best examine population movements between peridomestic and sylvatic foci. Stage M F M F 1Ð4 5 Tree No. Cave Infection 1 0/1 2 4 7 0/2 1/4 1/7 M, male; F, female; infection, infected per examine. Burrow No. Infection 1 1 5 5 1/1 0/1 3/3 3/4 4 6 22 2/14 5/6 14/19 Cliff No. Infection No. Infection 4 4/4 7 6 3/3 5/6 9 5 18 2/9 5/5 11/18 1 6 20 0/1 2/6 10/16 Downloaded from http://jme.oxfordjournals.org/ by guest on October 28, 2016 insects were identiÞed using morphological criteria (Lent and Wygodzinsky 1979). Nymphs belonging to the Phyllosoma complex are morphologically identical and therefore these stages were not separated to species. 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