Download Sylvatic Triatominae of the Phyllosoma Complex

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
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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
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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. Feces from each bug were mixed with phosphate
buffered saline and examined for the presence of
ßagellates.
639
640
JOURNAL OF MEDICAL ENTOMOLOGY
Acknowledgments
We thank the World Health Organization and the Institut
de Recherche pour le Développement (IRD) for Þnancial
support.
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