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    Polymerase chain reaction amplification with primers Tc83F and Tc83R of a 280-basepair (bp) DNA fragment from feces of triatomine bugs. Lane 1, Rhodnius prolixus from house 11; lane 2, Panstrongylus geniculatus from house 11; lane 3, R. prolixus from house 1; lane 4, degraded product; lane 5, purified DNA of Trypanosoma cruzi obtained from R. prolixus from house 11.

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    Random amplified polymorphic DNA profiles obtained with primer A2 of Trypanosoma cruzi stocks isolated from the intestine of Rhodnius prolixus. Lane M, 1-kb molecular mass marker; lane 1, R. prolixus from house 11; lane 2, R. prolixus from house 1; lane Z3 = reference strain CAN II; lane Z1 = reference strain WA250 cl10B; lane Z2 = reference strain Esmeraldo cl3. Values on the left are in basepairs.

  • 1

    Dias JC, 2000. Chagas disease control and the natural history of human Chagas disease: a possible interaction? Mem Inst Oswaldo Cruz 95 (Suppl II):14–22.

    • Search Google Scholar
    • Export Citation
  • 2

    Feliciangeli MD, Campbell-Lendrum D, Martinez C, Gonzalez D, Coleman P, Davies C, 2003. Chagas disease control in Venezuela: lessons for the Andean region and beyond. Trends Parasitol 19 :44–49.

    • Search Google Scholar
    • Export Citation
  • 3

    Reyes-Lugo M, Rodriguez-Acosta A, 2000. Domiciliation of the sylvatic Chagas disease vector Panstrongylus geniculatus Latreille, 1811 (Triatominae: Reduviidae) in Venezuela. Trans R Soc Trop Med Hyg 94 :508.

    • Search Google Scholar
    • Export Citation
  • 4

    Soto Vivas AA, Barazarte H, Molina de Fernández D, 2001. Primer registro de Eratyrus mucronatus (Hemiptera: Reduviidae) en el ambiente domiciliario en Venezuela. Entomotropica 16 :215–217.

    • Search Google Scholar
    • Export Citation
  • 5

    Schofield CJ, 1994. Triatominae: Biología y Control. West Sussex, United Kingdom: Eurocommunica Publications.

  • 6

    Anonymous, 1999. Recommendations from a Satellite Meeting. International Symposium to Commemorate the 90th Anniversary of the Discovery of Chagas Disease. April 11–16, 1999, Rio de Janeiro, Brazil. Mem Inst Oswaldo Cruz 94: 429–432.

    • Search Google Scholar
    • Export Citation
  • 7

    Miles MA, Povoa MM, Prata A, Cedillos RA, de Souza AA, Macedo V, 1981. Do radically dissimilar Trypanosoma cruzi strains (zymodemes) cause Venezuelan and Brazilian forms of Chagas’ disease? Lancet i :1338–1340.

    • Search Google Scholar
    • Export Citation
  • 8

    Mendonça MBA, Neheme NS, Santos SS, Cupolillo E, Vargas N, Junqueira A, Naiff RD, Barrett TV, Coura JR, Zingales B, Fernandes O, 2002. Two main clusters within Trypanosoma cruzi zymodeme 3 are defined by distinct regions of the ribosomal RNA cistron. Parasitology 124 :177–184.

    • Search Google Scholar
    • Export Citation
  • 9

    Gaunt M, Miles MA, 2000. The ecotopes and evolution of triatomine bugs (Triatominae) and their associated trypanosomes. Mem Inst Oswaldo Cruz 95 :557–565.

    • Search Google Scholar
    • Export Citation
  • 10

    Feliciangeli MD, Dujardin JP, Bastrenta B, Mazzarri M, Villegas J, Flores M, Muñoz M, 2002. Is Rhodnius robustus (Hemiptera: Reduviidae) responsible for Chagas disease transmission in western Venezuela? Trop Med Int Health 7 :180–187.

    • Search Google Scholar
    • Export Citation
  • 11

    Ewel JJ, Madriz A, 1968. Zonas de Vida de Venezuela. Memoria Explicativa Sobre el Mapa Ecológico. Caracas: Editorial Sucre.

  • 12

    OCEI, 1990. XII Censo General de la Población y Vivienda. Nomenclador de Centros Poblados. Caracas: OCEI

  • 13

    Miles MA, 1993. Culturing and biological cloning of Trypanosoma cruzi. Hyde JE, ed. Methods in Molecular Biology, Protocols in Molecular Parasitology. Totowa, NJ: Humana Press Inc., 15–28.

  • 14

    Carrasco HJ, Frame IA, Valente SA, Miles MA. Genetic exchange as possible source of genomic diversity in sylvatic populations of Trypanosoma cruzi. Am J Trop Med Hyg 54 :418–424.

    • Search Google Scholar
    • Export Citation
  • 15

    Gomez B, Sanchez E, Feliciangeli MD, 1998. Man-vector contact of phlebotomine sandflies (Diptera: Psychodidae) in north-central Venezuela, as assessed by bloodmeal identification using a dot-ELISA. J Am Mosq Control Assoc. 14 :28–32.

    • Search Google Scholar
    • Export Citation
  • 16

    Agrela I, Sánchez E, Gomez B, Feliciangeli MD, 2002. Feeding behavior of Lutzomyia pseudolongipalpis (Diptera: Psychodidae), a putative vector of visceral leishmaniasis in Venezuela. J Med Entomol 39 :440–445.

    • Search Google Scholar
    • Export Citation
  • 17

    Camargo ME, 1966. Fluorescent antibody test for the diagnosis of American trypanosomiasis. Technical modification employing preserved culture forms of Trypanosoma cruzi in a slide test. Rev Inst Med Trop Sao Paulo 8: 227–234.

    • Search Google Scholar
    • Export Citation
  • 18

    Kagan IG. 1970. Serologic diagnosis of parasitic diseases. N Engl J Med 282 :685–686.

  • 19

    Maekelt GA, 1960. Die komplement bindungs reaction der Chagas krankheit. Z Trop Med Parasitol 21 :39–44.

  • 20

    Deane MP, Kenzi HL, Jansen AM, 1986. Double development cycle of Trypanosoma cruzi in the opossum. Parasitol Today 2 :146–147.

  • 21

    Lent H, Wygodzinsky P, 1979. Revision of the Triatominae (Hemiptera, Reduviidae), and their significance as vectors of Chagas’disease. Bull Am Mus Nat Hist 163 :123–520.

    • Search Google Scholar
    • Export Citation
  • 22

    Povoa MM, de Souza AA, Naif RD, Arias JR, Naif MF, Biancardi CB, Miles MA, 1984. Chagas disease in the Amazon Basin. IV. Host records of Trypanosoma cruzi zymodemes in the States of Amazonia and Rondonia. Brazil. Ann Trop Med Parasitol 78 :479–487.

    • Search Google Scholar
    • Export Citation
  • 23

    Valente VC, Valente SAS, Noireau F, Carrasco HJ, Miles MA, 1998. Chagas disease in the Amazon basin: association of Panstrongylus geniculatus (Hemiptera: Reduviidae) with domestic pigs. J Med Entomol 35 :99–103.

    • Search Google Scholar
    • Export Citation
  • 24

    Lotka AJ, 1925. Elements of Physical Biology. Baltimore: Williams & Wilkins.

  • 25

    Volterra V, 1926. Variations and fluctuations of the number of individuals in animal species living together. Chapman RN, ed. Animal Ecology. New York: McGraw-Hill, 409–448.

  • 26

    Gause GF, 1934. The Struggle for Existence. New York: Hafner.

  • 27

    Bar ME, Oscherov EB, Dambrovsky MP, Porcel EA, Alvarez BM, 1994. Interaction between populations of Triatoma infestans and Triatoma sordida. Rev Saude Publica 28 :59–68.

    • Search Google Scholar
    • Export Citation
  • 28

    Noireau F, Brenière SF, Cardozo L, Bosseno MF, Vargas F, Peredo C, Medinacelli M, 1996. Current spread of Triatoma infestans at the expense of Triatoma sordida in Bolivia. Mem Inst Oswaldo Cruz 91 :271–272.

    • Search Google Scholar
    • Export Citation

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MIXED DOMESTIC INFESTATION BY RHODNIUS PROLIXUS STÄL, 1859 AND PANSTRONGYLUS GENICULATUS LATREILLE, 1811, VECTOR INCRIMINATION, AND SEROPREVALENCE FOR TRYPANOSOMA CRUZI AMONG INHABITANTS IN EL GUAMITO, LARA STATE, VENEZUELA

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  • 1 Facultad de Ciencias de la Salud, BIOMED, Universidad de Carabobo, Maracay, Venezuela; Facultad de Medicina, Instituto de Medicina Tropical, Universidad Central de Venezuela, Caracas, Venezuela; London School of Hygiene and Tropical Medicine, London, United Kingdom; Laboratorio de Chagas, Dirección General de Salud Ambiental y Contraloría Sanitaria, Ministry of Health and Social Development, Maracay, Venezuela

Mixed infestation of nymphs and adults of Rhodnius prolixus Stäl, 1859 and Panstrongylus geniculatus Latreille, 1811 was detected in 3 (15%) of 20 dwellings in El Guamito, an endemic focus of Chagas disease in Lara State, Venezuela. In one of the houses, both species were positive for Trypanosoma cruzi: 14.3% (R. prolixus) and 20% (P. geniculatus ). The overall infection rate in 143 of 352 R. prolixus was 16.1%. Parasites isolated from R. prolixus were identified as T. cruzi I by random amplified polymorphic DNA analysis. Dot–enzyme-linked immunosorbent assays of 36 R. prolixus showed that 58.3% of the R. prolixus had fed on humans. The gut contents of one fifth-instar nymph of P. geniculatus that was positive for T. cruzi also reacted with anti-human serum. A questionnaire was used to gather data on the demographic and socioeconomic characteristics of the population. An indirect immunofluorescent test, an indirect hemaglutination test, and an ELISA were used to detect the presence of antibodies against T. cruzi in 84 of 86 inhabitants and in 15.5% of people more than 20 years old. The relative risk (RR) of infection was greater in men than in women (RR = 1.61, 95% confidence interval = 0.54–4.80). Of the people more than 15 years old, 36.6% had no formal education. All respondents recognized triatomine bugs, but they did not relate them to Chagas disease transmission. A total of 85.7% of the houses were “ranchos” suitable for the colonization of triatomine bugs. The possible domiciliation of P. geniculatus and the implications of competition with R. prolixus for resources are discussed. Since there is no clear separation of food sources, abiotic factors such as microclimatic variation within houses may be critical to predict the outcome of the process of competition and potential domestication of this generally sylvatic species.

INTRODUCTION

Human Chagas disease is caused by the parasitic protozoan Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae) that is mainly transmitted through fecal contamination by triatomine bugs (Hemiptera: Reduviidae). It is endemic in all Latin American countries (20°N–45°S), where approximately 80–100 million people are at risk and 11–12 million people are estimated to be infected.1

In Venezuela, a national Chagas Disease Control Program was undertaken in the 1960s with the aim of interrupting intradomestic transmission by vector control using residual spraying of dieldrin indoors and hexachlorocyclohexane outdoors and replacing the mud-walled, palm-roofed huts with cement block dwellings with zinc roofs on a large scale (National Rural Housing Program) to deprive the domestic Rhodnius prolixus of resting and breeding sites. During the 1980s, diendrin was replaced with fenitrothion in most states and the routine screening of all public hospital blood banks for Trypanosoma cruzi was instituted using enzyme-linked immunosorbent assays (ELISAs). Efforts to improve health education were also implemented. These interventions have reduced the annual incidence of T. cruzi infection from approximately 10 per 1,000 inhabitants in the 1950s to 1 per 1,000 in the 1980s. This has decreased a huge burden of disease among the rural poor. However, analysis of epidemiologic indicators of the last 10 years has shown that transmission has not been interrupted and may now be increasing.2

Although the presence of R. prolixus in human dwellings remains the primary risk factor for maintenance of the domestic transmission, invasion by wild triatomine species has recently been documented in Venezuela, indicating possible domestic adaptation.3,4 These findings deserve attention since sylvatic bugs often show high infection rates5 and may establish new domestic cycles of T. cruzi.

At present, T. cruzi is divided into T. cruzi I and T. cruzi II6, which broadly correspond to the principal zymodemes (Z1 and Z2);7 a third zymodeme group Z3, also known as T. cruzi IIa, is considered by some to be more closely related to T. cruzi I.8 These three zymodeme groups have been associated with different vectors and reservoirs.9 The identification of the parasite strain circulated by sylvatic bugs entering houses is therefore of extreme interest in terms of acquiring a better knowledge of the etiology and epidemiology of Chagas disease. Miles and others,7 using isoenzyme analysis, reported the presence of T. cruzi Z1 and Z3 in Venezuela. However, there is little new information available on this matter,10 although a phenotypic and genotypic characterization of a number of isolates will be published elsewhere (Carrasco H and others, unpublished data).

In this paper, we report mixed domestic infestation by R. prolixus and Panstrongylus geniculatus. The latter species appears to be in the process of domiciliation in El Guamito, Lara Sate, Venezuela. The food sources of the bugs, the identification of T. cruzi isolated from both species, and a serologic survey among the inhabitants are also reported.

MATERIAL AND METHODS

Study area.

The research was carried out in El Guamito (09°47′00″N, 69°20′14″W) in the Municipality of Iribarren, Lara State, Venezuela, a wet pre-mountain forest with an average annual precipitation between 1,200 and 2,200 mm and an annual temperature range of 18–24°C.11 El Guamito is a small village of 25 houses12 scattered from 429–1043 m, surrounded by a large variety of subsistence agriculture (coffee, banana, avocado, corn, beans) (75%), with secondary forest (10%) and primary forest (15%). Most of the houses are made of a structure of sticks plastered by a mixture of mud and straw, which is called “bahareque” in the colloquial language, with thatched or zinc roofs. Very few were constructed of sun-baked mud bricks, which are called “adobe” houses.

Entomologic study.

Searching for triatomine bugs and natural infection with trypanosomatids.

In response to the reported presence of Chagas disease vectors, an initial visit to El Guamito was carried out in November 2000. House searches were conducted using torches and fine forceps in cracks in walls, pictures on the walls, beds, and household goods in 10 houses. The finding in two houses of mixed infestations by R. prolixus and P. geniculatus led to subsequent visits for more extensive collections. The triatomine bugs were transported to the laboratory, where feces or gut contents were examined for the presence of trypanosomatids. The first group of positive fecal samples were fixed in methanol for five minutes, dried, and stained with 10% Giemsa. Additionally, a small amount of each sample was kept in lysis buffer (10 mM Tris, pH 8, 10 mM EDTA, 1 μg/μL of proteinase K) for a polymerase chain reaction (PCR). Inoculations and cultures were attempted as described later in this report.

Identification of T. cruzi.

Parasites from R. prolixus were obtained by pulling out the digestive tract, mixing in two or three drops of physiologic saline, inoculating intraperitoneally into laboratory mice and subsequent blood culture, and/or direct culture of bug feces in diphasic blood agar medium. After isolation, the parasites were grown at 26°C in RPMI 1640 medium (GIBCO-BRL, Paisley, Scotland) supplemented according to the method of Miles.13 Genomic DNA was isolated and purified using the Nucleon DNA Extraction Kit (Amersham Pharmacia Biotech, Ltd., Bucks, United Kingdom) following the manufacturer’s instructions. The resulting DNA was suspended in 100 μL of TE buffer (10mM Tris-HCl, pH 7.2, 1mM EDTA). The isolates were identified and typed to T. cruzi group using the random amplified polymorphic DNA (RAPD) technique as reported by Carrasco and others.14 Alternatively, parasites were detected after extraction of genomic DNA directly from P. geniculatus feces using the Wizard Genomic DNA Purification System (Promega, Madison, WI), followed by amplification of a 280-basepair product, with specific primers derived from the sequence of a 480-bp fragment obtained by RAPD analysis with primer A2. This sequence has been shown to be species specific for T. cruzi; no amplification product is obtained with DNA of different Kinetoplastidae, including T. rangeli and Leishmania spp. The sequences of the 480-bp T. cruzi species-specific fragment and the amplification primers will be published elsewhere (Carrasco H and others, unpublished data). Parasite DNA was amplified in an MJ thermal reactor (PTC200; MJ Research, Inc., Waltham, MA). Amplified DNA products were analyzed by electrophoresis on agarose gels, stained with ethidium bromide, and photographed on an ultraviolet transilluminator.

Blood meal identification by dot-ELISA.

Blood meal identification was carried out on triatomine bugs positive for T. cruzi (n = 17) and on a random sample of negative bugs (n = 20). The technique used was previously standardized for identification of blood meals in phlebotomine sand flies.15,16 We used IgG peroxidase antiserum conjugates against humans, mice, and some domestic animals (dog, chicken, pig, cow, and horse) (Sigma, St. Louis, MO). Serum dilutions in (phosphate-buffered saline [PBS] 1:100) from selected hosts were used as positive controls. Triatomine blood meal samples on filter paper were eluted individually in 100 μL of PBS (pH 7.4) at overnight at 4°C. After 24 hours, 5 μl of each eluate was transferred to small piece of nitrocellulose membrane in flexible polyvinyl chloride plates and incubated for one hour at 37°C. The plates were blocked with 150 μL of PBS, 1% bovine serum albumin for 30 minutes at room temperature and then washed three times with PBS, 0.05% Tween 20. The anti-IgG host-specific peroxidase conjugate was diluted in PBS, 0.05% Tween 20 according to previously determined ratios, mixed with 50 μL of each heterologus serum to reduce cross-reactivity and to enhance specificity, incubated for one hour at 37°C, and washed three times with PBS, Tween 20. Peroxidase substrate (4-cloro-naphthol) was added and incubated in the dark for 30 minutes. The reaction was stopped by washing with distilled water. The samples were considered positive if defined blue-purple spots developed on an antigen dot.

Epidemiologic study.

With the aim of evaluating the prevalence of antibodies to T. cruzi among the population at risk, in May 2001 families of 21 houses gave informed consent for inclusion in a study according to a protocol reviewed and approved by the Committee of Bioethics of the Instituto de Altos Estudios Dr. Arnoldo Gabaldon of the Ministry of Health and Social Development. A questionnaire on demographic data (age, sex, occupation, education, time in the locality, knowledge of Chagas disease) structure of the houses, and peridomestic habitat was completed with the help of the householders. Finger prick blood samples were collected on Whatman (Clifton, NJ) no. 1 filter paper to screen for antibodies to T. cruzi. Samples were kept dry in plastic bags and transported to the Laboratorio de Chagas, Dirección de Salud Ambiental y Contraloría Sanitaria, Ministry of Health and Social Development (Maracay, Venezuela).

Three serologic tests were used for detecting antibodies to T. cruzi as routinely applied at national level: 1) an indirect immunofluorescent test (IFAT),17 2) an indirect hemaglutination test (IHT),18 and 3) an ELISA (Code UM 2014; UMELISA Chagas-SUMA, Havana, Cuba). The IHT and ELISA antigens were soluble protein extracts of T. cruzi produced at the Instituto de Medicina Tropical, Universidad Central de Venezuela (Caracas, Venezuela) according to the method of Maekelt.19 Cut-off points for each test were IFAT: 1:32, IHT: 1:32, and ELISA: 0.030 optical density values. Samples were considered positive when a positive reaction was obtained in two of the three tests.

RESULTS

Entomologic and parasitologic results.

Among 20 houses inspected for triatomine bugs, 14 were found positive for R. prolixus (infestation index = 70%). Table 1 shows the number of specimens collected, instars, and results of examination for T. cruzi. A total of 352 R. prolixus were collected, of which 143 were examined. Twenty-three were found positive for T. cruzi (infection index = 16.08%). A total of 79.8% of the bugs (n = 281) were collected in one house (No. 2). Ninety-nine were examined and 15.15% (n = 15) were infected.

Table 2 shows the results of triatomine bugs catches in the three houses where a mixed infestation of two triatomine species was found and their examination for T. cruzi. A total of 36 R. prolixus and 11 P. geniculatus were collected (3.3:1.0). Only one P. geniculatus was positive for T. cruzi.(11.1%), a fifth-instar nymph.

Identification of T. cruzi.

The PCR amplification of a 280-bp nuclear DNA fragment in feces from P. geniculatus indicated the presence of T. cruzi in the intestine of this triatomine bug, as shown in Figure 1. The pattern of bands obtained by RAPD of the parasites isolated from R. prolixus corresponded to T. cruzi I when compared with the TCI (Z1) reference strain WA250 cl10,14 as shown in Figure 2. It is noteworthy that both species of triatomine bugs were found in the same house.

Blood meal identification.

The sample obtained from the stomach of the fifth-instar P. geniculatus that was positive for T. cruzi reacted with the human antiserum. Seventy-five percent of the samples obtained from R. prolixus (n = 27) were reactive and 25% (n = 9) not reactive. Twenty-one blood meals reacted only with human antiserum (58.3%), one with human and dog antisera (2.8%), one with human and mouse antisera (2.8%), and four with chicken antisera (11.1%). Among 15 R. prolixus positive for T. cruzi, 13 (86.7%) had fed on humans.

Demographic and serologic results.

The demographic and socioeconomic indicators showed high levels of poverty in El Guamito where 85.7% of the dwellings were “ranchos” suitable for colonization by triatomine bugs. At the time of the study, 51 men and 35 women lived there, of whom 38.4% were less than 15 years old. A total of 36.6% of the people had no formal education. The most frequent occupations were domestic activities (29.1%), farmers (37.2%), and students (8.1%).

All but two men were screened for antibodies to T. cruzi. The overall seroprevalence was 15.5% (nine men and four women) and all were more than 30 years old. No significant difference by sex was found. However, the relative risk (RR) of infection was greater in men than in women (RR = 1.61, 95% confidence interval = 0.54–4.80). All infected women were housekeepers and all of the men were farmers.

All of the heads of households said that they recognized triatomine bugs; 14 (82.4%) said they had seen them inside houses. Additionally, 10 (58.8%) had seen them in the peridomestic habitats. However, 78.9% said they knew nothing of Chagas disease, although 89.5% recognized the bugs as a problem for their family.

A total of 61.1% of the families had lived in the houses they occupied for more than 10 years. However, the rest were children of older inhabitants who had married and constructed their own houses in the same village. Eight houses had bugs and seropositive occupants, six houses had bugs but no seropositive occupants, three houses had no bugs but seropositive occupants, while three houses had no bugs and no seropositive occupants. Fisher’s exact one-tailed test showed no significant difference among the groups (P = 0.5743).

DISCUSSION

The village of El Guamito in Lara State is a long established focus of Chagas disease in Venezuela, as demonstrated by the distribution of the presence of antibodies to T. cruzi among its inhabitants, which were detected only in adults, the majority of whom had lived all their life in El Guamito. The bias in relative risk towards men could be interpreted as the result of outdoor transmission, probably due to contamination of men with the urine or feces of Didelphis marsupialis,20 natural reservoir of T. cruzi, which are commonly hunted for food. However, because of the maintenance of poor dwelling conditions, which are highly favorable for the presence of R. prolixus, and because of the presence of T. cruzi in these vectors feeding on humans and dogs, recent infections cannot be excluded. The additional presence of P. geniculatus also infected with T. cruzi in a pre-imaginal stage and the fact that it had fed on humans confirms that not only R. prolixus but also P. geniculatus is involved in an active domestic cycle.

The RAPD analysis showed that the triatomine bugs were infected with T. cruzi I (Z1). These results are in agreement with those obtained with many other isolates found circulating in domestic and sylvatic cycles in different localities in Portuguesa State in west-central Venezuela, which were also identified as T. cruzi I.

Panstrongylus geniculatus is a sylvatic triatomine bug widespread in 16 Latin American countries,5 which is commonly associated with the armadillo Dasypus novemcinctus and only occasionally enters houses when attracted by light.21 It has been frequently reported to be infected with T. cruzi, and in Brazil mainly with T. cruzi Z3.22 The potential for domiciliation of P. geniculatus was suggested by Valente and others23 in the Amazon Basin of Brazil, where hundreds of specimens were found infesting pig sties adjacent to human dwellings and specimens were collected from 10 houses, in one of which it repeatedly attacked people. Although no human infections were detected, T. cruzi I (Z1) was isolated from bugs, pigs, and opossums collected in the area. This indicates the need for a program to control Chagas disease in the Amazon Basin. In northcentral Venezuela, 20 specimens of P. geniculatus of different stages were found in a house in Hoyo de la Puerta, Miranda State, associated with Rattus rattus living in a cavity inside the house.3 However, no investigation for T. cruzi infection was done. In both of these cases, no other triatomine species was found associated with P. geniculatus nymphal stages, indicating that P. geniculatus successfully colonized the houses.

The present work in El Guamito, Lara State, Venezuela seems to be the first report of mixed infestation of R. prolixus and P. geniculatus adults and nymphs. Mathematical models, such as the Lotka-Volterra equations,24,25 have been used to hypothesize what would happen when two species live together in the same habitat. It is accepted that competition for food and space would occur, which might give rise to transient coexistence with eventual competitive exclusion to the point of the replacement of one species by the other. The logistic model predicts that competing species can co-exist only if interspecific competition is relatively weak compared with intraspecific competition. The competitive exclusion principle (CEP), as derived by Gause,26 states that two species that occupy the same habitat cannot also occupy the same ecologic niche. Any two species that occupy the same niche will compete with each other to the detriment of one of the species, which will thus be excluded. The CEP assumes a number of conditions that must be met for it to be obtained. Among the most important, 1) the environment must be spatially uniform, 2) the environment must be temporally constant, 3) time must be sufficient to allow exclusion, and 4) species must have the opportunity to compete.

An example of transient co-existence of T. dimidiata and R. ecuadoriensis in Ecuador has been reported (Abad-Franch F, unpublished data). The ability of Triatoma infestans to replace T. sordida in a laboratory experiment27 is supported by observations of the spreading of T. infestans in domestic ecotopes in Bolivia,28 and is evidence of the successful replacement of one triatomine species by another better adapted species after a period of stability of the human population, followed by significant migration. What is the case for R. prolixus and P. geniculatus? Theoretically, it could be argued that they could coexist indefinitely if there is a distinction between their niches, i.e., P. geniculatus exploiting the humid dusty burrow-like areas in the house (perhaps feeding only on domestic animals, e.g., dogs and/or chickens or pigs), leaving R. prolixus to occupy the drier parts and feeding on humans. However, the identification of the blood meal in one P. geniculatus collected in El Guamito indicates that this would be not the situation. Nevertheless, P. geniculatus and R. prolixus have different relative humidity requirements, which are higher for P. geniculatus. This factor may be critical in modulating the outcome of the process of competition between these two species and the domestication of this sylvatic species. In El Guamito, it was observed that the three houses where P. geniculatus was found shared similar features: all were made of adobe bricks rather than “bahareque”, and piles of adobe were found inside and outside the houses.

In conclusion, the follow-up of invasion of houses by P. geniculatus in the field, the study of the association of its presence with the features of the niches occupied, and experimental simulation in the laboratory are necessary to confirm and predict if incipient domiciliation of P. geniculatus may give rise to successful domestic colonization.

Table 1

Rhodnius prolixus collected, examined and positive for Trypanosoma cruzi in 20 houses in El Guamito, Lara State, Venezuela

No. (%) collectedNo. (%) examinedNo. (%) positive for T. cruzi
Males74 (21.0)29 (39.2)5 (17.2)
Females78 (22.2)42 (53.8)8 (19.1)
Instar
    V66 (18.8)26 (39.4)0 (0.0)
    IV62 (17.5)19 (30.6)3 (15.8)
    III57 (16.2)18 (31.6)7 (38.9)
    II14 (3.97)8 (57.4)0 (0.0)
    I1 (0.28)1 (100)0 (0.0)
Total352143 (40.6)23 (16.08)
Table 2

Mixed infestation by Rhodnius prolixus (Rp) and Panstrongylus geniculatus (Pg) in 3 of 20 houses in El Guamito, Lara State, Venezuela*

House no.
51112
RpPgRpPgRpPg
* Values in parentheses are number of bugs dissected. + = no. of bugs positive for Trypanosoma cruzi.
Males5 (2)3 (3)
Females2 (0)1 (1)3 (3)
Instar
    V1 (0)7 (5)3 (2)2 (2)2 (2)
    IV1 (0)2 (0)2 (2)
    III2 (1)3 (3)2 (2)
    II3 (2)1 (1)2 (2)
    I
Total10221 (3+)5 (1+)54
Figure 1.
Figure 1.

Polymerase chain reaction amplification with primers Tc83F and Tc83R of a 280-basepair (bp) DNA fragment from feces of triatomine bugs. Lane 1, Rhodnius prolixus from house 11; lane 2, Panstrongylus geniculatus from house 11; lane 3, R. prolixus from house 1; lane 4, degraded product; lane 5, purified DNA of Trypanosoma cruzi obtained from R. prolixus from house 11.

Citation: The American Journal of Tropical Medicine and Hygiene Am J Trop Med Hyg 71, 4; 10.4269/ajtmh.2004.71.501

Figure 2.
Figure 2.

Random amplified polymorphic DNA profiles obtained with primer A2 of Trypanosoma cruzi stocks isolated from the intestine of Rhodnius prolixus. Lane M, 1-kb molecular mass marker; lane 1, R. prolixus from house 11; lane 2, R. prolixus from house 1; lane Z3 = reference strain CAN II; lane Z1 = reference strain WA250 cl10B; lane Z2 = reference strain Esmeraldo cl3. Values on the left are in basepairs.

Citation: The American Journal of Tropical Medicine and Hygiene Am J Trop Med Hyg 71, 4; 10.4269/ajtmh.2004.71.501

Authors’ addresses: M. Dora Feliciangeli and Benny Suarez, Facultad de Ciencias de la Salud, BIOMED, Universidad de Carabobo, Núcleo Aragua, Apartado 4873, Maracay, Venezuela. Hernán Carrasco and Clara Martínez, Facultad de Medicina, Instituto de Medicina Tropical, Universidad Central de Venezuela, Caracas, Venezuela. James S. Patterson, London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom. Mehudy Medina, Laboratorio de Chagas, Dirección General de Salud Ambiental y Contraloría Sanitaria, Ministry of Health and Social Development, Maracay, Venezuela.

Acknowledgments: We thank Carlos Mendez, Roseliano Visval, and Annhy Torrellas for their technical assistance.

Financial support: This work was supported by the Wellcome Trust (Project no. 062984/Z/00/Z). The Chagas Disease Intervention Activities – European Community, the MCT-FONACIT, S1-98000388, and the CDCH-UCV-09-34-4097-01.

REFERENCES

  • 1

    Dias JC, 2000. Chagas disease control and the natural history of human Chagas disease: a possible interaction? Mem Inst Oswaldo Cruz 95 (Suppl II):14–22.

    • Search Google Scholar
    • Export Citation
  • 2

    Feliciangeli MD, Campbell-Lendrum D, Martinez C, Gonzalez D, Coleman P, Davies C, 2003. Chagas disease control in Venezuela: lessons for the Andean region and beyond. Trends Parasitol 19 :44–49.

    • Search Google Scholar
    • Export Citation
  • 3

    Reyes-Lugo M, Rodriguez-Acosta A, 2000. Domiciliation of the sylvatic Chagas disease vector Panstrongylus geniculatus Latreille, 1811 (Triatominae: Reduviidae) in Venezuela. Trans R Soc Trop Med Hyg 94 :508.

    • Search Google Scholar
    • Export Citation
  • 4

    Soto Vivas AA, Barazarte H, Molina de Fernández D, 2001. Primer registro de Eratyrus mucronatus (Hemiptera: Reduviidae) en el ambiente domiciliario en Venezuela. Entomotropica 16 :215–217.

    • Search Google Scholar
    • Export Citation
  • 5

    Schofield CJ, 1994. Triatominae: Biología y Control. West Sussex, United Kingdom: Eurocommunica Publications.

  • 6

    Anonymous, 1999. Recommendations from a Satellite Meeting. International Symposium to Commemorate the 90th Anniversary of the Discovery of Chagas Disease. April 11–16, 1999, Rio de Janeiro, Brazil. Mem Inst Oswaldo Cruz 94: 429–432.

    • Search Google Scholar
    • Export Citation
  • 7

    Miles MA, Povoa MM, Prata A, Cedillos RA, de Souza AA, Macedo V, 1981. Do radically dissimilar Trypanosoma cruzi strains (zymodemes) cause Venezuelan and Brazilian forms of Chagas’ disease? Lancet i :1338–1340.

    • Search Google Scholar
    • Export Citation
  • 8

    Mendonça MBA, Neheme NS, Santos SS, Cupolillo E, Vargas N, Junqueira A, Naiff RD, Barrett TV, Coura JR, Zingales B, Fernandes O, 2002. Two main clusters within Trypanosoma cruzi zymodeme 3 are defined by distinct regions of the ribosomal RNA cistron. Parasitology 124 :177–184.

    • Search Google Scholar
    • Export Citation
  • 9

    Gaunt M, Miles MA, 2000. The ecotopes and evolution of triatomine bugs (Triatominae) and their associated trypanosomes. Mem Inst Oswaldo Cruz 95 :557–565.

    • Search Google Scholar
    • Export Citation
  • 10

    Feliciangeli MD, Dujardin JP, Bastrenta B, Mazzarri M, Villegas J, Flores M, Muñoz M, 2002. Is Rhodnius robustus (Hemiptera: Reduviidae) responsible for Chagas disease transmission in western Venezuela? Trop Med Int Health 7 :180–187.

    • Search Google Scholar
    • Export Citation
  • 11

    Ewel JJ, Madriz A, 1968. Zonas de Vida de Venezuela. Memoria Explicativa Sobre el Mapa Ecológico. Caracas: Editorial Sucre.

  • 12

    OCEI, 1990. XII Censo General de la Población y Vivienda. Nomenclador de Centros Poblados. Caracas: OCEI

  • 13

    Miles MA, 1993. Culturing and biological cloning of Trypanosoma cruzi. Hyde JE, ed. Methods in Molecular Biology, Protocols in Molecular Parasitology. Totowa, NJ: Humana Press Inc., 15–28.

  • 14

    Carrasco HJ, Frame IA, Valente SA, Miles MA. Genetic exchange as possible source of genomic diversity in sylvatic populations of Trypanosoma cruzi. Am J Trop Med Hyg 54 :418–424.

    • Search Google Scholar
    • Export Citation
  • 15

    Gomez B, Sanchez E, Feliciangeli MD, 1998. Man-vector contact of phlebotomine sandflies (Diptera: Psychodidae) in north-central Venezuela, as assessed by bloodmeal identification using a dot-ELISA. J Am Mosq Control Assoc. 14 :28–32.

    • Search Google Scholar
    • Export Citation
  • 16

    Agrela I, Sánchez E, Gomez B, Feliciangeli MD, 2002. Feeding behavior of Lutzomyia pseudolongipalpis (Diptera: Psychodidae), a putative vector of visceral leishmaniasis in Venezuela. J Med Entomol 39 :440–445.

    • Search Google Scholar
    • Export Citation
  • 17

    Camargo ME, 1966. Fluorescent antibody test for the diagnosis of American trypanosomiasis. Technical modification employing preserved culture forms of Trypanosoma cruzi in a slide test. Rev Inst Med Trop Sao Paulo 8: 227–234.

    • Search Google Scholar
    • Export Citation
  • 18

    Kagan IG. 1970. Serologic diagnosis of parasitic diseases. N Engl J Med 282 :685–686.

  • 19

    Maekelt GA, 1960. Die komplement bindungs reaction der Chagas krankheit. Z Trop Med Parasitol 21 :39–44.

  • 20

    Deane MP, Kenzi HL, Jansen AM, 1986. Double development cycle of Trypanosoma cruzi in the opossum. Parasitol Today 2 :146–147.

  • 21

    Lent H, Wygodzinsky P, 1979. Revision of the Triatominae (Hemiptera, Reduviidae), and their significance as vectors of Chagas’disease. Bull Am Mus Nat Hist 163 :123–520.

    • Search Google Scholar
    • Export Citation
  • 22

    Povoa MM, de Souza AA, Naif RD, Arias JR, Naif MF, Biancardi CB, Miles MA, 1984. Chagas disease in the Amazon Basin. IV. Host records of Trypanosoma cruzi zymodemes in the States of Amazonia and Rondonia. Brazil. Ann Trop Med Parasitol 78 :479–487.

    • Search Google Scholar
    • Export Citation
  • 23

    Valente VC, Valente SAS, Noireau F, Carrasco HJ, Miles MA, 1998. Chagas disease in the Amazon basin: association of Panstrongylus geniculatus (Hemiptera: Reduviidae) with domestic pigs. J Med Entomol 35 :99–103.

    • Search Google Scholar
    • Export Citation
  • 24

    Lotka AJ, 1925. Elements of Physical Biology. Baltimore: Williams & Wilkins.

  • 25

    Volterra V, 1926. Variations and fluctuations of the number of individuals in animal species living together. Chapman RN, ed. Animal Ecology. New York: McGraw-Hill, 409–448.

  • 26

    Gause GF, 1934. The Struggle for Existence. New York: Hafner.

  • 27

    Bar ME, Oscherov EB, Dambrovsky MP, Porcel EA, Alvarez BM, 1994. Interaction between populations of Triatoma infestans and Triatoma sordida. Rev Saude Publica 28 :59–68.

    • Search Google Scholar
    • Export Citation
  • 28

    Noireau F, Brenière SF, Cardozo L, Bosseno MF, Vargas F, Peredo C, Medinacelli M, 1996. Current spread of Triatoma infestans at the expense of Triatoma sordida in Bolivia. Mem Inst Oswaldo Cruz 91 :271–272.

    • Search Google Scholar
    • Export Citation

Author Notes

Reprint requests: M. Dora Feliciangeli, Facultad de Ciencias de la Salud, BIOMED, Universidad de Carabobo, Núcleo Aragua, Apartado 4873, Maracay, Venezuela, Telephone : 58-243-233-5822, Fax: 58-243-242-5333; E-mail: mdora@telcel.net.ve.
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