Acta Tropica 140 (2014) 124–129 Contents lists available at ScienceDirect Acta Tropica jo urnal homepage: www.elsevier.com/locate/actatropica Biological cycle and preliminary data on vectorial competence of Triatoma boliviana in laboratory conditions a,1 a a,b,∗ Pamela Durán , Edda Sinani˜ , Stéphanie Depickère a Laboratorio Entomología Médica, INLASA, Rafael Zubieta No. 1889, Miraflores, La Paz, Bolivia b Institut de Recherche pour le Développement (IRD), c/o Embajada Francia, CP 9214 La Paz, Bolivia a r a t i b s c t l e i n f o r a c t Article history: With more than 140 potential vectors of Chagas disease, it is important to better know the biology Received 22 April 2014 and especially the vectorial capacity of the triatomine species which live in the surroundings of human Received in revised form 4 August 2014 dwellings. In Bolivia where 17 triatomine species are reported, the principal vector is Triatoma infestans. Accepted 11 August 2014 In some valleys of the department of La Paz where T. infestans is not present, a new species (Triatoma Available online 20 August 2014 boliviana) was described in 2007. This species lives in a sylvatic environment not far away from the dwellings, and occasionally some individuals are found inside the houses. This study was carried out to Keywords: describe the biological cycle of T. boliviana and to determine its vectorial competence. The development Chagas disease of a cohort of 95 nymphs of first instar (N1) was followed through nymphal instars and adult stage until Vectorial competence ◦ death in laboratory (22 C). They were fed twice a week on an immobilized mouse. The median egg-to- Triatoma boliviana Life cycle adult development time was 8.4 months. The mortality by nymphal instar was lower than 7% except for Laboratory rearing N1 (67%) and N5 (18%). All nymph instars needed at least two feedings to molt (until six feedings for N5). Defecation index The differentiation of a nymph into a female or a male could not be detected until the fifth instar for which the food intake was greater for a nymph developing into a female. Adults fed about once a week. The adult life span was around 400 days. The fecundity was 4.2 eggs/female/week, with a hatching rate of 50% and a hatching time of 39 days. In the same conditions, T. infestans showed a similar fecundity but a greater ◦ hatching rate and hatching time. A trial for rearing the adults at a higher temperature (26 C) showed a drastic fall in the fecundity and in the hatching rate. The vectorial competence was analyzed for fifth instars and adults by three parameters: the ability to feed on human beings, the capacity to be infected by T. cruzi and the postfeeding defecation delay. Results showed a relatively high vectorial competence: (1) insects fed easily on the tested human being; (2) 100% of the specimens became infected by T. cruzi just by one infected meal; and (3) although the adults defecated after a median postfeeding delay greater than that of T. infestans, results on N5 suggest that they could be as good vectors as T. infestans males. © 2014 Elsevier B.V. All rights reserved. 1. Introduction currently recognized species of Triatominae have been shown to be naturally or experimentally infected with T. cruzi, and all are sus- Chagas disease is caused by the parasite Trypanosoma cruzi pected to have this capacity. Nevertheless, only 5% of the triatomine which is mainly transmitted to humans by blood-sucking tri- species is considered to have a great epidemiological importance atomine bugs (Hemiptera: Reduviidae). Over half of the 141 in the Chagas disease transmission (Telleria and Tibayrenc, 2010). This can be explained by the vectorial competence which varies according to the bug species. The heamatophagous diet and the ∗ capacity to be infected by T. cruzi are not sufficient to determine a Corresponding author at: Institut de Recherche pour le Développement (IRD), species as a vector; other conditions mainly related to the anthro- IRD c/o Embajada Francia, La Paz, Plurinational State of Bolivia. Tel.: +591 2 222 52 80. pophyly degree and the defecation velocity are required (Dujardin E-mail addresses: [email protected] (P. Durán), et al., 2002; Klotz et al., 2009; Telleria and Tibayrenc, 2010). [email protected] (E. Sinani),˜ [email protected] (S. Depickère). In the Southern Cone of South America, the main vector 1 Present address: Instituto de Investigación en Salud y Desarrollo (IINSAD), Triatoma infestans is a domiciled species. In Bolivia which is a high- Calle Claudio Sanjinez, Edificio IBBA, Complejo Hospitalario de Miraflores, La endemic country for Chagas disease, this vector is present across Paz, Bolivia—Cátedra de Parasitología, Departamento de Parasitología, Facultad de Medicina, Universidad Mayor de San Andrés, Av. Saavedra 2246, La Paz, Bolivia. 60% of the territory (Petherick, 2010). Sixteen other species of http://dx.doi.org/10.1016/j.actatropica.2014.08.014 0001-706X/© 2014 Elsevier B.V. All rights reserved. P. Durán et al. / Acta Tropica 140 (2014) 124–129 125 Triatominae have been described until now in this country feeding/weight just after the last molting. The feeding speed was (Martínez et al., 2007). Some of them have a role in the transmis- measured as the amount of ingested blood (mg) per minute. To sion of Chagas disease to human population (Rhodnius stali: Justi determine the frequency of feeding, the percentage of positive feed- et al., 2010; Triatoma sordida: Noireau et al., 1997). Some other ing was calculated. The latter is defined as the number of effective species do not have this vector role although they live near human feeding divided by the number of possibilities to feed and expressed beings (Eratyrus mucronatus: Depickère et al., 2012; Panstrongylus in percentage. Finally the defecation time (defined as the time rufotuberculatus: Depickère et al., 2011). between the end of feeding and the defecation act) was determined. Triatoma boliviana is a new species of Triatominae described in This time was equal to 0 if the bug defecated during feeding. Two 2007 in Bolivia (Martínez et al., 2007). This bug was collected in defecation indexes (ADIt and PDIt), based on the defecation index narrow valleys of the Department of La Paz, Provinces of Munecas˜ (DI) calculated by Zeledón et al. (1977), were defined in order to and Larecaja (2100–2600 m asl). It was captured in a sylvatic habi- compare the stages and species: tat in the surroundings of the dwellings, more precisely in piles t Nt of stones delimiting the fields in this region. From time to time ADI = t=0 × D,¯ t N some specimens are also collected inside or around the houses. Until now, there is no evidence of Chagas disease transmission to t human population in the region. Nevertheless, it is really important Nt t=0 PDIt = × D,¯ to well understand the biological cycle of the Triatominae species N − Nno living near the human dwellings. Therefore, the objectives of this where Nt is the number of bugs which defecated at time t; N is the study were to determine the life-cycle of T. boliviana under labo- total number of individuals; Nno is the number of insects which ratory conditions and to analyze some parameters of its vectorial have not defecated during the observation time; and D¯ is the aver- competence as regards the transmission of T. cruzi. age number of defecation per insect which have defecated during the observation time. 2. Material and methods Data on feeding and defecation behavior were compared with those obtained on T. infestans (6 pairs of adults) using the same The colony of T. boliviana was collected in 2007 in the Province of protocol and conditions of rearing. In view of the usual condition Munecas,˜ La Paz, Bolivia. From four communities visited during the ◦ of rearing of T. infestans in our laboratory (26 ± 2 C, 55 ± 20% RH, field work, 917 T. boliviana specimens were found in three villages. 12:12 dark:light regime), 6 pairs of adults of T. infestans and 6 Eight bugs were captured in the dwellings (one in the intradomi- pairs of adults of T. boliviana were also reared in these conditions cile and seven in the peridomicile at 2 m of the house). The rest to observe the influence of the temperature on the fecundity and of the bugs were captured in piles of stones and stone walls (0.3 mortality. to 2 m high) delimiting the fields around the dwellings, generally Finally, the capacities of T. boliviana to feed on human being and 20–300 m distant from the houses (Martínez et al., 2007). Insects to be infected by T. cruzi were investigated in order to complete the were reared in laboratory in La Paz under similar conditions to ◦ data about the vectorial competence of this species: those of their natural environment: 22 ± 2 C; 60 ± 10% RH; 12:12 light:dark regime in a laboratory oven (Firlabo Meditest 600). - 10 N5 and 10 adults (5 females and 5 males) were starved for 30 days and then placed in two different small plastic containers 2.1. Life-cycle covered on the top with a piece of mosquito net. These contain- ers were placed directly in contact with the human being skin of The study began with 95 nymphs of the first instar (N1) from a consenting person of our team, allowing the bite of the bugs. the first generation (F1). The development of this cohort was fol- The insects’ weight before and after feeding was recorded and lowed through nymphal instars and adult stage until death.