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Gaspe MS, Provecho YM, Piccinali RV, Gürtler RE. Where do these bugs come from? Phenotypic structure of Triatoma infestans populations after control interventions in the Argentine Chaco. Mem Inst Oswaldo Cruz 2015; 110:310-8. [PMID: 25946158 PMCID: PMC4489468 DOI: 10.1590/0074-02760140376] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Accepted: 03/18/2015] [Indexed: 11/22/2022] Open
Abstract
House re-invasion by native triatomines after insecticide-based control campaigns
represents a major threat for Chagas disease vector control. We conducted a
longitudinal intervention study in a rural section (Area III, 407 houses) of Pampa
del Indio, northeastern Argentina, and used wing geometric morphometry to compare
pre-spray and post-spray (re-infestant bugs) Triatoma infestans
populations. The community-wide spraying with pyrethroids reduced the prevalence of
house infestation by T. infestans from 31.9% to < 1% during a
four-year follow-up, unlike our previous studies in the neighbouring Area I. Two
groups of bug collection sites differing in wing shape variables before interventions
(including 221 adults from 11 domiciles) were used as a reference for assigning 44
post-spray adults. Wing shape variables from post-spray, high-density bug colonies
and pre-spray groups were significantly different, suggesting that re-infestant
insects had an external origin. Insects from one house differed strongly in wing
shape variables from all other specimens. A further comparison between insects from
both areas supported the existence of independent re-infestation processes within the
same district. These results point to local heterogeneities in house re-infestation
dynamics and emphasise the need to expand the geographic coverage of vector
surveillance and control operations to the affected region.
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Fernández MDP, Cecere MC, Lanati LA, Lauricella MA, Schijman AG, Gürtler RE, Cardinal MV. Geographic variation of Trypanosoma cruzi discrete typing units from Triatoma infestans at different spatial scales. Acta Trop 2014; 140:10-8. [PMID: 25090650 DOI: 10.1016/j.actatropica.2014.07.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Revised: 07/07/2014] [Accepted: 07/23/2014] [Indexed: 10/25/2022]
Abstract
We assessed the diversity and distribution of Trypanosoma cruzi discrete typing units (DTU) in Triatoma infestans populations and its association with local vector-borne transmission levels at various geographic scales. At a local scale, we found high predominance (92.4%) of TcVI over TcV in 68 microscope-positive T. infestans collected in rural communities in Santiago del Estero province in northern Argentina. TcV was more often found in communities with higher house infestation prevalence compatible with active vector-borne transmission. Humans and dogs were the main bloodmeal sources of the TcV- and TcVI-infected bugs. At a broader scale, the greatest variation in DTU diversity was found within the Argentine Chaco (227 microscope-positive bugs), mainly related to differences in equitability between TcVI and TcV among study areas. At a country-wide level, a meta-analysis of published data revealed clear geographic variations in the distribution of DTUs across countries. A correspondence analysis showed that DTU distributions in domestic T. infestans were more similar within Argentina (dominated by TcVI) and within Bolivia (where TcI and TcV had similar relative frequencies), whereas large heterogeneity was found within Chile. DTU diversity was lower in the western Argentine Chaco region and Paraguay (D=0.14-0.22) than in the eastern Argentine Chaco, Bolivia and Chile (D=0.20-0.68). Simultaneous DTU identifications of T. cruzi-infected hosts and triatomines across areas differing in epidemiological status are needed to shed new light on the structure and dynamics of parasite transmission cycles.
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Enriquez GF, Bua J, Orozco MM, Wirth S, Schijman AG, Gürtler RE, Cardinal MV. High levels of Trypanosoma cruzi DNA determined by qPCR and infectiousness to Triatoma infestans support dogs and cats are major sources of parasites for domestic transmission. INFECTION GENETICS AND EVOLUTION 2014; 25:36-43. [PMID: 24732410 DOI: 10.1016/j.meegid.2014.04.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2014] [Revised: 03/31/2014] [Accepted: 04/03/2014] [Indexed: 12/29/2022]
Abstract
The competence of reservoir hosts of vector-borne pathogens is directly linked to its capacity to infect the vector. Domestic dogs and cats are major domestic reservoir hosts of Trypanosoma cruzi, and exhibit a much higher infectiousness to triatomines than seropositive humans. We quantified the concentration of T. cruzi DNA in the peripheral blood of naturally-infected dogs and cats (a surrogate of intensity of parasitemia), and evaluated its association with infectiousness to the vector in a high-risk area of the Argentinean Chaco. To measure infectiousness, 44 infected dogs and 15 infected cats were each exposed to xenodiagnosis with 10-20 uninfected, laboratory-reared Triatoma infestans that blood-fed to repletion and were later individually examined for infection by optical microscopy. Parasite DNA concentration (expressed as equivalent amounts of parasite DNA per mL, Pe/mL) was estimated by real-time PCR amplification of the nuclear satellite DNA. Infectiousness increased steeply with parasite DNA concentration both in dogs and cats. Neither the median parasite load nor the mean infectiousness differed significantly between dogs (8.1Pe/mL and 48%) and cats (9.7Pe/mL and 44%), respectively. The infectiousness of dogs was positively and significantly associated with parasite load and an index of the host's body condition, but not with dog's age, parasite discrete typing unit and exposure to infected bugs in a random-effects multiple logistic regression model. Real-time PCR was more sensitive and less time-consuming than xenodiagnosis, and in conjunction with the body condition index, may be used to identify highly infectious hosts and implement novel control strategies.
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Enriquez GF, Cardinal MV, Orozco MM, Lanati L, Schijman AG, Gürtler RE. Discrete typing units of Trypanosoma cruzi identified in rural dogs and cats in the humid Argentinean Chaco. Parasitology 2013; 140:303-8. [PMID: 23058180 PMCID: PMC3721149 DOI: 10.1017/s003118201200159x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The discrete typing units (DTUs) of Trypanosoma cruzi that infect domestic dogs and cats have rarely been studied. With this purpose we conducted a cross-sectional xenodiagnostic survey of dog and cat populations residing in 2 infested rural villages in Pampa del Indio, in the humid Argentine Chaco. Parasites were isolated by culture from 44 dogs and 12 cats with a positive xenodiagnosis. DTUs were identified from parasite culture samples using a strategy based on multiple polymerase-chain reactions. TcVI was identified in 37 of 44 dogs and in 10 of 12 cats, whereas TcV was identified in 5 dogs and in 2 cats -a new finding for cats. No mixed infections were detected. The occurrence of 2 dogs infected with TcIII -classically found in armadillos- suggests a probable link with the local sylvatic transmission cycle involving Dasypus novemcinctus armadillos and a potential risk of human infection with TcIII. Our study reinforces the importance of dogs and cats as domestic reservoir hosts and sources of various DTUs infecting humans, and suggests a link between dogs and the sylvatic transmission cycle of TcIII.
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Garelli FM, Espinosa MO, Gürtler RE. Processes affecting Aedes aegypti (Diptera: Culicidae) infestation and abundance: inference through statistical modeling and risk maps in northern Argentina. JOURNAL OF MEDICAL ENTOMOLOGY 2012; 49:722-730. [PMID: 22679882 DOI: 10.1603/me11156] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Understanding the processes that affect Aedes aegypti (L.) (Diptera: Culicidae) may serve as a starting point to create and/or improve vector control strategies. For this purpose, we performed statistical modeling of three entomological surveys conducted in Clorinda City, northern Argentina. Previous 'basic' models of presence or absence of larvae and/or pupae (infestation) and the number of pupae in infested containers (productivity), mainly based on physical characteristics of containers, were expanded to include variables selected a priori reflecting water use practices, vector-related context factors, the history of chemical control, and climate. Model selection was performed using Akaike's Information Criterion. In total, 5,431 water-holding containers were inspected and 12,369 Ae. aegypti pupae collected from 963 positive containers. Large tanks were the most productive container type. Variables reflecting every putative process considered, except for history of chemical control, were selected in the best models obtained for infestation and productivity. The associations found were very strong, particularly in the case of infestation. Water use practices and vector-related context factors were the most important ones, as evidenced by their impact on Akaike's Information Criterion scores of the infestation model. Risk maps based on empirical data and model predictions showed a heterogeneous distribution of entomological risk. An integrated vector control strategy is recommended, aiming at community participation for healthier water use practices and targeting large tanks for key elements such as lid status, water addition frequency and water use.
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Piccinali RV, Marcet PL, Ceballos LA, Kitron U, Gürtler RE, Dotson EM. Genetic variability, phylogenetic relationships and gene flow in Triatoma infestans dark morphs from the Argentinean Chaco. INFECTION, GENETICS AND EVOLUTION : JOURNAL OF MOLECULAR EPIDEMIOLOGY AND EVOLUTIONARY GENETICS IN INFECTIOUS DISEASES 2011; 11:895-903. [PMID: 21352954 PMCID: PMC3104122 DOI: 10.1016/j.meegid.2011.02.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2010] [Revised: 02/10/2011] [Accepted: 02/15/2011] [Indexed: 11/18/2022]
Abstract
The recent discovery of sylvatic populations of Triatoma infestans outside the Andean Valleys of Bolivia prompted an evolutionary question about the putative ancestral area of origin and dispersal of the species, and an epidemiological question regarding the possible role of these sylvatic populations in the recolonization process of insecticide-treated houses. The finding of a population of sylvatic melanic T. infestans (dark morphs) in the Argentinean dry Chaco at 7 km from a peridomestic bug population of typical coloration gave us the opportunity to test both questions simultaneously by employing phylogenetic and population genetic approaches. For this purpose we analyzed sylvatic and peridomestic bugs using sequence-based mitochondrial and nuclear markers (mtCOI and ITS-1) and microsatellites. Sylvatic bugs were confirmed to be T. infestans and not hybrids, and showed high levels of genetic variability and departures from neutral expectations for mtCOI variation. New ITS-1 and mtCOI haplotypes were recorded, as well as haplotypes shared with peridomestic and/or domestic bugs from previous records. The peridomestic population was invariant for ITS-1 and mtCOI, but showed variability for microsatellites and signatures of a population bottleneck, probably due to a limited number of founders. Phylogenetic analyses were consistent with the presence of ancestral haplotypes in sylvatic bugs. According to F-statistics and assignment methods there was a significant differentiation between sylvatic and peridomestic bugs and gene flow was low and asymmetric, with more bugs moving from the peridomicile to the sylvatic environment. These results support the hypothesis of the Chaco region as the area of origin of T. infestans, and a limited role of sylvatic melanic T. infestans in peridomestic infestation in the Argentinean Chaco.
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Tomassone L, Nuñez P, Ceballos LA, Gürtler RE, Kitron U, Farber M. Detection of "Candidatus Rickettsia sp. strain Argentina"and Rickettsia bellii in Amblyomma ticks (Acari: Ixodidae) from Northern Argentina. EXPERIMENTAL & APPLIED ACAROLOGY 2010; 52:93-100. [PMID: 20186466 PMCID: PMC3072707 DOI: 10.1007/s10493-010-9339-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Accepted: 01/30/2010] [Indexed: 05/28/2023]
Abstract
Ixodid ticks were collected from vegetation and from humans, wild and domestic mammals in a rural area in the semi-arid Argentine Chaco in late spring 2006 to evaluate their potential role as vectors of Spotted Fever Group (SFG) rickettsiae. A total of 233 adult ticks, identified as Amblyomma parvum, Amblyomma tigrinum and Amblyomma pseudoconcolor, was examined for Rickettsia spp. We identified an SFG rickettsia of unknown pathogenicity, "Candidatus Rickettsia sp. strain Argentina", in A. parvum and A. pseudoconcolor by PCR assays targeting gltA, ompA, ompB and 17-kDa outer membrane antigen rickettsial genes. Rickettsia bellii was detected in a host-seeking male of A. tigrinum. Amblyomma parvum is widespread in the study area and is a potential threat to human health.
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Piccinali RV, Marcet PL, Noireau F, Kitron U, Gürtler RE, Dotson EM. Molecular population genetics and phylogeography of the Chagas disease vector Triatoma infestans in South America. JOURNAL OF MEDICAL ENTOMOLOGY 2009; 46:796-809. [PMID: 19645282 PMCID: PMC2777637 DOI: 10.1603/033.046.0410] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Knowledge of the genetic variability, population structure, and evolutionary history of Triatoma infestans may be useful for developing rational vector control strategies. A 661-bp fragment of the mitochondrial gene cytochrome oxidase I (COI) was sequenced and analyzed in bugs from Argentina, Uruguay, Peru, and Bolivia, including peridomestic, domestic, Andean, and Chaco sylvatic bugs. A total of 48 polymorphic sites among 37 haplotypes were described. Nucleotide variation fluctuated among samples, with the highest nucleotide diversity observed in seven Argentinean provinces. Within this group, some populations showed patterns of variability compatible with population expansions and/or fine-scale population structure, whereas others suggested population bottlenecks and/or population admixture processes. A maximum parsimony analysis of the haplotypes showed the presence of a Bolivian/Peruvian and an Argentinean/Uruguayan clade. Bolivian sequences were further divided in Chaco sylvatic and Andean domestic and sylvatic. Two different nested clades were found within the Argentinean/Uruguayan cluster. Analysis of molecular variance (AMOVA) and K(ST)* analysis supported a strong population structure in Argentina, where genetic differentiation was correlated with geographic distance. Departures from neutrality expectations and a nested cladistic analysis suggest a recent population expansion of T. infestans in Argentina, followed by restricted gene flow and patterns of isolation by distance. This expansion could have taken place as a two-wave process, as was shown by the phylogenetic analysis and signatures of population admixture in the southern most Argentinean populations.
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Vazquez-Prokopec GM, Cecere MC, Kitron U, Gürtler RE. Environmental and demographic factors determining the spatial distribution of Triatoma guasayana in peridomestic and semi-sylvatic habitats of rural northwestern Argentina. MEDICAL AND VETERINARY ENTOMOLOGY 2008; 22:273-282. [PMID: 18816276 DOI: 10.1111/j.1365-2915.2008.00746.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Triatoma guasayana (Wygodzinsky & Abalos), a sylvatic vector of Chagas' disease, occurs in natural and peridomestic habitats of the dry Chaco region of Argentina, Bolivia and Paraguay. Ten-year retrospective spatial analyses of peridomestic T. guasayana abundance in the rural community of Amamá were expanded to the neighbouring community of Trinidad in northwestern Argentina. The distribution of T. guasayana in domiciles, peridomiciles (storerooms, chicken coops and corrals) and natural habitats (bromeliads, dry cacti and logs) around houses (i.e. 'semi-sylvatic' habitats) was analysed. The distribution of the 316 T. guasayana specimens collected in domestic and peridomestic sites during 1993-2002 was significantly clustered in both communities. Searches confirmed that the spatial distribution of semi-sylvatic and peridomestic T. guasayana was determined by the joint effects of the local abundance of goats and the density of semi-sylvatic habitats. The integration of detailed entomological and demographic longitudinal data with geographic information system data, high-resolution satellite imagery, appropriate spatial and temporal analyses and field observations allowed us to infer the underlying processes determining the distribution of T. guasayana in rural communities. This approach may be applied to other sylvatic and peridomestic vectors of Chagas' disease in order to identify high-risk areas for targeted control or environmental management.
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Gürtler RE, Cecere MC, Lauricella MA, Cardinal MV, Kitron U, Cohen JE. Domestic dogs and cats as sources of Trypanosoma cruzi infection in rural northwestern Argentina. Parasitology 2006; 134:69-82. [PMID: 17032467 PMCID: PMC2669415 DOI: 10.1017/s0031182006001259] [Citation(s) in RCA: 174] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2005] [Revised: 04/07/2006] [Accepted: 05/24/2006] [Indexed: 11/06/2022]
Abstract
The reservoir capacity of domestic cats and dogs for Trypanosoma cruzi infection and the host-feeding patterns of domestic Triatoma infestans were assessed longitudinally in 2 infested rural villages in north-western Argentina. A total of 86 dogs and 38 cats was repeatedly examined for T. cruzi infection by serology and/or xenodiagnosis. The composite prevalence of infection in dogs (60%), but not in cats, increased significantly with age and with the domiciliary density of infected T. infestans. Dogs and cats had similarly high forces of infection, prevalence of infectious hosts (41-42%), and infectiousness to bugs at a wide range of infected bug densities. The infectiousness to bugs of seropositive dogs declined significantly with increasing dog age and was highly aggregated. Individual dog infectiousness to bugs was significantly autocorrelated over time. Domestic T. infestans fed on dogs showed higher infection prevalence (49%) than those fed on cats (39%), humans (38%) or chickens (29%) among 1085 bugs examined. The basic reproduction number of T. cruzi in dogs was at least 8.2. Both cats and dogs are epidemiologically important sources of infection for bugs and householders, dogs nearly 3 times more than cats.
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Vazquez-Prokopec GM, Ceballos LA, Marcet PL, Cecere MC, Cardinal MV, Kitron U, Gürtler RE. Seasonal variations in active dispersal of natural populations of Triatoma infestans in rural north-western Argentina. MEDICAL AND VETERINARY ENTOMOLOGY 2006; 20:273-9. [PMID: 17044877 PMCID: PMC1894892 DOI: 10.1111/j.1365-2915.2006.00637.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The flight dispersal of Triatoma infestans Klug (Hemiptera: Reduviidae) is one of the main mechanisms determining community re-infestation after control interventions. An empirical model of flight initiation coupled with data from a longitudinal study predicted that the flight dispersal of T. infestans would peak in summer. To test this prediction, longitudinal light trap collections were conducted during 3-8 nights in March (late summer), July (winter) and November (spring) 2003, and in March 2004 in a rural community in north-west Argentina. Following each light-trapping collection date, all peridomestic sites around light traps were inspected to assess the relative abundance and nutritional status of T. infestans at each site. A total of 21 adult and five nymph T. infestans, six Triatoma guasayana Wygodzinsky & Abalos, and nine Triatoma garciabesi Carcavallo et al. were collected in 96 light-trapping nights, whereas 696 T. infestans were collected from the peridomestic sites that surrounded the light traps. The arrival of T. infestans in the light traps occurred in 64% of catch stations and peaked in the summer surveys (10-14 bugs) compared with spring and winter surveys. When winds were < 5 km/h, the arrival of adult T. infestans at the light traps was significantly associated with maximum temperature and relative humidity. This is the first field report of seasonal variations in the flight dispersal activity of T. infestans.
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Schijman AG, Lauricella MA, Marcet PL, Duffy T, Cardinal MV, Bisio M, Levin MJ, Kitron U, Gürtler RE. Differential detection of Blastocrithidia triatomae and Trypanosoma cruzi by amplification of 24salpha ribosomal RNA genes in faeces of sylvatic triatomine species from rural northwestern Argentina. Acta Trop 2006; 99:50-4. [PMID: 16887092 DOI: 10.1016/j.actatropica.2006.06.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2005] [Revised: 06/27/2006] [Accepted: 06/28/2006] [Indexed: 10/24/2022]
Abstract
Flagellates indistinguishable from Trypanosoma cruzi were detected by microscopy in faecal samples of 2/110 Triatoma guasayana and 2/283 Triatoma garciabesi captured in a rural area of northwestern Argentina. Inoculation of faecal homogenates to mice followed by xenodiagnosis, haemoculture, histopathology and culture from cardiac homogenates, and PCR based on T. cruzi minicircle and nuclear sequences failed to detect T. cruzi infection, pointing to another trypanosomatidean. A PCR strategy targeted to the D7 domain of 24salpha ribosomal DNA genes amplified a 250 bp sequence from one T. guasayana and one T. garciabesi faecal lysate. Sequence analysis revealed 100% identity with 24salpha rDNA amplicons from Blastocrithidia triatomae obtained from faeces of reared Triatoma infestans bugs. Phylogenetic analysis clustered this sequence with C. fasciculata and L. major, separated from the Trypanosoma branch (bootstrap: 968/1000), in concordance with a Neighbour-joining dendrogram based on 18s rDNA sequences. This PCR procedure provides a rapid sensitive tool for differential diagnosis of morphologically similar trypanosomatids in field surveys of Chagas disease vectors and laboratory-reared triatomines used for xenodiagnosis.
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Ceballos LA, Cardinal MV, Vazquez-Prokopec GM, Lauricella MA, Orozco MM, Cortinas R, Schijman AG, Levin MJ, Kitron U, Gürtler RE. Long-term reduction of Trypanosoma cruzi infection in sylvatic mammals following deforestation and sustained vector surveillance in northwestern Argentina. Acta Trop 2006; 98:286-96. [PMID: 16839513 PMCID: PMC1853287 DOI: 10.1016/j.actatropica.2006.06.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2006] [Revised: 05/05/2006] [Accepted: 06/01/2006] [Indexed: 11/20/2022]
Abstract
Long-term variations in the dynamics and intensity of sylvatic transmission of Trypanosoma cruzi were investigated around eight rural villages in the semiarid Argentine Chaco in 2002-2004 and compared to data collected locally in 1984-1991. Of 501 wild mammals from 13 identified species examined by xenodiagnosis, only 3 (7.9%) of 38 Didelphis albiventris opossums and 1 (1.1%) of 91 Conepatus chinga skunks were infected by T. cruzi. The period prevalence in opossums was four-fold lower in 2002-2004 than in 1984-1991 (32-36%). The infection prevalence of skunks also decreased five-fold from 4.1-5.6% in 1984-1991 to 1.1% in 2002-2004. Infection in opossums increased with age and from summer to spring in both study periods. The force of infection per 100 opossum-months after weaning declined more than six-fold from 8.2 in 1988-1991 to 1.2 in 2002-2004. Opossums were mainly infected by T. cruzi lineage I and secondarily by lineage IId in 1984-1991, and only by T. cruzi I in 2002-2004; skunks were infected by T. cruzi IId in 1984-1991 and by IIc in 2002-2004. The striking decline of T. cruzi infection in opossums and skunks occurred in parallel to community-wide insecticide spraying followed by selective sprays leading to very low densities of infected Triatoma infestans in domestic and peridomestic habitats since 1992; to massive deforestation around one of the villages or selective extraction of older trees, and apparent reductions in opossum abundance jointly with increases in foxes and skunks. These factors may underlie the dramatic decrease of T. cruzi infection in wild reservoir hosts.
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Marcet PL, Duffy T, Cardinal MV, Burgos JM, Lauricella MA, Levin MJ, Kitron U, Gürtler RE, Schijman AG. PCR-based screening and lineage identification of Trypanosoma cruzi directly from faecal samples of triatomine bugs from northwestern Argentina. Parasitology 2006; 132:57-65. [PMID: 16393354 PMCID: PMC1853270 DOI: 10.1017/s0031182005008772] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2005] [Revised: 07/11/2005] [Accepted: 07/12/2005] [Indexed: 11/06/2022]
Abstract
This study applied improved DNA extraction and polymerase chain reaction strategies for screening and identification of Trypanosoma cruzi lineages directly from faeces of triatomines collected in a well-defined rural area in northwestern Argentina. Amplification of the variable regions of the kinetoplastid minicircle genome (kDNA-PCR) was performed in faecal lysates from 33 microscope (MO)-positive and 93 MO-negative Triatoma infestans, 2 MO-positive and 38 MO-negative Triatoma guasayana and 2 MO-positive and 73 MO-negative Triatoma garciabesi. kDNA-PCR detected T. cruzi in 91% MO-positive and 7.5% MO-negative T. infestans, which were confirmed by amplification of the minicircle conserved region. In contrast, kDNA-PCR was negative in all faecal samples from the other triatomine species. A panel of PCR-based genomic markers (intergenic region of spliced-leader DNA, 24Salpha and 18S rRNA genes and A10 sequence) was implemented to identify the parasite lineages directly in DNA lysates from faeces and culture isolates from 28 infected specimens. Two were found to be infected with TCI, 24 with TCIIe, 1 with TCIId and 1 revealed a mixed TCI+TCII infection in the faecal sample whose corresponding culture only showed TCII, providing evidence of the advantages of direct typing of biological samples. This study provides an upgrade in the current diagnosis and lineage identification of T. cruzi in field-collected triatomines and shows T. cruziII strains as predominant in the region.
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Marcet PL, Lehmann T, Groner G, Gürtler RE, Kitron U, Dotson EM. Identification and characterization of microsatellite markers in the Chagas disease vector Triatoma infestans (Heteroptera: Reduviidae). INFECTION, GENETICS AND EVOLUTION : JOURNAL OF MOLECULAR EPIDEMIOLOGY AND EVOLUTIONARY GENETICS IN INFECTIOUS DISEASES 2006; 6:32-7. [PMID: 16376838 PMCID: PMC1351232 DOI: 10.1016/j.meegid.2005.01.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2004] [Revised: 01/04/2005] [Accepted: 01/08/2005] [Indexed: 11/27/2022]
Abstract
Triatoma infestans, the main vector of Chagas disease in the southern cone countries, is the principal target of a regional elimination program. A better understanding of its dispersal, sources of reinfestation, and insecticide resistance is key to an effective control program. To address such problems, we identified and characterized 13 microsatellite loci of T. infestans. For each locus, primer sequences and PCR conditions are presented. Allele variability and frequency were analyzed in 59 T. infestans specimens from different rural communities in northwestern Argentina; nine loci were considered suitable for population genetic studies. Departure from Hardy-Weinberg equilibrium was detected in 10/13 loci with F(IS) values ranging from 0.04 to 0.91, indicating heterozygote deficit and a possible grade of sub-structure in the sample analyzed. Presence of null alleles in some loci cannot be discarded. The present work provides a promising tool to develop a population genetic study of natural populations of T. infestans in tandem with field studies and analyses of bug dispersal and the reinfestation process.
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Ceballos LA, Vazquez-Prokopec GM, Cecere MC, Marcet PL, Gürtler RE. Feeding rates, nutritional status and flight dispersal potential of peridomestic populations of Triatomainfestans in rural northwestern Argentina. Acta Trop 2005; 95:149-59. [PMID: 15993834 DOI: 10.1016/j.actatropica.2005.05.010] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2005] [Accepted: 05/31/2005] [Indexed: 11/25/2022]
Abstract
Triatoma infestans, the main vector of Chagas disease in Southern Cone countries, frequently infests peridomestic structures housing domestic animals. A total of 814 T. infestans collected from 35 different peridomestic sites in rural northwestern Argentina over 1-4 consecutive seasons was examined for recent blood meals and nutritional status. Bugs from goat or pig corrals had lower qualitative nutritional status and mean weight to length ratios (W/L) than those captured in chicken coops. Males systematically had lower qualitative nutritional status and W/L than females. Using logistic multiple regression, the daily feeding rates of T. infestans were significantly associated with season and stage but not ecotope, whereas the proportion of well-fed bugs varied significantly with all three factors. The seasonal trends in feeding rates and nutritional status were consistent with the local availability and breeding timing of domestic animals. The observed data fed into an empirical model predicted that the probability of flight initiation would peak in summer from pig or goat corrals, not chicken coops, and be insignificant in all ecotopes in spring and fall. Male T. infestans outnumbered females as potential fliers. This is the first study conducted in well-defined habitat units that shows significant heterogeneities in the feeding rates and nutritional status of triatomine populations linked to host demographics and management, and how these affect flight dispersal potential over seasons. Peridomestic bug populations are of great relevance as a source of domestic reinfestation and for the elimination of T. infestans.
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Vazquez-Prokopec GM, Ceballos LA, Cecere MC, Gürtler RE. Seasonal variations of microclimatic conditions in domestic and peridomestic habitats of Triatoma infestans in rural northwest Argentina. Acta Trop 2002; 84:229-38. [PMID: 12443801 DOI: 10.1016/s0001-706x(02)00204-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Our objectives were to describe and compare the seasonal variations in microclimatic conditions in domestic and peridomestic ecotopes infested by Triatoma infestans, the main vector of Chagas disease, in rural northwestern Argentina. Using data loggers for 4-7 consecutive days in October 2000, February, May and August 2001, microsite (interior of thatched roofs) and ambient temperatures or relative humidity (RH) were recorded simultaneously and compared with an external reference. The damping effects on microsite temperature and ambient RH increased successively from the goat corral to the chicken coop or pig corral, to the storeroom or human habitation. In the interior of the thatched roofs of the habitation and storeroom, average external minima were increased by +5.0 to +5.6 degrees C in all seasons, and average external maxima were decreased by -4.3 to -5.6 degrees C in October-May and -10.6 degrees C in August. On average, the human habitation damped extreme temperatures by 8 degrees C over a wider range than previously reported. The interior of the thatched roofs of the pig corral and chicken coop exerted intermediate damping effects that varied over seasons, whereas the goat corral's thatch showed little or no damping effects at all. The adobe-and-thatch habitation and storeroom presented nearly optimal and more suitable conditions for T. infestans populations than other open structures housing animals. Global climate changes are expected to affect peridomestic populations of T. infestans much more than domestic bug populations, provided other local conditions are held constant. Heterogeneous habitat conditions are expected to affect T. infestans population parameters, dispersal, control and infection with Trypanosoma cruzi.
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Cecere MC, Gürtler RE, Canale DM, Chuit R, Cohen JE. Effects of partial housing improvement and insecticide spraying on the reinfestation dynamics of Triatoma infestans in rural northwestern Argentina. Acta Trop 2002; 84:101-16. [PMID: 12429427 DOI: 10.1016/s0001-706x(02)00183-3] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The long-term effects on domiciliary reinfestation by Triatoma infestans of smoothing the plaster of indoor walls prior to insecticide application (in Amamá village) relative to only insecticide application (in Trinidad-Mercedes villages) were evaluated in rural northwestern Argentina from 1992 to 1997. All domestic and peridomestic areas of each house were sprayed with 2.5% suspension concentrate deltamethrin at 25 mg/m(2) in October 1992, and infestations were assessed by various methods every 6 months. Domiciliary infestation decreased from 72-88% in 1992 to 6-17% in late 1995, to increase moderately thereafter without returning to baseline rates. Peridomestic sites were the first in becoming reinfested, and reached more abundant T. infestans populations than domiciliary areas. Domiciliary infestation rates and bug abundances were not significantly different between communities during surveillance. Domiciliary infestation rates in well-plastered houses were very low (5-9%) and approximately stable until 1996, but in houses with regular or bad plaster they consistently increased from 5 to 19-21% in both communities. Logistic multiple regression analysis showed that the likelihood of domestic infestation assessed through householders' collections was significantly and positively associated with the occurrence of an infested peridomestic site in the respective house, the occurrence of high-density domestic infestations before interventions, and well-plastered walls in 1996. Combining insecticide spraying and partial improvement of walls controlled domestic infestations and transmission of Trypanosoma cruzi effectively, but was not sufficient to eliminate T. infestans from the study area or increase the effectiveness of careful chemical control.
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Abstract
American trypanosomiasis, or Chagas disease, caused by the protozoan parasite Trypanosoma cruzi and transmitted by blood-feeding triatomine bugs, is a chronic, frequently fatal infection that is common in Latin America. Neither adequate drugs nor a vaccine is available. A mathematical model calibrated to detailed household data from three villages in northwest Argentina shows that householders could greatly reduce the risk of human infection by excluding domestic animals, especially infected dogs, from bedrooms; removing potential refuges for bugs from walls and ceilings; and using domestically applied insecticides. Low-cost, locally practicable environmental management combined with intermittent use of insecticides can sustainably control transmission of T. cruzi to humans in rural Argentina and probably elsewhere.
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Gürtler RE, Prokopec GM, Ceballos LA, Petersen CL, Salomon OD. Comparison between two artificial shelter units and timed manual collections for detecting peridomestic Triatoma infestans (Hemiptera: Reduviidae) in rural northwestern Argentina. JOURNAL OF MEDICAL ENTOMOLOGY 2001; 38:429-436. [PMID: 11372969 DOI: 10.1603/0022-2585-38.3.429] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A new artificial shelter unit was compared with segments of bamboo cane lined with pleated filter paper for detecting peridomestic Triatoma infestans Klug at Amamá and nearby rural villages in northwestern Argentina. The new shelter unit consisted of a black plastic, wide-mouthed jar with a screw cap on the top, and a removable central structure made of pleated corrugated paper. In devices exposed from February to December 1999 at 24 sites positive for T. infestans by timed manual collections with an irritant in April 1999, the cumulative percentage of sites with any sign of infestation detected by the shelter unit increased from 71% after 2 mo to 96% after 10 mo, whereas bamboo cane units concurrently detected only 12-42% of the sites. Sensitivity increased with time of exposure and the abundance of T. infestans per site. In 19 sites negative for T. infestans by inspection, shelters increasingly detected infestation at 16-63% of sites after 10 mo, whereas the bamboo canes only detected one infestation. Shelter units inspected three times over an 11-mo period were significantly more sensitive than a single manual search with an irritant performed in March 2000. Our study provided conclusive field evidence that the shelter unit was more sensitive for detecting peridomestic T. infestans than were timed manual searches, the standard reference method, or bamboo cane units. Rapid timed searches by skilled bug collectors during the early surveillance phase overlooked many peridomestic populations that, in the absence of control, inevitably would increase in abundance and repopulate treated areas.
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Petersen RM, Gürtler RE, Cecere MC, Rubel DN, Lauricella MA, Hansen D, Carlomagno MA. Association between nutritional indicators and infectivity of dogs seroreactive for Trypanosoma cruzi in a rural area of northwestern Argentina. Parasitol Res 2001; 87:208-14. [PMID: 11293568 DOI: 10.1007/s004360000324] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The association between the nutritional state of mongrel dogs naturally infected with Trypanosoma cruzi and their infectivity to Triatoma infestans bugs and immune response to Trypanosoma cruzi were studied in the rural village of Amamá, northwestern Argentina. All of the 97 evaluated dogs were classified into one of three categories of external clinical aspect (ECA) based on the degree of muscle development, external evidence of bone structures, state of the hair of the coat, existence of fatty deposits, and facial expression. ECA was significantly associated with two nutritional indicators, hematocrit and skin-fold thickness, but not with total serum proteins. For all dogs, hematocrit was significantly correlated with skin-fold thickness. The 2-year survival probability decreased significantly from 60.7% for dogs with good ECA to 45.9% and 31.2% for those with regular and bad ECA, respectively. The age-adjusted relative odds of infection for Triatoma infestans xeno-diagnosis nymphs that fed once on a dog seroreactive for Trypanosoma cruzi decreased significantly as ECA improved, when tested by multiple logistic regression analysis. A delayed hypersensitivity reaction was observed in all of the seroreactive dogs with good ECA but only in 45-50% of those with regular or bad ECA. Dogs with bad ECA had a 2.6 and 6.3 times greater probability of infecting triatomines after a single full blood meal than dogs with regular or good ECA, respectively. Our study shows that the reservoir competence of dogs for Trypanosoma cruzi was associated with ECA, which is a surrogate and valid index of nutritional state.
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Gürtler RE, Oneto ML, Cecere MC, Castañera MB, Canale DM. A simple method to identify triatomine (Hemiptera: Reduviidae) feces in sensing devices used in vector surveillance programs. JOURNAL OF MEDICAL ENTOMOLOGY 2001; 38:147-152. [PMID: 11296815 DOI: 10.1603/0022-2585-38.2.147] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We successfully applied the phenolphthalin (Kastle-Meyer) test used in forensic chemistry to distinguish between feces from triatomines and other domestic arthropods in sensing devices used for vector surveillance. All black or dark brown, but not white or yellow, fecal smears from laboratory-reared or field-collected Triatoma infestans Klug, Triatoma guasayana Wydgozinsky & Abalos, Triatoma sordida Ståhl (recently revalidated as Triatoma garciabesi Carcavallo, Cichero, Martínez, Prosen & Ronderos) tested positive, whereas dejecta from cockroaches and spiders, crickets, beetles, predatory bugs, and domestic flies tested negative. Black or dark brown dejecta from female Aedes aegypti L. and Cimex lectularius L. bedbugs also tested positive. In sellsing devices installed in bedrooms of 11 houses in Amamá, rural northwestern Argentina, where neither cimicid bedbugs nor argasid ticks had been found over the years, only 62% of the black or dark brown fecal smears attributed to triatomines by a skilled observer tested phenolphthalin-positive. After insecticidal spraying, when bedroom areas were not colonized by triatomines, only 33-40% of the black or dark brown fecal smears in sensor boxes attributed to triatomines by another skilled observer tested phenolphthalin-positive. Eleven (79%) ofthe 14 houses with dubious or nontypical triatomine feces tested phenolphthalin-positive at least once during 1993-1995. Our study introduces a low-cost, simple and effective procedure for the identification of triatomine feces. The test, as a helpful adjunct to sensing devices used in triatomine surveillance, will aid in the accurate detection of infestations and the determination of the need for insecticide application.
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Canale DM, Cecere MC, Chuit R, Gürtler RE. Peridomestic distribution of Triatoma garciabesi and Triatoma guasayana in north-west Argentina. MEDICAL AND VETERINARY ENTOMOLOGY 2000; 14:383-390. [PMID: 11129702 DOI: 10.1046/j.1365-2915.2000.00254.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The Reduviid bugs Triatoma garciabesi Carcavallo et al. (Hemiptera: Reduviidae: Triatominae), previously known as T. sordida Ståhl in the semi-arid chaco region, and T. guasayana Wygodzinsky & Abalos, vectors of Trypanosoma cruzi Chagas (Kinetoplastida: Trypanosomatidae), were found to occupy wide but different ranges of ecotopes in the peridomestic environment. At Amamá and nearby rural villages in north-western Argentina, a combined total of 1233 specimens were collected from 325/2314 (14%) sites surveyed at 6-monthly intervals from November 1994 to November 1996. Triatoma garciabesi and T. guasayana displayed a significantly different distribution among peridomestic ecotopes. Triatoma garciabesi predominated over T. guasayana in the prevalence of infested sites, the number of colonies and the number of bugs collected. For T. garciabesi, the predominant ecotopes most likely to yield T. garciabesi repeatedly were the rugged bark of Prosopis alba or P. nigra (Fabaceae) trees, where chickens roosted, and chicken coops. For T. guasayana the main ecotopes were goat or sheep corrals, piled materials and orchard fences. Triatoma garciabesi and T. guasayana were collected concurrently from the same site on 9/2314 (0.4%) occasions, and on different dates at the same site on 12 (0.5%) occasions. The observed low frequency of mixed populations (< 1%) was not significantly different from that expected from a hypothesis of independence. Triatoma garciabesi clearly outnumbered T. guasayana in four of the nine mixed populations, none of which persisted as such. Neither T. garciabesi nor T. guasayana colonized human habitations, even in the absence of T. infestans (formerly the predominant domestic vector of T. cruzi in this area), a situation that apparently has not changed in the last 50 years in northern Argentina.
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Blanco SB, Segura EL, Cura EN, Chuit R, Tulián L, Flores I, Garbarino G, Villalonga JF, Gürtler RE. Congenital transmission of Trypanosoma cruzi: an operational outline for detecting and treating infected infants in north-western Argentina. Trop Med Int Health 2000; 5:293-301. [PMID: 10810029 DOI: 10.1046/j.1365-3156.2000.00548.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We designed a set of procedures for first-line local health services to detect and treat the congenital transmission of Trypanosoma cruzi at a province-wide scale, and field-tested the programme in the province of Tucumán, northwestern Argentina, from 1992 to 1994. The programme consists of routine screening of pregnant women for seroreactivity to T. cruzi, serological and parasitological follow-up of the newborn at least twice during the first year of age, treatment of the infected infants, and evaluation of the outcome. 927 (5.5%) of 16 842 pregnant women were seroreactive to T. cruzi by indirect haemagglutination assay and ELISA. Twenty-one (6.7%) of 315 newborns to seroreactive mothers were diagnosed as infected with T. cruzi parasites microhaematocrit concentration before 30 days of age. Five newborns who initially tested negative had a T. cruzi infection detected by microhaematocrit and/or serological techniques at 3 or 6 months of age. Thus, congenital infection was diagnosed in 26 (7.1%) infants born to seroreactive women and residing in houses free of triatomine bugs. Four of 6 infants born to seroreactive mothers died during the first year of age and had some evidence of T. cruzi infection; one of the deaths was attributed to T. cruzi based on clinical evidence. After specific treatment with nifurtimox or benznidazole, 30 of 32 infants remained parasitologically and serologically negative. This study shows the feasibility of controlling the incidence of congenitally acquired T. cruzi infections at a province-wide scale by means of a specific screening programme at first-line health services level.
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Gürtler RE. [Control campaigns against Triatoma infestans in a rural community of northwestern Argentina]. Medicina (B Aires) 2000; 59 Suppl 2:47-54. [PMID: 10668242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023] Open
Abstract
Control campaigns against Triatoma infestans, the principal vector of Trypanosoma cruzi, have relied on the application of residual insecticides and have regarded the system as homogeneous. Reinfestation generally starts in peri-domestic residual foci or in preexisting foci that escaped spraying for diverse reasons. From these foci T. infestans adults actively invade other sites, or they are transported passively within objects or goods from infested communities. In the absence of additional spraying of insecticides after the attack phase, domiciliary reinfestation expanded exponentially to return to pre-spraying levels in 3-4 years in Amamá, Santiago del Estero. However, the rate of recovery of T. infestans abundance was much lower than that predicted by a simple mathematical model or in experimental field studies. Reinfestation did not progress homogeneously within the village. Two longitudinal studies in Santiago del Estero revealed that the presence of T. infestans-infested peri-domestic sites increased the risk of domiciliary reinfestation. "Key" sites where reinfestation started early were goat or sheep corrals, pig corrals, chicken houses, and store-rooms. Peri-domestic reinfestation is likely the result of multiple factors, such as insecticide breakdown by climatic agents, and the greater surface and availability of refuge and hosts in peri-domestic rather than domiciliary sites. Such environmental heterogeneity generates insecticidal effects heterogeneity and increases the probability of persistence of T. infestans even under control pressures. Several studies showed that sustained surveillance after the attack phase decreased sharply the domiciliary colonization by T. infestans and the percentage of bugs infected with T. cruzi, and the local incidence of infected children. The sustained elimination of T. infestans demands a scientific approach that is not only centered in insecticide use but that also includes the environment and house-holders in their specific social and political scenario.
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