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Phylogeographic Pattern and Extensive Mitochondrial DNA Divergence Disclose a Species Complex within the Chagas Disease Vector Triatoma dimidiata  [PDF]
Fernando A. Monteiro, Tatiana Peretolchina, Cristiano Lazoski, Kecia Harris, Ellen M. Dotson, Fernando Abad-Franch, Elsa Tamayo, Pamela M. Pennington, Carlota Monroy, Celia Cordon-Rosales, Paz Maria Salazar-Schettino, Andrés Gómez-Palacio, Mario J. Grijalva, Charles B. Beard, Paula L. Marcet
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0070974
Abstract: Background Triatoma dimidiata is among the main vectors of Chagas disease in Latin America. However, and despite important advances, there is no consensus about the taxonomic status of phenotypically divergent T. dimidiata populations, which in most recent papers are regarded as subspecies. Methodology and Findings A total of 126 cyt b sequences (621 bp long) were produced for specimens from across the species range. Forty-seven selected specimens representing the main cyt b clades observed (after a preliminary phylogenetic analysis) were also sequenced for an ND4 fragment (554 bp long) and concatenated with their respective cyt b sequences to produce a combined data set totalling 1175 bp/individual. Bayesian and Maximum-Likelihood phylogenetic analyses of both data sets (cyt b, and cyt b+ND4) disclosed four strongly divergent (all pairwise Kimura 2-parameter distances >0.08), monophyletic groups: Group I occurs from Southern Mexico through Central America into Colombia, with Ecuadorian specimens resembling Nicaraguan material; Group II includes samples from Western-Southwestern Mexico; Group III comprises specimens from the Yucatán peninsula; and Group IV consists of sylvatic samples from Belize. The closely-related, yet formally recognized species T. hegneri from the island of Cozumel falls within the divergence range of the T. dimidiata populations studied. Conclusions We propose that Groups I–IV, as well as T. hegneri, should be regarded as separate species. In the Petén of Guatemala, representatives of Groups I, II, and III occur in sympatry; the absence of haplotypes with intermediate genetic distances, as shown by multimodal mismatch distribution plots, clearly indicates that reproductive barriers actively promote within-group cohesion. Some sylvatic specimens from Belize belong to a different species – likely the basal lineage of the T. dimidiata complex, originated ~8.25 Mya. The evidence presented here strongly supports the proposition that T. dimidiata is a complex of five cryptic species (Groups I–IV plus T. hegneri) that play different roles as vectors of Chagas disease in the region.
Molecular Evidence of Demographic Expansion of the Chagas Disease Vector Triatoma dimidiata (Hemiptera, Reduviidae, Triatominae) in Colombia  [PDF]
Andrés Gómez-Palacio ,Omar Triana
PLOS Neglected Tropical Diseases , 2014, DOI: 10.1371/journal.pntd.0002734
Abstract: Background Triatoma dimidiata is one of the most significant vectors of Chagas disease in Central America and Colombia, and, as in most species, its pattern of genetic variation within and among populations is strongly affected by its phylogeographic history. A putative origin from Central America has been proposed for Colombian populations, and high genetic differentiation among three biographically different population groups has recently been evidenced. Analyses based on putatively neutral markers provide data from which past events, such as population expansions and colonization, can be inferred. We analyzed the genealogies of the nicotinamide adenine dinucleotide dehydrogenase 4 (ND4) and the cytochrome oxidase subunit 1-mitochondrial genes, as well as partial nuclear ITS-2 DNA sequences obtained across most of the eco-geographical range in Colombia, to assess the population structure and demographic factors that may explain the geographical distribution of T. dimidiata in this country. Results The population structure results support a significant association between genetic divergence and the eco-geographical location of population groups, suggesting that clear signals of demographic expansion can explain the geographical distribution of haplotypes of population groups. Additionally, empirical date estimation of the event suggests that the population's expansion can be placed after the emergence of the Panama Isthmus, and that it was possibly followed by a population fragmentation process, perhaps resulting from local adaptation accomplished by orographic factors such as geographical isolation. Conclusion Inferences about the historical population processes in Colombian T. dimidiata populations are generally in accordance with population expansions that may have been accomplished by two important biotic and orographic events such as the Great American Interchange and the uplift of the eastern range of the Andes mountains in central Colombia.
Triatoma dimidiata Infestation in Chagas Disease Endemic Regions of Guatemala: Comparison of Random and Targeted Cross-Sectional Surveys  [PDF]
Raymond J. King ,Celia Cordon-Rosales,Jonathan Cox,Clive R. Davies ?,Uriel D. Kitron
PLOS Neglected Tropical Diseases , 2011, DOI: 10.1371/journal.pntd.0001035
Abstract: Background Guatemala is presently engaged in the Central America Initiative to interrupt Chagas disease transmission by reducing intradomiciliary prevalence of Triatoma dimidiata, using targeted cross-sectional surveys to direct control measures to villages exceeding the 5% control threshold. The use of targeted surveys to guide disease control programs has not been evaluated. Here, we compare the findings from the targeted surveys to concurrent random cross-sectional surveys in two primary foci of Chagas disease transmission in central and southeastern Guatemala. Methodology/Principal Findings Survey prevalences of T. dimidiata intradomiciliary infestation by village and region were compared. Univariate logistic regression was used to assess the use of risk factors to target surveys and to evaluate indicators associated with village level intradomiciliary prevalences >5% by survey and region. Multivariate logistic regression models were developed to assess the ability of random and targeted surveys to target villages with intradomiciliary prevalence exceeding the control threshold within each region. Regional prevalences did not vary by survey; however, village prevalences were significantly greater in random surveys in central (13.0% versus 8.7%) and southeastern (22.7% versus 6.9%) Guatemala. The number of significant risk factors detected did not vary by survey in central Guatemala but differed considerably in the southeast with a greater number of significant risk factors in the random survey (e.g. land surface temperature, relative humidity, cropland, grassland, tile flooring, and stick and mud and palm and straw walls). Differences in the direction of risk factor associations were observed between regions in both survey types. The overall discriminative capacity was significantly greater in the random surveys in central and southeastern Guatemala, with an area under the receiver-operator curve (AUC) of 0.84 in the random surveys and approximately 0.64 in the targeted surveys in both regions. Sensitivity did not differ between surveys, but the positive predictive value was significantly greater in the random surveys. Conclusions/Significance Surprisingly, targeted surveys were not more effective at determining T. dimidiata prevalence or at directing control to high risk villages in comparison to random surveys. We recommend that random surveys should be selected over targeted surveys whenever possible, particularly when the focus is on directing disease control and elimination and when risk factor association has not been evaluated for all regions
Sobre a varia??o intra-específica em Triatoma dimidiata (Latreille) e Triatoma infestans (Klug) (Hemiptera, Reduviidae)
Lent, Herman;Jurberg, José;
Memórias do Instituto Oswaldo Cruz , 1985, DOI: 10.1590/S0074-02761985000300004
Abstract: the analysis of eight speciemens of triatoma dimidiata (latreille, 1811) of diverse origins, in order to characterize the structure of the male external genitalia (endosoma process, struts, phallosoma, vesica) led us to point out that the same variability is demonstrate by the species in relation to its external colour characters and the relation between the head and rostrum. triatoma dimidiata is a vector of chagas' disease in several american countries, from mexico (extreme north of its distribution) to the north of south america, including colombia, venezuela, ecuador and peru. similarly we have carried out a large scale study on male genitalia of triatoma infestans (klug, 1834) which also has a wide geographic distribution, but with stable external characters. the spines of the endosoma process which generally are few in number, might not exist in a small percentage of cases. we analysed fifteen specimens of diverse origins.
Current situation of Chagas disease in Central America
Ponce, Carlos;
Memórias do Instituto Oswaldo Cruz , 2007, DOI: 10.1590/S0074-02762007005000082
Abstract: chagas disease in central america is known since 1913 when the first human case was reported in el salvador. the other central american countries reported their first cases between 1933 and 1967. on october 1997 was launched the central american initiative for chagas disease control (ipca). the objectives of this sub-regional initiative are: (1) the elimination of rhodnius prolixus in central america; (2) the reduction of the domiciliary infestation of triatoma dimidiata; and (3) the elimination of the transfusion transmission of trypanosoma cruzi. significant advancements being close to the elimination of r. prolixus in central america and the control of the transfusion transmission has been a transcendent achievement for the sub-region. the main challenges that the ipca will have in the close future are: developing effective strategies for control and surveillance of t. dimidiata; and surveillance of other emerging triatominae species like r. pallescens, t. nitida, and t. ryckmani.
Epidemiology of Chagas disease in Guatemala: infection rate of Triatoma dimidiata, Triatoma nitida and Rhodnius prolixus (Hemiptera, Reduviidae) with Trypanosoma cruzi and Trypanosoma rangeli (Kinetoplastida, Trypanosomatidae)
Monroy, Carlota;Rodas, Antonieta;Mejía, Mildred;Rosales, Regina;Tabaru, Yuichiro;
Memórias do Instituto Oswaldo Cruz , 2003, DOI: 10.1590/S0074-02762003000300003
Abstract: a five-year domiciliary collection in the 22 departments of guatemala showed that out of 4,128 triatomines collected, 1,675 were triatoma dimidiata (latreille, 1811), 2,344 were rhodnius prolixus stal 1859, and only 109 were t. nitida usinger 1939. the chagas disease parasite, trypanosoma cruzi, was found in all three species. their natural infection rates were similar in the first two species (20.6%; 19.1%) and slightly lower in t. nitida(13.8%). however there was no significant difference in the infection rates in the three species (p = 0.131). t. dimidiata males have higher infection rates than females (p = 0.030), whereas for r. prolixus there is no difference in infection rates between males and females (p = 0.114). the sex ratios for all three species were significantly skewed. more males than females were found inside houses for t. dimidiata (p < 0.0001) and t. nitida (p = 0.011); a different pattern was seen for r. prolixus (p = 0.037) where more females were found. sex ratio is proposed as an index to show the mobility of t. dimidiata in different populations. t. dimidiata is widely distributed in the country, and is also the main vector in at least ten departments, but r. prolixus with higher vectorial capacity is an important vector in at least two departments.
Epidemiology of Chagas disease in Guatemala: infection rate of Triatoma dimidiata, Triatoma nitida and Rhodnius prolixus (Hemiptera, Reduviidae) with Trypanosoma cruzi and Trypanosoma rangeli (Kinetoplastida, Trypanosomatidae)
Monroy Carlota,Rodas Antonieta,Mejía Mildred,Rosales Regina
Memórias do Instituto Oswaldo Cruz , 2003,
Abstract: A five-year domiciliary collection in the 22 departments of Guatemala showed that out of 4,128 triatomines collected, 1,675 were Triatoma dimidiata (Latreille, 1811), 2,344 were Rhodnius prolixus Stal 1859, and only 109 were T. nitida Usinger 1939. The Chagas disease parasite, Trypanosoma cruzi, was found in all three species. Their natural infection rates were similar in the first two species (20.6%; 19.1%) and slightly lower in T. nitida(13.8%). However there was no significant difference in the infection rates in the three species (p = 0.131). T. dimidiata males have higher infection rates than females (p = 0.030), whereas for R. prolixus there is no difference in infection rates between males and females (p = 0.114). The sex ratios for all three species were significantly skewed. More males than females were found inside houses for T. dimidiata (p < 0.0001) and T. nitida (p = 0.011); a different pattern was seen for R. prolixus (p = 0.037) where more females were found. Sex ratio is proposed as an index to show the mobility of T. dimidiata in different populations. T. dimidiata is widely distributed in the country, and is also the main vector in at least ten departments, but R. prolixus with higher vectorial capacity is an important vector in at least two departments.
Public Street Lights Increase House Infestation by the Chagas Disease Vector Triatoma dimidiata  [PDF]
Freddy Santiago Pacheco-Tucuch, Maria Jesus Ramirez-Sierra, Sébastien Gourbière, Eric Dumonteil
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0036207
Abstract: Triatoma dimidiata is one of the primary vectors of Chagas disease. We previously documented the spatio-temporal infestation of houses by this species in the Yucatan peninsula, Mexico, and found that non-domiciliated triatomines were specifically attracted to houses. However, the factors mediating this attraction remained unclear. Artificial light has been known for a long time to attract many insect species, and therefore may contribute to the spread of different vector-borne diseases. Also, based on the collection of different species of triatomines with light traps, several authors have suggested that light might attract triatomines to houses, but the role of artificial light in house infestation has never been clearly demonstrated and quantified. Here we performed a spatial analysis of house infestation pattern by T. dimidiata in relation to the distribution of artificial light sources in three different villages from the Yucatan peninsula, Mexico. In all three villages, infested houses were significantly closer to public street light sources than non-infested houses (18.0±0.6 vs 22.6±0.4 m), and street lights rather than domestic lights were associated with house infestation. Accordingly, houses closer to a public street lights were 1.64 times more likely to be infested than houses further away (OR, CI95% 1.23–2.18). Behavioral experiments using a dual-choice chamber further confirmed that adult male and females were attracted to white light during their nocturnal activity. Attraction was also dependent on light color and decreased with increasing wavelength. While public lighting is usually associated with increased development, these data clearly show that it also directly contributes to house infestation by non-domiciliated T. dimidiata.
Hunting, Swimming, and Worshiping: Human Cultural Practices Illuminate the Blood Meal Sources of Cave Dwelling Chagas Vectors (Triatoma dimidiata) in Guatemala and Belize  [PDF]
Lori Stevens ,M. Carlota Monroy,Antonieta Guadalupe Rodas,Patricia L. Dorn
PLOS Neglected Tropical Diseases , 2014, DOI: 10.1371/journal.pntd.0003047
Abstract: Background Triatoma dimidiata, currently the major Central American vector of Trypanosoma cruzi, the parasite that causes Chagas disease, inhabits caves throughout the region. This research investigates the possibility that cave dwelling T. dimidiata might transmit the parasite to humans and links the blood meal sources of cave vectors to cultural practices that differ among locations. Methodology/Principal Findings We determined the blood meal sources of twenty-four T. dimidiata collected from two locations in Guatemala and one in Belize where human interactions with the caves differ. Blood meal sources were determined by cloning and sequencing PCR products amplified from DNA extracted from the vector abdomen using primers specific for the vertebrate 12S mitochondrial gene. The blood meal sources were inferred by ≥99% identity with published sequences. We found 70% of cave-collected T. dimidiata positive for human DNA. The vectors had fed on 10 additional vertebrates with a variety of relationships to humans, including companion animal (dog), food animals (pig, sheep/goat), wild animals (duck, two bat, two opossum species) and commensal animals (mouse, rat). Vectors from all locations fed on humans and commensal animals. The blood meal sources differ among locations, as well as the likelihood of feeding on dog and food animals. Vectors from one location were tested for T. cruzi infection, and 30% (3/10) tested positive, including two positive for human blood meals. Conclusions/Significance Cave dwelling Chagas disease vectors feed on humans and commensal animals as well as dog, food animals and wild animals. Blood meal sources were related to human uses of the caves. We caution that just as T. dimidiata in caves may pose an epidemiological risk, there may be other situations where risk is thought to be minimal, but is not.
Two Distinct Triatoma dimidiata (Latreille, 1811) Taxa Are Found in Sympatry in Guatemala and Mexico  [PDF]
Patricia L. Dorn equal contributor ,Claudia Calderon equal contributor,Sergio Melgar equal contributor,Barbara Moguel,Elizabeth Solorzano,Eric Dumonteil,Antonieta Rodas,Nick de la Rua,Roberto Garnica,Carlota Monroy
PLOS Neglected Tropical Diseases , 2009, DOI: 10.1371/journal.pntd.0000393
Abstract: Approximately 10 million people are infected with Trypanosoma cruzi, the causative agent of Chagas disease, which remains the most serious parasitic disease in the Americas. Most people are infected via triatomine vectors. Transmission has been largely halted in South America in areas with predominantly domestic vectors. However, one of the main Chagas vectors in Mesoamerica, Triatoma dimidiata, poses special challenges to control due to its diversity across its large geographic range (from Mexico into northern South America), and peridomestic and sylvatic populations that repopulate houses following pesticide treatment. Recent evidence suggests T. dimidiata may be a complex of species, perhaps including cryptic species; taxonomic ambiguity which confounds control. The nuclear sequence of the internal transcribed spacer 2 (ITS2) of the ribosomal DNA and the mitochondrial cytochrome b (mt cyt b) gene were used to analyze the taxonomy of T. dimidiata from southern Mexico throughout Central America. ITS2 sequence divides T. dimidiata into four taxa. The first three are found mostly localized to specific geographic regions with some overlap: (1) southern Mexico and Guatemala (Group 2); (2) Guatemala, Honduras, El Salvador, Nicaragua, and Costa Rica (Group 1A); (3) and Panama (Group 1B). We extend ITS2 Group 1A south into Costa Rica, Group 2 into southern Guatemala and show the first information on isolates in Belize, identifying Groups 2 and 3 in that country. The fourth group (Group 3), a potential cryptic species, is dispersed across parts of Mexico, Guatemala, and Belize. We show it exists in sympatry with other groups in Peten, Guatemala, and Yucatan, Mexico. Mitochondrial cyt b data supports this putative cryptic species in sympatry with others. However, unlike the clear distinction of the remaining groups by ITS2, the remaining groups are not separated by mt cyt b. This work contributes to an understanding of the taxonomy and population subdivision of T. dimidiata, essential for designing effective control strategies.
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