ABSTRACT
Fine scale patterns of genetic structure and dispersal in Triatoma infestans populations from Argentina was analysed. A total of 314 insects from 22 domestic and peridomestic sites from the locality of San Martín (Capayán department, Catamarca province) were typed for 10 polymorphic microsatellite loci. The results confirm subdivision of T. infestans populations with restricted dispersal among sampling sites and suggest inbreeding and/or stratification within the different domestic and peridomestic structures. Spatial correlation analysis showed that the scale of structuring is approximately of 400 m, indicating that active dispersal would occur within this distance range. It was detected difference in scale of structuring among sexes, with females dispersing over greater distances than males. This study suggests that insecticide treatment and surveillance should be extended within a radius of 400 m around the infested area, which would help to reduce the probability of reinfestation by covering an area of active dispersal. The inferences made from fine-scale spatial genetic structure analyses of T. infestans populations has demonstrated to be important for community-wide control programs, providing a complementary approach to help improve vector control strategies.
Subject(s)
Insect Vectors/genetics , Microsatellite Repeats/genetics , Triatoma/genetics , Animal Migration , Animals , Argentina , Ecosystem , Female , Inbreeding , Male , Polymorphism, Genetic , Population/genetics , Sex CharacteristicsABSTRACT
Here we apply inter-simple sequence repeat (ISSR) markers to explore the fine-scale genetic structure and dispersal in populations of Triatoma infestans. Five selected primers from 30 primers were used to amplify ISSRs by polymerase chain reaction. A total of 90 polymorphic bands were detected across 134 individuals captured from 11 peridomestic sites from the locality of San Martín (Capayán Department, Catamarca Province, Argentina). Significant levels of genetic differentiation suggest limited gene flow among sampling sites. Spatial autocorrelation analysis confirms that dispersal occurs on the scale of â¼469 m, suggesting that insecticide spraying should be extended at least within a radius of â¼500 m around the infested area. Moreover, Bayesian clustering algorithms indicated genetic exchange among different sites analyzed, supporting the hypothesis of an important role of peridomestic structures in the process of reinfestation.
Subject(s)
Genetics, Population , Microsatellite Repeats , Triatoma/genetics , Animals , Argentina , Bayes Theorem , Chagas Disease/prevention & control , DNA Fragmentation , Gene Flow , Genetic Loci , Genetic Markers , Insect Control , Insect Vectors/genetics , Insect Vectors/parasitology , Insecticides/pharmacology , Polymorphism, Single Nucleotide , Specimen Handling , Triatoma/parasitologyABSTRACT
Variation in mitochondrial NADH dehydrogenase subunit 5 (ND5) and NADH dehydrogenase subunit 4 (ND4) genes was surveyed in Triatoma infestans from 24 localities of Argentina. The DNA sequence comparisons of 2,183 basepairs of the mitochondrial genome, which include the complete sequence of ND5 (1,712 basepairs) and 401 basepairs of ND4 genes, showed 19 haplotypes determined by 48 variable sites and a nucleotide diversity value of 0.292%. Twenty-six (65%) substitutions were synonymous, and there were 14 (35%) predicted amino acid replacements in ND5. In ND4, 5 (62.5%) substitutions were synonymous and 3 (37.5%) were replacement sites. Samples from six localities studied shared one haplotype and the rest of the localities had different haplotypes. The amplified regions should be useful for population genetic studies.
Subject(s)
Chagas Disease/transmission , Genetic Variation , Insect Vectors/enzymology , Mitochondria/enzymology , NADH Dehydrogenase/genetics , Triatoma/enzymology , Animals , Argentina , Chagas Disease/parasitology , DNA, Mitochondrial , Genetics, Population , Haplotypes , Insect Proteins/chemistry , Insect Proteins/genetics , Insect Vectors/genetics , Mitochondria/chemistry , Mitochondria/genetics , NADH Dehydrogenase/chemistry , Sequence Analysis, DNA , Triatoma/geneticsABSTRACT
The genetic structure in populations of the Chagas' disease vector Triatoma infestans from six localities belonging to areas under the same insecticide treatment conditions of Catamarca province (Argentina) was examined at macrogeographical and microgeographical scales. A total of 238 insects were typed for 10 polymorphic microsatellite loci. The average observed and expected heterozygosities ranged from 0.319 to 0.549 and from 0.389 to 0.689, respectively. The present results confirm that populations of T. infestans are highly structured. Spatial genetic structure was detectable at macrogeographical and microgeographical levels. Comparisons of the levels of genetic variability between two temporal samples were carried out to assess the impact of the insecticide treatment. The genetic diversity of the population was not significantly affected after insecticide use since different genetic parameters (allele number, observed and expected heterozygosities) remained stable. However, loss of low frequency alleles and not previously found alleles were detected. The effective population size (N(e)) estimated was substantially lower in the second temporal sample than in the first; nevertheless, it is possible that the size of the remnant population after insecticide treatment was still large enough to retain the genetic diversity. Very few individuals did not belong to the local T. infestans populations as determined by assignment analyses, suggesting a low level of immigration in the population. The results of the assignment and first-generation migrant tests suggest male-biased dispersal at microgeographical level.
Subject(s)
Chagas Disease/transmission , Disease Vectors , Triatoma/genetics , Alleles , Animals , Argentina , Family Characteristics , Female , Genetic Markers/genetics , Genetic Variation , Geography , Insecticides/pharmacology , Male , Microsatellite Repeats , Time FactorsABSTRACT
The genetic structure in populations of the Chagas' disease vector Triatoma infestans was examined. Comparisons of the levels of genetic variability in populations of this species from areas with different periods since last insecticide treatment and from areas that never received treatment were also carried out. A total of 598 insects from 19 populations were typed for 10 polymorphic microsatellite loci. The average observed and expected heterozygosities ranged from 0.186 to 0.625 and from 0.173 to 0.787, respectively. Genetic drift and limited gene flow appear to have generated a substantial degree of genetic differentiation among the populations of T. infestans. Departures from Hardy-Weinberg expectations due to an excess of homozygotes suggested the presence of null alleles and population subdivision. Microgeographical analysis supports the existence of subdivision in T. infestans populations. Levels of genetic diversity in the majority of the populations of T. infestans from insecticide-treated localities were similar or higher than those detected in populations from areas without treatment. Since the populations of T. infestans are subdivided, a population bottleneck would result in independent genetic drift effects that could randomly preserve different combinations of alleles in each subpopulation. These events followed by a rapid population growth could have preserved high levels of genetic diversity. This study supports the hypothesis of vector population recovery from survivors of the insecticide-treated areas and therefore highlights the value of population genetic analyses in assessing the effectiveness of Chagas' disease vector control programmes.