RESUMO
The evolution of reproductive division of labour and social life in social insects has lead to the emergence of several life-history traits and adaptations typical of larger organisms: social insect colonies can reach masses of several kilograms, they start reproducing only when they are several years old, and can live for decades. These features and the monopolization of reproduction by only one or few individuals in a colony should affect molecular evolution by reducing the effective population size. We tested this prediction by analysing genome-wide patterns of coding sequence polymorphism and divergence in eusocial vs. noneusocial insects based on newly generated RNA-seq data. We report very low amounts of genetic polymorphism and an elevated ratio of nonsynonymous to synonymous changes a marker of the effective population size in four distinct species of eusocial insects, which were more similar to vertebrates than to solitary insects regarding molecular evolutionary processes. Moreover, the ratio of nonsynonymous to synonymous substitutions was positively correlated with the level of social complexity across ant species. These results are fully consistent with the hypothesis of a reduced effective population size and an increased genetic load in eusocial insects, indicating that the evolution of social life has important consequences at both the genomic and population levels.
Assuntos
Genômica , Insetos/genética , Densidade Demográfica , Animais , Insetos/classificação , Filogenia , TranscriptomaRESUMO
Trypanosoma congolense forest-type was identified by PCR in France, in a dog returning from Senegal. This paper describes the morphological features of the parasite on Giemsa-stained smears. Slender forms and "latent bodies" represent 30.4% and 20.4%, respectively. Some rosettes have been observed (0.8%). The predominant form (48.4%) is stumpy, close to "montgomeryi-form", but it is unusually broad, with a width/length ratio (WLr) of 0.40-0.55, while that of "montgomeryi-forms" is close to 0.3. To the best of our knowledge, this is the first description of such a form of T. (Nannomonas). Also unusual, the shape of the cytoplasm appears to be tightened by an "S-" or "C-" shaped flagellum. We propose naming this peculiar morphotype "hyperpachymorph", and adding its description to that of T. congolense forest-type. Thus T. (Nannomonas) forms would include: sphaeromorph or "latent body-form" (globular), hyperleptomorph (rodhaini-form, very long and slender, with a free flagellum); leptomorph (simiae-form, slender, with a free flagellum); isomorph (congolense-form, short, generally without a free flagellum); pachymorph (montgomeryi-form, short and stout; 0.25 < WLr < 0.34, without a free flagellum), and hyperpachymorph ("hyper montgomeryi-form", short and very stout; 0.35 < WLr < 0.7, without a free flagellum).
Assuntos
Doenças do Cão/parasitologia , Trypanosoma congolense/isolamento & purificação , Tripanossomíase Africana/veterinária , Animais , DNA de Protozoário/isolamento & purificação , Doenças do Cão/tratamento farmacológico , Cães , Evolução Fatal , França , Injeções Intramusculares/veterinária , Masculino , Pentamidina/administração & dosagem , Pentamidina/uso terapêutico , Reação em Cadeia da Polimerase/veterinária , Senegal , Viagem , Tripanossomicidas/administração & dosagem , Tripanossomicidas/uso terapêutico , Trypanosoma congolense/classificação , Trypanosoma congolense/genética , Trypanosoma congolense/ultraestrutura , Tripanossomíase Africana/tratamento farmacológico , Tripanossomíase Africana/parasitologiaRESUMO
The impact of landscape fragmentation resulting from human- and climate-mediated factors on the structure of a population of Glossina tachinoides Westwood (Diptera: Glossinidae) in the Mouhoun River basin, Burkina Faso, was investigated. Allele frequencies at five microsatellite loci were compared in four populations. The average distance between samples was 72 km. The sampling points traversed an ecological cline in terms of rainfall and riverine forest ecotype, along a river loop that enlarged from upstream to downstream. Microsatellite DNA demonstrated no structuring among the groups studied (F(ST) = 0.015, P = 0.07), which is contrary to findings pertaining to Glossina palpalis gambiensis Vanderplank in the same geographical area. The populations of G. tachinoides showed complete panmixia (F(IS) = 0, P = 0.5 for the whole sample) and no genetic differentiation among populations or global positioning system trap locations. This is in line with the results of dispersal studies which indicated higher diffusion coefficients for G. tachinoides than for G. p. gambiensis. The impact of these findings is discussed within the framework of control campaigns currently promoted by the Pan African Tsetse and Trypanosomosis Eradication Campaign.
Assuntos
Ecossistema , Insetos Vetores/fisiologia , Moscas Tsé-Tsé/fisiologia , Animais , Burkina Faso , Demografia , Frequência do Gene , Geografia , Insetos Vetores/genética , Repetições de Microssatélites/genética , Moscas Tsé-Tsé/genéticaRESUMO
Tsetse flies (Diptera: Glossinidae) are the main vectors of animal and human trypanosomoses in Africa. The Sterile Insect Technique (SIT) has proven effective in controlling tsetse flies when applied to isolated populations but necessitates the production of large numbers of sterile males. A new approach, called boosted SIT, combining SIT with the contamination of wild females by sterile males coated with biocides has been proposed for large-scale control of vector populations. The aim of the study was to evaluate this new approach using pyriproxyfen on the riverine species Glossina palpalis gambiensis (Vanderplank, 1949) in the laboratory. The contamination dose and persistence of pyriproxyfen on sterile males, the impact of pyriproxyfen on male survival, and the dynamics of pyriproxyfen transfer from a sterile male to a female during mating, as well as the impact of pyriproxyfen on pupal production and adult emergence, were evaluated in the laboratory. For this purpose, a method of treatment by impregnating sterile males with a powder containing 40% pyriproxyfen has been developed. The results showed that the pyriproxyfen has no impact on the survival of sterile males. Pyriproxyfen persisted on sterile males for up to 10 days at a dose of 100 ng per fly. In addition, the horizontal transfer of pyriproxyfen from a treated sterile male to a female during mating could be measured with an average of 50 ng of pyriproxyfen transferred. After contacts without mating, the average quantity transferred was more than 10 ng. Finally, the pyriproxyfen powder was very effective on G. p. gambiensis leading to 0% emergence of the pupae produced by contaminated females. These promising results must be confirmed in the field. A large-scale assessment of this boosted pyriproxyfen-based SIT approach will be carried out against tsetse flies in Senegal (West Africa).
Assuntos
Controle de Insetos/métodos , Insetos Vetores/efeitos dos fármacos , Inseticidas/toxicidade , Piridinas/toxicidade , Moscas Tsé-Tsé/efeitos dos fármacos , Animais , Feminino , Infertilidade Masculina/genética , Insetos Vetores/fisiologia , Insetos Vetores/efeitos da radiação , Inseticidas/farmacologia , Masculino , Piridinas/farmacologia , Radiação Ionizante , Reprodução , Moscas Tsé-Tsé/fisiologia , Moscas Tsé-Tsé/efeitos da radiaçãoRESUMO
The West African trypanosomoses are mostly transmitted by riverine species of tsetse fly. In this study, we estimate the dispersal and population size of tsetse populations located along the Mouhoun river in Burkina Faso where tsetse habitats are experiencing increasing fragmentation caused by human encroachment. Dispersal estimated through direct (mark and recapture) and indirect (genetic isolation by distance) methods appeared consistent with one another. In these fragmented landscapes, tsetse flies displayed localized, small subpopulations with relatively short effective dispersal. We discuss how such information is crucial for designing optimal strategies for eliminating this threat. To estimate ecological parameters of wild animal populations, the genetic measures are both a cost- and time-effective alternative to mark-release-recapture. They can be applied to other vector-borne diseases of medical and/or economic importance.
Assuntos
Variação Genética , Genética Populacional , Insetos Vetores/genética , Moscas Tsé-Tsé/genética , Animais , Burkina Faso , Ecossistema , Geografia , Homozigoto , Repetições de Microssatélites , Densidade Demográfica , Rios , Análise de Sequência de DNARESUMO
Relationships of 13 species of the genus Glossina (tsetse flies) were inferred from mitochondrial (cytochrome oxidase 1, NADH dehydrogenase 2 and 16S) and nuclear (internal transcribed spacer 1 of rDNA) sequences. The resulting phylogeny confirms the monophyly of the morphologically defined fusca, morsitans and palpalis subgenera. Genetic distances between palpalis and morsitans subspecies suggest that their status needs revision. In particular, cytochrome oxidase 1 sequences showed large geographical differences within G. palpalis palpalis, suggesting the existence of cryptic species within this subspecies. The morphology of palpalis group female genital plates was examined, and individuals were found varying outside the ranges specified by the standard identification keys, making definitive morphological classification impossible. A diagnostic PCR to distinguish G. palpalis palpalis, G. tachinoides and G. palpalis gambiensis based on length differences of internal transcribed spacer 1 sequences is presented.
Assuntos
Filogenia , Moscas Tsé-Tsé/classificação , Moscas Tsé-Tsé/genética , Algoritmos , Animais , DNA Mitocondrial/genética , DNA Ribossômico/genética , Feminino , Genes de Insetos , Genes Mitocondriais , Marcadores Genéticos , Haplótipos , Funções Verossimilhança , Mitocôndrias/genética , Alinhamento de Sequência , Análise de Sequência de DNA , Especificidade da Espécie , Moscas Tsé-Tsé/anatomia & histologiaRESUMO
Cacao swollen shoot virus is a member of the family Caulimoviridae, genus Badnavirus and is naturally transmitted to Theobroma cacao (L.) by several mealybug species. CSSV populations in West African countries are highly variable and genetically structured into several different groups based on the diversity in the first part of ORF3 which encodes the movement protein. To unravel the extent of isolate diversity and address the problems of low titer and mixed viral sequences in samples, we used Illumina MiSeq and HiSeq technology. We were able to reconstruct de novo 20 new complete genomes from cacao samples collected in the Cocoa Research Institute of Ghana (CRIG) Museum and from the field samples collected in Côte d'Ivoire or Ghana. Based on the 20% threshold of nucleotide divergence in the reverse transcriptase/ribonuclease H (RT/RNase H) region which denotes species demarcation, we conclude there exist seven new species associated with the cacao swollen shoot disease. These new species along with the three already described leads to ten, the total number of the complex of viral species associated with the disease. A sample from Sri Lanka exhibiting similar leaf symptomology to West African CSSD-affected plants was also included in the study and the corresponding sequence represents the genome of a new virus named cacao bacilliform SriLanka virus (CBSLV).
Assuntos
Badnavirus/genética , Cacau/virologia , Variação Genética , Genoma Viral , Filogenia , Proteínas Virais/genética , Animais , Badnavirus/classificação , Badnavirus/isolamento & purificação , DNA Viral/genética , Expressão Gênica , Hemípteros/virologia , Insetos Vetores/virologia , Fases de Leitura Aberta , Doenças das Plantas/virologia , Folhas de Planta/virologia , DNA Polimerase Dirigida por RNA/genética , Ribonuclease H/genética , Análise de Sequência de DNARESUMO
Glossina palpalis is the main vector of human African trypanosomosis (HAT, or sleeping sickness) that dramatically affects human health in sub-Saharan Africa. Because of the implications of genetic structuring of vector populations for the design and efficacy of control campaigns, G. palpalis palpalis in the most active focus of sleeping sickness in Côte d'Ivoire was studied to determine whether this taxon is genetically structured. High and statistically significant levels of within population heterozygote deficiencies were found at each of the five microsatellite loci in two temporally separated samples. Neither null alleles, short allele dominance, nor trap locations could fully explain these deviations from random mating, but a clustering within each of the two samples into different genetic sub-populations (Wahlund effect) was strongly suggested. These different genetic groups, which could display differences in infection rates and trypanosome identity, were composed of small numbers of individuals that were captured together, leading to the observed Wahlund effect. Implications of this population structure on tsetse control are discussed.
Assuntos
Tripanossomíase Africana/parasitologia , Moscas Tsé-Tsé/classificação , Moscas Tsé-Tsé/genética , Animais , Côte d'Ivoire/epidemiologia , Feminino , Humanos , Insetos Vetores/parasitologia , Masculino , Filogenia , Tripanossomíase Africana/epidemiologia , Tripanossomíase Africana/transmissão , Moscas Tsé-Tsé/parasitologiaRESUMO
Six sets of teneral Glossina palpalis gambiensis (Diptera: Glossinidae) were fed on mice infected with six different isolates of Trypanosoma brucei gambiense (each mouse was infected with one of the isolates), previously isolated from patients in the sleeping sickness focus of Bonon, Côte d'Ivoire and in Makoua, Congo. All the tsetse flies were dissected 42 days post-infection and midgut and salivary glands were examined for trypanosomes by microscopical examination. No infection was observed with the reference stock whereas each of the five recently isolated trypanosome isolates was able to infect tsetse flies, with rates of infection varying between 9.7 and 18.2% depending on the isolate. Three isolates displayed only immature infections with 9.7, 17.3 and 18% of the flies showing trypanosomes in their midgut. One isolate gave both immature (12.1%) and mature infections (6.1%). Finally, the last isolate involved only mature infections in 9.7% of the Glossina species examined. These substantial differences in the cyclical transmission of T. b. gambiense in the same fly species could have important implications for the epidemiology of the transmission of Human African Trypanosomiasis.
Assuntos
Trypanosoma brucei gambiense/patogenicidade , Moscas Tsé-Tsé/parasitologia , Animais , Sistema Digestório/parasitologia , Humanos , Masculino , Camundongos , Glândulas Salivares/parasitologia , Trypanosoma brucei gambiense/fisiologia , Tripanossomíase Africana/parasitologiaRESUMO
Tonically active neurons (TANs) in the monkey striatum are involved in detecting motivationally relevant stimuli. We recently provided evidence that the timing of conditioned stimuli strongly influences the responsiveness of TANs, the source of which is likely to be the monkey's previous experience with particular temporal regularities in sequential task events. To extend these findings, we investigated the relationship of TAN responses to a primary liquid reward, the timing of which is more or less predictable to the monkey either outside of a task or during instrumental task performance. Reward predictability was indexed by the timing characteristics of the mouth movements. The responsiveness of TANs to reward increased with the range and variability of time periods before reward, notably when the liquid was delivered outside of a task. A change in the temporal order of events in a task context produced an increase of response to reward, suggesting an influence of the predicted nature of the event in addition to its time of occurrence. By contrast, we observed no substantial changes in neuronal activity at the expected time of reward when this event failed to occur, suggesting that these neurons do not appear to carry information about an error in reward prediction. These results demonstrate that TANs constitute a neuronal system that is involved in detecting unpredicted reward events, irrespective of the specific behavioral situation in which such events occur. The responses influenced by stimulus prediction may constitute a neuronal basis for the notion that striatal processing is crucial for habit learning.
Assuntos
Corpo Estriado/fisiologia , Intuição/fisiologia , Neurônios/fisiologia , Recompensa , Animais , Braço/fisiologia , Aprendizagem por Associação/fisiologia , Comportamento Animal/fisiologia , Condicionamento Clássico/fisiologia , Corpo Estriado/citologia , Eletrodos Implantados , Eletrofisiologia , Hábitos , Macaca fascicularis , Masculino , Movimento/fisiologia , Desempenho Psicomotor/fisiologia , Tempo de Reação/fisiologia , Fatores de TempoRESUMO
The efficiency of supplying cholesterol by the LDL endocytic pathway of lymphoblastic T CEM cells was compared when incubated in the presence of either fetal calf serum (FCS) or lipoprotein-depleted fetal calf serum (LDFCS). In the presence of FCS, there were 8600 +/- 2000 LDL receptors/cell with a Kd of (2.2 +/- 0.8).10(-8) M and a receptor cycling time of about 7 min; about 90% of the internalized LDL was degraded. LDL degradation produced 98% of total cellular cholesterol and only 2% came from endogenous synthesis. The absence of LDL in the culture medium of lymphoblastic CEM cells deeply modified certain metabolic and structural characteristics of the cells. Their cholesterol content decreased; the total number of LDL receptors increased 6-fold, whereas their affinity for the ligand decreased by the same factor (Kd = (1.2 +/- 0.2).10(-7) M); the receptor cycling time increased 3-fold. Finally, LDL degraded by cholesterol-depleted CEM cells amounted to about 40% of that degraded by untreated CEM cells.
Assuntos
Endocitose , Lipoproteínas LDL/fisiologia , Receptores de LDL/fisiologia , Colesterol/metabolismo , Sangue Fetal/fisiologia , Homeostase , Humanos , Leucemia de Células T/metabolismo , Leucemia de Células T/patologia , Receptores de LDL/análise , Células Tumorais CultivadasRESUMO
In Africa the highest HIV infection rate has been reported among female commercial sex workers (CSWs) who are at increasing risk of acquiring and transmitting HIV infection. In October 1995, 176 CSWs were studied in Bamako, the capital city of Mali. The ages of the CSWs ranged from 15 to 50 years old (mean, 28.8 years). Only 20.45% of the 176 CSWs were Malian; the majority were from Nigeria (32.9%) and Ghana (31.8%), and the remaining were from other African countries. Forty-one percent were active for less than 1 year as a commercial sex worker, and the length of prostitution for the remaining women ranged from 1 to 15 years (mean, 2.76). A total of 81 (46.02%) of the 176 CSWs were positive for HIV antibodies; 63 (35.8%) were HIV-1 positive, (3.9%) were HIV-2 positive, 11 (6.2%) had antibodies to HIV-1 and HIV-2, and none of them had antibodies to group O viruses. For all HIV antibody-positive samples, PBMCs were separated and genetic subtypes of HIV-1 were determined using the heteroduplex mobility assay (HMA), with ED5-ED12 as outer and ES7-ES8 as inner primers. Among the 66 HIV-1 strains characterized, 53 (80.3%) were subtype A, 2 (3.1%) belonged to subtype C, 1 (1.5%) belonged to subtype D, and 10 (15.1%) were identified as subtype G. Among the 10 subtype G strains, 8 were obtained from women who were very recent CSWs, with an activity of 1 year or less, assuming that there is a high probability that these infections occurred recently. Genetic subtypes of five HIV-2 viruses were determined by sequencing of the env and/or gag genes followed by phylogenetic analysis, and all of them belonged to subtype A. Comparison of HIV-1 and HIV-2 seroprevalence data from our study with previous data from Mali shows a significant rise in HIV-1 prevalence and a significant decrease in HIV-2 prevalence and confirms similar trends observed in neighboring countries. We have found four different genetic subtypes of HIV-1; however, subtype A is predominant and accounts for 80% of the cases and 15% of the HIV-1 infections were subtype G. It is important to continue the surveillance of subtypes on a systematic basis in order to see to what extent the proportions of the different subtypes will change over time.
PIP: The genetic variability of HIV-1 was investigated in a 1995 study of 176 commercial sex workers (CSWs) recruited in different areas in Bamako, Mali. 36 CSWs (20.45%) were born in Mali; 58 (32.9%) were from Nigeria and 56 (31.8%) were from Ghana. They ranged in age from 15-50 years (mean, 28.8 years). 41% of sex workers had been active for less than 12 months; the remaining women had been CSWs for 1-15 years (mean, 2.76 years). Of the 81 CSWs (46.02%) who were HIV-positive, 63 (35.8%) were infected with HIV-1, 7 (3.9%) with HIV-2, and the remaining 11 (6.2%) had antibodies to both HIV-1 and HIV-2. In contrast to other studies conducted among CSWs in Africa, none of these sex workers had antibodies to group O viruses. HIV-1 prevalence increased with age and length of time in prostitution and was higher among women with a history of sexually transmitted diseases. Among the 66 HIV-1 strains characterized, 53 (80.3%) were subtype A, 2 (3.1%) belonged to subtype C, 1 (1.5%) belonged to subtype D, and 10 (15.1%) were identified as subtype G. These results indicate a significant rise in HIV-1 prevalence and significant decreases in HIV-2 and combined HIV-1 and HIV-2 prevalence (10%, 15%, and 13%, respectively, in 1985). Ongoing surveillance of HIV-1 subtypes in Africa is important to identify shifts in the proportions of different subtypes over time. The genetic diversity of HIV has important implications for vaccine development.
Assuntos
HIV-1/genética , HIV-2/genética , Trabalho Sexual , Adolescente , Adulto , Feminino , Infecções por HIV/epidemiologia , Humanos , Mali/epidemiologia , Pessoa de Meia-Idade , FilogeniaRESUMO
Teneral Glossina palpalis gambiensis (Diptera: Glossinidae) were infected with a culture of procyclic forms of Trypanosoma brucei gambiense using a single-bloodmeal membrane feeding technique. The infection was monitored by analysing the saliva (mature infection) and anal drop (midgut infection) of each fly at different post-infection times both by microscopic observation and polymerase chain reaction (PCR). Amplification revealed many more positive anal drops than microscopy. The monitoring showed that the installation of T. b. gambiense in Glossina took place at least 11 days after the infection and that maturation occurred after 29 days. It also reflected precisely the parasitic status of each tsetse fly as determined by the dissection, microscopic examination and PCR amplification of the midguts and salivary glands 47 days post-infection. Twice as many tsetse flies with mature salivary glands infection were revealed by PCR than by microscopic examination, but the two techniques gave exactly the same results regarding the proportion of flies with midgut infection. This study also demonstrated the ability of natural non-infective procyclic forms of T. b. gambiense, to colonise the midgut and subsequently establish in the salivary glands of G. p. gambiensis.
Assuntos
Trypanosoma brucei gambiense/crescimento & desenvolvimento , Moscas Tsé-Tsé/parasitologia , Canal Anal/parasitologia , Animais , Feminino , Masculino , Reação em Cadeia da Polimerase , Saliva/parasitologia , Trypanosoma brucei gambiense/isolamento & purificaçãoRESUMO
We have developed a highly sensitive, simple and rapid procedure to detect Leishmania infantum within human macrophages. It only requires ficoll preparation of peripheral blood mononuclear cells from the patient, and their direct use for Leishmania kDNA amplification by polymerase chain reaction. Under these conditions, about one parasite can be detected in a one million human cell environment. Results, including those of a hybridization step to confirm the diagnosis specificity, are obtained with 24 h, a very short period as compared to current diagnostic methods. This procedure is of particular interest for early detection and early drug treatment of leishmaniasis, especially in the case of HIV coinfection. Furthermore, the method could be useful for monitoring the efficiency of new leishmaniasis treatments in infected patients.
Assuntos
Leishmania infantum/isolamento & purificação , Leucócitos Mononucleares/parasitologia , Reação em Cadeia da Polimerase , Animais , Sequência de Bases , Humanos , Macrófagos/parasitologia , Dados de Sequência Molecular , Sensibilidade e EspecificidadeRESUMO
Trypanosoma vivax is a widespread hemoparasite in tropical areas and is pathogenic to ruminant domestic livestock as well as wild ruminants. The accurate identification of parasites in both hosts and vectors is crucial for epidemiological studies and disease control programs. We describe here the development of molecular markers specific for T. vivax identification. These markers were used to identify mouthpart infections in field-collected tsetse flies from Cameroon. The markers target the genomic sequence of a species-specific antigen from the bloodstream stages. No cross amplification with other trypanosome species was observed, which makes the markers a reliable tool to detect T. vivax infections, both in hosts and vectors. The PCR-amplified sequence contains a (CA)(n) microsatellite repeat for which 11 different alleles were identified. This microsatellite, which showed high polymorphism, provides a suitable marker for population genetic studies.
Assuntos
Marcadores Genéticos/genética , Repetições de Microssatélites/genética , Trypanosoma vivax/classificação , Trypanosoma vivax/isolamento & purificação , Moscas Tsé-Tsé/parasitologia , Animais , DNA de Protozoário/análise , DNA de Protozoário/genética , Reação em Cadeia da Polimerase , Polimorfismo Genético/genética , Especificidade da Espécie , Trypanosoma vivax/genéticaRESUMO
In West Africa, Aedes aegypti (Diptera: Culicidae) (Linnaeus, C., 1762. Zweyter Theil, enhalt Beschreibungen veschiedener wichtiger Naturalien. In: Hasselquist, F. (Ed.), Reise nach Palastina in den Jahren von 1749 bis 1752, Rostock, Germany, pp. 267-606) represents the principal vector of yellow fever. This study reports the use of microsatellite markers to characterise various A. aegypti populations from Côte d'Ivoire according to a north-south transect, and to perform a temporal genetic survey of the mosquitoes. Three microsatellite loci were used to analyse individuals from four different places: Kabolo, Bouaké, and two different districts of Abidjan. We found that the four populations are genetically distinct except the two Abidjan populations. In the Bouaké population, the coexistence of two cryptic species, not morphologically distinguishable, seems to account for the extensive heterozygote deficiency observed. Comparison of mosquitoes from Bouaké 1 year apart indicated that a dramatic change occurred in the structuring of this population over time. Taken together these results indicate that microsatellite markers could be useful for identifying various populations of A. aegypti on a microgeographic scale and to assess for temporal variation within mosquito populations.
Assuntos
Aedes/genética , Variação Genética , Repetições de Microssatélites , Aedes/classificação , Animais , Côte d'Ivoire/epidemiologia , Frequência do Gene , Reação em Cadeia da Polimerase , Polimorfismo GenéticoRESUMO
Dengue fever recently reemerged in the Americas. Because vaccines are still under development, dengue prevention depends entirely on vector control. Since Aedes aegypti (Linnaeus, 1762) is the principal vector of this arbovirus, knowledge of the genetic structure of the insect is therefore required to maintain effective vector control strategies and to estimate levels of gene flow from which movement can be inferred. This preliminary study uses microsatellite and amplified fragment length polymorphism (AFLP) markers, to provide insights into genetic diversity of A. aegypti populations from different districts of two towns, located in the north-west of Mexico, Hermosillo and Guaymas. Although the microsatellites used were found to display limited polymorphism, they allowed discrimination between mosquitoes from the northern and the southern districts of Hermosillo. Using AFLP markers, clustering of individuals from the same town and from the same district was observed. Data from microsatellite and AFLP markers analysis both suggest that reinvasion of A. aegypti probably occurs from Guaymas to Hermosillo.
Assuntos
Aedes/genética , Repetições de Microssatélites/genética , Aedes/química , Alelos , Animais , DNA/química , Dengue/prevenção & controle , Dengue/transmissão , Eletroforese em Gel de Poliacrilamida , Feminino , Variação Genética/genética , Genética Populacional , México , Filogenia , Projetos Piloto , Reação em Cadeia da Polimerase , Polimorfismo GenéticoRESUMO
The present study was carried out in order to investigate if there was really a failure of PCR in identifying parasitologically positive tsetse flies in the field. Tsetse flies (Glossina palpalis gambiensis and Glossina morsitans morsitans) were therefore experimentally infected with two different species of Trypanosoma (Trypanosoma brucei gambiense or Trypanosoma congolense). A total of 152 tsetse flies were dissected, and organs of each fly (midgut, proboscis or salivary glands) were examined. The positive organs were then analysed using PCR. Results showed that, regardless of the trypanosome species, PCR failed to amplify 40% of the parasitologically positive midguts. This failure, which does not occur with diluted samples, is likely to be caused by an inhibition of the amplification reaction. This finding has important implications for the detection and the identification of trypanosome species in wild tsetse flies.
Assuntos
Insetos Vetores/parasitologia , Técnicas de Amplificação de Ácido Nucleico , Trypanosoma brucei gambiense/isolamento & purificação , Trypanosoma congolense/isolamento & purificação , Moscas Tsé-Tsé/parasitologia , Animais , DNA de Protozoário/análise , Sistema Digestório/parasitologia , Reação em Cadeia da Polimerase , Glândulas Salivares/parasitologia , Especificidade da Espécie , Trypanosoma brucei gambiense/genética , Trypanosoma congolense/genéticaRESUMO
Tsetse flies are the cyclical vectors of African animal trypanosomosis (AAT) and human African trypanosomosis (HAT). In March 2010, the Government of Ghana initiated a large scale integrated tsetse eradication campaign in the Upper West Region (UWR) (≈18,000 km(2)) under the umbrella of the Pan-African Tsetse and Trypanosomosis Eradication Campaign (PATTEC). We investigated the structuring of Glossina tachinoides populations within and between the three main river basins of the target area in the UWR. Out of a total sample of 884 flies, a sub-sample of 266 was genotyped at nine microsatellite loci. The significance of the different hierarchical levels was tested using Yang's parameters estimated with Weir and Cockerham's method. A significant effect of traps within groups (pooling traps no more than 3 km distant from each other), of groups within river basins and of river basins within the whole target area was observed. Isolation by distance between traps was highly significant. A local density of 0.48-0.61 flies/m(2) was estimated and a dispersal distance that approximated 11 m per generation [CI 9, 17]. No significant sex-biased dispersal was detected. Dispersal distances of G. tachinoides in the UWR were relatively low, possibly as a result of the fragmentation of the habitat and the seasonality of the Kulpawn and Sissili rivers. Moreover, very high fly population densities were observed in the sample sites, which potentially reduces dispersal at constant habitat saturation, because the probability that migrants can established is reduced (density dependent dispersal). However, the observed spatial dispersal was deemed sufficient for a G. tachinoides-cleared area to be reinvaded from neighboring populations in adjacent river basins. These data corroborate results from other population genetics studies in West Africa, which indicate that G. tachinoides populations from different river basins cannot be considered isolated.
Assuntos
Genética Populacional , Controle de Insetos , Rios , Moscas Tsé-Tsé/genética , Animais , Feminino , Loci Gênicos , Genótipo , Geografia , Gana , Endogamia , Masculino , Repetições de Microssatélites/genética , Tipagem Molecular , Densidade Demográfica , Dinâmica Populacional , Isolamento ReprodutivoRESUMO
Substantial differences have been observed between the cyclical transmission of three Trypanosoma brucei gambiense field isolates in Glossina palpalis gambiensis (Ravel et al., 2006). Differences in the pleomorphism of these isolates in rodent used to provide the infective feed to Glossina, could explain such results, since stumpy forms are preadapted for differentiation to procyclic forms when taken up in a tsetse bloodmeal. To assess this possibility, mice were immunosuppressed and inoculated intraperitoneally with the three isolates (six mice for each trypanosome isolate); then parasitaemia and pleomorphism were determined daily for each mouse. The three T. b. gambiense isolates induced different infection patterns in mouse. The parasitaemia peak was rapidly reached for all the isolates and maintained until mice death for two isolates, while the third isolate rapidly showed a falling phase followed by a second parasitaemia plateau. The proportion of the stumpy forms varied from 15% to 70% over the duration of the experiment and according to the isolate. One isolate, which displayed the highest proportion of stumpy forms and reached the stumpy peak at the onset of the falling phase of parasitaemia, was used to study the relationship between the proportion of stumpy forms and transmissibility to tsetse fly. The results indicated that the transmissibility of trypanosomes was not correlated to the proportion of non-dividing stumpy forms.