Observações sobre o comportamento de acasalamento de Culex quinquefasciatus Say (Diptera-Culicitlae)

An investigation was conducted into the mating behaviour of strains of Culex quinquefasciatus Say from the Gambia, West Africa and Amazonas, Brazil. Using an infra-red sensitive television system for observation in the "dark"; experiments showed that males are attracted to the flight tone of the female and do not appear to discriminate between members of their own and other genera. The response of males to artificial female flight tones is at a peak in the hour following light off in an LD12:12 regime and shows a circadian pattern in constant dark. In the field mating was observed when the males were actively swarming at dusk and dawn. It is concluded that mating is dependant on male activity but that the choice of a species specific partner is dependant on the female.Um estudo foi conduzido sobre o comportamento de acasalamento de linhagens de Culex quinquefasciatus Say do Gâmbia, África Ocidental e Amazonas. Brasil. Usando um sistema de televisão sensível ao infravermelho para observação no "escuro", os experimentos mostraram que os machos são atraídos pela emissão de som no vôo da fêmea e pareceram não distinguir entre membros de suas espécies e de outros gêneros. A resposta dos machos à emissão de som artificial de vôo da fêmea tem um pico em L.D. 12:12 na hora seguinte à interrupção da luz no laboratório e apresenta um padrão circadiano em escuro constante. No campo, o acasalamento foi observado quando os machos estavam em enxame voando ativamente. A conclusão obtida é de que o acasalamento depende da atividade do macho, mas que a escolha do padrão específico da espécie depende da fêmea

Estudos sobre a biologia e hábitos alimentares de Culex quinquefasciatus Say de Manaus, Amazonas, Brasil

A study was made of Culex quinquefasciatus Say a potential vector of urban filariasis in Manaus Amazonas. Catches were made of the biting and resting populations. The stages of ovarian development and parity were determined by examination of the external appearence of the abdomen and dissection for ovariole dilations. Most females appeared to rest after oviposition before returning to feed. Biting took place inside houses with peaks at dusk and around midnight. Daily mortality was similar to that In areas where transmission of filariasis occurs. Resting trap catches indicated that there was little fluctuation in numbers throughought the year and analysis of 274 blood meals demonstrated that man was the preferred host.Estudo sobre Culex quinquefasciatus Say, um vetor potencial da filariose urbana em Manaus, Amazonas. Foram realizadas coletas de populações no ato de picar e em repouso. Os estágios de desenvolvimento ovariano e paridade foram determinados pelo exame do aspecto externo do abdome e a dissecção para dilatações de ovaríolos. A maioria das fêmeas parece repousar após a ovoposição antes de voltar a alimentar-se. O ato de picar ocorria dentro das casas, com picos ao entardecer e por volta da meia-noite. A mortalidade diária era semelhante à das áreas em que ocorre a transmissão de filariose. Coletas com armadilhas, dos individuos em repouso, indicaram que ocorrem pequenas flutuações em números durante o ano, e a análise de 274 refeições de sangue demonstrou que o homem era o hospedeiro preferido

Variações geográficas no ciclo de picada do Anopheles darlingi Root no Brasil

The biting behaviour of Anopheles darlingi Root from three areas in Brasil is compared and differences in the biting cycle are discussed.O comportamento e as diferenças no ciclo do ataque do Anopheles darlingi Root, em três localidades diferentes brasileiras, foram comparadas e discutidas

Um rápido ciclo gonotrófico em Chagasia bonneae Root (Diptera: Culicidae) do Brasil

Man biting Chagasia bonneae Root were found to have recently oviposited. A gonotrophic cycle of less than three days is hypothesized

Dinâmica estacional de uma população de Anopheles darlingi, numa área endêmica de malária no Amazonas

The biting activity of Anopheles darlingi was studied for over a year in an endemic area of malaria - BR-174 (Manaus/Boa Vista). The biting activity was documented to show seasonal changes in population and variation in the cycle with changes of season. Data is presented for the outdoor biting cycle and indoor biting cycle collections. Patterns remained constant within the study area and the population of A. darlingi increases in dry season. Intense rainfall is accredited the decline in population - this decline corresponds to a similar seasonal decrease in the nunber of malaria cases.A atividade de picadas do Anopheles darlingi foi estudada por mais de um ano numa área endêmica de malária na BR-174 (Manaus/Boa Vista). Esta atividade foi documentada para demonstrar as mudanças estacionais na população e variação do ciclo nas estações do ano. São apresentadas as coletas mostrando o ciclo de picada dentro e fora das casas. O modelo foi constante na área estudada e verificou-se que a população de A. darlingi aumenta na estação seca. Com o aumento das chuvas há um declínio na população de anófeles e esta diminuição corresponde a um decréscimo estacional similar ao número de casos de infecção malárica

Malaria and its possible control on the island of Príncipe

BACKGROUND: Malaria can be eradicated from islands. To assess the prospects for eradication of malaria from the island of Príncipe in the Gulf of Guinea, we fitted a mathematical model to age-prevalence curves and thus obtained estimates of the vectorial capacity and of the basic reproductive number (R(0)) for malaria. METHODS: A cross-sectional malariological survey was carried out, in mid-1999, in six communities, comprising circa 17% of the total 6,000 population of the island. All houses in these communities were registered and their mode of construction recorded. Thick and thin blood films were prepared from all consenting individuals. Each individual was asked whether they possessed a mosquito net, whether they had slept under a mosquito net the previous night, whether they were allergic to chloroquine, and whether they had visited the main island of São Tomé since the beginning of the year. Outpatient records from March 1999 until the end of December 2000 were also examined and the age and place of residence of diagnosed cases noted. RESULTS: 203 (19.8%) of the 1,026 individuals examined were found to be infected with Plasmodium falciparum. By fitting the mathematical model of the Garki project to the age-prevalence curve we estimate that the basic reproductive number, R(0), on the island is approximately 1.6. Over a period of one year, a total of 1,792 P. falciparum cases reported to an outpatient facility at the island's hospital. Overall, 54% of the people interviewed slept under mosquito nets and were at reduced risk of infection. Conversely, people living in houses with openings between the top of the wall and the roof had higher risk of infection. CONCLUSION: This high incidence suggests that most of the malaria cases on the island attend the hospital and that treatment of these cases is an important factor reducing the effective rate of transmission. Providing that clinical cases are effectively treated, endemic malaria can probably be eliminated from the island mainly by reducing exposure to the vector with simple measures such as insecticide-treated nets and mosquito-proofing of dwellings. In contrast to traditional malaria eradication strategies, this would avoid the risk of malaria epidemics because the reduction in R(0 )should be sustainable

pre-gravid behaviour of female Anopheles gambiae from the islands of São Tomé and Príncipe, West Africa

BACKGROUND: Malaria prevalence differs between the two islands that comprise the archipelago of São Tomé and Príncipe. This may be due to differences in the biology of local Anopheles gambiae, the only vector on the islands. Survival rate and feeding frequency are two factors influencing vectorial capacity. Anophelines generally feed just once per gonotrophic (oviposition) cycle. Newly emerged insects, however, may feed two or more times during their first oviposition cycle thus increasing the likelihood of becoming infected. The reasons for multiple feeding are not clearly understood and it is still uncertain whether the behaviour is facultative or obligatory. We, therefore, determined survival and sporozoite rates, and examined the behaviour of An. gambiae from the two islands during their first gonotrophic cycle. METHODS: The wing size of 1,410, abdominal condition of 687, gonotrophic age and mated status of 7,264 female M form An. gambiae collected by light-trap, landing catch, resting outdoors or in copula, was determined from four sites in the archipelago. Sporozoite rates assessed by ELISA in 15,533 females from São Tomé and 2,111 from Príncipe were determined. RESULTS: Estimated survival rates ranged between 0.834-0.849 per day in São Tomé and 0.801-0.818 per day in Príncipe. Sporozoite rates of 0.63% in São Tomé were significantly higher than the 0.24% from Príncipe. Overall 49% of females mated on the second night after emergence before feeding, and 51% on the third night and thus fed before mating. The likelihood of mating before feeding increased with wing size. None of the 3,776 parous insects collected showed evidence of recent mating. All but two of the 198 females collected in copula had undeveloped ovaries. Mean wing sizes and the number of insects collected in a sentinel light-trap varied but the proportion of newly emerged insects in the collection did not. The estimated survival rate of the smallest insects was lower than other size groups, but the overall size distribution of each age group was normal. Parous insects were gonotrophically concordant. CONCLUSION: Differences in mosquito survival contributed to the lower sporozoite rates and endemicity of malaria on Príncipe compared to São Tomé. On both islands all newly emerged insects blood fed on the second night following emergence but only became gonotrophically active on the third night after emergence. Smaller insects had a higher 'mortality/emigration' rate than larger ones. We suggest that insufficiency of Juvenile Hormone until the third day of adult life is responsible for gonotrophic inactivity and that by partitioning mating between the second or third day after emergence females maximise their chances of out-crossing.publishersversionpublishe

Sex-specific and blood meal-induced proteins of Anopheles gambiae midguts: analysis by two-dimensional gel electrophoresis

BACKGROUND: Anopheles gambiae is the main vector of Plasmodium falciparum in Africa. The mosquito midgut constitutes a barrier that the parasite must cross if it is to develop and be transmitted. Despite the central role of the mosquito midgut in the host/parasite interaction, little is known about its protein composition. Characterisation of An. gambiae midgut proteins may identify the proteins that render An. gambiae receptive to the malaria parasite. METHODS: We carried out two-dimensional gel electrophoresis of An. gambiae midgut proteins and compared protein profiles for midguts from males, sugar-fed females and females fed on human blood. RESULTS: Very few differences were detected between male and female mosquitoes for the approximately 375 silver-stained proteins. Male midguts contained ten proteins not detected in sugar-fed or blood-fed females, which are therefore probably involved in male-specific functions; conversely, female midguts contained twenty-three proteins absent from male midguts. Eight of these proteins were specific to sugar-fed females, and another ten, to blood-fed females. CONCLUSION: Mass spectrometry analysis of the proteins found only in blood-fed female midguts, together with data from the recent sequencing of the An. gambiae genome, should make it possible to determine the role of these proteins in blood digestion or parasite receptivity