Observações sobre atividade de mosquitos Culicidae, em mata residual no Vale do Ribeira, S. Paulo, Brasil

Relatam-se observações sobre o ciclo diário de atividade, por parte de mosquitos Culicidae de mata residual, em área de ambiente intensamente modificado por exploração agropecuária, no Vale do Ribeira, Estado de São Paulo, Brasil. Foram levadas a efeito, com ritmo bimensal, capturas ininterruptas de vinte e cinco horas com isca humana, além de coletas simultâneas com ardilhas tipo Shannon em ambiente intra e extra florestal. Os resultados evidenciaram o caráter diurno e noturno das espécies mais freqüentes, com destaque para o Ae. scapularis e Ae. serratus que, embora com atividade classificada como diurna, mantêm atuação apreciável também durante a noite. Em relação ao primeiro acrescenta-se a ocorrência de nítido pico endocrepuscular vespertino, e a manutenção de sua presença no meio extraflorestal. De maneira geral, essas duas espécies mostram-se presentes todos os meses do ano, com dominância de Ae. scapularis sobre Ae. serratus somente no mês de junho, ocasião porém em que aquele sobrepuja a este de maneira considerável. Tais feições caracterizam quadro que permite atribuir àquele mosquito maiores oportunidades de contato com a população humana e, por conseguinte, papel importante na veiculação de arboviroses, em especial modo, de encefalites.

Observações sobre atividade de mosquitos Culicidae em matas primitivas da planície e perfis epidemiológicos de vários ambientes no Vale do Ribeira, São Paulo, Brasil

Observou-se o ciclo diário da atividade culicídea em ambiente primitivo das florestas perenifólias higrófilas da planície, compreendendo tanto a quaternária como a de transição, do Sistema da Serra do Mar, no Vale do Ribeira, Estado de São Paulo (Brasil). Em cada floresta foram realizadas capturas mensais de 25 horas ininterruptas com o emprego de isca humana, bem como a utilização de armadilha tipo Shannon operadas dentro e fora do ambiente florestal. Registrou-se a dominância de An. cruzii embora não de maneira tão acentuada quanto a verificada na mata da encosta, mas que se manteve durante todos os meses do ano. Juntamente com Ae. serratus e An. bellator, esse mosquito manteve-se continuamente em atividade, na isca humana, durante todo o período das 24 horas. Cx. sacchettae e Ps. ferox revelaram ciclo nictimeral caracteristicamente noturno para o primeiro e diurno para o segundo. A influência crepuscular evidenciou-se com a ocorrência de nítidos picos endocrepusculares para An. cruzii, An. bellator e o caráter eocrepuscular para Cx. sacchettae. Aquelas duas espécies de Kerteszia confirmaram a presença de ritmo paracrepuscular. O Ae. scapularis ocorreu nas coletas efetuadas no aberto, ou seja, no meio extraflorestal onde não se registrou a presença de Ae. serratus. Comparando-se os resultados destas observações com aqueles obtidos no ambiente modificado e na mata da encosta, pôde-se traçar o perfil culicídeo dos quatro locais notando-se a ocorrência de nítida sucessão na fauna, conseqüente às alterações introduzidas pelo homem. Ae. scapularis e Cx. ribeirensis mostraram capacidade de adaptação ao ambiente humano, com a conseqüente importância epidemiológica que desse fenômeno se pode deduzir.

Biting activity of Aedes scapularis (Rondani) and Haemagogus mosquitoes in Southern Brazil (Diptera: Culicidae)

The biting activity of a population of Aedes scapularis (Rondani), Haemagogus capricornii Lutz and Hg. leucocelaenus (Dyar and Shannon) in Southern Brazil was studied between March 1980 and April 1983. Data were obtained with 25-hour human bait catches in three areas with patchy residual forests, named "Jacaré-Pepira", "Lupo" Farm, and "Sta. Helena" Farm, in the highland region of S. Paulo State (Brazil). Data obtained on Ae. scapularis were compared with those formerly gathered in the "Ribeira'' Valley lowlands, and were similar, except in the "Lupo" Farm study area, where a precrepuscular peak was observed, not recorded at the "Jacaré-Pepira" site or in the "Ribeira" Valley. In all the areas this mosquito showed diurnal and nocturnal activity, but was most active during the evening crepuscular period. These observations support the hypothesis about the successful adaptation of Ae. scapularis to man-made environments and have epidemiological implications that arise from it. As for Haemagogus, results obtained on the "Lupo" and "Sta. Helena" regions agree with previous data obtained in several other regions and show its diurnal activity. The proximity of "Lupo" Farm, where Hg. capricornii and Hg. leucocelaenus showed considerable activity, to "Araraquara" city where Aedes aegypti was recently found, raises some epidemiological considerations about the possibility of urban yellow fever resurgence.

Biologia de Anopheles (Kerteszia) neivai H., D. & K., 1913 (Diptera: Culicidae) en la costa Pacífica de Colombia: II. Fluctuación de la población adulta

En la localidad de Charambirá, situada en el município de Istmina (Chocó) en la costa Pacífica de Colombia, se presenta un problema de malaria endémica asociada con grandes poblaciones de mosquitos Anopheles del subgénero Kerteszia (A. neivai). Estos se crían en las colecciones de agua formadas por plantas epífitas de la família Bromeliaceae, que son muy abundantes en los árboles de mangle. En esa localidad se estudiaron: fluctuación poblacional y algunos aspectos ecológicos y etológicos de los adultos de esa especie de mosquito, con el objetivo de determinar su papel en la transmisión de malaria. Todos los mosquitos fueron colectados por cebos humanos. Los picos máximos de actividad ocurrieron en las horas crepusculares de la mañana y de la tarde (5:30 a 6:30 y 18:00 a 19:00 horas). En el período nocturno la actividad intradomiciliar fue baja y no hubo ninguna durante el día. El estado gonadotrófico de las hembras colectadas durante nos picos de actividad, mostró la existencia de dos poblaciones de mosquitos: una, en su mayoría individuos jóvenes que buscan su alimento en las horas de la tarde y la otra compuesta por individuos mas longevos, que buscan su alimento en la mañana. El estudio de la variación estacional mostró que las poblaciones son bajas en los meses de poca precipitación, pero a medida que aumenta el índice pluviométrico, aumenta el número de mosquitos. Se discute la relación que existe entre la presencia de los mosquitos y la prevalencia de malaria humana; se sugiere que A. neivai puede ser el responsable de la transmisión de malaria en la zona estudiada.

Peroral susceptibility of Aedes albifasciatus and Culex pipiens complex mosquitoes (Diptera: Culicidae) from Argentina to western equine encephalitis virus

The transmission cycle of western equine encephalitis (WEE) virus in South America is unknown. A WEE virus strain was isolated from Aedes albifasciatus in Argentina during the WEE epizootic of 1982-83. Also, Culex pipiens from Argentina was reported to be able to transmit WEE virus experimentally, but other results indicate that Cx. pipiens from the USA is refractory to this virus. We determined the susceptibility of Argentina strains of Ae. albifasciatus and Culex pipiens complex mosquites to infection by WEE virus by the oral route. Adult females were fed on chicks infected with a WEE virus strain isolated in Cordoba Province, Argentina, or were fed on a blood/virus suspension. Each mosquito ingested between 10(1.6) to 10(6.4) vero cell plaque-forming units of virus. Each of 28 Ae. albifasciatus was positive for virus from the fourth day postfeeding, and there was evidence for virus replication. In contrast, 0/44 Cx. p. quinquefasciatus and only 1/15 Cx. p. pipiens was positive. Aedes albifasciatus is susceptible to infection by WEE virus and should be considered a potential vector of this virus in Argentina. Both subspecies of Cx. pipiens are refractory to peroral infection by WEE virus and probably do not play a role in the WEE virus cycle in Argentina.

Nota sobre culicídeos (Diptera: Culicidae) da bacia do rio Purus, Acre, Amazônia (Brasil)

Foram feitas coletas de mosquito (Diptera: Culicidae) na área do projeto de Colonização Pedro Peixoto, no Estado do Acre, Brasil. Obteve-se um total de 4.588 exemplares pertencentes a 53 espécies ou grupos. Salienta-se a ocorrência de Anopheles (Nyssorhynchus) oswaldoi.

Studies on mosquitoes (Diptera: Culicidae) and anthropic environment: 2 - Immature stages research at a rice irrigation system location in South-Eastern Brazil

A relation between a rice irrigation system and mosquito breeding was established in a study undertaken at the Ribeira Valley Experimental Station, from January through December 1992. Flooding favoured Anopheles (Nyssorhynchus) and Culex (Melanoconion) species, while empty paddies condition were propitious to Aedes scapularis and Culex (Culex) species. Compared with a more primitive area of the same region, several species showed high a degree of adaptation to the anthropic environment. Among them, Anopheles albitarsis, a potential malaria vector that breeds in the irrigation system, has shown immature stage production thirteen times higher than at the natural breeding sites. In addition, Ae. scapularis, An. oswaldoi, Cx. bastagarius, and Cx. chidesteri presented high levels of synanthropy.

Studies on mosquitoes (Diptera: Culicidae) and anthropic environment: 3- Survey of adult stages at the rice irrigation system and the emergence of Anopheles albitarsis in South-Eastern, Brazil

A study of adult Culicidae ecology was carried out from January 1992 through January 1993 at the rice irrigation system of the Ribeira Valley Experimental Station. The adaptation of Anopheles albitarsis to the anthropic environment became evident through the adult collections made at its various habitats represented by the irrigation system and the edge of the residual pond, as well as at those made within the local patchy residual woods. Other potential disease vectors were prevalent in the irrigated system too. There were Aedes scapularis, Culex nigripalpus and Cx. ribeirensis that were collected at various habitats. Remarkable differences among their prevalences were obtained such as between the natural forest and anthropic environments. In the former An. albitarsis was practically non-existent, thus suggesting that it might be considered as eusynathropic. As the populations of other species seemed to increase in the anthropic environment, they may be regarded as hemisynanthropes. Observations suggest the hypothesis that the development of irrigated land may be a factor in the emergence of An. albitarsis, and some other species, as well as the possibility of an increase in the transmission of mosquito-borne diseases such as malaria.

Studies on mosquitoes (Diptera: Culicidae) and anthropicenvironment: 5- Breeding of Anopheles albitarsis in flooded rice fields in South-Eastern Brazil

Studies on breeding Anopheles albitarsis and association with rice growth in irrigated paddy fields were carried out during the rice cultivation cycle from December 1993 to March 1994. This period corresponded to the length of time of permanent paddy flooding. Breeding occurred in the early stage up until five weeks after transplantation when rice plant height was small. That inverse correlation may give potential direction to control measures.

Studies on mosquitoes (Diptera: Culicidae) and anthropic environment: 9- Synanthropy and epidemiological vector role of Aedes scapularis in South-Eastern Brazil

Behaviour comparisons of Aedes scapularis and Ae. serratus are presented. Results were obtained by sampling Aedes adult mosquitoes at several places in the rural anthropic environment in the Ribeira Valley region of S. Paulo State, Brazil. Aedes dominance was shared by those two species, but Ae. scapularis Sshowed a clear tendency to frequent the modified environment, while Ae. serratus was to be found in the more preserved ones, here represented by the vestigial patchy forests. Regarding the open cultivated land and the dwelling environments, Ae. scapularis preponderates. Considering the regional developmental phases, this mosquito showed a remarkable increase in the modified environment differently from Ae. serratus that underwent a considerable decrease in migrating from the forest to the anthropic environment. As a consequence of these results it is reasonable to conclude that Ae. scapularis may be considered as an epidemiologically efficient vector and that it quite probably played this role in the Rocio encephalitis and other arbovirus epidemics.

Studies on mosquitoes (Diptera: Culicidae) and anthropic environment: 10- survey of adult behaviour of Culex nigripalpus and other species of Culex (Culex) in South-Eastern Brazil

A survey of adult behaviour of Culex (Culex) species was carried out from August 1992 through December 1993 in a human modified (anthropic) environment in the Ribeira Valley, S.Paulo State, Brazil. Culex nigripalpus dominated the catches at several sites and it's tendency to increase in the anthropic environment became quite clear. Nevertheless no high level of synanthropy was demonstrated. So it seems that the mosquito may have a restricted role in natural arbovirus cycles. Nonetheless, Cx. nigripalpus must be considered a potential vector of arboviruses, especially St. Louis encephalitis virus outside dwellings.

Determinação das fontes alimentares de Anopheles aquasalis (Diptera: Culicidae) no Estado do Rio de Janeiro, Brasil, pelo teste de precipitina

Anopheles aquasalis é um mosquito ora encarado como antropofílico, ora como zoofílico ou eclético. Realizou-se estudo em Guapimirim, Estado do Rio de Janeiro, de maio a novembro de 1992, com o intuito de se verificar a fonte alimentar preferida desse anofelino através de teste imunológico de precipitina. De 1.366 fêmeas capturadas em abrigos naturais, 725 estavam ingurgitadas. O conteúdo digestivo de apenas 473 delas reagiu no teste de precipitina, sendo que em 75,3% dos casos foi identificada apenas uma fonte alimentar. Mais da metade dessas fêmeas havia se alimentado em boi (52,2%), enquanto poucas tinham sugado homem (1,1%). Por outro lado, 24,7% dos espécimes haviam se alimentado em mais de uma fonte sangüínea, principalmente boi e cavalo. Conclui-se que An. aquasalis é zoófilo nessa região do País, utilizando grande variedade de hospedeiros, porém preferindo se alimentar em animais de grande porte, especialmente o boi e cavalo.

Encontro de criadouros de Aedes scapularis (Diptera: Culicidae) em recipientes artificiais

Relata-se o encontro de criadouros de Aedes scapularis em recipientes artificiais abandonados nos Municípios de Ilha Comprida e de Pariquera-Açu, Estado de São Paulo (Brasil). Foram coletadas 270 (250 larvas e 20 pupas) formas imaturas, o que permitiu levantar a hipótese de adaptação secundária desse mosquito ao ambiente antrópico. Este caracteriza-se pela diminuição de locais viáveis para instalação de criadouros no solo e, ao mesmo tempo, pelo incremento do número de recipientes artificiais os quais poderiam ser utilizados para a oviposição. Estima-se que, nesta parte da região Sudeste do Brasil, possam ocorrer implicações epidemiológicas em relação à transmissão de encefalite.

LARVICIDAL ACTIVITY OF Bacillus sphaericus 2362 AGAINST Anopheles nuneztovari, Anopheles darlingi AND Anopheles braziliensis (DIPTERA, CULICIDAE)

In this present study, preliminary data was obtained regarding the mortality rate of the Amazonian anophelines, Anopheles nuneztovari, Anopheles darlingi and Anopheles braziliensis when subjected to treatment with Bacillus sphaericus strain 2362, the WHO standard strain. Initially, experiments were conducted to test the mortality rate of the three species of anopheline larvae. The third larval instar of An. nuneztovari and the second and third larval instars of An. darlingi proved to be the least susceptible. In other experiments, the same three mosquito species were tested with the standard strain 2362, An. nuneztovari was the least susceptible to this insect pathogen, while An. braziliensis was the most susceptible. This latter species showed a difference in the level of LC50 concentration, when compared to the former, of 2.4, 2.5 and 1.8 in readings taken 24, 48 and 72 hours after exposure to the bacillus.

INVENTORY OF MOSQUITOES (DIPTERA: CULICIDAE) IN CONSERVATION UNITS IN BRAZILIAN TROPICAL DRY FORESTS

In Brazil, most studies of the Culicidae family are concentrated in rainforest regions. As such, there is a lack of knowledge regarding the diversity of Culicidae in regions with different climatic and vegetational characteristics. The aim of this study was to compile an inventory of Culicidae in protected areas of the semi-arid region of the state of Minas Gerais, Brazil, in order to better understand the diversity of the family within this region. The study was conducted across four protected areas in the northern region of the state, in tropical dry forest (TDF) fragments. Sampling methods included Shannon trap and CDC light trap, as well as active collection. A total of 11,219 mosquito specimens were collected between August 2008 and July 2012, belonging to 11 genera and 45 species; 15 new records for the state of Minas Gerais were registered, as well as 26 new records for semi-arid regions within the state. The high number of new Culicidae records in this region demonstrates the importance of inventory studies for increasing the knowledge of culicid biodiversity in Minas Gerais, and in particular within semi-arid regions of the state.