Effectiveness of Mosquito Magnet® trap in rural areas in the southeastern tropical Atlantic Forest

Traps are widely employed for sampling and monitoring mosquito populations for surveillance, ecological and fauna studies. Considering the importance of assessing other technologies for sampling mosquitoes, we addressed the effectiveness of Mosquito Magnet® Independence (MMI) in comparison with those of the CDC trap with CO2 and Lurex3® (CDC-A) and the CDC light trap (CDC-LT). Field collections were performed in a rural area within the Atlantic Forest biome, southeastern state of São Paulo, Brazil. The MMI sampled 53.84% of the total number of mosquitoes, the CDC-A (26.43%) and CDC-LT (19.73%). Results of the Pearson chi-squared test (χ2) showed a positive association between CDC-LT and species of Culicini and Uranotaeniini tribes. Additionally, our results suggested a positive association between CDC-A and representatives of the Culicini and Aedini tribes, whereas the MMI was positively associated with the Mansoniini and Sabethini as well as with Anophelinae species. The MMI sampled a greater proportion (78.27%) of individuals of Anopheles than either the CDC-LT (0.82%) or the CDC-A traps (20.91%). Results of the present study showed that MMI performed better than CDC-LT or CDC-A in sampling mosquitoes in large numbers, medically important species and assessing diversity parameters in rural southeastern Atlantic Forest.

Effect of diet composition on the development of the floodwater Mosquito Ochlerotatus (Ochletotatus) albifasciatus (Macquart) (Diptera: Culicidae) / Efecto de la composición de la dieta sobre el desarrollo del mosquito de inundación Ochlerotatus (Ochletotatus) albifasciatus (Macquart) (Diptera: Culicidae)

One important step for the colonization of Ochlerotatus albifasciatus (Macquart) is to determine the optimal conditions for larval rearing, which makes possible the development of experiments comprising larval rearing in the laboratory. In this research the effect of diet composition on the development of O.albifasciatus was studied. For this purpose, cohorts of 20 first instars were reared using five diets: 1:1 mix of yeast and TetraMin®, 1:1 mix of fine and coarse organic matter, grass cuts soaked in water for 1h or 24h before larvae incorporation, and 1:1:1 mix of grass cuts, fine organic matter and coarse organic matter. Survival was recorded for each cohort, while development time from first instar to pupa, and adult wing length were recorded for each individual. The effects of the diet on the observed traits were analyzed by one way ANOVA. Both survival and wing length were affected by diet, being significantly higher (79-100% and ~ 4.46 mm) on diets consisting of organic matter or organic matter plus grass than on those consisting of yeast plus TetraMin® or grass. Development time was not affected by the diet, although the shortest time (8.1 to 8.3 days) and lower variation between replicates were recorded when larvae were reared using organic matter or organic matter plus grass. Thus, it is concluded that the diets consisting of organic matter or a mix of it and grass are the most effective for O.albifasciatus rearing.

Un paso importante para la colonización de Ochlerotatus albifasciatus (Macquart) es conocer las condiciones óptimas para la cría de las larvas, lo cual además posibilita el desarrollo de experimentos en el laboratorio. En este trabajo se estudió el efecto de la dieta sobre el desarrollo de O. albifasciatus. Para ello se criaron cohortes de 20 larvas I utilizando cinco tipos de dietas: una mezcla 1:1 de levadura y TetraMin®, una mezcla 1:1 de materia orgánica fina y gruesa, gramíneas cortadas y sumergidas en agua 1h o 24h antes de incorporar las larvas, y una mezcla 1:1:1 de gramíneas cortadas, materia orgánica fina y materia orgánica gruesa. Para cada cohorte se registró la supervivencia, y para cada individuo, el tiempo de desarrollo desde larva I hasta pupa y la longitud del ala de los adultos. El efecto de la dieta sobre estas características se analizó mediante un ANOVA de una vía. Los resultados mostraron que la dieta afecta la supervivencia y la longitud del ala, obteniéndose los mayores valores de estas variables (79-100% y ~ 4,46 mm) con las dietas consistentes en materia orgánica o materia orgánica más gramíneas. El tiempo de desarrollo no estuvo afectado por la dieta, aunque el tiempo más corto (8,1-8,3 dias) y la menor variación entre réplicas se registraron al criar las larvas con materia orgánica o materia orgánica más gramíneas. Se concluye que las dietas consistentes en materia orgánica o una mezcla de ésta y gramíneas, son las más efectivas para la cría de O. albifasciatus.

Long-term storage and viability of Ochlerotatus albifasciatus (Diptera: Culicidae)

The viability of Ochlerotatus albifasciatus (Macquart) eggs stored at room temperature and at 5ºC was studied over 31 months. After 12, 18 and 31 months of storage, eggs were acclimatized at 22ºC for ten days, and then inundated twice every seven days. The effect of the storage period on the percentage of hatching was analyzed by one way ANOVA. Differences on the hatching response between the first and second flooding were analyzed by paired t-test. Differences on the hatching response between the two storage conditions were analyzed by Mann-Whitney rank test. Results showed that (1) Oc. albifasciatus eggs were able to survive and hatch over 31 months; (2) the percent hatching of eggs stored at 5ºC was higher than that of eggs stored at room temperature; and (3) low temperatures and long periods without water favor installment hatching.

Transmission dynamics of diurnally subperiodic lymphatic filariasis transmitted by Ochlerotatus (Finlaya) niveus in the Andaman & Nicobar Islands.

BACKGROUND & OBJECTIVE: In India diurnally subperiodic filariasis is prevalent only in the Nicobar district of Andaman and Nicobar Islands, with significant health problem. Sample surveys indicated that this form of filariasis is restricted to a small region of Nancowry group of islands with Ochlerotatus niveus as the vector. We therefore carried out a comprehensive study to assess the transmission dynamics of LF in Teressa island in Nicobar district in view of its control and evaluation of interventions. METHODS: Entomological studies were carried out for a period of twelve months covering all the seasons in the year, by means of man landing catches in Teressa Island, an endemic island for this form of filariasis. Parameters viz., the annual biting rate (ABR), annual infective biting rate (AIBR), annual transmission index (ATI), risk of infection index (RII) and annual transmission potential (ATP), which reflect the dynamics and intensity of transmission of filariasis, were estimated. Host efficiency of Oc. niveus was also assessed. RESULTS: The number of vectors biting a person in a year was estimated to be 21851, of which 107 were harbouring infective parasite. Risk of infection intensity was 0.02332. Every person in this study area was at the risk of receiving an estimated number of 22 infective stage larvae per year. The host efficiency index of Oc. niveus indicated that over 40 per cent of the microfilariae ingested were able to develop into infective stages. The ATP was 169 with evidence of year round transmission. The pattern of monthly transmission potential suggested that the intensity of transmission was high during summer months. INTERPRETATION & CONCLUSION: Perennial transmission of subperiodic Wuchereria bancrofti in the typical forest ecosystem was evident in Teressa Island with transmission parameters suggesting that summer is a high risk season for transmission. Personal protection measure is the method of choice to protect from the risk of infection, because of day biting, exophilic and exophagic behaviour of the vector and larvae are not amenable to larvicidal measures. An alternative method to control the transmission would be to use selective or periodic mass chemotherapy to reduce the parasite load in this community.

Paridade de Ochlerotatus scapularis em condições de laboratório e campo / Parity of Ochlerotatus scapularis in laboratory and field conditions

OBJETIVO: Identificar o estado de paridade em fêmeas de Ochlerotatus scapularis de campo e obtidas em condições de laboratório. MÉTODOS: Para obtenção das fêmeas de campo, foram realizadas coletas quinzenais no Vale do Ribeira utilizando-se a técnica da aspiração manual, de abril de 2003 a março de 2004. Em laboratório, 100 fêmeas (F1) de Ochlerotatus scapularis foram mantidas e observadas individualmente anotando-se o número de repastos realizados, duração do ciclo gonotrófico, tempo de sobrevivência e número de ovos colocados. A observação do estado de paridade e desenvolvimento ovariano foi feita pela dissecção dos ovários de 90 fêmeas por coleta, e de todas as fêmeas mantidas em laboratório. RESULTADOS: Das 100 fêmeas mantidas em laboratório e dissecadas, o diagnóstico de condição de paridade conferiu com os resultados constatados em 55 por cento dos casos, sendo subestimados em 37 por cento e superestimados em 2 por cento. Ainda em laboratório, de 106 ciclos gonotróficos completados, cerca de 55 por cento das fêmeas necessitaram de mais de um repasto sangüíneo antes de ovipor. A sobrevivência observada em laboratório foi de até 26 dias para a espécie. Foram dissecadas 1.180 fêmeas de Ochlerotatus scapularis do campo: 418 (35,4 por cento) foram consideradas nulíparas, 655 (55,5 por cento) uníparas, 46 (3,9 por cento) como bíparas e 61 (5,2 por cento) não puderam ser avaliadas. Noventa fêmeas apresentavam-se na fase III-V de Christophers e Mer. CONCLUSÕES: Pode-se confirmar a hipótese de discordância gonotrófica, com base nas observações de fêmeas de Ochlerotatus scapularis no campo e laboratório.

Variation in the hatching response of Ochlerotatus albifasciatus egg batches (Diptera: Culicidae) in temperate Argentina

Egg hatching of winter-collected Ochlerotatus albifasciatus was studied for six months. Batches of eggs were divided into two groups, one of them was stored in the laboratory at 23ºC and 12:12 photoperiod, and the other in the field under dead leaves. Every month, from July to December, eggs from the two groups were flooded under both laboratory and field conditions. Unhatched eggs were returned to the original condition and flooded two more times separated by ten-day intervals. Results show that egg diapause is expressed in different intensities, not only on eggs exposed to different conditions but also in those exposed to the same condition, even when they were laid by the same female. Successive inundations yielded incomplete hatches of eggs, and favored the hatching response in the next flooding. Low environmental temperatures before and during the flooding depressed hatching response. This shows that eggs need a warm period before flooding as well as warm temperatures during flooding, to hatch. As drought period was longer hatching response increased, but this was also accompanied by warmer environmental conditions. The experiment performed in laboratory did not show that increment. Field studies showed that a layer of dead leaves protected eggs from extreme temperatures.

Preliminary evidence of association between species of mosquitoes in Atlantic forest of Santa Catarina State, (Diptera: Culicidae)

Foi observado coeficiente de associação positivo (afinidade) entre Runchomyia reversa and Anopheles cruzii e alto (0,38) índice de associação, provavelmente devido a similaridade entre os criadouros (bromélias) e aos hábitos de pouso, e alto (0,92) índice de associação entre Oc. scapularis e Wyeomyia incaudata, com baixo coeficiente de associação.

Paridade e desenvolvimento ovariano de Ochlerotatus scapularis (Diptera Culicidae) em condições de laboratório e de campo na região do Vale do Ribeira, São Paulo, Brasil / Parity and ovarian development of Ochlerotatus scapularis (Diptera: Culicidae) in laboratory and field conditions in Vale do Ribeira region. São Paulo, Brazil

Objetivo. Identificar o estado de paridade em fêmeas de Ochlerotatus scapularis em condições de laboratório e campo. Das fêmeas coletadas em campo, determinar o grau de paridade considerando sua importância epidemiológica como possível transmissor de patógenos. Métodos. O trabalho foi dividido em duas partes: no campo foram realizadas coletas quinzenais no Vale do Ribeira de abril de 2003 a março de 2004, utilizando-se a técnica da aspiração manual. No laboratório, 100 fêmeas (F1) de Ochlerotatus scapularis foram criadas e observadas individualmente anotando-se o número de repastos por elas realizados, duração do ciclo gonotrófico e número de ovos colocados. A observação do estado de paridade e desenvolvimento ovariano foi feita através da dissecação dos ovários de 90 fêmeas, por coleta, e de todas as fêmeas criadas. Resultados. Das 100 fêmeas mantidas em laboratório e dissecadas, o diagnóstico de condição de paridade conferiu com os resultados constatados em 55 por cento dos casos, sendo subestimados em 37 por cento e superestimados em 2 por cento. Ainda em laboratório, de 106 ciclos gonotróficos complementados, cercade 55 por cento das fêmeas necessitaram de mais de um repasto sangüíneo antes de ovipor, indicando uma possível discordância gonotrófica para a espécie. Sob condições laboratoriais observou-se uma sobrevivência de até 26 dias para a espécie. Foram dissecadas 1180 fêmeas de Oc. scapularis do campo: 418 (35,4 por cento) foram consideradas nulíparas, 655 (55,5 por cento) uníparas, 46 (3,9 por cento) como bíparas e 61 (5,2 por cento) não puderam ser avaliadas. Foi observado que 90 fêmeas apresentavam-se na fase III-V de Christopher e Mer, reforçando a discordância gonotrófica. A variável estado de paridade variou ao longo do ano. Conclusões: Observando fêmeas de Oc. scapularis no campo e laboratório, confirmamos a hipótese de discordância gonotrófica.