Diversidade genética de Wolbachia Pipientis em populações de culicídeos vetores e no parasito Wuchereria Bancrofti / Genetic diversity of Wolbachia pipientis in populations of vector mosquitoes and the parasite Wuchereria bancrofti

A bactéria endossimbionte Wolbachia tem sido sugerida como mecanismo de controle de insetos vetores e alvo para o tratamento das filarioses. Nesse contexto, estudos sobre a prevalência de Wolbachia em populações de vetores de campo, a análise da sua densidade em insetos sob diferentes condições fisiológicas e a investigação da diversidade genética da bactéria dentro e entre diferentes populações de vetores e em pacientes filarêmicos são relevantes. O presente estudo teve como objetivos: determinar o percentual de infecção em Culex quinquefasciatus e Aedes albopictus coletados em diferentes áreas da RMR - PE - BR; descrever a diversidade dos genes ftsZ e wsp nas linhagens de Wolbachia encontradas tanto nos vetores citados quanto nos vermes filariais coletados de pacientes microfilarêmicos da região; como também comparar a densidade da bactéria em duas populações de C. quinquefasciatus do estado de PE, uma susceptível e outra resistente a temefós. Nossos resultados mostraram que o simbionte Wolbachia está presente em 100 por cento dos vetores analisados quando diagnosticados pelo método de PCR seminested, o qual se mostrou mais eficiente que a PCR convencional. Quanto à densidade do endossimbionte, as fêmeas de C. quinquefasciatus resistentes a organofosforados de Santa Cruz do Capibaribe, Sertão - PE, apresentaram a densidade média, cerca de sete vezes maior que às fêmeas susceptíveis de Peixinhos, RMR - PE, confirmando dados encontrados na literatura. Isto sugere que mosquitos resistentes apresentam maior dificuldade para controlar a densidade do endossimbionte provavelmente pelo custo biológico associado à resistência. Em relação à diversidade genética, os dois genes estudados não mostraram nenhuma variação nas populações observadas. A análise de outros marcadores pode ajudar a esclarecer a relação entre hospedeiros e endossimbionte dando maior suporte ao uso de Wolbachia no desenvolvimento de novas estratégias de controle e tratamento de doenças transmitidas por vetores.

Laboratory studies on the effect of inorganic fertilizers on survival and development of immature Culex quinquefasciatus (Diptera: Culicidae).

BACKGROUND & OBJECTIVES: Studies were conducted to determine the effect of ammonium sulfate (AM) and muriate of potash (MOP) fertilizers on survival and development of immature stages of Culex quinquefasciatus Say, a major vector of Bancroftian filariasis in Africa. METHODS: Twenty I instar larvae each were added in four doses of each fertilizer dissolved in one litre of deionised water and in one litre of deionised water as a control in replicates of five. The larvae were monitored every morning throughout their life and the numbers of each instar surviving were recorded. The experiments were discontinued when all the larvae had died or emerged into adults. RESULTS: An analysis of variance test and Tukey's HSD test revealed a significant impact of fertilizers on survival and development of aquatic stages of Cx. quinquefasciatus. Ammonium sulfate accounted for up to 40% mortality rate, and one week delay in development time and this effect was both instar and dose dependent. None of the MOP dosages had significant impact on survival of immatures of Cx. quinquefasciatus and only the higher dosages showed significant impact on development time but in significantly lower magnitudes compared with similar dosages of ammonium sulfate. INTERPRETATION & CONCLUSION: These findings demonstrate the toxic effect of fertilizers on immature stages of Cx. quinquefasciatus contrary to field observations.

Larval susceptibility of Ajuga remota against anopheline and culicine mosquitos.

The objective of the present study is to determine the bioefficacy of different crude extracts of Ajuga remota against anopheline and culicine larvae. Larval susceptibility of crude carbon-tetrachloride, methanol and petroleum-ether extracts of Ajuga remota leaves was observed against the malaria vector, Anopheles stephensi and the filariasis vector, Culex quinquefasciatus. Among the extracts tested, petroleum-ether extract was the most effective with LC50 values of 0.033% after 24 hours and 0.029% after 48 hours of treatment against the larvae of Anopheles stephensi. In the case of the larvae of Culex quinquefasciatus, the carbon-tetra-chloride extract exhibited maximum efficacy with LC50 values of 0.043% after 24 hours and 0.026% after 48 hours of exposure, respectively. It is, therefore, concluded that Ajuga remota can be applied as an ideal larvicide against An. stephensi and Cx. quinquefasciatus.

A comparison of two Brazilian populations of Culex quinquefasciatus (Say, 1823) from endemic and non-endemic areas to infection with Wuchereria bancrofti (Cobbold, 1877)

Culex quinquefasciatus is known to be an efficient insect host of Wuchereria bancrofti. In Brazil Cx. quinquefasciatus is widely distributed throughout the country and is often abundant in and around human habitations. In contrast, Bancroftian filariasis is limited to three foci in Brazil. Experiments were undertaken to compare the vector capacities of Cx. quinquefasciatus originating from Maceio (Alagoas), one of the endemic areas of W. bancrofti infection in Brazil, and Belo Horizonte (Minas Gerais), a non endemic area. Laboratory-reared Cx. quinquefasciatus were dissected 20 days after blood feeding on microfilaraemic patients. Survival rates and the number of infective larvae that developed did not differ in female mosquitoes of different origins. Thus both populations of Culex were susceptible to infection with W. bancrofti.

Anopheles donaldi incriminated as a vector of periodic Brugia malayi in Grik, Perak, Malaysia.

Studies were carried out to observe the species composition of mosquitos and to determine the vectors responsible for the transmission of filariasis in Grik, Perak, Malaysia. A total of 2,155 mosquitos belonging to 7 genera and 30 species were collected. Anopheles donaldi comprised 24.1% of the collection. Twelve out of 519 An. donaldi were infected with L3 larvae of Brugia malayi. The peak biting time was around 23.00-24.00 hours. The infective bites per month ranged from 0 to 6.3.

Effect of ivermectin on survival and fecundity of culex pipiens the vector of wuchereria bancrofti in Egypt

The effect of two different doses of ivermectin on the survival and fecundity of Culex pipiens was evaluated. Female mosquitoes [50 in each group, same age and generation] were fed once on blood from ivermectin-treated rabbits. Comparative treatments consisted of two different doses of ivermectin [0.1 mg or 0.4 mg/kg of body weight] and mosquito groups were fed on the rabbits at 3 days and 10 days post-treatment, respectively. Mosquitoes were maintained with 10% sucrose solution at 25C and 70% relative humidity. Observations were made at 7, 10, 15, 20, 25 and 30 days post-feeding. These results provided new information about the effect of ivermectin on the vector of lymphatic filariasis and added a new dimension to the use of ivermectin in filariasis control

Recent advances in vector control in filariasis.

Three factors are involved when vector control is incorporated into an integrated control program for filariasis: (1) the vector species or species complex of each filarial worm; (2) type of control measures employed; (3) pesticide application. Recent advances in vector control in filariasis include the use of bed nets, environmental manipulation, insecticides and biological control. Three promising advances in vectrol control are the use of pathogenic bacteria such as Bacillus thuringiensis H-14 and B. sphaericus, juvenile hormone mimics or insect growth regulator (IGR) and predatory crustaceans.

Mosquito age as a factor influencing the transmission of wuchereria bancrofti

Two mosquito Species; Culex pipiens and Aedes caspius of different ages were experimentally infected with moderate microfilarial densities of Wuchereria bancrofti and examined for their vector potential to transmit this parasite. Tested age groups of Cx. pipiens supported the development of the infective stage of the parasite [L3] but those of Ae. caspius arrested its development especially aged mosquitoes. For Cx. pipiens, infection rates and the mean number of microfilaria [mf] were found decreased with insect age groups while their survival was not affected. Also, proportion of mosquitoes harbouring L3 of the parasite was quite similar for the examined age groups, however; the 4 days-old group was the highest. On the other hand, Ae. caspus capability to respond against W. bancrofti Was decreased in older mosquitoes. The observed results may indicate certain influence of mosquito aging on the development of W. bancrofti which differ according to mosquito species

Primer caso de Microfilariasis de ocurrencia fatal en Santa Cruz-Bolivia / The first of case microfilariasis probably fatal in Santa Cruz-Bolivia

Se presenta el primer caso de Microfilariasis patogena probable Mansonella Ozzardi, diagnosticado por estudio Histopalogico, en un nino de 12 anos de edad, procedente de la ciudad de Santa Cruz, con un cuadro clinico atipico y desenlace fatal

A cost benefit analysis of fish culture strategy towards the control of mansonioides in Shertallai, Kerala state.

The cost benefit analysis of fish culture as a means for vector control towards the containment of Brugian filariasis in Shertallai, a highly endemic tract for this disease in Kerala was carried out. While the financial gain accrued to the community was to the tune of Rs. 1,82,052 in ponds (under monoculture) with Chinese grass carp from 763 ponds, it was Rs. 1,83,740 from 1000 ponds under polyculture with Catla catla, Cyprinus carpio, Labeo rohita, Labeo fimbriatus, Cirrhina mrigala and Ctenopharyngodon idella (Chinese grass carp). Monoculture with Giant gourami (Osphronemous goramy) fetched an income of Rs. 7,654 to the community from 128 ponds. A marked reduction in weed reinfestation/vector breeding was observed in ponds under fish culture than other without fishes. The study clearly indicates that fish culture is an ideal strategy for Mansonioides control as it can bring perceptible benefits to the community.

Evaluation of RNA rich fraction of Litmosoides carinii in induction of protection in infected rats.

The RNA rich fraction of adult L. carinii worms was evaluated in evoking a protective response in infected rats. The RNA immunization was seen to be effective in limiting the microfilaraemia in peripheral blood as well as the adult worm burden. The antibodies to both RNA antigen and adult worm antigen were high in this group of animals at the peak of infection. The RNA immunization was seen to evoke hyperresponsiveness in lymphocytes to mitogens like adult worm antigen, PHA and Con A.

Weedivorous fishes for the control of vectors of Malayan filariasis.

An attempt was made to assess the efficacy of phytophagous fishes viz., Ctenopharyngodon idella, the Chinese grass carp and Osphronemus goramy, the giant gourami in the control of mansonioides mosquitoes by checking the growth of aquatic weeds which support their breeding. When C. idella and O. goramy were used in monoculture 80.21 and 81.25 per cent of the ponds were kept free from weeds. With polyculture using grass carp in combination with other varieties of carps, only 70.10 per cent of the ponds were kept out from the reinfestation of weeds. Even in the reinfested ponds, there was significant reduction (P less than 0.05) in vector breeding in all the three types of piscicultures, as compared to the control ponds. The utility of weedivorous fishes in the elimination of aquatic weeds and thereby breeding of vectors of Malayan filariasis was thus demonstrated.

Effectiveness of repellent/insecticidal bars against malaria and filariasis vectors in peninsular Malaysia.

Field tests were conducted to compare the degree of protection from bites of Mansonia species and Anopheles maculatus by applying two repellent/insecticidal bars, MOSBAR and MOSKIL, to exposed arms and legs. Human test subjects were exposed to natural populations of mosquitos for an 8-hour night time period while using the repellent/insecticidal bars. MOSBAR gave good protection against the bites of Mansonia and An. maculatus. MOSKIL was effective against An. maculatus but not against Mansonia. High mortality was observed among the mosquitos collected from human test subjects treated with the repellent/insecticidal bars. Use of MOSBAR in terms of cost-effectiveness and safety by field and health workers entering into malaria and filariasis endemic areas is discussed.