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At least 1,261 records · Page 70Linked to original sources
PubMed2001

Laboratory evaluation of two native fishes from tropical North Queensland as biological control agents of subterranean Aedes aegypti.

The ability of 2 freshwater fishes, eastern rainbow fish Melanotaenia splendida splendida and fly-specked hardyhead Craterocephalus stercusmuscarum stercusmuscarum, native to North Queensland to prey on immature Aedes aegypti was evaluated under laboratory conditions. The predation efficiency of the 2 species was compared to the exotic guppy, Poecilia reticulata, which is commonly used as a biological control agent of mosquito larvae. Of the 3 fish species tested, M. s. splendida was shown to be the most promising agent for the biological control of Ae. aegypti that breed in wells. Melanotaenia s. splendida consumed significantly greater numbers of immature Ae. aegypti than P. reticulata, irrespective of developmental stage or light conditions. Unlike C s. stercusmuscarum, M. s. splendida could be handled, transported, and kept in captivity for extended periods with negligible mortality. However, M. s. splendida was also an efficient predator of Litoria caerulea tadpoles, a species of native frog found in wells during the dry season. This result may limit the usefulness of M. s. splendida as a biological control agent of well-breeding Ae. aegypti and suggests that predacious copepods, Mesocyclops spp., are more suitable. However, the use of M. s. splendida as a mosquito control agent in containers that are unlikely to support frog populations (e.g., aquaculture tanks and drinking troughs) should be given serious consideration.

Aedes↗
PubMed2004

Larvicidal and mosquitocidal extracts, a coumarin, isoflavonoids and pterocarpans from Neorautanenia mitis.

The present study aimed to evaluate extracts and compounds from tubers of Neorautanenia mitis against the malaria- and filariasis-transmitting mosquitoes, Anopheles gambiae and Culex quinquefaciatus, respectively. The extracts exhibited activity against larvae of A. gambiae and C. quinquefaciatus mosquitoes, and were also active against adult A. gambiae mosquitoes. The active extracts yielded the coumarin derivative pachyrrhizine, the isoflavonoids neotenone and neorautanone, and the pterocarpans neoduline, nepseudin and 4-methoxyneoduline as the active constituents. The activity of the crude extracts was at about the same magnitude as that of the constituent natural products, the latter's efficacy being almost at the same level for all the isolated compounds. The mosquitocidal activities of the pure compounds were comparable to those of the standard mosquitocides deltamethrin and alphacypermethrin. These findings corroborate traditional insecticidal application of N. mitis and the results can be extended for the control of mosquitoes especially at breeding sites.

Animals↗
PubMedDate not supplied

Viral encephalitis of public health significance in India: current status.

Japanese encephalitis (JE) and rabies are 2 viral encephalitis that are of public health importance in India. JE is a zoonosis with the primary cycle occurring in arthropods (mosquito vectors) and vertebrate animals (primarily the pig), man being only an incidental 'dead end' host. Out-breaks have been seen in most parts of India except the north west. The disease presents with a prodromal stage, an acute encephalitic stage with coma, convulsions and variable deficits and a convalescent stage. Diagnosis can be made by viral isolation from CSF or brain, or serologic tests such as haemagglutination inhibition test and IgM antibody capture ELISA in CSF and blood. There is no specific treatment. Mortality ranges from 20-50% and almost half the survivors have sequelae. The most effective control measure besides control of mosquitos is vaccination. A killed mouse brain vaccine is being prepared in India and is safe and effective but expensive. Rabies is a highly fatal encephalomyelitis primarily occurring in urban dogs and wild animals especially canines. It is endemic in India and affects an estimated 3 per 100,000 persons annually. The patient initially may display bizarre combative behaviour. The disease can be effectively prevented by post exposure vaccination. The nervous tissue vaccine is no longer recommended because of unacceptable neurotoxicity. Three cell culture vaccines are presently available with about equal efficacy.

Animals↗
PubMed1995

Hemocyte alterations during melanotic encapsulation of Brugia malayi in the mosquito Armigeres subalbatus.

The involvement of hemocytes in melanotic encapsulation reactions against Brugia malayi was assessed in Armigeres subalbatus. Hemocyte populations, epitope changes, phenol oxidase (PO) activity, and the presence of an 84-kDa polypeptide were investigated in mosquitoes exposed to a B. malayi-infective bloodmeal (= immune-activated), in mosquitoes given a noninfective bloodmeal (= controls), in nonbloodfed mosquitoes (= naive), or in some combination of these. Total hemocyte populations in immune-activated mosquitoes significantly decreased at 24 hr postbloodmeal (PB) as compared with controls. At 48 and 72 hr PB, hemocyte population levels in immune-activated mosquitoes increased to control levels. Epitope changes, as indicated by wheat germ agglutinin (WGA) binding, also were observed. There was a significant increase in the percentage of hemocytes binding WGA in immune-activated mosquitoes at 24 hr PB as compared with controls. Furthermore, the activity of hemocyte PO, an enzyme involved in the melanotic encapsulation pathway, was significantly elevated at 12 hr PB in immune-activated mosquitoes as compared with controls. Analysis for the presence of an 84-kDa polypeptide in A. subalbatus indicates that a 2.0-kb message in total RNA hybridized to D6.12, an Aedes aegypti cDNA encoding an 84-kDa polypeptide that is associated with melanotic encapsulation responses. The hybridization of D6.12 to RNA was not greater in immune-activated as compared to control A. subalbatus, as has been observed in A. aegypti. Results indicate that these hemocyte changes correspond in time with the melanotic encapsulation reactions of A. subalbatus against filarial worms.

Animals↗
PubMed2005

Toxicity and effects of microbial mosquito larvicides and larvicidal oil on the development and fecundity of the tadpole shrimp Triops newberryi (Packard) (Notostraca: Triopsidae).

Tadpole shrimp (TPS), Triops newberryi (Packard) (Notostraca: Triopsidae), is a predatory agent for immature mosquitoes breeding in aquatic habitats. This biological control agent could be used with other larvicides in mosquito control programs. In order to elucidate compatibility of the TPS and commonly used mosquito larvicides, studies were initiated to investigate effects of Bacillus thuringiensis ssp. israelensis (B.t.i.) de Barjac, Bacillus sphaericus Neide and Golden Bear-1111 larvicidal oil on growth, longevity, and fecundity of TPS in laboratory and field. The exposure of TPS to high dosages of B.t.i. and B. sphaericus in the laboratory or in the field did not have significant adverse effects on growth, longevity, and fecundity. These results indicate that TPS are compatible with microbial larvicides and can be used jointly in practical mosquito control programs. The larvicidal oil GB-1111, on the other hand, caused almost 100% mortality within 48 h after treatment in the laboratory even at the low dosage of 0.38 gallons/ac. The impact of oil in the field was less severe, as significant adverse impact on population density was noted at 1 gallon/ac when water temperatures were warmer, or 2 gallons/ac when water temperatures were cooler. Almost 100% mortality within 48 h was noted at 2 gallons/ac when water temperatures were warmer or at 4 gallons/ac when the water temperatures were cooler. These results indicate incompatibility between this larvicidal oil and TPS at the higher rates of the label range, and joint use of TPS and larvicidal oil at dosages of 1-2 gallons/ac or greater, depending on water temperatures, should be avoided.

Animals↗
PubMed1993

[Current situation of yellow fever in Latin America].

Yellow fever endemicity is currently stabilized in South America: an average of 115 cases has officially been notified each year since 25 years (between 12 and 304 annual cases). These figures are underevaluated but no epidemic has been observed since 1983. Only sporadic or limited grouped cases have been reported. All declared cases correspond to people who have been infected within sylvatic areas, mainly adult forestmen. Within the last years, the majority of cases have occurred in Peru and Bolivia; the other cases have been observed in Brazil, in Columbia, in Ecuador and in French Guiana (imported strains from Surinam). This apparently low virus circulation may be due to massive campaigns of vaccination and to mosquito vector control. But this situation could suddenly reverse as observed in the past with yellow fever and the spring of the urban Aedes aegypti vector. Genetic and immunochemical heterogeneity has been demonstrated between South American and African yellow fever strains, which may reveal evolutionary divergence due to different ecological environment between the two continents. Yellow fever definitely remains a topical disease which requires a constant surveillance.

Aedes↗
PubMed2005

Genetic variation along time in a Brazilian population of Aedes aegypti (Diptera: Culicidae), detected by changes in the esterase patterns.

Aedes aegypti from the Brazilian cities of São José do Rio Preto (SJ) and Goiânia (GO) were analyzed as to their esterase patterns and the results were compared with data obtained about 5 years before for SJ population. Esterase bands not detected in the previous study were now observed in mosquitoes from both SJ and GO populations, being the last considered a population resistant to insecticides. Other similarities between SJ and GO populations in this study, and some differences in comparison with the previous data on SJ were observed, involving, in addition to changes in band type, changes in frequency of mosquitoes expressing them and differential gene activation during development. As it is generally true for genetic features, changes in the esterase patterns are expected to be the result of factors such as selection by environmental conditions and genetic drift. In the present case, continuous use of insecticides aiming mosquito population size control in SJ by sanitary authorities could be involved in the observed changes. Changed esterases were classified as carboxylesterases and cholinesterases, which are enzymes already shown to take part in the development of resistance in several organisms. In addition, data obtained in the elapsed time by authorities responsible for the mosquito control has shown increasing insecticide resistance of SJ population mosquitoes parallel to increase in the total amount of esterases, reinforcing the mentioned possibility.

Aedes↗
PubMed2004

[Malaria: from genetic and molecular biology to disease control].

The knowledge of the genomic structure of Plasmodium falciparum and of its main vector, Anopheles gambiae, may offer new perspectives for malaria therapy, vaccines or control of mosquito-borne transmission. New targets for future antimalarial drugs were identified, mainly apicoplast (a vestige of a vegetal structure incorporated by the parasite) and several enzymes, particularly proteases. The practical difficulty is now to select a few number of these "promising molecules", probably no more than 3 or 4, for a preclinical and clinical pharmaceutical development. Indeed, several other antimalarial drugs are already under development, and the industrial possibilities for developing new drugs are evidently limited. Many new vaccination targets and antigenic proteins were also identified. According to scientific and industrial limitations, a complete evaluation of these antigens is absolutely necessary to select a few of them for clinical development. For anti-malarial vaccinations, DNA vaccines may offer the most interesting perspectives, with the possibility of simultaneous immunisation against different Plasmodium stages and of an adjuvant effect by adding a gene encoding certain cytokines. In Anopheles gambiae genome, several genes encoding key-proteins (particularly odorant receptors necessary for blood feeding) were identified, as other genes encoding for proteins limiting the sexual development of Plasmodium inside its vector. From a theoretical viewpoint, genetically modified non biting or non transmitting mosquitoes offer new perspectives for the control of malaria transmission, but until now, the preliminary practical attempts gave rather poor results. On the whole, the genomic and proteomic of Plasmodium falciparum and Anopheles gambiae yielded exciting scientific results, but it is still too early and very speculative to imagine their practical applications for the control of malaria.

Animals↗
PubMed2004

Remote sensing as a tool for mapping mosquito breeding habitats and associated health risk to assist control efforts and development plans: a case study in Wadi El Natroun, Egypt.

Limited mosquito ground surveys were combined with remote sensing and GIS technologies to identify mosquito breeding habitats in Natroun lakes area and to delineate associated health risks. Mosquito larval surveys were carried out in a small area to characterize positive breeding habitats and determine their geographic coordinates. Mosquitoes (Anopheles multicolor, Culex antennatus and Cx. theileri) were found breeding in water-flooded habitats with dense vegetation cover spatially associated to existing lakes. Chemical analysis indicated that mosquito breeding water was found to be polluted by several sources including agriculture, industrial and domestic sources. This information served as a training set to characterize the spectral signature of mosquitogenic (mosquito-producing) habitats using reflectance data of the Thematic Mapper (TM) sensor aboard Landsat 5 satellite. Following characterization of the spectral signature, satellite data were used to predict, potential mosquito breeding patches over the whole study area. Field surveys were then carried out to assess the accuracy of predicted habitats and those surveys have indicated that all checked sites were positive for mosquito larvae demonstrating an accuracy of 100%. Based on an average adult mosquito flight range of 2 km, GIS was used to create buffer zones around breeding habitats describing areas at risk from mosquito nuisance and disease transmission. The obtained results could thus provide a new basis for directing the control of mosquito vectors as they provide health authorities with precise maps of mosquito breeding habitats in a timely manner. Moreover, the generated map delineating risk areas could be used by project developers to either re-site the project or invest in mosquito control activities in order to avoid health risks and ensure sustainability of their development. The approach adopted in this investigation demonstrated the practical and successful application of remote sensing and GIS in assisting health and development decision making.

Animals↗
PubMed1988

A trial of bed nets (mosquito nets) as a malaria control strategy in a rural area of The Gambia, West Africa.

An intervention trial was undertaken in a rural area of The Gambia to assess the impact on malaria morbidity of the use of bed nets. Bed nets were allocated at random among a group of 16 Fula hamlets, where they were previously rarely used. The incidence of febrile episodes with associated malaria parasitaemias throughout the rainy season and the prevalence of splenomegaly and parasitaemia at the end of the rainy season were determined in 233 children aged 1-9 years who slept under bed nets and in 163 children who did not. Bed nets were used correctly by the children in the study cohort, but direct observations showed that a significant number of children left their nets for a period during the night. There was no significant difference in the incidence of clinical attacks of malaria or in any other malariometric measurement between the 2 groups. Thus, bed nets were not effective in reducing malaria morbidity in this group of children. The apparent protection from bed nets demonstrated in previous retrospective surveys may have been due to an increased number of infective bites being received by exposed individuals sleeping close to users of bed nets.

Child↗
PubMed2004

Predatory potential of Nepa cinerea against mosquito larvae in laboratory conditions.

Biocontrol potential of nepidae bug, Nepa cinerea against immature stages of Anopheles stephensi, Anopheles culicifacies, Culex quinquefasciatus and Aedes aegypti was studied under laboratory conditions. It was found that N. cinerea had the highest predation against An. stephensi followed by An. culicifacies, Cmx quinquefasciatus and Ae. aegypti. From the analysis, it was found that N. cinerea has good predation efficacy. It can be used as a biological control agent to control of mosquito breeding in integrated disease vector control programme.

Aedes↗
PubMedDate not supplied

Approaches to vector control: new and trusted. 5. The epidemiological context of vector control.

This paper discusses 2 prominent, contemporary issues in the epidemiological context of insect vector control: (i) the magnitude of the control problem, and (ii) non-linear processes influencing vector control. It concludes that we still cannot reliably measure the scale of some important control problems; e.g., there is considerable uncertainty about the basic reproduction number of malaria. The emergence of new concepts such as strain-specific immunity, and a growing emphasis on disease control as distinct from infection control, mean that some quantitative problems are being redefined more quickly than they are being solved. Population biologists have urged exploration of density-dependent processes which may help or hinder new methods of vector control. This brief review of non-linear phenomena such as facilitation and limitation finds little evidence that they will significantly influence, e.g., the introduction of some novel refractory mechanism into a vector population.

Animals↗
PubMed2004

Nutritional regulation of JH synthesis: a mechanism to control reproductive maturation in mosquitoes?

Juvenile hormone (JH) titers must be modulated to permit the normal progress of development and reproduction in mosquitoes. In adult female Aedes aegypti, JH levels are low at adult eclosion, elevated in sugar-fed females and low again after a blood meal. Although degradation plays a role, JH titer is fundamentally determined by the rate of biosynthesis in the corpora allata gland (CA). CA from newly eclosed females (0-1 h after emergence) exhibit a very low basal JH biosynthetic activity, Aedes-allatotropin stimulates the CA in newly emerged females to produce JH. There is a correlation between nutritional reserves at adult emergence (teneral reserves) and CA activity. JH synthesis is significantly reduced in teneral females that emerge with low nutritional reserves. Taking a blood meal results in a reduction of CA activity. The biosynthetic activity of Ae. aegypti CA is significantly inhibited by factors present in the head, as well as by Anopheles gambiae PISCF-allatostatin. Nutritional signals affect the release of allatotropin and allatostatins by the brain resulting in the activation or inhibition of JH synthesis. JH is therefore an important part of a transduction mechanism that connects changes in the nutritional status with activation of specific physiological events during reproduction.

Aedes↗
PubMedDate not supplied

West Nile encephalitis.

After the New York outbreak of West Nile Virus encephalitis in the summer of 1999, awareness that vulnerable children and adolescents may be at risk for this mosquito-borne viral infection intensified. The Nurse Practitioner can play an invaluable critical role to recognize and diagnose this arthropod-borne virus. Pathophysiology, vector transmission, clinical manifestations and laboratory findings are discussed in this article. Emphasis is placed on the PNP's role of providing anticipatory guidance concerning prevention of outbreaks and physical management that focuses on the elimination of mosquito-breeding areas, reducing personal exposure, and biological control of mosquito populations.

Adolescent↗