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Evaluation of compounds for insecticidal activity on adult mosquitos. 5. Toxicity to adult mosquitos and residual properties of some pyrethroids.

New pyrethrin-like compounds are compared with earlier synthetic pyrethroids and natural pyrethrins for intrinsic toxicity to adult mosquitos and for residual contact activity. Two of the compounds are at least as toxic as pyrethrin I to female Anopheles stephensi and Aedes aegypti. Residues of these compounds are very persistent in the dark or in very subdued lighting but they decompose on exposure to normal intensities of daylight and rapidly lose their insecticidal activity.

Animals↗

Experimental infection of Aedes aegypti mosquitoes, suckling mice, and rats with four mosquito spiroplasmas.

Four mosquito spiroplasmas, Spiroplasma culicicola, Spiroplasma sabaudiense, Spiroplasma taiwanense, and an isolate designated CUAS-1 were nonpathogenic for suckling mice and suckling rats inoculated either intracerebrally or intraperitoneally. S. culicicola persisted as long as 14 days in the brain of intracerebrally inoculated mice but did not replicate. The three other spiroplasmas were not reisolated from inoculated rats or mice. S. culicicola replicated in vitro at 37 degrees C in M1D media. A low but clear-cut immune response was elicited in suckling rats inoculated with S. sabaudiense. S. culicicola and S. taiwanense were pathogenic (life span reduced) for Aedes aegypti females inoculated intrathoracically. The progeny of Ae. aegypti females inoculated with S. sabaudiense had a significantly reduced emergence rate in one of two trials and a significant distortion of the sex ratio in two of two trials (increased percentage of males). Female Ae. aegypti inoculated with S. culicicola had a significantly reduced fecundity rate.

Animals↗

Tolypocladium cylindrosporum (Deuteromycotina: Moniliales), a fungal pathogen of the mosquito Aedes australis. III. Field trials against two mosquito species.

A blastoconidial preparation of the New Zealand isolate of T. cylindrosporum was tested in two field trials against larvae of the freshwater mosquito Aedes subalbirostris and the brackish water species Ae. australis. There was some reduction in the population of the Ae. subalbirostris larvae and larvae collected from the test pools exhibited signs of fungal infection when reared in the laboratory. In the brackish pools there was no observable decrease in the larval populations even though Ae. australis is the natural host of T. cylindrosporum [NZ]. Water volume fluctuations in the test pools were a major difficulty experienced when monitoring the results. Tests against field-collected non-target fauna indicated that T. cylindrosporum is non-specific in action. Species of daphnid, dixid larvae and copepods were all susceptible to infection at varying degrees.

Aedes↗

Toxic effects of mosquito coil (a mosquito repellent) smoke on rats. II. Morphological changes of the respiratory system.

A group of 20 female albino rats was exposed to mosquito coil smoke, 8 h a day, 6 days per week, for 60 days. An additional group receiving air exposure served as control. The smoke-exposed animals had a lower body weight than the controls. Smoke-induced histopathological lesions, including an inflammation of the tracheal epithelium, atelectasis of the lung parenchyma, emphysema, increase of alveolar macrophages in the alveolar space and perivascular infiltration of polymorphonuclear cells were observed in the experimental rats. An elevation of enzyme activities of lactate dehydrogenase, glutamate pyruvate transaminase, glutamate oxoacetate transaminase and acid phosphatase were found in the serum of the smoke-exposed rats indicating the enzymes were released from the damaged tissues into the blood stream.

Animals↗

Alkalization of larval mosquito midgut and the role of carbonic anhydrase in different species of mosquitoes.

We have previously demonstrated the involvement of carbonic anhydrase (CA) in the alkalization mechanism of the Aedes aegypti larval midgut. In this study, we used Hansson's histochemistry to examine the distribution of the enzyme in the midgut of six different species of mosquito larvae (Aedes aegypti, Aedes albopictus, Culex quinquefasciatus, Culex nigripalpus, Ochlerotatus taeniorhynchus, Anopheles quadrimaculatus). Additionally, we quantitated CA content in the gastric caeca, anterior and posterior midgut of fourth instar larvae from these species using the 18O isotope exchange method coupled to mass spectrometry. We also tested the effect of CA inhibitors such as methazolamide and acetazolamide in the alkalization of the midgut for these species. Our results indicate that CA is present in the larval midgut of the species studied and that it appears to be associated with the posterior midgut and gastric caeca in some species and with the anterior midgut in others. CA inhibitors appear to have a profound effect on the alkalization mechanism of the midgut with lethal consequences for most of the species tested.

Acetazolamide↗

The defensin peptide of the malaria vector mosquito Anopheles gambiae: antimicrobial activities and expression in adult mosquitoes.

A recombinant Anopheles gambiae defensin peptide was used to define the antimicrobial activity spectrum against bacteria, filamentous fungi and yeast. Results showed that most of the Gram-positive bacterial species tested were sensitive to the recombinant peptide in a range of concentrations from 0.1 to 0.75 microM. No activity was detected against Gram-negative bacteria, with the exception of some E. coli strains. Growth inhibitory activity was detected against some species of filamentous fungi. Defensin was not active against yeast. The kinetics of bactericidal and fungicidal effects were determined for Micrococcus luteus and Neurospora crassa, respectively. Differential mass spectrometry analysis was used to demonstrate induction of defensin in the hemolymph of bacteria-infected adult female mosquitoes. Native peptide levels were quantitated in both hemolymph and midgut tissues. The polytene chromosome position of the defensin locus was mapped by in situ hybridization.

Animals↗

Comparative genome analysis of the yellow fever mosquito Aedes aegypti with Drosophila melanogaster and the malaria vector mosquito Anopheles gambiae.

An in silico comparative genomics approach was used to identify putative orthologs to genetically mapped genes from the mosquito, Aedes aegypti, in the Drosophila melanogaster and Anopheles gambiae genome databases. Comparative chromosome positions of 73 D. melanogaster orthologs indicated significant deviations from a random distribution across each of the five A. aegypti chromosomal regions, suggesting that some ancestral chromosome elements have been conserved. However, the two genomes also reflect extensive reshuffling within and between chromosomal regions. Comparative chromosome positions of A. gambiae orthologs indicate unequivocally that A. aegypti chromosome regions share extensive homology to the five A. gambiae chromosome arms. Whole-arm or near-whole-arm homology was contradicted with only two genes among the 75 A. aegypti genes for which orthologs to A. gambiae were identified. The two genomes contain large conserved chromosome segments that generally correspond to break/fusion events and a reciprocal translocation with extensive paracentric inversions evident within. Only very tightly linked genes are likely to retain conserved linear orders within chromosome segments. The D. melanogaster and A. gambiae genome databases therefore offer limited potential for comparative positional gene determinations among even closely related dipterans, indicating the necessity for additional genome sequencing projects with other dipteran species.

Aedes↗

Parasites of the Asian tiger mosquito and other container-inhabiting mosquitoes (Diptera:Culicidae) in northcentral Florida.

Seven microorganisms including 4 protozoans, 2 fungi, and a bacterium infected Aedes albopictus (Skuse) larvae collected from 12 counties in northecentral Florida. Ae albopictus and 14 other species of mosquitoes were collected from tires, flower-holding vases in cemeteries, other types of artificial containers, and treeholes. Ascogregarina taiwanensis (Lien & Levine) was the most common parasite of Ae. albopictus throughout the year. The microsporidium Vavraia culicis (Weiser) infected Aedes aegypti (L.), Ae. albopictus, Aedes triseriatus (Say), and Orthopodomyia sinifera (Coquillett). A vibrio bacterium and 2 fungi (Leptolegnia sp. and Smittium culisetae Lichtwardt), infected Ae. albopictus larvae but were observed infrequently. A. taiwanensis, S. culisetae, and the vibrio bacterium previously have been reported from Ae. albopictus. This is the 1st report of the other 4 microorganisms parasitizing Ae. albopictus larvae.

Aedes↗

Mosquito engineering. Building a disease-fighting mosquito.

With resistance against insecticides on the rise and a U.N.-backed push to phase out DDT, several labs have embarked on the most ambitious and futuristic of all approaches to combat malaria: They hope to replace billions and billions of mosquitoes in the world's endemic areas with new strains, created in the lab, that would be "refractory," or unable to transmit Plasmodium, the parasite that causes the disease. The idea is not that farfetched, these researchers claim.

Aedes↗

Rainfall and vector mosquito numbers as risk indicators for mosquito-borne disease in central Australia.

There have been 5 confirmed cases of Murray Valley encephalitis virus (MVE) infection in the Alice Springs region during the high rainfall years of 1999/00 and 2000/01, compared with one case in the preceding 9 years. There also appeared to be an increased prevalence of Ross River virus (RR) infection in the Alice Springs and Tennant Creek regions associated with high rainfall. This paper presents an analysis of summer rainfall from 1990/91 to 2000/01, numbers of seroconversion of sentinel chickens to MVE, and RR cases in both regions. In Alice Springs where summer rainfall (December to February) and average vector numbers in the December to March period are closely correlated, the analysis also included mosquito vector numbers and MVE cases. Summer rainfall over 100 mm was significantly associated with sentinel chicken seroconversions to MVE. From December to March there was also a significant association of average vector numbers (> or = 300) with seroconversions in sentinel chickens following high summer rainfall. MVE appears enzootic in the Tennant Creek region and epizootic in the Alice Springs region. In Alice Springs during December to March, there was a significant association of RR cases with rainfall over 100 mm and with average vector numbers over 300. There was also a significant correlation of summer rainfall with RR cases in Tennant Creek. Summer rainfall is a new and good early indicator of high risk for both MVE and RR disease in the Alice Springs locality and RR in the Tennant Creek locality. Although similar relationships between rainfall and vector abundance, and disease incidence probably exist in other areas of central Australia, rainfall and vector abundance thresholds will probably vary according to local climatic and environmental conditions.

Alphavirus Infections↗

[Pathogenicity of Aedes aegypti L. mosquito densonucleosis virus to larvae of other species of blood-sucking mosquitoes].

Laboratory studies established that A. aegypti mosquito virus of densonucleosis was infectious for larvae of A. caspius dorsalis, A. vexans, A. cinereus and C. pipiens pipiens caught in natural water bodies. Death rates of Aedes and Culex larvae experimentally were 46.3% on the average, while in control groups 19.7%. The external appearance of virus-infected larvae and pathological changes in nuclei of the cells of the fat body were identical to those previously described in A. aegypti larvae affected with densonucleosis.

Adipose Tissue↗