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Cemetery vase breeding of dengue vectors in Manila, Republic of the Philippines.

Aedes albopictus and Ae. aegypti were found breeding abundantly in cement vases within cemeteries in Manila. Aedes albopictus dominated in cemeteries containing vegetation which provided both shade and plant debris for the vase water. The highest larval densities for both species were found from August to December, which is from mid-to-late rainy season. Aedes albopictus is unable to compete successfully with Ae. aegypti in residential areas with sparce vegetation and thus is very limited in its distribution within the city. Biting activity of both species is similar, with peaks occurring between 0530-0600 h and 1730-1800 h.

Aedes↗

Repellents and other personal protection strategies against Aedes albopictus.

Five chemical repellents, a controlled-release repellent formulation, Avon Skin-So-Soft bath oil and permethrin-impregnated clothing fabric were assayed for personal protection against bites of Aedes albopictus. On skin the chemical repellents provided significant (P = 0.05) protection from biting; however, Ae. albopictus was more sensitive to the repellents than the standard, Ae. aegypti. Two experimental repellents provided 6-7 h protection from bites, 25% deet in ethanol provided greater than 8 h protection, a controlled-release formulation containing 35% deet provided greater than 10 h protection, and the Avon product provided 0.64 h protection from bites. Permethrin-treated fabric provided complete protection from mosquito bites through 0-5 washings. Repellent products containing greater than or equal to 12% deet should provide satisfactory protection against Ae. albopictus; the use of permethrin-impregnated clothing should provide additional protection.

Aedes↗

Urticaria in Thai children.

In this study, 142 patients under 12 years of age with the diagnosis of urticaria accompanied or not by angioedema were examined. In all 72.6% of the patients were under 6 years of age. Boys and girls were equally affected, 13.4% of the cases had chronic urticaria, 56.3% had a previous history of urticaria, 88.0% had generalized urticaria, and about half of the cases had associated angioedema. The causes of the urticaria were identified or suspected in 32.4% of the cases. Drugs, foods, insect bites and stings, infections and cold were the most common or associated precipitating agents in that order. Histories revealed 27.5% of the cases had records of other allergic diseases, and 76.1% had allergic diseases in the family. Dermographisms were found in 16.2% of the cases, and 22.5% of cases had eosinophilia. The means of IgE levels in both acute and chronic urticaria were within normal limits, and there was no statistically significant difference between the two groups. Skin testing was of little practical value in evaluating the etiology of the urticaria. Clinical trials of drugs for symptomatic treatment revealed that clemastine, ketotifen and hydroxyzine gave approximately equally high response rates. All these three medications gave significantly greater response rates than chlorpheniramine.

Angioedema↗

Field bioassays of permethrin-treated uniforms and a new extended duration repellent against mosquitoes in Pakistan.

Field bioassays were conducted to evaluate the effectiveness of different treatment combinations of permethrin-impregnated clothing and a new extended duration repellent formulation of deet against natural populations of mosquitoes in Islamabad, Pakistan. Tests were initiated 2-2 1/2 hours prior to sunset and volunteers who wore the topical repellent applied it 8 hours earlier. The most effective treatment was a combination of wearing both the permethrin-impregnated clothing and the repellent on exposed skin. This combination provided 100% protection from bites whereas volunteers wearing only treated clothing received 57% protection. Those wearing only repellent received 89% protection, but, under the biting pressure observed, this was not significantly different from the treated clothing-repellent combination.

Animals↗

Mathematical models of the effectiveness and persistence of mosquito repellents.

Two models of the effectiveness and persistence of mosquito repellents on the skin were developed from published functions and data. The probit plane model, Y = a + b1X1 + b2X2, relates the response (Y, in probits) of the mosquito test population to the log dose (X1) of repellent applied and the test period, or elapsed time from the time of application (X2). The exponential decay model, Z = X1 + (b2/b1)X2, estimates the repellent residue (log-1 Z) from X1 and X2. The models were validated with original data from tests of deet (N,N-diethyl-3-methylbenzamide) and ethyl hexanediol (2-ethyl-1,3-hexanediol) on the forearm against the yellow fever mosquito, Aedes aegypti. The probit plane model was evaluated as Y = 8.83 + 1.56 X1-0.69X2 for deet and Y = 8.67 + 1.68X1 - 0.92X2 for ethyl hexanediol when X1 is in log mg/cm2 and X2 is in hours. The exponential decay model was evaluated as Z = X1 - 0.45X2 for deet and Z = X1 - 0.55X2 for ethyl hexanediol. The decay constant (lambda) and half-life (t1/2) were estimated as 1.03 hr-1 and 0.67 hr for deet and 1.26 hr-1 and 0.55 hr for ethyl hexanediol from the slope parameter (b2/b1) of the decay model. Applicable correlation coefficients, standard errors and confidence limits are given. The introduction of these models of the pharmacodynamics of mosquito repellents is a step toward establishing a rational basis for the research, development, testing and evaluation of repellents and for their regulation by the government.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Cutaneous↗

Effectiveness of soap formulations containing deet and permethrin as personal protection against outdoor mosquitoes in Malaysia.

Two soap formulations, both containing 20% deet and one each containing permethrin at 0.5 and 1.0%, respectively, were applied to exposed arms and legs of volunteers as personal protection against outdoor human biting mosquitoes in six locations on Penang Island, Malaysia. The predominant mosquito species collected from these locations were Aedes albopictus, Mansonia uniformis, Culex gelidus, Anopheles lesteri and Armigeres subalbatus. Efficacy and residual effects up to 4 hours indicated good protection against these species. Reduction in mosquito landing-biting rates in treated groups ranged from 83.8 to 100.0%. At high densities, small percentages of Ma. uniformis and An. lesteri landed or bit on treated skin. Use of the soap formulations in terms of cost-effectiveness, safety and overall vector control strategy for some tropical diseases is discussed.

Animals↗

Some corrections to the record on insect repellents and attractants.

Fifteen apparent errors of observation, reporting, interpretation, or attribution occurring in the insect repellent and attractant literature were examined. Topics discussed are the boiling point effect, solvents and solutions, repellent-treated netting, terpineol and diphenyl oxide, lactic acid, the smell and feel of deet (diethylmethylbenzamide), effective half-life, protection time, protection time of deet for men and women, McGuire's formula, "plussing out", King's classification, exorbitant doses, extrapolated doses, and extreme observations. The decay constant (1.36 hr-1) and half-life (0.51 hr) of a mosquito-repellent bath oil (Skin-So-Soft) are reported for the first time.

Animals↗

[The effect of selected preparations for the protection of draft horses against dipterous blood-sucking insects].

Dipterous blood-sucking insects (horseflies, black flies, gnats, midges) have negative impacts on the performance of draught horses in forest enterprises. For the protection of these animals, the following preparations were applied at the interval of 24 hours: diethyltoluamide, Oxamat (N,N-diethyloxamine acid, USSR) and Stomoxin (synthetic pyrethroid, product of the firm Wellcome, England). In the course of 66 working days, the performance of test animals treated with 10% water emulsion of diethyltoluamide increased by 49.25 cu. m. of skidded wood, i.e. by 0.74 cu. m. wood per horse/day (21.65%), as compared with the control group. The daily savings of prime costs per test horse/day made 16.99 Kcs (Czechoslovak crowns). In comparison with the control group, the performance of horses treated with 5% water emulsion of Oxamat increased by 85.50 cu. m. wood, i.e. by 1.29 cu. m. wood per horse/day (38.00%). Stomoxin at the concentration of 0.05% acted as a good insecticide but had no marked repellent effect. The results of this study document that the production of effective repellents should be introduced in the Czechoslovak Socialist Republic.

Animals↗

Some entomological observations on malaria transmission in a remote village in northwestern Thailand.

Anopheline mosquitoes and their relation to malaria transmission were studied during the months of March, May and July in the Karen village of Mae Tha Waw located in the northwestern mountains of Tak Province. Thirteen species were captured on human bait during 80 man-nights of collecting. Four additional species were collected during routine larval surveys. Anopheles minimus and An. maculatus comprised 92.5% of the specimens captured biting man. Anopheles minimus and An. nivipes were implicated as vectors based on the detection of sporozoite infections using enzyme-linked immunosorbent assays for Plasmodium falciparum and P. vivax. Anopheles dirus was rarely encountered and probably played little part in transmission in Mae Tha Waw during the period of study. Information is provided on nightly biting activity, incidence of disease, infectivity and larval bionomics.

Animals↗

Geographic distribution and biting behaviour of four species of the Anopheles dirus complex (Diptera: Culicidae) in Thailand.

A cytogenetic analysis of the species status of members of the Anopheles dirus group, from natural populations, over a six-year period has produced biogeographic and behavioural data which are presented herein. Species A, B, C and D have quite distinct geographic distributions in Thailand. Species A is the only species in most of the mainland but is absent from the southern half of the peninsula. Species B is dominant in the far south of the peninsula giving way to species C on the north-east side and rarely occurring on the west side of the peninsula; it is unknown from the northern half or the rest of the country. Species C is known from the middle eastern side of the peninsula and from a site far to the north along the Burmese border. Species D occurs down the mountains along the Burmese/Thai border and along the north half of the western peninsula. Each species appears to have distinct times of biting during the night. They also appear to have differential seasonal abundance. These data together with the differing geographic distributions suggest some implications for Plasmodium transmission and that care should be taken to identify these genetic species during malariometric studies.

Animals↗

Experimental transmission of Plasmodium mexicanum by bites of infected Lutzomyia vexator (Diptera: Psychodidae).

Lutzomyia vexator is an efficient experimental vector of Plasmodium mexicanum, infecting 69.2% (9/13) of the Sceloporus undulatus lizards with as few as one bite. Sporozoites were present in the salivary glands by day 6.5 postfeed and infective by day 8 postfeed at 27 degrees C. The prepatent period was relatively long, ranging from 23 to 40 days for bite-induced infections and appears to be related to the number of sporozoites injected. The acute phase of the infection is initially exponential and rapid. All lizards (6) that were not sacrificed, died of fulminating infections from 13 to 56 days after parasites were seen in the blood films. Gametocytes from 2 experimentally infected lizards were infective to L. vexator during the course of the acute infection. The majority of P. mexicanum parasites were in erythrocytes of Sc. undulatus. Exoerythrocytic forms were observed in circulating lymphocytes and thrombocytes, lymphocytes of spleen and bone marrow, and endothelial cells of brain capillaries.

Animals↗

Vector incrimination and experimental transmission of Plasmodium floridense by bites of infected Culex (Melanoconion) erraticus.

A survey of mosquitoes which are attracted to and readily feed upon lizards in a northcentral Florida area where there is a relatively high prevalence of Plasmodium floridense in Anolis carolinensis was conducted. Culex erraticus and Cx. territans, collected in lizard-baited traps, readily fed on lizards in the traps and in the laboratory, and the former mosquito species is an experimental vector of Plasmodium floridense. Sporozoites were observed in the salivary glands from 11 to 14 days at 21-25 degrees C following an infective blood meal. The prepatent period of P. floridense in A. carolinensis at 18-24 degrees C was relatively long, 24-25 days (n = 2). At 32 degrees C, the prepatent period was decreased to 13-17 days (n = 4). The transmission rate of P. floridense by bite of Cx. erraticus and intraperitoneal inoculation of sporozoites from the salivary glands of Cx. erraticus, was relatively low (16.2%). Peak parasitemias ranged from 912 to 4,280 parasites per 10,000 red blood cells. Sporogonic development of P. floridense in Cx. territans which fed on infected lizards was not observed.

Animals↗