The effects of smoke from mosquito coils on Anopheles gambiae Giles and Mansonia uniformis (Theo.) in verandah-trap huts at Magugu, Tanzania

Abstract

IntroductionSmoke from mosquito coils is widely used as a method of reducing the nuisance from mosquitoes, particularly in South-East Asia, Japan, parts of Africa and South America (Maclver, 1963). Laboratory tests showed coils containing pyrethrins to have several effects on mosquitoes. Maclver (1964a) using blood-fed Aedes aegypti (L.) caged about 8 cm from a coil in a closed room found that there was a decrease in the KD90 (time to knockdown of 90%) from 105 min with coils containing 0-1% pyrethrins to 20 min with coils containing 0-5% pyrethrins. Coils containing more than 0-5% pyrethrins did not have decreased KD90 values. Mortality after three hours' exposure plus 24-h holding period ranged from 88% with 0 1 % pyrethrins coils to 100% with 0-5% pyrethrins coils. "Blank coils" that were virtually free from pyrethrins caused no knockdown in three hours and no mortality in a further 24 h. Maclver (1964a), Paulini & Ricciardi (1954), Kogan (1961), Fales et al. (1968 and Mace (1969) all showed that in various types of cage or tube mosquitoes would congregate in the part furthest from sources of smoke from pyrethrins coils. This has usually been termed " repellency ". Winney (1969) showed that fewer Ae. aegypti would feed on a human arm in air containing smoke from pyrethrins coils than in clean air. Smith & Obudho (1967) tried mosquito coils containing 0-23-0-24% pyrethrins in a verandahtrap hut at Magugu. They noted an increase in the overall mortality of naturally entering Anopheles gambiae Giles from 8% before treatment to 19-27% during the period when coils were burned. The proportion of mosquitoes in the exit traps increased from 39% to 86-92% and the proportion of unfeds increased from 30% to 75-81%.This paper describes trials of mosquito coils made in six verandah-trap huts at Magugu between December 1967 and June 1968. The work had three objectives: first, to compare the different brands of coil which were available in Tanzania at the time, including some containing pyrethrins and others containing DDT; second, by comparing the numbers of mosquitoes entering treated and control huts to determine whether the coils deterred mosquitoes from entering; third, to see whether the relation between pyrethrins concentration and effectiveness found by Maclver (1964a) using caged mosquitoes would also apply to free flying mosquitoes in a ventilated room.

Field efficacy of thermally expelled or live potted repellent plants against African malaria vectors in western Kenya

“…by thermal expulsion was comparable with that of a mosquito coil that was used as a positive control in this field trial. The level of repellency of mosquito coil in this study is in agreement to reports of 24–88% reduction from Tanzania and Papua New Guinea (Hudson & Esozed 1971; Charlwood & Jolly 1984). The continuing repellency of plants after application by thermal expulsion showed that thermal fumigation in the early hours of the night may be sufficient to effectively repel mosquitoes for the remaining duration of the night.…”

Preliminary field trials of personal protection against mosquitoes in The Gambia using deet or permethrin in soap, compared with other methods

“…The burning of pyrethroid coils protected individuals outdoors. Similar reductions have been reported by other workers in Africa (Hudson & Esozed, 1971;Smith et al, 1972) and in Papua New Guinea (Charlwood & Jolley, 1984).…”

Experimental hut trials of permethrin‐impregnated mosquito nets and eave curtains against malaria vectors in Tanzania

“…Although the impregnated eave curtains were consistently less efficient than the nets with which they were compared, they still provided about as much protection (57-7396) in the verandah-trap huts (Table 6) as the pyrethrum mosquito coils tested in the same huts by Smith et al (1972) and Hudson & Esozed (1971). Like the nets.…”