Mass treatment with ivermectin for filariasis control in Papua New Guinea: impact on mosquito survival

Abstract

Field studies were carried out to determine the impact of mass human treatment with ivermectin on the survival of anthropophagic mosquitoes of the Anopheles punctulatus complex (Diptera: Culicidae), the vectors of lymphatic filariasis and malaria in Papua New Guinea. In a village where mass treatment had been given, using 400 microg/kg ivermectin plus 6 mg/kg diethylcarbamazine citrate (DEC), we performed pre- and post-treatment collections of freshly blood-engorged mosquitoes from the same nine bedrooms. All blood-fed mosquitoes collected less than 4 days after mass treatment died within 9 days, whereas 67% of those collected before treatment survived for >9 days. Comparison (using the log-rank test) of the survival curves for mosquitoes collected (i) before treatment, (ii)<4 days after treatment, and (iii) 28 days after treatment, showed the survival rate of group (ii) to be significantly lower than the other two (chi2=176, df=2, P<0.0001). Pre- and post-treatment all-night landing catches showed no reduction in human biting rates in the experimental village. In another village, where people were mass treated with ivermectin (400 microg/kg) only, the survival rates of freshly blood-engorged An. punctulatus collected from bedroom resting-sites less than 1 day after treatment, were compared to similar collections carried out at the same time in a nearby village where people were not treated with ivermectin. The 48-h survival rate for the ivermectin-treated village was 31% compared to 94% for the other; this difference was highly significant (chi2=32.42, df=1, P<0.0001). Mosquitoes fed 2 months post-treatment with DEC or collected 38 days post-treatment with ivermectin had normal survival rates. We conclude that the duration of the systemic lethal effect of ivermectin on mosquitoes is insufficient to be of epidemiological significance in filariasis control programmes that are based on biannual and annual single-dose treatments, but might reduce vectorial capacity sufficiently to block epidemics of dengue or even malaria.

Effects of Ivermectin on Blood-Feeding Phlebotomus papatasi, and the Promastigote Stage of Leishmania major

“…Mass treatment of IVM for filariasis control in Papua New Guinea produced blood levels that were toxic to mosquitoes of the An. punctulatus group (Bockarie et al 1999). Studies by Pampiglione et al (1985) that compared between three mosquito species found the insecticidal effect of IVM to be greater against anophelines than culicines.…”

Effect of Ivermectin onAnopheles gambiaeMosquitoes Fed on Humans: The Potential of Oral Insecticides in Malaria Control

“…The literature varies on the longevity of the insecticidal effect, with some finding a prolonged effect [10]. The effects of ivermectin on blood-sucking insects and parasites may be only loosely related to plasma concentration, possibly because of metabolites with longer half-lives [11,12]. Data on the pharmacokinetics of ivermectin in humans vary.…”

“…Experiments in animals and in vitro have shown that ivermectin readily kills adult mosquitoes, including anophelines [8,9]. In human trials of mass drug administration for onchocerciasis and filariasis, the effect of ivermectin on mosquitoes seems to be maintained in the field [10,11]. These insecticidal properties of ivermectin have led some to suggest that this drug could have a role in the control of arthropod vector-borne diseases.…”

Comparison of Methods for Xenomonitoring in Vectors of Lymphatic Filariasis in Northeastern Tanzania

“…5 Light traps are commonly used for the collection of mosquitoes for LF xenomonitoring, [6][7][8] and are usually placed indoors near a sleeping person who is protected with an untreated mosquito net. Other methods such as human landing catches have been used, 9 but this method is used less often due to ethical concerns. 10 Gravid traps have been used for the collection of mosquitoes for xenomonitoring, particularly in the United States for monitoring of Western Equine, St. Louis, and West Nile viruses.…”