The effect of permethrin impregnated bednets on the incidence of Plasmodium falciparum, in children of north Guadalcanal, Solomon Islands.

The effect of permethrin impregnated bednets was studied for the first time amongst a large community in North Guadalcanal, Solomon Islands. The community was divided into two; one covered 23 villages with 860 people who were given bednets impregnated at 0.5 g/m2, and the other 20 villages with 520 people was used as control. Parasitological data were collected by regular prevalence surveys and examination of records of malaria patients who have sought treatment in clinics. Entomological data by landing catches using human bait. The entomological results showed a 71% reduction of Anopheles farauti. Even though there was no significant reduction observed with An.punctulatus, as the density was already very low, the number biting indoor was much lower than those outdoor of houses with treated bednets. Parasitologically there was a steady decline in the incidence between surveys with Plasmodium falciparum in the under 10 years old. Even though there was no significant reduction in the other variables measured, there was a steady increase in the clearance rate between surveys which might also be due to easy accessibility to chemotherapy. The study showed the significant beneficial effect of permethrin impregnated bednets, which was found to be still effective up to twelve months, against stable P. falciparum malaria in children.

Seasonal abundance and biting behaviour of Anopheles punctulatus and An. koliensis in Malaita Province, Solomon Islands, and a trial of permethrin impregnated bednets against malaria transmission.

Seasonal abundance of the malaria vectors Anopheles punctulatus Dönitz and An.koliensis Owen in Bilimanu, an isolated inland village with forty-two houses in Malaita Province of the Solomon Islands, was monitored over 28 months by means of all-night landing/biting catches at one site during June 1985 to September 1987. Totals of 1250 An.punctulatus and 141 An.koliensis were collected, the latter being the largest number of this species ever caught at any locality in the Solomons. Bednets impregnated with permethrin 0.5 g/m2 were introduced in December 1986 to be used at night by all 190 villagers for protection against malaria vectors. Bioassay tests with An.punctulatus blood-fed females exposed under nets for 10 min resulted in 100% mortality up to 50 weeks post-impregnation. For An.punctulatus, the main vector species, the mean catch (indoors + outdoors) per man hour was 2.9 (range 0.7-13.2) before a cyclone on 19 May 1986, and, 0.66 (0.2-2.7) after the cyclone. The vector survival rates were usually high before the cyclone, but erratically lower thereafter for An.punctulatus. An.koliensis disappeared after the cyclone. Both An.punctulatus and An.koliensis consistently showed higher rates of biting man indoors than outdoors and their diel biting cycle showed a peak around midnight. Outdoors, the parous proportion of An.punctulatus was twice the nulliparous, and nearly so indoors. Following intervention with permethrin-treated bednets, the mean catch of An.punctulatus fell to 0.35 per man-hour (monthly range 0-1.5). The Plasmodium falciparum malaria infection rate reduced from 10% pre-intervention to zero in September 1987, 9 months after intervention, and then rose again.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of halofantrine and n-desbutylhalofantrine in patients with falciparum malaria following a multiple dose regimen of halofantrine.

Halofantrine is a new blood schizontocidal drug used for the treatment of multidrug-resistant falciparum malaria. The pharmacokinetics of halofantrine (HAL) and its principal metabolite, N-desbutylhalofantrine (BHAL), was investigated in 6 adult male patients of Melanesian origin with uncomplicated falciparum malaria. The patients received 500 mg of halofantrine hydrochloride at times 0, 6 and 12 h (total 1.5 g). All patients responded to treatment with a mean parasite clearance time of 52.7 h and a mean fever clearance time of 33.8 h. The following kinetic parameters (mean values) were determined for HAL and BHAL, respectively: maximum plasma concentration (Cmax) = 896 and 491 ng.ml-1; time to reach the Cmax (tmax) = 15 and 56 h; elimination half-life (t1/2) = 91 and 79 h and the mean residence time (MRT) = 71 and 102 h. Based on the clinical response the plasma concentrations of HAL and BHAL were adequate for the treatment of uncomplicated falciparum malaria in the 6 patients.