Introduction

Homestead arthropod pests constitute biting nuisance, noise and stinging annoyance contamination of human foods and drinks as well as transmission of public health diseases to man. Such diseases include malaria, typhus fever, dysentery and cholera, yellow fever, dengue haemorrhagic fever, and a host of other arboviruses. Organochlorine and organophosphate insecticides used in controlling them are not only highly toxic to man but they are also not easily biodegradable in the environment and sometimes infiltrate into the food chain (Hill, 1987). Consequently the pyrethrum and their synthetic analogues (pyrethroids) that are easily biodegradable, environmentally friendly and practically less poisonous to mammals are being developed for the control of these pests (Pfadt, 1985). Among these pyrethroids are the commonly used alletrin, permenthrirl and ICON (Iambda-cyhalothrin) (Lines et al 1985, 1987, Rozendeal, 1989). These insecticides are costly and not easily available to the general populace who need them for the control of these pests (Okigbo and Igwe, 2007). To improve the situation, effort is directed to development of new pyrethroids that are not only effective but are also cheap and easily available. Some new products such as Ultrad® and Talstar® have been developed and tested. Most recently, Bistar® 10WP is developed and is being tested.

The aim of the present study was to determine the efficacy and persistence of Bistar® 10WP as residual insecticide for the control of household arthropod pests.

Materials and Methods

Bistar® 10WP is a wetable, colourless powder. It is odourless and non-irritating to both the body and sense organs. The active ingredients are Bifenthrin 10WP-10% and Inert ingredients-90%. Application was according to the manufacture’s instruction. About 62.5g of the wetable power was dissolved in 10 litres of clean water in a Hudson sprayer tank. The inner surfaces of living and sleeping rooms were sequentially sprayed in overlapping vertical columns until the surfaces were covered with insecticide. Crevices of household furniture including mattresses and furniture edges were sprayed to control bedbugs.

Preliminary Studies

Selection of spray sites

Ethical Considerations

Monitoring of Insecticide Activities

Bioassay Studies

Results

Preliminary Study

The preliminary study results revealed the abundance of homestead arthropod pests in the two urban slums (Table 1). A total of 532 arthropod pests were collected, 273(51.32%) from Ugbo-Oghe and 259(48.68%) from Agu-Owa. Bedbugs and cockroaches constituted a large bulk of the total collections in the two areas.

Figure 1

Table 1: Pre-spray collection of homestead arthropod pests at Agu-Owa and Ugbo-Oghe

Post-spray evaluation

Two days after spraying, collection of arthropod pests was carried out inside then sprayed rooms and the control rooms. None of the arthropod pests collected during the preliminary studies was collected in both places sprayed with either ICON or Bistar® 10WP. The only collections were from the control areas (Table 2).

Figure 2

Table 2: Post-spray collections of homestead arthropod pests at Ugbo-Oghe and Agu-Owa

Bioassay Test

The mortality of mosquitoes exposed to ICON and Bistar® 10WP sprayed walls is shown in table 3. After 2 weeks, the mortality rates of 3-days old adult Aedes aegypti mosquitoes exposed to ICON and Bistar® 10WP sprayed walls were 68.89% for ICON and 67.22% for Bistar® 10WP. At 4 weeks, the mortality rates were 28.8% for ICON and 25.00% for Bistar® 10WP. By the end of 6 weeks, the mortality rate for both ICON and Bistar® was 13.06% respectively.

Figure 3

Table 3: Mortality rates of mosquitoes exposed to ICON and Bistar® 10WP sprayed-walls at Ugbo-Oghe and Agu-Owa at biweekly intervals

Perception of the occupants of sprayed houses

Discussion

Bistar® 10WP compared well with ICON in its efficacy in knockdown and killing effects on the mosquitoes and other arthropod pests in the households. ICON is a pyrethrum-based standard insecticide used in common with permethrin, deltamethrin, resimethrin and other pyrethroids in mass malaria control programmes using insecticide impregnated bednets, 8 curtains for the control of mosquitoes in households (Sexton et al, 1990). Bistar® 10WP is also a pyrethrum based insecticide and like other pyrethroids, it has low mammalian toxicity, easily biodegradable without any record of insecticide resistance from insect vectors and pests (Snow et al., 1985). Unlike ICON which is irritating to the eyes and sense organs, Bistar® 10WP was highly accepted by the people as it was odourless and non-irritating to the sense organs. One hardly knew that an insecticide was sprayed in the area except by observing killed insects. Bistar® 10WP was also found as good as ICON in residuality indicating that Bistar® 10WP could be effective in preparation of insecticide impregnated bednets and curtains for the control of malaria and other vector-borne diseases. Many investigations have revealed that permethrin impregnated bednets and curtains have resulted in lower prevalence of malaria parasitaemia in children, fewer clinical episodes of fever, reduced spleen size and in some cases reduced malaria incidences and prevalence (Graves et al., 1987, Gouck et al., 1967 and Sexton et al., 1990). More studies is recommended on its effectiveness in aquatic conditions for the control of larval stages of mosquitoes and Simulium vectors of River blindness. It is also recommended for trial in field vectors such as Glossina species, houseflies and ticks.