Bio- ecological studies of life history traits of Anopheles Gambiae S.L. immature stages with specific reference to feeding preference, and the insecticide resistance status in southern Ghana : implications for malaria control

Malaria is one of the leading causes of morbidity and mortality in sub Saharan Africa. Currently, malaria vector control measures are faced with setbacks and hence are failing. One of the effective ways of controlling malaria in Africa is the use of long lasting insecticide treated nets (LLINS) and indoor residual spraying (IRS). Over the years the National Malaria Control programs have become focused on strategies targeting the mosquito vectors and hence has scaled up distribution of insecticide treated nets and indoor residual spraying campaigns (WHO, 2012). Yet the robustness and the integrity of LLIN and IRS in vector control is threatened by the development of insecticide resistance to pyrethroids. However, although resistance bioassays exist and are regularly used to assess phenotypic resistance, the fitness of the mosquitoes used and how it affects the results of the bioassays is unknown. The aim of this study is to determine the effect of five different feeding regimes on some life history traits of Anopheles gambiae and also profile the insecticide resistance levels in population of An. gambiae from the same area. A water bath was used to control larval rearing temperature as the effect of Rabbit pellet (no. 001131 Agrifeed, Kumasi, Ghana.), Fish flakes (Lopis Fish flakes™), Cerelac maize (Nestle®), Cat meal (Purina Friskies®) and Baking yeast on pupation rate, pupal weight , larval developmental time, Larval survivors ship was determined. The insecticide resistance on the urban agricultural setting in Opeibea, Accra was also investigated. Molecular techniques were used to identify mosquito species and screened for kdr and Ace-1 mutation. A high pupation rate (21.22%), larval survivorship (24%), pupal weight (2.353mg) and short larval developmental time (8 days) were obtained when the larvae was fed with rabbit pellet. The performance of rabbit pellet and fish flakes on the various life history trait was statistically different from Cerelac and yeast. However, the performance of fish flakes was insignificantly different from the life history traits of larvae fed xiii with cat meal. Molecular screening for kdr and Ace-1 mutation indicated a high occurrence of L1014F kdr (109) and Ace-1 R (80%) allele frequency which corresponded with the high phenotypic resistance and the use of insecticide by the famers. Bioassay revealed a high resistance (*RR) Anopheles gambiae s.s population at the vegetable farms in Opeibea. The S and M forms of An. gambiae s.s. was observed to occur in sympatry at Opeibea with a higher frequency of (78.95%) S form. The farmers use Fenitrothion, Deltamethrin, Emamectin Benzoate, Imidacloprid and Fenvalevrate in growing their vegetables. Rabbit pellets is highly recommended for use in the rearing of Anopheles gambiae s.s larvae in the insectary and the level of resistance at the urban agricultural setting in Opeibea indicates that practices such as indiscriminate use of insecticides may be helping in the development of resistance and needs to be controlled and monitored.

Source: KNUST