The Impact of Insecticide Pre-Exposure on Longevity, Feeding Succession, and Egg Batch Size of Wild Anopheles gambiae s.l.

Abstract

Background. Insecticide resistance among the vector population is the main threat to existing control tools available. The current vector control management options rely on applications of recommended public health insecticides, mainly pyrethroids through long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). Regular monitoring of insecticide resistance does not provide information on important factors that affect parasite transmission. Such factors include vector longevity, vector competence, feeding success, and fecundity. This study investigated the impacts of insecticide resistance on longevity, feeding behaviour, and egg batch size of Anopheles gambiae s.l. Method. The larval sampling was conducted in rice fields using a standard dipper (350 ml) and reared to adults in field insectary. A WHO susceptibility test was conducted using standard treated permethrin (0.75%) and deltamethrin (0.05%) papers. The susceptible Kisumu strain was used for reference. Feeding succession and egg batch size were monitored for all survivors and control. Results. The results revealed that mortality rates declined by 52.5 and 59.5% for permethrin and deltamethrin, respectively. The mortality rate for the Kisumu susceptible strain was 100%. The survival rates of wild An. gambiae s.l. was between 24 and 27 days. However, the Kisumu susceptible strain blood meal feeding was significantly higher than resistant colony (t = 2.789, df = 21, P = 0.011 ). Additionally, the susceptible An. gambiae s.s. laid more eggs than the resistant An.gambiae s.l. colony (Χ2 = 1366, df = 1, P ≤ 0.05 ). Conclusion. It can, therefore, be concluded that the wild An. gambiae s.l. had increased longevity, blood feeding, and small egg batch size compared to Kisumu susceptible colonies.

Reduced performance of community bednets against pyrethroid-resistant Anopheles funestus and Anopheles gambiae, major malaria vectors in Cameroon

“…The physical condition of each LLIN collected was recorded according to the size of holes, and size 1 holes were found to be the most prevalent on all sides of the nets. The proportional hole index [ 37 ] allowed each LLIN to be categorized as: either “good,” acceptable” or “torn.” Accordingly, 30% of the LLINs were classified as good, 40% as acceptable and 30% as torn and requiring replacement as soon as possible. However, the percentage of nets still usable in the village (good + acceptable) was 70%.…”

Impact of insecticide resistance on malaria vector competence: a literature review

“…funestus. Globally, the findings revealed a pleitropic effect of insecticide resistance on mosquito lifespan [33,[96][97][98][99][100][101][102][103][104][105][106][107][108] (Table 2). The majority of studies (10/14) which used laboratory strains showed that pyrethroid resistant An.…”

“…It was reported that pre-exposure to insecticide in a manner micmicing field exposure to insecticides, affects the longevity of insecticide resistant An. gambiae strain [ 97 ], and that delayed mortality observed in the vectors may be dependent on resistance intensity [ 98 ]. This later observation indicates that findings obtained with laboratory colonies are to be taken with caution given that they may not reflect exactly what is oberved on the field [ 26 ].…”

Reduced performance of community bednets against pyrethroid-resistant Anopheles funestus and Anopheles gambiae, major malaria vectors in Cameroon

“…This revealed that size 1 holes were most prevalent on all sides of the nets. The proportional hole index (37) allowed each LLIN to be categorised as: either 'good, acceptable or torn'. Thus, 40% of the LLINs were classi ed as acceptable; 30% as good and 30% as torn requiring replacement as soon as possible.…”