Efficacy of Bendiocarb Used for Indoor Residual Spraying for Malaria Control in Madagascar: Results With Local Anopheles Species (Diptera: Culicidae) From Experimental Hut Trials

Investigation of the efficacy of diosmin against organ damage caused by bendiocarb in male Wistar albino rats

Bendiocarb is a carbamate insecticide, which is used more in indoor areas, especially against scorpions, spiders, flies, mosquitoes and cockroaches. Diosmin is an antioxidant flavonoid found mostly in citrus fruits. In this study, the efficacy of diosmin against the adverse effects of bendiocarb was investigated in rats. For this purpose, 60, 2-3 month-old male Wistar albino rats, weighing 150-200 g, were used. The animals were assigned to six groups, one of which was maintained for control purposes and five of which were trial groups. The control rats received only corn oil, which was used as a vehicle for diosmin administration in the trial groups. Groups 2, 3, 4, 5 and 6 were administered with 10 mg/kg.bw bendiocarb, 10 mg/kg.bw diosmin, 20 mg/kg.bw diosmin, 2 mg/kg.bw bendiocarb plus 10 mg/kg.bw diosmin, and 2 mg/kg.bw bendiocarb plus 20 mg/kg.bw diosmin, respectively, using an oral catheter, for 28 days. At the end of the study period, blood and organ (liver, kidneys, brain, testes, heart and lungs) samples were collected. Body weight and organ weights were determined. Compared to the control group, in the group given bendiocarb alone, firstly, body weight and liver, lung and testicular weights decreased. Secondly, tissue/plasma malondialdehyde (MDA) and nitric oxide (NO) levels increased, and glutathione (GSH) levels and superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) (except for lung tissue), glutathione reductase (GR), and glucose-6-phosphate dehydrogenase (G6PD) activities decreased in all tissues and erythrocytes. Thirdly, catalase (CAT) activity decreased in erythrocytes and the kidney, brain, heart and lung tissues and increased in the liver and testes. Fourthly, while GST activity decreased in the kidneys, testes, lung and erythrocytes, an increase was observed in the liver and heart tissues. Fifthly, while serum triglyceride levels and lactate dehydrogenase (LDH), alkaline phosphatase (ALP) and pseudo-cholinesterase (PchE) activities decreased, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities and blood urea nitrogen (BUN), creatinine and uric acid levels increased. Lastly, liver caspase 3, caspase 9 and p53 expression levels significantly increased. When compared to the control group, the groups treated with diosmin alone showed no significant difference for the parameters investigated. On the other hand, it was observed that the values of the groups treated with a combination of bendiocarb and diosmin were closer to the values of the control group. In conclusion, while exposure to bendiocarb at a dose of 2 mg/kg.bw for 28 days caused oxidative stress/organ damage, diosmin administration at doses of 10 and 20 mg/kg.bw reduced this damage. This demonstrated that diosmin has pharmaceutical benefits, when used for supportive treatment as well as radical treatment, against the potential adverse effects of bendiocarb.

Bioefficacy of bendiocarb WP80 in vector-borne and zoonotic diseases areas in borderline of Iran and Pakistan

Malaria and leishmaniasis are the public health problems in southern Iran. The main activity of vector control is indoor residual spraying using pyrethroids, using different insecticides as larviciding and impregnated bednets. The aim of study was to evaluate the biological assays of bendiocarb wettable powder (WP) at different surfaces of wall. The residual effect of bendiocarb WP80 at 400 milligram/meter square (mg/m²) was evaluated on various local surfaces of rooms such as mud and plaster as well as thatch roofs and wooden. World Health Organization standard cones using contact bioassays were carried out using laboratory reared sugar-fed, 48-72 h old females of Anopheles stephensi. Contact bioassays were carried out on sprayed surfaces for 150 days. Contact bioassay on surfaces treated with bendiocarb WP80 at different surfaces was estimated about 2 months. Fumigant tests of bendiocarb WP80 at 400 mg/m² revealed 50-93.83% mortality with 1 month persistency. The results showed that carbamate insecticide could be used as rotation with pyrethroids for malaria vector control. Monitoring and evaluation of environmental toxicology of pesticides is important for decision making for choosing appropriate pesticides for disease vector control.

Estimating the optimal interval between rounds of indoor residual spraying of insecticide using malaria incidence data from cohort studies

Background

Indoor residual spraying (IRS) reduces vector densities and malaria transmission, however, the most effective spraying intervals for IRS have not been well established. We estimated the optimal timing interval for IRS using a statistical approach.

Methods

Six rounds of IRS were implemented in Tororo District, a historically high malaria transmission setting in Uganda, during the study period (3 rounds with bendiocarb active ingredient (Ficam®): December 2014 to December 2015, and 3 rounds with pirimiphos methyl active ingredient (Actellic 300®CS): June 2016 to July 2018). A generalized additive model was used to estimate the optimal timing interval for IRS based on the predicted malaria incidence. The model was fitted to clinical incidence data from a cohort of children aged 0.5–10 years from selected households observed throughout the study period.

Results

494 children, 67% aged less than 5 years at enrolment were analysed. Six-months period incidence of malaria decreased from 2.96 per person-years at the baseline to 1.74 following the first round of IRS and then to 0.02 after 6 rounds of IRS. The optimal time interval for IRS differed between bendiocarb and pirimiphos methyl and by IRS round. To retain an optimum impact, bendiocarb would require respraying 17 (95% CI: 14.2–21.0) weeks after application whereas pirimiphos methyl could remain impactful for 40 (95% CI: 37.0–42.8) weeks, although in the final year this estimates 36 (95% CI: 32.7–37.7) weeks. However, we could not estimate from the data the optimal time after the second and third rounds of bendiocarb and after the second round of pirimiphos methyl. Neither the amount of rainfall nor the EIR nor the distribution of nets were found to be statistically significant for determining the time period between spray rounds.

Conclusion

In our setting, the effect of the two IRS products was distinct. Statistically, pirimiphos methyl provided a longer window of protection than bendiocarb, although impact varied between different spray rounds and years which was not explained by rainfall or EIR or distribution of nets in our statistical approach. Understanding the effectiveness of IRS and how long it lasts can help for planning campaigns, but one should consider the financial cost and insecticide resistance. Monitoring the timing of spray campaigns using clinical incidence could be repeated in future programs to help determine the average period of protectivity of these products.

Efficacy of insecticides used in indoor residual spraying for malaria control: an experimental trial on various surfaces in a "test house"

Background

Malaria is a public health problem in the Brazilian Amazon region. In integrated vector management for malaria (anopheline) control, indoor residual spraying (IRS) represents one of the main tools in the basic strategy applied in the Amazonian states. It is essential to understand the residual efficacy of insecticides on different surfaces to determine spray cycles, ensure their rational use, and prevent wastage. This study aimed to evaluate the residual efficacy of six insecticide formulations used in the National Malaria Control Programme on four different types of walls in a field simulation at a “test house”.

Methods

The tests were performed as a field-simulating evaluation at a “test house” built in the municipality of Macapá. Six insecticide formulations comprising four pyrethroids, a carbamate, and an organophosphate were used, and evaluated when applied on different wall surfaces: painted wood, unpainted wood, plastered cement, and unplastered cement. The insecticides were applied to the interior walls of the “test house” by a trained technician.

Results

In the bioassays performed with pyrethroids, deltamethrin water-dispersible granules (WG) performed particularly well, presenting residual bioefficacy of 8 months on both wood surfaces after the IRS, whereas alpha-cypermethrin suspension concentrate (SC) and etofenprox wettable powder (WP) demonstrated residual bioefficacy of 4 months on at least one of the wood surfaces; however, the pyrethroid lambda-cyhalothrin WP showed a low residual bioefficacy (< 3 months) on all tested surfaces, demonstrating its inefficiency for areas with a long transmission cycle of malaria. For the carbamate-bendiocarb WP, residual bioefficacy for 3 months was achieved only on wood surfaces. In general, the organophosphate pirimifos-methyl capsule suspension (CS) demonstrated the best result, with a mortality rate < 80% over a period of 6 months on all surfaces tested.

Conclusion

Insecticide efficiency varies among different types of surface; therefore, a “test house” is a valuable evaluation tool. This work highlights the usefulness of associating the residual efficacy of insecticides on the surfaces commonly found in houses in endemic areas, together with knowledge about the transmission cycle duration of the transmission cycle and the insecticide susceptibility of the vector. This association helps in the decision-making for the malaria control intervention regarding.