The frequency of kdr and ace-1 alleles in Anopheles gambiae s.l. before and during indoor residual spraying (IRS) implementation and four years after IRS withdrawal in three districts in Atacora, Benin

BACKGROUND

Indoor residual spraying (IRS) was first implemented in the Atacora department, Benin from 2011 to 2012 using bendiocarb (carbamate) followed by annual spraying with pirimiphos-methyl (organophosphate) from 2013 to 2018. Before and after IRS implementation in Atacora, standard pyrethroid insecticide-treated bed nets were the main method of vector control in the area. This study investigated the knockdown resistance (kdr) gene (L1014F) and the acetylcholinesterase (ace-1) gene (G119S), before and during IRS implementation, and 4-years after IRS withdrawal from Atacora. This was done to assess how changes in insecticide pressure from indoor residual spraying may have altered the genotypic resistance profile of Anopheles gambiae s.l.

METHOD

Identification of sibling species of An. gambiae s.l. and detection of the L1014F mutation in the kdr gene and G119S mutation in ace-1 genes was done using molecular analysis. Allelic and genotypic frequencies were calculated and compared with each other before and during IRS implementation and 4 years after IRS withdrawal. The Hardy-Weinberg equilibrium and genetic differentiation within and between populations were assessed.

RESULTS

Prevalence of the L1014F mutation in all geographic An. gambiae s.l. (An. gambiae s.s., Anopheles. coluzzii, Anopheles. arabiensis, and hybrids of "An. gambiae s.s. and An. coluzzii") populations increased from 69% before IRS to 87% and 90% during and after IRS. The G119S allele frequency during IRS (20%) was significantly higher than before IRS implementation (2%). Four years after IRS withdrawal, allele frequencies returned to similar levels as before IRS (3%). Four years after IRS withdrawal, the populations showed excess heterozygosity at the ace-1 gene and deficit heterozygosity at the kdr gene, whereas both genes had excess heterozygosity before and during IRS (FIS < 0). No genetic differentiation was observed within the populations.

CONCLUSIONS

This study shows that the withdrawal of IRS with bendiocarb and pirimiphos-methyl may have slowed down the selection of individual mosquitoes with ace-1 resistance alleles in contrast to populations of An. gambiae s.l. with the L1014F resistance allele of the kdr gene. This may suggest that withdrawing the use of carbamates or organophosphates from IRS or rotating alternative insecticides with different modes of action may slow the development of ace-1 insecticide-resistance mutations. The increase in the prevalence of the L1014F mutation of the kdr gene in the population, despite the cessation of IRS, could be explained by the growing use of pyrethroids and DDT in agriculture and for other domestic use. More observational studies in countries where carbamates or organophosphates are still being used as public health insecticides may provide additional insights into these associations.

Assessing the susceptibility and efficacy of traditional neurotoxic (pyrethroid) and new-generation insecticides (chlorfenapyr, clothianidin, and pyriproxyfen), on wild pyrethroid-resistant populations of Anopheles gambiae from southern Benin

BACKGROUND

The objective of this study was to determine the susceptibility of wild Anopheles gambiae sensu lato (s.l.) from southern Benin to the new insecticides (chlorfenapyr (CFP), pyriproxyfen (PPF), and clothianidin (CTD)) and assess the efficacy of insecticide-treated bed nets (ITNs) that contain these new products.

METHODS

Wild An. gambiae from the Benin communes of Allada, Ifangni, Akpro-Missérété, and Porto-Novo were tested for their susceptibility to CFP and PPF using the WHO bottle tests, and pyrethroids (alpha-cypermethrin, deltamethrin, and permethrin) and CTD using WHO tube tests. WHO cone tests were used to evaluate the efficacy of Interceptor® (which contains alpha-cypermethrin (ACM) only), Interceptor® G2, (CFP + ACM), and Royal Guard® nets (PPF + ACM). The ovaries of blood-fed An. gambiae from Ifangni exposed to a new PPF net were dissected, and egg development status was examined using Christopher's stages to determine the fertility status of the mosquitoes. Using a standardized protocol, the oviposition rate and oviposition inhibition rate were calculated from live blood-fed An. gambiae placed in oviposition chambers after exposure to PPF.

RESULTS

In all four mosquito populations, pyrethroid mortality ranged from 5 to 80%, while chlorfenapyr and clothianidin mortality ranged from 98 to 100%. At Ifangni, all mosquitoes exposed to Royal Guard® nets were infertile (100%) while the majority (74.9%) of mosquitoes exposed to Interceptor® nets had fully developed their eggs to Christopher's stage V. The oviposition inhibition rate after exposure of the mosquitoes to the PPF was 99% for the wild population of An. gambiae s.l. and the susceptible laboratory strain, An. gambiae sensu stricto (Kisumu).

CONCLUSIONS

The results of this study suggest that pyrethroid-resistant An. gambiae from the selected communes in southern Benin are susceptible to chlorfenapyr, clothianidin, and pyriproxyfen. In addition, based on bioassay results, new and unused Interceptor® G2 and Royal Guard® nets were effective on Ifangni's mosquito populations. Despite the availability of new effective insecticides, continued vigilance is needed in Benin. Therefore, monitoring of resistance to these insecticides will continue to periodically update the Benin national insecticide resistance database and management plan.

Associations Between Mobility, Food Insecurity, and Transactional Sex Among Women in Cohabitating Partnerships: An Analysis From 6 African Countries 2016-2017

BACKGROUND

Mobile women are at risk of HIV infection in sub-Saharan Africa, although we lack evidence for HIV risk among women in mobile partnerships, especially in the context of household food insecurity, a growing concern in the region.

SETTING

Women aged 15-59 years with a cohabitating male partner who participated in population-based HIV impact assessment surveys in Eswatini, Lesotho, Namibia, Tanzania, Uganda, and Zambia.

METHODS

We evaluated the association between women's and their partner's mobility (being away from home for more than 1 month or staying elsewhere) and transactional sex (selling sex or receiving money or goods in exchange for sex). We examined associations for effect measure modification by food insecurity level in the household in the past month. We used survey-weighted logistic regression, pooled and by country, adjusting for individual, partner, and household-level variables.

RESULTS

Among women with a cohabitating male partner, 8.0% reported transactional sex, ranging from 2.7% in Lesotho to 13.4% in Uganda. Women's mobility [aOR 1.35 (95% CI: 1.08 to 1.68)], but not their partner's mobility [aOR 0.91 (0.74-1.12)], was associated with transactional sex. Food insecurity was associated with transactional sex independent of mobility [aOR 1.29 (1.10-1.52)]. Among those who were food insecure, mobility was not associated with increased odds of transactional sex.

CONCLUSION

Food insecurity and women's mobility each increased the odds of transactional sex. Because transactional sex is associated with HIV risk, prevention programs can address the needs of mobile and food-insecure women, including those in cohabitating relationships.

Food insecurity and the risk of HIV acquisition: findings from population-based surveys in six sub-Saharan African countries (2016-2017)

OBJECTIVE

To assess the potential bidirectional relationship between food insecurity and HIV infection in sub-Saharan Africa.

DESIGN

Nationally representative HIV impact assessment household-based surveys.

SETTING

Zambia, Eswatini, Lesotho, Uganda and Tanzania and Namibia.

PARTICIPANTS

112 955 survey participants aged 15-59 years with HIV and recency test results.

MEASURES

Recent HIV infection (within 6 months) classified using the HIV-1 limited antigen avidity assay, in participants with an unsuppressed viral load (>1000 copies/mL) and no detectable antiretrovirals; severe food insecurity (SFI) defined as having no food in the house ≥three times in the past month.

RESULTS

Overall, 10.3% of participants lived in households reporting SFI. SFI was most common in urban, woman-headed households, and in people with chronic HIV infection. Among women, SFI was associated with a twofold increase in risk of recent HIV infection (adjusted relative risk (aRR) 2.08, 95% CI 1.09 to 3.97). SFI was also associated with transactional sex (aRR 1.28, 95% CI 1.17 to 1.41), a history of forced sex (aRR 1.36, 95% CI 1.11 to 1.66) and condom-less sex with a partner of unknown or positive HIV status (aRR 1.08, 95% CI 1.02 to 1.14) in all women, and intergenerational sex (partner ≥10 years older) in women aged 15-24 years (aRR 1.23, 95% CI 1.03 to 1.46). Recent receipt of food support was protective against HIV acquisition (aRR 0.36, 95% CI 0.14 to 0.88).

CONCLUSION

SFI increased risk for HIV acquisition in women by twofold. Heightened food insecurity during climactic extremes could imperil HIV epidemic control, and food support to women with SFI during these events could reduce HIV transmission.

Screening for HIV Among Patients at Tuberculosis Clinics - Results from Population-Based HIV Impact Assessment Surveys, Malawi, Zambia, and Zimbabwe, 2015-2016

The World Health Organization and national guidelines recommend HIV testing and counseling at tuberculosis (TB) clinics for all patients, regardless of TB diagnosis (1). Population-based HIV Impact Assessment (PHIA) survey data for 2015-2016 in Malawi, Zambia, and Zimbabwe were analyzed to assess HIV screening at TB clinics among persons who had positive HIV test results in the survey. The analysis was stratified by history of TB diagnosis* (presumptive versus confirmed^†), awareness^§ of HIV-positive status, antiretroviral therapy (ART)^¶ status, and viral load suppression among HIV-positive adults, by history of TB clinic visit. The percentage of adults who reported having ever visited a TB clinic ranged from 4.7% to 9.7%. Among all TB clinic attendees, the percentage who reported that they had received HIV testing during a TB clinic visit ranged from 48.0% to 62.1% across the three countries. Among adults who received a positive HIV test result during PHIA and who did not receive a test for HIV at a previous TB clinic visit, 29.4% (Malawi), 21.9% (Zambia), and 16.2% (Zimbabwe) reported that they did not know their HIV status at the time of the TB clinic visit. These findings represent missed opportunities for HIV screening and linkage to HIV care. In all three countries, viral load suppression rates were significantly higher among those who reported ever visiting a TB clinic than among those who had not (p<0.001). National programs could strengthen HIV screening at TB clinics and leverage them as entry points into the HIV diagnosis and treatment cascade (i.e., testing, initiation of treatment, and viral load suppression).