Background: The accuracy of malaria diagnosis has received renewed interest in recent years due to changes in treatment policies in favour of relatively high-cost artemisinin-based combination therapies. The use of rapid diagnostic tests (RDTs) based on histidine-rich protein 2 (HRP2) synthesized by Plasmodium falciparum has been widely advocated to save costs and to minimize inappropriate treatment of non-malarial febrile illnesses. HRP2-based RDTs are highly sensitive and stable; however, their specificity is a cause for concern, particularly in areas of intense malaria transmission due to persistence of HRP2 antigens from previous infections.

BackgroundUganda’s malaria burden includes the sixth highest number of annual deaths in Africa (10,500) with approximately 16 million cases (2013) and the entire population at risk. The President’s Malaria Initiative has been supporting the malaria control interventions of indoor residual spraying (IRS) and distribution of long-lasting insecticidal nets (LLIN) in Uganda since 2007. These interventions are threatened by emerging and spreading insecticide resistance, known to exist in Ugandan malaria vectors. Pyrethroid insecticides have been used in agriculture since the early 1990s and in IRS programmes from the mid-2000s until 2010. A universal LLIN coverage campaign was executed in 2013–2014, distributing pyrethroid-treated LLINs throughout the country. This study investigated insecticide susceptibility, intensity, and oxidase detoxification in Anopheles gambiae sensu lato and Anopheles funestus to permethrin and deltamethrin in four eastern Ugandan sites.MethodsThe susceptibility status of An. gambiae and An. funestus to bendiocarb, permethrin and deltamethrin was determined using the CDC (Centers for Disease Control and Prevention) bottle bioassay. Presence of oxidative enzyme detoxification mechanisms were determined by pre-exposing mosquitoes to piperonyl butoxide followed with exposure to discriminating doses of deltamethrin- and permethrin-coated CDC bottles. Resistance intensity was investigated using serial dosages of 1×, 2×, 5× and 10× the diagnostic dose and scored at 30 min to determine the magnitude of resistance to both of these LLIN pyrethroids. Testing occurred in the Northern and Eastern Regions of Uganda.ResultsAnopheles gambiae and An. funestus were fully susceptible to bendiocarb where tested. Anopheles gambiae resistance to deltamethrin and permethrin was observed in all four study sites. Anopheles funestus was resistant to deltamethrin and permethrin in Soroti. Oxidative resistance mechanisms were found in An. gambiae conferring pyrethroid resistance in Lira and Apac. 14.3% of An. gambiae from Tororo survived exposure of 10× concentrations of permethrin.ConclusionsBoth An. gambiae and An. funestus are resistant to pyrethroids but fully susceptible to bendiocarb at all sites. Susceptibility monitoring guided the Ministry of Health’s decision to rotate between IRS insecticide classes. Intensity bioassay results may indicate encroaching control failure of pyrethroid-treated LLINs and should inform decision-makers when choosing LLINs for the country.

Background In 2017, more than 5 million house structures were sprayed through the U.S. President’s Malaria Initiative, protecting more than 21 million people in sub-Saharan Africa. New IRS formulations, SumiShield™ 50WG and Fludora Fusion™ WP-SB, became World Health Organization (WHO) prequalified vector control products in 2017 and 2018, respectively. Both formulations contain the neonicotinoid active ingredient, clothianidin. The target site of neonicotinoids represents a novel mode of action for vector control, meaning that cross-resistance through existing mechanisms is less likely. In preparation for rollout of clothianidin formulations as part of national IRS rotation strategies, baseline susceptibility testing was conducted in 16 countries in sub-Saharan Africa. Methods While work coordinated by the WHO is ongoing to develop a suitable bottle bioassay procedure, there was no published guidance regarding clothianidin susceptibility procedures or diagnostic concentrations. Therefore, a protocol was developed for impregnating filter papers with 2% w/v SumiShield™ 50WG dissolved in distilled water. Susceptibility tests were conducted using insectary-reared reference Anopheles and wild collected malaria vector species. All tests were conducted within 24 h of treating papers, with mortality recorded daily for 7 days, due to the slow-acting nature of clothianidin against mosquitoes. Anopheles gambiae sensu lato (s.l.) adults from wild collected larvae were tested in 14 countries, with wild collected F 0 Anopheles funestus s.l. tested in Mozambique and Zambia. Results One-hundred percent mortality was reached with all susceptible insectary strains and with wild An. gambiae s.l. from all sites in 11 countries. However, tests in at least one location from 5 countries produced mortality below 98%. While this could potentially be a sign of clothianidin resistance, it is more likely that the diagnostic dose or protocol requires further optimization. Repeat testing in 3 sites in Ghana and Zambia, where possible resistance was detected, subsequently produced 100% mortality. Results showed susceptibility to clothianidin in 38 of the 43 sites in sub-Saharan Africa, including malaria vectors with multiple resistance mechanisms to pyrethroids, carbamates and organophosphates. Conclusions This study provides an interim diagnostic dose of 2% w/v clothianidin on filter papers which can be utilized by National Malaria Control Programmes and research organizations until the WHO concludes multi-centre studies and provides further guidance. Electronic supplementary material The online version of this article (10.1186/s12936-019-2888-6) contains supplementary material, which is available to authorized users.

BackgroundThere are major concerns over sustaining the efficacy of current malaria vector control interventions given the rapid spread of resistance, particularly to pyrethroids. This study assessed the bioefficacy of five WHO-recommended long-lasting insecticidal nets (LLINs) against pyrethroid-resistant Anopheles gambiae field populations from Uganda.MethodsAdult An. gambiae from Lira, Tororo, Wakiso and Kanungu districts were exposed to permethrin (0.75%) or deltamethrin (0.05%) in standard WHO susceptibility tests. Cone bioassays were used to measure the bioefficacy of four mono-treated LLINs (Olyset®, Interceptor®, Netprotect® and PermaNet® 2.0) and one combination LLIN (PermaNet® 3.0) against the four mosquito populations. Wireball assays were similarly conducted to determine knockdown rates. Species composition and kdr mutation frequency were determined for a sample of mosquitoes from each population. Chemical assays confirmed that test nets fell within target dose ranges.ResultsAnopheles gambiae s.s. predominated at all four sites (86 - 99% of Anopheles spp.) with moderate kdr L1014S allelic frequency (0.34 – 0.37). Confirmed or possible resistance to both permethrin and deltamethrin was identified for all four test populations. Reduced susceptibility to standard LLINs was observed for all four populations, with mortality rates as low as 45.8% even though the nets were unused. The combination LLIN PermaNet®3.0 showed the highest overall bioefficacy against all four An. gambiae s.l. populations (98.5 - 100% mortality). Wireball assays provided a more sensitive indicator of comparative bioefficacy, and PermaNet 3.0 was again associated with the highest bioefficacy against all four populations (76.5 – 91.7% mortality after 30 mins).ConclusionsThe bioefficacy of mono-treated LLINs against pyrethroid-resistant field populations of An. gambiae varied by LLIN type and mosquito population, indicating that certain LLINs may be more suitable than others at particular sites. In contrast, the combination LLIN PermaNet 3.0 performed optimally against the four An. gambiae populations tested. The observed reduced susceptibility of malaria vectors to mono-treated LLINs is of particular concern, especially considering all nets were unused. With ongoing scale-up of insecticidal tools in the advent of increasing resistance, it is essential that those interventions with proven enhanced efficacy are given preference particularly in areas with high resistance.

Summary Malaria is a key health problem among displaced populations in malariaendemic areas. Mass distribution of insecticide-treated bednets (ITN) to prevent malaria is often carried out in complex emergencies, but there are few data on the outcome or operational effectiveness of such programmes. In June 2001, Médecins Sans Frontières completed a mass distribution of ITNs (Permanet ® ) to internally displaced persons in Bundibugyo, southwest Uganda, distributing one to four nets per household, and aiming to provide coverage for all residents. In July 2002, we did a cross-sectional survey using three-stage cluster sampling to evaluate the programme. A total of 1245 individuals from 835 households were interviewed. An ITN was present in 75.6% (95% CI 72.7-78.5) of the households, but only 56.5% (95% CI 52.3-60.4) of individuals were sleeping under an ITN, and nets were often damaged. The prevalence of malarial parasitaemia was 11.2% (95% CI 9.4-13.0), and was significantly lower in ITN users compared to non-users (9.2% vs. 13.8%, relative risk [RR] 0.63, 95% CI 0.46-0.87); ITNs with severe damage remained effective (RR for severely damaged net 0.58, 95% CI 0.35-0.98). There was no significant difference in haemoglobin concentration between ITN users and non-users.