The Absence of Abdominal Pigmentation in Livestock Associated Culicoides following Artificial Blood Feeding and the Epidemiological Implication for Arbovirus Surveillance

Culicoides midges (Diptera: Ceratopogonidae), the vectors of economically important arboviruses such as bluetongue virus and African horse sickness virus, are of global importance. In the absence of transovarial transmission, the parity rate of a Culicoides population provides imperative information regarding the risk of virus dispersal. Abdominal pigmentation, which develops after blood feeding and ovipositioning, is used as an indicator of parity in Culicoides. During oral susceptibility trials over the last three decades, a persistent proportion of blood engorged females did not develop pigment after incubation. The present study, combining a number of feeding trials and different artificial feeding methods, reports on this phenomenon, as observed in various South African and Italian Culicoides species and populations. The absence of pigmentation in artificial blood-fed females was found in at least 23 Culicoides species, including important vectors such as C. imicola, C. bolitinos, C. obsoletus, and C. scoticus. Viruses were repeatedly detected in these unpigmented females after incubation. Blood meal size seems to play a role and this phenomenon could be present in the field and requires consideration, especially regarding the detection of virus in apparent “nulliparous” females and the identification of overwintering mechanisms and seasonally free vector zones.

Impacts of ivermectin mass drug administration for onchocerciasis on mosquito populations of Ogun state, Nigeria

Background The impact of single-dose mass drug administration (MDA) of ivermectin for onchocerciasis on mosquito populations was investigated in Ogun State, Nigeria. Methods Indoor and outdoor collection of mosquitoes was carried out in two intervention (IC) and two control communities (CC) at three different periods: pre-MDA (baseline), 2–3 days after MDA and 13–14 days after MDA. The density and parity rate of female Anopheles and Culex mosquitoes were determined and compared. Environmental and climatic data of study locations were obtained to perform generalized linear model analysis. Results A total of 1399 female mosquitoes were collected, including 1227 Anopheles and 172 Culex mosquitoes. There was a similar magnitude of reduction in the indoor density of Anopheles by 29% in the IC and CC 2–3 days post-MDA but the reduction in indoor parity rate was significantly higher (p = 0.021) in the IC, reducing by more than 50%. In the IC, observation of a significant reduction at 2–3 days post-MDA was consistent for both the indoor density (1.43 to 1.02) and indoor parity rate (95.35% to 44.26%) of Anopheles mosquitoes. The indoor parity rate of Anopheles remained significantly reduced (75.86%) 13–14 post-MDA. On the other hand, the indoor density of Culex increased from 0.07 to 0.10 at 2–3 days post-MDA while the indoor parity rate of Culex did not change. The outdoor density of Anopheles in the IC increased (p = 0.394) from 0.58 to 0.90 at 2–3 days post-MDA; a similar observation was consistent for the outdoor density (2.83 to 3.90) and outdoor parity rate (70.59% to 97.44%) of Culex, while the outdoor parity rate of Anopheles reduced from 85.71 to 66.67% at 2–3 days post-MDA. A generalized linear model showed that ivermectin MDA significantly caused a reduction in both the indoor density (p < 0.001) and indoor parity rate (p = 0.003) of Anopheles in the IC. Conclusion Ivermectin MDA resulted in the reduction of both the survival and density of Anopheles mosquitoes. This has strong implications for malaria transmission, which depends strongly on vector survival. Graphic abstract

Impacts of Ivermectin Mass Drug Administration for Onchocerciasis on Mosquito Populations of Ogun State, Nigeria.

Background: This study investigated the impacts of single-dose mass drug administration (MDA) with ivermectin for onchocerciasis and lymphatic filariasis on mosquito populations in Ogun State, Nigeria. Methods: Mosquito samples were collected indoor and outdoor in two communities before and after MDA. The communities were pair-matched with two other control communities where concurrent mosquito collection was also carried out. The mosquitoes were identified by morphological features and parity status was determined by microscopy. The density and age structure of the mosquitoes were determined and compared between intervention and control communities. Environmental and climatic data of study locations were obtained from online databases. MDA treatment coverage survey was conducted in the treated communities. Results: Before MDA, the density of indoor Anopheles mosquitoes was 7.20 in the control communities. This was significantly lower (p = 0.049) in the intervention communities where the density was 1.43. The density of the indoor Anopheles population reduced significantly 2-3 days after MDA to 1.02 (p = 0.039) in the intervention communities. Parity rate also reduced significantly from 95.35 to 44.26 (p < 0.001). The density of indoor Anopheles rebounded to 1.45 two weeks after MDA while parity rate remained significantly lower (p = 0.001) than before MDA. The density of indoor Culex increased 2-3 days after MDA from 0.07 to 0.10 (p = 0.527) and to 0.25 (p = 0.012) 13-14 days after MDA in the intervention communities. In Amini where MDA coverage was 65.9%, the indoor density of Anopheles reduced significantly from 0.90 to 0.33 (p = 0.005) 2-3 days after MDA while in Kugba-Ajagbe where MDA coverage was 41.0%, the reduction from 1.97 to 1.70 was not statistically significant (p = 0.446). Exposure to MDA across sampling intervals in the intervention communities showed a significant effect on the density (p < 0.001) and parity rate (p = 0.003) of indoor Anopheles in the generalized linear model examining multiple factors. Conclusion: Ivermectin MDA showed a promising potential to impact on malaria transmission and Anopheles abundance at high MDA coverage.

Influence of a Major Mountainous Landscape Barrier (Mount Cameroon) on the Spread of Metabolic (GSTe2) and Target-Site (Rdl) Resistance Alleles in the African Malaria Vector Anopheles funestus

Increased levels of insecticide resistance in major malaria vectors such as Anopheles funestus threaten the effectiveness of insecticide-based control programmes. Understanding the landscape features impacting the spread of resistance makers is necessary to design suitable resistance management strategies. Here, we examined the influence of the highest mountain in West Africa (Mount Cameroon; 4095 m elevation) on the spread of metabolic and target-site resistance alleles in An. funestus populations. Vector composition varied across the four localities surveyed along the altitudinal cline with major vectors exhibiting high parity rate (80.5%). Plasmodium infection rates ranged from 0.79% (An. melas) to 4.67% (An. funestus). High frequencies of GSTe2R (67–81%) and RdlR (49–90%) resistance alleles were observed in An. funestus throughout the study area, with GSTe2R frequency increasing with altitude, whereas the opposite is observed for RdlR. Patterns of genetic diversity and population structure analyses revealed high levels of polymorphisms with 12 and 16 haplotypes respectively for GSTe2 and Rdl. However, the reduced diversity patterns of resistance allele carriers revealed signatures of positive selection on the two genes across the study area irrespective of the altitude. Despite slight variations associated with the altitude, the spread of resistance alleles suggest that control strategies could be implemented against malaria vectors across mountainous landscapes.

Influence of a Major Mountainous Landscape Barrier (Mount Cameroon) on the Spread of Metabolic (GSTe2) and Target-Site (Rdl) Resistance Alleles in the African Malaria Vector Anopheles funestus

Increased levels of insecticide resistance in major malaria vectors such as Anopheles funestus threaten the effectiveness of insecticide-based control programmes. Understanding the landscape features impacting the spread of resistance makers is necessary to design suitable resistance management strategies. Here we examined the influence of the highest mountain in West Africa (Mount Cameroon; 4,100 meters elevation) on the spread of metabolic and target-site resistance alleles in An. funestus populations. Vector composition varied across the four localities surveyed along the altitudinal cline with major vectors exhibiting high parity rate (80.5%). Plasmodium infection rates ranged from 0.79% (An. melas) to 4.67% (An. funestus). High frequencies of GSTe2R (67% - 81%) and RdlR (49% - 90%) resistance alleles were observed in An. funestus throughout the study area, with GSTe2R frequency increasing with altitude whereas the opposite is observed for RdlR. Patterns of genetic diversity and population structure analyses revealed high levels of polymorphisms with 12 and 16 haplotypes respectively for GSTe2 and Rdl. However, the reduced diversity patterns of resistance allele carriers revealed signatures of positive selection on the two genes across the study area irrespective of the altitude. Despite slight variations associated with the altitude, the spread of resistance alleles suggest that control strategies could be implemented against malaria vectors across mountainous landscapes.

4102 Assessment of ivermectin-treated backyard chickens as a novel urban West Nile virus prevention strategy

OBJECTIVES/GOALS: We conducted a randomized field trail to evaluate the efficacy and safety of a novel vector control strategy that involves treating urban backyard chickens with ivermectin (IVM), a widely used antiparasitic and mosquitocial drug. The goal was to reduce vector mosquito populations and West Nile virus (WNV) transmission. METHODS/STUDY POPULATION: We placed eight flocks—four treated and four untreated control—of six Lohmann brown chickens (16 month-old) each in backyard coops across Davis, CA and administered IVM in feed daily at treated coops (200 mg IVM/kg feed) for eleven weeks. We monitored entomological indices weekly (i.e. mosquito abundance, WNV infection prevalence, and parity rate) in Culex mosquito populations near (10 m) and far (150 m) from each coop location for the peak WNV transmission season (Jul-Sep 2019). We also monitored serum IVM levels in treated chickens and tested for WNV antibodies in all chickens throughout the study. RESULTS/ANTICIPATED RESULTS: Since IVM impacts only mosquitoes that live long enough to take a bloodmeal from a treated chicken, we do not expect to find a marked difference in adult Culex abundance between the two treatment arms, but we expect to find a reduction in WNV infection prevalence and a shift in female mosquito age structure towards younger, uninfected individuals at treated coops. We also anticipate seroconversions in treated chickens to occur at lower rates versus untreated control chickens indicating a reduction in WNV transmission intensity at treated coops. We observed no negative health outcomes from the long-term ingestion of IVM by study chickens. A pathological investigation is underway to compare histological findings between treated and untreated chickens. DISCUSSION/SIGNIFICANCE OF IMPACT: IVM provides the potential for targeted mosquito control. Reduced WNV transmission dynamics here is a stepping stone to a commercial WNV control strategy; IVM-treated feed for wild birds for homeowners’ use to combat WNV transmission in their neighborhoods.

Monthly dynamics and biting behavior of principal onchocerciasis vector (Simulium damnosum s.l.) in endemic area of Southwest Ethiopia

Background and Aim: Vector-borne diseases are the major causes of morbidity and mortality in several regions, especially in tropical and subtropical countries. This study aimed to compare the relative abundance, diversity, monthly biting rates, and parity rate of onchocerciasis vector collected from three small rivers in Southwest Ethiopia. Materials and Methods: Adult Simulium were collected using human landing catch with protected by the Mosq Tent for 4 consecutive days per month from 7 a.m. to 6 p.m. from January 2018 to December 2018 at three communities: Dizi, Agalo Uka, and Haro Magela. Chi-square test was used to determine the association between study site villages and abundances of the Simulium diversity. Results: During the study period, a total of 15,264 Simulium belong to two species Simulium damnosum sensu lato and Simulium neavei were collected. The monthly dynamics of S. damnosum sensu lato shows that the highest density of flies was observed in August, followed by July, whereas the lowest was observed in April. On the other hand, the highest peak biting hour was observed between 4 p.m. and 6 p.m., while the lowest hourly activity of the fly was recorded from 7 a.m. to 8 a.m. Furthermore, the highest parity rate was observed 82.2% in July followed by 80.9% in August while the lowest rate was observed 43.7% in January. Conclusion: This information on onchocerciasis vectors seasonal variation, diversity, parity, and biting time are important factors that to be considered for noticeable suggestions in monitoring transmission levels to guide the regional and national onchocerciasis elimination programs in Ethiopia.

Efficacy of Actellic 300 CS-based indoor residual spraying on key entomological indicators of malaria transmission in Alibori and Donga, two regions of northern Benin

Background The current study shows the results of three years of IRS entomological monitoring (2016, before intervention; 2017 and 2018, after intervention) performed in Alibori and Donga, northern Benin. Methods Mosquito collections were performed on a monthly basis using human landing catches and pyrethrum spray catches in six districts including four treated with Actellic 300 CS (Kandi, Gogounou, Djougou and Copargo) and two untreated (Bembèrèkè and Kouandé) which served as control sites. Key transmission indicators of Anopheles gambiae (s.l.) as well as the residual activity of Actellic 300 CS assessed through WHO cone tests, were determined. Results The residual efficacy duration of Actellic 300 CS after the two IRS campaigns (2017 and 2018) was 4–5 months (May–September). The parity rate and the sporozoite index of An. gambiae (s.l.) were 36.62% and 0.71%, respectively, after the first spray round in treated areas compared to 57.24% and 3.7%, respectively, in the control areas (P < 0.0001). The same trend was observed after the second spray round. After the first spray round, each person received 1.6 infective bites/month (ib/m) in the treated areas against 12.11 ib/m in the control areas, resulting in a reduction rate of 86.78%. Similarly, the entomological inoculation rate was 1.5 ib/m after the second spray round in the treated areas vs 9.75 ib/m in the control areas, corresponding to a reduction of 84.61%. A decrease in the parity rate (46.26%), sporozoite index (85.75%) and EIR (87.27%) was observed for An. gambiae (s.l.) after the first round of IRS (June–October 2017) compared to the pre-intervention period (June–October 2016). The density of An. gambiae (s.l.) ranged between 0.38–0.48 per house in treated areas vs 1.53–1.76 An. gambiae (s.l.) per house respectively after the first and second IRS rounds. Conclusions This study showed the positive impact of IRS in reducing key entomological parameters of malaria transmission in Alibori and Donga. However, the considerable blood-feeding rate of An. gambiae (s.l.) in spray areas, stress the need for the population to sleep under long-lasting insecticidal nets (LLINs) in addition, to prevent from mosquito bites which did not succeed in resting on sprayed walls.

Keanekaragaman dan perilaku menggigit nyamuk sebagai vektor potensial filariasis di Kabupaten Banyuasin, Sumatera Selatan

Filariasis adalah penyakit menular menahun disebabkan oleh cacing filaria dan ditularkan oleh berbagai spesies nyamuk seperti Mansonia, Anopheles, Culex, Aedes, dan Armigeres. Penelitian ini bertujuan mengetahui keanekaragaman dan perilaku menggigit nyamuk sebagai vektor potensial penularan filariasis di Kabupaten Banyuasin, Sumatera Selatan. Penangkapan nyamuk dilakukan selama 12 jam dari pukul 18.00–06.00 dengan metode human landing collection dan animal biting trap. Pada Desember 2016 hasil penelitian menunjukkan bahwa sampel nyamuk yang ditangkap di daerah studi berjumlah 16 spesies dengan spesies paling dominan yang ditemukan adalah Mansonia uniformis (47,28%), Culex tritaeniorhynchus (23,89%), dan Culex vishnui (14,48%). Ma. uniformis memiliki perilaku menggigit lebih banyak di luar rumah dengan rata-rata angka perilaku menggigit (man biting rate/MBR) sebesar 100,50 nyamuk/malam dan angka kepadatan gigitan nyamuk (man hour density/MHD) sebesar 11,90 dan merupakan yang tertinggi dari semua spesies nyamuk yang ditemukan. Analisis parity rate melalui pembedahan terhadap nyamuk dewasa mengkonfirmasi bahwa perkiraan umur populasi Ma. uniformis adalah 31,8 hari dan Ma. uniformis terdeteksi positif sebagai vektor penularan filariasis.

The Significance of ‘Non-Significant’ Meconium Stained Amniotic Fluid (MSAF): Colour versus Contents

The presence of ‘thin’ or ‘non-significant’ meconium stained amniotic fluid (MSAF) is currently being considered by some intrapartum guidelines as ‘low risk’, requiring only an intermittent auscultation and not continuous electronic fetal heart rate monitoring using the cardiotocograph (CTG). Clinicians not only must exclude ‘non-physiological’ causes of MSAF but consider the potential effect of MSAF on fetal wellbeing, irrespective of whether the passage was secondary to a normal physiological process or due to an underlying pathology. Management decisions should be made based on the parity, rate of progress of labour, cervical dilatation at diagnosis, and observed CTG changes and the risk factors such as multiple pregnancy and intra-uterine growth restriction. Presence of any meconium within the amniotic fluid should be considered as an important intrapartum risk factor. The thin meconium may be ‘non-significant’ on visual inspection, but it is very significant from the point of view of a fetus, who is covered with toxic materials within the surrounding amniotic fluid.