Utilizing citizen science to model the distribution of Aedes aegypti in West Africa

In a rapidly urbanizing region such as West Africa, Aedes mosquitoes pose an emerging threat of infectious disease that is compounded by limited vector surveillance. Citizen science has been proposed as a way to fill surveillance gaps by training local residents to collect and share information on disease vectors. Increasing citizen science efforts can begin to bridge the gaps in our current knowledge of Aedes distribution while engaging locals with mosquito control and public health efforts. Understanding the distribution of disease vectors in West Africa can inform researchers and public health officials on where to conduct disease surveillance and focus public health interventions. We aimed to compare citizen science data to published literature observations of Aedes mosquitoes and to quantify how incorporating citizen science changes our understanding of Aedes mosquito distribution in West Africa. We utilized citizen science data collected through NASAs GLOBE Observer mobile phone application and data from a previously published literature review on Aedes mosquito distribution to examine the contribution of citizen science to understanding the distribution of Ae. aegypti in West Africa using Maximum Entropy modeling. Combining citizen science and literature-derived observations improved the fit of the model compared to models created by each data source alone, but did not alleviate location bias within the models, likely due to lack of widespread observations. Understanding Ae. aegypti distribution will require greater investment in Aedes mosquito surveillance in the region, and citizen science should be utilized as a tool in this mission to increase the reach of surveillance.

Control effectiveness of APL formulation against dengue- and Zika-transmitting Aedes mosquitoes in Gia Lai province, Vietnam

Background: Dengue fever and Zika are two of the Aedes-borne diseases. Despite being widely used, synthetic mosquitocides become abortive for the mosquito control due to growing resistance and environmental pollution. In Gia Lai province (dengue-endemic area), a huge amount of cashew nut shell waste with roughly 100,000 tons/year has been disposed of into the environment, potentiating a high risk of pollution. Methodology/Principal findings: To utilize it, anacardic acid was extracted and combined it with ethanol extract of the local lime peel, which contains limonene, to generate APL formulation. APL robustly exhibited inhibition of egg hatching, larvicidal effect, and repellent effect against female mosquitoes from oviposition sites in the laboratory and field. The results showed that, at a dose of 12.5 ppm, the APL formulation after 24 hours of treatment demonstrated oviposition deterrence against Ae. aegypti (43.6%) and Ae. albopictus (59.6%); inhibited egg hatching of Ae. aegypti (49.6%) and Ae. albopictus (59.6%); caused larval lethality in Ae. aegypti (LC 50 = 9.5 ppm, LC 90 = 21 ppm) and Ae. albopictus (LC 50 = 7.6 ppm, LC 90 = 18 ppm). Under natural field conditions, it showed a 100% reduction in larval density after 48 and 72 hours of the APL treatment at a tested concentration of 120 mg a.i./m 2 and maintained a mortality rate of 100% in the next 14 days. Conclusions/Significance: The APL formulation is promisingly to become an environmentally friendly and highly effective biological product for future management programs of dengue and Zika-transmitting vectors. Here offer prospects in controlling critical illnesses transmitted by several mosquito species in dengue-endemic areas.

Attraction of the Mosquitoes Aedes aegypti and Aedes albopictus (Diptera: Culicidae) to a 3-Part Phytochemical Blend in a Mesocosm

Aedes aegypti (L.) and Aedes albopictus (Skuse) mosquitoes of both sexes were attracted to a 3-part volatile synthetic phytochemical blend but differed according to their component ratios, 7:3:2 or 1:1:1, and their initial concentrations. These arbovirus vectors were presented with the blends as baits in paired baited and blank CFG traps in a large greenhouse mesocosm. Ae. aegypti attraction was highest at a 7:3:2 blend ratio, but at a concentration half that found most effective for an anopheline mosquito species in outdoor screenhouses. Both lower and higher concentrations yielded substantially lower attraction scores for Ae. aegypti. By contrast, the few tests conducted on Ae. albopictus showed that it was not as sensitive to concentration, but again it was more responsive to the 7:3:2 ratio of components than to the 1:1:1 ratio. The two sexes of both species were represented equally in the trap catches, indicating the potential value of this and similar attractive blends for population surveillance and control of Aedes mosquitoes.

The Distribution and Composition of Vector Abundance in Hanoi City, Vietnam: Association with Livestock Keeping and Flavivirus Detection

Background: Dengue virus and Japanese encephalitis virus are two common flaviviruses that are spread widely by Aedes and Culex mosquitoes. Livestock keeping is vital for cities; however, it can pose the risk of increasing the mosquito population. Our study explored how livestock keeping in and around a large city is associated with the presence of mosquitoes and the risk of them spreading flaviviruses. Methods: An entomological study was conducted in 6 districts with 233 households with livestock, and 280 households without livestock, in Hanoi city. BG-Sentinel traps and CDC light traps were used to collect mosquitoes close to animal farms and human habitats. Adult mosquitoes were counted, identified to species level, and grouped into 385 pools, which were screened for flaviviruses using a pan-flavivirus qPCR protocol and sequencing. Results: A total of 12,861 adult mosquitoes were collected at the 513 households, with 5 different genera collected, of which the Culex genus was the most abundant. Our study found that there was a positive association between livestock keeping and the size of the mosquito population—most predominantly between pig rearing and Culex species (p < 0.001). One pool of Cx. tritaeniorhynchus, collected in a peri-urban district, was found to be positive for Japanese encephalitis virus. Conclusions: The risk of flavivirus transmission in urban areas of Hanoi city due to the spread of Culex and Aedes mosquitoes could be facilitated by livestock keeping.

The Residual Efficacy of SumiShield™ 50WG and K-Othrine® WG250 IRS Formulations Applied to Different Building Materials Against Anopheles and Aedes Mosquitoes

Insecticides with novel modes of action are required to complement the pyrethroids currently relied upon for controlling malaria vectors. One example of this is the neonicotinoid clothianidin, which is found in SumiShield&trade; 50WG used in indoor residual spraying (IRS). In a preliminary experiment, mortality in insecticide susceptible and resistant An. gambiae adults exposed to SumiShield&trade; 50WG-treated filter papers reached 80% by 3-days post-exposure and 100% by 6-days post-exposure. Next, cement, wood, and mud tiles were treated with SumiShield&trade; 50WG or K-Othrine&reg; WG250 (deltamethrin IRS formulation) and insecticide resistant and susceptible Anopheles and Aedes were exposed to these surfaces periodically for up to 18-months. Pyrethroid resistant Cx. quinquefasciatus were also exposed at 9 months. Between exposures tiles were stored in heat and relative humidity conditions reflecting those found in the field. On these surfaces, SumiShield&trade; 50WG was effective at killing both susceptible and resistant An. gambiae for 18 months post-treatment, while mortality amongst the resistant strains when exposed to deltamethrin (K-Othrine&reg; WG250) IRS was not above that of the negative control. Greater efficacy of SumiShield&trade; 50WG was also demonstrated against insecticide resistant strains of An. funestus compared to deltamethrin, though the potency was lower when compared with An. gambiae. In general, a higher efficacy of SumiShield&trade; 50WG was observed on cement and mud compared to wood. SumiShield&trade; 50WG demonstrated poor residual activity against Aedes aegypti and Culex quinquefasciatus. Overall, the results suggest SumiShield&trade; 50WG is well suited for malaria control.

Effect of Petroleum Products on the Larvicidal Activity of Aedes Mosquitoes in Ika North-East LGA, Delta State, Nigeria

Aims: The recent yellow fever outbreak in Delta State, especially in Ika North East local government, triggered the need for this study. Background: Diseases caused by Aedes are by far raising serious concerns in the world. Objective: To evaluate the larvicidal activity on the use of petroleum products in the control of Aedes mosquitoes. Methods: Mosquito species were collected using 350ml deep ladle and identified in the field using their resting positions in their local habitats. Larvae and pupae were separately exposed to 0.005, 0.01, and 0.02%ml of kerosene and petrol in single and mixed forms. The experimental sets were triplicated. Data was analyzed using ANOVA and Turkey’s test to compare mortality, and time of mortality. LC50 and LC95 were computed using Probit analysis. Results: Results revealed that all concentrations of treatment caused complete mortality in larvae except in 0.005%ml and 0.01%ml of kerosene alone and kerosene and petrol mixture at 50 minutes of exposure. All concentrations of treatment equally caused complete mortality in pupae except in 0.005%ml of kerosene (Mean= 10.00) at 30 minutes. The differences between mortality and time mortality records were significant (p< 0.05). Kerosene and petrol mixture and kerosene alone had the lower LC50 and LC95 0.0021 and 0.0088ml respectively in the larvae group. Kerosene and petrol mixture had lower LC50 and LC95 0.0037 and 0.0050, respectively. Conclusion: Therefore, scaling up this intervention on a large scale in endemic areas would reduce larvae density and disease outbreaks.

Local and Global Stability Analysis of Dengue Disease with Vaccination and Optimal Control

Dengue fever is a disease that has spread all over the world, including Thailand. Dengue is caused by a virus and there are four distinct serotypes of the virus that cause dengue DENV-1, DENV-2, DENV-3, and DENV-4. The dengue viruses are transmitted by two species of the Aedes mosquitoes, the Aedes aegypti, and the Aedes albopictus. Currently, the dengue vaccine used in Thailand is chimeric yellow tetravalent dengue (CYD-TDV). This research presents optimal control which studies the vaccination only in individuals with a documented past dengue infection (seropositive), regardless of the serotypes of infection causing the initial infection by the disease. The analysis of dengue transmission model is used to establish the local asymptotically stabilities. The property of symmetry in the Lyapunov function an import role in achieving this global asymptotically stabilities. The optimal control systems are shown in numerical solutions and conclusions. The result shows that the control resulted in a significant reduction in the number of infected humans and infected vectors.

Zika Virus: An Emerging Mosquito-Borne Disease Threat in Kerala

First laboratory confirmed Zika case in Kerala was reported in Thiruvananthapuram, on 8th July 2021. Since then, 68 ZIKV positive cases have been reported from Kerala, with majority of cases from Thiruvananthapuram Corporation area. Based on the preliminary investigation, micro containment zones were identified and detailed investigation was carried out in these areas. Entomological surveillance indicated that all the three species of Aedes mosquitoes - Ae. aegypti, Ae. albopictus and Ae. vittatus were present in the survey areas. The Aedes larval indices were found above the critical level. The most preferred habitats of Aedes mosquitoes were water stagnated areas in cemented floor of the newly constructing buildings followed by cement tanks/cement pits and discarded tires. ZIKV could be detected from all the three Aedes mosquitoes collected from the micro containment zones. Trasovarial transmission of ZIKV could be noted in this outbreak. Vector control was intensified with the active participation of local bodies and local health institutions. The epidemiological study showed most of the Zika positive cases has fever, rash and conjunctivitis and in majority of cases, the duration of the illness lasts only for 2-3 days. The females were more affected. The most affected age group was 21-30 followed by 31-40. Among the 68 ZIKV positive cases, 7 (10.29%) were pregnant women. No major anomaly was detected in ZIKV positive cases; however there is a need to scale up surveillance and vector control activities to prevent further outbreaks in Kerala and elsewhere.