EFFECT OF COPPER SULPHATE PENTAHYDRATE ON MOSQUITO LARVAL AEDES AEGYPTI, CULEX QUINQUEFASCIATUS, AND ANOPHELES QUADRIMACULATUS IN LABORATORY AND UNDER SEMI-FIELD CONDITIONS

Mosquito larval control has been conducted by various chemicals and biological agents to reduce mosquito population and mosquito-borne diseases. The larvicidal efficacy of Copper sulphate pentahydrate (CuSO4 ·5H2 O) on Aedes aegypti, Culex quinquefasciatus and Anopheles quadrimaculatus was evaluated separately in the laboratory and semi-field conditions. Different concentrations of CuSO4 ·5H2 O (ranging from 1 to 20 ppm) were tested against third (3rd ) instar larvae. Larval mortality was observed at 24, 48 & 72h after exposure and the LC 50 values were determined. In both conditions, larval mortality showed concentration and time dependent correlations i.e. larval mortality was higher with increasing concentration CuSO4 ·5H2 O and exposure time. No mortality was observed in the control (0 ppm). Of the three species tested, Cx. quinquefasciatus and An. quadrimaculatus were more sensitive to CuSO4 ·5H2 O than Ae. aegypti. It was demonstrated that 1.5 -2.25 ppm of CuSO4 ·5H2 O killed more than 50% of Cx. quinquefasciatus and An. quadrimaculatus larvae at 72 h in both laboratory and semi-field conditions, whereas Ae. aegypti could survive easily in these concentrations. Besides, CuSO4 ·5H2 O showed more toxicity to larvae in semi-field conditions than laboratory studies. These results suggest that CuSO4 ·5H2 O could be used as a potential larvicide especially for Cx. quinquefasciatus and An. quadrimaculatus as a low-cost alternative larvicidal agent. Further studies will be needed to confirm its effectiveness in large scale field trials.

Spatial Repellents Protect Small Perimeters from Riceland Mosquitoes in a Warm-Humid Environment

ABSTRACT Recent experiments suggest spatial repellents may significantly reduce biting pressure from host-seeking riceland mosquitoes, such as Anopheles quadrimaculatus, in a warm-humid open-field habitat. However, little is known regarding efficacy of these formulations in partially enclosed spaces where US military personnel may be sheltered or concealed in an operational environment. In this study we investigated the capability of 3 spatial repellents—metofluthrin, linalool, and d-cis/trans allethrin—to reduce mosquito incursion into small open-top enclosures of US military camouflage netting. We found that metofluthrin was more effective in partially enclosed spaces compared with the open field, whereas both linalool and d-cis/trans allethrin provided superior protection in the open. These findings support strategic selection of spatial repellents depending on the environment immediately surrounding the host.

Combining DL-Methionine and Bacillus thuringiensis Subspecies israelensis: Prospects for a Mosquito Larvicide

Mosquito larvicides can reduce mosquito populations at the source, potentially decreasing biting rates and pathogen transmission. However, there is a growing need for mosquito larvicides that are environmentally sustainable. Bacillus thuringiensis subspecies israelensis (BTI) is a naturally occurring bacterium commonly used as a larvicide to manage mosquito populations. Methionine is an essential amino acid that has demonstrated toxic properties against larval mosquitoes in laboratory experiments, while having minimal effects on non-target organisms. The goal of this study was to evaluate the potential for a novel combination larvicide by testing for compatibility between these two active ingredients. We began by determining the lethal concentration values (LCs) of BTI and DL-methionine against Anopheles quadrimaculatus Say and Aedes aegypti Linnaeus (Diptera: Culicidae) larvae. These bioassays were conducted in glass jars and mortality was observed 48 h post-treatment. We found that while DL-methionine was more toxic to An. quadrimaculatus than Ae. aegypti, the opposite was true for BTI. Then, we used these LCs to conduct bioassays with a combination of BTI and DL-methionine to determine the relationship between the two active ingredients when used against An. quadrimaculatus and Ae. aegypti larvae. The findings of this study demonstrate that BTI and DL-methionine have the potential to be complementary due to their additive properties at higher concentrations and effect levels when tested against An. quadrimaculatus. However, an antagonistic relationship was detected at the concentrations tested with Ae. aegypti. These results are encouraging and imply that a DL-methionine or BTI/DL-methionine combination larvicide could be used in management of Anopheles species.

Transmission potential of Mayaro virus by Aedes albopictus, and Anopheles quadrimaculatus from the USA

Background Mayaro virus (MAYV; Alphavirus, Togaviridae) is an emerging pathogen endemic in South American countries. The increase in intercontinental travel and tourism-based forest excursions has resulted in an increase in MAYV spread, with imported cases observed in Europe and North America. Intriguingly, no local transmission of MAYV has been reported outside South America, despite the presence of potential vectors. Methods We assessed the vector competence of Aedes albopictus from New York and Anopheles quadrimaculatus for MAYV. Results The results show that Ae. albopictus from New York and An. quadrimaculatus are competent vectors for MAYV. However, Ae. albopictus was more susceptible to infection. Transmission rates increased with time for both species, with rates of 37.16 and 64.44% for Ae. albopictus, and of 25.15 and 48.44% for An. quadrimaculatus, respectively, at 7 and 14 days post-infection. Conclusions Our results suggest there is a risk of further MAYV spread throughout the Americas and autochthonous transmission in the USA. Preventive measures, such as mosquito surveillance of MAYV, will be essential for early detection.

No Evidence That Salt Water Ingestion Kills Adult Mosquitoes (Diptera: Culicidae)

Various products and insecticides are available that purport to reduce wild populations of adult mosquitoes. Recently, several manufacturers and general public comments on the internet have promoted devices that claim that ingestion of salt will significantly reduce populations of wild mosquitoes to near zero; there are no known scientific efficacy data that support these claims. We tested the survival of nine mosquito species of pest and public health importance across four adult diets: Water Only, Sugar Water Only (8.00%), Salt Water Only (1.03%), and Sugar + Salt Water. Species included the following: Aedes aegypti (L.), Aedes albopictus (Skuse), Aedes dorsalis (Meigen), Aedes notoscriptus (Skuse), Aedes vigilax (Skuse), Anopheles quadrimaculatus (Say), Culex pipiens (L.), Culex quinquefasciatus (Say), and Culex tarsalis (Coquillett). Male and female mosquitoes were placed in cages and allowed to feed on liquid diets under controlled environmental conditions for 1 wk. For seven of the nine species, adult survival was significantly higher in the presence (Sugar Water, Sugar + Salt Water) versus the absence (Water Only, Salt Only) of sugar, with no indication that salt had any effect on survival. Anopheles quadrimaculatus showed intermediate survival in Sugar + Salt to either Sugar Only or no sugar diets, whereas Aedes dorsalis showed low survival in Salt Only versus other diets. Based on our data and coupled with the fact that mosquitoes have physiological and behavioral adaptations that allow them to avoid or process excess salt (as found in blood meals), we conclude that there is no scientific foundation for salt-based control methods of mosquitoes.

Transmission potential of Mayaro virus by Aedes albopictus, and Anopheles quadrimaculatus from United States

Background Mayaro virus (MAYV; Alphavirus, Togaviridae) is an emerging pathogen endemic in South American countries. The increase in intercontinental travel and tourism-based forest excursions has resulted in an increase in MAYV spread, with imported cases observed in Europe and North America. Intriguingly, no local transmission of MAYV has been reported outside South America, despite the presence of potential vectors.Methods We assessed the vector competence of Aedes albopictus from New York and Anopheles quadrimaculatus for MAYV. Results We showed that Aedes albopictus from New York and Anopheles quadrimaculatus are competent vectors for MAYV. However, Aedes albopictus was more susceptible to infection. Transmission rates increased with time for both species with rates of 37.21% and 64.44% for Aedes albopictus, and 31.11% and 46.34% for Anopheles quadrimaculatus, respectively, at 7 and 14 days-post-infection. Conclusions Our results suggest there is a risk of further MAYV spread throughout the Americas and autochthonous transmission in the United States. Preventive measures such as mosquito surveillance of MAYV will be essential for early detection.

Impact of Three Species of Aquatic Plants on Anopheles quadrimaculatus and its Effect on the Efficacy of Boric Acid Sugar Baits

ABSTRACT The purpose of this study was to investigate the sugar-feeding behavior of Anopheles quadrimaculatus by measuring the impact of different aquatic plants on its survival. At the same time, the potential use of boric acid in toxic sugar bait (TSB) applications to the leaves of these plants was also evaluated. Mean survival rates of mosquitoes after 120 h feeding on 3 common aquatic plant species—Thalia geniculata, Pontederia cordata, and Limnobium spongia—were 10.55%, 1.86%, and 6.21%, respectively. No significant difference in mortality between mosquitoes feeding on separate plant species was detected (P = 0.05). The TSB efficacy was evaluated by leaf dip bioassay to compare 24-h mortality of mosquitoes feeding on leaves treated with TSB formulation (1% boric acid, 10% sucrose) and leaves dipped in 10% sucrose. Mortality was significantly higher for TSB-treated leaves for T. geniculata (t = 12.5, df = 8, P < 0.0001) and P. cordata (t = 5.42, df = 8, P = 0.0006) than for L. spongia (t = 1.4003, df = 8, P = 0.199). One-way ANOVA analysis showed no significant difference in efficacy between TSB-treated leaves of the 3 plants.

Vector competence of selected North AmericanAnophelesandCulexmosquitoes for Zika virus

Zika virus (ZIKV) is a vector-borne flavivirus that has caused recent outbreaks associated with serious disease in infants and newborns in the Americas.Aedesmosquitoes are the primary vectors for ZIKV, but little is known about the diversity of mosquitoes that can transmit ZIKV in North America. We chose three abundant North American mosquito species (Anopheles freeborni,Anopheles quadrimaculatus, andCulex tarsalis) and one known vector species (Aedes aegypti), fed them blood meals supplemented with a recent outbreak ZIKV strain, and tested bodies, legs, and saliva for infectious ZIKV. ZIKV was able to infect, disseminate, and be transmitted byAedes aegypti. However,Anopheles freeborni,Anopheles quadrimaculatus, andCulex tarsaliswere unable to be infected. We conclude that these species are unlikely to be involved in ZIKV transmission in North America. However, we should continue to examine the ability for other mosquito species to potentially act as ZIKV vectors in North America.