methoprene and West-Nile-Fever

Topics: Animals; Bird Diseases; Birds; Culicidae; Environmental Exposure; Environmental Health; Health Education; Humans; Insect Vectors; Insecticides; Life Cycle Stages; Malathion; Methoprene; Mosquito Control; Ontario; Population Surveillance; Protective Clothing; Risk Assessment; West Nile Fever

West Nile virus remains the leading cause of arboviral neuroinvasive disease in the United States, despite extensive efforts to control the mosquito vectors involved in transmission. In this study, we evaluated the effectiveness of Altosid SR-20 (active ingredient, S-methoprene 20%) larvicide applications using truck-mounted ultra-low volume (ULV) dispersal equipment to target Culex pipiens Linnaeus (Diptera: Culicidae) and Cx. restuans (Theobald)larvae. A combination of emergence bioassays, open-field measurements of deposited S-methoprene and spray distribution using gas chromatography-mass spectrometry, and assessments of adult Culex spp. populations in response to applications were conducted over the summer of 2020 within the North Shore Mosquito Abatement District (IL, USA). Open-field applications revealed that dispersed Altosid SR-20 using ULV equipment was effective (75% emergence inhibition in susceptible lab strain Cx. pipiens larvae) up to 53 m. In suburban neighborhood applications, we found that S-methoprene deposition and larval emergence inhibition (EI) in front yards did not differ significantly from backyards. An overall EI of 46% and 28% were observed for laboratory strain Cx. pipiens and wild Cx. restuans larvae respectively, and both had an EI significantly higher than the untreated control group. The EI of exposed wild Cx. pipiens larvae did not differ from the untreated controls, suggesting an increased tolerance to S-methoprene. No difference in abundance of gravid or host-seeking adult Culex spp. post-application was detected between treated and untreated sites. These results document the ability of area-wide application to distribute S-methoprene, but this strategy will need further modifications and evaluation for Culex spp. management.

Topics: Animals; Chicago; Culex; Larva; Methoprene; Mosquito Vectors; Seasons; West Nile Fever; West Nile virus

Since the outbreak of vector-borne West Nile virus in New York City in 1999, the disease has spread across United States and Canada, resulting in the use of larvicides such as methoprene at catch basins for widespread urban mosquito control. Although the manufacturer has recommended a methoprene dosage for catch basin application, the effect of rainfall on this dosage is not known. A field study on the fate of methoprene pellets and ingots was conducted during the summer of 2004 at three catch basins in the City of Toronto, Canada. Water samples from each catch basin were collected daily and during rain storms and analyzed for methoprene concentration using gas chromatography mass spectrometry. It was found that: (1) the methoprene concentration at the catch basin sump fell below the minimum lethal concentration most of the time; (2) rainfall events greater than 25 mm flushed methoprene pellets out of the catch basin; (3) the higher the sump water depth, the higher the residual methoprene concentration at the catch basin sump; and (4) rainfall flushed methoprene from the catch basins into the storm sewer outfall at concentrations much lower than the detrimental level which might cause ecosystem damage.

Topics: Environmental Monitoring; Humans; Insecticides; Methoprene; Ontario; Water Microbiology; West Nile Fever; West Nile virus

Effective control of mosquitoes in rural Midwestern communities that lack organized mosquito control districts would be aided by baseline data on optimal breeding sites, interannual effects of climate on population emergence and abundance, and efficacy of various control options under field conditions. During 19 surveillance weeks in the summer of 2005, we sampled 100 catch basins each week that were distributed among 10 study zones. Catch basins within each study zone were subjected to 1 of 4 different mosquito control methods or were left untreated. Of the 10 study zones, 5 were in high-intensity urban areas and 5 in low-intensity urban areas. During the study period, treatment of urban catch basins with Altosid XR extended residual briquets resulted in a 69.5% reduction in mosquito larvae numbers. However, the product did not provide sustained treatment for the 120-150 days suggested by the manufacturer. Vectolex WSP, when applied according to manufacturer's suggestions, resulted in a 73.4% reduction in mosquito larvae. VectolexWSP effectiveness was impacted by heavy rainfalls early in the surveillance period. Cleaning catch basins once or twice during the surveillance period resulted in a 40.1% and a 39.9% reduction in mosquito larvae, respectively. Catch basins in high-intensity urban areas comprised 27.7% of the total collection compared to 72.3% from low-intensity urban areas. The AltosidXR extended residual briquets and the VectolexWSP products both impacted the number of mosquito larvae collected. However, a single treatment to control mosquitoes in this study area may not be sufficient. We suggest that treatment of urban catch basins is optimized when accompanied by a comprehensive surveillance plan, and that a combination of treatments or multiple treatments during the season may be necessary to mitigate risks of vector-borne infectious diseases in areas with similar climate and precipitation trends.

Topics: Animals; Bacillus; Culex; Insect Vectors; Insecticides; Larva; Methoprene; Mosquito Control; Pest Control, Biological; Rain; Time Factors; Urban Population; Waste Disposal, Fluid; West Nile Fever; Wisconsin

Topics: Canada; Communicable Disease Control; Communicable Diseases, Emerging; Health Education; Humans; Insecticides; Methoprene; Mosquito Control; National Health Programs; New York City; Seasons; West Nile Fever