Larval exposure to insecticides increases adult susceptibility to bluetongue virus in Culicoides sonorensis Wirth and Jones (Diptera: Ceratopogonidae)
Year: 2026
Type: article
Abstract: Culicoides biting midges develop in organically enriched habitats, such as livestock wastewater, which can accumulate pesticide residues from livestock treatments. In some instances, larval development sites are directly targeted with insecticides for vector control. These environmental stressors can affect larval survival and gene expression patterns that govern development and long-term fitness, such as altered immune function. This overlap in gene pathways reflects the integration of detoxification in immunity as a response to both chemical stress and pathogenic threats. As a result, detoxifying pesticides at sublethal levels may developmentally compromise insect vectors, making them more vulnerable to infections in later life stages. In this study, larvae of Culicoides sonorensis Wirth and Jones, a major North American bluetongue virus (BTV) vector, were exposed to the lethal concentration for 10% of the test population (LC₁₀) of three distinct classes of insecticides (permethrin, yeast microencapsulated (YME) fluralaner, or methoprene) while controls received equal amounts of solvent (ethanol or water). Survivors were reared to adulthood and offered defibrinated sheep blood spiked with BTV at three days post-emergence. Engorged females were held for up to 14 days post-infection. At 1, 3, 7, 10, and 14 days post-infection, up to 10 females per treatment group were sampled to test for BTV infection and dissemination using RT-qPCR. Infection and dissemination rates, as well as viral titers as quantified by qPCR, were compared across time points and treatments to evaluate whether sublethal pesticide exposure of larvae alters vector competence of adults for BTV. Exposure to three different pesticides resulted in significantly increased BTV titers, particularly at 7 days post-infection (YME fluralaner and methoprene) and 14 days post-infection (permethrin). Infection and dissemination rates at 7 days post-infection were also significantly higher in midges exposed to YME fluralaner and methoprene. Midges exposed to permethrin had significantly higher dissemination rates at 14 days post-infection. Implications of changes in infection dynamics are discussed.
Source: Ecotoxicology
Language: English
Topic: Vector-Borne Animal Diseases
Subfield: Virology
Field: Immunology and Microbiology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,990
OpenAlex ID: W7225735954