Assessment of the Mechanical Transmission Potential of Coxsackievirus RNA by Female Culex molestus Mosquitoes under Controlled Laboratory Conditions

Introduction: Coxsackieviruses are medically important enteroviruses transmitted mainly by the fecal–oral route. Although mosquitoes are studied as biological vectors of arboviruses, their role in the mechanical transmission of enteroviruses remains unclear. The aim of this study was to evaluate the susceptibility of female Culex molestus mosquitoes to mechanical transmission of Coxsackievirus genetic material, and the effect of exposure duration on the amount of viral RNA transferred. Methods: Fifty blood and stool samples were collected from participants. IgM was screened by rapid immunoassay and stool viral RNA by RT-qPCR; positive samples served as viral sources. Female C. molestus were exposed to positive fecal sources for 1, 4, or 24 hours, then transferred to negative fecal media for 8 hours; recipient-media RNA was quantified by RT-qPCR. Results: All 50 samples were IgM-positive; RT-qPCR confirmed Coxsackievirus RNA in 22/50 (44.0%), with Ct 19.2–37.6 (mean 28.75 ± 5.31). Transfer was detected after all three periods, with mean Ct decreasing from 36.92 to 33.61 to 29.84 and molecular recovery rising from 0.09% to 0.82% to 10.8% at 1, 4, and 24 hours. ANOVA showed highly significant differences (F = 96.3, P < 0.001), with a strong inverse correlation between exposure duration and Ct (r = −0.934, R² = 0.872, P < 0.001). Controls showed no amplification. Conclusion: Female C. molestus can mechanically transfer Coxsackievirus RNA from a positive fecal source to a negative medium under laboratory conditions, with transfer increasing with exposure time. RT-qPCR confirms RNA transfer but not infectivity; further studies of viability and field relevance are warranted.