Eilat virus isolated from Culex univittatus mosquitoes from the Namibian Zambezi Region influences in vitro superinfection with alpha- and flaviviruses in a virus-species-dependent manner.
Authors: Guggemos Heiko D, Kopp Anne, Voigt Katrin, Fendt Matthias, Graff Selina L, Mfune John K E, Borgemeister Christian, Junglen Sandra
Journal: PloS one
Summary
# Editorial Summary: Eilat Virus and Arbovirirus Co-circulation in Namibian Mosquitoes Insect-specific alphaviruses such as Eilat virus (EILV) circulate naturally in mosquito populations but remain poorly characterised, despite their potential to modulate transmission of pathogenic alphaviruses like Chikungunya and equine encephalitis viruses. Guggemos and colleagues isolated EILV from *Culex univittatus* mosquitoes in the Namibian Zambezi Region, performed complete genome sequencing, and conducted in vitro superinfection experiments using both vertebrate and mosquito cell cultures to investigate interactions between EILV and clinically significant viruses. The isolated strain showed 94.5% nucleotide identity to an Israeli EILV isolate and demonstrated strict host restriction to insects (no replication in vertebrate cells or at 34°C). Critically, EILV's effect on co-infecting viruses proved pathogen-dependent: it suppressed Sindbis virus production by 2000-fold and reduced Chikungunya virus by approximately 30-fold, but unexpectedly enhanced West Nile virus replication by over 5-fold. These findings suggest that EILV prevalence in wild mosquito populations may significantly alter the epidemiological landscape of arboviral transmission in southern Africa, potentially reducing risk of some endemic alphaviruses whilst paradoxically increasing West Nile virus circulation—an important consideration for disease surveillance programmes and vector control strategies in regions where these viruses co-circulate.
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Practical Takeaways
- •Insect-specific alphaviruses like EILV may naturally modulate transmission of pathogenic arboviruses (including equine encephalitis viruses and Chikungunya) through mosquito populations, with effects varying by virus species
- •The presence of EILV in Namibian mosquitoes suggests a potential biological factor that could influence arbovirus epidemiology in that region, relevant for disease surveillance in horses and other animals
- •Viral interference mechanisms demonstrated in vitro warrant investigation in natural mosquito populations to understand how insect-specific viruses may reduce or enhance transmission of clinically important arboviruses to equine hosts
Key Findings
- •Eilat virus (EILV) isolated from Culex univittatus mosquitoes in Namibia shows 94.5% nucleotide identity to Israeli EILV isolate and is restricted to insect hosts
- •EILV superinfection reduced Sindbis virus infectious particle production by 2000-fold, while reducing Chikungunya virus by approximately 30-fold in a multiplicity-of-infection-dependent manner
- •EILV demonstrated virus-species-dependent effects: 3-10-fold reduction for Bagaza and Middleburg viruses, but enhanced West Nile virus production by >5-fold at MOI 0.1
- •EILV replication is completely blocked at 34°C and unable to infect vertebrate cell lines, confirming its insect-specific nature