Selection of a strain of Culex tarsalis highly resistant to infection following ingestion of western equine encephalomyelitis virus.

The research has successfully evolved two hybrid strains of Culex tarsalis that show high resistance to infection from the western equine encephalomyelitis virus, after being fed to viremic chicks. The resistance in these strains occurs due to a barrier in the mesenteron.

Research Methodology and Findings

• The researchers undertook a prolonged selection process to evolve two hybrid strains of Culex tarsalis (a species of mosquitoes) that were resistant to the western equine encephalomyelitis virus.
• Post evolution, these strains were found to be more than 25,000 times resistant than the most susceptible parental strain when fed on viremic chicks.
• The research revealed that the resistance was associated with a barrier in the mesenteron, a part of the insect’s digestive system.

Mode of Infection

• Interestingly, both refractory (resistant) and parental strains demonstrated equal susceptibility to infection via intrathoracic inoculation, a method where the virus is directly introduced into the thorax of the mosquitoes.

Inheritance and Dominance Pattern

• The research revealed an intriguing pattern, where susceptibility was dominant, and possibly incompletely dominant over resistance.
• Research suggested that the inheritance pattern was probably polyfactorial – where multiple factors or genes could be influencing the trait.

Alternative Infection Mechanisms

• Researchers perceived that a small proportion of individuals were infected through non-genetic mechanisms, indicating that non-heritable factors may have been influencing the outcomes.