Intestinal threshold of an enzootic strain of Venezuelan encephalitis virus in Culex (Melanoconion) taeniopus mosquitoes and its implications to vector competency and vertebrate amplifying hosts.

This research investigated the susceptibility of Culex (Melanoconion) taeniopus mosquitoes from Guatemala to an enzootic strain of Venezuelan Encephalitis (VE) virus, discovering that these mosquitoes can contract the virus from vertebrates with remarkably low levels of the virus in their blood.

Study Design and Procedures

• The researchers tested the minimal intestinal dose of the VE virus that Culex (Melanoconion) taeniopus mosquitoes can ingest. These mosquitoes were collected from areas known to be a habitat for the VE virus in Guatemala.
• The scientists used plaque forming units (pfu) to measure the virus concentration. This is a commonly used method for measuring the concentration of a virus.
• An enzootic strain of the VE virus was utilized in this study. Enzootic refers to a disease that is constantly present in an animal population, but only occurs in a small number of cases.

Key Outcomes and Conclusions

• The study found that an intake of less than five pfu of the virus could lead to successful infection of the mosquitoes. Therefore, the researchers concluded that these mosquitoes have a low intestinal threshold for this enzootic strain of the VE virus.
• The research also explored the concept of vector competency, basically the mosquito’s ability to acquire, sustain, and transmit the virus. The fact that the mosquitoes were able to acquire the virus from such a small dose suggests that they are highly competent vectors.
• This study also revealed that these mosquitoes could acquire the virus from vertebrates – such as hamsters in this study – that had viremia levels (or levels of the virus in the blood) as low as 1,000-5,000 pfu/ml.
• However, the study acknowledges that other factors may limit the virus interchange between mosquitoes and vertebrates. This could include things like the mosquito’s feeding behavior or environmental conditions.

Implications of the Research

• This data aids our understanding of the transmission of the VE virus in natural environments. Given that the mosquitoes can acquire the virus from low levels of viremia in vertebrates, this could have implications for disease spread and control strategies.
• The findings also help identify vertebrates as potential “amplifying hosts”, meaning that they increase the amount of virus available to mosquitoes, consequently facilitating its spread.