Studies of possible movement of Venezuelan encephalitis virus from an enzootic focus in Guatemala during 1971-1974.

Objective:

This study sought to understand the movement and survival pattern of the Venezuelan Encephalitis (VE) virus in sentinel horses, mosquitoes, and a hamster situated various distances from a known reservoir area in Guatemala, specifically focusing on the effects of seasonality.

Explanation:

The researchers looked into instances of VE virus infections during the wet seasons of 1971, 1972, and 1973, as well as the dry seasons of 1973 and 1974. The following observations made were:

• Sentinel horses, specially kept animals for disease surveillance, located inland away from an enzootic marsh suspected to be a virus hotspot, demonstrated temporal and geographic progression of VE infections. This was particularly noticeable during the wet seasons of 1972 and possibly 1971.
• During the wet seasons of 1972 and 1973, the VE virus was also detected in sentinel horses and a sentinel hamster located within a small woodland area, situated 10 kilometers north of the marshland.
• Interestingly, no detectable levels of the virus were recorded in the same woodland area during the dry seasons of 1973 and 1974 or the wet season of 1974.
• In addition to this, Culex (Melanoconion) mosquitoes, a known carrier of the VE virus, were discovered in the woodland area and the marshland during August 1973.

These findings suggest that there might be a seasonal and environmental component associated with the movement of the VE virus from the marshlands.

However, the occurrence of the virus in areas adjacent to the marsh was unpredictably variable on a year-to-year basis during the period of 1971-1974. It was also observed that the presence of the virus was extremely focal or limited to specific habitats.

The mechanisms by which the VE virus is able to move from the marshlands to other areas are not yet understood, but the researchers are investigating the possible role of bats in this phenomenon.