West Nile Virus Antibody Prevalence in Horses During the 2023 Outbreak in Tunisia, North Africa.

The research article investigated the prevalence of West Nile virus in horses during an outbreak in Tunisia, North Africa, during 2023, using antibody testing.

Research Overview

Researchers analyzed twenty horses kept at the Pasteur Institute of Tunis, which are used for the production of a therapeutic serum for scorpion venom treatment. These twenty horses underwent testing during the West Nile virus outbreak of 2023, which affected humans and horses in Tunisia.

Methodology

• The horses’ blood samples were tested through an enzyme-linked immuno-sorbent assay (ELISA), a common lab technique used to detect and measure antibodies in blood. This test can help diagnose infections, including those caused by viruses like West Nile.
• Out of the twenty samples tested in November 2023, five were positive, resulting in a seroprevalence (the level of a pathogen in a population, as measured in blood serum) of 25%.
• To confirm the ELISA test results due to the relatively modest number of horses, the samples were also tested using a Virus microneutralization test (MNT). This involved using a Tunisian strain of West Nile virus lineage 1, which was first isolated in 2014.

Findings

• The MNT identified only two horses with WNV-neutralizing antibodies, leading to a lower seroprevalence of 10%.
• Of the five horses that tested positive by ELISA, only two were confirmed positive using the MNT.
• No new cases or seroconversions (a change from infection-free to infected) were identified in the horses when followed up in December 2023 and January 2024.
• No clinical cases linked to the horses were reported during this period. Blood analyses did not detect viral RNA (the genetic material of the virus), but the MNT results confirmed the virus’s circulation during the outbreak.

Implications

The researchers concluded that horses could play a crucial role in the early detection and accurate monitoring of West Nile virus outbreaks. This consideration is supported by the fact that humans and horses share similar clinical symptoms and antibody responses when infected with this virus. Therefore, ongoing surveillance of equid populations could offer a useful warning system for impending human outbreaks.