Use of sentinel serosurveillance of mules and donkeys in the monitoring of West Nile virus infection.

This study used mules and donkeys as markers to monitor and assess the prevalence of the West Nile Virus (WNV) in southern Spain after it was found in the horse and human population in the region.

Research Objectives and Methodology

• The research was conducted as a cross-sectional study on mules and donkeys that displayed no clinical signs of WNV infection in southern Spain. This method allows researchers to observe and analyze multiple variables at a specific point in time.
• The researchers aimed to assess and determine the seroprevalence of WNV in these animals. ‘Seroprevalence’ refers to the level of a pathogen in a population, as measured in blood serum.
• Blood samples were taken from the animals and tested for the presence of antibodies against WNV using a blocking ELISA and micro-virus neutralisation test. These are standard tests for detecting specific antibodies in a specimen.

Results and Findings

• The study found that 12 out of 165 (7.3%) animals sampled had antibodies against WNV. This indicates past exposure to WNV, although no clinical signs of the disease were observed.
• Of these, a higher seroprevalence was observed in mules (9.6%) than in donkeys (4.9%), although the difference wasn’t statistically significant, meaning it could have occurred by chance.
• About 10% of the herds tested also contained at least one seropositive animal.
• Interestingly, the researchers found antibodies against WNV in one of four donkeys tested on three different farms where WNV cases had previously been confirmed in horses. This could suggest cross transmission between horses and donkeys.
• Despite considering 26 potential explanatory variables, the researchers were not able to identify any particular risk factors for seropositivity, suggesting more research is needed in this area.

Conclusions and Implications

• The researchers concluded that using mules and donkeys as ‘sentinels’ or indicators for monitoring WNV could be an effective tool, especially in regions where horses are vaccinated against WNV; thus, the prevalence in horses might not accurately reflect the current state of the virus in the region.

This research contributes to our understanding of the epidemiology of WNV, which is significant given that this virus can cause serious and sometimes fatal disease in humans. It also suggests a novel approach to disease surveillance that may be effective in areas where prevalent species are routinely vaccinated.