The utility of animal surveillance in the detection of West Nile virus activity in Puerto Rico, 2007.

The research investigated the usefulness of animal surveillance for early detection of West Nile virus (WNV) activity in Puerto Rico from 2006 to 2008, finding that it served as an effective early warning system before human cases were identified. The study emphasized the advantage of using horses as sentinel animals in the region.

Research Methodology

This study conducted an analysis of animal surveillance involving various species – horses, monkeys, sheep, dogs, and birds. Animal samples were collected over a span of three years (2006 to 2008), after the initial isolation of West Nile virus (WNV) from humans, mosquitoes, and chickens in 2007.

• The surveillance involved tracking WNV transmission amongst these animal species after its isolation from humans, mosquitoes, and chickens.
• The collected samples were tested for WNV presence using a method known as the blocking ELISA (Enzyme-Linked Immunosorbent Assay), a test that identifies antibodies in blood samples.

Research Findings

• The study found that 13.4% of all collected animal samples over this period were seropositive for WNV as per the blocking ELISA analysis. ‘Seropositive’ refers to the presence of specific antibodies to a microorganism in the blood, indicating exposure to that microorganism, in this case, WNV.
• Horses provided the most island-wide sampling, out of which, 22% were seropositive, indicating a significant exposure to WNV amongst the horse population.
• Furthermore, out of this 22%, 96% of the cases were confirmed as WNV infections by a procedure known as plaque-reduction neutralization test, a highly specific test considered as the “gold standard” for confirming cases of viral infection and immunity.

Conclusions

• The study concluded that animal surveillance plays a crucial role as an early indication of WNV activity even before the identification of human cases. This suggests that monitoring animal populations, particularly those like horses that can serve as a sentinel species, can provide an early warning system for impending infectious disease outbreaks like WNV and catalyze appropriate public health responses.
• The results also suggested that among the various animals tested, horses provided comprehensive geographical coverage and should continue to be used as sentinels for passive surveillance, particularly in tropical regions like Puerto Rico.
• Applying the conclusions of this research could guide surveillance strategies and add another layer of protection against infectious disease outbreaks for humans in such areas.