Horses serve as good sentinels for WNV infection surveillance because they are easily identifiable; their role in the epidemiological cycle of WNV; being dead-end hosts
like humans; low cost easy to maintain facility to capture and sample horses: and the availability of serological tools are to do surveillance.
Such dead-end hosts
include people and adult chickens.
"We call horses dead-end hosts
because they cannot pass this virus to other horses, humans, or mosquitoes," said Dr.
WNF is a virus spread mainly by mosquitoes and birds, with humans and horses as the dead-end hosts
. After incubation period of between five and 15 days, the symptoms are usually a mild flu-like illness.
Alphaviruses are arthropod-borne viruses (arboviruses) that circulate among a wide variety of wild animals in relative mosquito vector-specific and host-specific enzootic cycles; infection in humans (dead-end hosts
) is almost exclusively incidental.
Camels can act as reservoir hosts for RVFV (6) but are unlikely to do so for WNV, which cycles between mosquitoes and wild birds with mammals usually being dead-end hosts
. High prevalence of antibodies to RVFV in camels has been described in different sub-Saharan and Sahelian countries (7-9).
The enzootic virus cycle involves transmission between avian hosts and ornithophilic mosquitoes, whereas humans and horses are considered dead-end hosts
. Given the recent increase of WNV infection in humans and horses in Europe, concern has been raised regarding public and animal health.
Active transmission of WNV in Puerto Rico indicated that this virus has established a life cycle of natural, amplifying hosts and arthropod vectors with horses and humans as dead-end hosts
. Sequence analysis of 4 isolates indicates that PR_WNV was derived from a recent introduction of lineage I WNV and is closely related to WNV currently circulating in North America based on the location of the isolates in the phylogenetic tree.