SEROMOLECULAR DETECTION, SEQUENCE ANALYSIS AND NEURO-IMMUNOLOCALIZATION OF WEST NILE VIRUS IN NIGERIAN WILDLIFE

Background: West Nile virus (WNV) is an emerging and re-emerging flavivirus transmitted by mosquitoes, causing diseases in the brain and other organs of the body in man and animals. Despite the increases in incidence, severity and geographic range of diseases caused by the virus especially in other parts of the world, there is limited data on the presence of the virus in the blood and brains of its wildlife hosts in Nigeria.
Methods: 758 animals from 9 animal types including pigeons, pied crows, cattle egrets, African giant rats, hedgehogs, pangolins, primates, bats, and squirrels were screened serologically for antibodies by ELISA against the virus envelope protein. Seromolecular screening for WNV lineage 1 E-protein genomic region using RT-PCR and DNA sequencing were conducted following which neuroinvasiveness was assessed in RT-PCR-seropositive animals by subjecting their brains to RT-PCR and immunohistochemistry.
Results: All animal types investigated were ELISA-positive with primates and bats having the highest seropositivities of 74% (14/19) and 63% (67/106) respectively. The WNV lineage 1 RNA sequence was also detected serologically by RT-PCR in at least one individual from each animal There was 99-100% sequence identity of the amplified gene in sequenced samples with that of the WNV lineage 1 reference sequence. The virus was also detected by RT-PCR and by immunohistochemistry.
Conclusions: This study has shown the presence of circulating zoonotic and neuroinvasive lineage 1 West Nile Virus in Nigerian wildlife which is of public and veterinary health risk especially to vulnerable human and animal populations in Nigeria.