Comp. lmmun. Mierobiol. inject. Dis. Vol. 13, No. 1, pp. 35-39, 1990 0147-9571/90 $3.00 + 0.00 Printed in Great Britain Pergamon Press plc A SURVEY FOR HAEMAGGLUTINATION-INHIBITING ANTIBODY TO WEST NILE VIRUS IN HUMAN AND ANIMAL SERA IN NIGERIA O. D. OLALEYE, S. A. OM|LABU, E. N. ILOMECHINA and A. H. FAGBAMI Department of Virology, College of Medicine, University of Ibadan, Ibadan, Nigeria (Receit,ed 8 November 1989) Abstract--A survey for West Nile Virus (WNV) haemagglutination-inhibition (HI) antibody was carried out in humans and domestic animals. Human sera were collected from Ibadan, while the animal sera were collected from both Ibadan and Maiduguri. Out of 304 human sera tested, 123 were positive (40%). There was a higher prevalence of HI antibody in adults than children. Sex distribution of positive sera showed that 37% of males and 43% of females had WNV HI antibody. There was no significant difference in the prevalence of HI antibody in both sexes. On the 123 WNV HI positive sera tested, 104 (85%) and 78 (75%) had yellow fever and Potiskum HI antibody respectively. Monotypic WNV virus reactions were frequently found in children while polytypic reactions were frequently found in adults. A total of 200 animal sera were examined, 50 camels, 50 goats, 49 cattle and 51 sheep. The highest prevalence of HI antibody was found in camels (26%), followed by sheep (20%). Percentage of positive sera in other species were: goat (18%) and cattle (6%). Of the 35 WNV HI positive animal sera, 26 and 20% reacted with Yellow fever and Potiskum virus antigens respectively. Key words: West Nile Virus, human, domestic animals, serological survey, R6sum6--Une enqu616 portant sur les anticorps inhibant l'hemogglutination par le virus West Nile (WNV) a 6t6 r6alis6e chez l'Homme et les animaux domestiques. Les serums humains ont 6t6 collectes ~ Ibadan, les serums animaux fi Ibadan et Maiduguri. Des 304 personnes 6tudi6s, 123 &aiait positives (40%). La pr6valence en anticorps 6tait sup6rieure chez les adultes par rapport aux enfants. La distribution des positifs en fonction du sexe est de 37% (Hommes) et 43% (Femmes). Sur les 123 positifs, 104 (85%) et 78 (75%) presentaient respectivement des anticorps contre le virus de la fi6vre jaune et le virus Potiskum. Des reactions monotypiques contre le WNV ont 6t6 fr6quemment trouv6es chez les enfants tandis que chez les adultes les r6actions polytypiques 6talent frequentes. Les s6rums de 200 animaux ont 6t6 &udi6s (50 chameaux, 50 ch6vres, 49 bovins et 51 moutons). La plus grande pr6valence a 6t6 observ6e chez les chameaux (26%) puis les moutons (20%). Les pourcentages de positifs one 6t6 pour les autre especes de 18% (ch6vres) et 6% (bovins). Sur les 35 animaux positifs, respectivement 26% et 20% reagissaient avec les antigenes de fi6vre jaune et de Potiskum. Mots-clef~: Virus West Nile, homme, animal domestique, enqu61~ s6rologique. INTRODUCTION West Nile Virus (WNV), a mosquito-borne flavivirus was originally isolated from human [1]. The virus was isolated for the first time in 1965 in Nigeria during a routine virus surveillance [2]. Serological surveys in certain parts of the country revealed the presence of antibodies to the virus in human populations [3]. In serological surveys to determine the prevalence of arbovirus infections in Igbo-Ora, Boorman and Draper [4] and Guyer 35