SPATIO-TEMPORAL AND MOLECULAR EPIZOOTIOLOGY OF FOOTAND- MOUTH DISEASE IN CATTLE IN NORTH-CENTRAL NIGERIA, 2011-2014

Abstract

Foot-and-Mouth Disease (FMD) caused by FMD Virus (FMDV) is an economic limitation to cattle production. The current epizootiological status of FMD and circulating serotypes of FMDV in north-central Nigeria is unknown. Spatio-temporal and molecular techniques are important to the study of FMD spread, ultimately leading to the prevention and control of the disease. This study was designed to determine the seroprevalence, associated risk factors of seropositivity, circulating serotypes and their spatial distribution, as well as isolate and characterise FMDV in cattle herds in North-Central Nigeria. A cross-sectional study was undertaken from February 2013 to April 2014; using three-step multistage sampling, 1,206 sera were collected from 150 herds in Plateau (n=589) and Niger (n=617) states. For molecular study, tongue epithelial specimens (n=40) from lesions of clinically sick animals were collected purposively between June 2011 and October 2014 from north-central states (Plateau 26; Kogi 4; Nassarawa 6; Benue 4). Seroprevalence was determined using FMD 3ABC ELISA kit and associated risk factors were determined using pre-tested questionnaire (n=150) administered to participating farmers. Circulating serotypes were determined using FMDV serotypes-specific ELISA and antigen-detection ELISA. Spatial distribution was done using purely spatial cluster analysis. The FMDVs were isolated using foetal goat tongue cell line and bovine thyroid glands cell line. Virus characterization was done using PCR, sequencing and phylogenetic analyses of the VP1 gene. Sequence comparisons were made with other country reference strains in gene bank. Multiple sequence alignment was done. Data were analysed using descriptive statistics, chisquare and logistic regression at α0.05. Overall seroprevalence of 71.0% was recorded (Plateau 54.2%; Niger 85.4%). Risk factors associated with FMD seropositivity were management system (OR 9.31; CI 4.81-19.02), trans-boundary crossing (OR 5.12; CI 3.75-7.43), herd mixing at the watering point (OR 171.83; CI 23.82-1253.02) and age (OR 1.14; CI 0.83-1.48). The FMDV serotypes A, O, SAT 1 and SAT 2 were found to be diffusely distributed and co-circulating in north-central Nigeria. Sequence analysis of serotype A revealed that the virus was within Africa typotypes which belong to genotype G-IV. They were closely related with FMDV from Bauchi state (94.7%), Cameroon (93.0%) and Togo (90.0%). Serotype O isolates were iv within the West Africa (WA) topotypes and East Africa-3 topotypes (EA-3). Isolates from Plateau state revealed close genetic relationship with sequences from Adamawa state (98.1%) and Cameroon (87.0%); isolates from Kogi state had sequence similarity with those from Togo (94.7%), Ghana (93.9%) and Benin (92.8%). Benue state isolates clustered with FMDV isolates from Plateau state (98.6%) and Sudan (94.2%).The VP1 region of FMDV SAT 2 showed that it belonged to topotype VII. The isolates had a close genetic relationship with SAT 2 isolates from Liberia (93.5%), Niger (92.1%), Senegal (91.5%), Sudan (91.1%) and Cameroon (91.4%). The spatio-temporal pattern of Foot-and-Mouth Disease virus in north-central Nigeria indicated trans-boundary spread of serotype O East Africa-3 topotype. Use of Foot-and- Mouth Disease virus serotypes A, O, SAT 1 and SAT 2, with East Africa-3 topotype in vaccine production and animal movement restriction will enhance the control of this disease in the region. Keywords: Foot-and-Mouth Disease, Serotype O, Topotype, Transboundary spread, VP1 gene.