Longitudinal study of foot-and-mouth disease virus in Northern Nigeria: implications for the roles of small ruminants and environmental contamination in endemic settings

Figures

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  Figure 1. Maps showing the location of the study areas. A Bassa and Jos South local government areas (study sites) in Plateau State, Nigeria where sampling for foot-and-mouth disease virus was carried out between March and October 2021; and B Kanke and Wase local government areas in Plateau State where foot-and-mouth disease outbreaks were reported during the study period.

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  Figure 2. Longitudinal oral swab and serum sampling for the presence of foot-and-mouth disease virus (FMDV) in cattle, sheep and goats in northern Nigeria between March and October 2021. FMD viral genome was detected by rRT-PCR (PCR), and antibodies to FMDV non-structural proteins (NSP) were detected by ELISA. Sera and oral swabs were paired (i.e. collected from the same animal). Samples were collected from animals at households (H1-H5), one livestock market (LM) and one transhumance location (T) in both Bassa and Jos South local government areas. Coloured shading indicates the proportion (%) of positive samples; grey shading indicates that no samples were collected. Note: households sampled in March are not the same as those sampled in April–October.

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  Figure 3. Longitudinal environmental sampling for the presence of foot-and-mouth disease virus (FMDV) in northern Nigeria between March and October 2021. Samples collected from households (H1-H5), one livestock market (LM) and one transhumance location (T) in both Bassa and Jos South local government areas. Coloured shading indicates the proportion (%) of samples positive for FMDV RNA by rRT-PCR; grey shading indicates that no samples were collected. Note: households sampled in March are not the same as those sampled in April–October.

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  Figure 4. Probability of a sample being positive for foot-and-mouth disease virus (FMDV) RNA by rRT-PCR or antibodies against FMDV non-structural proteins (NSP). Samples were collected during a longitudinal study in Bassa and Jos South local government areas between April and October 2021. Sample types tested by rRT-PCR were serum (S, red), oral swabs (O, blue) and environmental swabs (E, magenta). Samples tested by NSP ELISA were from cattle (green), sheep (cyan) or goats (yellow). Violin plots show the posterior median (circle), interquartile range (line) and density (shape) for the probability.

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  Figure 5. Relationship between age and seroprevalence for foot-and-mouth disease virus (FMDV) in cattle and sheep, by household, in Bassa and Jos South local government areas. Each plot shows the observed seroprevalence (i.e. proportion (%) of animals positive for antibodies to FMDV non-structural proteins by ELISA) at each age (triangles) and the expected seroprevalence based on the estimated force of infection (posterior median: black line; 95% credible region: coloured shading) for cattle (green) and sheep (cyan).

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  Figure 6. Phylogenetic tree showing the relationship amongst foot-and-mouth disease virus VP1 sequences. Sequences were generated from five samples collected during the present longitudinal study in northern Nigeria in 2021 (highlighted in yellow) and other sequences in the FAO World Reference Laboratory for FMD (WRLFMD) database. An asterisk (*) indicates virus designations not assigned by the WRLFMD.