Abstract
We developed a model to quantify the effect of factors
influencing the spatio-temporal distribution of foot-and-mouth
disease (FMD) in Tanzania. The land area of Tanzania was divided
into a regular grid of 20 km x 20 km cells and separate grids
constructed for each of the 12-month periods between 2001 and
2006. For each year, a cell was classified as either FMD
positive or negative dependent on an outbreak being recorded in
any settlement within the cell boundaries. A Bayesian
mixed-effects spatial model was developed to assess the
association between the risk of FMD occurrence and distance to
main roads, railway lines, wildlife parks, international borders
and cattle density. Increases in the distance to main roads
decreased the risk of FMD every year from 2001 to 2006 (ORs
ranged from 0.43 to 0.97). Increases in the distance to railway
lines and international borders were, in general, associated
with a decreased risk of FMD (ORs ranged from 0.85 to 0.99).
Increases in the distance from a national park decreased the
risk of FMD in 2001 (OR 0.80; 95% CI 0.68-0.93) but had the
opposite effect in 2004 (OR 1.06; 95% CI 1.01-1.12). Cattle
population density was, in general, positively associated with
the risk of FMD (ORs ranged from 1.01 to 1.30). The spatial
distribution of high-risk areas was variable and corresponded to
endemic (2001, 2002 and 2005) and epidemic (2003, 2004 and 2006)
phases. Roads played a dominant role in both epidemiological
situations; we hypothesize that roads are the main driver of FMD
expansion in Tanzania. Our results suggest that FMD occurrence
in Tanzania is more related to animal movement and human
activity via communication networks than transboundary movements
or contact with wildlife.