Abstract
Foot-and-mouth disease (FMD) is endemic in India, where circulation of
serotypes O, A and Asia 1 is frequent. In the past two decades, many of
the most widespread and significant FMD lineages globally have emerged
from the South Asia region. Here, we provide an epidemiological
assessment of the ongoing mass vaccination programs in regard to
post-vaccination monitoring and outbreak occurrence. The objective of
this study was to quantify the spatiotemporal dynamics of FMD outbreaks
and to assess the impact of the mass vaccination program between 2008 to
2016 with available antibody titer data from the vaccination monitoring
program, alongside other risk factors that facilitate FMD spread in the
country. We first conducted a descriptive analysis of epidemiological
outcomes of governmental vaccination programs in India, focusing on
antibody titer data from >1 million animals sampled as part
of pre- and post-vaccination monitoring and estimates of standardized
incidence ratios calculated from reported outbreaks per
state/administrative unit. The percent of animals with inferred
immunological protection (based on ELISA) was highly variable across
states, but there was a general increase in the overall percent of
animals with inferred protection through time. In addition, the number
of outbreaks in a state was negatively correlated with the percent of
animals with inferred protection. Because standardized incidence ratios
of outbreaks were heterogeneously distributed over the course of eight
years, we analyzed the distribution of reported FMD outbreaks using a
Bayesian space-time model to map high-risk areas. This model
demonstrated a ~50% reduction in the relative risk of
outbreaks in states that were part of the vaccination program. In
addition, states that did not have an international border experienced
reduced risk of FMD outbreaks. These findings help inform risk-based
control strategies for India as the country progresses towards reducing
reported clinical disease.