Towards the strategic control of endemic foot-and-mouth disease in Africa: new techniques for a neglected problem

Cleaveland, Haydon, Reeve, Lembo

Foot-and-mouth disease (FMD) is a very serious viral disease of cloven-hooved animals, which causes immense economic losses through its impacts on animal health, productivity, and consequent trading constraints.  While the biology of foot-and-mouth disease virus (FMDV) is quite well-understood as it occurs in outbreak settings in developed countries, this understanding has not been applied to regions of the world where the virus is permanently present.  This is particularly unfortunate, since FMD has serious impacts for small-farmers, and previous studies rank FMD as one of the most important livestock diseases associated with poverty.

Tanzania has the third largest population of domestic livestock in Africa, and livestock are critical for the nutrition and economic welfare of the millions of people who live in rural Tanzania.  Rural communities depend directly on livestock for food, milk, use of animals in crop production, and in raising money through local sales.  FMD causes animals to lose weight, reduce milk production, become immobile, and reduce in financial value, and therefore its control is particularly important for communities who depend directly on the well-being of their livestock.

FMDV is often found to infect buffalo and other wild ungulates, and wildlife are often suspected to be either the direct of ultimate source of viruses causing disease in domestic livestock.  This has led to conflict between the management of wildlife, which is itself a hugely important financial resource in countries like Tanzania, and domestic livestock, with calls for the construction of fences similar to those constructed in southern Africa that serve to reduce contact between domestic livestock and wildlife.  There is an urgent need to understand how important wildlife is as a source of FMD for domestic livestock, and to find more environmentally-friendly ways of preventing the virus from moving out from wildlife sanctuaries.

FMD can be controlled through the use of vaccination, but the vaccines are not perfect, providing only short-lived protection from the symptoms of the disease rather than infection itself, and protecting against only a limited range of genetic types of the virus.  In order to use vaccination effectively, it is critical to know the genetic types of the virus that are likely to cause infection in animals, so that the best vaccines can be chosen.  Unfortunately, although quite easily obtained, this knowledge is almost completely lacking from very large areas of Africa in which the virus is thought to be present. 

This project aims to conduct a large-scale survey of FMD in livestock and wildlife in 10 different areas across Tanzania.  Blood samples will be collected from domestic livestock and wildlife and tested for evidence of previous infection by FMD and this will provide a crude picture of the most important types of virus that are present.  Where virus is actually isolated we will sequence parts of the genome to obtain much more detailed information on the virus types. 

We will also focus on one area in northern Tanzania to carry out a more detailed longer-term study, collecting blood samples from herds at regular time intervals and collecting viruses during FMD outbreaks and sequencing them. Using these data, we will be able to determine where virus that causes infections comes from (is it wildlife or other domestic animals in the region, or does it evolve within the herds that its infecting?).  We will also study the role of animals that have long-term infections of FMDV, identify other farming practices that are associated with infection by FMDV, and study just how much immune protection caused by infection with one strain can protect animals from infection with other strains.