Management of footrot in small ruminants in hill districts of Nepal

• Monash University, Australia

There are about 3 million sheep and goats in Nepal. Along with cattle and buffalo, these are an integral component of the traditional farming system of the hill people. The small ruminants provide wool and fibre, meat and milk. Moreover, their manure provides essential fertiliser for the terraced fields on which the villagers grow wheat, millet, barley, rice and maize.

Footrot of sheet and goats - a painful and debilitating disease that puts severe constraints on productivity - was introduced to the hill districts of the Western Region of Nepal in imported sheep about 20 years ago. Initially it spread to many small flocks, in total containing up to 50 000 sheep and goats.

However, concerted efforts by Ministry of Agriculture officers and staff of the UK Overseas Development Administration (ODA)-funded Lumle Regional Agricultural Research Centre (LRARC) stopped the spread and eliminated the disease from many flocks. Nevertheless, about 100 flocks remain in which the disease persists, despite the best eradication efforts.

Given the husbandry system that is practised in Nepal - where sheep and goats graze/browse in three different environments in the course of an annual cycle - while footrot remains in some flocks there is potential for it to spread again, perhaps throughout the country.

This project was set up following a request by LRARC for assistance from Prof. Egerton - one of the leading researchers on footrot in Australia. Prof. Egerton's group at the University of Sydney's Department of Animal Health will collaborate with Nepalese colleagues to research the problem in both Nepal and Australia. The research will be based on the recognition that, in flocks where footrot eradication fails, this is due to relapse and reinfection of flocks during the migration of animals to and from the alpine pastures in summer.

The project will examine three hypotheses:

. That conventional eradication methods result in the persistence of infection in a low frequency of carrier animals;

. A relatively new technique, the polymerase chain reaction (PCR), shows promise in its application to footrot; and

. The technique permits a diagnosis of infection when only a small number of organisms is present by multiplying organism-specific DNA to levels that can be tested.

In continuing collaboration with Monash University, Prof. Egerton's group will further develop the test to a level where it can be used to distinguish between infected flocks and those free of infection.

The evaluation phase of PCR testing will be done in Australia, where there will be access to identified sheep over a defined period. (In Nepal, animals are virtually inaccessible when they migrate to the alpine pastures.) The eventual application of the test in Nepal will be to flocks that are apparently free of infection.That treatment of all animals with long-acting antibiotic at the conclusion of an eradication program will eliminate infection in sub-clinical cases

Normally, use of injected antibiotics in eradication programs is restricted to clinically infected animals. The current program of footrot eradication in Nepal could readily be supplemented by injecting whole flocks with lon-acting terramycin before departure of sheep to the summer pastures. That hyperimmunisation of animals with purpose-made vaccines will discourage or eliminate the persistence of the footrot organism (Bacteroides nodosus) in carrier animals (and its subsequent regrowth when environmental conditions are more favourable)

Because footrot in Nepal seems to have arisen from a few imported sheep, there is a high probability that only one serogroup of B. nodosus is involved. An essential prerequisite to the preparation of a designed vaccine will be isolation and characterisation of those strains of B. nodosus now established in Nepal. Research in both Australia and Nepal will evaluate the comparative application of antibiotics and hyperimmunisation to replicated flocks and determine their roles in eliminating infection.

The ultimate goal of the project is the elimination of footrot in Nepal. Irrespective of this goal, the project will establish new diagnostic skills in Nepal, identify the strains of B. nodosus present, and provide training in planning, executing and evaluating filed investigations. Stock owners and shepherds will be the main beneficiaries.

The project has considerable potential value for Australian sheep growers. They also have the problem of carrier animals, and the results of the investigation of alternative methods of B. nodosus elimination will be equally applicable in Australia. If it can be shown that hyperimmunisation is a feasible method for eliminating footrot, this could lead to increased vaccine sales both in Australia and overseas.