THE EFFECT OF TRANSHUMANCE ON THE EPIDEMIOLOGY OF ANIMAL DISEASES

Transhumance, the seasonal movement of people and their livestock to r egions of different climate is a way of life for tens of millions of p eople living in the cool mountainous or the arid and semi-arid regions of the world, Transhumant peoples migrate through and spend most of t he time in areas where there are invariably no veterinary, medical or educational facilities, nor abattoirs, safe water supplies or sanitati on. Prevalent diseases go unrecorded and there are rarely any attempts made at disease control, The epidemiology of different diseases in tr anshumant communities is additionally influenced by their peculiar ani mal husbandry practices, the different species of livestock maintained , the close association of humans and their livestock and the small is olated groups and their frequent migrations. The frequency of these mi grations will remove them from the build-up of free-living parasites i ncluding most of the faecally transmitted protozoans and helminths and also from the huge numbers of nuisance flies. Migrations, however, in crease their chances of coming into contact with geographically limite d or seasonally abundant diseases. In Africa, these include, Trypanoso ma spp. and Cowdria ruminantium, which have a profound effect on migra tion patterns. Migrations also increase the opportunity for the intera ction of domestic and wild animals, which facilitates the transmission of a number of shared diseases, particularly bacterial, viral, ricket tsial and protozoan infections. Temperature and relative humidity play an important role in determining the distribution of those parasite s pecies which have free-living forms or have indirect life cycles, part icularly those involving invertebrate hosts. The relative importance o f all the above factors on the epidemiology of different parasite spec ies found in the cold and/or arid regions of the world occupied by tra nshumant peoples and their livestock is discussed.