Review/Oorsig Volume 23, Issue 02 - Page 8

Oorsig/Review Peculiarities of Foot and Mouth Disease in Southern Africa and Resulting Implications Gavin Thomson BVSc, MSc, PhD Background It’s remarkable that Foot and Mouth Disease is so widely misunderstood bearing in mind the international importance ascribed to it. The disease generally kills few animals and does not cause disease in humans; yet in the wider animal health world it is often considered the most important disease of livestock. Part of the explanation is that in intensive livestock production systems such as large piggeries and dairies, it can have devastating effects and can destroy commercial enterprises overnight. On the other hand, in extensive rangeland systems its presence, certainly in much of Southern Africa, may be difficult to detect because the disease is so mild or even unapparent. The considerable impact of FMD in Southern Africa relates to its profound trade effects; parts of the world free from FMD go to great lengths to avoid importing what they consider risky commodities or products. It is important to appreciate that the FMD virus genus (Aphthovirus) has two distinct branches or lineages: (1) comprising the three SAT 1 types (1, 2 & 3) and (2) the so-called Eurasian serotypes – A, O, C & Asia 1 (Fig. 1). FMD virus family tree showing 2 dis8nct lineages Eurasian types (O, A, C & Asia 1) – evolved over last 500 years, mainly in domes@c livestock, in Eurasia SAT X SAT X – progenitor – probably originated in African buffalo ≈ 1 000 years ago Fig 1. FMD virus Family Tree showing 2 distinct lineages The Eurasian lineage (molecular genetic studies suggest) split from the progenitor SAT lineage (maintained by African buffalo) about 500 years ago. Since then the Eurasian types have evolved, mainly in Eurasia, in association with cloven- hoofed livestock. Essentially therefore, the SATs are African buffalo viruses while the Eurasian types are livestock viruses that originally evolved in Eurasia, although some types – particularly O and A – have spread far and wide since the early 19th Century. Including in Africa where they are endemic to the northern portions of some southern African countries such as Zambia and Malawi. SAT – abbreviation for ‘South African Territories’, the name given to these viruses when they were first identified by The Pirbright Laboratoty, UK in the 1950s 1 8