The movement of sheep and goats does not stop at national borders, and neither do the diseases that affect them. Recognizing this challenge, the Food and Agriculture Organization of the United Nations (FAO) is promoting a more targeted approach to animal-health surveillance through the identification of interconnected livestock populations known as episystems.

An episystem brings together sheep and goat populations that are epidemiologically connected through animal movements, shared grazing areas, trading networks, production practices or other pathways that can influence disease transmission. Such populations may stretch across several administrative regions or even international borders.

This approach is particularly important in the global campaign against Peste des Petits Ruminants (PPR), a highly contagious disease affecting small ruminants. FAO says PPR threatens around 80 percent of the world’s small-ruminant population, with confirmed disease occurring across large parts of Africa, Asia and the Middle East.

Why Episystems Matter

Traditional disease-control programmes are often organized around national boundaries. However, livestock production and trading systems frequently operate across those boundaries. A herd vaccinated in one country may still face infection risks if connected populations across a border remain vulnerable.

Mapping episystems can help veterinary authorities understand where disease transmission is most likely to occur and which animal populations are most important for maintaining the virus. FAO’s PPR programme emphasizes identifying populations that play a critical role in maintaining infection and using that information to design appropriate vaccination and surveillance strategies.

Instead of treating every area in exactly the same way, authorities can therefore concentrate resources where they are likely to have the greatest impact.

Better Surveillance, Smarter Vaccination

The episystem concept can strengthen several parts of animal-health planning. Disease surveillance can be directed toward high-risk livestock populations, while vaccination programmes can be designed around actual transmission patterns rather than simply administrative boundaries.

This could improve the efficiency of limited veterinary resources, particularly in regions where pastoralism, seasonal migration and livestock markets connect communities across borders.

FAO’s broader PPR strategy includes surveillance, laboratory capacity, vaccination, animal identification, movement controls, quarantine and improved biosecurity as important components of disease prevention and eradication.

Regional Cooperation Is Essential

Because livestock diseases can move through cross-border networks, cooperation between neighbouring countries is a central part of the strategy. FAO’s PPR framework promotes coordinated approaches between countries and regions, recognizing that disease-control measures in one territory can be undermined when connected populations elsewhere remain exposed.

The idea also fits into a broader shift toward coordinated action against transboundary animal diseases. In 2026, FAO highlighted the importance of regional cooperation, early warning, digital surveillance and country-led partnerships in dealing with diseases that can spread rapidly across borders.

Protecting Livelihoods Alongside Animal Health

The stakes extend far beyond veterinary concerns. Sheep and goats provide food, income, savings and economic security for millions of rural households. FAO notes that PPR can threaten the livelihoods of hundreds of millions of rural families, making disease prevention an important part of food-security and poverty-reduction efforts.

By identifying the livestock populations that are genuinely connected, countries can potentially make surveillance more precise, vaccination more strategic and disease-control efforts more coordinated.

The ultimate objective is not simply to respond faster when outbreaks occur, but to understand how livestock populations interact and use that knowledge to prevent transmission in the first place.

As the global effort to eliminate PPR continues toward the 2030 goal, the episystem approach offers an important lesson: animal diseases may respect no borders, so effective disease control cannot depend on borders alone.