(CNN) -- A potentially fatal sheep and goat disease could spread from Tanzania into southern Africa, a United Nations agency warned, threatening millions of people's livelihoods and food supplies.
Small ruminants' plague can cause death rates of up to 100 percent in sheep and goats, though it does not affect humans, the Food and Agriculture Organization warned.
It could kill 50 million sheep and goats if it spreads into southern Africa, the agency said after an emergency mission to Tanzania, in east Africa.
"Sheep and goats are critical to food and income security for pastoral communities. The presence of the disease directly affects a family's wealth," agency's chief veterinary officer, Juan Lubroth, said Tuesday.
He urged southern African nations to review border controls and surveillance and to make sure their veterinary services are prepared.
And the agency advised Tanzania to "initiate an emergency vaccination program" in the north, where the outbreak is centered, and consider additional vaccination in the area bordering Malawi, Mozambique and Zambia.
Tanzania did not immediately issue a public response to the warning.