Taking The Cows To Town

Rural Africans are bringing their livestock with them as they move to the cities, and that is causing a number of problems:

Dagoretti, a district of Nairobi, is a maze of tin huts and wood shacks. Since the 1970s, it's grown from about 40,000 residents to roughly 240,000, springing up haphazardly as Nairobi spilled over into the surrounding land. There aren't clearly delineated plots so much as a mass of semiformal homes belonging to former country folk who've arrived in search of economic opportunity.
Today, about 40 percent of the African population lives in urban areas, a rapid migration that's expected to triple in size over the next four decades.
But the people who are moving to cities aren't entirely leaving their rural lives behind. Instead, they are bringing their livestock with them, often keeping them right in their backyards, even in densely populated areas.
As a result, low-income countries have started to see a dramatic spike in a class of disease known as zoonoses, which pass from animals to humans. These can cause everything from tapeworms to fatal diarrhea, and they're concentrated near major cities in Africa and India.
A recent study by the International Livestock Research Institute found that zoonoses make up 26 percent of the infectious disease burden in low-income countries, but just 0.7 percent in high-income countries.

The article goes on to say that in spite of the health risks, economic issues make it better to keep the livestock then to leave them behind.  As far as diseases go, I would guess modern science would have an easier time controlling some of these than some of the antibiotic-resistant diseases that migh come out of our confinement facilities.  That said, it seems that new strains of flu often come from areas where people live with their livestock.