Global patterns of zoonotic disease may predict transmission

WRITTEN BY: Kerry Evans

A new study published in Trends in Parasitology reveals patterns that could be used to predict the locations of future zoonotic disease outbreaks.

Zoonotic diseases are diseases that infect animals and can be transmitted to humans. They can be caused by bacteria, viruses, parasites, and fungi, and can be transmitted in a number of ways.

Direct transmission can occur through the air or from direct contact with fluids like blood or saliva - influenza or rabies, for example. Alternately, zoonotic diseases such as West Nile virus can be spread by vectors like mosquitoes. Fun fact - fairs and petting zoos are actually hot spots for catching a zoonotic disease. In 2005, 63 people contracted E. coli O157:H7 from a Florida petting zoo exhibit.

In this study, researchers at the Cary Institute of Ecosystem Studies and the University of Georgia combed through the available data on zoonotic disease transmission. Their work uncovered patterns that show hotspots for disease transmission.

Some of these patterns surprised study author Barbara Han. “I was rather surprised to see that hotspots of zoonotic diseases didn't match hotspots of biodiversity more closely. For example, there is high species diversity in the tropics, so I expected to see a similar pattern of more zoonotic parasites and pathogens in the tropics as well. We do find more zoonotic hosts in the tropics, but we find more zoonotic diseases in temperate regions, possibly because these diseases can occur in multiple host species”, says Han.

That’s not the only surprise from the study. It turns out that more primates are zoonotic hosts than rodents. (See, stop giving rodents such a hard time.) Bats also carry the fewest zoonotic diseases. (Bats, you’re off the hook). Last, but not least, bacteria were the most abundant pathogens carried by mammals. (Sorry bacteria.)

According to Han, "understanding where animals are distributed and why may not seem applicable to our day-to-day lives … but the big breakthroughs that we need as a society (e.g., forecasting where the next zoonotic disease may emerge) rely on exactly this kind of basic scientific knowledge."