Washington - Crowded living conditions, moving to new places and eating unusual foods can spread disease - among wild animals, too.
A new study warns that when it comes to the globalisation of the planet, animals face a lot of the same hazards as people, including emerging infectious diseases.
"We call it pathogen pollution," said Peter Daszak, of the University of Georgia, lead author of a paper appearing in Thursday's edition of the journal, Science.
These diseases can cause local extinctions among wild animals and, in some cases, could even lead to total extinction of a species, he said.
Diseases in wildlife not only threaten the future of the animals, but may also form a reservoir of germs that may harm people and domestic animals.
This type of transmission may have been a factor in the emergence of the virus that causes Aids, as well as the newer Marburg and Ebola viruses, the paper notes.
The international transport of livestock and modern agricultural practices have led to the spread of rinderpest in Africa and mad cow disease in Europe, for example.
Even the most innocent-seeming act can pose problems.
"Recent analysis suggests that 15 000 tons of peanuts are fed annually to United Kingdom garden birds. This form of provisioning has led to the emergence of infection by salmonella and E coli in Britain ... because of the high density and diversity of birds at feeding stations," the scientists reported.
Similar reports have occurred in the United States.
Bringing animals together in zoos and wild animal parks in an effort to conserve them may also cause problems. A type of herpes virus that is harmless to African elephants can be fatal to their Asian cousins.
Zoo animals in the United Kingdom have been exposed to food contaminated with the agent that causes mad cow disease. They reported that that exposure to the agent, called BSE, has been found in 58 zoo animals of 17 species.
The study also found that "measles contracted from humans threatens wild mountain gorillas habituated to tourists and polio virus has killed chimpanzees in Gombe National Park in Tanzania." - Sapa-AP