Zoonotic Diseases Are a Serious Threat to Humans

In October 2008 the World Conservation Society warned that global warming may lead to a more rapid spread of zoonotic diseases. What are zoonotic diseases? Simply stated, they are illnesses that are transmissible from nonhuman to human animals through vectors like fleas, ticks, and mosquitoes or body fluids.

Few people realize just how many diseases are shared among humans and their fellow animals. Approximately 61 percent of the approximately 1,400 human pathogens (viruses, bacteria, parasites and prions) and 75 percent of all newly discovered human diseases are zoonotic. Zoonotic diseases include Plague, Hantavirus, Tuberculosis, Mad Cow Disease, Rabies, Tularemia, Monkeypox, Ebola, HIV/AIDs, West Nile Virus, Lyme Disease, SARS (Sudden Acute Respiratory Syndrome) and Avian Flu.

One recent zoonotic disease, Ebola Fever, was discovered a little over thirty years ago and was first contracted by humans through the consumption of bush meat (the meat of monkeys and apes killed for food). Besides the deaths in Africa, Ebola killed hundreds of imported Philippine macaques used as research animals in a Virginia lab in 1989.

Monkeypox hit the Midwest about five years ago when African rodents imported as pets were housed with American prairie dogs in the shed of an animal dealer. In Japan, a family got Monkeypox from imported prairie dogs. Unfortunately, despite the depopulation of prairie dogs, US animal dealers sell or export as many as 20,000 prairie dogs a year for the pet trade and are particularly popular in Asia.

Rabies has been largely controlled in western countries through vaccination, but it's still a big problem in Asian countries, especially China, where the wild and domesticated animal trade flourishes. Rabies is a threat in raccoons, bats, skunks, coyotes and foxes as well as domesticated dogs and cats raised for slaughter there.

From time to time, the pathogen Salmonella makes the news when it sickens a group of people. Just through contact with reptiles such as iguanas and turtles and other exotics, there have been some 70,000 cases of Salmonellosis in the United States.

The H5N1 strain of Avian (Bird) Flu most likely originated in domesticated poultry in the late 1950s and has since spread to wild birds. Cockfighting, which is still popular in countries like the Philippines, Thailand and Mexico, is one way to spread Avian Flu, and a number of cockfighters have already died from it. Another is factory farming of poultry and ducks. Factory-farmed poultry are crowded together in huge sheds, standing in their own pathogen-filled manure, which is a perfect storm for evolving zoonotic diseases like Bird Flu. Bird Flu is slowly making its way across Asia, Europe and has already appeared in the United States among poultry workers. If Avian Flu should ever mutate and produce a strain contagious among humans, which is likely to occur eventually, it will become a huge global problem.

Other diseases that can easily jump from animal to human are Herpes B Virus (from macaques), Tuberculosis (widespread in the animal kingdom), Psittacosis (parrots and gamecocks) and last but certainly not least, HIV/AIDS (which probably originated in African monkeys). AIDS has killed tens of millions of people so far worldwide, devastating African countries in particular.

Who's to blame for the growing zoonotic disease threat? The culprits are many. Besides the recently recognized threat of climate change, they include the international wildlife trade, cockfighting, and, as noted above, factory farming. The business of killing animals for their body parts or capturing them for zoos, safari parks, canned hunting, game farms, circuses, research and pets, among other reasons, is tremendously profitable for those involved. It is an estimated $20-billion-a-year industry. There are numerous ways for people involved in the wildlife trade to catch a zoonotic disease; hunters and poachers as well as the middlemen and consumers can end up infected. Another way to spread zoonotic disease is in local markets and villages where wild and domesticated animals may eat the remains or waste of infected animals and spread disease.

What country is the biggest consumer of imported wildlife? Sadly, it's the United States, which imports some 10,000 primates, 250,000 birds, two million reptiles and 200 million fish every year. Amazingly, the vast majority of these animals are not tested for disease or parasites at ports of entry. That only happens with commercial bird importation and with some livestock, but fish, reptiles and amphibians are not tested.

What can we do to stop the spread of zoonotic diseases? If we begin to encourage an attitude of respect for nonhuman animals and their right not to suffer for human benefit, close contact with exploited animals will automatically diminish. Wild animals are not appropriate as pets, as biomedical research subjects, or in show business. Children, with their still-developing immune systems, are particularly susceptible to contracting zoonotic diseases from wildlife. We can start to reduce the threat of global zoonotic diseases by monitoring wildlife for disease, restricting or eliminating the wildlife trade, cracking down on cockfighting in countries that still allow it, and replacing factory farming with smaller, safer, cleaner, more humane farming operations.