Increasing Focus on Animal Diseases Infecting Humans
The international health community is responding to recent disease crises by focusing more attention and resource on zoonoses -- animal diseases that can also sicken people. The threat of zoonotic diseases was a major theme last week in Atlanta, at the four-day International Conference on Emerging Infectious Diseases (ICEID), and the three-day International Symposium on Emerging Zoonoses that immediately followed it.
Beginning with HIV-AIDS in the 1970s and '80s, and more recently SARS and H5N1 avian flu, animal-originated diseases have increasingly taken center stage in the international fight against disease in human beings.
"Maybe it's because we've been hit with one disease after another after another -- HIV and SARS and mad cow," said Michael Woodford to Bloomberg.com. Woodford is a retired veterinarian living in Portugal, who attended the ICEID conference as a member of a working group on wildlife disease. "But the emphasis is changing. It really is. And the bird flu scare seems to be the tipping point. It has the potential to change our lives in a big way."
Bernard Vallat, Director-General of the Paris-based World Organization for Animal Health, told Bloomberg.com that the problem is that poor nations where dangerous animal diseases exist have little funding available for public health services, veterinary treatment, animal-disease surveillance and to compensate farmers who have to destroy herds and flocks in response to disease outbreaks (such as bird flu) that threaten humans. Vallat said that only about 30 countries that are members of his organization have the resources and systems to respond quickly to outbreaks of disease in animals, leaving 140 that need some support.
Bloomberg.com reports that in response to these new threats, the U.S. CDC is reorganizing its National Center for Infectious Disease, creating four new centers. One of these, the Center for Zoonotic, Vector-borne, and Enteric Diseases, is expected to begin work within weeks. (Dr. Lonnie King, its acting director, is the dean of Michigan State University's College of Veterinary Medicine. Beginning February 2006, King is "on loan" to CDC for a year to direct the agency’s new Office of Strategy and Innovation).
King said that "from SARS, to West Nile virus, to avian influenza, we're living in a new era of emerging diseases and the bulk are zoonotic. We speak of this time as the convergence of animal and human health." He also noted that animals have been the sources of 1) three-quarters of all new human diseases in the past three decades, and 2) 80% of the microbes considered among the most dangerous possible bioterrorist weapons.
CDC is also expanding its veterinary program by training 13 veterinarians in its two-year Epidemic Intelligence Service program, and is building new animal and insect facilities at its Fort Collins, CO site.
New biological threats are constantly being identified in animals that may spread to humans, researchers said at the conference this week. For instance, one study presented at the ICEID identified previously unknown viruses, possibly related to HIV, that are infecting Africans who eat monkey meat.
Here's part of the NYT's coverage of issues discussed at the International Symposium on Emerging Zoonoses(ISEZ):
"We are creating the conditions for the spread of these viruses" that cause zoonoses and human illness through tourism, hunting and farming, said Dr. Bruno Chomel, a professor of zoonoses at the University of California, Davis.
For example, Dr. Chomel said, the corn mouse that carries the virus that causes Argentine hemorrhagic fever has spread its range with changes in farming, leading to outbreaks of the bleeding disease.
The liver infection caused by the hepatitis E virus, which has been detected mainly in poor countries, is being increasingly recognized in wealthy countries in small numbers. Two outbreaks of hepatitis E occurred recently in Japan after people ate raw liver from infected wild boar and deer, Dr. Chomel said.
In 1999, scientists discovered the Nipah virus among pig workers in Malaysia and Singapore who developed inflammation of the brain and respiratory illness. Farming practices on pig farms where fruit trees were abundant created opportunities for transmission of the Nipah virus, said Dr. Peter W. Daniels of the Australian Animal Health Laboratory in Geelong.
Fruit bats carried the Nipah virus, and it was transmitted to pigs that lived in an open farm environment. In turn, the virus was transmitted to humans and their pets.
Additional factors favoring Nipah virus transmission were disrespect for regulations and the frequent breaking of rules to increase profits. It was a lesson that self-regulation must be realistically audited, Dr. Daniels said.
The demand for exotic pets can also spread zoonoses.
Customs inspectors recently stopped the potential spread of A(H5N1) virus in Belgium by catching a man trying to smuggle infected Thai eagles that had been stuffed alive in a roller tube.
Cats, leopards and tigers have died from A(H5N1) avian influenza in southeast Asia and Europe. Though the number of cases is small, they have raised concern that the virus could become a bigger problem among felines. The 10,000 tigers now being kept as pets in the United States outnumber the 6,000 in the wild worldwide, Dr. Chomel said.
Another zoonosis, rabies, killed 50,000 people in 2005, mainly from dog bites in Africa and Asia despite availability of an effective vaccine, according to the World Health Organization.