Human Deaths from Animal Diseases on the Rise
Pastor Dale Morgan
Human Deaths from Animal Diseases on the Rise*
Jeanna Bryner
LiveScience Staff Writer
Nov 9, 1:20 PM ET
An estimated 50 million people caught diseases from animals such as
dogs, cattle, chickens and mosquitoes between 2000 and 2005, according
to a new study. Some 78,000 of them died.
The finding reveals the global urgency for doctors to stay vigilant when
it comes to zoonotic illnesses—those transmitted by non-human animals.
By reviewing past studies, virologist Jonathan Heeney of the Biomedical
Primate Research Center in The Netherlands found the diseases
responsible for the majority of zoonotic illnesses seem to be increasing.
Zoonotic killers between 2000 and 2005 included: Rabies (range of host
animals such as dogs, cats and horses): killed an estimated 30,000
people Dengue Virus (spread by mosquitoes): affected 50 million people
and killed around 25,000 Japanese Encephalitis Virus (spread by
mosquitoes): up to 15,000 estimated deaths Lassa Fever (spread by a
rodent known as the "multimammate rat”): affected up to 300,000 people
and killed about 5,000 SARS Corona virus (host unknown): killed 774 of
the 8,102 people infected
What’s worrisome is there are no effective vaccines for some of the most
common zoonotic viruses. Heeney said doctors and veterinarians need to
work together to tackle this increasing global threat.
Most recently, the bird flu, or H5N1, has garnered public attention for
its potential not only to spread from chickens and other birds to
humans, but also for the virus to mutate in a way that allows it to
spread between humans. During the study period, bird flu killed just
over half of the 145 people infected with the virus.
“This comes on the heels of other major zoonotic viral epidemics in the
last decade,” Heeney noted in the November issue of the Journal of
Internal Medicine. These include severe acute respiratory syndrome
(SARS), West-Nile virus, Ebola virus and monkeypox.
An estimated 700,000 to 2.7 million people — 75 percent of them African
children— die of malaria each year. However, malaria doesn’t count as a
zoonotic disease, because the virus depends on a human host for part of
its life cycle.
There has been a global resurgence of Dengue virus, which is transmitted
between monkeys in the jungle by the mosquitoes that feed on them. This
same cycle could move into urban areas, where the mosquitoes could
infect humans. Heeney attributes the rise to growth around large cities,
increased transportation and failing public control measures.
Animal viruses like these have the potential to devastate humans. Over
time, viruses can develop the needed “machinery” for efficient
transmission not only from the animal host to humans, but from human to
human. When this happens, Heeney said, zoonotic illnesses can become
serious human killers with potential to reach epidemic proportions.
While vaccines have eradicated devastating human diseases, such as
smallpox, other related viruses, such as monkeypox, could hit people
whose smallpox vaccines have expired.
This animal-human connection can go both ways. For instance, a deadly
parasite called Toxoplasma gondii, which causes a food-borne disease in
humans, has caused lethal brain damage in California sea otters.
Scientists have also reported that a combination of toxic chemicals and
human herpes virus causes cancer in California sea lions.
Heeney stressed the importance of doctors in all walks of medicine
working together.
"They are in the best position to identify trends and patterns, such as
increases in the number of deaths of wild or domestic animals," Heeney
said. "Awareness and surveillance of ecosystems will play a key role in
identifying and controlling new, emerging and re-emerging viral zoonotics."