Zoonoses and Food Safety
Zoonotic diseases are a group of infectious diseases that are naturally transmitted between
vertebrate animals and humans. The greatest risk for zoonotic disease transmission occurs at
the human-animal interface through direct or indirect human exposure to animals, their
products and/or their environments. More than 60% of the newly identified infectious agents
that have affected people over the past few decades have been caused by pathogens
originating from animals or animal products. Seventy percent of these zoonotic infections
originate from wildlife.
In addition, a number of well known and preventable zoonoses continue to occur in many
countries, especially in the developing world where they mostly affect the poorest segment of
human society; some are transmissible to humans through food (brucellosis, tuberculosis),
through bites from infected mammals (rabies) and insects (Rift Valley Fever) or via
environmental contamination (echinococcosis/hydatidosis).
The emergence of zoonotic disease is complex and multifactorial, driven by factors which include
evolving ecology, microbial adaptation, human demographics and behaviour, international travel
and trade, agricultural practices, technology and industry. Addressing zoonotic risk requires
multisectoral cooperation and strong partnerships with strong linkages between human and animal
detection and response systems.
Zoonoses and veterinary public health
(VPH)
Any disease or infection that is naturally transmissible from vertebrate animals to humans
and vice-versa is classified as a zoonosis according to the PAHO publication "Zoonoses and
communicable diseases common to man and animals". Over 200 zoonoses have been
described and they have been known for many centuries. They are caused by all types of
agents: bacteria, parasites, fungi, viruses and unconventional agents.
Some examples of zoonoses, classified according to the type of causative agent, are given
hereafter.
Bacteria
Every year millions of people get sick because of foodborne zoonoses such as Salmonellosis
and Campylobacteriosis which cause fever, diarrhoea, abdominal pain, malaise and nausea.
Other bacterial zoonoses are anthrax, brucellosis, infection by verotoxigenic Escherichia coli,
leptospirosis, plague, Q fever, shigellosis and tularaemia.
Parasites
Cysticercosis/Taeniasis is caused by a parasite which infects swine and can cause seizures,
headache and many other symptoms in humans. In Latin America for example, 100 out of
100 000 inhabitants suffer from this disease (estimation). Other parasitic zoonoses are
trematodosis, echinococcosis/hydatidosis, toxoplasmosis and trichinellosis.
Viruses
Rabies is a disease of carnivores and bats mainly transmissible to humans by bites. Almost all
persons infected by rabid animals will die if not treated. An estimated number of 55 000
persons, mainly children, die of this disease in the world every year. Dogs are responsible for
most human deaths. Other viral zoonoses are avian influenza, Crimean-Congo hemorrhagic
fever, Ebola and Rift Valley fever.
Fungi
Dermatophytoses are superficial mycoses that may be acquired from infected animals and
affect the skin, hair and nails of humans, causing itching, redness, scaling and hair loss.
Another mycotic infection that can be zoonotic is sporotrichosis.
Unconventional agents
The agent of Bovine Spongiform Encephalopathy is thought to be the cause of variant
Creutzfeldt-Jakob Disease (vCJD) which is a degenerative neurological disease different
from CJD, at present inevitably lethal in humans.
Zoonoses still represent significant public health threats, but many of them are neglected, i.e.
they are not prioritized by health systems at national and international levels. They affect
hundreds of thousands of people especially in developing countries, although most of them
can be prevented.