There are many different infectious animal diseases, but not all of them are zoonoses or zoonotic diseases. What are zoonotic diseases? The World Health Organization (WHO) defines zoonotic diseases as “…disease(s) or infection(s) that (are) naturally transmissible from vertebrate animals to humans.” Whenever discussions about human infectious diseases come up, the role of animals in the transmission of some of the causative agents is often brought forward.
Many of the different animal diseases can cause infection to humans, with over a hundred diseases of vertebrate animals capable of being transmitted naturally and directly from both domestic and wild animals to humans. This makes all zoonotic diseases potential threats to human health.
Bacteria, viruses, fungi and protozoans all cause zoonotic diseases. The point at which these causative agents enter the body may be any one of these four usual portals: the mouth, the skin, the respiratory tract, or mucous membranes.
Some examples of zoonotic diseases that are caused by bacteria are brucellosis (from cats, cattle, deer, dogs, fowl, goats, horses, mules, rabbits, sheep, or swine), glanders (from horses), murine typhus fever (from rats), plague (from rodents), psittacosis (from birds or domestic fowl), Q fever (from birds, domestic animals, or rats), Rocky Mountain spotted fever (from wild rodents), and tularemia (from birds or wild animals).
Three examples of zoonotic diseases caused by viruses are equine encephalitis (from birds, horses, or mules), jungle yellow fever (from lemurs, marmosets, or monkeys), and rabies (from bats, cats, dogs, or skunks). Histoplasmosis (from birds or domestic fowl) and ringworm (from cats, dogs, or other domestic animals) are two examples of zoonotic diseases that are caused by fungi. Those that are caused by protozoans include leishmaniasis (from insect bites), malaria (from monkeys), and trypanosomiasis or Chagas’ disease (from cats, dogs, or rodents).
All zoonotic diseases, regardless of the natural host or types of organism responsible for the disease, have several common characteristics. For those who have close contact with animals or animal products (such as farmers, butchers, or veterinarians), for example, zoonotic diseases are obvious occupational hazards. Anthrax, primarily a disease of herbivorous animals which generally appears as a disease of the skin in humans, is a perfect example of such occupational disease.
If eating meat or products of diseased animals is the cause of the disease in humans, the disease will resemble that in the animal. Also in humans, these diseases are clinically similar to those in animals if the point of entry is the same in both. Finally, note that zoonotic diseases are seldom transmitted from person to person.
Sources:
1. “Zoonosis”, the Wikipedia – http://en.wikipedia.org/wiki/Zoonosis
2. “Zoonoses and veterinary public health (VPH)”, World Health Organization – http://www.who.int/zoonoses/en/
