Zoonosis
Zoonosis refers to any infectious disease that can be transmitted from animals, both wild and domestic, to humans. The word is derived from Greek words zoon (animal) and nosos (disease). Many serious diseases fall under this category.
Some agents that can carry zoonoses include:
Zoonoses can be listed according to the infective agent :
Some of the more important zoonoses are:
- Anthrax
- Campylobacteriosis
- Cutaneous larva migrans
- Leptospirosis
- Bubonic plague
- Listeriosis
- Rabies
- Salmonellosis
- Trichinosis
- Toxoplasmosis
- Typhus and other Rickettsial diseases
- Lassa fever
- Ebola fever
- Marburg virus infection
- Ornithosis
- Brucellosis
- Foot and mouth disease (Hand, Foot & Mouth Disease)
This list is by no means complete. The influenza virus is an interesting example of these: it continually recombines genes between strains found in humans, ducks, and pigs, producing new strains with changed characteristics, and occasionally, as in 1918, killing millions worldwide.
Subsection
Sometimes written zoonose. Plural is zoonoses.
The simplest definition of zoonosis is a disease that can be transmitted from animals to humans. A slightly more technical definition is a disease that normally exists in animals, but can infect humans. On other occasions it may be used to mean a disease that can complete its life cycle without a human host. None of these are wrong, although the first is overly simplistic.
Zoonotic diseases are important for a number of reasons:
Most of human prehistory has been spent as small bands of hunter-gathers; these bands were rarely larger then 50 individuals, and were not in contact with other bands very often. Because of this, epidemic diseases, which depend on a constant influx of humans that haven't developed an immune response, tended to burn out after their first run through a population. To survive, a biological pathogen had to be either a chronic infection, staying alive in the host for long periods of time, or have a non-human reservoir in which to live while waiting for new hosts to pass by. In fact, for many 'human' diseases, the human is actually an accidental victim and a dead-end host. (This is the case with rabies, anthrax, tularemia, West Nile virus, and many others). Thus mush of human development has been in relation to zoonotic, not epidemic, diseases.
Many modern diseases, even epidemic diseases, started out as zoonotic diseases. It's hard to be certain which diseases jumped from other animals to humans, but there's good evidence that measles, smallpox, influenza, and diphtheria came to us this way. AIDS, the common cold, and tuberculosis may also have started in other species.
In modern days, zoonoses are of practical interest because they tend to pop out of nowhere and attack humans; at the time of this writing, [[West Nile virus]] is moving into America, and causing much distress. The black plague was a zoonosis, as are salmonella, tetanus, Rocky Mountain spotted fever, and Lyme disease.
Diseases like malaria, schistosomiasis, river blindness, and elephantiasis are not zoonotic, even though they are borne by insects or other animal vectors, because they depend on the human host for part of their life-cycle.