Zoonosis

Any infectious disease that can be transmitted (in some instances, by a vector) from non-human animals to humans or from humans to non-human animals (the latter is sometimes called reverse zoonosis) In a study of 1415 pathogens known to affect humans, 61% were zoonotic. The emergence of a pathogen into a new host species is called disease invasion. 

Infectious disease surrounds us – It is one of the basic processes of ecology alongside others such as predation, competition and photosynthesis. Throughout history predators are usually big beasts that eat their prey from the outside in, disease causing agents (pathogens) are small beasts that eat their prey from within. 

 Accidents happen, aberrations occur, opportunities and circumstances change and when a pathogen leaps from a non-human animal into a person and by so doing causes a disease problem the result is known as “zoonosis”.

 Interspecies pathogen leap is a common occurrence, more than 50% of human infectious diseases are shared between non-human animals and people; diseases such as:

Bovine tuberculosis.

Bubonic plague.

Ebola.

Hendra.

Lyme Disease.

Marburg.

Monkey Pox.

Nipah.

Rabies.

West Nile Fever.

Yellow fever.

Close contact between two species presents an opportunity for a pathogen to move from one species to another, broadening its horizons by expanding its ability to spread from its original reservoir host into a new species and by so doing increasing its abundance and geographic reach.

Close contact between non-human animals and humans occurs in differing ways, animal husbandry, domestic pets (exotic type), consumption of wild animals, and closer contact with wild life by disruptive penetration of humans into the wild landscape.

 Speed of travel and its availability as well as the large numbers of humans existing on this crowded planet we live on are contributing factors once a pathogen crosses over from non-human animals to humans.

 Infectious disease is caused by parasites (pathogens) capable of damaging their host. These include some, but not all, members of the viruses, bacteria, fungi, protozoa, worms, and prions.

Infections are held in check, where possible, by the immune system, operating at several levels, depending on the evasion strategies adopted by the pathogen.