Zoonoses are human diseases caused by organisms that are acquired from animals. There are bacterial, viral, fungal and parasitic zoonoses. Some zoonotic organisms are acquired direct from the animal reservoir, whereas others are transmitted by vector such as mosquitoes, fleas or ticks.
Zoonotic transmission
Zoonotic infections are classified into two groups viz; zoonotic infections transmitted by scratches, bites and other contact with domestic or mild animals and those transmitted by direct contact or inhalation. The increasing importance of zoonotic infections is occurring for many reasons as follows:
(1) More humans on the planet than ever before.
(2) Movement of these people into previously unpopulated areas.
(3) Increased exposure of people to animals and their infections.
(4) Wild animals are often transported by human to areas that are new for animals.
(5) Increased microbial exchanges between humans and animals.
(6) Interactions between wild animals.
Zoonotic potential of novel virus
Zoonotic infections occur normally in animal populations and rarely jump to humans, and when these rare infections are introduce into a human population, the zoonotic pathogen can be transmitted human to human, resulting in a sustained persistence of the agent in the human population. Some zoonotic agents that have done this include; human immunodeficiency virus (HIV), Influenza, Ebola virus, and severe acute respiratory syndrome (SARS).
As well, Some zoonotic agents are transmitted from animals to humans, but resulting disease is not contagious generally from one person to another. In that case humans essentially represent dead- end hosts and they are as follows; west nile virus, rabies, ehrlichiosis, bubonic plague, tularemia, brucellosis, leptospirosis and Lyme borreliosis.
BACTERIAL AGENTS OF ZOONOSES.
There are mainly four medically important gram negative rids that have significant animal reservoir as follows; Brucella app, francisella tularenisis, yersina pestis and pasteurella multocida.
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