Home | | Microbiology | Zoonotic diseases

Chapter: Microbiology

Zoonotic diseases

Association between man and animals are there since the begin-ning of earth.



Association between man and animals are there since the begin-ning of earth. Man’s association with animals became more intimate that certain diseases are transmitted from animals to man and vice a versa. Zoonotic diseases are transmissible between man and animals. Zoonotic diseases spread by contact with infected animals by handling them or living in their premises. Transmission is through direct contact or aerosol spread. Drinking milk from infected animals is another way of getting zoonotic infections. Insects could transfer mechanically or biologically different zoonotic diseases. These diseases are classified as follows:




Anthrax and Brucellosis are two of the many bacterial zoonotic diseases. Anthrax is a disease caused by Bacillus anthracis. It belongs to the genus Bacillus. Organisms belonging to the genus bacillus are gram positive spore forming bacilli, present ubiquitously in all environ-ments. Many of them do not cause disease in man. Anthrax is an im-portant disease of man and animals and it could be used a biological warfare agent.


Bacillus  anthracis

The typical organism is a gram positive bacillus, measuring 1x3-4 μ m, have square ends and are arranged in long chains. Spores are located in the center of the non motile bacillus. It can grow on ordinary laboratory media like nutrient agar and blood agar. It does not produce haemolysis on blood agar, shows a cut glass appearance, liquefies gelatin.


Anthrax is primarily a disease of sheep, cattle, horse, and many other animals; humans are rarely affected. Infection is acquired by the entry of spores through injured skin or mucous membrane; rarely spores enter the lungs by inhalation. In animals portal of entry is mouth and gastrointestinal tract.

Spores germinate in the tissue at the site of entry, and growth of the vegetative organisms results in the formation of edema. Organisms spread through lymphatics to the blood stream and they multiply in the blood and tissues. Inhalation anthrax is also called wool sorter’s dis-ease. Infection is acquired by the inhalation of spore present on mate-rials from the animal source. Rapid multiplication of the organisms in the tissue is fatal.


Penicillin is the drug of choice. The organism is susceptible to macrolids, aminoglycosides, tetracycline and chloramphenicol. Ciprofloxacin or other fluoroquinalone is recommended for prophy-laxis.


Live attenuated bacilli were first used by Louis Pasteur in 1881. It gave very good protection in domestic animals. Now the Sterne strain of live spore vaccine is used for animal immunization. Live bacterial vaccine is not safe for human use. Alum precipitated Toxoid has been used to immunize the workers at risk of exposure.

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail
Microbiology : Zoonotic diseases |

Privacy Policy, Terms and Conditions, DMCA Policy and Compliant

Copyright © 2018-2023 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.