Zoonosis Health Article

Definition

Zoonosis, also called zoonotic disease refers to diseases that can be passed from animals, whether wild or domesticated, to humans.

Description

Although many diseases are species specific, meaning that they can only occur in one animal species, many other diseases can be spread between different animal species. These are infectious diseases, caused by bacteria, viruses, or other disease causing organisms that can live as well in humans as in other animals.

There are different methods of transmission for different diseases. In some cases, zoonotic diseases are transferred by direct contact with infected animals, much as being near an infected human can cause the spread of an infectious disease. Other diseases are spread by drinking water that contains the eggs of parasites. The eggs enter the water supply from the feces of infected animals. Still others are spread by eating the flesh of infected animals. Tapeworms are spread this way. Other diseases are spread by insect vectors. An insect, such as a flea or tick, feeds on an infected animal, then feeds on a human. In the process, the insect transfer the infecting organism.

Some zoonotic diseases are well known, such as rats (plague), deer tick (Lyme disease). Others are not as well known. For example, elephants may develop tuberculosis, and spread it to humans.

Causes and symptoms

The following is a partial list of animals and the diseases that they may carry. Not all animal carriers are listed, nor are all the diseases that the various species may carry.

• Bats are important rabies carriers, and also carry several other viral diseases that can affect humans.
• Cats may carry the causative organisms for plague, anthrax, cowpox, tapeworm, and many bacterial infections.
• Dogs may carry plague, tapeworm, rabies, Rocky Mountain Spotted Fever, and Lyme disease.
• Horses may carry anthrax, rabies, and Salmonella infections.
• Cattle may carry the organisms that cause anthrax, European tick-borne encephalitis, rabies, tapeworm, Salmonella infections and many bacterial and viral diseases.
• Pigs are best known for carrying tapeworm, but may also carry a large number of other infections including anthrax, influenza, and rabies.
• Sheep and goats may carry rabies, European tick-borne encephalitis, Salmonella infections, and many bacterial and viral diseases.
• Rabbits may carry plague and Q-Fever.
• Birds may carry Campylobacteriosis , Chlamydia psittaci, Pasteurella multocida, Histoplasma capsulatum, Salmonellosis, and others.

Zoonotic diseases may be spread in different ways. Tapeworms care often spread to humans when they eat the infected meat of fish, cattle, and swine. Other diseases are transferred by insect vectors, often blood-feeding insects that carry the cause of the disease from one animal to another.

Diagnosis

Diagnosis of the disease is made in the usual manner, by identifying the infecting organism. Each disease has established symptoms and tests. Identifying the carrier may be easy, or may be more difficult when the cause is a fairly common infection. For example, tapeworms are usually species specific. Cattle, pigs, and fish all carry different species of tapeworms, although all can be transmitted to humans who eat undercooked meat containing live tapeworm eggs. Once the tapeworm has been identified, it is easy to tell which species the tapeworm came from.

Other zoonotic infections may be harder to identify. Sometimes the infection is fairly common among both humans and animals, and it is impossible to tell. Snakes may carry the bacteria Escherichia coli and Proteus vulgaris, but since these bacteria are already common among humans, it would be difficult to trace infections back to snakes.

Because of increased trade between nations, and changes in animal habitats, there are often new zoonotic diseases. These may be found in animals transported from one nation to another, bringing with them new diseases. In some cases, changes in the environment lead to changes in the migratory habits of animal species, bringing new infections.

Treatment

Treatment is the established treatment for the specific infection.