Zoonotic Diseases

Whether you own a fish, amphibian, reptile, bird or mammal you can promote your pet's health along with your own by being alert to possible problems. Even if you don't own a pet or come into contact with one, you should be aware that many animals, vertebrates and invertebrates (e.g., snails), living or dead, could have an effect on your health by way of zoonotic diseases.
 
Zoonotic diseases are diseases of animals that can be transmitted to humans. Some of the best known zoonotic diseases include the plague—fleas bite infected rats then pass the disease on when the flea bites a human—rabies, and Lyme disease.

Sources of Zoonotic Diseases

As long as you're in the immediate environment of animals or untreated animal products, you're at risk of contracting a disease or infection that can be traced to them. Sometimes toxins or poisons linked to animals are transmitted to us through the environment.
 
A wide range of health problems may be linked to animals. Some common sources of disease-causing organisms include:
  • contaminated meat or milk
  • food such as fruits, vegetables and other produce such as mushrooms that are contaminated with animal waste or product
  • direct contact with a living animal that causes you an injury or transfers a bacterium, virus, fungus or parasite to you
  • contaminated materials such as soil and water that have come in contact with animals, animal by-products or animal waste.

How Humans Contract Zoonotic Diseases

The nose, ears, eyes and mouth serve as easy points of entry for viruses, bacteria and parasites. This means that air, water, food, soil and direct contact with an animal play a part in assisting disease-causing organisms or infectious agents to enter your body. Of course, cuts and scrapes in the skin can provide entry points as well.
 
The most common way humans are infected with a zoonotic disease is through indirect transmission. Pets are most likely to transmit an external parasite such as a flea or tick, which is infected with the virus. Once the external parasite bites the human, the disease is transmitted. Viruses and bacteria are also transmitted through nasal droplets and feces. Feces may also contain other internal parasites such as roundworms.
 
Sometimes a disease-causing agent in an animal is disease-causing in humans as well. Diseased cattle and swine have had to be destroyed because eating the meat, even when cooked, would have meant that the disease-causing agent would infect white blood cells in humans. Sheep, mink, mule, deer and elk have also been implicated in the transfer of a disease-causing agent. Consumption of deer and elk meat has been implicated in a number of cases of chronic wasting disease, a member of the family that also includes bovine spongiform encephalopathy (a.k.a. mad cow disease).
 
What is important to remember, however, is that an infected animal may exhibit no symptoms of having a disease.

People at Risk of Zoonotic Diseases

Everyone is at risk, but these groups of people are much more susceptible to contracting a zoonotic disease:
  • infants and small children — their immune systems are not yet fully developed.
  • pregnant women — their immune systems may be weakened.
  • the elderly — they may have impaired immune systems.
  • veterinarians and others who work with animals — simple exposure puts this group at highest risk.

Preventing Zoonotic Diseases

There are no guarantees that an individual will or will not contract a disease, but avoiding certain behaviors and practices helps minimize the risk. Of course you'll need to keep up the "pro-active" behaviors such as washing hands with soap and water.
 
Many common practices can help minimize the transfer of harmful bacteria, viruses and parasites to humans and human food. These include:
  • feeding pets commercial or home-cooked food
  • careful disposal of all pet waste
  • preventing cross contamination from raw to cooked food through surfaces such as cutting boards, knives, utensils and human hands
  • thoroughly washing all vegetables
  • cooking meat thoroughly.

Below is a table of the more common zoonotic diseases.

Exotic Animals
Disease
Source
Primary Method of Transfer
Best Prevention
tuberculosis
bacteria in infected animal
inhalation
Avoid the infected animal; once you're diagnosed as infected; some drugs may be effective against contracting the disease.
Farm and Food Animals
brucellosis (undulant fever)
bacteria in diseased livestock (e.g. cow's milk)
ingestion
Avoid contact with diseased cattle, sheep and goats; pasteurize milk.
influenza
virus in infected animal
inhalation
Flu shots; avoid animals exhibiting flu-like symptoms, coughing and sneezing.
leptospirosis
wild and domesticated animals (e.g. rats)
skin contact; ingestion
Avoid contact with animal urine; good sanitation; immunization of animals; rodent control.
salmonellosis
bacteria
ingestion
Avoid contaminated food and water.
Insects and Arachnids
Lyme disease
bacteria carried by deer ticks
bites
Avoid contact with ticks; immediately remove ticks from skin; some repellants may be effective if applied to clothing and skin.
plague
bacteria in rodents
bites
Avoid fleas that transmit bacteria from rodents to humans; rodent control.
relapsing fever
bacteria in rodents
bites
Avoid ticks and body lice; de-lousing and de-ticking; rodent control.
Pets (Companion Animals)
cat scratch disease (CDS)
bacteria in cats
scratches and lesions
Immediately wash scratches in soap and water; flea control.
psittacosis
bacteria in several types of birds
inhalation
Avoid dust from dried bird droppings of parrots, turkeys and pigeons; give pet birds antibiotics (e.g. tetracycline).
rabies
virus in infected animals
bites; scratches; ingestion
Avoid rabid animals; immunization.
toxoplasmosis
parasite in birds or mammals
bites; scratches; ingestion
Avoid playing in uncovered sandboxes or soil contaminated by cat feces; wash fruits and vegetables; pasteurize milk; feed commercial diet.
ringworm
fungus on animal skin
skin contact
Avoid contact with infected animals or objects that have contacted fungal spores.
Wild Animals
hantavirus
virus in rodents
inhalation
Avoid deer mouse droppings and urine; rodent control.
Newcastle's disease
virus in birds
inhalation
Avoid birds and their droppings and secretions.