Pet-Related Diseases and Human Health

Pets provide many benefits to humans. They comfort us and give us companionship. However, some animals can also pass diseases to people; these diseases are called zoonoses. Although animals can carry germs, the Centers for Disease Control and Prevention (CDC) emphasizes that it is important to know that you are more likely to get some of these germs from contaminated food or water than from your pet or another animal you encounter.

A variety of germs can be caught from animals, especially household pets. The rabies virus, which can infect cats and dogs, is one of the most serious and deadly of these microbes. Fortunately, rabies vaccine prevents animals from getting rabies. Vaccines protect people from accidentally getting the virus from an animal. They also prevent people who already have been exposed to the virus, such as through an animal bite, from getting sick.

Dog and cat saliva can contain any of more than 100 different germs that can make you sick. Pasteurella bacteria, the most common, can be transmitted through bites that break the skin causing serious, and sometimes fatal, diseases such as blood infections and meningitis. Meningitis is the inflammation of the lining of the brain and spinal cord.
Warm-blooded animals are not the only ones that can cause you harm. Pet reptiles such as turtles, snakes, and iguanas can give Salmonella bacteria to their unsuspecting owners.

• Bovine spongiform encephalopathy (BSE, also called mad cow disease)
• Cat scratch disease
• Flu (Influenza)
• Giardiasis
• Hookworm
• Rabies
• Ringworm
• Salmonellosis

Cat Scratch Disease (Bartonella henselae infection)
Cat scratch disease (CSD) is a bacterial disease caused by the bacteria Bartonella henselae. Most people with CSD have been bitten or scratched by a cat and developed a mild infection at the point of injury. Lymph nodes, especially those around the head, neck, and upper limbs, become swollen. Additionally, a person with CSD may experience fever, headache, fatigue, and a poor appetite. Rare complications of B. henselae infection are bacillary angiomatosis and Parinaud's oculolandular syndrome.

Sometimes, cats can spread B. henselae to people. Most people get CSD from cat bites and scratches. Kittens are more likely to be infected and to pass the bacterium to people. About 40 percent of cats carry B. henselae at some time in their lives. Cats that carry B. henselae do not show any signs of illness; therefore, you cannot tell which cats can spread the disease to you. People with immunocompromised conditions, such as those undergoing immunosuppressive treatments for cancer, organ transplant patients, and people with HIV/AIDS, are more likely than others to have complications of CSD. Although B. henselae has been found in fleas, so far there is no evidence that a bite from an infected flea can give you CSD.

Pet owners can reduce their risk of getting cat scratch disease:

• Avoid "rough play" with cats, especially kittens. This includes any activity that may lead to cat scratches and bites.
• Wash cat bites and scratches immediately and thoroughly with running water and soap.
• Do not allow cats to lick open wounds that you may have.
• Control fleas.
• If you develop an infection (with pus and pronounced swelling) where you were scratched or bitten by a cat or develop symptoms, including fever, headache, swollen lymph nodes, and fatigue, contact your physician.

Cryptococcus Infection
Cryptococcosis is a fungal disease caused by Cryptococcus neoformans. Most people do not get sick with cryptococcosis, but some people are more likely than others to get this disease. For these people, cryptococcosis can cause serious symptoms of brain and spinal cord disease, such as headaches, dizziness, sleepiness, and confusion.

Cryptococcus neoformans is found in the droppings of wild birds (such as pigeons). When dried bird droppings are stirred up, this can make dust containing Cryptococcus go into the air. People can stir up this dust and then breathe it in when they work, play, or walk in areas where birds have been. Pets, such as dogs and cats, can also get sick with cryptococcosis from this dust, but people do not get cryptococcosis from dogs and cats. A person's age and health status may affect his or her immune system, increasing the chances of getting sick. People who are more likely than others to get cryptococcosis include infants, children younger than five years old, organ transplant patients, people with HIV/AIDS, and people receiving treatment for cancer.

Lyme Disease
Lyme disease is a bacterial disease caused by Borrelia burgdorferi. Within one to two weeks of being infected, people may have a "bull's-eye" rash with fever, headache, and muscle or joint pain. Some people have Lyme disease and do not have any early symptoms. Other people have a fever and other "flu-like" symptoms without a rash. After several days or weeks, the bacteria may spread throughout the body of an infected person. These people can get symptoms such as rashes in other parts of the body, pain that seems to move from joint to joint, and signs of inflammation of the heart or nerves. If the disease is not treated, a few patients can get additional symptoms, such as swelling and pain in major joints or mental changes, months after getting infected.

People get Lyme disease when they are bitten by ticks carrying B. burgdorferi. Ticks that carry Lyme disease are very small and can be hard to see. These tiny ticks bite mice infected with Lyme disease and then bite people or other animals, such as dogs and horses, passing the disease to them.

Whenever possible, you should avoid entering areas that are likely to be infested with ticks, particularly in spring and summer when nymphal (larval form of certain insects, such as silverfish and grasshoppers, resembling the adult form but smaller and lacking fully developed wings) ticks feed. If you are in an area with ticks, you should wear light-colored clothing so that ticks can be spotted more easily and removed before becoming attached. If you are in an area with ticks, wear long-sleeved shirts, and tuck your pants into socks. You may also want to wear high rubber boots (since ticks are usually located close to the ground).

Application of insect repellents containing DEET to clothes and exposed skin, and permethrin (which kills ticks on contact) to clothes, should also help reduce the risk of tick attachment. DEET can be used safely on children and adults but should be applied according to Environmental Protection Agency guidelines to reduce the possibility of toxicity.

Since transmission of B. burgdorferi from an infected tick is unlikely to occur before 36 hours of tick attachment, check for ticks daily and remove them promptly. Embedded ticks should be removed by using fine-tipped tweezers. Cleanse the area with an antiseptic.

You can reduce the number of ticks around your home by removing leaf litter, and brush- and wood-piles around your house and at the edge of your yard. By clearing trees and brush in your yard, you can reduce the likelihood that deer, rodents, and ticks will live there.

Monkeypox
Monkeypox is a rare viral disease that occurs mostly in central and western Africa. It is called “monkeypox” because it was first found in 1958 in laboratory monkeys. Blood tests of animals in Africa later found that other types of animals probably had monkeypox. Scientists also recovered the virus that causes monkeypox from an African squirrel. These types of squirrels might be the common host for the disease. Rats, mice, and rabbits can get monkeypox, too. Monkeypox was reported in humans for the first time in 1970.

In early June 2003, monkeypox was reported among several people in the United States. Most of these people got sick after having contact with pet prairie dogs that were sick with monkeypox. This is the first time that there has been an outbreak of monkeypox in the United States.

The disease is caused by Monkeypox virus. It belongs to a group of viruses that includes the smallpox virus (variola), the virus used in the smallpox vaccine (vaccinia), and the cowpox virus.

In humans, the signs and symptoms of monkeypox are like those of smallpox, but usually they are milder. Another difference is that monkeypox causes the lymph nodes to swell.
About 12 days after people are infected with the virus, they will get a fever, headache, muscle aches, and backache; their lymph nodes will swell; and they will feel tired. One to three days (or longer) after the fever starts, they will get a rash. This rash develops into raised bumps filled with fluid and often starts on the face and spreads, but it can start on other parts of the body too. The bumps go through several stages before they get crusty, scab over, and fall off. The illness usually lasts for two to four weeks.

In Africa, monkeypox has killed between 1 percent and 10 percent of people who get it. However, this risk would probably be lower in the United States, where nutrition and access to medical care are better.

People can get monkeypox from an animal with monkeypox if they are bitten or if they touch the animal’s blood, body fluids, or its rash. The disease also can spread from person to person through large respiratory droplets during long periods of face-to-face contact or by touching body fluids of a sick person or objects such as bedding or clothing contaminated with the virus.

There is no specific treatment for monkeypox. In Africa, people who got the smallpox vaccine in the past had a lower risk of monkeypox. The CDC has sent out guidelines explaining when smallpox vaccine should be used to protect against monkeypox. For example, people taking care of someone infected with monkeypox should think about getting vaccinated. Contact your state or local health department for more information.

Rabies Infection
Rabies is a disease caused by the rabies virus. It may take several weeks or even a few years for people to show symptoms after getting infected with rabies, but usually people start to show signs of the disease one to three months after the virus infects them. The early signs of rabies can be fever or headache, but this changes quickly to nervous system signs, such as confusion, sleepiness, or agitation. Once someone with rabies infection starts having these symptoms, that person usually does not survive. This is why it is very important to talk to your doctor or health care provider right away if any animal bites you, especially a wild animal.

Many kinds of animal can pass rabies to people. Wild animals are much more likely to carry rabies, especially raccoons, skunks, bats, foxes, and coyotes. However, dogs, cats, cattle, or any warm-blooded animal can pass rabies to people. People usually get rabies from the bite of an infected animal. Many animals, such as dogs, cats, and horses are vaccinated against rabies, but you should always wash any bite thoroughly and check with your health care provider about what to do if any animal bites you.

Be a responsible pet owner:

• Keep vaccinations up to date for all dogs, cats, and ferrets. This requirement is important not only to keep your pets from getting rabies, but also to provide a barrier of protection for you, if your animal is bitten by a rabid wild animal.
• Keep your pets under direct supervision so they do not come in contact with wild animals. If your pet is bitten by a wild animal, seek veterinary assistance for the animal immediately.
• Call your local animal control agency to remove any stray animals from your neighborhood. They may be unvaccinated and could be infected by the disease.
• Spay or neuter your pets to help reduce the number of unwanted pets that may not be properly cared for or regularly vaccinated.
• Avoid direct contact with unfamiliar animals:
  • Enjoy wild animals (raccoons, skunks, foxes) from afar. Do not handle, feed, or unintentionally attract wild animals with open garbage cans or litter.
  • Never adopt wild animals or bring them into your home. Do not try to nurse sick animals to health. Call animal control or an animal rescue agency for assistance.
  • Teach children never to handle unfamiliar animals, wild or domestic, even if they appear friendly. "Love your own, leave other animals alone" is a good principle for children to learn.
  • Prevent bats from entering living quarters or occupied spaces in homes, churches, schools, and other similar areas, where they might come in contact with people and pets.

When traveling abroad, avoid direct contact with wild animals and be especially careful around dogs in developing countries. Rabies is common in developing countries in Asia, Africa, and Latin America where dogs are the major reservoir of rabies. Tens of thousands of people die of rabies each year in these countries. Before traveling abroad, consult with a health care provider, travel clinic, or your health department about the risk of exposure to rabies, pre-exposure prophylaxis, and how you should handle an exposure, should it arise.

Ringworm
Ringworm is a skin and scalp disease caused by several different kinds of fungi. Ringworm on the scalp usually makes a bald patch of scaly skin. People with ringworm on other parts of their skin can have a ring-shaped rash that is reddish and may be itchy. The rash can be dry and scaly or wet and crusty. Many different kinds of animals can transmit ringworm to people. Ringworm is transmitted from direct contact with an infected animal's skin or hair. Dogs and cats, especially kittens or puppies, can have ringworm that can be passed to people. Cows, goats, pigs, and horses can pass ringworm to people too. People can also get ringworm from other people and their personal items.

West Nile Virus
See the CDC’s West Nile Virus Web site at: http://www.cdc.gov/ncidod/dvbid/westnile/index.htm

More Animal-borne Diseases (link to separate page)
Anthrax
Brucellosis
Cryptosporidiosis
Hantavirus pulmonary syndrome
Histoplasmosis
Listeriosis
SARS (severe acquired respiratory syndrome)
Toxoplasmosis
Tularemia

Avian Influenza
Go to the CDC’s avian influenza site at: http://www.cdc.gov/flu/avian/

Health Risks Associated With Raising Chickens
http://www.cdc.gov/healthypets/pdf/intown_flocks.pdf

Cryptosporidium Infection
Cryptosporidium infection (cryptosporidiosis) is a parasitic disease caused by Cryptosporidium parvum. It usually causes a mild to severe infection of the gastrointestinal system, including watery diarrhea, fever, abdominal cramps, nausea, and vomiting. Most people get Cryptosporidium infection from contaminated food and water. However, sometimes animals (including farm animals, cats, and dogs) carry this parasite in their feces (stool) and pass it to people. Animals do not have to be ill to pass Cryptosporidium to humans. People with compromised immune systems, such as those undergoing immunosuppressive treatments for cancer, organ transplant patients, and people with HIV/AIDS, are more likely than others to get Cryptosporidium infection.

Individuals can reduce their risk of acquiring cryptosporidiosis from their pets by observing the following recommendations:

• After contact with animals and animal feces (stool), wash your hands thoroughly with running water and soap.
• If you are immunocompromised and are getting a new pet, avoid strays, puppies, kittens and pets with diarrhea.
• If your dog or cat has diarrhea, take it to your veterinarian.
• If you develop symptoms, including diarrhea, vomiting, abdominal cramps, and/or nausea, contact your physician. Be sure to inform him or her of your pet and if it is ill.

Hantavirus Pulmonary Syndrome
Hantavirus pulmonary syndrome is a rare disease caused by a virus (hantavirus). The first symptoms of hantavirus pulmonary syndrome are fever, muscle pain, and being tired. This happens one to three weeks after a person is exposed to hantavirus. Some people also get headaches, dizziness, vomiting, or diarrhea. After about four to 10 days, people who are sick with hantavirus infection begin to cough and have shortness of breath. If someone is sick with hantavirus pulmonary syndrome and does not get help quickly, he or she may die.

Wild rodents can pass hantavirus to people. Several different types of wild mice and rats can be infected with hantavirus and pass it in their droppings, urine, or saliva. The common house mouse does not carry hantavirus. People can get hantavirus when they touch rodent urine, droppings, or places where these animals have nested. Dried droppings or urine can be stirred up in dust and breathed in by people. Hantavirus has not been shown to infect other kinds of animals, such as dogs, cats, or farm animals.

You can protect yourself from hantavirus pulmonary syndrome by doing the following:

• Keep a clean home, especially the kitchen (wash dishes, clean counters and floor, and keep food covered in rodent-proof containers).
• Keep a tight-fitting lid on garbage, and discard uneaten pet food at the end of the day.
• Set and keep spring-loaded rodent traps near baseboards because rodents tend to run along walls and in tight spaces rather than out in the open.
• Set Environmental Protection Agency-approved rodenticide with bait under plywood or plastic shelter along baseboards. These are sometimes known as "covered bait stations." Remember to follow product use instructions carefully, since rodenticides are poisonous to pets and people, too.
• If bubonic plague is a problem in your area, spray flea killer or spread flea powder in the area before setting traps. This is important. If you control rodents but do not control fleas as well, you may increase the risk of infection with bubonic plague, since once the rodents die, fleas will leave them and seek other food sources, including humans.
• Seal all entry holes 1/4 inch wide or wider with lath screen or lath metal, cement, wire screening, or other patching materials, inside and out.

Bacteria and viruses are the microscopic organisms – otherwise known as germs -- that are responsible for causing and transmitting illness and disease. These microbes are so small, that according to the American Society for Microbiology, if the smallest of all microbes was the size of a baseball, an average bacterium would then be the size of the pitcher's mound, and just one of the millions of cells that make up your body would be the size of the ballpark!

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