Reptiles: Zoonoses

Synopsis: There are several diseases that can be transmitted from pet reptiles and amphibians to humans. However, by practicing good sanitation and personal hygiene, keeping herps out of the kitchen and food preparation areas, it is possible to minimize the risk. It is also important to have all new herps examined and tested prior to introducing them to your home.

Nobody likes to think about it, but the truth is that any pet animal has the potential for carrying a disease that could be contagious to humans. A disease that is contagious from an animal to a human is called a zoonosis (or zoonotic disease). For example, you might have read about the possibility of green iguanas carrying the potentially dangerous bacterium, Salmonella. Let's separate fact from fiction and learn about the zoonotic diseases of reptiles and amphibians, and how to prevent herp-related illness in your family.

To minimize the risk of contracting a disease from a pet reptile or amphibian, always purchase domestically bred and raised animals only. The reasons for this are simple: captive herps bred in this country are usually housed and bred in much cleaner conditions than their wild counterparts (which means less risk of parasites or organisms that might cause disease). They are subject to much less stress and crowding than wild-caught herps are, and domestics are not subject to poor conditions (such as incorrect temperature, crowding, poor diet) that may occur during importation to this country.

In addition to always purchasing domestic stock, choose herps that appear healthy, and have new pets examined by a herp vet. If your vet recommends testing, be sure to have those performed.

The risk of contracting a disease from a reptile or amphibian is generally small, as long as owners practice good hygiene. However, people with a suppressed immune system are more at risk than the general population. For example, children under 10 and the elderly are considered to be at higher risk. People with chronic disease that compromises the immune system are also at greater risk, as are people with AIDS. People who have had organ transplants, and those taking immunosuppressive drugs (such as prednisone or dexamethasone) are also more susceptible to infection.

Bacterial Infections

Probably the most recognized zoonotic disease is Salmonellosis, caused by the Salmonella bacterium. There are over 2000 different strains of the organism, and there is a different one (or several) that can be found in just about every animal species! But any strain (officially called a serotype) can cause disease in any animal, and virtually all serotypes should be considered to be potentially dangerous to animals and humans.

The problems associated with pet reptiles and Salmonella first came to light in 1963, when a pet turtle was implicated in the disease found in a 7-month-old baby. In 1975, the FDA ruled it illegal to sell turtles with a carapace (upper shell) length of less than 4 inches (with exceptions made for educational or scientific institutions and marine turtles). This law was enacted because baby turtles are much more likely to shed Salmonella bacteria and because it was assumed that larger turtles were less likely to be purchased or handled by young children (who are more at risk).

There are several problems associated with this unusual group of bacteria. First, it can be difficult to diagnose. While this bacterium usually inhabits the gastrointestinal tract, it is not always passed in the feces. So, performing one fecal culture isn't always helpful. If the culture does not show the presence of the bacterium, it doesn't mean that the herp doesn't harbor the organism. In other words, a negative culture result does not rule out the disease. Sometimes, multiple cultures may be necessary to diagnose Salmonella. Other diagnostics may be employed to try and diagnose this disease. Another problem is that the Salmonella bacterium isn't like most other bacteria that can simply be treated with a 10-day course of antibiotics. By treating with antibiotics, instead of eradicating the bacterium, it is possible to create an animal that becomes a carrier, able to shed the organism during times of stress. It is impossible to tell if a reptile is harboring Salmonella simply by looking at it.

The best way to deal with the entire issue of Salmonella is to treat each reptile as if it is carrying the bacterium. By taking certain precautions, you can minimize the risk of actually acquiring an infection from a pet herp. Make sure everyone in the family knows that they must wash their hands after handling a herp. Wear gloves and face protection when washing herp cages, supplies and soaking pools. Use a safe disinfectant (ask your vet) frequently and correctly. Supervise young children around reptiles. Never clean reptile equipment or cages in a kitchen or bathroom used by humans. Don't soak herps in tubs, sinks or showers used by humans. Keep herps out of the kitchen and bathroom. Make herp cages simple to clean and disinfect. Keep other pets away from herps. And finally, no matter how much you may care for your pet herp, never kiss it (and make sure that your children know this rule, as well!)

If a herp does scratch or bite a family member, make sure that the wound is scrubbed with plenty of hot, soapy water. Any bite or scratch should be taken very seriously, as there is a potential for infection. A doctor should be consulted for all bites and scratches.

There are other types of bacteria found in reptiles that can also cause disease in humans. One potentially serious organism is called Campylobacter. This bacterium can cause serious gastroenteritis, diarrhea, abdominal cramps, nausea, vomiting and fever.

Other types of bacteria that can be isolated from reptiles can also cause infections in people. One of the most serious diseases is tuberculosis. Infections in humans can be contracted through scratches, bites, during handling an infected reptile and when cleaning the cage of an infected herp.

Occasionally, reptiles can transmit fungal infections or viruses to humans. Many herps harbor large numbers of protozoal organisms, which may infest humans, most commonly the elderly, infants, and those with weak immune systems.

While we may usually associate worms with pet dogs and cats, there are many different types of worm parasites that can infest pet reptiles. By far, the most dangerous are called pentastomid worms. They are found in different species of snakes, crocodiles, turtles and lizards. The adult worms are found in the lungs, windpipe or nasal passages. Infested reptiles can shed millions of pentastomid eggs because the eggs are coughed up by the reptile, swallowed and then passed in the feces. The cage can become contaminated with incredible numbers of eggs. Humans can become infested by ingesting eggs (which are microscopic and cannot be detected by the naked eye). This fact alone should be enough to deter owners from cleaning cages and cage equipment in the kitchen sink!

If a human swallows some pentastomid eggs, they hatch and become larvae. These immature worms then penetrate through the intestines of a human and then go wandering through the bloodstream, to settle in lymph nodes, liver, lungs, or other organs where they become dormant in cysts. The larvae then mature and may break out of the cysts to once again migrate through the human body. Eventually, cysts can become hardened with calcium deposits and the larvae will die. The larvae migrating through the human body can cause varying degrees of inflammation and reaction. Surgery may be necessary to remove larval cysts. Medical treatment of humans with larval cysts is not usually effective.

Mites are external parasites that can infest a variety of reptiles. While most are quite species specific, and can only complete their life cycle on their intended host, they are capable of biting humans.

Ticks are another group of insects that can be found on reptiles. The ticks themselves are not usually dangerous to humans, although they can bite humans and family pets. But ticks can carry several different diseases that can infect humans, such as relapsing fever, western equine encephalitis virus, among others.

This information is not meant to scare herp owners, but to ensure that pet owners understand that it is very important to teach all family members that practicing scrupulous hygiene is very important when it comes to owning herps. It is equally important to find and utilize the knowledge of a qualified herp vet. By having appropriate testing performed by your vet, by washing after handling a herp, and finally by keeping herp cages clean, any risk of disease will be minimized.

Cadeusus
Copyright 2006 Margaret A. Wissman, D.V.M., D.A.B.V.P.
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