Zoonosis is a disease that is transmitted from other vertebrate animals to humans directly or through a secondary source such as ticks. Many serious diseases fall into this category such as anthrax, tuberculosis, Ebola and plague. In past articles I have discussed several diseases seen in Vermont such as rabies, Lyme disease and leptospirosis. In this article I will discuss a lesser known but still very important zoonotic disease called larva migrans.
Larva migrans is caused by an unusual migration of a parasite larva. There are three different forms of larva migrans depending on which part of the body is affected. Cutaneous (skin) larva migrans occurs when the worm larvae enter the skin. If the worm larvae migrate through various internal organs of the host, it is called visceral larva migrans. Sometimes the worm larvae may invade the eye of the host. This is called ocular larva migrans. Larva migrans infection primarily occurs in children aged 1-4 years but can occur at any age. During 2006 there were twenty-two cases of cutaneous larva migrans diagnosed in Miami, Florida. After an investigation by the health department it was determined that the infections occurred in a sandbox at a daycare facility. Amazingly, blood tests for animal parasite antigens in the United States have shown that the infection rate in children varies from 2-10%. This doesn’t mean that these children became ill, but it does mean that at some point this many kids ingested a parasite egg.
Larva migrans is caused by animal parasite eggs hatching in or on humans. These parasites can’t reproduce in humans, so they cause damage as they wander throughout the body. Feline and canine hookworms and roundworms are the most common cause of human disease although there is a raccoon parasite that occasionally causes disease. Prevention is key. Worm all your pets at least biannually and have a fecal exam done annually. If you are giving heartworm medication to your pet then that will take care of it. If you’re not, you should be. Since kids are most commonly affected it is also very important to make sure they wash their hands after playing in the dirt, sandbox or anywhere else that a cat or dog may have defecated. If you have a sandbox make sure it is covered when not in use. Gardeners: Wear gloves and/or wash your hands thoroughly after gardening. Also, keep in mind that when your dog does his business on the bike path or in the park it’s not just an eyesore, it’s a potential infection. Clean it up!
Finally, there are many more parasites that can cause larva migrans which is why it is one of the most common tropical diseases. If you’re traveling keep your hands clean, eat only cooked food and be careful. Although the disease is not common, when it occurs it can be devastating. Remember, prevention is the key.