Tapeworms (Taenia pisiformis, Dipylidium canium, Enchinococcus granulosus, and Echinococcus multilocularis) are found in the intestine of dogs and are a major hygienic concern because they are transmissible to people. Dog-rabbit tapeworms (T. pisiformis) have a life cycle that starts with them living in the small intestines of wild foxes, coyotes, and wolves where they produce eggs that are shed in the feces and subsequently contaminate the local environment. Rabbits then become infected by ingesting these eggs which then form hundreds or even thousands of "hydatid cysts" in the tissues. When dogs or their wild cousins eat these rabbits they can be infected with hundreds to thousands of adults. These adults latch onto the wall of the intestines and after about a month, start shedding eggs. These eggs are then immediately infective to other animals, including people. To complicate matters further, these tapeworm eggs can remain infective in the environment for several months.

Infected dogs may seem clinically normal while shedding large numbers of infective eggs. The eggs are generally first seen in your dog's feces or sticking to the hair around your dog's rear. These specialized muscular egg cases are actually segments of the worm that are full of eggs and they look like a small, flattened, grain of white rice that moves. As the egg case wiggles around it is spreading thousands of tapeworm eggs which are too small for the naked-eye to see.

Adult tapeworms appear to cause very few clinical problems in dogs. However, this is the real point of concern since infected people are not as lucky. Alveolar hydatid disease in humans, caused by Echinococcus multilocularis, is a very serious infection that usually involves the liver. Early in the course of the infection, patients may be misdiagnosed with other liver ailments. Involvement of other tissues, including the lungs and brain can also occur. Since over 50% of people with alveolar hydatid disease die, this is considered the most lethal worm infection that people get. It is therefore important for all dogs and cats in high-risk areas be screened for tapeworm infection. This is more difficult than it sounds since infection with Echinococcus eggs can not be readily differentiated from the more common tapeworms which do not affect people. Veterinarians finding tapeworm eggs on fecal exams usually closely examine pets for the rice-like grains known as proglottids which are found with common tapeworms but not the lethal variety. Occasionally more dramatic methods are necessary to try to recover worms from suspect pets. A more convenient blood test is available to diagnose infection in people and hopefully similar tests will soon become suitable for pets.

The best defense is increased public awareness of this condition. Personal protection and hygiene are important, especially to those individuals that may contact feces from potentially-infected pets. Children are particularly at risk. Mulch that contains feces from dogs, cats, wolves or foxes should not be used on gardens. Beagles should be discouraged from consuming rabbits or any other type of wild rodent.

Fortunately for pets, there are medicines that are safe and very effective for treatment. People are not as lucky and surgery still remains the preferred treatment.

In conclusion, Echinococcus multilocularis, may cause a mild problem in pets but if people get infected, the results can be fatal. In order to minimize the risk of human infection the public must increase its awareness of the potential complications that are associated with the parasites.


 

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