Clever parasite – Fox tapeworms on the advance
Pets can pick up the parasites
Nowadays, dogs and cats are more than just pets – they are members of the family and are treated with love. Although psychologists welcome this trend, because cuddling and caressing helps us to release tensions, parasitologists have mixed feelings about this physical contact.
After all, Rover and Kitty sometimes bring back to the living room dangerous souvenirs from their travels outside: the eggs of the small fox tapeworm. These eggs can cause echinococcosis if they find their way into the human digestive tract, a disease that is incurable and sometimes fatal.
Foxes are the main carriers
Foxes are currently multiplying unrestrained in Germany. Experts estimate that their population has quadrupled within the last 15 years. The reasons are that fox fur is out of fashion, and rabies, which used to wipe out innumerable animals, can be successfully combated today.
Both factors are impacting on the spread of the fox tapeworm. "The infestation rate has risen drastically in many regions since about 1990. Furthermore, the parasite is cropping up today in regions where it used to be unknown," says an information brochure published by the German Hunting Association, which goes on to say that the danger of contact between tapeworms and humans is growing as foxes increasingly adapt to life in our towns and villages.
Small worms, big impact
The small fox tapeworm is very common in the Northern Hemisphere. It lives both in Arctic regions, where the Arctic fox is the definitive host, and in Northern Italy and Japan. In Germany, too, it knows no frontiers.
"From region to region, the percentage of infected foxes ranges from just a few individuals to up to seventy percent," says Prof. Franz J. Conraths, Director of the Institute of Epidemiology at the Federal Research Institute for Animal Health in Wusterhausen, Germany. Foxes are the definitive hosts here. In other words, the only 4mm-long tapeworm with its four to five segments develops in their intestines. Its last segment contains about 400 mature eggs, which get into the open via the feces onto plants or the ground.
When the eggs find their way into the digestive tract of an intermediate host – in most cases a field mouse or a vole – small larvae hatch there after a while. They penetrate the intestinal wall and travel with the bloodstream to the liver, where a new generation of tapeworms grows. This development considerably weakens the rodent, so that the mouse becomes easy prey for a fox – or a dog or cat – and the tapeworm's next life cycle begins.
The first symptoms are a long time in coming
This development phase is basically the same in humans. The only difference from the rodent is that the development of the larvae in the liver can take up to 15 years. If unnoticed, the larvae start proliferating like a tumor. After a long time, the first symptoms, e.g. jaundice, appear, but by the time the disease has not only destroyed large sections of the liver, it has also infested other organs. A special chemotherapy can help, but it cannot cure the disease and has to be repeated for the rest of the patient's life.
Risk of infection seven times greater than 20 years ago
The Robert Koch Institute registered 16 new cases in 2006. "Overall, the risk of human infection today is seven times higher than 20 years ago," says Dr. Andreas König of the Department of Game Biology and Game Management at the Weihenstephan Center of Life and Food Science at the Technical University of Munich. He goes on to say that preventive measures to stop the spread of the tapeworm are therefore all the more important.
The best protection is to have pets regularly wormed
One of the most effective ways to prevent the risk of contracting echinococcosis is to have your four-legged family members regularly wormed. Treating all your animals with the active ingredient Praziquantel from Bayer every three months considerably reduces the risk of transmission. Animal lovers who want to play completely safe should submit their pets to prophylactic treatment once a month; this is because the tapeworm lays its 400 eggs after spending a month inside its host. This procedure is recommended by Prof. Heinz Mehlhorn, parasitologist at the University of Düsseldorf: "Fox tapeworms can be effectively and easily eliminated in this way."
Advice for patients
Every body reacts differently to medicines. Therefore it is impossible to tell which medicine works best for you. Please consult your veterinary.
