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Diseases

Like other wild mammals, foxes are susceptible to a variety of parasites, infections and diseases. Most prominent are fleas, ticks, worms and in some cases scabies. There hasn't been done a lot of research on this point, because these kinds of diseases don't have much impact on a normal-sized fox population. Moreover, foxes that are weakened by a disease retire to the most inaccessible places to die there unnoticed. Two important diseases that are dangerous to men however have already been investigated or are at this moment being investigated: rabies and tapeworms (echinococcus multilocularis).

     Rabies

Rabies is a viral disease that is mainly the result of bite wounds. As soon as a fox is infected with rabies, the virus will travel up the nerves of the victim to the brain. The period of incubation (the time the virus needs to travel up to the brain) takes two to four weeks. During this period of incubation, there is no development of symptoms and no risk of infection. As soon as the brain is infected however, the virus will pass down the nerves to all the organs of the body. Some virus particles will travel to the salivary glands. At this stage, the animal becomes infective and the symptoms of the disease start to show: at first the animal becomes apathetic, then it becomes irritable and it tries to bite objects. Finally a paralysis develops and death is inevitable. The virus can only be prevented if vaccination is arranged soon after the bite of the infected animal. An infected fox will be more active during the daytime and will be less shy. The period between the infection of the brain and death is three to five days for foxes. During this period, a fox can infect other foxes but also people and other mammals. These infections are mainly caused by bite wounds: the virus is introduced from the saliva of the infected animal. The carcass of a dead infected fox still remains a potential source of infection to animals that prey on it. All warm-blooded animals (people too) are susceptible to this disease, but this susceptibility is different for every species. Foxes have a high susceptibility to rabies and they are also the main carriers of this disease in Europe. An infected fox will attack people only very exceptionally, but it's not so difficult to imagine a fox infecting cattle or domestic animals. In their turn, they can infect human beings.

The vaccination of domestic animals and high-risk groups (foresters, hunters,...) is one of the means to prevent (the spread of) rabies. The best method however is to get down to the very root of the problem. Up to ten years ago, this method consisted of shooting as many foxes as possible. The government supported large campaigns of extermination. These campaigns caused a strong decline of the fox in Flanders, in some Flemish provinces even the fox became a rarity or disappeared completely (east and west of Flanders), although there had never been found one infected fox on Flemish territory. In woodlands and other regions with a lot of greenery and big woods (like in the Walloon provinces), people have never succeeded in exterminating the fox completely. The purpose of these campaigns of extermination was to thin out the fox population so that the sick foxes infected as little other foxes as possible before their death in order to stop the spread of the virus. But foxes don't need much time to recover. More than half of a strongly thinned out fox population can be re-established within one year. Moreover, foxes are territorial animals (each animal has its own territory that it defends against intruders) and making certain territories fox-free is of no use because soon foxes from neighbouring territories will fill up these territories. If some of these foxes turn out to be infected, that would only speed up the spread of rabies. 
Because of the bad effects of these campaigns of extermination, researchers had to look for new and efficient methods. What if they could render foxes themselves immune to rabies? At the end of the eighties, researches introduced the method of oral vaccination. This method allowed them to put the bait containing the vaccine against rabies in strategic places: in the immediate neighbourhood of foxes (holes, edges of woods, tracks). With this method at least 60% of the foxes could be immunized and after a few years, rabies had been cut back so drastically that the campaign could be regarded as a success. The fox can now function normally again in nature and that's good because the method of oral vaccination requires a well-balanced fox population. For the first time, scientists are able to keep rabies out of Belgium and restrain local outbursts of the disease in no time. When you see a poster at the entrance of a forest or nature reserve, like the photo on the right, you can be sure that the method of oral vaccination is being used in that area to announce the fight against rabies.

 

     Tapeworms (echinococcus multilocularis)

A tapeworm is a parasite of a few millimetre in size and lives in the intestine of foxes as a kind of a grown-up parasite. The fox is the final host or the primary host (also dogs and to a lesser degree cats can get infected being the final host). The eggs of the tapeworm come out together with the excrements and after that they are accidentally eaten by f.e. a vole or other mice. These mice function as intermediate hosts and the egg inside the mice's body develops into a larva. If a fox eats an infected mouse, the larva automatically ends up in the intestine of the fox and develops into a grown-up tapeworm. Although this parasite is practically harmless to the final host, i.c. the fox, it is fatal to the intermediate host. The larva can develop into a cyst, spread itself all over the organ (usually the liver) and finally destroy it, resulting in the death of the intermediate host. Although human beings are no appropriate intermediate hosts, the same thing can happen to them if they consume the eggs of a dead fox in one way or another. This is a frightening phenomenon, but at the same time the chance of infection for human beings is -in normal conditions- practically zero. The tapeworm has probably been found for a number of years in the Walloon provinces in Belgium, in the southwest of Flanders and in the north of the province of Antwerp, but nobody in these regions has been infected so far. If you take the following basic precautions when entering a fox's territory, you have absolutely nothing to worry about: never touch dead or living foxes and their excrements, stay out of fox holes, don't eat unwashed forest fruit that grows 70 centimetre above the ground, rinse off raw vegetables before you eat them and regularly (three-monthly) worm pets that often stay outside. Nevertheless there is a need for accurate research. At this very moment, the RUCA is carrying out a research into the tapeworm. On the basis of the results of this (and other) research(es), appropriate measures will be taken. In the meantime, the best thing to do is to leave foxes alone. Drastic interventions in fox populations will only cause instability, which could stimulate the spread of the tapeworm (the same thing can happen in case of a massive shooting off of foxes carrying rabies, see photo below). Because of the extremely small risk of infection in normal conditions, and because of the fact that the fox plays an important role in our natural environment, it is just a matter of taking all these things into account when you enter a nature reserve.

Hans Schockaert