Vétérinaires Sans Frontières Suisse (Vets Without Borders Switzerland) published a short booklet a few months ago about diseases that pass from animals to people, known as zoonoses. The booklet, which is very thorough, has proved a great success with the public, for whom these diseases — or rather how contagious they are — often go unrecognised. Here is a brief overview of the topics it covers.
Ringworm (dermatophytosis)
In my view, the most common zoonoses are fungal infections of the skin — in other words, ringworm. These skin fungi (dermatophytes) spread easily, by direct or indirect contact. The lesions are often round, slightly reddened, with flakes or crusts and hair loss. While they cause the animal very little itching, in people they more often bring on a burning or itching sensation. Children, the elderly and anyone with a weakened immune system (chemotherapy, transplant recipients, HIV-positive) are more susceptible. How to identify it, the treatment and the hygiene measures are all set out carefully in the booklet mentioned above.
External parasites (ectoparasites)
Fleas
Fleas are partial to animal blood but, failing that, will also feed on humans. The species most often seen is the cat flea (Ctenocephalides felis). Their bites (clusters of tiny red spots) itch and, in susceptible people, can trigger an allergic reaction to flea bites. Flea prevention on the animal matters, to try to head off this problem. If fleas are already present, remember to treat the surroundings as well as the cat, dog or other animal concerned, since 95% of the problem sits there in the form of eggs and larvae! Although the flea passes on a gastrointestinal worm of the Dipylidium type to carnivores, it is not known to transmit anything to humans beyond this allergy.
Ticks
These arachnids can be every bit as dangerous to animal health as to our own. While the bite itself may cause a local reaction, ticks are feared above all for the diseases they carry. In Switzerland they can transmit, among others, piroplasmosis (or babesiosis) in dogs (and cattle), ehrlichiosis (known in dogs and also in cattle), borreliosis in dogs and humans (in which case it is called Lyme disease) and European tick-borne encephalitis (TBE), which is more common in the north of the country.
Some of these diseases can be avoided by removing the tick promptly. The best method is to grasp the tick delicately and pull gently to draw it out, turning it clockwise as you go. Never pour oil, vinegar or any other product onto the tick, and never pull it out without a twisting motion. Anti-tick products (for animals) also protect effectively when applied correctly and regularly.
Other external parasites
Cheyletiella, so-called duck fleas (cercariae) and harvest mites can also cause redness and itching in animals or people.
Internal parasites (endoparasites)
Toxocara
Gastrointestinal worms of the Toxocara genus live inside the small intestine. The larvae are the greater danger, as they can migrate through the body and cause serious consequences. These worms are found in dogs and cats, mainly in young animals, and can infect humans, especially children. The eggs are very sticky and survive extremely well in the environment. Symptoms range from digestive inflammation to all sorts of problems linked to the possible migration of the larvae (mainly respiratory symptoms). Here again prevention is hugely important and, like treatment, comes down to worming.
Echinococcus multilocularis
The fox tapeworm is found in Switzerland too. An estimated 30% of Swiss foxes are infected with the adult worms, which live in the small intestine. Dogs and cats are also known to harbour this parasite, which makes these animals the definitive hosts. People become infected by swallowing egg segments of the worm (raw wild berries, for instance) and serve as an intermediate host for the development of the echinococcus. While the parasite causes no disease in carnivores, in the human intermediate host it causes a condition called alveolar echinococcosis of the liver (AE): the parasite grows in the liver and can produce “metastases” in other organs. The interval between infection and the first symptoms is 10 to 15 years. In Switzerland, 8 to 10 new cases of AE are recorded each year. Thanks to advances in medicine, the 10-year survival rate is 90% (untreated, the mortality rate is 90%). But not everyone infected goes on to develop AE, so it seems some people are resistant to the disease.
Preventing or treating it in the animal, once again, means giving wormers that are effective against echinococcus on several consecutive days, as well as thoroughly cooking any food that might be infected. Treatment in humans is more involved, calling on surgery and long courses of drug therapy.
Other parasitic diseases
Toxoplasmosis and leishmaniasis (more common in warm to tropical regions) also cause illness in both animals and humans. These diseases have serious consequences and are described in full in the VSF-Suisse booklet.
Other diseases behind zoonoses
Rabies — the subject of a forthcoming tip of the month — tuberculosis, sadly still present around the world, and diseases of farm animals such as BSE (mad cow disease) or anthrax (lately back in the political spotlight) are other serious zoonoses, also explained in the booklet.
The booklet is available from VSF-Suisse, www.vsf-suisse.ch