Disease: Other diseases

Fox tapeworm

The fox tapeworm (scientific name Echinococcus multilocularis) causes a serious or even fatal liver disease in humans (alveolar echinococcosis). The parasite is found in much of the northern hemisphere, although the British Isles are fox tapeworm free. The disease requires an intermediate host (rodents) and a definitive host (most carnivores, including foxes). Infection with the fox tapeworm causes little or no harm to the definitive host. Eggs are shed in the host faeces and people or pets can be infected though contact with faeces.

Head and shoulders of a coyote with its ears drawn backwords
In the USA, coyotes are locally important for the spread of fox tapeworm

In most areas, foxes are responsible for the spread and increased prevalence of this tapeworm. In North America, coyotes and arctic foxes can be locally important. Direct transmission from foxes to humans is unlikely, but high prevalence in foxes is linked to high prevalence in rodents, which are the intermediate hosts. This creates a high infective pressure, and so domestic pets are more likely to be infected. Domestic pets are most likely to transmit infection to humans.

Fox populations across Europe are increasing and this has been linked to the increased spread of the fox tapeworm, and in some areas the increased number of human infections. There are a number of ways to control fox tapeworm infection in foxes. Several studies have used anti-helminthic (anti-parasite) drugs to decrease prevalence locally, but as yet no wide scale solution has been devised. However, as with the spread of rabies, culling is unlikely to be effective and, as it disrupts social dynamics of fox groups causing individuals to move, might even be counter-productive by facilitating the disease spread.

TopToxocariasis

Toxocara canis is a roundworm that can be found in both dogs and foxes. Research using genetic data from worms found in dogs and foxes has shown that they belong to the same population, and so Toxocara canis can be transmitted between dogs and foxes. Humans can be infected through their pet dog. Pet cats harbour a different species of worm, Toxocara cati, which can also infect humans.

Young children are particularly at risk because they tend to explore the world around them with their hands and mouths; infection with toxocariasis occurs through ingestion of material contaminated with the parasite's eggs, such as dog and cat faeces or cat litter.

TopCanine heartworm

Dog sitting in a armchair
Most parasites are transmissible between foxes and domestic dogs

There are several kinds of heartworms widespread in different parts of the world. For instance, in North America Dirofilaria immitis is known as heartworm. In the UK, where Dirofilaria immitis is absent, Angiostrongylus vasorum is known as heartworm.

Dirofilaria immitis is a nematode (roundworm) commonly found in domestic and wild canids in Africa, Asia, Australia, South America, southern Europe and the USA but is absent in the British Isles, where it cannot survive because of the cool climate. It is transmitted by several species of mosquitoes and the adult worms live in the heart and lung arteries. It is common in domestic dogs and less common in cats, ferrets and a variety of other wild carnivores. In dogs, light infestations are easily treated but heavy infestations can be fatal. The disease is easily treated in humans.

Angiostrongylus vasorum is also a nematode (parasitic worm) commonly found in domestic dogs, foxes and other canids in North and South America, southern England and in many parts of Europe. It was first discovered in France and, for this reason, is commonly called French heartworm or simply heartworm. Although it is called heartworm, it actually lives in the lung arteries of its definitive host, such as foxes and dogs. Disease transmission requires an intermediate host (slugs and snails) and a definitive host (foxes and dogs), although frogs that have eaten infected slugs and snails have also been implicated in the transmission to dogs and, presumably, foxes. The disease has severe consequences for the infected animal, including heart failure and death. The disease is not easily treated in dogs and, since foxes have been implicated as a reservoir, this is a matter of concern. However, regular de-worming pets is effective in preventing all diseases due to nematodes (roundworms).

Question & Answer

TopWhat is the fox tapeworm?

It is a parasite belonging to the Cestoda (flat, parasitic worms) that lives in the intestine of cats, dogs and foxes.

TopWhere is the fox tapeworm found?

The fox tapeworm is widespread throughout most of the northern hemisphere including Asia, Europe and North America. The British Isles are free of the fox tapeworm.

TopWhat can I do to avoid contracting the fox tapeworm?

TopWhat is toxocariasis?

Toxocariasis is caused by Toxocara canis, a nematode (roundworm) that lives in the small intestine of dogs and wild canids.

TopWhere is the toxocariasis found?

Toxocariasis is found worldwide and the proportion of the human population infected (link to an external website) varies from country to country.

TopWhat can I do to avoid contracting toxocariasis?

TopWhat is the canine heartworm?

In North America Dirofilaria immitis is known as heartworm. In Britain where Dirofilaria immitis is absent, Angiostrongylus vasorum is known instead as heartworm or also French heartworm. Both worms are nematodes, a kind of parasitic roundworm.

TopWhere is canine heartworm found?

Dirofilaria immitis is commonly found in domestic and wild canids in Africa, Asia, Australia, South America, southern Europe and the USA but is absent from Britain. Angiostrongylus vasorum is instead found in domestic dogs, foxes and other canids in South and North America, southern England and in many parts of Europe.

TopWhat can I do to prevent my dog from contracting canine heartworm?

References

  • Bellamy, R. & Salmon, R. (1999) Risk of importation of diseases exotic to Great Britain following the relation of quarantine regulations. Quarterly Journal of Medicine 92, 683-687.
  • Deplazes, P., Hegglin, D., Gloor, S. & Romig, T. (2004) Wilderness in the city: the urbanization of Echinoccocus multilocularis. Trends in Parasitology 20, 77-84.
  • Ferasin, L. (2004) Disease risks for the travelling pet: heartworm disease. In Practice 26, 350-357.
  • Morgan, E.R., Shaw, S.E., Brennan, S.F., De Waal, T., Jones, B.R. & Mulcahy, G. (2005) Angiostrongylus vasorum: a real heartbreaker. Trends in Parasitology 21, 49-51.
  • Ridyard, A. (2005) Heartworm and lungworm in dogs and cats in the UK. In Practice 27, 147-153.
  • Smith, G.C., Gangadharan, B., Taylor, Z.,Laurenson, M.K., Bradshaw, H., Hide, G., Hughes, J.M., Dinkel, A., Romige, T. & Craig, P.S. (2003) Prevalence of zoonotic important parasites in the red fox (Vulpes vulpes) in Great Britain. Veterinary Parasitology 118, 133142.