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Zoonoses: Hydatid disease (Echinococcosis)

Description

Hydatid disease is caused by infection of humans with the larval stage of the dog tape worm, Echinococcus granulosus, acquired by ingestion of tapeworm eggs. It is maintained via a herbivore (mainly sheep) to dog cycle in which, occasionally, humans (rather than grazing animals) are infected by tapeworm eggs excreted in the faeces of infected dogs.

Human health

Echinococcus eggs can be picked up from unwashed fruit and vegetables if they inadvertently become contaminated by dog faeces containing  Echinococcus granulosus eggs.  You should always wash fruit and vegetables before eating to reduce the risk from a number of potentially harmful infections. Observing good kitchen practices such as washing and drying your hands before and after handling food, and to clean kitchen equipment and surfaces thoroughly before and after use will also help minimise risk.

Further information regarding human health is available on the Health Protection Agency’s website.

Hydatid disease in sheep

There are no specific signs of hydatid disease in sheep. There may be a slight loss in production of up to 5% but this would not be diagnostic for hydatid disease. Hydatid infection may be detected at slaughter or at post mortem examination. Hydatid cysts can be recognised as visible cysts at meat inspection and are generally identified in the liver and lungs. On occasion the cysts can be located in other tissues including the spleen, kidney, bone marrow or brain. Visible cysts are more commonly identified during the post mortem inspection of older animals.

Hydatid diseasein dogs

Dogs can pick up this infection if they are fed raw sheep  carcass meat and offal. Dogs that are allowed to roam may come in to contact with dead  sheep and pick up hydatid tapeworms from scavenging  their tissues. It has been suggested that the Border Collie is especially susceptible to infestation with Echinococcus, but this may just reflect the level of exposure of some members of this breed, as Border Collies are often kept on sheep farms.

Dog owners should ensure that only cooked food is fed, that dogs do not get access to sheep carcasses and offal and that they are not allowed to roam, especially out of sight. Dogs should be regularly wormed with an appropriate wormer. Owners should consult their veterinary surgeon who will assess the individual dog’s risk of contracting Echinococcus and advise on an appropriate type of wormer and frequency of dosing according to their risk assessment.

Dog owners should discuss worming needs with their vet who will carry out a risk assessment based on the particular needs of the dog. Treatments at intervals recommended by your vet will ensure that at-risk dogs are prevented from passing on this infection.

If an abattoir or VLA report identifys hydatid cysts in the carcases of sheep or other livestock which originate from your farm, the appropriate action is to ensure all farm dogs are regularly and appropriately wormed to ensure they do not infect further flock or herd members. All the other measures described above for any dog owner should also be considered to help minimise the risk of further herbivores (or people) becoming infected.

Preventing the spread of hydatid disease

The incidence of hydatid disease can be reduced if the following are adhered to:

  • Feed dogs with cooked dog foods
  • Worm dogs at the frequency suggested by your vet with an appropriate wormer
  • Clear up your dog’s faeces and dispose appropriately
  • Do not allow dogs to roam
  • Closely control dogs whilst out walking
  • Do not allow dogs to lick faces
  • Wash hands after handling dogs or clearing up their faeces and before and after handling any food
  • Wash all fruit and vegetables before eating or cooking

Hydatid disease in Wales

Why is hydatid disease more commonly found in Wales?

It is not confined to Wales but the occurrence in England and Scotland is at a much lower rate. The higher level of infection is thought to be due to the high density of sheep and the extensive farm management systems of hill farming. Numbers of sheep die on high grazing and will be found by straying dogs before the farmer can remove them.

An increase in prevalence of the Echinococcus tapeworm in  dogs in Wales has prompted a Welsh Assembly Government campaign asking dog owners to speak to their vet about worming. Hydatid disease is caused by this tapeworm and can be picked up by humans if they come in to contact with infected dog faeces. It is on the increase in certain parts of Wales and is more likely to occur when a dog has been fed or allowed to scavenge on infected sheep carcasses.

Why have English GPs, vets and agricultural merchants, bordering Wales, been approached?

The infection rate in dogs in Wales has been steadily increasing in the last few years and this increases the risk of humans contracting hydatid disease. There is a possibility that English counties bordering Wales may also be at risk  of increased levels of this disease and the parasite may also pose a risk to the human population. We have sent the same information that was sent to GPs and Veterinary Practices in Wales to raise awareness of this issue and the initiative run in Wales. (It is a matter of protocol that the letter to GPs, vets and agricultural merchants was sent from Chief Medical Officers and Chief Veterinary Officers in England and Wales).

Further information on Hydatid disease in Wales including a questions and answers page can be found on the Welsh Assembly Government website.

References

Buishi I, Walters T, Guildea Z, Craig P, Palmer S. Reemergence of canine Echinococcus granulosus infection, Wales. Emerg Infect Dis [serial on the Internet]. 2005 Apr [cited October 2006]. Available from the Centers for Disease Control and Prevention website.

Palmer SR, Biffin AHB, Craig PS, Walters TMH. Control of hydatid disease in Wales. BMJ 1996: 312; 674-675.

Further information

 

Page published: 13 December 2007

Department for Environment, Food and Rural Affairs