Echinococcosis

Synonyms: cystic echinococcosis, hydatid disease

What is it?

Cystic echinococcosis or hydatid disease is caused by the larval stage of a tiny cousin of the Taenia tapeworms, Echinococcus granulosus. Like other tapeworms, echinococcus has two hosts, a definite host in which the adult worm lives and an intermediate host, in which the immature cyst lives. Adult worms measure a few mm and live in the intestine of dogs, which are thus the definitive host. The larval stage occurs mainly in herbivores and in humans, the intermediate hosts. The larval cysts are found mostly in the liver and the lungs and can be large, sometimes weighing more than a kg. The transmission to herbivores and humans is assured by the eggs passed with dogs’ stools and accumulating in the environment, particularly grass or vegetables. Dogs become infected when feeding on organs containing cysts.

Simplified text: Echinococcosis Disease Card, OIE (English, French and Spanish); Echinococcus granulosis, Wikipedia
Simplified video: Cystic echinococcosis - Kist hidatik (11'04; Turkish with English subtitles); Echinococcosis in Argentina (13'46; Spanish); Estudio demografico sobre la tenencia responsable de mascotas y prevencion de la hidatidosis (Chilean video) (4'41; Spanish)
Technical text: Echinococcosis CDC (English only); Zoonoses and communicable diseases common to man and animals, vol 3 p 184 (English only)

How to recognize it

In humans, hydatid cysts caused by the larval stage of the parasite, can be localized in various organs. The symptoms will depend on the localization. The most common localizations are the liver (hepatic cysts) and the lungs (pulmonary cysts). The cysts grow slowly but their weight can reach several kg after several years, causing compressions and failure of the compressed tissues. Swollen abdomens are observed in case of large hepatic cysts. The following symptoms may be observed in case of small or large hepatic cysts: abdominal pain, abnormal abdominal tenderness, jaundice and fever. Pulmonary cysts may cause coughing, shortness of breath and chest pain. When cysts rupture, after a trauma for instance, a severe and acute reaction generally occurs (anaphylactic shock): high fever, itching, fluid retention (edema) difficulty in breathing and abnormally loud breathing (stridor). The presence of hydatid cysts may be confirmed using a serological test or medical imaging techniques.

Simplified text: Echinococcosis CDC (English only)
Simplified video: Cystic echinococcosis - Kist hidatik (11'04; Turkish with English subtitles); Estudio demografico sobre la tenencia responsable de mascotas y prevencion de la hidatidosis (Chilean video) (4'41; Spanish)
Technical text: Echinococcosis CDC (English only); WHO/OIE Joint publication p20 (English only); Zoonoses and communicable diseases common to man and animals, vol 3 p 184 (English only)
Technical video: Hepatic Echinococcus Cyst Ultrasound, CT Scan images, Sonoworld (English only)

In animals, no symptoms are observed in live animals and serological and diagnostic imaging methods do not perform well. Cysts in herbivores are mostly detected when animals are slaughtered. They resemble water balls of various sizes ranging from a few mm to a few cm in diameter. They are mostly found in the liver and in the lungs. They may be confounded with the cysts of another parasite, Taenia hydatigena. Eggs of this parasite are also transmitted by dogs to herbivores but not to humans. Cysts caused by T. hydatigena are more commonly observed on the peritoneum (lining of the abdominal cavity).

Simplified video: Cystic echinococcosis - Kist hidatik (11'04; Turkish with English subtitles); Images of cattle liver with hydatic cysts (1'21; no sound; French titles)
Technical text: Echinococcosis OIE terrestrial manual (English only); WHO/OIE Joint publication p20 (English only)

Infected dogs cannot be easily identified. It is dangerous to look for worms in dogs’ intestines given the infective and zoonotic character of eggs.

Technical text: WHO/OIE Joint publication p20 (English only); Zoonoses and communicable diseases common to man and animals, vol 3 p 184 (English only)

How to control it

Cystic echinococcosis in humans is closely associated with extensive sheep breeding. A cooler and humid climate for at least part of the year seems necessary for the survival and accumulation of eggs in the environment. Dog populations should be controlled. Waste should be properly managed to reduce the abundance of stray dogs. More specifically, abattoirs and slaughter slabs should have access to appropriate disposal facilities and make full use of them. Contamination of surface water by infected dogs should be avoided and, if necessary, surface water should be adequately treated before it is used by humans.

General considerations on dog management

In Africa, most stray dogs are associated with a human community that provides them with food. Some apparently stray dogs are actually owned, but left to roam freely. Some stray dogs return to the wild (feral dogs) but struggle to reproduce. As a consequence, most feral dogs come from owned or stray dog populations. Controlling births among owned and stray dog populations would, therefore, have an impact on all dog populations, including feral dogs.

Unfortunately, no easy and cheap contraceptive methods are available. Castration of males is not useful because one single male can fertilize many females. Spaying female dogs is recommended but more difficult to implement. Alternatively, euthanasia of pups could be recommended but this should be done in a humane way, probably requiring veterinary expertise.

Killing dogs has been demonstrated to be counterproductive in several situations, because the killed stray and feral dogs are quickly replaced by new dogs from outside the community, with the attendant risk of bringing in diseases (e.g. rabies). The dog capture, sterilization, vaccination, treatment and release method is recommended but, again, is very demanding for veterinary services.

Finally, stray dogs mostly feed on waste. Improved waste management is likely to result in reduced stray dog populations.

Simplified text: Guidelines from World Society for the Protection of Animals (English only)
Simplified video: Estudio demografico sobre la tenencia responsable de mascotas y prevencion de la hidatidosis (Chilean video) (4'41; Spanish); FAO film on rabies control (21'00; English only); Rabies control in Liberia (4'18; English only)
Technical text: OIE terrestrial manual code (English only); WHO guidelines for dog management (1990; English only); WHO report on echinococcosis control (English only)

Dogs play a major role in the spreading of eggs in the environment. Infections in dogs can be controlled using the following methods:

When slaughtering herbivores, infected organs should be identified and destroyed
Offal containing cysts should never be given to dogs
Dog populations should be controlled: female dogs may be spayed and surplus puppies should be euthanized humanely
Communal and individually owned dogs should be regularly treated with an appropriate drug (1 – 4 times a year depending on the incidence of the parasite)

Humans become infected when they have direct or indirect contact with dogs and/or dogs’ stools (faeces). Eggs can be found in great numbers on infected dogs’ fur and in their mouths. Eggs may also contaminate vegetables and drinking water. For these reasons:

Close contact with untreated dogs should be avoided
Potentially infected dogs should not be allowed inside houses and vegetable gardens
Hands should be washed after interacting with dogs or working with potentially contaminated soil
Vegetables should be thoroughly washed or cooked before consumption
Surface water, which may be contaminated far away upstream, should be boiled
However, butchering or consuming contaminated mutton represents no direct risk to humans, (in contrast to dogs)

Herbivores become infected when grazing on ground that has been contaminated with eggs shed by dogs. Most herbivores are receptive to the hydatid cyst but sheep play the most important role in the transmission of human cystic echinococcosis. Controlling the infection in these animals should reduce the risk of transmission to dogs. It will also reduce the economic losses from having to condemn contaminated offal as unfit for consumption. For these reasons:

Potentially infected dogs should not be allowed in grazing areas
An experimental vaccine has been shown to protect sheep against the parasite
Use of praziquantel or albendazole in herbivores: herbivores could be treated with anthelmintics before they are slaughtered to reduce the risk of transmission to dogs. The recommended waiting interval between this treatment and the slaughter of the treated animal should be strictly adhered to.

Cystic echinococcosis is only pathogenic in humans. Surgery is the only option for curing human patients. Different treatment protocols exist. In the past protocols were very invasive and debilitating. Currently, the Puncture, Aspiration, Injection, Re-aspiration (PAIR) method is an effective and safe treatment. Surgery may be followed by an albendazole treatment (anthelmintic) to avoid relapses.

Popularized illustrations: Do not give offal to dogs (French only); Prevention in Morocco 1 (Arabic only); Prevention in Morocco 2 (Arabic only); Prevention in Morocco 3 (French only)
Popularized text: Chlef: l'aid el-adha et le kyste hydatique (Algerian publication; French only); Eloigner le spectre du kyste hydatique (Algerian publication; French only); La prohylaxie du kyste hydatique est importante en cette pÃ©riode (Algerian publication; French only); Mise en garde contre la propagation du kyste hydatique (Algerian publication; French only)
Simplified text: Echinococcosis CDC (English only); Publication of the Moroccan vet school (French only)
Simplified video: Cystic echinococcosis - Kist hidatik (11'04; Turkish with English subtitles); Echinococcosis in Argentina (13'46; Spanish); Estudio demografico sobre la tenencia responsable de mascotas y prevencion de la hidatidosis (Chilean video) (4'41; Spanish); Hydatidosis prevention in Chili (5'09; Spanish only)
Technical text: Echinococcosis CDC (English only); WHO publication on PAIR (English only); WHO publication on chemotherapy and vaccination of animals (p91; English); WHO publication on control straregies (p215; English); WHO publication on human treatment (p60; English); WHO/OIE Joint publication p20 (English only); Zoonoses and communicable diseases common to man and animals, vol 3 p 184 (English only)
Technical video: Case study of a 20 year old woman, surgery (9'33; English only); Case study of a 62 year old person, surgery (3'25; English only)

Cultural and geographical specificities

Cystic echinococcosis is closely associated with sheep rearing, especially where dogs are used for herding. In Africa it is particularly linked with mountainous landscapes in northern and eastern Africa and with pastoralist and agro-pastoralist communities in those regions. .

Pastoralist communities

The incidence of the disease is particularly high in some Turkana pastoralist communities, but high incidences have also been found in other pastoralist communities in eastern Africa and the Horn of Africa. Specific messages for pastoralists should consider the very close contact they have with dogs. Dogs living in very close contact with people (contacts with coat and tongue or with contaminated soil and water) should be regularly treated (1 – 4 times a year) with praziquantel.

To reduce the risk of dog infection, people should understand that cysts should be killed before they are given to dogs. People do have the capacity to identify the cysts. They must find a genuinely effective way of disposing them without infecting the dogs (burying, cooking or burning). Destruction of the infected organs only would already be a useful measure.

No links.

Communities in northern Africa and the Sahel region

The disposal of infected organs should be improved. At abattoir and slaughter slab level, the (illegal) habit of disposing these organs outside these facilities, where they are accessible to wild and domestic animals, should stop. Since a very high proportion of sheep are slaughtered in homes, public awareness campaigns need to focus on the danger of feeding raw offal to dogs and on practical ways of disposing of it safely.

Waste management, including in tourist areas (mountains and ski stations), should be improved so as to reduce the abundance of stray dogs and the contamination of the environment and surface water.

Public awareness should provide basic information about the disease to communities which are at risk. This needs to explain signs and symptoms in people. The ways in which cystic echinococcosis can be transmitted and the role of dogs needs to be explained.

In Arabic and Berber communities, public awareness could build on the Muslim hadiths in relation to dogs, which recommend low dog populations and reduced contacts with dogs. Unfortunately these hadiths also tend to make dogs living close to human communities less easy to handle for veterinary interventions (treatment, sterilization or euthanasia) because they are not used to being manipulated.

Popularized illustrations: Prevention in Morocco 1 (Arabic only); Prevention in Morocco 2 (Arabic only); Prevention in Morocco 3 (French only)
Popularized text: Chlef: l'aid el-adha et le kyste hydatique (Algerian publication; French only); Eloigner le spectre du kyste hydatique (Algerian publication; French only); La prohylaxie du kyste hydatique est importante en cette pÃ©riode (Algerian publication; French only); Mise en garde contre la propagation du kyste hydatique (Algerian publication; French only)

Mixed farming communities in more humid regions

The incidence of cystic echinococcosis in humans in other African settings is too low to justify specific messages.