Bovis ISSN 2398-2993

Echinococcus granulosus and ortleppi

Synonym(s): hydatidosis, dwarf dog tapeworm, E. granulosus

Contributor(s): Rob Kelly , Johannes Charlier

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Introduction

Classification

Taxonomy

  • Class: Cestoda.
  • Family: Taeniidae.
  • Genus: Echinococcus.
  • Species: E. granulosus and E. ortleppi.
    • E. ortleppi has recently been defined as a separate species to E. granulosus.
    • Species differences will be stated where appropriate.
    • This article focuses on bovine infections of E. granulosus:
      • E. granulosus is the most reported species infecting herbivores globally.
      • Echinococcus ortleppi primarily infects cattle (as an intermediate host) however is reported less frequently.
    • Other related Echinococcus species include E. intermedius, E. multilocularis, E. candensis, E. equinus and E. felis.
    • Other Echinococcus species have been rarely reported in cattle, including E. intermedius and E. multilocularis. These species are not described in this article. 

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Clinical Effects

Epidemiology

Habitat

  • Adult tapeworms in anterior small intestine of dog.
  • Infection can also occur in foxes.
  • Eggs in environment: faeces, soil, water, etc.
  • Metacestodes (hydatid cysts) in sheep, cattle and other herbivores; the liver and lungs can be affected. 
  • Differences in tissue distribution of E. granulosus and E. ortleppi infections in cattle have not been identified.
  • In human, hydatid cysts are found most commonly in the liver, but lungs and other organs, including brain and bone, can be also be infected.
  • On very rare occasions an Echinococcus cyst has been identified in a dog.

Lifecycle

  • Adult .
  • Egg.
  • Hydatid cyst containing brood capsules and protoscoleces.
  • Echinococcus ortleppi has cattle as the primary intermediate host. Other differences in the lifecycle of E. granulosus and E. ortleppi have not been described

Transmission

To herbivore intermediate host (eg sheep, cattle and others)
  • Sporadic ingestion of eggs on pasture. Eggs in canine feces can be washed onto pasture or can be eaten by flies and deposited over the pasture.
To carnivore definitive host (eg dog)
  • E. granulosus sheep strain: ingestion of protoscoleces in fertile hydatid cyst in viscera when the dog is scavenging or is fed uncooked offal. E. granulosus infection has also been seen in dogs in hound kennels in which horse carcasses were fed.

Pathological effects

To herbivore intermediate host (eg sheep, cattle and others)
  • Hydatid cysts cause space occupying lesions in the lungs and less often in the liver of sheep, but these usually cause no apparent loss in production.
  • Echinococcus granulosus hydatid cysts are usually found in the liver or lungs of cattle. Echinococcus ortleppi hydatid cysts are are usually found in lungs of infected cattle.
  • Differences in clinical impact of bovine infections of E. granulosus and E. ortleppi have not been identified.
  • No protective immunity develops in the sheep populations.
  • Rarely cysts occur in other locations causing a variety of clinical signs.
To herbivore intermediate host (eg humans)
  • Many infections are asymptomatic, but symptoms may result from pressure atrophy induced by large cysts that compress or invade the biliary system, veins, bronchi, etc.
  • Patients present most commonly with abdominal or chest pain. Cysts in the brain or heart can be life-threatening.
  • Rupture of a cyst causes a variety of symptoms including those of anaphylaxis.
To carnivore definitive host (eg dog)
  • Adult worms, even in large numbers, in dogs cause little pathology and essentially no clinical signs are apparent.
  • Very little or no protective immunity develops within the dog population.
  • There is crypt hyperplasia, increased numbers of mast cells and goblet cells, and villous atrophy.

Control

Control via animal

  • Principle control measure:
    • Cattle, and other intermediate hosts play an important role in the spread, and thus aso the control of this parasite.
    • The parasite survives for a long time in the intermediate host and thus control measures should focus on eliminating the parasite at this stage of the lifecycle.
    • Uncooked offal should not be fed to dogs.
    • Dead sheep and cattle should be disposed of according to local regulations and in articular wshould be isolated from potential scavengers.
  • Supportive control measures:
    • Anthelmintic treatment of dog at a interval of 8 weeks (To treat developed adult tapeworms in the small intestine).
    • Pick up dog feces (Echinococcus spp eggs are immediately infective).
    • Prevent dogs from roaming.

Control via chemotherapies

  • Making sure farm dogs (Definitive hosts which spread infection) are wormed regularly with praziquantel Praziquantel.
    • Typical dose: 5 mg/kg body weight.
    • Dogs in rural areas, or those considered to be at high risk of tapeworms may be dosed every 4 weeks, to ensure that newly acquired tapeworms are destroyed before reaching maturity.             
Please check the specific product information.
  • For herbivores (Intermediate hosts) infected with metacestodes usually no treatment prescribed due to absence of clinical effects. Even larger doses of praziquantel may have little effect on metacestode stages even if prescribed for infected intermediate hosts.

Control via environment

  • Avoidance of dog faeces on pasture or within feed supplies.
  • Egg control usually not practical on farm however if a farm dog is diagnosed infected treatment of the environment maybe implied to minimize transmission to potential intermediate hosts.
  • Although eggs are resistant to many disinfectants desiccation or dry heat kills eggs and sodium hypochlorite solution (3.75% or higher) for at least 2-3 hours can be used to clean concrete surfaces.

Vaccination

  • No vaccine is available for either the dog or sheep.
  • Recently, an antigen that has induced protection experimentally in sheep has been identified, cloned and expressed. It is likely to become available for use in control programs around the world in the next few years, although it yet requires field testing.

Other countermeasures

Control programs

  • Control programs against Echinococcus granulosus (sheep strain) have been introduced in many countries. Measures can include:
    • Routine praziquantel treatment of dogs.
    • Removal of stray dogs.
    • Education of the population, eg not to feed sheep to dogs.
  • This can break transmission from dogs to sheep within 1 year but must continue for 10-15 years until all infected sheep have been removed (at least 2 sheep generations).

Endemic E. granulosus

  • Where there is no control, E. granulosus may be in a stable endemic steady state.
  • Herbivores, sheep especially due to their epidemiological importance, remain susceptible to infection so sheep continually acquire infection with age (as in nature they are never challenged with enough eggs at any one time to stimulate immunity).
  • Mathematically, this gives E. granulosus a reproduction ratio of about 1.3-1.6 and it is in endemic steady state.
  • If a control campaign is instigated that reduces the reproduction ratio to < 1 the parasite population will gradually decline to extinction.

Diagnosis

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Conraths F J, Deplazes P (2015) Echinococcus multilocularis: Epidemiology, surveillance and state-of-the-art diagnostics from a veterinary public health perspective. Vet Parasitol 213,149–161 PubMed doi:10.1016/j.vetpar.2015.07.027.
  • Craig P, Mastin A, van Kesteren F, Boufana B (2015) Echinococcus granulosus: Epidemiology and state-of-the-art of diagnostics in animals. Vet Parasitol 213, 132-148 PubMed doi:10.1016/j.vetpar.2015.07.028.
  • Hegglin D, Deplazes P (2013) Control of Echinococcus multilocularis: Strategies, feasibility and cost–benefit analyses. Int J Parasitol 43, 327-337 PubMed doi:10.1016/j.ijpara.2012.11.013.
  • Buishi I et al (2005) Reemergence of canineEchinococcus granulosusinfection, Wales. Emerg Infect Dis 1, 568-571 PubMed.
  • Lloyd S et al (1998) Use of sentinel lambs to survey the effect of an education progamme on control of transmission of Echinococcus granulosusin South Powys, Wales. Bulletin of the World Health Organisation 76, 469-473.
  • Cabrera P A, Parietti S, Haran G, Benavidez U, Lloyd S, Perera G, Valledor S, Gemmell M A & Botto T (1996) Rates of reinfection with Echinococcus granulosus, Taenia hydatigena, Taenia ovis and other cestodes in a rural dog population in Uruguay. Intern J Parasitol 26, 79-83 (Methods for baseline analysis).
  • Lloyd S, Martin S C, Walters T M H & Soulsby E J L (1991) Use of sentinel lambs for early monitoring of the South Powys Hydatidosis Control Scheme - prevalence of Echinococcus granulosus and some other helminths. Vet Rec 129, 73-76 (Surveillance of control).

Other sources of information

  • www.esccap.org: website for European Scientific Counsel: Companion Animal Parasites, guidelines for worm control in cats and dogs.
  • www.wales.nhs.uk : Hydatid disease (Echinococcosis) background information on hydatid disease and overview of the current situation in Wales.
  • www.wales.nhs.uk/sitesplus/888/page/43882 : Summary of hydatid disease (Echinococcosis) control and eradication program in Wales.
  • Wales Assembly Government Website : an overview of the current hydatid control program in Wales, questionnaire for the public, downloadable leaflet and poster.
  • Andrews A H, Blowey RW, Boyd H, Eddy R G (2004) Bovine Medicine: Diseases and Husbandry of Cattle. 2nd edn, Oxford.
  • Eckert J et al (2002) WHO/OIE Manual on echinococcosis in humans and animals: a public heath problem of global concern. Published by WHO and OIE, Paris.
  • Radostits O M, Gay C C, Blood D C, Hinchcliff K W (2000) Veterinary medicine: A textbook of disease of cattle, sheep, pigs, goats and horses. 9th edn. New York: Saunders.
  • Gemmell M A & Roberts M G (1998) Cystic echinococcosis (echinococcus granulosus. In: Zoonoses - biology, clinical practice and public health control.Oxford University Press. pp 665-688.
  • Kaufmann K (1996) Parasitic infections of domestic animals. 1st edn, Basel: Birkhauser Verlag.
  • Thompson R C A & Lymbery A J (eds) (1995) Echinococcus and Hydatid Disease. Wallingford, CAB International. pp 477 (Complete overview).

Organisation(s)

  • Royal (Dick) School of Veterinary Studies, University of Edinburgh, UK.

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