Echinococcus granulosus and ortleppi

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. 

Distribution

Worldwide

• Echinococcus granulosus and E. ortleppi are thought to have a global distribution, except for a few notable exceptions:
  • Iceland and Greenland have been declared free of echinococcosis.
  • Tasmania and New Zealand are provisionally free from the parasite.
  • Programs are underway in other countries such as Greek Cyprus and some South American countries to eliminate this parasite.
• The lifecycle of these species are similar and have a two-host cycle from canid to ungulate.

• In some areas of the world there is a natural or sylvatic cycle from, for example, wolf to moose. Elsewhere the parasite has adapted to a domestic cycle with dogs as the canine host and primarily sheep but also horses, cows and pigs as the intermediate host.
• The sheep strain of E. granulosus is the most common in Europe and sheep are the common intermediate host effected.
• Distinct strains have been recognized for some time, and there has been reclassification of the cattle strain, as E. ortleppi. Subsequently the specific epidemiology of E. ortleppi is poorly defined.
• Both E. granulosus and E. ortleppi are potentially zoonotic.
  • Human infection and disease is most associated with the E. granulosus sheep strain, although all strains and species are zoonotic except the E. equinus)  .
• Cattle infected with E. species tend to be asymptomatic hence interest in the parasite is primarily from a zoonotic perspective.

Regions with endemic canid infections and reported zoonotic disease

North America

• In circumpolar taiga and tundra, the northern biotype of E. granulosus has a sylvatic life cycle.
  • Large cervids with hydatid cysts and wild canids with the adult stage. Domestic and wild canines can also serve as intermediate hosts.
  • Zoonotic infecion in these areas occur in high numbers when domestic dogs become infected, such as Alaska and Canada.

• In the Southern United States, the sheepdog cycle occurs:
  • Particulary in Western states such as California, Arizona, New Mexico, and Utah where ovine infections are reported (Intermediate stage infections).
  • Human infections have occurred in Native Americans (Zuni, Navajo, and Santo Domingo tribes) who raise their sheep and live in close proximity with their animals.
  • Utah has had about 50 surgical cases in humans in the last 50 years, with these cases being confined mainly to the central sheep-raising portion of the state.
  • Cases have been markedly reduced in the last decade through the holding of public health clinics, education, and regular anthelmintic treatment of dogs.
• Cattle and buffalo are not currentlyconsidered to be an important intermediate host species for maintaining Echinococcus species in Northern America.

UK

• In Britain the E. granulosus sheep strain is common in the sheep raising areas of South Wales and the English/Welsh border, particularly Powys. Also parts of Scotland, primarily the Hebridean islands.
• From 1983-89 there was an eradication campaign in South Powys, South Wales. From 1989 this was replaced by an education campaign. The campaign resulted in a decrease in the prevalence of infection, for example the prevalence in older sheep fell by more than 50%, however, 10% of sheep remained infected.
• In 1995-6, prevalance in lambs was between 4.3 and 10.4% in Powys and Gwent. In 2005, 8.1% of farm dogs from the area were positive for Echinococcus species coproantigen.
• In 2006, a public awareness campaign implemented by the Welsh Assembly Government to raise awareness of the disease and encouraging dog owners to consult their vets about their dog worming practices.
• In 2008, a 10-year dog dosing program began and a public awareness campaign was initiated with the aim to eradicate disease in Wales. Monitoring impact is ongoing currently ongoing, with the aim to eradicate disease in 10-20 years
• Since the year 2000, there have been 19 confirmed cases in Wales and 77 in England with a proportion of these cases being acquired abroad. Hence disease is now considered rare in human populations.
• Cattle are not currently considered to be an important intermediate host species for maintaining Echinococcus species in the UK and Europe.