First case of echinococcosis caused by Echinococcus canaden...

In Norway, the parasite Echinococcus canadensis G10 was detected in a dead elk found in Innlandet County. A sample was taken as part of the Norwegian Food Safety Authority’s regular slaughter inspection. The animal, in good general condition, presented cysts on the lungs.

This is the first time the parasite has been detected in a moose in Norway, E. canadensis G10 has not been detected in Norway before, but has been detected in Sweden and Finland. In Finland it was also the cause of a human case.

In nature, E. canadensis it has a silvatic and semi-synanthropic nature with a life cycle that sees wild deer (including moose) as intermediate host and canids (dogs, coyotes and wolves) as definitive hosts. Echinococcosis can infect humans, but the Institute of Public Health believes there is a very low risk of infection in this case.

Cystic echinococcosis or hydatid disease reminder

Human echinococcosis is a zoonosis (disease transmitted to humans from animals) caused by parasites, i.e. tapeworms of the genus Echinococcus. Echinococcosis comes in 4 forms:

• cystic echinococcosis, also known as hydatid disease or hydatid disease, due to infestation by a species complex centered on Echinococcus granulosum ;
• alveolar echinococcosis, due to infestation with E.multilocularis ;
• two forms of neotropical echinococcosis: polycystic echinococcosis caused by E. vogeli ; and unicytic echinococcosis caused by E.oligarthrus.

Geographical distribution

Cystic echinococcosis exists on all continents except Antarctica, particularly in the countries of the Mediterranean Basin, North Africa, Latin America, Australia, New Zealand, China and Central Europe.

Transmission

The parasite cycle includes two hosts: an intermediate host (HI) and a definitive host (HD).

A number ofherbivorous and omnivorous animals Behave like intermediate hosts to Echinococcus. They become infected by ingesting the embryonated eggs (embryophores) of the parasite present in the external environment (food and water) which then develop into the larval stages in the viscera. The larvae cross the digestive wall and reach the liver, or even other organs where they develop, through the bloodstream.

The carnivores Behave like definitive guests for the parasite and host the mature tapeworm in their intestines where it will lay eggs. These definitive hosts become infected by ingesting the viscera of the intermediate hosts containing the parasite larvae.

The humans I am accidental intermediate hosts. They contract the infection by ingesting embryophores after direct contact with the dog (licking, petting), more rarely indirectly from contaminated food or water. The eggs penetrate the digestive wall and reach the liver through the bloodstream. More rarely they can reach other organs.

Currently, on the basis of the phylogenetic analysis and the specificity of the parasitic hosts in their life cycles, 5 species are distinguished within the complex Echinococcus granulosum lateral sense. : E. grainy strictly speaking, E.equinus, E. ortleppi, E. canadensis And E. felidis (Vector Parasite. 2022 Mar 28;15(1):109.doi:10.1186/s13071-022-05197-8.)

• E. grainy strict sense. includes genotypes G1 and G3, previously described as “sheep stock” and “buffalo stock” respectively. The G2 genotype is no longer considered a valid genotype, but is recognized as a microvariant of G3. E. grainy ss is distributed worldwide both due to the low specificity of HI and the extensive stock trade. The main HI and HD contributing to the maintenance of the life cycle of the parasite are small ruminants (mainly sheep) and dogs (mainly shepherd dogs) respectively. E. grainy ss causes 88.5% of human hydatid infections.
• E.equinus it is represented by the G4 genotype, previously described as a “horse strain”. The main HI and HD are equines and dogs. This species was long thought not to be zoonotic until two cases of human infection were recently documented in Turkey and Uzbekistan.
• E. ortleppi it is represented by the G5 genotype, previously described as “bovine strain”. The main HI and HD are cattle and dogs. This parasitic infection has become rare in animals, and few human infections have been documented worldwide.
• The bunch E. canadensis it is divided into two main clades. G6/7 genotypes (previously described as “camel strain” and “pork strain”, respectively) and G8/G10 genotypes (also known as “cervid strains”). The G6/7 genotypes are distributed worldwide and have a rather low specificity of HI, mainly involving domestic species such as pigs, camels and goats, and dogs such as DH. E. canadensis (G6/7) is the second most important species in terms of public health, being responsible for approximately 11% of documented human infections worldwide. The G8/G10 genotypes have a circumpolar distribution in the northern hemisphere. The main HI and HD contributing to the maintenance of the life cycle of the parasite are wild cervids (such as moose and red deer) and wolves, respectively, but also, to a lesser extent, semi-domesticated reindeer and hunting, sled or hunting dogs. shepherd. Few human infections E. canadensis (G8/G10) have so far been documented. The taxonomic status of the group ofAND. canadensis (G6/7, G8 and G10) is still under discussion.
• E. felidis (also called the “lion stock”), has a wild life cycle and is found only in sub-Saharan Africa. No human infections have been documented so far.

Symptoms

Human infestation from E. grainy causes the development of one or more hydatid cysts located most commonly in the liver and lungs and less commonly in the bones, kidneys, spleen, muscles, and central nervous system.

The asymptomatic incubation period of the disease can last many years before the hydatid cysts are sufficiently developed to trigger clinical signs.

Liver hydatids often cause abdominal pain, nausea, and vomiting. In case of pulmonary involvement, the clinical signs are chronic cough, chest pain and shortness of breath. Other signs depend on the location of the hydatid cysts and the pressure exerted on the surrounding tissues. Nonspecific signs include anorexia, weight loss, and fatigue.

Treatment

There are three treatment options for treating cystic echinococcosis:

• percutaneous treatment of hydatid cysts using the PAIR technique (puncture, aspiration, injection, re-aspiration);
• surgery ;
• anti-infective drug treatment (albendazole).

Prevention

Cystic echinococcosis is a preventable disease because the definitive and intermediate hosts are domesticated species. Prevention is based on the following measures:

• public education;
• periodic deworming of dogs with praziquantel (at least 4 times a year);
• systematic euthanasia of stray dogs;
• prevent dogs from feeding on infected sheep carcasses;
• caution in human-dog contact (licking, caresses, etc.);
• improve hygiene during livestock slaughter (including proper destruction of infected offal);
• vaccination of sheep with a recombinant antigen ofE. granulosus (EG95) offers encouraging prospects for control. The vaccine is currently being manufactured for commercial availability and is licensed in China and Argentina. In Argentina, trials have shown the added value of vaccinating sheep, and in China, the vaccine is being used on a large scale.

On an individual level

• Do not consume food or water that may have been contaminated with dog feces.
• Wash your hands with soap and warm water after handling dogs and before handling food.

Source: Promed

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