Echinococcus canadensis

Echinococcus canadensis
Systematics
Class :	Tapeworms (Cestoda)
Subclass :	True tapeworms (Eucestoda)
Order :	Cyclophyllidea
Family :	Taeniidae
Genre :	Echinococcus
Type :	Echinococcus canadensis
Scientific name
	Echinococcus canadensis
	Webster & Cameron , 1961

Echinococcus canadensis is a parasitic tapeworm belonging to the genus Echinococcus and one of the pathogens causing cystic echinococcosis , a serious zoonotic disease in humans.

description

Echinococcus canadensis corresponds in its morphology to the tripartite dog tapeworm ( Echinococcus granulosus ). The group of species around the tripartite dog tapeworm has long been considered to be a number of genotypes (G1 to G10) of this species ( Echinococcus granulosus sensu lato ). Only recently have several species been described after phylogenetic studies: Echinococcus granulosus sensu stricto (G1 to G3), Echinococcus equinus (G4), Echinococcus ortleppi (G5) and Echinococcus canadensis (G6 to G10). In the larval stage, these species are morphologically impossible to distinguish as adult parasites. In addition to the genetic analysis for some species, because of their different antibody profiles, an ELISA allows differentiation . In addition, the species differ in terms of their intermediate hosts and, although they can all cause cystic echinococcosis, their infectivity to humans.

Spread and hosts

Echinococus canadensis is distributed worldwide. There are, however, differences between the genotypes in the intermediate hosts they attack and, depending on this, in their geographical distribution. The genotype G6 ( English camel strain ) primarily affects camels. The genotype G7 ( English pig strain ) specializes in pigs; human infections are unknown in areas where pigs are neither kept nor consumed. The genotypes G8 ( English North American cervid strain ) and G10 ( English Fennoscandian cervid strain ) predominantly infect deer in North America and Northern Europe. The genotype G9 ( English variant pig strain or human-pig strain ) again prefers pigs as intermediate hosts. The main hosts of all genotypes are dogs , namely wolves and coyotes , but also domestic dogs with access to the innards of dead intermediate hosts.

Humans are always false intermediate hosts. For the genotype G7 of Echinococcus canadensis it has been shown in animal experiments that it does not form cysts in mice .

Epidemiology

Of the diseases from cystic echinococcosis worldwide, 77 percent are caused by the tripartite dog tapeworm ( Echinococcus granulosus ) and 22 percent by Echinococcus canadensis . The remaining percentage is assigned to the other species in the group. However, the distribution varies greatly from region to region. In a retrospective analysis of 104 cases of cystic echinococcosis in Austria, it was found that 92 percent of the patients born in Austria, 33 of the sick migrants from the former Yugoslavia, and no migrants of Turkish origin were infected by the G7 strain, which infects pigs as intermediate hosts .

Clinical picture of an infection

There is evidence that liver cysts caused by Echinococcus canadensis are smaller than those caused by Echinococcus granulosus . In addition, the G6 strain is likely to affect the brain more frequently. For cases of infection with the G7 strain, an examination of previous cases always revealed cysts in the liver and, in one case, also in the lungs. With an average of 5.7 centimeters and a maximum of ten centimeters in diameter, the cysts were only about half the size of those of Echinococcus granulosus .

literature

Thomas Romig, Dennis Ebi and Marion Wassermann: Taxonomy and molecular epidemiology of Echinococcus granulosus sensu lato . In: Veterinary Parasitology 2015, Volume 213, No. 3–4, pp. 76–84, doi : 10.1016 / j.vetpar.2015.07.035
Renate Schneider et al .: Echinococcus canadensis G7 (Pig Strain): An Underestimated Cause of Cystic Echinococcosis in Austria . In: American Journal of Tropical Medicine and Hygiene 2010, Volume 82, No. 5, pp. 871-874, doi : 10.4269 / ajtmh.2010.09-0639 .

Individual evidence

↑ ^a ^b ^c ^d Lucas L. Maldonado et al .: The Echinococcus canadensis (G7) genome: a key knowledge of parasitic platyhelminth human diseases . In: BMC Genomics 2017, Volume 18, Article 204, p. 2, doi : 10.1186 / s12864-017-3574-0 .
↑ Janna Schurer et al .: Surveillance for Echinococcus canadensis genotypes in Canadian ungulates . In: International Journal for Parasitology: Parasites and Wildlife 2013, Volume 2, pp. 97-101, here p. 97, doi : 10.1016 / j.ijppaw.2013.02.004 .
↑ Thomas Romig, Dennis Ebi and Marion Wassermann: Taxonomy and molecular epidemiology of Echinococcus granulosus sensu lato , p. 78.
↑ Renate Schneider et al .: Echinococcus canadensis G7 (Pig Strain): An Underestimated Cause of Cystic Echinococcosis in Austria , p. 871.
↑ Renate Schneider et al .: Echinococcus canadensis G7 (Pig Strain): An Underestimated Cause of Cystic Echinococcosis in Austria , p. 872.

[Maldonado_2017_2-1] Lucas L. Maldonado et al .: The Echinococcus canadensis (G7) genome: a key knowledge of parasitic platyhelminth human diseases . In: BMC Genomics 2017, Volume 18, Article 204, p. 2, doi : 10.1186 / s12864-017-3574-0 .

[Schurer_2013_97-2] Janna Schurer et al .: Surveillance for Echinococcus canadensis genotypes in Canadian ungulates . In: International Journal for Parasitology: Parasites and Wildlife 2013, Volume 2, pp. 97-101, here p. 97, doi : 10.1016 / j.ijppaw.2013.02.004 .

[Romig_2015_78-3] Thomas Romig, Dennis Ebi and Marion Wassermann: Taxonomy and molecular epidemiology of Echinococcus granulosus sensu lato , p. 78.

[Schneider_2010_871-4] Renate Schneider et al .: Echinococcus canadensis G7 (Pig Strain): An Underestimated Cause of Cystic Echinococcosis in Austria , p. 871.

[Schneider_2010_872-5] Renate Schneider et al .: Echinococcus canadensis G7 (Pig Strain): An Underestimated Cause of Cystic Echinococcosis in Austria , p. 872.