The dog is definitive host.. Echinococcus granulosis

The dog is definitive host:
a- Echinococcus granulosis***
b- Trypanosoma sp.
c- Plasmodium malaria
d- Toxoplasma gondii.

Echinococcus granulosus or echinococcus dog is a very small tapeworm whose adult parasitic small intestine dog and whose larval or hydatid form can develop in humans by giving the various tables of hydatidosis, a disease that should not be confused with alveolar echinococcosis (due to Echinococcus multilocularis).
The intermediate host of Echinococcus granulosus is often sheep.

Genetic:
Recently acquired data show that taxon E.
granulosus shows a great diversity is actually an assembly of several and quite diverse genotypes, which could lead to a revision or precision of taxonomic subsets.
The latter have marked differences, in terms of epidemiology, eco-epidemiology and in terms of pathogenicity for humans.
This can also explain the very uneven geographic and regional distribution of areas of high endemicity for humans.
This variation was formerly attributed to differences in human behavior.
Several genotypes can coexist in the same geographical region, in different wild or farm animals or domestic (dogs, cat ...). Thus, a recent study (1999) showed in Argentina - from 33 isolates - the coexistence in farms of the country of at least distinct genotypes (a common sheep strain (G1) in the sheep of the province of Chubut and in the man in the province of Río Negro, a strain specific to Tasmanian sheep (G2) in sheep and found in a human from the province of Tucumán, a swine strain (G7) in pigs in the province of Santa Fe and one strain Carnel (G6) in humans found in the provinces of Rio Negro and Buenos Aires.
The detection of this last strain, harbored by pigs and the appearance of a "Tasmanian" sheep strain, has "considerable implications for the implementation of hydatid control programs due to the reduction of maturation time. of two strains in the dog compared to the common sheep strain ".
This is the first time that genotypes G2 and G6 have been found in humans, with "significant consequences for human health".
The same strain carried by the camel affects men in some areas and not in others, without explanation to date.

Geographical distribution and importance:
Cosmopolitan, its exact world distribution is poorly known, but a priori follows that of sheep farming, usual intermediate host.
Rare in Europe and Asia, it is widespread in Australia, New Zealand, North Africa, the US Middle East and Argentina.
Some poor European regions where anti-test drugs are used less are more vulnerable.
As an example in Sardinia, a survey has shown that domestic slaughterings are the most frequent and that offals are given to dogs (17%) after boiling (37%), or thrown in the trash (23%), or superficially buried (15%).
69% of breeders reported treating their dogs, but only 10% used a cestodicidal drug.
In this same Sardinian context, the coprological analysis of samples of 300 dog excrements showed a prevalence of 8 to 10% of the pathogen (E. granulosus or E. multilocularis). This parasite derives its importance from the usual frequency and severity of human injury in these areas.
In Europe: E. granulosus has a very uneven geographic distribution on this continent, with very low prevalence rates in some of the Nordic and Central European countries, average endemicity in other countries or regions, and high endemicity in some countries. regions of southern and eastern Europe.
The European focus is centered on Central Europe (where "five strains of E. granulosus have been identified (...) that differ in their life cycle as well as for their morphology, biochemistry, genetics and some other functional aspects") .

Biology:
The adults, always in great numbers, carpet the small intestine of the dog like a velvet. Embryophores, eliminated with faeces, soil the soil and pastures.
Sheep, and many other herbivores, including wild ones (including deer, for example), become infected by ingesting them.
Released by digestion, the hexacanth embryo (embryo of the tapeworm echinococcus) crosses the digestive mucosa and migrates by blood to the liver (70%), the lung (20%) and, only if these two successive filters have failed, to the other viscera.
Installed, the embryo develops into a very particular larva: hydatid.
The latter is rapidly vesiculated, is the seat of an intense larval multiplication, budding on its internal surface (proliferous membrane = which carries the pathogen) a large number of vesicles which bathe in a clear liquid, salty and tense, the hydatid liquid.
In turn, these proliferating vesicles burst on their inner sides with scolex, each of which could give an adult tapeworm.
This second order multiplication (1 hexacanth embryo giving a scolex) is accompanied by a very large volume increase, whereas around the hydatid, an intense tissue reaction will form the wall of the hydatid cyst.
It is by eating offal refused and abandoned on site, sheep that the dog is infected and maintains the infection all the more easily that, even heavily parasitized, it is still a healthy carrier.
The man is infected by swallowing some embryophores, either as a food stain, or through the hands soiled in contact with the coat of dogs.
The importance of dog-dog and sheep-dog contacts explains the often pastoral character of the affection.
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