echinococcosis (hydatids)

introduction

often referred to as hydatid disease or echinococcal disease
a tapeworm parasitic disease that affects both humans and other mammals, such as sheep, dogs, rodents and horses

eggs are passed through the faeces of the definitive host and it is the ingestion of these eggs that lead to infection in the intermediate host
from the embryo released from an egg develops a hydatid cyst, which grows to about 5–10 cm within the first year and is able to survive within organs for years
protoscolices bud from these cysts and can then form adult tapeworms up to 7mm long depending on species
transmitted to definitive hosts is then by means of eating infected, cyst-containing organs

humans are accidental intermediate hosts that become infected by handling soil, dirt or animal hair that contains eggs
incubation period can be months to years or even decades
75% of cysts are in the liver, 5-15% are in the lungs, 10-20% of cases they are in the spleen, brain, heart, kidneys or other organs

by far the most common form in humans and is caused by Echinococcus granulosus which generally result in slow growing hepatic hydatid cysts
present virtually worldwide, sheep farmers and those who come in contact with sheep dogs are most at risk
definitive host: dogs
intermediate hosts: sheep, goats, swine and other wild herbivores

is caused by Echinococcus multilocularis which mainly only occurs in the northern hemisphere
rarely diagnosed in humans but may become an emerging disease in many countries
high fatality rate
in Europe, existed only in France, Switzerland, Germany, and Austria, but with spread of infection rate in foxes, has spread to other European countries since the 1990's.
definitive host: foxes, dogs, other canidae and cats
intermediate hosts: small rodents