Todayโs path rounds are on ๐๐๐ก๐ข๐ง๐จ๐๐จ๐๐๐จ๐ฌ๐ข๐ฌ!
๐๐ก๐๐ญ ๐ข๐ฌ ๐ข๐ญ?
๐๐๐ก๐ข๐ง๐จ๐๐จ๐๐๐จ๐ฌ๐ข๐ฌ is infection with either Echinococcus multilocularis or Echinococcus granulosus. These are species of ๐ญ๐๐ฉ๐๐ฐ๐จ๐ซ๐ฆ๐ฌ, little internal parasites that can have some serious consequences. Here in North America, E. multilocularis is the most important, and the one that weโll be talking about today.
๐๐ก๐จ ๐ ๐๐ญ๐ฌ ๐ข๐ญ?
The primary species that E. multilocularis infects are foxes, coyotes and wolves. However, dogs, cats, or even people, who come in contact with infected animals may become infected themselves!
๐๐จ๐ฐ ๐๐จ ๐๐ง๐ข๐ฆ๐๐ฅ๐ฌ ๐ ๐๐ญ ๐ข๐ง๐๐๐๐ญ๐๐?
As mentioned before, the main hosts of this tapeworm are foxes, wolves and coyotes. In these animals, the adult worms reside in the intestine, and produce infective eggs which are passed in the feces. These eggs are ingested by ๐ข๐ง๐ญ๐๐ซ๐ฆ๐๐๐ข๐๐ญ๐ ๐ก๐จ๐ฌ๐ญ๐ฌ like mice or voles. Once inside an intermediate host, the egg hatches, travels through the intestinal wall, enters the liver and forms a ๐ก๐ฒ๐๐๐ญ๐ข๐ ๐๐ฒ๐ฌ๐ญ, which is a big cyst that contains ๐ฉ๐ซ๐จ๐ญ๐จ๐ฌ๐๐จ๐ฅ๐ข๐๐๐ฌ. Protoscolices are basically the โheadโ of a new tapeworm. When the intermediate host is consumed by a fox, wolf or coyote, these protoscolices attach themselves to the intestinal wall of their new host, and develop into an adult tapeworm.
๐๐ก๐ฒ ๐ข๐ฌ ๐ญ๐ก๐ข๐ฌ ๐ ๐ฉ๐ซ๐จ๐๐ฅ๐๐ฆ?
Many species can be ๐๐๐๐ซ๐ซ๐๐ง๐ญ ๐ข๐ง๐ญ๐๐ซ๐ฆ๐๐๐ข๐๐ญ๐ ๐ก๐จ๐ฌ๐ญ๐ฌ (intermediate hosts that arenโt supposed to happen!). We most commonly see this in dogs and cats. These aberrant hosts develop similar hydatid cysts as seen in rodents, particularly in the liver and lungs. This can cause progressive abdominal enlargement, vomiting and inappetence. If a cyst ruptures, it can induce a severe ๐๐ง๐๐ฉ๐ก๐ฒ๐ฅ๐๐๐ญ๐ข๐ ๐ซ๐๐๐๐ญ๐ข๐จ๐ง, because the body simply has no idea where all this foreign material came from!
Another of these possible aberrant hosts is humans. Echinococcosis is a serious ๐ณ๐จ๐จ๐ง๐จ๐ฌ๐ข๐ฌ (animal disease that can infect humans). Often in humans, the only clinical sign is abdominal pain and possibly ๐ฃ๐๐ฎ๐ง๐๐ข๐๐ (yellowing of the tissues) indicating liver failure. Untreated infections have a very high fatality rate, so prompt diagnosis is critical!
๐๐ซ๐๐งโ๐ญ ๐๐จ๐ ๐ฌ ๐ข๐ง ๐ญ๐ก๐ ๐ฌ๐๐ฆ๐ ๐๐๐ฆ๐ข๐ฅ๐ฒ ๐๐ฌ ๐๐จ๐ฑ๐๐ฌ, ๐ฐ๐จ๐ฅ๐ฏ๐๐ฌ ๐๐ง๐ ๐๐จ๐ฒ๐จ๐ญ๐๐ฌ? ๐๐ก๐ฒ ๐๐ซ๐ ๐ญ๐ก๐๐ฒ ๐๐๐๐ซ๐ซ๐๐ง๐ญ ๐ก๐จ๐ฌ๐ญ๐ฌ?
One weird thing about dogs is that they can actually act as either a primary host, like a fox or wolf, and an aberrant host. Itโs technically possible for this to even occur in the same animal, where the animal would have adults producing eggs and hydatid cysts at the same time. Weird!
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐๐ข๐๐ ๐ง๐จ๐ฌ๐๐?
In our โdomesticโ patients (humans included), usually an ultrasound or X-ray is a good starting point to identify the large cysts in the liver. From there, a sample of the cyst fluid can be taken to visualize the protoscolices under a microscope, confirming the diagnosis.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐ญ๐ซ๐๐๐ญ๐๐?
Typically, depending on the size and location of the cysts, surgical removal of the cysts is the main treatment. This is usually paired with administration of ๐๐ฅ๐๐๐ง๐๐๐ณ๐จ๐ฅ๐, a potent anti-parasitic medication. However, hydatid cysts have a fairly impenetrable wall that makes it difficult for medication to enter where it is needed most. For this reason, human patients are often on albendazole for 2 years or more! Crazy.
๐๐ก๐จ๐ญ๐จ๐ฌ
1) A liver showing hydatid cysts.
2) The same liver with a needle showing the contents of the cyst. This is called ๐ก๐ฒ๐๐๐ญ๐ข๐ ๐ฌ๐๐ง๐, and contains the protoscolices!
3) Hydatid cysts in the lung of a moose.
4) Protoscolices from a hydatid cyst, as seen under the microscope!
๐๐จ๐ฎ๐ซ๐๐๐ฌ
Maxie, G. Jubb, Kennedy and Palmerโs Pathology of Domestic Animals, Volume 2. Sixth Edition.
Pearson, R.D. Echinococcosis. Merck Manual, 2020.
Photos 1-4 courtesy of University of Calgary Diagnostic Services Unit.
