Alveolar hydatid disease

Overview
Alveolar hydatid disease, also known as Alveolar echinococcosis, Echinococcosis Alveolar and Echinococciasis multilocular is a disease that originates from the parasitic flatworm Echinococcus multilocularis. This disease is not to be confused with the similar Echinococcosis, which originates from the parasite Echinococcus granulosus

Epidemiology and Demographics
Alveolar hydatid disease is found worldwide, mostly in northern latitudes. Cases have been reported in central Europe, Russia, China, Central Asia, Japan, and North America. In North America E. multilocularis is found primarily in the north central region from eastern Montana to central Ohio, as well as Alaska and Canada. Human cases have been reported in Alaska, the province of Manitoba, and Minnesota. Prevalence among wild foxes and coyotes is high, and may reach over 50% in some areas; however, even in these areas, transmission to humans has been low.

Infestations of Animals
Wild foxes, coyotes, and cats get infected when they eat Echinococcus multilocularis larvae in infected rodents, field mice, or voles. Cats are less susceptible than dogs, but because they catch and eat rodents often, may also become infected. Once the animal becomes infected, the tapeworm matures in its intestine, produces eggs, and the infected animal passes eggs in the stool. These tapeworm eggs, which are directly infectious to other animals, are too tiny to see, and will stick to anything with which they come in contact. Coyotes, foxes, dogs, and cats are not harmed by the tapeworm and do not have symptoms of AE.

Routine fecal examinations are not sufficient to diagnose E. multilocularis infection. Infection with the E. multilocularis tapeworm and other tapeworms may occur at the same time. Eggs of Taenia species tapeworms and Echinococcus tapeworms are similar in shape and size and are very difficult to tell apart.

Infestation of Human
By accidentally swallowing the eggs of the E. multilocularis tapeworm. Humans can be exposed to these eggs in two main ways, both of which involve "hand-to-mouth" transfer or contamination:
 * By directly ingesting food items contaminated with stool from foxes or coyotes. This might include grass, herbs, greens, or berries gathered from fields.
 * By petting or handling household cats and dogs infected with the E. multilocularis tapeworm. These pets may shed the tapeworm eggs in their stool, and their fur may be contaminated. Some dogs "scent roll" in foreign material (such as wild animal feces) and may become contaminated this way.

Associated Conditions

 * Cardiac and vascular conditions such as myocarditis or pericarditis
 * Hypersensitivity type 1 reactions such as Anaphylaxis
 * Neurologic conditions such as aseptic meningitis
 * Infection and infective conditions such as a lung abscess and lung cavitation

History and Symptoms
AE is caused by tumor-like or cyst-like tapeworm larvae growing in the body. AE usually involves the liver, but can spread to other organs of the body. Because the cysts are slow-growing, infection with AE may not produce any symptoms for many years. Pain or discomfort in the upper abdominal region, weakness, and weight loss may occur as a result of the growing cysts. Symptoms may mimic those of liver cancer and cirrhosis of the liver. As a summary:
 * Abdominal mass
 * Ascites
 * Hemoptysis
 * Hepatomegaly
 * Hydrocephalus

Other Findings

 * Zoonosis

Laboratory Findings

 * Eosinophilia
 * Cholestatic jaundice

Imaging findings

 * Intracranial calcification

Surgery
Surgery is the most common form of treatment for AE, although removal of the entire parasite mass is not always possible. After surgery, medication may be necessary to keep the cyst from growing back.

Prevention
If you live in an area where E. multilocularis is found in rodents and wild canines, take the following precautions to avoid infection:
 * Don't touch a fox, coyote, or other wild canine, dead or alive, unless you are wearing gloves. Hunters and trappers should use plastic gloves to avoid exposure.
 * Don't keep wild animals, especially wild canines, as pets or encourage them to come close to your home.
 * Don't allow your cats and dogs to wander freely or to capture and eat rodents.
 * If you think that your pet may have eaten rodents, consult your veterinarian about the possible need for preventive treatments.
 * After handling pets, always wash your hands with soap and warm water.
 * Fence in gardens to keep out wild animals.
 * Do not collect or eat wild fruits or vegetables picked directly from the ground. All wild-picked foods should be washed carefully or cooked before eating.