Echinococcus multilocularis

​Echinococcus multilocularis Updates

​Updated: June 14, 2024

Echinococcus multilocularlis in Kentucky ​Wildlife

​Kentucky has a confirmed case of E. multilocularis in a coyote found in Rowan County.​

DISEASE INFORMATION​

​​​What are the symptoms of E. multilocularis​?

Infected wild canids and domestic dogs typically remain asymptomatic. However, the intermediate rodent hosts and non-target, dead-end hosts infected with E. multilocularis may display symptoms and develop internal cysts. The cysts associated with E. multilocularis larvae develop slowly, and infected animals may not display any symptoms for extended periods, sometimes years. However, if symptoms do arise, they may include abdominal pain, weight loss, weakness, and indications of liver disease.

How is E. multilocularis s​pread?

E. multilocularis is primarily spread through the ingestion of parasite eggs. Its life cycle involves two hosts: a definitive host (usually canids such as foxes, coyotes or domestic dogs) and an intermediate host (typically small mammals like rodents). The life cycle and transmission of the parasite typically occurs in the following manner:

1. Definitive Host: In the definitive host (coyotes, foxes, or domestic dogs)​, adult tapeworms reside in the small intestine. These tapeworms produce eggs, which are shed in the host's feces.
   
2. Egg Contamination: The eggs, which are immediately infectious upon being shed, are then passed into the environment through the feces of the definitive host. The eggs are microscopic and can survive in the environment for extended periods.
   
3. Intermediate Host: The intermediate host (such as rodents) becomes infected when it ingests these eggs from the environment. Once ingested, the eggs hatch in the intestine of the intermediate host, releasing larvae.
   
4. Formation of Metacestodes or Hydatid Cysts:  The larvae, once ingested by an intermediate or aberrant host, can then migrate through the intestinal wall and are carried via the bloodstream to various organs, most commonly the liver. In the liver (and occasionally other organs), the larvae develop into metacestodes or hydatid cysts over several months to years.
5. Aberrant or Dead-end Host: These are hosts that do not contribute to the lifecycle but become infected through ingestion of the infectious tapeworm eggs. Humans are considered aberrant hosts because they develop the disease but do not contribute to the parasite's lifecycle. 
   

​How is E. multilocularis diagnosed?

Depending on the case, E. multilocularis can be diagnosed through using imaging techniques, serological tests, biopsy, fecal examination, and molecular diagnostics. These are used in tandem with the evaluation of clinical signs and symptoms​.

How is E. multilocularis treated?

It is complex and difficult to treat wildlife infected with E. multilocularis. Treatment strategies typically focus on reducing infection rates rather than directly treating infected wildlife. In some cases, anthelmintic drugs (anti-parasitic medications) may be used to treat infected animals, although this approach is generally more feasible in captive or semi-captive settings rather than in wild populations. Other treatment strategies include reducing wildlife densities in endemic areas, implementing measures to prevent wildlife's contact between with humans and domestic animals, and promoting wildlife health through habitat management and disease monitoring.

Does E. multilocularis pose a risk to people or other animals?

E. multilocularis is a zoonotic tapeworm that poses a significant risk to both people and other animals.

Definitive Hosts (Carnivores like Foxes, Coyotes and Domestic Dogs)

Wild canids and domestic dogs infected with E. multilocularis typically remain asymptomatic and do not usually develop hydatid cysts. Even while asymptomatic, they still harbor adult tapeworms in their intestines and consequently shed eggs into the environment through their feces. The cysts associated with E. multilocularis larvae develop slowly, and infected intermediate or aberrant hosts may not display any symptoms for up to several years of infection. However, if symptoms do arise, they may include abdominal pain, weight loss, weakness, and indications of liver disease. While E​​​. multilocularis does not typically cause severe disease in wild canids themselves, they play a pivotal role in the transmission cycle of the parasite by perpetuating the transmission of infectious eggs​, which has implications for both wildlife conservation and public health.

Intermediate Hosts (Mammals like Rodents)
Rodents, such as muskrats, mice, vole and rats, are the primary intermediate hosts for E. multilocularis. When rodents ingest the eggs of E. multilocularis, the eggs hatch in the intestine and release larvae (oncospheres). These larvae penetrate the intestinal wall and migrate to various organs, particularly the liver, where they develop into fluid-filled cysts (metacestodes).

Aberrant Hosts (Humans)

Humans are aberrant, or dead-end, hosts of E. multilocularis. Humans can contract the parasite through accidental ingestion of E. multilocularis eggs present in the feces or fur of wild and domestic canines, or in contaminated food and water. Human infections do not contribute to the parasite's lifecycle. Infections of E. multilocularis in people can lead to a disease known as alveolar echinococcosis. This disease can cause the formation of multivesicular cysts primarily in the liver, although other organs may also be affected. If left untreated, alveolar echinococcosis can be life-threatening due to its invasive and destructive nature.​

​How can E. multiocularis be prevented?

Preventing E. multilocularis involves several strategies aimed at reducing the transmission of the parasite, particularly from definitive hosts (such as wild canids and domestic dogs) to intermediate hosts (such as rodents) and accidental hosts (including humans). Here are key preventive mea​sures:

Deworming of Definitive Hosts

Regular deworming of domestic dogs that may act as definitive hosts can help reduce the shedding of E. multilocularis eggs into the environment. This is crucial in areas where these domestic dogs have access to wildlife habitats or where they roam freely. Large-scale deworming of the wild free-ranging canids is not feasible, but could be appropriate for canids who are in a captive setting or undergoing rehabilitation.

Hygiene and Sanitation

Practicing good hygiene, such as washing hands thoroughly after handling domestic dogs or dead wildlife, can reduce the risk of accidental ingestion of parasite eggs. This is particularly important in regions where there is close contact between humans, animals and contaminated environments.

Ensuring proper food handling and cooking practices, particularly when handling and processing wild game, can reduce the likelihood of human exposure to E. multilocularis eggs.

Surveillance and Monitoring    

Surveillance and monitoring for the presence of E. multilocularis is critical to both understanding the distribution and prevalence of this pathogen on the landscape, as well as making informed management decisions to help mitigate the risk of infection in animals and humans.

Public Education

Educating the public, including pet owners, hunters, and communities living in endemic areas, about the risks and preventive measures of E. multilocularis infection helps to slow the spread of the parasite through raising awareness on the importance of deworming protocols and hygiene practices.​