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​?

Wild canids and domestic dogs infected with E. multilocularis typically remain asymptomatic and rarely develop internal cysts unlike in the intermediate rodent hosts and non-target, dead-end hosts. 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. The life cycle and transmission of the parasite typically occurs in the following manner:

1. Life Cycle: The life cycle of E. multilocularis​ involves two hosts: a definitive host (usually canids such as foxes, coyotes, or domestic dogs) and an intermediate host (typically small mammals like rodents.
   
2. Definitive Host: In the definitive host (coyotes, foxes, domestic dogs)​, adult tapeworms reside in the small intestine. These tapeworms produce eggs, which are shed in the host's feces.
   
3. Egg Contamination: The eggs 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. These eggs are immediately infectious upon being passed in the feces of the definitive host (canid).
   
4. 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.
   
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 that develop disease but do not contribute to the parasite's lifecycle.
   
6. 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.
   

​How is E. multilocularis diagnosed?

Depending on the case, E. multilocularis is diagnosed through a combination of imaging techniques, serological tests, biopsy, fecal examination, molecular diagnostics, in combination with  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 contact between wildlife and humans or 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, Domestic Dogs)

Wild canids and domestic dogs infected with E. multilocularis typically remain asymptomatic, harboring adult tapeworms in their intestines and shedding eggs into the environment through their feces. Canids do not typically develop hydatid cysts. These animals play a crucial role in the parasite's life cycle by perpetuating the transmission of infectious eggs. The cysts associated with E. multilocularis larvae develop slowly, and infected intermediate or aberrant hosts 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. 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, which has implications for both wildlife conservation and public health.

Intermediate Hosts (Rodents, Humans)
Rodents, such as muskrats, mice, voles, 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).

Humans are aberrant or dead-end hosts of E. multilocularis, contracting the parasite through accidental ingestion of E. multilocularis eggs present in the feces or on the 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 would be appropriate in a captive setting or animals 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 understanding the distribution and prevalence of this pathogen on the landscape and making informed management decisions to help mitigate the risk of infection in both animals and humans.

Public Education

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