Echinococcus granulosus

February 22, 2012 | Filed under: Research | Posted by: LWW

Echinococcus granulosus in Gray Wolves and Ungulates in Idaho and Montana, USA

Abstract

We evaluated the small intestines of 123 gray wolves (Canis lupus) that were collected from Idaho, USA (n=63), and Montana, USA (n=60), between 2006 and 2008 for the tapeworm Echinococcus granulosus. The tapeworm was detected in 39 of 63 wolves (62%) in Idaho, USA, and 38 of 60 wolves (63%) in Montana, USA.

The detection of thousands of tapeworms per wolf was a common finding. In Idaho, USA, hydatid cysts, the intermediate form of E. granulosus, were detected in elk (Cervus elaphus), mule deer (Odocoileus hemionus), and a mountain goat (Oreamnos americanus). In Montana, USA, hydatid cysts were detected in elk. To our knowledge, this is the first report of adult E. granulosus in Idaho, USA, or Montana, USA. It is unknown whether the parasite was introduced into Idaho, USA, and southwestern Montana, USA, with the importation of wolves from Alberta, Canada, or British Columbia, Canada, into Yellowstone National Park, Wyoming, USA, and central Idaho, USA, in 1995 and 1996, or whether the parasite has always been present in other carnivore hosts, and wolves became a new definitive host. Based on our results, the parasite is now well established in wolves in these states and is documented in elk, mule deer, and a mountain goat as intermediate hosts.

Source: Echinococcus granulosus in Gray Wolves and Ungulates in Idaho and Montana, USA

How Can Humans, Pets, and Livestock Become Infected With Hydatid Disease?

Livestock grazing in areas where wolves may have left egg infested feces may become infected. Anyone who lives, works, recreates, owns pets, and gathers food from areas where Hydatid Disease exists in wild animal populations bears a risk of infection. Hunters, trappers, taxidermists, veterinarians, wildlife professionals, ranchers, farmers, and others who handle animals in areas where wild animals are infected with these parasites bear a higher risk of infection.

Causal Agent:

Human echinococcosis (hydatidosis, or hydatid disease) is caused by the larval stages of cestodes (tapeworms) of the genus Echinococcus. Echinococcus granulosus causes cystic echinococcosis, the form most frequently encountered; E. multilocularis causes alveolar echinococcosis; E. vogeli causes polycystic echinococcosis; and E. oligarthrus is an extremely rare cause of human echinococcosis.

Life Cycle:

The adult Echinococcus granulosus (3 to 6 mm long) resides in the small bowel of the definitive hosts, dogs or other canids. Gravid proglottids release eggs that are passed in the feces. After ingestion by a suitable intermediate host (under natural conditions: sheep, goat, swine, cattle, horses, camel), the egg hatches in the small bowel and releases an oncosphere that penetrates the intestinal wall and migrates through the circulatory system into various organs, especially the liver and lungs.

In these organs, the oncosphere develops into a cyst that enlarges gradually, producing protoscolices and daughter cysts that fill the cyst interior. The definitive host becomes infected by ingesting the cyst-containing organs of the infected intermediate host. After ingestion, the protoscolices evaginate, attach to the intestinal mucosa , and develop into adult stages in 32 to 80 days.

The same life cycle occurs with E. multilocularis (1.2 to 3.7 mm), with the following differences: the definitive hosts are foxes, and to a lesser extent dogs, cats, coyotes and wolves; the intermediate host are small rodents; and larval growth (in the liver) remains indefinitely in the proliferative stage, resulting in invasion of the surrounding tissues.

With E. vogeli (up to 5.6 mm long), the definitive hosts are bush dogs and dogs; the intermediate hosts are rodents; and the larval stage (in the liver, lungs and other organs) develops both externally and internally, resulting in multiple vesicles. E. oligarthrus (up to 2.9 mm long) has a life cycle that involves wild felids as definitive hosts and rodents as intermediate hosts. Humans become infected by ingesting eggs , with resulting release of oncospheres in the intestine and the development of cysts , , , , , in various organs.

Geographic Distribution:

E. granulosus occurs practically worldwide, and more frequently in rural, grazing areas where dogs ingest organs from infected animals. E. multilocularis occurs in the northern hemisphere, including central Europe and the northern parts of Europe, Asia, and North America. E. vogeli and E. oligarthrus occur in Central and South America.

Source: CDC http://dpd.cdc.gov/dpdx/html/Echinococcosis.htm

More Resources and Information:

Echinococcus granulosus has been reported in California, Arizona, New Mexico, and Utah.

Humans become infected when they swallow eggs in contaminated food. The infection is carried to the liver, where cysts form. Cysts can also form in the:

Brain
Bones
Kidney
Lungs
Skeletal muscles
Spleen

Risk factors include being exposed to:

Cattle
Deer
Feces of wolves
Pigs
Sheep

Symptoms

A liver cyst may produce no symptoms for 10 – 20 years until it is large enough to be felt by physical examination.

Symptoms include:

Pain in the upper right part of the abdomen
Bloody sputum
Chest pain
Cough
Fever
Severe skin itching

Possible Complications

The cysts may break open (rupture) and cause severe illness, including:

Fever
Low blood pressure
Shock

The cysts may also spread throughout the body.

PREVENTIVE MEASURES:

1. Wear plastic gloves whenever handling wild game, especially carnivores.
2. Avoid exposure to infected feces, do not touch, kick, or disturb carnivore feces.
3. Consider affects of livestock grazing on the ground in areas inhabited by infected wolves or foxes.
4. Do not let pets roam freely in areas known to be inhabited by infected wolves or foxes.
5. Obtain and use an effective dog wormer on dogs that may have been exposed to wolf or fox feces.
6. Cook wild game well before eating.
7. Do not collect or eat wild fruits or vegetables picked directly from the ground.
8. Wild-picked foods should always be washed carefully or cooked before eating.
9. Fence in gardens to keep out wild animals and pets.
10. Do not allow pets to eat wild animal or livestock offal.
11. Watch children do not touch pets which could be infected, children put their hands in their mouths.
12. Use caution allowing pets in your home (any which could have had any chance of being infected).