Echinococcus And The Risk To Our Pets
What is Echinococcus?
Echinococcus is a group of tapeworms. Tapeworms are parasites that live in the small intestines of many different species of animals, including humans.
Echinococcus spp. Is normally transmitted between two different groups of animals: definitive hosts and intermediate hosts.
• A definitive host is an animal that normally carries the adult tapeworms in the intestine and sheds the eggs in its feces. For E. multilocularis, Coyotes, wolves, foxes and dogs are definitive hosts.
• An intermediate host is an animal species that typically harbours the cyst stage of the parasite in the body tissues, and is then eaten by a definitive host. Small prey animals such as voles, mice and lemmings are common intermediate hosts for E. multilocularis
People and dogs can “accidental” be intermediate hosts. People and dogs can be infected with the cyst form if they swallow eggs from the feces of an infected definitive host.
• Since domestic dogs and cats can be infected as definitive hosts, exposure to Echinococcus eggs in their feces is a much higher risk to humans. Preventing infection in pets therefore helps to prevent infection in people. 1
• Echinococcus eggs are immediately infective when they are passed, so even contact with fresh feces is a risk.
• Echinococcus eggs also survive very well in the environment, and can remain infective in soil for up to a year. Individuals who work outside and have contact with soil that may be contaminated with feces from infected animals must be extra careful about washing their hands and preventing any tiny bits of soil from getting in their mouths.
If a human or dog is infected with E. multilocularis it can develop into alveolar echinococcis.
The cysts usually start in the liver but can form and spread elsewhere, ranging in size from that of a sesame seed to a large melon. Although the cysts grow slowly, usually for 5-15 years or more before a person becomes sick, they tend to invade nearby tissues like a cancerous tumor, making treatment very difficult.
• Dogs that roam, hunt or are fed raw offal from potentially infected intermediate hosts (e.g. sheep, moose), and that are infrequently dewormed, are more likely to be infected with Echinococcus spp
In endemic regions, the estimated annual incidence of cystic echinococcosis ranges from less than 1 to 220 cases per 100,000 individuals, and for alveolar echinococcosis it ranges from 0.03-1.2 cases per 100 000 individuals. It is difficult to determine the true prevalence in people because hydatid cysts and alveolar hydatid cysts are often not detected for years after infection.
How do I know if my pet has tapeworms, including Echinococcus?
• Infections in adult animals rarely cause illness, even with large numbers of worms, but the motile proglottids may cause irritation around the anus, causing the animal to chew or rub the area or “scoot”. • Your veterinarian can perform a fecal “float” on your pet to look for eggs of tapeworms (and other parasites) in the feces. It is important to have this done regularly.
It is impossible to tell Echinococcus eggs from the eggs of Taenia tapeworms based on a fecal float. The egg sacs of Echinococcus are distinguishable from Taenia, but they are very small and extremely difficult to find. Newer tests that look for marker molecules (e.g. antigens or DNA) for Echinococcus in feces may help make diagnosing infection easier and more accurately.
Echinococcus eggs may only be shed intermittently and in low numbers by infected pets, so a single negative fecal float cannot completely rule out intestinal infection.
How is infection with Echinococcus in people diagnosed?
• Echinococcus cysts may grow for years, depending on their location, without causing any signs of illness in people. When signs of illness do occur, they depend on where the cyst is and what tissues or organs are being compressed or invaded. Cysts most often occur in the liver, which can lead to abdominal pain and sometimes obstruction of bile ducts and jaundice. Cysts in the lungs may cause coughing (with or without blood), chest pain and difficulty breathing. Cysts in the brain can cause neurological signs and seizures.
• Cysts are often found when tests such as radiographs, ultrasound, CT or MRI are performed for other reasons. A blood test for antibodies to the parasite is often used to help confirm the diagnosis.
• Ultrasound is sometimes used for screening individuals living in high-risk areas, because catching the infection early, typically before anyone knows the cyst is there, helps make treatment much easier and more effective.
How is infection with Echinococcus treated?
In pets, intestinal infections with Echinococcus can be treated just as easily as other tapeworm infections, using an oral dewormer. Nonetheless, if your pet needs to be treated for tapeworms, it is important to also take steps to prevent your pet from being reinfected afterwards.
• Pets may shed very high numbers of parasite eggs for a few days after being treated, so be particularly diligent about removing pet feces promptly and hand washing.
How can I prevent Echinococcus infection in me, my pets & my family?
The two major components of preventing Echinococcus infection in people are preventing intestinal infection in pets and preventing human exposure to the parasite eggs.
• Have your veterinarian check your pet’s feces at least once a year to detect parasite eggs. In Calgary we recommend fecal testing every 6 months. If eggs are detected, treatment with an oral dewormer is safe and usually very effective.
• To prevent infection in pets, do not allow them to hunt or scavenge other animals. Keep cats indoors and prevent rodent infestations in the house. Keep dogs on a leash or at least in sight when outdoors. Do not allow hunting dogs to eat raw offal. Ensure all meat or other animal-based products are properly cooked before being fed to pets, especially if the animal source is from an area where Echinococcus is endemic.
• Pick up pet feces promptly and wash you hands thoroughly afterwards.
• When we pet our animals and then touch our food or our mouths, we ingest the parasite’s eggs. Make sure you wash your hands and thoroughly before eating and after petting.
• If working with soil in an endemic region, especially where the soil may be contaminated by foxes, feral dogs or similar animals, always wear gloves and wash hands thoroughly when done.
What Is The Risk?
Recent studies have not determined the prevelance of E. Multilocularis in Calgary but it is assumed to be around 0.1 to 0.5%. 2
? CDC Public Health Image Library (phil.cdc.gov) 2/4 www.wormsandgermsblog.com Updated July 2013
? Worms and Germs blog: Echinococcus for Owners https://www.wormsandgermsblog.com/files/2008/04/M2-Echinococcus.pdf
? World Health Organization: Echinococcosis http://www.who.int/mediacentre/factsheets/fs377/en/
? Echinococcus flow chart adapted from: