Monday, October 29, 2012

Are you and your loved ones at risk???

Several years ago I was presented with a bunny named "Sally" that had what looked like a huge growth on her inner was larger than her head!!

When the following directive came across my desk I thought of her:

"Dear Doctor,

Recently, in the national news there has been information regarding mounting evidence that the tapeworm Echinococcus multilocularis (E. multi) may be spreading amongst coyote and fox populations in Canada. This has some researchers concerned about spill-over of this infection into dog and human populations where there is urban-wildlife interface.

Some types of E. multi infections can cause serious health problems in human and animal populations (e.g. cyst formation), however the risks for such an infection are low - only a handful of cases in humans have been diagnosed in North America.

Risks can be minimized by:

  • Proper handling of dog and wildlife feces and proper handwashing
  • Controlling rodents and preventing pets from catching and eating rodents
  • Preventing dogs from eating wildlife feces
  • Routine deworming should kill E. multilocularis and if a dog is at a particularly high risk, more regular testing and treatment may be indicated
This information is being distributed by the Canadian Veterinary Medical Association for the benefit of all veterinarians in Canada."

"Sally" had not read that the risk was low...she was infected with E. multi.  Fortunately for her the huge, multi loculated cyst had formed under her skin and not in her abdomen, chest or brain! If it had developed in these tissues she would not have survived. We opened the cyst and removed the tapeworm. It was sent to a laboratory for identification and was confirmed to be E.multi. Once the offending metacestode and brood capsules (cyst) was removed the cyst resolved and "Sally" went on to live to old age.

How did "Sally" get the cyst? 

She lived in doors but on nice days would go about the garden under the watchful eye of her owner. She loved to nibble on grass and other naturally growing green treats. However, when "Sally" and her owner were not about the garden was also frequented by coyotes. It is assumed that the grass was contaminated with tapeworm eggs that were deposited with coyote feces.

Just the other day my husband mentioned that he had never seen so many coyotes on our property. He commented that they must like blackberries as the feces were riddled with blackberry seeds. It is a concern as even if you pick up the visible fecal matter the eggs are tiny and can cling to the vegetation or get into the soil. Our dogs chase off coyotes every day! They are at risk!

There are many different types of tapeworms that can cause serious health problems, including death, in man and animals. E.multi is one of the nastier ones.

The tapeworm life cycle involves a stage where it resides in the intestinal tract and a stage where it encysts in other tissues. With E. multi the problem isn't the worm living in the intestinal tract. The adult worms live in the intestinal tract of the "definitive host"which, in North America, are primarily foxes and coyotes and as now realized occasionally domestic dogs. Most of the time definitive hosts live in balance with the tapeworm parasite that resides in their intestines. The worms mature and produce huge numbers of tiny eggs that pass out of the host in the stool. Small animals, such as rodents (mice, voles etc) ...and the"Sallys"in our lives...may ingest the eggs either from nibbling on the feces or the vegetation contaminated by them. The parasite then develops into a cyst within the body of the "intermediate host". If the infected small animal is eaten by a fox, coyote or potentially a dog then the parasite continues its life cycle and becomes a new adult tapeworm in the intestinal tract of the "definitive host".

Rodents, dogs, rabbits, humans  etc as "intermediate hosts" with cysts
When it comes to humans, and some other domestic species (your pet), the health problem is what happens when tapeworm eggs are ingested. As in rodents (as a natural host they usually develop smaller cysts that do not kill them) the ingested eggs hatch and the immature parasites migrate through the intestinal wall. From here they can spread to virtually any place in the body!! They develop cysts which can be huge (as in "Sally's " case) and, unlike her , if they are situated in major organs the result can catastrophic if not deadly. Treatment is difficult, prolonged and expensive. Death rates are high!

The relationship between dogs and E. multi is quite interesting. The can act as "definitive hosts" passing eggs in the stool and they can act as "intermediate hosts" developing large tissue cysts which can be devastating.This has been seen and written up in both BC and Alberta. It is not someone else's is our concern.

The increase in urban coyote populations putting coyotes and dogs into close proximity increases the risk of pet dogs becoming infected as both "definitive hosts", where the shedding of eggs can impact other animals including humans, and "intermediate hosts" where the pet may become extremely compromised and die. Animals sick with cysts will not be shedding eggs as the cyst stage is not within the intestines.

Fecal egg counts (parasite exams) may detect definitive hosts that are shedding eggs but advanced imaging techniques will likely be require to positively identify an intermediate host with a tapeworm cyst.

To lower the risk for yourself and your pets:
  1. use gloves and wash your hands after cleaning up fecal matter
  2. don't eat poop! Watch that young children, and your pets, don't eat poop
  3. avoid situations where you pet may eat a wild rodent
  4. have routine parasite exams done on your pets feces
  5. worm your pet for tapeworms on a regular basis
  6. allow your veterinarian to do imaging studies if it felt advisable
  7. don't encourage coyotes, rodents and other parasite harbouring animals onto your property

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