Internal Parasites in Pets and Humans, Part 2

In part one of this article, we explored the three types of parasites that can infect both humans and animals. In this article, we will summarize two common internal parasites that can cause your pet to become ill. These two were chosen because of their prevalence and the fact they can be spread to humans.

Giardia 
Giardia are protozoal parasites that live in the small intestines. Giardia are found everywhere in the world. Infection rates are variable, with younger animals having a higher rate of infection. There are various strains that differ in their potential to cause disease.

The strain called Giarda lamblia (also called intestinalis or duodenalis) is the primary strain that invades people, companion animals and livestock. This parasite can be found during fecal exams of healthy pets that don't have any symptoms. It is probably underdiagnosed because of the chronic nature of the problem it presents and the difficulty of coming up with a positive diagnosis. Giardia exists in two forms: trophozoites and cysts. Trophozoites are the active and motile form and are the stage that lives in the intestines of an affected mammal. They produce nonmotile cysts that are cast off into the environment. The cysts remain viable in the environment for months, especially in cool and moist areas. They thrive in clear and cool water, a good reason not to drink running water in the outdoors no matter how pristine it looks. The cysts are killed by freezing, boiling and extended contact with disinfectants.

It is theorized that Giardia make pets prone to food allergies. By interfering with the intestinal lining, they let in proteins that stimulate the immune system to cause an allergic reaction. In many pets, there aren't any symptoms, while in others that do show symptoms, the problem might resolve by itself. The most susceptible pets are puppies and kittens, ones with other internal parasites, and debilitated pets. Diarrhea that occurs can be severe and can be accompanied by poor appetite and dehydration. Vomiting, weight loss and blood in the stool are occasional symptoms.

Giardia can be hard to diagnose because the parasite cysts become shriveled in the routine fecal solution that is used to bring eggs to the surface and adhere to the cover slip for viewing on amicroscope. Special fecal flotation solutions (zinc sulfate) are amore accurate manner to make the diagnosis. Cysts can be shedintermittently, so several samples are sometimes needed to make this diagnosis.

Fresh fecal samples that are not put in the fecal solution can sometimes show the parasite. We sometimes send fecal solutions to our outside lab for special tests when we suspect the problem, yet we may not find the parasite. Just like Coccidia, our doctors might treat for this disease even on negative fecal samples.

Flagyl is the drug routinely used to treat Giardia, although it does not cure all Giardia infections. The usual course of therapy is five days, although our doctors will vary this dose depending on specific circumstances. Other medications are sometimes used if the Flagyl is not effective, but in reality, there is no drug that is 100 percent effective against Giardia.

We recommend treating pets that are positive for Giardia even if they don't have any symptoms. This helps eliminate environmental contamination and minimize the spread to people. If one pet in a household has Giardia, we recommend treating all pets. .

Roundworms
A common parasite of dogs and cats, especially puppies and kittens, is the roundworm. The scientific name for their group is Ascarid. We routinely treat puppies and kittens for this parasite for two reasons: its prevalence and its potential for infesting humans. The larval form of this parasite may cause serious disease in children. Fortunately, it is not a common problem and can be prevented by worming all puppies and kittens early in life.

The life cycle of this parasite almost ensures that a puppy or a kitten will be exposed. Dogs can get it from their mother while they are in the uterus; puppies and kittens can contract them during nursing and through contamination by infected feces. Larval forms of this parasite migrate through internal organs, get coughed up and swallowed, and become mature parasites in the small intestines. Intermediate hosts like rodents can become infected by eating eggs and can then infect dogs or cats that eat them.

roundcycle

Life cycle of a roundworm

Some larvae migrate to the tissues of internal organs and remain dormant until pregnancy, whenthey become active and infect the developing puppies in the uterus. Common symptoms are a distended abdomen and diarrhea. Some puppies and kittens will vomit, become lethargic, and not eat well, while others will not show any symptoms. On rare occasions, the parasite,load can be so heavy that the intestines become obstructed. Coughing, fever, nasal discharge and even pneumonia can occur in,pups that have large numbers of larvae migrating through their respiratory tract.

In some cases, the roundworm will be present in your pet's feces or vomitus. It looks like a curled-up piece of spaghetti. The vast majority of roundworm infestations are diagnosed during fecal analysis for eggs. Young puppies can be infected before the eggs of the parasite appear in the feces.

There are several effective treatments for roundworms. Your pet can easily be treated with an oral version administered during a routine office visit. It has to be retreated in two weeks because of the migrating larvae that the medication does not kill. Some pets require several more treatments for a full cure.

To learn more about these internal parasites and many other parasites, please visit the worm page on our web site.

Some of the information in this article is courtesy of the Centers for Disease Control and Prevention.  



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