Pet Sense (Archives)
Zoonosis:
This month we’ll give you the insight you need to know about zoonosis (various diseases that are able to be transmitted from animals - both wild and domestic - to humans). There are quite a few, so we’ll focus on two parasites (giardia and tapeworms).
Giardia:
What are Giardia?
Giardia are sometimes confused with worms because they invade the gastrointestinal tract and can cause diarrhea. They are not worms; instead, they are one-celled parasites classified as protozoa.
Most dogs and cats that are infected with Giardia do not have diarrhea or any other signs of illness. When the eggs (cysts) are found in the stool of a dog without diarrhea, they are generally considered a transient, insignificant finding. However, in puppies and debilitated adult dogs, they may cause severe, watery diarrhea that may be fatal if left untreated.
Infection is relatively rare in healthy cats. It is more common in densely-populated groups of animals, such as in a cattery, pet store, or animal shelter. Also, kittens have been shown to shed more Giardia cysts in their feces than older cats.
How did my dog get Giardia?
Pets become infected with Giardia when it swallows the cyst stage of the parasite (could be from eating stool from another animal that has Giardia). Once inside the dog’s intestine, the cyst goes through several stages of maturation, and eventually pass cysts in their own stool. These cysts lie in the environment and can infect other animals. They may also be transmitted through drinking infected water.
What are the clinical signs?
These microscopic parasites attach themselves to the intestinal wall and cause an acute (sudden-onset) foul-smelling diarrhea. The stool may range from soft to watery, and occasionally contains blood. Infected animals tend to have excess mucus in the feces. Sometimes, vomiting can occur too.
How is giardiasis diagnosed?
Giardia is diagnosed by performing a microscopic examination of a stool sample. The cysts are quite small and usually require a special floatation medium for detection, so they are not normally found on routine fecal examinations. A blood test is also available for detection of antigens (cell proteins) of Giardia in the blood. This test is probably more accurate than the stool exam, but it requires several days to get a result from the laboratory performing the test.
How is giardiasis treated?
Once diagnosed, the typical drug used to kill Giardia is metronidazole, an antibiotic-type drug. It is given for 5-7 days. Other drugs are also used if diarrhea and dehydration occur.
Can humans become infected with Giardia?
Giardia can also cause diarrhea in humans. Therefore, environmental disinfection is important. The use of chlorine bleach, one cup in a gallon (500 ml in 4 liters) of water, is effective if the surfaces and premises can be safely treated with it.
TAPEWORMS:
What are tapeworms?
Tapeworms are a parasite that attaches to the small intestinal wall by hook-like mouthparts. Adult tapeworms may reach 8 inches in length. The adult worm is actually made up of many small segments about 1/8 inch long. As the tail end of the worm matures, the terminal segments break off and pass into the stool. Occasionally, the mobile segments can be seen crawling near the anus or on the surface of a fresh bowel movement. These segments look like grains of rice and contain tapeworm eggs; the eggs are released into the environment when the segment dries.
How did my dog get tapeworms?
Animals must swallow a flea that contains tapeworm eggs, in order to become infected with tapeworms (this is the most common tapeworm, called Dipylidium). When pets chew or lick its skin as a flea bites; the flea is then swallowed. As the flea is digested within the animal’s intestine, the tapeworm hatches and anchors itself to the intestinal lining.
Dogs and cats can also become infected with tapeworms when they eat a small mammal, usually a rodent, that contains the parasite (this type of tapeworm is called Echinococcus).
What kind of problems do tapeworms cause?
Tapeworms are not highly pathogenic (harmful) to your pets. They may cause debilitation (loss of energy) and weight loss when they occur in large numbers. The adult worm is generally not seen, but the white segments which break away from the tapeworm and pass outside the body rarely fail to get an owner’s attention.
Occasionally, a tapeworm will release its attachment in the intestines and move into the stomach. This can irritates the stomach, causing the animal to vomit the worm. When this happens, a worm several inches in length will be seen.
How is tapeworm infection diagnosed?
A tapeworm infection is usually diagnosed when the white, mobile segments are seen crawling on your pet or in the stool. Tapeworms are not usually detected by the routine fecal examination performed by the veterinarian. Because of this, veterinarians depend on the owner to notify them of possible tapeworm infection in the dog.
How are the tapeworms treated?
Treatment is simple and, fortunately, very effective. A drug which kills tapeworms can be given topically, orally, or by injection. It causes the tapeworm to dissolve within the intestines. Since the worm is usually digested before it passes, it is not visible in your dog’s stool. These drugs are safe and should not cause vomiting, diarrhea, or any other adverse side-effects.
Control of fleas is very important in the management and prevention of tapeworm infection. Flea control involves treatment of your pet, the indoor environment and the outdoor environment where they reside. If your pet lives in a flea-infested environment, reinfection with tapeworms may occur in as little as two weeks. Because the medication which treats tapeworm infection is so effective, return of the tapeworms is almost always due to reinfection from the environment.
If one pet has tapeworms, should we assume they all do?
No, just because one pet in the household has swallowed an infected flea does not mean they all have. Our recommendation is to deworm only the pets who have obvious tapeworms.
Are tapeworms infectious to people?
Yes, although infection is not common or likely. A flea must be ingested for humans to become infected with the most common tapeworm of dogs. Most reported cases have involved children. The most effective way to prevent human infection is through aggressive, thorough flea control. The risk for infection with this tapeworm in humans is quite small but does exist.
Echinococcus tapeworms are of more concern. These tapeworms cause very serious disease when humans become infected. Hunters and trappers in the north central United States and south central Canada may be at risk for infection by this worm if strict hygiene is not observed. Rodent control and good hygiene are important in preventing the spread of this disease to humans. As with the more common tapeworm, infection with Echinococcus is infrequent but still possible.
