Veterinary Medicine - May 2008 - (Page v3) are not a good screening tool for Dipylidium infection. Preventing zoonotic infections These control measures can help control zoonoses: • Institute regular deworming programs with broad-spectrum anthelmintics • Conduct annual fecal examination, followed by appropriate antiparasitic treatment • Follow strict flea and tick control for pets and their environments • Recommend that clients: —Dispose of cat and dog feces daily —Cover children’s sandboxes when not in use —Reduce their pet’s predatory behavior (e.g., keep cats indoors) —Feed cooked, canned, or dry pet food —Prevent pets from drinking from toilet bowls —Wash or cook vegetables for human consumption —Thoroughly cook all meat for human consumption —Adequately wash their hands after contact with anything contaminated by dog or cat feces. Source: Companion Animal Parasite Council. Members speak out. Available at: www.capcvet.org/?p=MembersSpeakOut_ Article07&h=0&s=6. Accessed February 26, 2008. Q: What is the life cycle of Taenia species? Kevin Kazacos: The life cycle of Taenia species involves other mammals. Infected dogs and cats shed Taenia proglottids in their feces, just like with Dipylidium, but then other mammals acquire the organism by ingesting the eggs. The eggs hatch in that mammal and the larvae migrate into organs, usually the liver, and grow to form large fluid-filled larvae. The dog or cat becomes infected again by eating that infected mammal. The larva contains the tapeworm scolex—the tapeworm head that attaches to the intestinal wall and generates proglottids. So for Taenia species, carnivorism is necessary for tapeworm transmission back to the dog or cat. Dogs acquire Taenia pisiformis by eating cottontail rabbits, and cats acquire Taenia taeniaeformis by eating infected mice. These are the two most common taeniids we see. Other Taenia species and Echinococcus, which includes zoonotic taeniids, are seen less often but are hard to distinguish from the aforementioned species. As with Dipylidium, Taenia is diagnosed by finding proglottids in the feces, on the rear end, or in the environment of dogs and cats. Q: How common is human exposure and infection? Bowman: Dipylidium infection is probably the most common tapeworm zoonosis in the continental United States. It may be a little less common than it once was, probably because of better flea control. Again, a person becomes infected through ingestion of the intermediate host—the flea—and not ingestion of the stage passed by the dog or cat. Kazacos: With the zoonotic Taenia species and Echinococcus, people become infected with the larval stages, and the method of infection is also different. With Dipylidium, you have to eat the flea and ingest the larvae to become infected with adult tapeworms. With the taeniids, you ingest infective eggs and become infected with tapeworm larvae. It is important to realize that an animal can have infective eggs in its perianal area and fur. Bowman: Unlike hookworms or roundworms, these taeniids are infectious when they come out. Kazacos: That’s correct. With zoonotic taeniids, simple contact and accidental ingestion of those eggs can cause infection, and that is an important distinction. Proper sanitation and handwashing in the clinic are always good ideas, because taeniid infections may be hard to identify with certainty. Q: What is the best way to treat and prevent tapeworms, and is reinfection a problem? Jonathan Cooper: We use praziquantel as our tapeworm treatment and find it to be very effective. Oftentimes, if there is a major flea infestation and potential for reinfection, we readminister the praziquantel. My assumption is that the animals are being reinfected with fleas that transmit the tapeworms, so generally I discuss flea control with the pet owner. Little: Reinfection is very common. In fact, many practitioners will prescribe a second treatment of praziquantel two weeks after the first treatment. The initial treatment is fully effective for the current infection, but it takes some time to get a flea problem under Q: What are the effects of tapeworm infection on dogs and cats? Dwight Bowman: Usually we think of adult tapeworms as fairly benign in dogs and cats. But there are reports of impactions, sometimes fatal, in young puppies with Dipylidium infection. I have an article in press on Taenia taeniaeformis in cats causing impaction that required surgery and removal of the worm.1 Although these cases occur, they are often not reported. http://www.capcvet.org/?p=MembersSpeakOut_Article07&h=O&d=6 http://www.capcvet.org/?p=MembersSpeakOut_Article07&h=O&d=6
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