VET CHECK: INTERNAL PARASITE CONTROL: CONTROLLING THE MONSTERS INSIDE YOUR DOG

This summer my son and I are living on a quiet, remote island in the Pacific Northwest. My son, who is eight, is especially pleased about this change of scenery because the house we are sharing has a television. A working, larger-than-life, high-definition digital television. He is pleased about this because back when analog TV became obsolete our family opted not to replace our ancient and enormous box. I mean, really, where we live in Alaska it is difficult enough to get the local channels much less the cable networks. I hardly miss the old machine. Not surprisingly the warm electronic glow of this new screen on my deprived child makes it nearly impossible to peel him away from the tube and out into fresh air. However, that was before Animal Planet aired a new episode of Monsters Inside Me. You know, the gruesomely shocking expose about parasites happily residing within humans. Pictures and sound effects aside, the narration about goat, cattle, and pork parasites was enough to send one little third grader out of the dining room and onto the porch to finish his hamburger. How handy this topic of parasites has become to me as a mom! In fact, as a veterinarian and mushing mom, internal parasite control is high on my kennel management priority list due in part to the potential for transmission from dogs to humans. Adults and children alike risk roundworm infection simply by handling dogs (and cats) as the sticky eggs will adhere to the animal’s haircoat. Contaminated environments lead to fecal-oral transmission most often in young children whose sense of hygiene is typically unsophisticated. Proper hand-washing will prevent infection. Severe repercussion of human infestation by roundworms includes skin irritation, intestinal disorders, brain and tissue damage, and blindness. The American Veterinary Medical Association and the American Academy of Pediatrics publish helpful information about human parasite infections on their web sites.The threat of zoonosis certainly instills a sense of urgency to remembering to deworm the dogs, but there are many advantages to controlling parasites in the kennel. A strategic deworming protocol not only minimizes parasites in the dogyard for the sake of family members but also improves each dog’s stamina, speed, nutritional efficiency, and overall health. Successful parasite control requires knowledge of regionally prevalent parasite species, their life cycles in the dog, and methods of reducing environmental contamination. Diagnosis, treatment, and prevention are good topics to discuss with your veterinarian to identify specific trouble spots within the kennel. Roundworm species Toxocara canis and Toxocara leonina are the most common intestinal parasite in the sled dog world. Toxocara have thin, smoothly tapered, yellowish bodies and range in size from 1-2 inches to nearly 8 inches long. Mushers often find these highly motile spaghetti-like adult parasites in vomitus or diarrhea from infected dogs and pups. The eggs of roundworms have a tough exterior shell and can endure extreme environments of both freezing temperatures and heat up to 104 degrees F. Toxocara adults lay eggs within the canine intestinal tract that pass in feces onto the kennel soil. Once passed, infective larval stages develop within the eggs in 7-30 days. Dogs pick up these eggs and larvae by eating food off the ground, licking their paws after walking on contaminated soil, or by drinking fecally contaminated water. Alternatively a rodent or other animal may ingest the eggs and become an inadvertant host. The larvae encyst within the muscles and tissue of the transport host and lie dormant until a dog eats the meat.After ingestion of an infective egg the life cycle of the larvae continues. The larvae migrate through the intestine and travel to the liver, respiratory tissue, or in pregnant females, the uterus. Larval migration through the lungs causes coughing and pneumonia in puppies and young dogs. The larvae are coughed into the mouth and reswallowed to begin a new cycle within the dog’s intestine. Extremely significant in sled dog kennel contamination, the uterine tissue in pregnant females is a nidus for roundworm infection as larvae pass into the growing fetuses. Secondarily, pups are infected by large quantities of roundworm larvae when the larvae pass through the mammary glands and milk during nursing. Consequently these pups (and mom) continue the cycle and reinfect the kennel if they are excluded from the deworming program. Hookworms and whipworms are internal parasites found less frequently than Toxocara but which produce more severe pathology in the dog. These parasites, unlike roundworms, attach directly to the lining of the intestine by using piercing mouthparts to suck blood from the host. Anemia from blood loss causes weakness and weight loss, adversely affects the dog’s performance, and predisposes the dog to infections and organ failure. Hookworms move from contaminated soil by direct penetration through the skin or mouth or through oral ingestion. Humans also are at significant risk of hookworm infestation by walking barefoot in contaminated areas, or handling infected dirt without gloves. Whipworms can be tranmitted to dogs or humans by oral ingestion of eggs or larvae. Tapeworm species are familiar to mushers because of the rare but serious threat of Echinococcus zoonosis. Less common than the Dipylidium tapeworm, Echinococcus is a species of tapeworm extremely dangerous to humans. Chronic bone, tissue, and brain infection occurs when an Echinococcus tapeworm egg is consumed by humans. Tapeworm cysts in humans have been fatal. Echinococcus infects wildlife populations such as foxes, game sheep, caribou, and moose in Arctic and northern regions of the world. A sled dog ingests Echinococcus larvae from raw or undercooked meat of infected wildlife (or infected domestic sheep). Fecal-oral transmission occurs to the musher from infected dogs or the raw meat of infected wild game. Dipylidium infects dogs by their direct ingestion of eggs or egg-packet segments found on fleas, lice, or infected rodents. The egg packets are thin, flat, sticky rice-like body parts of the tapeworm that attach near the dog’s perineum. Both Echinococcus and Dipylidium tapeworms are treatable with the anthelmintic praziquantal, an ingredient in Droncit and Drontal-brand dewormers. A number of distance races, including Iditarod, require mushers to deworm their dogs pre-race with a praziquantal product to diminish the passage of Echinococcus to mushers, handlers, and spectators.Consistent diagnostic and control measures in the kennel are necessary to decrease the year-round threat of parasites. Annual fecal sampling and testing is a useful tool in the kennel which is often performed early in the spring or just prior to fall training. Deworming before training, whelping, or transport will decrease detrimental effects of parasites on the dogs during times of stress. A notable point about fecal testing is that samples may be void of eggs during specific stages of the parasite life cycle. It is thus possible for fecal testing to miss larval burdens when no eggs are being shed by adult parasites. Overall however, fecal testing is a consistently helpful method of detecting roundworms as well as a means for identifying giardia and coccidia, two species of protozoa found in sled dog populations. Tapeworms are notoriously difficult to visualize in fecal samples and diagnosis often relies on identifying risk of exposure (raw meat, rodents with fleas/lice) or noting visible egg-packet segments on the host.Definitive diagnosis of specific parasites dictates appropriate treatment protocols in a kennel. Haphazard deworming methods are rarely effective in controlling parasitism in a large group of dogs. Deworming medications affect only the adult stages of intestinal parasites. The first anthelmintic dose administered will kill adult parasites in the intestine at that date, but follow-up deworming doses are necessary to kill still-migrating larvae as they ultimately reach the intestinal tract. Administration of follow-up doses is generally at 2-week intervals and can require up to four doses to clear the dog of the majority of parasites.Anthelmintics effective against roundworms include pyrantel pamoate, fenbendazole, febantel, piperazine, and milbemycin. Piperazine is a drug found in many brands of over-the-counter dewormers. Various brands that contain one or a combination of deworming drugs are available by veterinary prescription. Combination medications conveniently treat multi-species parasite infestations. Pregnant bitches should receive regular deworming during gestation and be administered a pre-whelping dose to decrease the incidence of larval migration during lactation. A post-partum bitch and her neonatal pups should be dewormed with a broad-spectrum anthelmintic every two weeks, often until the pups are 2-4 months old, to effectively treat round, whip, and hookworms. A dose of praziquantel for pups older than four weeks of age is necessary in tapeworm infestations. Doses and safe medications for pups and pregnant dogs vary by drug. Be sure to read the labels of any medication you plan to use in the kennel.Intestinal parasites are so well adapted to the canine host that they continue to re-infect a kennel for years if effective treatment and control measures are not adopted. The tenacity of eggs in the environment as well as the larval tissue migration necessitates a year-round deworming program. Kennels whelping litters are at serious risk for continued reinfection. Racing kennels often deworm every 3-4 months to address these issues as well as the risk of parasite contact from racetracks or from visiting other kennels. Quality kennels remove manure from the dog yard on a daily basis to prevent shed eggs from maturing to infective larval stages in the soil. Dog manure should be disposed of well away from areas of human activity. Deep burial of feces away from water sources, burning, or high-heat composting are options for disposing of dog waste. Information on dog manure composting is available through the University of Alaska at Fairbanks, among other sources. Composting, when done correctly, appears to be a useful method of inactivating parasite ova, and can be useful in regions with high summer temperatures and direct sunlight. Many sources recommend that dog manure compost NOT be used on crops grown for human consumption. Weaving nutrition, training, and health topics seamlessly together to form a practical and efficient kennel-management program is a goal of every sled dog kennel. Deworming can certainly be an undesirable topic to consider and discuss but the beneficial effect of controlling parasites in the kennel is substantial. Perhaps an added advantage; you’ll be the most knowledgeable at the next family viewing of Monsters Inside Me!Sandi Farris graduated from Colorado State University with a DVM in 1995. She started Harmony Veterinary Services in 2000 concetrating in equine and canine sports medicine. She also raised and trained sprint Alaskan huskies with her husband and son as Up A Creek Kennels in Willow, Alaska. She has raced limited sprint dogs and the Womens WC since 1992.

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