Hookworms (Ancylostoma - Uncinaria) Holly Nash, DVM, MS Veterinary Services Department, Drs. Foster & Smith, Inc.

Hookworms (Ancylostoma and Uncinaria) are one of the most common intestinal parasites of dogs and cats (especially puppies and kittens), and can cause severe disease including anemia and serious diarrhea. Hookworms have either teeth-like structures or cutting plates with which they attach themselves to the wall of the intestine and feed on the animal's blood. Hookworms can cause a skin disease in humans called cutaneous larval migrans. The common names of the hookworms and animals they infect are shown below.   Latin Name Common Name Hosts Infected A. caninum Canine hookworm Dog, fox, possibly humans (intestine) A. braziliense Canine and feline hookworm Dog, cat, fox, man (skin) U. stenocephala Northern canine hookworm Dog, cat, fox A. tubaeforme Feline hookworm Cat   Hookworms are found throughout North America, although A. braziliense is more common in semitropical and tropical areas, and U. stenocephala in the colder north. Their life cycle has an unusual twist – animals can be infected by ingestion of larvae either from contaminated soil or water; by eating an infected transport host; through larvae penetrating their skin, and by larvae infecting fetuses or the young via the uterus or mammary glands. What is the life cycle of hookworms? The adult worms live in the small intestine where they attach themselves and feed on the host's blood. The adults lay eggs that pass out in the feces. In 1-3 weeks, the eggs have hatched and the larvae are released. These larvae are excellent swimmers that travel through raindrops or dew on leaves and vegetation and wait for a dog to come along. The larvae enter a host either by being ingested or by burrowing through the host's skin. Through the Skin: Larvae entering through the skin migrate through the bloodstream to the lungs and trachea, and are coughed up and swallowed. They attach themselves to the intestinal wall and thus complete the life cycle. Through Ingestion: Larvae may be ingested through contaminated food or water, from moist surfaces, or through transport hosts that have been infected by the larvae. Most larvae that are ingested usually pass down to the intestine where they remain. A few, however, may migrate through tissues of the body and ultimately to the trachea where they are coughed up and swallowed. Some larvae will stop their migration midway and encyst in muscles. Through the Uterus or Milk: Larvae that encyst in the muscle can subsequently migrate to the uterus of a pregnant animal and infect the fetuses. They can also migrate to the mammary glands of a lactating bitch and infect nursing puppies. What are the signs and symptoms of a hookworm infection in animals? Hookworms, especially A. caninum can cause severe disease. By feeding on the oxygen-carrying blood of the host, hookworms can rapidly cause anemia. The mucous membranes e.g., gums will appear pale, the animal will become weak, and sometimes black, tarry stools can be seen. Growth in young animals is stunted, and the hair coat may appear dull and dry. Animals may become emaciated and eventually die from the infection. How do hookworms infect humans and what are the signs of infection?   A hookworm produces an anticoagulant in its saliva so the host's blood does not clot at the site the hookworm attaches. If the worm moves from that site to reattach itself at another, the first site may continue to bleed, sometimes seriously. Hookworm larvae can penetrate the surface of a person's skin (usually through bare feet) and migrate through it, causing a disease called 'cutaneous larva migrans' or 'creeping eruption.' The lesions appear as red lines under the skin and sometimes break open at the skin's surface. These lesions cause severe itching. Usually, the larvae will die in several weeks and the condition will disappear. In severe cases, the larvae may make their way through the skin and enter deeper tissues. This may cause lung disease and painful muscles. There have been some reports of humans having intestinal infections with canine hookworms. Generally, these infected people do not show clinical signs of disease. How is an infestation with hookworms in dogs diagnosed? Diagnosis is made by finding the eggs in the feces. In very young animals, severe disease may be present before the adult worms have started to lay eggs. Diagnosis must then be made by evaluating the signs of disease. The eggs of different parasites of horses and deer can easily be confused with hookworm eggs. Sometimes, it is necessary to confine the dog away from any tempting manure or droppings for 24 hours and then repeat the fecal exam. If the eggs are still there, they are most likely hookworm eggs. The adult worms are small, ½ to ¾ inches long, and are rarely detected in the stool because of their size and ability to firmly attach themselves to the intestinal wall. How is a hookworm infection treated in dogs? Most of the wormers that kill roundworms, except piperazine, will also kill hookworms. Common wormers and their effectiveness against hookworms are listed below.   Oral Treatments for Gastrointestinal Parasites in Dogs Ingredient(s) Example Range of Efficacy* Minimum Age/Weight febantel/praziquantel/pyrantel pamoate Drontal® Plus R,H,W,T,F,E > or = to 3 weeks or 2 lbs fenbendazole Panacur, SafeGuard R,H,W,T > or = 6 weeks ivermectin/pyrantel pamoate Heartgard Plus** Tri-Heart Plus** Iverhart Plus** R,H > or = 6 weeks milbemycin oxime Interceptor**, Sentinel** R,H,W > or = 4 weeks or 2 lbs piperazine salts Hartz Advanced Care Liquid Wormer/Sergeants Worm Away R > or = 6 weeks praziquantel Droncit®, D-Worm T,F, E > or = 4 weeks pyrantel pamoate Drs. Foster & Smith ProWormer-2, Nemex-2 R,H > or = 2 weeks epsiprantel Cestex T,F > 7 weeks diethylcarbamazine Only compounded products available R > or = 8 weeks *Efficacy for intestinal worms: R = Roundworms H = Hookworms W = Whipworms T = Taeniid tapeworms F = Flea tapeworms E = Echinococcus granulosus tapeworms **Also prevents heartworm > means greater than   Strategic deworming is a practice recommended by the American Association of Veterinary Parasitologists (AAVP) and the Centers for Disease Control and Prevention (CDC). Puppies* Initiate treatment at 2 weeks; repeat at 4, 6, and 8 weeks of age. For a puppy at increased risk, also treat at 10 and 12 weeks, and then monthly until the puppy is 6 months old. Thereafter, use a heartworm preventive medication that is also effective against hookworms and roundworms. Nursing Dams Treat concurrently with pups. Adult Dogs Treat regularly for prevention. Also monitor and eliminate parasites in pet's environment. Newly Acquired Animals Worm immediately, after 2 weeks, and then follow above recommendations. Many times supportive care must be given, including high-protein diets and iron supplements. In severe cases, blood transfusions may be necessary. What can be done to prevent hookworm infections in pets, breeding animals, and people? To prevent hookworm infections, we need to remember how animals become infected – either through contaminated soil or water, or through their mothers. Treating the Environment: The larvae of hookworms can live several weeks in cool, moist soil, but die rapidly in freezing or hot, dry conditions. Yards and kennels should be cleaned daily. Floors in kennels and dog runs should be impervious, so they are easier to clean. All fecal material should be removed, since organic material will decrease the effectiveness of cleaning solutions. A bleach solution of 3 cups of household bleach to a gallon of cool water should be sprayed or mopped on the area. Any feces in yards should be picked up on a daily basis. Flaming the surface soil can kill the larvae. Gravel runs are best treated with sodium borate applied at the rate of 10 lbs/100 sq. ft. (Sodium borate will kill vegetation.) Medical Treatment and Isolation: As with any infection, animals infested with hookworms should be kept separate from other animals until their infection is cleared. Bitches can be medicated with fenbendazole at a dosage of 25 mg/lb from the 40th day of pregnancy to the 14th day of nursing to kill migrating larvae and greatly reduce the number that can pass to the puppies. Ivermectin given at a dose of 0.25 to 0.5 mg/lb two to ten days before whelping and at 10-day intervals after whelping can also greatly reduce infections in the puppies. Ivermectin, however, has not been approved for this use in dogs. A fecal examination should be performed at the time the puppies are weaned, 4-8 weeks after the last treatment of an infestation, at the time of your animal's annual physical exam, and before females are bred. Some owners choose to worm their animals on a regular basis. Many veterinarians suggest animals be wormed on at least an annual basis. Many heartworm preventives treat or control infections with hookworms and are an important addition to a control program. Look at your heartworm preventive package to see if it is effective against hookworms. To prevent human infection, good hygiene is extremely important. Teach children, especially, to wash their hands after playing and before eating. Do not let children play in areas where dogs or cats may have defecated. Do not allow cats to use sandboxes or the garden as litter boxes. Persons who will have contact with the ground, especially for long periods of time, e.g., plumbers or electricians working in crawl spaces, should place an impervious material between themselves and the ground. (Hookworm infestation in man is sometimes known as 'plumber's itch.' Sunbathers, especially those lying on wet sand or ground may also be at an increased risk of becoming infected. Animals should not be allowed to defecate on beaches, and people should not walk barefoot through the sand