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Symptoms |Getting rid of Them
What is Hookworm?
by Dr. N.J.Hayes, DVM
Hookworm is one of the main internal parasites of puppies, kittens, dogs and cats. The others are coccidia, roundworm, whipworm,and tapeworm.
Hookworm infection is very serious for the following reasons:
- Hookworms live on the blood of the host, thus depriving it of necessary nutrients
- Hookworms can be transmitted to unborn puppies
- Hookworm is a zoonotic parasite - they can infect humans
There are 4 hookworm species in the United States and Canada. A. braziliense, Uncinaria stenocephala, Ancylostoma caninum, and A. tubaeforme. A. tubaeforme bothers cats, A.braziliense and Uncinaria stenocephala bother both dogs and cats, and A. caninum lives in dogs. A. braziliense occurs only in the warmer temperatures of the south, while the others occur both in the south and the north. Uncinaria stenocephala causes the least problems to pets; and Ancylostoma caninum is the worst, mainly settling in the small intestine of dogs. Both A.caninum and A. tubaeforme can cause severe anemia, however, hookworm infection is not as common in cats as it is in dogs, and is usually less severe.
How does my pet get hookworm?
Hookworms are very tiny (about 1/8 inch), and have several ways of entering a new host as a larvae.
- The hookworm may penetrate the skin of the host wherever the pet touches infected ground. This may cause rashes and cysts at the point of entry.
- If your pet walks on contaminated soil, the larvae can attach itself to the feet and your pet ingests them when it is licking and cleaning itself.
- Hookworm larvae may be present in soil or on leaves, sticks, etc that a pet eats while digging or playing
- The larvae may be ingested by a pet while hunting and eating prey that is infected or has hookworm larvae on it.
- Hookworm can enter puppies through their mother
- If the mother dog is infected, there may be larvae all around and on her. Also, pregnancy hormones cause the larvae that have formed cysts to wake up and migrate to the unborn puppies and the mammary glands.
Some puppies will be born infected and some will become infected while drinking colostrum from their mother's teat. Some will be infected from larvae in the litter box. Puppies born infected may be shedding eggs in their stool within 2 weeks of birth.
What is the life cycle of the Hookworm and how to they eat?
The hookworm is so serious because of its life cycle and feeding method.
 After arriving inside the host, the larvae develop six sharp teeth and travel to the small intestine. Some will settle there, but others burrow through and migrate to the lung tissue. Those that reach the lungs will develop into adults, burrow back out into the trachea. Then they're coughed up to be swallowed again and travel back to the intestine.
 Some of the larvae go dormant while burrowing through organ walls and form cysts. Most eventually emerge to complete their migration.
The adults that live in the small intestine hang onto the wall with their teeth and drink the hosts blood. (Other species of worms simply absorb the hosts' digested food through their skin.) They spend their lives drinking the blood and mating. The active worms leave bite marks that continue to seep blood where they've been. When the female produces eggs, the eggs are released into the intestinal contents to be passed out with the stool.
The eggs hatch in the environment and develop through three larval stages before they're ready to infect a new host. The eggs and larvae will die if exposed to the sun and drying out.
The typical life cycle - from the time your pet ingests the original larvae to the adult worm shedding eggs - is three weeks. Your pet may keep reinfesting itself by licking in the eggs while it's grooming; or your child may pick up the eggs on their hands while petting the dog or cat.
How do I know if my pet is infected? Are there symptoms?
The best way to assure yourself that your pet is hookworm free is to have your veterinarian check a stool sample on an annual basis. They'll also check for any other parasites.
Some symptoms of heavy infestations are severe anemia with pale muceous membranes and gums. Some pets may become weak, suffer weight loss or have black, tarry stools. Adults get bloody diarrhea, cramping, vomiting and weight loss, in addition to anemia. The pet may or may not have diarrhea. If hookworms are common in the area, pets may show signs of skin disease from the larvae burrowing through the skin as the pet lays on the ground.
Hookworm infection is frequently fatal to young puppies who need all of their red blood cells for rapid growth and really can't spare any for the worms. Puppies may look healthy at birth, but be deadly sick within two weeks. A badly infected puppy may need a transfusion and iron supplements to keep it alive, as well as treatment to rid it of the worms.
How is it treated?
There are several products available to deworm pets. Your veterinarian is familiar with all of the deworming products and will recommend the one that he/she feels is best for your particular pet. You will probably be asked to repeat the treatment in 2 to 3 weeks, because the treatment can only kill the worms that are in the intestinal tract. Any worms that are still encysted or migrating through the pet's body won't be affected.
If the mother didn't receive treatment before pregnancy, the puppies will need repeated treatments to rid them of the infection. This should be started as early as 2 weeks after birth and may continue up to 3 months. Kittens do not get prenatal infection, so the treatment may start at three weeks old and continue up to 9 weeks. The mothers should be treated at the same time as the babies to prevent recurrence and further environmental contamination.
It cannot be stressed enough that it's important to treat the females before the pregnancy starts. Preventing the hookworm from ever infecting the puppies is easier, cheaper and safer than deworming them afterward. Many puppies don't have their first exam until they are 12 weeks old. This means that the families of these pets may already be contaminated with hookworm from handling and petting.
If your pet is on a heartworm prevention medication, it is being treated for hookworms on a monthly basis. This also serves as protection for the families of these pets. In addition, cleaning up the stools daily and having your veterinarian check for hookworm eggs every few months should prevent any infestation from becoming too severe.
References:
- Tilly, Larry.P.DVM, Smith, Francis Jr.DVM, The 5 Minute Veterinary Consult Canine and Feline,Williams & Wilkins, 1997
- Center for Disease Control, website, Guidelines for Veterinarians: Prevention of Zoonotic Transmission of Ascarids and Hookworms of Dogs and Cats
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