What are hookworms?
Hookworms (Ancylostoma caninum, Ancylostoma braziliense, Uncinaria stenocephala) are intestinal parasites of your pets that get their name from the hook-like mouthparts they use to anchor themselves to the lining of the intestinal wall. They are only about 2-3 mm long and so small that it is very difficult to see them with the naked eye. Despite their small size, they ingest large amounts of blood from the tiny blood vessels in the intestinal wall. A large number of hookworms can cause inflammation in the dog’s intestine, as well as a life-threatening decrease in the number of red bloods cells (called anemia). Anemia is most common in puppies, but can occur in adult dogs.
Hookworms are more common in warm, moist environments. Conditions of overcrowding and poor sanitation contribute to infection.
How do dogs get hookworms?
Dogs may become infected with hookworms by one or all of four routes:
- through the skin
- through the mother’s placenta before birth (in utero)
- through the mother’s milk
Female hookworms pass hundreds of microscopic eggs in the feces of infected dogs, where they contaminate the environment. Larvae hatch from the eggs and can remain infective in the soil for weeks or months. A dog may become infected when it inadvertently swallows hookworm larvae, often by grooming its feet, or from sniffing feces or contaminated soil.
Most larvae that are ingested will move to the intestinal tract to complete their life cycle. A few larvae may make their way into the trachea (windpipe), and are then coughed up and swallowed. The larvae may also burrow into the skin if the dog walks or lies on contaminated ground. Once in the host’s body, the larvae migrate to the lungs and trachea. The dog will then cough up and swallow the larvae which then migrate to the intestinal tract, where they mature and complete their life cycle. Part of the life cycle of the hookworm involves migration through muscle tissues, where they may become dormant (alive, but temporarily inactive).
If a pregnant dog had hookworms in the past, the pregnancy may reactivate dormant larvae, which then enter the female’s bloodstream and infect the puppies in the uterus (prenatal infection). Puppies may also become infected after birth through mother’s milk (transmammary) during nursing. Prenatal and transmammary infections are an important route of infection for puppies.
What are the clinical signs?
The most significant clinical signs are related to intestinal distress and anemia. The parasites anchor themselves to the intestinal lining so that they can feed on tissue fluids and blood, injecting an anti-coagulant substance which prevents the blood from clotting. This can cause continued bleeding after the hookworm has detached from the feeding site. Therefore, the dog can suffer blood loss from the hookworm’s feeding, as well as continued bleeding into the bowel from the attachment sites, causing anemia. Pale gums and weakness are common signs of anemia. Some dogs experience significant weight loss, bloody diarrhea, dull and dry hair coat or failure to grow properly with hookworm infection. It is not uncommon for young puppies to die from severe hookworm infections. Dogs may also exhibit coughing in severe cases.
Skin irritation and itching, especially of the paws, caused by larvae burrowing into and along the skin, can be signs of a heavily infested environment.
Treatment of hookworms infection
There are several effective drugs, called anthelmintics, which will eliminate hookworms. Most are given orally. However, these drugs only kill the adult hookworms.
Therefore, it is necessary to treat an infected dog again in about two to four weeks to kill any newly developed adult worms that were larvae at the time of the first treatment.
In some life-threatening cases, a blood transfusion may be necessary in dogs with severe anemia. It would help to stabilize your dog so that its body will be receptive to other treatments.
All puppies should be treated with a veterinary-approved anthelmintic product at two to three weeks of age. In addition, prompt deworming should be given if the parasites are detected. Regularly deworming may be appropriate for pets at high risk for infection.
Your veterinarian can advise and prescribe with the preventive product for your dog.