Hookworm

What are hookworms?

Hookworms are parasites which get their name from the hook-like mouthparts they use to attach to the intestinal wall.  They are only about 3 mm long and so small in diameter that you have to be looking very carefully to see them.  Despite their small size, they suck large amounts of blood from the tiny vessels in the intestinal wall.  A large number of hookworms can cause anaemia.  This problem is most common in puppies, but it will occasionally occur in adult dogs.

How did my dog get hookworms?

Dogs may become infected with hookworms by four routes:

 1.         Through the mother’s placenta before birth

2.         Through the mother’s milk

3.         Swallowing hookworm larvae in the milk

4.         Through the skin

If a pregnant dog has hookworms, the pregnancy may reactivate larvae.  These larvae will enter the female’s circulation and pass to the puppy through the placental blood flow.  Puppies may become infected through the mother’s milk.  This is considered to be an important route of infection for puppies.  Finally infection may also be by the infected larvae penetrating the skin and then migrating to the bowel where they complete the life cycle.

What kinds of problems do hookworms cause for my dog?

The most significant problems appear related to intestinal distress and anaemia.  Blood loss results from the parasites sucking blood from intestinal capillaries.  The presence of pale gums, diarrhoea, or weakness might suggest the need to specifically determine the dog’s red blood cell count.  Some dogs experience significant weight loss, bloody diarrhoea, or failure to grow properly with hookworm infection.

Skin irritation and itching can be one of the common signs of a heavily infested environment.  The larvae burrow into the skin and cause the dog a great deal of itching and discomfort.  Kennels can sometimes have a problem with hookworms. 

How is hookworm infection diagnosed?

Hookworms are diagnosed with a microscopic examination of a small faeces sample.  Since there are so many eggs produced on a daily basis, they are rather easily detected. One adult female hookworm is reported to produce as many as 20,000 eggs a day!

In puppies, large numbers of worms usually must be present before eggs are shed into the faeces.  For this reason, faecal examination may be less reliable in very young puppies than in adult dogs. 

How are the hookworms treated?

There are several very effective drugs that will kill hookworms.  These are given by injection or orally and have few, if any, side-effects.  However, these drugs only kill the adult hookworms.  Therefore, it is necessary to treat again in about 2-4 weeks to kill any newly formed adult worms that were larvae at the time of the first treatment.

A blood transfusion may be necessary in some dogs because of the rather severe anaemia which can be produced.

Since the dog’s environment can be laden with hookworm eggs and larvae, it may be necessary to treat it with a chemical to kill them.  There are some available that are safe to use on grass.

Are canine hookworms infectious to people?

Adult hookworms do not infect humans; however, the larvae can burrow into human skin where it causes itching and is called in some countries ground itch. The worms do not mature into adults.  Direct contact of human skin with moist, hookworm infested soil is required.  Fortunately, this does not occur very often if normal hygiene practices are observed.

In rare instances, the canine hookworm will penetrate into deeper tissues and partially mature in the human intestine.  A few reports of hookworm enterocolitis (small and large intestinal inflammation) have occurred in the recent past, particularly in North America. 

 What can be done to control hookworm infection in dogs and to prevent human infection?

1.         All pups should be treated at 2 weeks of age.  This needs to be repeated every 2 weeks until they are 4 months old.

2.         Prompt deworming should be given when parasites are detected; periodic deworming every 3 months is advised for all dogs and cats.

3.         Prompt disposal of dog faeces should occur, especially in yards, playgrounds, and public parks.

4.         Strict hygiene is important, especially for children.  Do not allow children to play in potentially contaminated environments.

5.         Nursing females should be treated at the same time as their pups; nursing may reactivate infection in the female.  Pregnant bitches should be wormed at least twice during pregnancy.

6.         Many of the broad spectrum worm remedies are effective against hookworms. E.g. drontal, interceptor and sentinel.

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