Hookworms (ancylostoma) are small and thin worms that can grow to be around a quarter to half an inch (0.6-1.3 cm) long.
There are three species of hookworms that can affect dogs (A. caninum, A. braziliense, and U. stenocephala).
Hookworms have either teeth-like structures or cutting plates with which they fasten themselves onto the small intestinal walls and suck blood from the host. As a result, hookworms can cause severe anemia and malnutrition to dogs.
Life Cycle of Hookworms
- Adult worms that attach themselves to the small intestines of their host lay eggs that pass out in the feces.
- Within 2 to 10 days, the eggs hatch and the larvae are released in the soil where they wait for a suitable host to come along. These larvae are infective in five to seven days.
- The larvae enter a host either by being ingested or by burrowing through the skin of the host.
- Once the larvae reach the small intestines, they mature, mate, and produce eggs, thus completing the life cycle. (Some larvae may migrate to other tissues such as muscle and fat tissues and become dormant.)
There are five ways that a dog can get infected with hookworms.
Five Ways to Get Infected with Hookworms
- Prenatal Infection: Encysted hookworm larvae can lie dormant in fat and muscle tissues in a dog and can subsequently migrate to the uterus. They can then infect an unborn puppy in utero through the placenta.
- Infection While Nursing: Hookworm larvae can also migrate to a bitch’s mammary glands. The larvae can be transmitted to the nursing puppies’ stomach and intestinal tract through the mother’s milk.
- Ingestion of Hookworm Eggs : Puppies and adult dogs can get infected by hookworms by ingesting larvae that are living in the soil.
- Ingestion of an Intermediate Host: Dog can also become infected with hookworms by eating transport hosts that have been infected by the larvae.
- Direct Skin Penetration: Larvae can also enter a host’s body through the skin (usually through the dog’s footpads). They then migrate through the bloodstream to the lungs and trachea, and are coughed up and swallowed. Once they get to the small intestines, they attach themselves to the intestinal wall.
Symptoms of Hookworms in Dogs
Most cases of hookworm infestations occur in puppies during the first two months of their lives. Usually they acquire the hookworms through their mother’s milk.
Puppies with hookworms usually exhibit symptoms such as:
Eventually, the progressive blood loss can cause a puppy to be very sick and die.
Adult dogs suffering from chronic hookworm infestations show no or very few symptoms, such as:
- Bloody or tarry diarrhea
- Signs of anemia such as pale gums and mucous membranes
- Weight loss
- Weakness and lethargy
Diagnosis and Treatment of Hookworms in Dogs
If hookworm infestation is suspected in a dog, a fecal sample is collected to look for hookworm eggs in the sample.
However, because eggs usually cannot be found in the feces for 2-3 weeks, sometimes a stool examination may be negative, in which case diagnosis is made based on the signs and symptoms showned by the dog.
Unlike roundworms, the hookworms are too small to be easily detected in the stool.
There are quite a few dewormers that are effective in treating hookworms in dogs (e.g. Drontal Plus, Panacur).
Usually at least two treatments are necessary – The second treatment needs to be repeated in 1-2 weeks, because the first treatment activates those larvae that are encysted.
As a result, new adult worms will appear in about 10-12 days. After the second treatment, a fecal examination should be done to make sure that all the worms have been eradicated.
Prevention of Hookworms in Dogs
As hookworms can cause serious health problems to dogs, especially to puppies, it is important to prevent hookworm infestations in dogs.
Good sanitation, such as daily cleaning of yards and kennels, combined with periodic stool checks can prevent hookworms from infecting our dogs.
Bitches pregnant with puppies should be dewormed in order to minimize prenatal infection. Additionally, mother dogs should be dewormed after the puppies have been born to reduce the chance of passing the worms to the baby pups while nursing.
Beware of “Creeping Eruption”
The hookworm A. brasiliense can cause a disease in people called cutaneous larvae migrans (creeping eruption). The larvae that are living in the soil penetrate the skin and cause intense itching and skin irritations to people. Don’t walk barefoot outside especially on warm sandy soil!