There are two kinds of canine hookworm that infect dogs – Uncinaria stenocephala and Ancylostoma caninum.
As in the case of roundworm infections, dormant hookworm larvae can be activated in pregnant female dogs, and transmitted to puppies through the placenta or through their mother’s milk.
Dogs can also be infected by accidentally eating hookworm eggs and larvae in the environment.
Another way infection can occur is through larvae penetration of the skin or the lining of the mouth.
When hookworm larvae penetrate the skin, they are carried by the blood to the lungs. The larvae are coughed up and then swallowed to establish residence in the small intestine.
When a dog eats larvae, some of them may migrate through the lungs, but most only penetrate the intestinal wall. A few days later, they return to the gut, where they mature into adults.
Like roundworms, adult canine hookworms produce eggs that are expelled in the feces of infected dogs, and contaminate the environment.
Hookworm eggs survive well in mild temperatures, shade and moist soil or grass.
Although direct sunlight, drying out and freezing will destroy most hookworm eggs, some are extremely resistant to cold temperatures.
Adult hookworms use their “teeth” to attach to the lining of the dog’s small intestine, and suck large amounts of blood.
This can lead to intestinal distress with dog hookworm symptoms like diarrhea, black stools, weight loss, failure to grow properly, white gums, severe blood loss, anemia, and even death.
When larvae enter through the skin, the dog may experience severe itching and discomfort.
A dog who survives an initial attack by hookworms may develop a degree of immunity or tolerance. In this case, the dog may appear normal, even though worms may be present, and eggs may be found by a veterinarian conducting a fecal examination.
Health Risk To People
Dog hookworm infections are zoonotic – and can therefore be transmitted to humans.
People can be infected by accidentally eating hookworm eggs and larvae that are shed in the environment.
Hookworm larvae can also enter the body through the skin. This can occur in sand boxes, beaches and play or work areas where people might come into contact with hookworm larvae.
As they move through the skin, hookworm larvae can cause severe itching and painful, tunnel-like rashes. This is called cutaneous larva migrans, also known as plumber’s itch or creeping eruption.
Until recently, it was believed that canine hookworms did not to pose a zoonotic threat to humans. There have, however, been confirmed cases of enteritis (inflammation of the small intestine) from hookworm infections in young children.
A dog infected with hookworms should be treated with a fast-acting, highly effective and safe dewormer, such as fenbendazole. This should be followed by a second treatment, two weeks later.
In severe cases, blood transfusions and supportive therapy may be required.