There are three species of hookworms that afflict dogs. These parasites are most prevalent in
areas of high temperature and humidity (such as the southern United States),
where conditions are favorable for the rapid development and spread of
Hookworms are small, thin worms about one-quarter to one-half inch (.6 to 1.3 cm)
long. They fasten their mouth parts onto the mucosa of the small intestines and
suck blood and tissue fluids from the host. This can result in severe blood
loss and malnutrition.
All forms of congenital heart disease occur
in dogs. The most common defects
are valve malformations (called dysplasias),valve narrowing (stenosis),abnormal
openings between the heart chambers (septal defects), patent ductus arteriosus,
and Tetralogy of Fallot.
Patent ductus arteriosusis a persistent arterial connection between the
aorta and pulmonary artery that normally closes at birth or shortly thereafter.
In the uterus, the ductus plays an important role in shunting blood away from
There are five routes by which puppies (and adult dogs) can acquire the
Migration through the placenta in utero
Ingesting larvae in mother’s milk
Ingesting larvae in the soil
Direct penetration of the skin (usually through the pads
of the feet)
Ingesting an intermediate host
The majority of serious hookworm infestations in puppies occur during the
first two months of life and are acquired through the mother’s milk. Signs of
illness include bloody, wine-dark, or tar-black diarrhea. Progressive blood
loss may cause these puppies to rapidly sicken and die. Intensive veterinary
management is required.
In adult dogs, the most common routes of infection are ingesting larvae and
larvae migrating through the skin. Some larvae encyst in tissues, while others
migrate through the lungs to the intestines, where they mature into adults. In
two to three weeks the dog begins to pass eggs in her feces. These eggs
incubate in the soil. Under proper conditions, the eggs hatch in 48 hours and
release larvae that are infective in five to seven days.
Dogs with chronic hookworms often have no symptoms. When symptoms do occur,
they include tarry or bloody diarrhea, pale mucous membranes caused by anemia, weight loss and
emaciation, and progressive weakness. Symptoms can appear as early as 10 days
after exposure. The diagnosis is made by finding eggs in the feces. Because
eggs do not appear in the feces for two to three weeks, however, there may be
an interval during which a stool examination is negative and the diagnosis must
be made on the basis of clinical signs.
Most dogs who recover from hookworms become carriers via larvae encysted in
their tissues. During periods of stress or illness, these larvae are released
and a new outbreak of bloody diarrhea occurs as worms appear in the
Treatment: A number of dewormers are highly effective
in treating hookworms. They include Nemex, Panacur, Drontal Plus, Telmintic,
and Vercom Paste. Treatment should be repeated in one to two weeks, because the
initial deworming activates encysted larvae and causes a new crop of adult
worms to appear in 10 to 12 days. A follow-up fecal examination is recommended
to be sure all parasites have been removed.
Prevention: Good sanitation and periodic stool checks with appropriate
deworming will prevent the serious consequences of hookworms. In addition, heartworm preventives such as
Interceptor are also effective against hookworms, ascarids, and whipworms. Heartgard Plus controls
hookworms and ascarids but not whipworms.
Public health considerations: An itchy disease in humans called cutaneous
larvae migrans (creeping eruption) is caused by the hookworm A. brasiliense.
Larvae present in the soil penetrate the skin, causing lumps and streaks
beneath the skin. The condition usually clears up on its own.
WebMD Veterinary Reference from "Dog Owner's Home Veterinary Handbook"