Hookworm Infestation in Dogs and Cats
Overview: Hookworms in Dogs and Cats
Hookworm infestation is the invasion and multiplication of a blood-sucking parasite in the small intestine. Hookworms attach to the intestinal wall with their mouths and feed on a host’s blood. As they feed, their mouth secretes an anticoagulant substance that further promotes bleeding upon attachment or detachment. Hookworms are known for causing blood loss anemia in severe infestations.
Infection can be acquired before birth or during nursing from an infected bitch. Larvae (young hookworms) become dormant in the female dog, reactivated during pregnancy, and subsequently transmitted to puppies through the placenta or mammary glands. This particular process does not occur in cats. Another method of transmission in dogs and cats occurs from ingestion of larva. This can develop when pets are cleaning themselves or from ingesting dirt. Infection can also develop from larval migration through the skin. In this type of infection, after the larvae penetrates the skin, it migrates through the lungs, up the trachea (through coughing), and into the gastrointestinal tract. The larvae then attach themselves to the intestines.
Hookworm infestation is commonly seen in puppies and kittens from two to eight weeks of age and in the geriatric or chronically-ill population. There is no breed or sex predilection, although infection is most commonly seen in crowded and stressful environments such as in shelters, kennels, and cat colonies. Infections are most common in warm, moist climates and environments.
Ancylostoma caninum is the most common hookworm in dogs and cats. Other species of hookworms in dogs include Ancylostoma caninum, Uncinaria stenocephala, and Ancylostoma braziliense. Ancylostoma tubaeforme, Ancylostoma braziliense, and Uncinaria stenocephala (which is uncommon) infect cats.
Hookworms: What to Watch For
Dogs and cats infected with hookworms may display:
- Pale mucous membranes
- Poor growth, body condition, or general unthriftiness
- Excessive thirst
- Poor appetite
- Dark black tarry stools (melena)
- Weight loss
Young, small puppies and kittens who become infected are at highest risk of severe disease. This is due to their smaller overall blood volume. Their immaturity and small size increase the risk for severe life-threatening anemia.
Diagnosis of Canine and Feline Hookworms
A thorough knowledge of a pet’s history and clinical signs is helpful in making a diagnosis. The physical examination results will be dependent on the severity of the infection. Findings may include pale mucous membranes, weakness, dull haircoat, bloody stool on rectal exam, elevated heart rates, and possibly a heart murmur (due to anemia).
Diagnostic tests necessary to confirm a diagnosis of hookworm infestation include:
- Fecal flotation. Fecal flotation is used to document the hookworm eggs (ova) that are released into the intestine and passed in the stool. The characteristic appearance of hookworm ova is ellipsoidal in shape and contains eight-cell morula. It is important to understand that eggs may not be shed consistently in the feces. A negative test in a pet with matching clinical signs should be treated prophylactically. Based on the life cycle, from the time of infection to the time ova appear in the feces can range from 12 to 30 days.
- Fecal antigen testing. This can confirm the diagnosis.
- Complete blood count (CBC). This is recommended if anemia is suspected.
When hookworms are suspected or diagnosed, pet owners should be cautious of the possibility of human transmission. Working in gardens, walking barefoot in contaminated soil or sand, and playing in sand boxes are common modes of transmission.
Treatment of Canine and Feline Hookworms
Puppies or kittens in an environment with a history of hookworm infections should be routinely treated at two-week intervals until weaning. Multiple agents are available to deworm infected pets.
- Pyrantel pamoate, fenbendazole, or ivermectin may be used. Routine deworming is recommended in puppies and kittens with their routine vaccine series.
- To prevent passage of larvae from the infected bitch to puppies, routine deworming is recommended during gestation.
- Kennel, shelter, or cattery hygiene and appropriate disinfection is extremely important in controlling/eliminating infections.
- Dogs and cats who are showing severe clinical signs should be hospitalized and treated to restore fluid and electrolyte abnormalities, and may require blood transfusions if severe anemia develops. Supplementation with iron may be recommended in pets with anemia. Iron supplements may include injectable iron dextran or oral ferrous sulfate.
Zoonosis of Hookworms
Hookworms can infect humans. In fact, according to the Centers for Disease Control (CDC), it is estimated that 576 to 740 million people in the world are infected with hookworms. Hookworm infection leads to a parasite infection called cutaneous larva migrans in humans. The larvae can migrate under the skin and cause raised, red, itchy snake-like tracts that are visible in the skin. The most common sites for infection are the hands, feet, between the toes, and knees.
This parasitic infection is most often transmitted from working in moist soft soil (such as in the garden) or walking barefoot on sandy surfaces (sandbox or beach) contaminated with dog and cat feces. Larvae can live for 3 to 4 weeks in the environment. Hookworm disease in humans can be caused by multiple species including Ancylostoma caninum, Ancylostoma braziliense, and Necator americanus.
It is recommended that all members of the family frequently wash their hands after handling their puppy or kitten, as well as wear shoes outdoors and gloves when gardening.
Prognosis of Pets with Hookworms
The prognosis for pets infected with hookworms is excellent with mild disease and prompt treatment. Severely infected pets with anemia can become very ill and prognosis may be guarded. Aggressive treatment with prompt parasite control and blood transfusion is critical to survival in severe infestations.
Home Care, Control, and Prevention of Hookworm Infections
Home care includes administering all prescribed medication. Be aware of pets who are severely affected and may need support and hospitalization. Concurrent infection with other intestinal parasites is common. Dogs and cats with hookworms may also get roundworms, tapeworms, whipworms, and heartworms. Routine deworming and fecal checks should be performed by your veterinarian during the routine vaccine series.
Prevention measures include the deworming treatment of pregnant dogs under the supervision of a veterinarian. Kennel hygiene is extremely important in the prevention of infection. Sodium borate can be used on concrete and gravel to control infections.
Another method of prevention of hookworms can be achieved by administering monthly anthelmintics (dewormers) made specifically to prevent infection. Hookworm treatments are common in many monthly heartworm prevention medications. Products that contain milbemycin, selamectin, or pyrantel pamoate can provide monthly control.