Hookworms are nematode parasites that live in the small intestines of their hosts, which include cats, dogs and humans. The two most common species of hookworm that infect cats are Ancylostoma braziliense and Ancylostoma tubaeforme. A third hookworm, Ancylostoma ceylanicum, can also cause infections, although it is extremely similar to A. braziliense and difficult to diagnose as a separate infection.
Hookworms suck blood from the host’s intestinal walls. When present in large numbers, they can produce an iron deficiency anemia. This disease is called Ancylostomiasis. Active worms sometimes leave lesions at the site of the bite which may continue to bleed, again resulting in intestinal blood loss. These infections can be fatal, especially in kittens.
Hookworm eggs survive in warm, sandy soil. Generally, they live for only a few weeks under natural conditions. However, if conditions are suitable, they can hatch to become active larvae as quickly as 5 to 7 days. The eggs die almost immediately on exposure to direct sunlight or desiccation. Infection of the host is by the larvae, not the eggs, and the usual method of infection is through the skin. Once inside the host, they are carried by the vascular system to the lungs and from there, they migrate up the trachea and into the pharynx. This often results in the host coughing, whereupon the larvae are swallowed and pass down the oesophagus to enter the digestive system. They make their way to the small intestine where they hook into the mucosal lining. The larvae begin feeding on the host’s blood and eventually develop into adult worms. The adult worms mate inside the host and the female then lays up to 30,000 eggs/day which pass out in the host’s feces. Hookworms are also sometimes ingested. Again, the larvae migrate into the oesophagus and then to the intestine.
The disease becomes communicable to other cats between 2 to 4 weeks after initial infection.
Hookworm infections are caused either by penetration of the skin by the larvae or ingestion. The eggs are usually found in contaminated water on grass or in the soil, or other contaminated environments. After hatching, the larvae typically migrate into the host through the feet when the cat walks on the infected substrate. Kittens can become infected through their mother’s milk.
When hookworm larvae enter the host cat, they often leave small lesions on the foot pads and between the toes – early symptoms of the disease. Another early symptom is repeated coughing. Because the parasite causes anemia, later symptoms can include dark and tarry feces, diarrhea, or constipation. The linings of the nostrils, lips and ears may be pale due to the anaemia. Infected cats will often have an overall unhealthy appearance and poor appetite. Complications can arise quickly and can be fatal if the cat is not treated immediately. Older cats can sometimes carry a low number of hookworms and show little, if any, symptoms. On the other hand, young cats may become very ill with the same sized parasite burden.
Hookworms are small and cannot be seen with the naked eye. A microscopic examination of a fecal specimen is needed to detect the presence of eggs and confirm the diagnosis. When several kittens within a litter have unexpectedly died, hookworms are a potential cause.
Treatment will depend on the age, weight and condition of the cat. To control the infection, de-worming medications will be prescribed. These either kill the worms or cause them to be expelled. Sometimes, this may not be sufficient for long-term infections. Nutritional and iron supplements may also be necessary.
In severe cases, the cat or kitten may be hospitalized for fluid therapy, blood transfusion and supplemental oxygen. Sudden death may occur – even if the cat receives treatment.
For kittens, treatment should begin at 3 to 4 weeks of age followed by monthly treatments.
With pregnant females, treatment should begin 2 weeks after mating. This should continue until 2 to 4 weeks after the kittens are born. This will kill worms in the small intestine and thereby protect the kittens.
To prevent infections, the cat’s environment should be kept clean. This is particularly important for areas in which the cat sleeps or toilets. Particular attention should be given to areas that might accumulate water such as containers, damp (low-lying) areas and even ponds.
There are no inoculations available for ancylostomiasis infections. Prevention of the disease relies on owners being highly observant and quickly seeking advice if symptoms present themselves. Hookworms can be transmitted to humans, so care should be taken when treating infected cats.