Clinical Features:
Iron deficiency anemia (caused by blood loss at the site of intestinal attachment of the adult worms) is the most common symptom of hookworm infection, and can be accompanied by cardiac complications.  Gastrointestinal and nutritional/metabolic symptoms can also occur.  In addition, local skin manifestations ('ground itch') can occur during penetration by the filariform (L3) larvae, and respiratory symptoms can be observed during pulmonary migration of the larvae.

The most common manifestation of zoonotic infection with animal hookworm species is cutaneous larva migrans, also known as ground itch, where migrating larvae cause an intensely pruritic serpiginous track in the upper dermis.  Less commonly, larvae may migrate to the bowel lumen and cause an eosinophilic enteritis.  In some cases of diffuse unilateral subacute retinitis, single larvae compatible in size to A. caninum have been visualized in the affected eye.

Laboratory Diagnosis:
Microscopic identification of eggs in the stool is the most common method for diagnosing hookworm infection.  The recommended procedure is as follows:

1. Collect a stool specimen.
2. Fix the specimen in 10% formalin.
3. Concentrate using the formalin–ethyl acetate sedimentation technique.
4. Examine a wet mount of the sediment.

Where concentration procedures are not available, a direct wet mount examination of the specimen is adequate for detecting moderate to heavy infections.  For quantitative assessments of infection, various methods such as the Kato-Katz can be used.

Cutaneous larval migrans is usually diagnosed clinically, as there are no serologic tests for zoonotic hookworm infections.  Larvae may be seen in stained tissue sections, but this procedure is usually not recommended as the parasites are usually not found in the visible track.

Diagnostic Findings

• Microscopy
• Morphologic comparison with other intestinal parasites

Examination of the eggs cannot distinguish between N. americanus and A. duodenale.  Larvae can be used to differentiate between N. americanus and A. duodenale, by rearing filariform larvae in a fecal smear on a moist filter paper strip for 5 to 7 days (Harada-Mori).  Occasionally, it may be necessary to distinguish between the rhabditiform larvae (L2) of hookworms and those of Strongyloides stercoralis.

Treatment:
In countries where hookworm is common and reinfection is likely, light infections are often not treated.  In the United States, hookworm infections are generally treated with albendazole*.  Mebendazole* or pyrantel pamoate* can also be used.  For additional information, see the recommendations in The Medical Letter (Drugs for Parasitic Infections).  Cutaneous larva migrans is a self-limiting infection but can be treated with albendazole or ivermectin, see recommendations in The Medical Letter (Drugs for Parasitic Infections). Treatment for more severe manifestations of zoonotic hookworm infection include albendazole and surgical removal of the parasite.  There are also recommendations in The Medical Letter available for eosinophilic enteritis caused by A. caninum.

* This drug is approved by the FDA, but considered investigational for this purpose.