Ancylostoma caninum

Description

Ancylostoma caninum is found rarely in the UK but it is a major pathogen of dogs in many warmer and tropical regions of the world and it may be encountered in dogs that have travelled under the Pet Travel Scheme. A. caninum may be recognised on examination under a microscope by its large buccal cavity which contain three pairs of teeth along its anterior and ventral edges. Two smaller teeth are also present at the base of the cavity. The life-cycle of A. caninum is detailed elsewhere but it should be noted that L3 larvae of this species mainly enter by the transcutaneous route so that intestinal disease and blood loss are mainly seen in younger animals.

Pathogenesis

A. caninum may cause disease in the following ways:

• The adult A. caninum is an avid blood-sucker, removing up to 0.1 ml of blood from the small intestinal wall every day. Heavy infections may occur when puppies ingest large numbers of L3 larvae from the milk of an infected dam or if they are exposed to a heavily contaminated environment and affected animals may show severe clinical signs, including:
  • Severe acute anaemia which may occur in the prepatent period (before eggs are present in the faeces).
  • Chronic anaemia that results in depletion of iron reserves, especially in older puppies.
  • Severely affected animals may show poor growth and body condition.
• All hookworms may cause dermatitis, particularly in older animals which have developed some local cutaneous immunity and are able to kill invading larvae in the skin.

Control

Most conventional anthelmintic products licensed for use in dogs and cats (such as praziquantel and pyrantel) will clear infection by hookworms and it is a requirement of the Pet Travel Scheme that animals returning to the UK are treated with praziquantel 24-48 hours before entering the UK.

Zoonotic Potential

A. caninum is capable of infecting humans, producing a disease called cutaneous larva migrans. The L3 larvae penetrate the skin and migrate for up to two weeks before they are killed by the development of an immune response. The larvae are acquired in tropical locations where bare skin comes into contact with sand or warm moist soil. The larvae are thought to lack the collagenolytic enzymes that would allow them to penetrate into the dermis and complete their life-cycle and instead, they continue to migrate in the superficial layers of the skin at a rate of up to 2 cm per day. Small serpiginous (snake-like) tunnels may be seen to radiate from the initial point of penetration. The disease is usually treated with thiabendazole. This disease is one of several referred to as cutaneous larva migrans, with other causes including migration of avian schistosome, Strongyloides westeri and papillosus and Pelodera strongyloides larvae.