Uncinaria stenocephala

Description

Unlike Ancylostoma caninum, U. stenocephala occurs in cool and temperate climates including that of the UK. The details of the life-cycle are given elsewhere but the infection is mainly acquired by ingestion of L3 larvae and, unlike A. caninum, L3 larvae are not passed to neonates by the trans-mammary route. U. stenocephala can be recognised on examination under a microscope by its large, dorsally curved, buccal capsule which contains cutting plates at the ventral edge. A single pair of small teeth are also found within the ventral capsule. Adults bury their heads deep in the wall of the small intestine and feed on plugs of mucosa.

Epidemiology

The larvae of U. stenocpehala require moist conditions for development to the L3 stage and clinical disease is reported most frequently in dogs kept in wet confined conditions where larvae build up to high levels. Common situations include grass runs, wet concrete pens (especially if the surface is very pitted and able to retain moisture) and in areas contaminated by foxes which also act as definitive hosts. Certain groups of dogs are therefore particularly affected, including greyhounds in densely-populated racing kennels, fox hounds, sheepdogs and dogs in rural environments. Since eggs also require warmth for development, most infections are also seen in summer.

Clinical Disease

Since adult worms are mucosal plug feeders, anaemia is not usually a feature of infection with U. stenocephala and most infections are asymptomatic. Where clinical signs are seen, the follwoing patterns may be expected:

• Protein-losing enteropathy caused by loss of protein to adults feeding in the small intestine.
• Dermatitis caused by the cutaneous migration of L3 larvae that are killed before they are able to enter the blood. Larvae which penetrate the skin rarely develop to maturity even in young naive puppies but they will cause reactions in older animals that have become sensitised by previous exposure, especially on the paws and elbows.

Control

Animals should be housed in conditions to prevent the build up of infective larvae and it is especially important that concrete runs are dry and well-maintained. Many of the anthelmintics licensed for use in dogs will clear hookworm infection (including praziquantel and pyrantel) and it is best to treat in the Spring when parasite burdens will be at their lowest.

Zoonotic Potential

Like A. caninum, U. stenocephala may be a cause of cutaneous larva migrans in humans. 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.

Kingdom	Animalia
Phylum	Nematoda
Class	Secernentea
Order	Strongylida
Superfamily	Ancylostomatoidea
Family	Ancylostomatidae
Genus	Uncinaria
Species	U. stenocephala