Ancylostoma (Hookworm)

Hookworms of Dogs and Cats

The families Ancylostomidae, whose members are com­monly called hookworms because of the characteristic hook posture of their anterior ends, are responsible for widespread morbidity and mortality in animals pri­marily due to their blood-sucking activities in the in­testine.

Ancylostoma:

Major Specie	Host	Location/Site	Distribution
Ancylostoma caninum	Dog and fox.	Small intestine	World wide in the tropics and warm temperate areas.
A. tubaeforme	Cat
A. braziliense	Dog and Cat

Identification

Gross:

• They are readily recognized on the basis of size (1.0-2.0 cm), being much smaller than the common ascarid nematodes which are also found in the small intestine, and by their characteristic 'hook' posture.

Microscopic:

• The buccal capsule is large with marginal teeth, there being three pairs in A. caninum and A. tubaeforme and two pairs in A. braziliense.

Ancylostoma caninum

Life Cycle

The life cycle is direct and given optimal conditions the eggs may hatch and develop to L₃ in as little as five days.

                                                                                F/H becomes by two ways

infecInfection is by ingestion by L₃

	Directly pass to the intestine and de­velop to potency.

 

PPP: 14-21 days (For any route)

Note:

• The worms are prolific egg layers and an infected dog may pass millions of eggs daily for several weeks.

Epidemiology

• In endemic areas, the disease is most common in dogs under one year old.
• In older animals, the gradual de­velopment of age resistance makes clinical disease less likely, particularly in dogs reared in endemic areas whose age resistance is reinforced by acquired immunity.
• The epidemiology is primarily associated with the two main sources of infection, transmammary in suckled pups and percutaneous or oral from the environment.
• Transmammary infection for a period of 3 wks after whelping by L₃ which remain dormant in skeletal muscle until the bitch is pregnant. (incase of percutaneous and penetration of oral mucosa)
• Infection of the bitch on a single occasion has been shown to produce transmammary infections in at least three consecutive litters.
• It also appears that dormant L₃ in the muscles of both bitches and dogs can recommence migration months or years later to mature in the host's intestine.
• Stress, severe illness or repeated large doses of corticosteroids can all precipitate these apparently new infections in dogs.
• experimentally, L₃ of some strains of A. caninum exposed to chilling before oral administration have been shown to remain in arrested development in the intestinal mucosa for weeks or months. The significance of this observation is still unknown, but it is thought that such larvae may resume development if the adult hookworm popula­tion is removed by an anthelmintic or at times of stress such as lactation.

Pathogenesis

·         This is essentially that of an acute or chronic haemorrhagic anaemia.

·         The disease is most commonly seen in dogs under one year old and young pups, in­fected by the transmammary route, are particularly susceptible due to their low iron reserves.

·         Blood loss starts about the eighth day of infection when the im­mature adult has developed the toothed buccal cap­sule which enables it to grasp plugs of mucosa containing arterioles. Each worm removes about 0.1 ml of blood daily and in heavy infections of several hundred worms, pups quickly become profoundly anaemic.

·         In lighter infections, common in older dogs, the anaemia is not so severe, as the marrow response is able to compensate for a variable period.

·         Ultimately however, the dog may become iron deficient and de­velop a microcytic hypochromic anaemia.

·         In previously sensitized dogs, skin reactions such as moist eczema and ulceration at the sites of percutaneous infection occur especially affecting the interdigital skin.

Clinical Signs:

In acute infections characterized by:

• anaemia and lassitude (lethargy)  and
• occasionally respiratory embarrassment.
• In suckled pups the anaemia is often severe and is accompanied by diarrhoea which may contain blood and mucus.
• Respiratory signs may be due to larval damage in the lungs or to the anoxic effects of anaemia.

chronic infections characterized by:

·         underweight, poor coat, and inappetite and perhaps pica.

·         Inconsistently, there are signs of respiratory embarrassment, skin lesions and lameness.

Diagnosis:

• Clinical History with epidemiology
• Clinical signs
• Coproscopy:
• High faecal worm egg counts are valuable confirma­tion of diagnosis
• pups may show severe clinical signs before eggs are detected in the faeces
• Haematological test

Treatment:

• Anthelmintics therapy, such as mebendazole, fenbendazole and nitroscanate, (all of which will kill both adult and developing intesti­nal stages)
• avermectins. (can kill both adult and larva)
• If the disease is severe, it is advisable to give parenteral iron and to ensure that the dog has a pro­tein-rich diet. Young pups may require a blood transfusion.

Control:

• A system of regular anthelmintic therapy and hygiene should be adopted.
• Weaned pups and adult dogs should be treated every three months.
• Pregnant bitches should be dosed at least once dur­ing pregnancy and the nursing litters dosed at least twice, at 1-2 weeks of age and again 2 weeks later (This will also help to control ascarid infections.)
• The perinatal transfer of both Ancylostoma and Toxocara larvae may be reduced by the oral adminis­tration of fenbendazole daily from 3 weeks before to 2 days after whelping.
• Kennel floors should be free of crevices and dry and the bedding should be disposed of daily.
• Runs should preferably be of tarmac or concrete and kept as clean and dry as possible; faeces should be removed with a shovel before hosing. If an outbreak has occurred, earth runs may be treated with sodium borate which is lethal to hookworm larvae, but this also kills grass. A second possibility which is often "used in fox farms is the provision of wire-mesh flooring in^Lthe runs.

A. tubaeforme:

The life cycle and treatment of this hookworm of cats are similar to that of A. caninum in the dog, but there is no evidence of transmammary infection.

A. braziliense:

This hookworm occurs in both dogs and cats. Its life cycle is similar to that of A. caninum although evi­dence of transmammary infection is lacking. While it may cause a degree of hypoalbuminaemia through an intestinal leak of plasma, it is not a blood sucker and consequently is of little pathogenic significance in dogs, causing only mild digestive upsets and occasional diarrhoea. Treatment is similar to that for A. caninum.

The main importance of A. braziliense is that it is regarded as the primary cause of cutaneous larva migrans in man. This lesion, characterized by tortuous erythematous inflammatory tracts within the dermis and by severe pruritus, is caused by infective larvae of A. braziliense, and less frequently Uncinaria, penetrat­ing the skin and wandering in the dermis. These larvae do not develop, but the skin lesions usually persist for weeks.Similar lesions, although only transient and pin­point, may be caused by A. caninum larvae.