Ancylostoma caninum: Hookworm

General Description: These worms are red or grey, depending on whether or not blood is present in their digestive tracts. Ancylostoma caninum is up to 16mm long and has 3 pair of prominent teeth in its mouth area. The hookworms lay strongyle -type eggs.

Life Cycle: Ancylostoma caninum infects dogs and foxes. Eggs develop to infective larvae, which enter dogs by being eaten, by skin penetration, or by penetrating a rodent transport host which is subsequently eaten. Ingested larvae usually mature without further migration, but larvae that enter dogs by skin penetration usually travel in the circulation through the heart to the lungs, break into the lung tissue, ascend the trachea, and are swallowed before maturing. Some bypass the lungs and invade muscle tissue, where they lie dormant. When an infected bitch gives birth, the previously dormant larvae travel to the mammary gland and enter the milk. After entering the newborn puppies, these larvae mature in the intestines in about a month.

Location: Small intestine.

Significance: Hookworms are very important canine parasites, which cause many deaths in dogs of all ages. Ancylostoma caninum is the most significant, because it causes heavy blood losses, but fortunately is not a common parasite in dogs in New Zealand.  Uncinaria is more prevalent, but much less pathogenic.

Effect on Host: Skin penetration by larvae causes irritation and itching, especially of the paws. The adult hookworms rupture blood vessels of the intestinal wall and feed on the released blood. Each Ancylostoma caninum hookworm may cause the loss of 0.1ml of blood daily. Diarrhoea develops, often dark in colour due to blood and mucus. The severe blood loss causes iron-deficiency anaemia, oedema, weakness, weight loss and poor coat condition. Heavy infections are frequently fatal, often within 2 weeks of birth in puppies.

Diagnostic Information: Characteristic "strongyle-type" eggs present in faeces can be cultured and the typical larvae identified. Adult hookworms can be identified at necropsy.

Control: Faeces should be removed from dogs' quarters. Anthelmintics should be used to treat infected dogs. Supplementary iron will help to combat the severe anaemia produced by these parasites.

A. caninum mouthparts – note 3 pair of teeth		A. caninum – Adult male		Eggs – A. caninum
Note pale membranes – anaemic puppy. Caused by hookworm infection		Blood stained mucus – small intestine		Small intestine, note attached worms