Ancylostoma caninum

Ancylostoma caninum is cosmopolitan in warm and temperate climates, especially where there is adequate moisture. (Marquardt, 2000; Olsen, 1974)

The first larval stage lives in the soil where it molts twice and then emerges into its infectious third stage. The third stage juvenile is either ingested, in which case it goes through the stomach and ends up in the small intestine, or it enters via the skin. If A. caninum enters through the skin of the host, it finds its way to the circulatory system which takes it to the trachea. In the trachea, the juvenile is swallowed and ultimately ends up in the small intestine.

In abnormal hosts, such as humans, A. caninum larva cannot remain in the subcutaneous layer of the skin, unable to enter the circulatory system to complete its life cycle. (Marquardt, 2000; Olsen, 1974)

Ancylostoma caninum is usually gray, but appears reddish if there is blood in its alimentary canal. The body is covered by a non-living cuticle that sheds at molts allowing for growth of the nematode. A male is 10 to 12 mm long and 0.36 mm wide; a female is 14 to 20 mm long by 0.5 mm wide and has a pointed tail. The anterior end is bent dorsally so that the arrangement of the hookworm's ventral and dorsal sides are reversed. In the head of the hookworm is an area called the buccal capsule which contains one the mouth and teeth. Ventrally, there is one pair of teeth, each with three points. In the depth of the capsule there is a pair of triangular dorsal teeth and a pair of ventro-lateral teeth. At its posterior end, a male A. caninum has a prominent bursa. The rays inside the bursa are used in identifying species of hookworms, so A. caninum has a particular arrangement of rays in its bursa. The female reproductive organ, the vulva, is found near the junction of the second and last thirds of the body. (Cheng, 1973; Jones, 1967; Marquardt, 2000; Olsen, 1974)

The eggs of Ancyclostoma caninum pass through several larval instars before becoming an adult. In an environment of 23 degrees Celsius, the egg hatches into the first-stage juvenile in the soil in approximately one day. Within four to five days, the cuticle is molted twice and the infective third-stage juvenile emerges. Infection of the host can occur through ingestion or by penetration of the unbroken skin but either way, the parasite ends up in the small intestine of the host. If ingested, A. caninum travels to the stomach of its host, molts, migrates to the small intestine, molts a fourth and final time, and develops to maturity in about 5 weeks. If entrance is via the skin, A. caninum makes its way through the dermal layers and enters the circulatory system which takes it to the lungs. Once in the lungs, A. caninum leaves the capillaries and travels up the trachea where it is swallowed. It then goes through the same cycle that ingested A. caninum go through until it reaches the small intestine.

Copulation occurs within the small intestine and the female worms pass eggs in the feces. Transplacental and transmammary transmission are known for dogs infected with A. caninum. Occasionally, an A. caninum juveniles will penetrate the skin of a human but cannot complete its life cycle in the inappropriate host. The juvenile wanders about in the upper layers of the skin, causing a conditio called dermal larva migrans. (Marquardt, 2000; Olsen, 1974)

Nematode females may produce a phermomone to attract males. The male coils around a female with his curved area over the female genital pore. The gubernaculum, made of cuticle tissue, guides spicules which extend through the cloaca and anus. Males use spicules to hold the female during copulation. Nematode sperm are amoeboid-like and lack flagella.

Copulation for Ancylostoma caninum occurs within the small intestine and the female worms pass eggs in the feces. (Barnes, 1987; Marquardt, 2000; Olsen, 1974)

There is no parental investment beyond egg laying.

Ancylostoma caninum is not a social parasite. The rate of infection is temperature dependent: temperate and warm climates are optimal conditions while cooler temperatures decrease the rate of infection. (Marquardt, 2000)

Nematodes in general have papillae, setae and amphids as the main sense organs. Setae detect motion (mechanoreceptors), while amphids detect chemicals (chemoreceptors).

Females may produce a phermomone to attract males. (Barnes, 1987)

These hookworms live in the small intestines of many animals, predominantly dogs. Other hosts are cats, foxes, wolves, and other carnivores in temperate as well as tropical and subtropical areas. On very few occasions have humans been reported as hosts. Ancyolostoma caninum feeds primarily on the tissue of the small intestine but is also known to suck blood. Adult worms feed at approximately six different sites per day. (Chowdhury and Tada, 1994; Lapage, 1962; Marquardt, 2000; Olsen, 1974; Roberst and Janovy Jr., 2000)

These parasites are probably not preyed on directly, but are ingested from host to host. Larval mortality is high as most of the parasites do not reach appropriate hosts.

These hookworms live in the small intestines of many animals, predominantly dogs. Other hosts are cats, foxes, wolves, and other carnivores in temperate as well as tropical and subtropical areas. On very few occasions have humans been reported as hosts.

It is difficult to assess the economic importance of Ancylostoma caninum because they do not infect animals raised for food or labor purposes very often. Domestic dogs, the most common host, can suffer from anemia. If proper precautions are not taken, pet owners with infected dogs can become the host of Ancylostoma caninum. Since infected dogs pass A. caninum larvae out with their feces, anyone who comes in direct contact with feces can obtain the parasite. For example, if a barefoot child is playing in the yard where his infected dog has passed feces, the larvae of A. caninum can enter the child's body via contact of the feet with the feces. Once in the child, an A. caninum will migrate within the subcutaneous layer of the skin for several months causing a condition called dermal larva migrans. (Marquardt, 2000)