ANCYLOSTOMA CANINUM: CHARACTERISTICS, MORPHOLOGY, SYMPTOMS - BIOLOGY - 2025

Ancylostoma caninum is a roundworm that belongs to the phylum Nematoda and is found mainly in tropical and subtropical areas of the planet. This is so because those regions are the ones that meet the necessary environmental conditions for their eggs to develop effectively.

As with a large number of nematodes, Ancylostoma caninum requires a host to develop, the dog being the perfect space for this. Inside this it fixes in the intestine and feeds on its blood.

Ancylostoma caninum. Source: See page for author

This parasite is responsible for causing intestinal disorders in dogs and can occasionally infect humans, generating serious skin lesions.

characteristics

-Species: Ancylostoma caninum

Morphology

Nematodes are worms that are cylindrical in shape. Its body is covered by a resistant and protective white cuticle. They have a mouth capsule, which contains about three pairs of teeth.

They have sexual dimorphism, due to which females and males present morphological differences. The female's tail ends straight, while the male's has a structure known as a copulating bag.

Enlargement of the anterior end of Ancylostoma caninum. Source: DPDx - a Web site developed and maintained by CDC (Centers for Disease Control and Prevention)

As with most nematodes, females are larger than males. They measure approximately 16 mm, while males are only 10 mm.

Biological cycle

The biological cycle of Ancylostoma caninum is of a direct type. This means that the infective form of the larvae develops in the environment.

This parasite does not require a vector, but it does require a definitive host. In this case, the host is the dog.

In the environment

The eggs are released to the outside through the feces. Depending on the humidity and temperature conditions of the soil, these can hatch, thus freeing the larvae that are covered by a protective cuticle. This occurs between day 2 and 9 after the eggs have been released.

Later, in an approximate period of about 5 days, the larvae undergo two transformations and pass to the L3 larval stage, that is, the infective form. It is to be understood that the larvae do not remain in the feces, but rather move towards the ground, where they can remain for several days, even weeks, waiting for a host to infect. Of course, as long as the humidity and temperature conditions are ideal (humid and cool).

Once a host appears, specifically a dog, the larvae are able to enter its body and infect it.

Inside the host

The larvae have the ability to enter the host through the skin, mainly through the space between the pads of the legs, which are in constant contact with the ground. They penetrate the hair follicles and join the dermis (the deepest layer of the skin). Then they move through it until they enter an artery or vein, thus attaching themselves to the bloodstream.

They are transported through the blood until they reach the lungs, where they leave the blood and pass to the alveoli. They then ascend through the respiratory tract (bronchioles, trachea bronchi), until they reach the pharynx to be swallowed and thus pass to the digestive system.

Through the esophagus, the larvae reach the stomach and then the intestine. Here they undergo another transformation, thus becoming adult organisms, already capable of producing eggs. The adult parasite attaches to the intestinal wall through the mouth capsule. There it feeds on the blood of its host.

Disease

Ancylostoma caninum is the parasite responsible for an infection in dogs and cats that mainly affects their digestive tract. In humans, it causes a pathology called larva migrans, which is caused mainly by the migration and displacement of the larvae through the tissues of the individual.

Humans are mainly infected by walking barefoot in places where larvae of this parasite can be found. The contagion of an animal to the human being by direct contact between both has not yet been demonstrated.

Symptoms of infection

In dogs

The symptoms that dogs that are infected by this parasite present are the following:

- Anemia, caused by loss of blood in the intestine.

- Coagulation disorders, caused by the secretion of anticoagulants by the parasite.

- Constant liquid stools in which there are often traces of blood.

- Weakness and apathy.

- Dehydration.

- Dark colored stools from blood loss.

- Paleness in the mucous membranes, which is also caused by loss of blood in the intestine.

In humans

The symptoms that humans present are related to the damage caused by the larvae as they move through the tissues, mainly through the skin. The signs and symptoms are:

- Lesions on the skin, which are red lines and represent the displacement of the larvae through the tissues of the epidermis.

- Unbearable itching in the lesions already mentioned.

- Bacterial infections in the initial lesions.

In general, the larvae die in a short time, so there is no opportunity for them to affect internal organs of the individual beyond the skin.

Lesions caused by Ancylostoma caninum on the skin. Source: WeisSagung

Treatment

Taking into account that Ancylostoma caninum is a parasite, the infections it causes are treated with anthelmintic medications. Among the drugs most used to treat the disease are benzimidazoles, emodepside, and endectocides.

As with most parasites, the most commonly used drugs are albendazole and fenbendazole. These drugs act by causing a degeneration and destruction of certain organelles of the parasites, which results in the eventual death of the adult parasites and the larvae produced by them.

References

1. Aiello, SE. (2000). The Merck Veterinary Manual. 5th edition. Ocean Editorial Group.
2. Brusca, RC & Brusca, GJ, (2005). Invertebrates, 2nd edition. McGraw-Hill-Interamericana, Madrid
3. Curtis, H., Barnes, S., Schneck, A. and Massarini, A. (2008). Biology. Editorial Médica Panamericana. 7th edition.
4. Fisher, M. and McGarry, J. (2007) Foundations of Parasitology in Companion Animals. 1st edition. Editorial Intermédica.
5. Hickman, CP, Roberts, LS, Larson, A., Ober, WC, & Garrison, C. (2001). Integrated principles of zoology (Vol. 15). McGraw-Hill.
6. López, J., Abarca, K., Paredes, P. and Inzuna, E. (2006). Intestinal parasites in canines and felines with digestive symptoms in Santiago, Chile. Public health considerations. Medical Journal of Chile. 134 (2).
7. Varela, C., Varela, M. and Pascual, M. (2002). Cutaneous larva migrans: suspected diagnosis and treatment in Primary Care. Medifam. 12 (10).