DIPYLIDIUM CANINUM: CHARACTERISTICS, CONTAGION, SYMPTOMS - BIOLOGY - 2025

Dipylidium caninum is an animal that belongs to the class Cestoda of the phylum of flatworms and that presents the classic morphology of these; a flattened and segmented body.

It has been known for quite some time, having been described for the first time by the famous Swedish naturalist Carlos Linnaeus. However, who deepened his study was the so-called father of parasitology, the German Karl Leuckart.

Dipylidium caninum. Source: Alan R Walker

This parasite is widely distributed throughout the world and to infect its hosts, it requires the flea as an intermediary, which is why most of its definitive hosts tend to be cats and dogs.

characteristics

-Species: Dipylidium caninum

Lifecycle

The life cycle of Dipylidium caninum is somewhat complex, since it includes the intervention of two intermediate hosts, such as the flea and a mammal such as the dog or the cat.

Outside the host

It is important to remember that the Cestoda class worms have proglottids, some of which are gravid, that is, they contain a large number of eggs, protected by an embryonic cover.

These proglottids are released into the environment by two mechanisms. They can be dragged in the feces, in the form of small chains and also come out through the anus spontaneously.

Once exposed to environmental conditions, the proglottids undergo a process of disintegration and release the eggs that are contained in them. There in the environment are the larvae of the intermediate host, the flea.

Intermediate host

The flea larvae, which can be those that affect cats or dogs, ingest the eggs. For this process to be successful, it is essential that the flea is in its larval stage, since when it reaches adulthood, its digestive structures do not allow the ingestion of solid particles.

Inside the flea, the parasite undergoes a transformation and becomes the oncosphere, which is the next larval stage. Oncospheres are characterized by having a spherical shape and presenting cilia around them, as well as having hook-like structures, which allow them to penetrate the intestinal wall of their host.

There, it continues its development and reaches the next stage, which is that of cysticercoid. It is worth mentioning that this is the infectious stage of this parasite, so if it is ingested by its definitive host (mammal), it can infect it.

Inside the host

Definitive infection occurs when fleas that are infected by cysticercoids are ingested by the animal, primarily a dog. Already inside this host, cysticercoids travel through the digestive tract until they reach the small intestine.

Here, the parasite, with the help of the specialized structures found in its cephalic portion, anchors itself to the intestinal wall and begins to feed on the nutrients that its host ingests.

The dog is the main host for ipylidium caninum. Source: Pixabay.com

Thanks to this, the parasite successfully completes its development and reaches sexual maturity, then begins to produce proglottids that contain a large number of eggs inside.

Later, as with the rest of the cestode parasites, the terminal proglottids begin to detach and be expelled through the host's anus to start the cycle again.

Humans can be an incidental part of the cycle when fleas infected with cysticercoids are accidentally ingested. This is more common than is believed, especially among infants, since as the dog is a domestic animal, they tend to handle them and come into contact with the feces of these animals.

Disease

Dipylidium caninum is the parasite responsible for a disease known as dipylidiasis, which is common among domestic animals such as cats and dogs, although it also affects humans.

This parasite has an approximate incubation period of 3 to 4 weeks. That is the time it takes for the parasite to become an adult and begin to produce eggs.

Contagion

As already explained, this parasite enters its hosts through the ingestion of fleas that contain the larval stage of the parasite called cysticercoid. Dogs and cats can ingest it by licking their fur. While the human being can do it when handling their pets.

The contagion from person to person is totally ruled out.

Symptoms

In general, Dipylidium caninum infection can be asymptomatic, so there are no warning signs that warn of the presence of this parasite during its early phase.

However, as the parasite takes hold and anchors in the intestine of its host, it begins to cause certain discomforts that eventually translate into certain symptoms. Because it is an intestinal parasite, the main symptoms affect the digestive tract. These include:

-Epigastric pain

-Occasional diarrhea

-Flatulence

-Constipation

-Abdominal distension

-Vomiting

-Sickness

-Loss of appetite

-Anal pruritus, generated by the presence of the proglottids in this area.

-Pain in the anal opening.

-Involuntary weight reduction, because the parasite feeds on the nutrients that its host ingests.

There are also other signs and symptoms that are derived from the discomfort caused by this parasitosis, such as:

-Insomnia

-Irritability

-Decay

-Fatigue

-Restlessness

Diagnosis

As with most intestinal parasites, the definitive diagnosis is made by direct observation of the eggs or proglottids in the feces of the infected person.

When the doctor suspects that a patient is infected with an intestinal parasite, the test he performs is an analysis of stool, which seeks to identify if there are eggs in them, in order to later make a differential diagnosis.

In the case of Dipylidium caninum, proglottids are seen in the stool. These should undergo a histological analysis to be able to observe the egg packets inside and in this way to confirm the infection by this parasite.

Treatment

The treatment scheme for Dipylidium caninum infections is quite simple, using an anthelmintic drug known as praziquantel.

This medicine has several mechanisms of action that neutralize parasites. First, it acts at the level of the cell membrane, altering the flow of ions such as calcium. This results in the parasite's musculature being affected, causing problems in its contraction and relaxation.

What praziquantel does is generate a muscle spasm in the parasite that causes it to be unable to move and ends up dying.

It is worth noting that three months after taking the treatment, it is important to undergo a new stool test, to be able to check if the infection was controlled.

References

1. Ayala, I., Doménech, I., Rodríguez, M. and Urquiaga, A. (2012). Dipylidium caninum intestinal parasitism. Cuban Journal of Military Medicine. 41 (2).
2. Curtis, H., Barnes, S., Schneck, A. and Massarini, A. (2008). Biology. Editorial Médica Panamericana. 7th edition.
3. Hickman, CP, Roberts, LS, Larson, A., Ober, WC, & Garrison, C. (2001). Integrated principles of zoology (Vol. 15). McGraw-Hill.
4. Hogan, K. and Schwenk, H. (2019). Dipylidium caninum New England Journal of Medicine. 380 (21).
5. Neira, P., Jofré, and Muñoz, N. (2008). Dipylidium caninum infection in a preschool. Case presentation and literature review. Chilean Journal of Infectology. 25 (6)
6. Smyth, J. and Mc Manus D. (1989). The physiology and biochemistry of cestodes. Cambridge University Press.