TOXOCARA CATI: CHARACTERISTICS, MORPHOLOGY, INFECTION, TREATMENT - BIOLOGY - 2025

Toxocara cati is a worm that belongs to the phylum Nematoda and, like many of this classification, is a causal agent of infections. Its main host is the cat and some other felines, although humans can also be its host.

It was first described by the German zoologist Johann Zeder in 1800. It was later established that it is the causative agent of toxocariasis, a rare infection in humans that affects certain tissues of the body.

Toxocara cati. Source: Beentree

This parasite is found mainly on the African continent and in some regions of America and is transmitted by ingestion of its eggs.

characteristics

-Species: Toxocara cati

Morphology

Toxocara cati is a roundworm that has a body covered by a cuticle, which is a kind of protective layer. The color can vary from pale pink through white to yellowish. At the level of the cervical area, the worms have fin-like or wing-like extensions.

Enlargement of the cephalic end of Toxocara cati. Source: CDC - DPD

The most developed system is the digestive system, which is complete, with an entrance hole (mouth) and an exit hole (anus). To mobilize, they do so with the help of a hydroskeleton and a system of longitudinal muscles.

They present sexual dimorphism, which means that there are morphological differences between male and female individuals.

The females are larger. They reach a length of approximately 10 cm and their bodies end in a straight tail. While the males are much smaller, measuring 5-6 cm on average, in addition to having a curved tail, which has structures called spicules, which serve it during the mating process.

Biological cycle

The life cycle of Toxocara cati takes place inside its host, which in most cases is the cat. It is worth noting that the cycle as described below occurs mainly in young cats.

This parasite reproduces through eggs. These are released to the outside through the animal's feces.

This is a parasite that requires going through several larval stages until it reaches the adult stage. Inside the egg, the larva develops until the second larval stage (L2). This is a process that can take up to 15 days.

Well, the eggs with the larvae (L2) inside can be ingested by some mammals. In the event of being ingested by an animal other than a cat, what happens there is that they undergo a transformation, the larvae encyst and transform into ineffective larvae, being able to remain there indefinitely.

If they are ingested by a cat, they travel through the digestive tract to the intestine, where the larvae hatch from the egg and manage to cross the intestinal wall, until they enter the circulation. Through this they reach the lungs. There they undergo another transformation and reach the third larval stage (L3).

The cat is the main host of Toxocara cati. Source: Pixabay.com

Later, the L3 larvae migrate through the trachea and reach the oral cavity of the animal, where they are swallowed again.

At the level of the intestine, the L3 larvae transform into stage 4 larvae (L4) until finally reaching the adult stage.

The adult parasite is able to begin to produce eggs, which are excreted in the feces, to start the cycle in another host. The total duration of the cycle is approximately 30 days.

In the case of older cats, what happens is that the second instar (L2) larvae can invade some organs where they can encapsulate and remain dormant for an indefinite time.

Symptoms of infection

In cats

Toxocara cati is a parasite of cats. As such, it generates an infection in them, toxocariasis.

In young cats, which are the ones that most develop the infection, the symptoms and signs that appear are the following:

- Inappetition

- Apathy

- Shaggy hair

- General weakness

- Intestinal obstruction (depending on the number of parasites)

- Diarrhea

- Blood in the stool

- constipation

In the human being

The potential human victims of this parasite are children under the age of 10. This is because they tend to play a lot with their pets, and they are always putting their hands to their mouths.

The symptoms that appear are given by the path that the larvae describes during their migration. Less mild symptoms include:

- High fever

- General discomfort

Finally, when the parasites reach their final destination, which can be the eye or the liver, among many others, they remain even without generating symptoms, but reproducing constantly. Eventually the tissues become inflamed, triggering some symptoms, such as:

- Abscesses in the organs in which they are found (liver, brain)

- Granulomas

- Bronchial problems

- Retinitis due to granulomatosis

- Uveitis

- Eye pain

- Intraocular hemorrhages

Diagnosis

Initially, when nonspecific symptoms are present, it is rare for Toxocara cati infection to be suspected. Due to this, no relevant tests are carried out. However, when symptoms flare up, your doctor may order blood tests that measure IgM and IgG.

When the parasite affects the ocular tissues, the most likely thing is that the doctor decides to perform a biopsy, in which the presence of the worm can be evidenced.

Treatment

The drugs used to treat Toxocara cati infections are anthelmintics that kill the parasites or their larval stages.

Those most commonly used to treat toxocariasis include mebendazole, thiabendazole, and albendazole. Treatment generally does not last more than 10 days.

References

1. Cardillo, N., Rosa, A. and Sommerfelt, I. (2008). Preliminary study on the different stages of Toxocara cati in cats. Latin American parasitology. 63 (4).
2. Curtis, H., Barnes, S., Schneck, A. and Massarini, A. (2008). Biology. Editorial Médica Panamericana. 7th edition.
3. Dubey, J. (1966). Toxocara cati and other intestinal parasites of cats. Veterinary Record. 79.
4. Hickman, CP, Roberts, LS, Larson, A., Ober, WC, & Garrison, C. (2001). Integrated principles of zoology (Vol. 15). McGraw-Hill.
5. Holland, C. and Smith, H. (2006). Toxocara: The enigmatic parasite. CABI Publishing.
6. Huapaya, P., Espinoza, Y., Roldán, W. and Jiménez, S: (2009). Human toxocariosis: public health problems ?. Annals of the Faculty of Medicine. 70 (4).