CICLO BIOLOGICO DE TOXOCARA CANIS PDF

Toxocara canis is worldwide-distributed helminth parasite of dogs and other canids. Toxocara canis is gonochoristic, adult worms measure from 9 to 18 cm, are. Frequency of the antibody anti-Toxocara canis in a community along the Os filhotes de cães infectados completam o ciclo em três a quatro semanas de anticorpo IgG antiToxocara canis no sangue ou fluídos biológicos dos pacientes. Para estudar a freqüência da infecção pelo Toxocara canis em crianças de classes Dadas as características do ciclo de transmissão da toxocaríase, é possível . Assim, os dois grupos estudados são representativos das condições de vida.

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Toxocariasis is caused by larvae of Toxocara canis dog roundworm and less frequently of T. Toxocara canis accomplishes its life cycle in dogs, with humans acquiring the infection as accidental hosts. Unembryonated eggs are shed in the feces of the definitive host. Eggs embryonate and become infective in the environment.

Following ingestion by dogsthe infective eggs hatch and larvae penetrate the gut wall. In younger dogs, the larvae migrate through the lungs, bronchial tree, and esophagus; adult worms develop and oviposit in the small intestine.

In older dogs, patent infections can also occur, but larval encystment in tissues is more common.

Frequency of seropositivity to Toxocara canis in children of different socioeconomic strata

Encysted stages are reactivated in female dogs during late pregnancy and infect by the transplacental and transmammary routes the puppiesin whose small intestine adult worms become established. Puppies are a major source of environmental egg contamination. Toxocara canis can also be transmitted through ingestion of paratenic hosts: The life cycle is completed when dogs eat these hosts and the larvae develop into egg-laying adult worms in the small intestine.

Humans are accidental hosts who become infected by ingesting infective eggs in contaminated soil or infected paratenic hosts.

After ingestion, the eggs hatch and larvae penetrate the intestinal wall and are carried by the circulation to a wide variety of tissues liver, heart, lungs, brain, muscle, eyes. While cicl larvae do not undergo any further development in these sites, they can cause severe local reactions that are the basis of toxocariasis.

The two main clinical presentations of toxocariasis are visceral caniss migrans and ocular larva migrans. Diagnosis is usually made by serology or the finding of larvae in biopsy or autopsy specimens. Many human infections are asymptomatic, with only eosinophilia and positive serology.

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In VLM, which occurs mostly in preschool children, the larvae invade multiple tissues liver, heart, lungs, brain, muscle and cause biokogico symptoms including fever, anorexia, weight loss, cough, wheezing, rashes, hepatosplenomegaly, and hypereosinophilia. Death can occur rarely, by severe cardiac, pulmonary or neurologic involvement. In OLM, the larvae produce various ophthalmologic lesions, which in some cases have been misdiagnosed as retinoblastoma, resulting in surgical enucleation.

OLM often occurs in older children or young adults, with only rare eosinophilia or visceral manifestations. The worm was never identified, but the egg size is most consistent with T. The adult worm was never identified in this case.

Object measured approximately 75 toxodara.

Stretched out, the worm measured 7. Close-up of the anterior end biolovico Toxocara sp. Close-up of the anterior end of Toxocara catishowing the three lips characteristic of ascarid worms. Side view of Image C, showing the broad, arrow-shaped alae with striations, characteristic of T.

Close-up of the posterior end of T. Close-up of the posterior end of Toxocara sp. Cross-section of Toxocara sp. Longitudinal section of a Toxocara sp. In this parasitic disease the diagnosis does not rest on identification of the parasite.

Toxocara canis – Wikipedia

Since the larvae do not develop into adults in humans, a stool examination would not detect any Toxocara eggs.

However, the presence of Ascaris and Trichuris eggs in feces, indicating fecal exposure, increases the probability of Toxocara in the tissues. For both VLM and OLM, a presumptive diagnosis rests on clinical signs, history of exposure to puppies, laboratory findings including eosinophiliaand the detection of antibodies to Toxocara. Antibody detection tests are the only means of confirmation of a clinical diagnosis of visceral larva migrans VLMocular larva migrans OLMand covert toxocariasis CTthe most common clinical syndromes associated with Toxocara infections.

The currently recommended serologic test for toxocariasis is enzyme immunoassay EIA with larval stage antigens extracted from embryonated eggs or released in vitro by cultured infective larvae. The latter, Toxocara excretory-secretory TES antigens, are preferable to larval extracts because they are convenient to produce and because an absorption-purification step is not required for obtaining maximum specificity. Evaluation of the true sensitivity and specificity of serologic tests for toxocariasis in human populations is not possible because of the lack of parasitologic methods to detect Toxocara parasites.

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These inherent problems result in underestimations of sensitivity and specificity. When the cutoff titer for OLM cases was lowered to 1: Further confirmation of the specificity of the serologic diagnosis of OLM can be obtained by testing aqueous or vitreous humor samples for antibodies.

When interpreting the serologic findings, clinicians must be aware that a measurable titer does not necessarily indicate canjs clinical Toxocara canis infection. In most human populations, a small number of those tested have positive EIA titers that apparently reflect the prevalence of asymptomatic toxocariasis. Treatment information for toxocariasis can be found at: DPDx is an education resource designed for health professionals and laboratory scientists.

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Toxocariasis

Life Cycle Toxocara canis accomplishes its life cycle in dogs, tosocara humans acquiring the infection as accidental hosts. Image Gallery Toxocara sp. Eggs are not clinically diagnostic for human cases. Humans are paratenic hosts for Toxocara spp. Toxocara eggs are subspherical, thick-shelled and have a pitted surface.

The size range diclo the three most commonly observed species differs slightly: Toxocara canis larva beginning to hatch.

They also possess large cervical alae with striations. Laboratory Diagnosis Laboratory Diagnosis In this parasitic disease the diagnosis does not rest on identification of the parasite. Antibody Detection Antibody detection tests are the only means of confirmation of a clinical diagnosis of visceral larva migrans VLMocular larva migrans OLMand covert toxocariasis CTthe most common clinical syndromes associated with Toxocara infections.

Antibody reactivity in human toxocariasis. Institute of Biology and the British Society for Parasitology; Treatment Information Treatment Information Treatment information for toxocariasis can be found at: Get Email Updates To receive email updates about this page, enter your email address: December 18, Page last updated: December 18, Content source: Linking to a non-federal site does not constitute an endorsement by HHS, CDC or any of its employees of the sponsors or the toxoccara and products presented on the site.