environmental assay data sheet

Toxocara PCR test

Test code: X0054 - Ultrasensitive qualitative detection of Toxocara by real time PCR

Toxocara is a genus of parasitic roundworms, or nematodes, that primarily infect the intestines of animals, particularly dogs and cats. The most common species are Toxocara canis, which affects dogs, coyotes, wolves, and foxes, and Toxocara cati, which affects cats and other felids. Toxocara malaysiensis and Toxocara vitulorum are also common pathogens in animals.

These worms have a direct life cycle, with adult parasites living in the small intestine of their definitive hosts, where the female worms can lay thousands of unembryonated eggs daily that are passed in feces. These eggs can remain viable for years in the environment. In general, eggs embryonate over 1-4 weeks (temperature-dependent) to become infective larvae enclosed within the eggs. When a new definitive host ingests these infective eggs from contaminated soil, food, or water, the eggs hatch in the intestine to release larvae which penetrate the gut wall and enter the bloodstream. The larvae migrate to the liver, and to the lungs where they can break into the airways. When the worms are coughed up and swallowed, they return to the small intestine to mature into adults over 3-5 weeks. Sometimes, especially in older hosts, larvae may encyst in muscle, liver or other tissues as dormant stages instead of completing the migration.

Toxocara causes toxocariasis, a infection that occurs when eggs are accidentally ingested from contaminated soil, sand, or feces. While the infection can be zoonotic, humans are considered accidental hosts because the larvae hatch and migrate through tissues but do not mature into adults. This can lead to conditions like visceral larva migrans affecting organs such as the liver or lungs, or ocular larva migrans affecting the eyes and potentially causing vision loss. Many infections are asymptomatic, but severe cases may involve inflammation, pneumonia, or neurological issues. Toxocariasis is more common in children and in tropical or subtropical regions, and prevention involves deworming pets, proper hygiene, and avoiding contact with contaminated areas.

Diagnosis of infection in animals relies mainly on detecting the adult worms or eggs in feces. The sensitivity of this microscopic examination is low, especially if the animals are asymptomatic. Serology detection also has low specificity due to cross-reactivity with other roundworms. Polymerase chain reaction is increasingly used in diagnosis and environmental surveillance due to its high sensitivity and specificity (Otero et al., 2018; Zibaei et al., 2013).

Utilities:

• Check for Toxocara species in feces, water, soil, and other environmental samples
• Selection of appropriate remediation regimens
• Check for post-remediation absence of this parasite
• Help confirm the presence of this parasite in animals
• Help minimize human exposure to this parasite

References:

Otero D, Alho AM, Nijsse R, Roelfsema J, Overgaauw P, Madeira de Carvalho L. Environmental contamination with Toxocara spp. eggs in public parks and playground sandpits of Greater Lisbon, Portugal. J Infect Public Health. 2018 Jan-Feb;11(1):94-98.

Specimen requirements: 2 ml of feces, or 10 ml of water, or used water filter media; or 10 ml of soil; or environmental swabs or swipes.

Contact Zoologix if advice is needed to determine an appropriate specimen type for a specific diagnostic application. For specimen types not listed here, please contact Zoologix to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative real time polymerase chain reaction

Normal range: Nondetected