environmental assay data sheet

Strongyloides stercoralis (threadworm) PCR test

Test code: X0058 - Ultrasensitive qualitative detection of Strongyloides stercoralis by real time PCR

Strongyloides stercoralis is a parasitic roundworm commonly known as threadworm. This parasite infects humans and causes the disease known as strongyloidiasis. An estimated 30–100 million people worldwide, mainly in tropical and subtropical regions, are infected by this parasite. The parasite is found in contaminated soil and typically enters the body through bare skin, such as the feet, before migrating to the lungs and intestines, where it matures and reproduces.

The parasite is zoonotic, meaning transmission between animals and humans is possible. Dogs can be infected, but clinical disease is often mild or subclinical, and so is more common than recognized due to underdiagnosis. Cats can be experimentally infected, but natural infections are rare and not well-documented. Infections have been detected in non-human primates, with fatal cases reported in some species.

Larvae in feces develop into infectious forms in warm, moist soil. Humans get infected by walking barefoot on contaminated ground, where larvae penetrate the skin. Larvae then travel via the bloodstream to the lungs. Larvae are coughed up and swallowed, then enter the intestine, where they mature into adult worms.

The life cycle of S. stercoralis is unique among soil-transmitted helminths because it can include an auto-infective phase: the parasite can reproduce within a host without needing to exit the body. This can lead to chronic infections lasting decades.

In immunocompromised individuals, such as those on constant corticosteroid treatment and HIV- or HTLV-1-infected individuals, this parasite can cause hyperinfection syndrome, a potentially fatal condition where larvae proliferate massively. However, in most people infections are asymptomatic. When symptoms occur, they may include abdominal pain, diarrhea, nausea, vomiting, skin rashes, and respiratory issues (such as coughing or wheezing). In severe cases, weight loss, malnutrition, or disseminated infection leading to sepsis can occur.

Preventing the infection relies on avoiding contact with contaminated soil by wearing suitable shoes in endemic areas, improving sanitation, and conducting deworming programs in high-risk communities. Screening is recommended for immunocompromised individuals or those from endemic regions before starting immunosuppressive therapy.

Traditional diagnosis involves microscopic detection of larvae in stool samples, duodenal fluid, or sputum, or blood tests for antibodies. PCR detection of this parasite can outperform traditional methods because it can provide sensitive, species-specific detection with minimal sample volume, even in complex matrices where viable eggs might be scarce or degraded (Campo-Polanco et al., 2018; Sanprasert et al., 2019).

Utilities:

• Check for Strongyloides stercoralis in water sources, 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:

Specimen requirements: 2 ml of feces; or rectal swab; or 0.5 ml EDTA whole blood; or 10 ml of soil; or 10 ml of water, or used water filter media; 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