Tapeworms (Hymenolepis nana and Hymenolepis diminuta)

Test code: X0060 - Ultrasensitive qualitative detection but not differentiation of tapeworm species Hymonolepis nana and Hymenolepis diminuta by real time PCR

Hymenolepis is a genus of cestodes that primarily infects the intestines of rodents, humans and other mammals. There are two major species: Hymenolepis nana (also known as the dwarf tapeworm) and Hymenolepis diminuta (also known as the rat tapeworm). These worms are found worldwide, with H. nana being the major tapeworm that infects humans. People living in temperate zones or children living in areas with poor sanitation are especially susceptible to the infection. Although H. nana mainly infects humans, rodents carrying this parasite have been reported (Hayashimoto et al., 2015).

H. nana adults measure about 15-40 mm long, while H. diminuta can grow up to 20-60 cm. Infection of humans causes hymenolepiasis. The parasite is usually spread via the fecal-oral route by ingestion of eggs in contaminated food and water. Unlike many tapeworms, H. nana has a direct life cycle without the need of an intermediate host. However, insects, such as fleas or beetles, can play a key role in the transmission of Hymenolepis parasites. For H. nana, insects as intermediate hosts are optional, but for H. diminuta, insects are definitely required to act as intermediate hosts. When mature eggs of the parasite are ingested by suitable arthropod intermediate hosts, such as beetles, fleas, mealworms, or other insects that feed on contaminated material, the eggs hatch inside the guts of the insects to release oncospheres (larval forms) that penetrate the intestinal wall and develop into cysticercoid larvae in the insect's body cavity. When humans or rodents accidentally ingest the insects, the parasite will pass on to the host. Prevention of this parasitic infection requires proper hygiene, rodent control, and avoiding consumption of potentially contaminated grains or insects.

The traditional method of diagnosis of this parasite relies on microscopic examination of eggs in the stool smear. Other techniques, such as fecal flotation, are used to increase the concentration of eggs for examination. Serological tests, such as ELISA to detect antibodies, are occasionally used but lack specificity and are not standard due to cross-reactivity with other helminths. Polymerase chain reaction is increasingly used in diagnosis and environmental surveillance due to its high sensitivity and specificity (Al-Jawabreh et al., 2019).

Unlike Syphacia parasites, Aspiculuris tetraptera larvae live in the proximal colon, after hatching in the cecum. A. tetraptera migrate from the proximal to distal colon to deposit eggs. The eggs are then excreted in the feces and are not infective until 5-8 days later. A. tetraptera has a 21-25 day prepatent period.

Infected mice or rats can carry light to medium loads of pinworms with no signs of disease; however, if the level of pinworms is high, animals may suffer from rectal prolapse, enteritis, intestinal impaction, sticky stools, and pruritus (itchy skin).

Pinworm infection has been diagnosed by finding ova using the perianal tape test (Syphacia species only), anal swabbing, or fecal floatation and/or centrifugation. However, the sensitivity of these methods is low. Examination of the cecal and colonic contents is more sensitive, but this method is not suitable for routine screening of rodent colonies or populations. PCR detection of these parasites has been found to be just slightly less sensitive than direct examination of cecal and colonic contents, but more sensitive than the other methods (Dole et al., 2011). Pinworm tissue and eggs are shed intermittently in feces, so testing feces at multiple time points or from multiple individuals at a single time point can be helpful when screening colonies. Because PCR can be performed on fecal samples, it is often more convenient than other techniques for screening rodent colonies

Utilities:

• Shorten the time required to confirm a clinical diagnosis of infestation
• Help ensure that animal populations and facilities are free of these parasites
• Early prevention of the spread of these parasites
• Minimize human exposure to these parasites

References:

Al-Jawabreh A, Ereqat S, Dumaidi K, Al-Jawabreh H, Abdeen Z, Nasereddin A. Prevalence of selected intestinal protozoan infections in marginalized rural communities in Palestine. BMC Public Health. 2019 Dec 11;19(1):1667.

Hayashimoto N, Morita H, Ishida T, Uchida R, Tanaka M, Ozawa M, Yasuda M, Itoh T. Microbiological survey of mice (Mus musculus) purchased from commercial pet shops in Kanagawa and Tokyo, Japan. Exp Anim. 2015;64(2):155-60.

Specimen requirement: 2 ml of feces; or rectal swab; 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 PCR

Normal range: Nondetected