Cysticercosis

Cysticercosis, taeniasis and hydatids are a subset of ‘cestode’ (tapeworm infection) and are all notifiable. Taeniasis and hydatids are discussed in separate chapters.

Tapeworm infection causes two clinical syndromes in humans:

• mature tapeworm infestation in the gut
• larval cysts embedded throughout the body, causing hydatosis, cysticercosis, coenurosis or sparganosis.

Cysticercosis refers to disease in the tissues caused by the larval stage of one species of tapeworm – Taenia solium, otherwise known as the pork tapeworm. Ingested eggs hatch in the small intestine, and the larvae migrate to various tissues and organs, particularly in the central nervous system (neurocysticercosis), and form cysts. These eventually degenerate and become calcified granulomata.

Taeniasis (discussed separately) refers to intestinal infection by adult tapeworms of the genus Taenia (for example, T. saginatum, T. solium).

More detailed epidemiological information is available on the Institute of Environmental Science and Research (ESR) surveillance website.

Cysticerci can cause symptoms by compression or inflammation. Outside the central nervous system, they are generally asymptomatic and, when calcified, present only as an incidental radiological finding. In the brain and spinal cord, however, cysticerci can be associated with mass effects (for example, sensorimotor or cognitive deficits), seizures, hydrocephalus, chronic meningitis and spinal cord compression. Cysticercosis can cause serious disability but has a low case-fatality rate. The clinical diagnosis of neurocysticercosis can be made by computed tomography (CT) or magnetic resonance imaging (MRI) of the brain or spinal cord.

Laboratory definitive evidence for a confirmed case requires:

• microscopic or histological identification of cysticerci in tissue
• reactive serology on serum or CSF in the context of suggestive radiological features on CT/MRI.

Serological testing can be performed on serum and cerebrospinal fluid. Modern serological assays are highly sensitive and specific for diagnosis of infection in patients with more than one viable cyst. Assay sensitivity is lower in the context of a single or calcified (dead) cyst and slightly lower in CSF compared to serum. Therefore, a negative serological test does not necessarily exclude cysticercosis.

Note: Microscopic identification of proglottids or eggs in the faeces or in the perianal region is also used in the diagnosis of taeniasis, but is not diagnostic of cysticercosis.

• Under investigation: A case that has been notified, but information is not yet available to classify it as probable or confirmed.
• Probable: A clinically compatible illness not accompanied by laboratory definitive evidence but with characteristic radiological features and occurs in a person who has lived in an endemic area.
• Confirmed: A clinically compatible illness accompanied by laboratory definitive evidence.
• Not a case: A case that has been investigated and subsequently found not to meet the case definition.

Humans are the definitive source; pigs the intermediate host.

The time between infection and onset of symptoms can vary from weeks to 10 years or more after infection.

Cysticercosis is acquired either by ingestion of T. solium eggs shed in the faeces of another case (including indirectly via food contamination) or by ingestion of T. solium eggs shed in a case’s own faeces (auto-inoculation).

Larvae remain viable in animal tissues for years. Adult tapeworms may live in the human intestine and shed eggs for up to 25 years, growing up to 8 metres in length. T. solium eggs are infectious both to humans and to pigs. Eggs may remain viable in the environment for months.

Attending medical practitioners or laboratories must immediately notify the local medical officer of health of suspected cases. Notification should not await confirmation.

See Appendix 5: Escalation pathways for more information

Investigate for the presence of T. solium taeniasis in case and among case contacts. Obtain a history of travel, especially to developing countries, and consumption of food prepared by someone who has lived in or travelled to high risk areas.

Ensure laboratory confirmation has been attempted.

Nil. However, in case of taeniasis due to T. solium cross-infection could occur via the faecal-oral route.

Advise the case and their caregivers of the nature of the disease and its mode of transmission. Educate about hygiene, especially hand cleaning.

A person from the same household(s) as the case.

A person who has travelled in developing countries together with the case.

People exposed to the same source of T. solium eggs via faecal-oral contamination if the source has been identified.

Advise contacts to visit their general practitioner to arrange laboratory testing, especially testing for the adult worm (for example, stool testing for eggs and parasites) as taeniasis is the infectious manifestation of the parasite cycle. The laboratory needs to be informed of the contact risk and history. For faecal testing, normally three samples are required.

Nil.

Nil.

Nil.

If the case contracted cysticercosis in New Zealand, liaise with the Ministry for Primary Industries to investigate potential animal sources of infection.

Nil.

Advise on hygienic food handling and on the danger of food contaminated by human faeces.

Public education may be indicated to prevent faecal contamination of soil, water and food for humans and animals. Avoid the use of sewage effluents for pasture irrigation.

Advise about the health dangers of consuming raw or undercooked meat.

Freezing pork or beef below –5ºC for more than 4 days effectively kills cysticerci, as does appropriate irradiation.

Ensure that complete case information is entered into EpiSurv.

On receiving a notification of a case who may have acquired the infection in New Zealand, medical officers of health should contact 0800GETMOH - CD option.

• Heymann DL (ed). 2015. Control of Communicable Diseases Manual (20th edition). Washington: American Public Health Association.
• Garcia HH, Nash TE, Del Brutto OH. Clinical symptoms, diagnosis and treatment of neurocysticercosis. Lancet Neurol 2014;13:1202-15.