Taenia (Multiceps) multiceps and Taenia serialis : Coenurosis

Epidemiology and Life Cycle

Fewer than 150 cases of coenurosis in humans have been reported, although potential exposure is common because of the widespread prevalence among dogs and other canids. Most cases of coenurosis occur in Africa, although the disease has also been reported in the UK, France, North America, the Middle East, and India. ^, Most cases from tropical Africa involve subcutaneous sites, whereas reported cases from South Africa and other temperate regions, including the US, have a higher frequency of intracranial localization. In North America, at least six cases of human autochthonous infection have been documented. Three cases involved the central nervous system (CNS), and the others involved intramuscular or subcutaneous localization.

Adult T. multiceps and T. serialis tapeworms can be recovered from the small intestines of definitive canid hosts, including dogs, wolves, foxes, and coyotes. ^, An intermediate host ingests embryonated eggs or gravid proglottids in the environment. Oncospheres hatch within the intermediate host and circulate to the tissues, often the brain or spinal cord. The inner membrane (i.e., bladder) of the resulting cyst is composed of multiple protoscolices with additional small protoscolices or metacestodes contained within. Intermediate hosts for T. multiceps include various herbivores (e.g., sheep, goats, or horses), whereas T. serialis larvae most often are found in rabbits and squirrels. Human infestation is thought to occur by ingestion of food or water that has been contaminated with the feces of an infected animal, usually a dog.

Clinical Manifestations

Human disease frequently involves the CNS, where it causes a cystic lesion and can be confused with neurocysticercosis, echinococcosis, or malignancy. ^{, ,} Intracerebral cysts can cause headaches, personality changes, hemiparesis, cranial nerve palsy, weakness, nuchal rigidity, seizures, weight loss, increased intracranial pressure, or papilledema. ^, Complications of coenurosis include meningitis, arteritis, arachnoiditis, ependymitis, and ocular involvement. Intraparenchymal lesions of the spinal cord have been reported rarely. Subcutaneous and intramuscular cysts are reported most commonly in Africa and involve the intercostal area, axillae, or anterior abdominal wall. ^{, ,} Allergic symptoms, such as recurrent urticaria, fever, and night sweats, also have been reported.

Laboratory Findings and Diagnosis

A presumptive diagnosis of coenurosis most often is based on results of imaging studies, including magnetic resonance imaging, computed tomography, or ultrasound. ^, The pressure of the cerebrospinal fluid (CSF) often is elevated. Analysis of the CSF may show lymphocytic pleocytosis and reduced glucose and elevated protein concentrations.

A definitive diagnosis requires surgical excision and histopathologic identification of the parasite. ^, Fine-needle aspiration of a cyst also may yield a diagnosis. ^, Coenurus larvae are easily distinguished morphologically from cysticerci and hydatid cysts on the basis of the number and characteristics of their protoscolices ( Fig. 282.1 ). Coenurid cysts also lack the acellular, laminated membrane characteristic of echinococcal cysts. Racemose (acephalic) cysticerci often cannot be differentiated from coenuri because the thin cyst membranes are similar.

Polymerase chain reaction–based restriction fragment length polymorphism (PCR-RFLP) has been used experimentally to differentiate various species of taeniid cestodes, including T. multiceps and T. serialis . ^, Successful PCR-amplification of cestode DNA in tissue and CSF has been described. ^, Molecular techniques may prove useful for diagnostic and epidemiologic purposes because there is no reliable serologic test for coenurosis.