Echinococcus multilocularis
From IDWiki
Background
Microbiology
- Cestode in the Echinococcus family
- Disease is caused by the larval form
Life Cycle
- Definitive hosts are canid carnivorous animals, including urban coyotes
- Eggs contaminate the environment, including produce
- They are infective after a few days, and are viable for up to 16 months at 4ºC
- Intermediate hosts (metacestode) are rodents, possibly pigs, and and incidentally humans
- Intermediate host is eaten by the definitive host, completing the life cycle
Epidemiology
- Estimated 18,000 cases annually
- Worldwide in the northern hemisphere
- Most cases in China (90%), followed by Japan and Russia
- Rare in North America
- Within Canada:
- Associated with arctic foxes and wolves
- Alberta has highest number of cases, with 19 cases from 2013 to 2021
- 0 to 3 case reports in other provinces
Clinical Manifestations
- Causes alveolar echinococcosis
- Incubation period 5 to 15 years
- Vague abdominal pain may precede diagnosis by years
- Presents as a metastatic malignancy of unknown primary, mot commonly with malaise, weight loss, and right upper quadrant discomfort
- May also mimic hepatocellular carcinoma, cirrhosis, and tuberculosis
- Causes continuously-growing tumour-like polycystic mass, made up of multiple vesicles that are lined by laminated germinal layer
- Can cause cholestatic jaundice, cholangitis, portal hypertension, and Budd-Chiari syndrome
Diagnosis
- Combination of radiologic and serologic investigations
- A single negative serologic test does not rule out infection
- May be confirmed by biopsy
Case Definition (Alberta)
- Typical organ lesion detected by imaging with US or CT
- AND histopathology compatible with alveolar echinococcosis
- AND
- Detection of E. multilocularis by serology
- OR detection of E. multilocularis by molecular diagnostic methods
Imaging
- Ultrasound or CT demonstrates lesions which typically have an irregular contour, no well-defined wall, central necrosis, and irregular intralesional and wall calcifications
PNM Classification
- P=parasitic mass in the liver, N=neighbouring organ involvement; M=metastases
| P | N | M | |
|---|---|---|---|
| X | Primary tumour cannot be assess | Not evaluable | Not evaluable |
| 0 | No detectable tumour in liver | No regional involvement | No metastasis |
| 1 | Peripheral lesions without proximal vascular and/or biliary involvement | Regional involvement of contiguous organs or tissues | Metastasis |
| 2 | Central lesions with proximal vascular and/or biliary invovlement of 1 lobe | ||
| 3 | Central lesions with hilar vascular or biliary involvement of both lobes and/or with involvement of 2 hepatic veins | ||
| 4 | Any liver lesion with extension along the vessels and biliary tree |
Management
- Main treatment is surgical resection followed by at least 2 years of antihelminthic therapy (e.g. albendazole)
- Poor prognosis, with 90% 10-year mortality if untreated
