[Alveolar echinococcosis: from an incurable rural disease to a controlled urban infection]. / Echinococcose alvéolaire : d'une maladie rurale incurable à une infection urbaine sous contrôle ?

Human alveolar echinococcosis is a parasitic zoonosis with intermediate (rodents and small lagomorphs) and final (carnivores) hosts. The latter can transmit the parasite to humans, by their feces, which are contaminated by the oncospheres of Echinococcus multilocularis, the larvae of which develop in the liver like a slow cancer. Political, socioeconomic, and ecological factors can affect the intermediate and final hosts and thus influence the long-term emergence and stability of endemic areas. The past 20 years have been marked by: Epidemiologic changes: discovery of an endemic area in China, the largest in the world; extension of the European endemic range to the east and north; extension of the French endemic range to the west and south; and the settlement of contaminated foxes in urban centers, which will modify the populations at risk over time. Progress in diagnosis: initial use of liver ultrasound to screen for asymptomatic disease; value of magnetic resonance imaging to confirm diagnosis and assess extension of disease before beginning treatment; mastery of immunological and genetic diagnosis; and the introduction of positron emission tomography combined with computed tomography to assess the functional activity of the lesions and monitor treatment. Consensus has defined the main directions of a multidisciplinary treatment approach: radical liver resection when possible; avoidance of palliative surgical procedures; use of interventional radiology or endoscopy to treat biliary and vascular complications, whenever possible; consideration of liver transplantation only when all other treatment possibilities have been exhausted; and treatment of all patients, without exception, by albendazole for at least two years after radical surgery and long term (at least several years) in other cases. In France, survival and quality of life have improved very substantially, due to earlier diagnosis, clinical classification of cases, and rigorous follow-up as part of the FrancEchino network. Better understanding of the immunological and immunogenetic mechanisms that underlie the course of disease may open up the possibility of immunomodulation that could replace or round out the current treatments. These are far from satisfactory, in view of the constraints of prolonged, most often life-long treatment by benzimidazoles and their side effects.

[Parasite-host relationships and treatment]. / Le parasite et ses relations avec ses hôtes.

Alveolar echinococcosis (AE) is a parasitic disease caused by intrahepatic growth of the larval stage of the cestode Echinococcus multilocularis. The main definitive host in Europe is the fox. The adult worms live in the fox intestine and their oncospheres are disseminated by faeces. Wolves, dogs and cats may also serve as definitive hosts. Small rodents--especially voles in Europe and small lagomorphs in Asia--are the natural intermediate hosts. The tumour-like larva is composed of multiple vesicles which produce protoscoleces, the fertile stage of the E. multilocularis metacestode. Carnivores are infected by preying on infected rodents. Like rodents, humans are intermediate hosts and are infected either by eating uncooked vegetables and berries contaminated by faeces of infected carnivores, or by touching such animals. Humans are naturally resistant to metacestode development. Genetic characteristics are involved in susceptibility/resistance to E. multilocularis metacestodes. In humans and other intermediate animal hosts, immune suppression enhances parasite growth, which is normally controlled by cytotoxic mechanisms and delayed-type hypersensitivity. Tolerance of E. multilocularis is due in part to parasite characteristics (especially carbohydrate antigens of the laminated layer) and in part to the "anti-inflammatory/tolerogenic" cytokines IL-10 and TGF-beta. Treatment with interferon-a restores a cytokine balance favorable to the host and might be a new therapeutic option for AE patients. Vaccination is a scientifically sound but economically and politically Utopian means of preventing the disease. Prevention thus relies on simple lifestyle measures: cooking potentially contaminated food, regular treatment of domestic animals with praziquantel, and precautions when touching potentially infected definitive hosts (foxes and dogs).

Community surveys and risk factor analysis of human alveolar and cystic echinococcosis in Ningxia Hui Autonomous Region, China.

OBJECTIVE: To determine the true community prevalence of human cystic (CE) and alveolar (AE) echinococcosis (hydatid disease) in a highly endemic region in Ningxia Hui, China, by detecting asymptomatic cases. METHODS: Using hospital records and "AE-risk" landscape patterns we selected study communities predicted to be at risk of human echinococcosis in Guyuan, Longde and Xiji counties. We conducted community surveys of 4773 individuals from 26 villages in 2002 and 2003 using questionnaire analysis, ultrasound examination and serology. FINDINGS: Ultrasound and serology showed a range of prevalences for AE (0-8.1%; mean 2%) and CE (0-7.4%; mean 1.6%), with the highest prevalence in Xiji (2% for CE, 2.5% for AE). There were significant differences in the prevalence of CE, AE and total echinococcosis between the three counties and villages (with multiple degrees of freedom). While hospital records showed 96% of echinococcosis cases attributable to CE, our survey showed a higher prevalence of human AE (56%) compared to CE (44%). Questionnaire analysis revealed that key risk factors for infection were age and dog ownership for both CE and AE, and Hui ethnicity and being female for AE. Drinking well-water decreased the risk for both AE and CE. CONCLUSION: Echinococcosis continues to be a severe public health problem in this part of China because of unhygienic practices/habits and poor knowledge among the communities regarding this disease.

Unique family clustering of human echinococcosis cases in a chinese community.

We have identified a significant focus and unusual clustering of human cases of cystic echinococcosis (CE) and alveolar echinococcosis (AE) in the village of Nanwan, Xiji County, Ningxia Hui Autonomous Region, in one of the most highly endemic areas for both diseases in China. The village, a Chinese Hui Islamic community, is composed of 167 members of four extended families. A total of 28 people died (12 of echinococcosis) since the village was first settled in the 1950s. Despite similar life patterns, the number of AE and CE cases occurring in each family was different. Overall, the prevalences of AE and CE were 9% (20 cases) and 5.9% (13 cases), with a combined prevalence of 14.9%. In contrast to CE, a comparison of the prevalence of AE indicated significant differences between the four family clusters. Although suggestive that host genotype might play a role in susceptibility to AE, this hypothesis requires further investigation.

Imaging aspects and non-surgical interventional treatment in human alveolar echinococcosis.

Alveolar echinococcosis (AE) of the liver caused by the metacestode of the fox tapeworm Echinococcus multilocularis is characterized by a multivesicular structure surrounded by an extensive fibro-inflammatory host reaction. The lesions behave like a slow-growing liver cancer, without sharp limits between the parasitic tissue and the liver parenchyma. Invasion of biliary and vascular walls is another hallmark of this severe disease. Moreover, the poor vascularization of the parasitic mass often leads to necrosis in the central part of the lesion. This explains why liver abscess due to superimposed bacterial infection of the necrotic area may occur in this disease. Currently, a range of imaging techniques can be used at the different stages of management of AE. For diagnosis, ultrasonography remains the first line examination. For a more accurate disease evaluation, aiming to guide the surgical strategy, computerized tomography, Magnetic Resonance (MR) imaging, including cholangio-MR imaging are of importance, providing useful complementary information. More recently, Positive-Emission Tomography using [18F] fluoro-deoxyglucose has been developed for the follow-up of inoperable AE patients under long-term benzimidazoles therapy. This approach seems very promising to assess inflammatory activity and thereby to indirectly depict parasitic activity. Non-surgical interventional procedures, mainly percutaneous biliary and/or centro-parasitic abscesses drainages, are currently a major aspect in the care of incurable AE patients and have largely contributed to the improvement of survival in this situation during the past 20 years. They may also be used as a bridge before a curative surgical procedure in symptomatic patients presenting a life-threatening bacterial and/or fungal infection. It is also very useful in inoperable patients to overcome similar infectious episodes.

Simultaneous alveolar and cystic echinococcosis of the liver.

Alveolar echinococcosis (AE) and cystic echinococcosis (CE), caused by infection with the larval stages of Echinococcus multilocularis and E. granulosus, respectively, are of major clinical importance. Reports of infection with AE or CE are very common, but instances of simultaneous or dual infection are rare. We report on four cases with mixed AE/CE infections in the liver, diagnosed using retrospective surgical records and active community surveys in southern Ningxia Hui Autonomous Region (NHAR), PR China, a recognized hyperendemic area for echinococcosis.