An epidemiological and ecological study of human alveolar echinococcosis transmission in south Gansu, China.
Human alveolar echinococcosis (AE) is usually a rare, highly pathogenic zoonotic disease, transmitted across the northern hemisphere between fox and rodent hosts. In China the first cases were described in 1965; however very few epidemiological studies have been undertaken since. Following identification in 1991 of a serious focus of human AE in south Gansu province, detailed village-based community and ecological studies were carried out between 1994 and 1997. Hepatic ultrasound mass screening with serological testing (five tests) identified 84/2482 new AE cases (3%). An overall prevalence of 4.1% (135/3331) was recorded for the area when previous cases were also included. Based on a seropositive result only, without an ultrasound scan indication, no additional AE cases were identified. Of the evolutive AE cases, 96% were seropositive in at least one test, while up 15-20% of individuals who exhibited hepatic calcified lesions and 12-15% exhibiting hepatic nodular lesions were seropositive for specific Em2 or Em18 antibodies. Village (n=31) human AE prevalence rates varied from 0 to 15.8%. Questionnaire analysis indicated that total number of dogs owned over a period was a risk factor (P<0.006), but not a history of red fox hunting (P>0.6). Rodent ecology studies revealed an association between density indices of voles (Microtus limnophilus) and village AE prevalence rates, on the one hand, and village landscape characterised by a ratio of scrub/grassland to total area above 50% (P<0.005). Long-term transmission of Echinococcus multilocularis and risk of zoonotic infection of south Gansu farmers may be related ultimately to a process of deforestation driven by agriculture. This in turn probably results in creation of optimal peri-domestic habitats for rodents that serve as intermediate host species (such as M. limnophilus) and subsequent development of a peri-domestic cycle involving dogs.
Craig
P S
PS
Cestode Zoonoses Research Group, Division of Biological Sciences, School of Environment and Life Sciences, University of Salford, The Crescent, M5 4WT, Salford, UK. p.s.craig@salford.ac.uk
Giraudoux
P
P
Shi
D
D
Bartholomot
B
B
Barnish
G
G
Delattre
P
P
Quere
J P
JP
Harraga
S
S
Bao
G
G
Wang
Y
Y
Lu
F
F
Ito
A
A
Vuitton
D A
DA
D000328:Adult; D000818:Animals; D000909:Antibodies, Helminth / Q000032:analysis; D002681:China / Q000453:epidemiology; D004283:Dog Diseases / Q000469:parasitology / Q000635:transmission; D004285:Dogs; D004444:Echinococcosis, Hepatic / Q000453:epidemiology / Q000635:transmission* / Q000662:veterinary*; D004446:Echinococcus / Q000276:immunology / Q000472:pathogenicity; D004463:Ecology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005589:Foxes / Q000469:parasitology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009784:Occupational Diseases / Q000453:epidemiology / Q000469:parasitology; D012307:Risk Factors; D012377:Rodentia / Q000469:parasitology; D012698:Serologic Tests; D011795:Surveys and Questionnaires
D000909:Antibodies, Helminth