Detection ofEchinococcus granulosus and Echinococcus equinus in Dogs and Epidemiology of Canine Echinococcosis in the UK

Echinococcus granulosus is a canid cestode species that causes hydatid disease or cystic echinococcosis (CE) in domestic animals or humans. Echinococcus equinus formerly recognised as the ‘horse strain’ (E.granulosus genotype G4) is not known to be zoonotic and predominantly involves equines as its intermediate host. The domestic dog is the main definitive host for both species, which are also both endemic in the UK but data is lacking especially for E.equinus. An E.equinus-specific PCR assay was designed to amplify a 299bp product within the ND2 gene and expressed 100% specificity against a panel of 14 other cestode species and showed detection sensitivity up to 48.8pg (approx. 6 eggs). Horse hydatid cyst isolates (n = 54) were obtained from 14 infected horse livers collected from an abattoir in Nantwich, Cheshire and hydatid cyst tissue was amplified using the ND2 PCR primers to confirm the presence of E.equinus and used to experimentally infect dogs in Tunisia from which serial post-infection faecal samples were collected for coproanalysis, and indicated Echinococcus coproantigen and E.equinus DNA was present in faeces by 7 and 10 days post infection, respectively. Canine echinococcosis due to E.granulosus appears to have re-emerged in South Powys (Wales) and in order to determine the prevalence of canine echinococcosis a coproantigen survey was undertaken. The Welsh Assembly Government also funded a 2 year hydatid disease eradication campaign (2008-10) as a preventative public health measure and faecal samples were tested from farm dogs in the control area. In addition 8 foxhound packs (5 from Wales and 3 from England) were sampled and screened for echinococcosis infection using an Echinococcus genus-specific coproantigen ELISA that was optimised against a panel of known Echinococcus and control faecal samples. Farm dogs and foxhounds were also screened using two coproPCR assays (predominantly E.granulosus G1 or E.equinus G4 specific). In the Welsh farm dog study, 609 dog faecal samples were collected at baseline (pre-treatment) of which 10.8% (66/609) were found to be coproantigen positive, 5.1% (31/609) were G1 E.granulosus coproPCR positive, and 1.8% (12/609) were E.equinus ND2 coproPCR positive. A total of 742 farm dog samples were tested after 3 quarterly deworming treatments and showed a coproantigen decrease to 0.7% (5/742). One year after the last dosing round 4.2% (45/1076) of farm dogs were found to be coproantigen positive; of these only 123 were tested with the G1 primers of which 15.4% (19/123) were positive for E.granulosus DNA. Of 8 foxhound packs screened by the Echinococcus genus specific coproantigen ELISA and by the two coproPCR tests (E.granulosus, E.equinus) 3 of the 4 Welsh hunts had copropositive dogs (hunt prevalence 30.9%, 9.7%, 61.2%) and 2 of the 3 English hunts (hunt prevalence 17.5%, 44.5%). Hounds in 6 of the 8 hunts were coproPCR positive for E.granulosus DNA and 2 of the 8 hunts were positive for E.equinus coproDNA. Additional foxhound data was collected in the form of a survey questionnaire to hunt staff which suggested that there may be a link between increased Echinococcus coproantigen prevalence and inadequate worming protocols and unsafe feeding practices. The study showed that canine echinococcosis due to E.granulosus and E.equinus occurred in farm dogs and foxhounds in Wales and England and that an intervention programme in mid-Wales reduced canine echinococcosis in farm dogs after four dosing rounds, but coproprevalence increased by 12 months after cessation of dosing. The data are discussed with reference to potential human infection, risk factors and optimal intervention approaches. The study showed that the distribution of canine echinococcosis in farm dogs and foxhounds was not homogenous and also confirms the continued presence of both E.granulosus and E.equinus in foxhounds in England and Wales.