Evaluation of ELISA coupled with Western blot as a surveillance tool for Trichinella infection in wild boar (Sus scrofa).
Trichinella surveillance in wildlife relies on muscle digestion of large samples which are logistically difficult to store and transport in remote and tropical regions as well as labour-intensive to process. Serological methods such as enzyme-linked immunosorbent assays (ELISAs) offer rapid, cost-effective alternatives for surveillance but should be paired with additional tests because of the high false-positive rates encountered in wildlife. We investigated the utility of ELISAs coupled with Western blot (WB) in providing evidence of Trichinella exposure or infection in wild boar. Serum samples were collected from 673 wild boar from a high- and low-risk region for Trichinella introduction within mainland Australia, which is considered Trichinella-free. Sera were examined using both an 'in-house' and a commercially available indirect-ELISA that used excretory-secretory (E/S) antigens. Cut-off values for positive results were determined using sera from the low-risk population. All wild boar from the high-risk region (352) and 139/321 (43.3%) of the wild boar from the low-risk region were tested by artificial digestion. Testing by Western blot using E/S antigens, and a Trichinella-specific real-time PCR was also carried out on all ELISA-positive samples. The two ELISAs correctly classified all positive controls as well as one naturally infected wild boar from Gabba Island in the Torres Strait. In both the high- and low-risk populations, the ELISA results showed substantial agreement (k-value=0.66) that increased to very good (k-value=0.82) when WB-positive only samples were compared. The results of testing sera collected from the Australian mainland showed the Trichinella seroprevalence was 3.5% (95% C.I. 0.0-8.0) and 2.3% (95% C.I. 0.0-5.6) using the in-house and commercial ELISA coupled with WB respectively. These estimates were significantly higher (P<0.05) than the artificial digestion estimate of 0.0% (95% C.I. 0.0-1.1). Real-time PCR testing of muscle from seropositive animals did not detect Trichinella DNA in any mainland animals, but did reveal the presence of a second larvae-positive wild boar on Gabba Island, supporting its utility as an alternative, highly sensitive method in muscle examination. The serology results suggest Australian wildlife may have been exposed to Trichinella parasites. However, because of the possibility of non-specific reactions with other parasitic infections, more work using well-defined cohorts of positive and negative samples is required. Even if the specificity of the ELISAs is proven to be low, their ability to correctly classify the small number of true positive sera in this study indicates utility in screening wild boar populations for reactive sera which can be followed up with additional testing.
School of Veterinary Science, The University of Queensland, Gatton, QLD 4343, Australia. Electronic address: l.cuttell@uq.edu.au.
Leigh
L
Cuttell
European Reference Laboratory for Parasites, Instituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy. Electronic address: mariaangeles.gomezmorales@iss.it.
Maria Angeles
MA
Gómez-Morales
Australian Department of Agriculture, Fisheries and Forestry, DAFF Biosecurity Northern Region, Box 96, Cairns International Airport, Cairns, QLD 4878, Australia. Electronic address: Beth.Cookson@daff.gov.au.
Beth
B
Cookson
School of Veterinary and Life Sciences, Murdoch University, Murdoch, WA 6150, Australia. Electronic address: p.adams@murdoch.edu.au.
Peter J
PJ
Adams
School of Population Health, The University of Queensland, Herston, QLD 4006, Australia. Electronic address: simon.reid@uq.edu.au.
Simon A
SA
Reid
Australian Department of Agriculture, Fisheries & Forestry, PO Box 222, Hamilton Central, QLD 4007, Australia. Electronic address: Paul.Vanderlinde@daff.gov.au.
Paul B
PB
Vanderlinde
Department of Agriculture, Fisheries & Forestry, Biosecurity Sciences Laboratory, Coopers Plains, QLD 4108, Australia. Electronic address: Louise.Jackson@daff.qld.gov.au.
Louise A
LA
Jackson
Peninsula School of Medicine & Dentistry, Plymouth University, Plymouth PL4 8AA, United Kingdom. Electronic address: christian.gray@plymouth.ac.uk.
C
C
Gray
School of Veterinary Science, The University of Queensland, Gatton, QLD 4343, Australia. Electronic address: r.traub@uq.edu.au.
Rebecca J
RJ
Traub
D000818:Animals; D000909:Antibodies, Helminth / Q000097:blood; D001315:Australia / Q000453:epidemiology; D015153:Blotting, Western / Q000662:veterinary*; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary*; D018482:Muscle, Skeletal / Q000469:parasitology; D011159:Population Surveillance / Q000379:methods*; D060888:Real-Time Polymerase Chain Reaction / Q000662:veterinary; D015203:Reproducibility of Results; D016036:Seroepidemiologic Studies; D034421:Sus scrofa / Q000469:parasitology*; D013552:Swine; D013553:Swine Diseases / Q000175:diagnosis* / Q000453:epidemiology; D014234:Trichinella / Q000276:immunology / Q000502:physiology*; D014235:Trichinellosis / Q000175:diagnosis / Q000453:epidemiology / Q000662:veterinary*
D000909:Antibodies, Helminth
ELISA; Real-time PCR; Serosurveillance; Trichinella; Western blot; Wildlife