title: The use of a Psoroptes ovis serodiagnostic test for the analysis of a natural outbreak of sheep scab.
abstract: BACKGROUND
  Sheep scab is a highly contagious disease of sheep caused by the ectoparasitic mite Psoroptes ovis. The disease is endemic in the UK and has significant economic impact through its effects on performance and welfare. Diagnosis of sheep scab is achieved through observation of clinical signs e.g. itching, pruritis and wool loss and ultimately through the detection of mites in skin scrapings. Early stages of infestation are often difficult to diagnose and sub-clinical animals can be a major factor in disease spread. The development of a diagnostic assay would enable farmers and veterinarians to detect disease at an early stage, reducing the risk of developing clinical disease and limiting spread.
  
  
  METHODS
  Serum samples were obtained from an outbreak of sheep scab within an experimental flock (n = 480 (3 samples each from 160 sheep)) allowing the assessment, by ELISA of sheep scab specific antibody prior to infestation, mid-outbreak (combined with clinical assessment) and post-treatment.
  
  
  RESULTS
  Analysis of pre-infestation samples demonstrated low levels of potential false positives (3.8%). Of the 27 animals with clinical or behavioural signs of disease 25 tested positive at the mid-outbreak sampling period, however, the remaining 2 sheep tested positive at the subsequent sampling period. Clinical assessment revealed the absence of clinical or behavioural signs of disease in 132 sheep, whilst analysis of mid-outbreak samples showed that 105 of these clinically negative animals were serologically positive, representing potential sub-clinical infestations.
  
  
  CONCLUSIONS
  This study demonstrates that this ELISA test can effectively diagnose sheep scab in a natural outbreak of disease, and more importantly, highlights its ability to detect sub-clinically infested animals. This ELISA, employing a single recombinant antigen, represents a major step forward in the diagnosis of sheep scab and may prove to be critical in any future control program.
authors.affiliation: Moredun Research Institute, Pentlands Science Park, Bush Loan, Edinburgh, Midlothian, EH26 0PZ, Scotland, UK. stewart.burgess@moredun.ac.uk
authors.forename: Stewart T G
authors.initials: ST
authors.lastname: Burgess
authors.forename: Giles
authors.initials: G
authors.lastname: Innocent
authors.forename: Francesca
authors.initials: F
authors.lastname: Nunn
authors.forename: David
authors.initials: D
authors.lastname: Frew
authors.forename: Fiona
authors.initials: F
authors.lastname: Kenyon
authors.forename: Alasdair J
authors.initials: AJ
authors.lastname: Nisbet
authors.forename: John F
authors.initials: JF
authors.lastname: Huntley
mesh_terms: D000818:Animals; D000906:Antibodies / Q000097:blood* / Q000378:metabolism; D000941:Antigens; D004196:Disease Outbreaks / Q000662:veterinary*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000662:veterinary*; D005188:False Negative Reactions; D005189:False Positive Reactions; D005260:Female; D008924:Mite Infestations / Q000175:diagnosis / Q000453:epidemiology / Q000662:veterinary*; D040042:Psoroptidae / Q000276:immunology*; D011994:Recombinant Proteins; D012680:Sensitivity and Specificity; D012698:Serologic Tests; D012756:Sheep; D012757:Sheep Diseases / Q000175:diagnosis* / Q000453:epidemiology / Q000469:parasitology; D013997:Time Factors
chemical_list: D000906:Antibodies; D000941:Antigens; D011994:Recombinant Proteins