The Sensitivity And Specificity Of Clinical Signs, Post-mortem Findings And Isolation Of Escherichia Coli In Diagnosing Edema Disease Of Swine.

Abstract

Commonly used diagnost ic techniques for edema disease in Kenya were tested for their sensitivity and specificity on 84 pig carcasses submitted to Department of Veterinary Pathology and Microbiology between June 2004 and June 2007. Clinical signs gathered from anamnesis, post - mortem lesions revealed at autopsy and E. coli isolated from intestinal contents and characterized using biochemical tests and polymerase chain reacti on were compared using receiver - operating characteristic analyses. A combination of clinical signs, post - mortem findings and isolation of E. coli carrying F18 and shiga - toxin type II variant genes were used as gold standard test. Forty nine (58.3%) cases w ere diagnosed as edema disease, based on clinical signs and post - mortem findings . Of these, thirty eight (77.6%) had variable amounts of edema in various body si tes and clinically, twenty six (53.1%) had neurological signs, 18 (36.7%) were found dead, 3 ( 6.1%) had swollen eyelids and 2 (4.1%) expressed respiratory distress. Hemolytic E. coli carrying the tested genes were isolated from thirty one (62.2%) of these cases. Presence of edema in various body cavities and observation of defined clinical signs h ad 75.3% and 57.4% sensitivity, respectively. Considered individually, the sensitivity was 64.7% for found dead, 50% for neurological signs and 84.4% for isolating hemolytic E. coli. All had a specificity of 81.3%. The results show that none of the diagnos tic techniques had the expected 100% sensitivity and specificity, but isolation of hemolytic E. coli may be an important screening test for suspected edema disease cases