Comparison of Competitive ELISA, PCR and Loop Mediated Isothermal Amplification of Mycoplasmal DNA in Confirmatory Diagnosis of an Outbreak of Contagious Bovine Pleuropneumonia in Eastern Rwanda

An outbreak of a respiratory disease in cattle was reported in February 2010 at the Rwanda Agriculture Board research station at Nyagatare in Eastern Rwanda. The tentative diagnosis based on clinical and postmortem signs suggested infection with Contagious Bovine Pleuropneumonia (CBPP). This paper presents a comparison of diagnostic techniques and their suitability in detecting early and asymptomatic carriers of CBPP. Serum was prepared from jugular vein blood and used to identify CBPP-infected animals using competitive ELISA (c-ELISA) assay and this was later confirmed with Loop-Mediated Isothermal Amplification (LAMP) of mycoplasmal DNA and Polymerase Chain Reaction (PCR). In order to confirm PCR positivity and enhance sensitivity, nested PCR was performed. In this study, 81 animals were examined by c- ELISA of which 52 were positive, 18 negative and 11 doubtful. Nasal swabs taken from the same 81 animals were examined by both PCR and LAMP for CBPP infections and 17 (20.9%) were found positive by all the three diagnostic techniques. c-ELISA positive and PCR-negative were 35 (43.2%) while c-ELISA- negative and PCR-positive was zero. Two samples were c-ELISA negative and LAMP positive while 35 samples were c-ELISA positive and LAMP negative. Of the 11 doubtful results by c-ELISA, LAMP technique confirmed positivity of 4 samples while PCR confirmed 2. These findings show that more false positive results were obtained with c-ELISA while LAMP indicated more sensitivity than both PCR and c-ELISA suggesting that LAMP, when used with clinical and post-mortem signs, is a suitable test for monitoring and surveillance programmes of CBPP in cattle.