Development of rapid immunochromatographic strip test for the detection of porcine epidemic diarrhoea virus

Lyoo, Kwang-Soo; Yeom, Minjoo; Kim, Jungho; Kim, Donghyuk; Ha, Gunwoo; Na, Woonsung; Le, Van Phan; Song, Daesub

Since the PEDV emergency in the USA in 2013, PED outbreaks have occurred worldwide. The prototype of PEDV is the CV777 strain, which was identified in 1977 in Belgium. Next, PEDV spread throughout Europe and Asia during the 1980s and 1990s and recently emerged in the USA. Based on extensive phylogenetic analysis using obtained sequences, PEDV strains are classified into two major categories: the classical PEDV strain showing lower pathogenicity and highly virulent PEDV strain that emerged in 2010. However, most studies aimed at developing techniques for diagnosing PEDV infection have attempted to differentiate various diarrhoea-causing antigens rather than differentiating between classical and novel PEDV strains. In the present study, we established an ICA kit that can be universally applied for PEDV infection screening without differentiation. The first advantage of this diagnostic kit is that it can be used for any diarrhoea case in which viral infection is suspected, but for which there is no available information regarding PEDV strain involvement. Second, ICA is useful upon emergence of novel PEDV strains, for which a strain-specific diagnostic method may be ineffective. Thus, another optimised diagnostic method should be considered to differentiate classical and novel PEDV strains if additional detection becomes essential for epidemiological studies or disease control. The detection limit of the ICA kit was10 4.0 TCID 50 / ml, while its sensitivity was less than that of real-time RT-PCR (10 2.0 TCID 50 /ml). It is generally accepted that rapid screening test kits may not be as sensitive as gold standard methods for virus diagnosis such as real-time PCR. However, high relative specificity and sensitivity results for PEDV were observed using field samples. Considering the performance of the ICA kit, we additionally assessed the sensitivity of the test in samples from piglets experimentally infected with PEDV; the results showed 100 per cent agreement with real-time RT-PCR results. These results of the challenge study clearly indicate the value of well-defined serial stool samples from experimentally infected animals, as the results of these samples are not influenced by previous infections with PEDV or other gastroenteric pathogens.