Diagnosis of foot-and mouth disease by real time reverse transcription polymerase chain reaction under field conditions in Brazil

Tatiane A Paixão,Alcina V Carvalho Neta,Naimes O Paiva,Renato L Santos,Barbara M Martin,René R Silva,Jorge R Reis,Tammy R Beckham,L Garry Adams,Claudia V Serra,Meirivan S Barbosa,Neville P Clarke

doi:10.1186/1746-6148-4-53

Abstract

BackgroundFoot-and-mouth disease (FMD) is an economically important and highly contagious viral disease that affects cloven-hoofed domestic and wild animals. Virus isolation and enzyme-linked immunosorbent assay (ELISA) are the gold standard tests for diagnosis of FMD. As these methods are time consuming, assays based on viral nucleic acid amplification have been developed.ResultsA previously described real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay with high sensitivity and specificity under laboratorial and experimental conditions was used in the current study. To verify the applicability of this assay under field conditions in Brazil, 460 oral swabs from cattle were collected in areas free of FMD (n = 200) and from areas with outbreaks of FMD (n = 260). Three samples from areas with outbreaks of FMD were positive by real-time RT-PCR, and 2 of those samples were positive by virus isolation and ELISA. Four other samples were considered inconclusive by real-time RT-PCR (threshold cycle [Ct] > 40); whereas all 200 samples from an area free of FMD were real-time RT-PCR negative.Conclusionreal-time RT-PCR is a powerful technique for reliable detection of FMDV in a fraction of the time required for virus isolation and ELISA. However, it is noteworthy that lack of infrastructure in certain areas with high risk of FMD may be a limiting factor for using real-time RT-PCR as a routine diagnostic tool.

Highlights

Foot-and-mouth disease (FMD) is an economically important and highly contagious viral disease that affects cloven-hoofed domestic and wild animals
Among the 200 samples from Eldorado and Japorã (State of Mato Grosso do Sul), 3 were positive by real-time reverse transcription polymerase chain reaction (RT-PCR), 2 of which were positive by combined virus isolation/enzymelinked immunosorbent assay (ELISA); whereas 4 samples were considered inconclusive with cycle threshold (Ct) values higher than 40
The real-time RT-PCR method used in the current study has proven to be highly sensitive and specific under laboratory and experimental conditions (Callahan et al 2002), which is supported by our results as all previously characterized field isolates resulted in positive reactions with low Ct values

Summary

Introduction

Foot-and-mouth disease (FMD) is an economically important and highly contagious viral disease that affects cloven-hoofed domestic and wild animals. Virus isolation and enzymelinked immunosorbent assay (ELISA) are the gold standard tests for diagnosis of FMD. As these methods are time consuming, assays based on viral nucleic acid amplification have been developed. Foot-and-mouth disease (FMD) is a highly contagious viral disease that affects cloven-hoofed domestic and wild animals. FMD causes enormous losses to the animal industry due to costs associated with control or eradication measures, including massive vaccination and/or destruction of infected herds, as well as decreases in milk and beef production as a result of clinical disease. Foot-and-mouth disease usually has a high morbidity and low mortality, with mortality occurring mostly in young animals [2]

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