Development and Validation of a Mucosal Antibody (IgA) Test to Identify Persistent Infection with Foot-and-Mouth Disease Virus.

Jitendra K Biswal,Antonello Di Nardo,Geraldine Taylor,Satya Parida,David J Paton

doi:10.3390/v13050814

Abstract

It is well known that approximately 50% of cattle infected with foot-and-mouth disease (FMD) virus (FMDV) may become asymptomatic carrier (persistently infected) animals. Although transmission of FMDV from carrier cattle to naïve cattle has not been demonstrated experimentally, circumstantial evidence from field studies has linked FMDV-carrier cattle to cause subsequent outbreaks. Therefore, the asymptomatic carrier state complicates the control and eradication of FMD. Current serological diagnosis using tests for antibodies to the viral non-structural proteins (NSP-ELISA) are not sensitive enough to detect all carrier animals, if persistently infected after vaccination and do not distinguish between carriers and non-carriers. The specificity of the NSP ELISA may also be reduced after vaccination, in particular after multiple vaccination. FMDV-specific mucosal antibodies (IgA) are not produced in vaccinated cattle but are elevated transiently during the acute phase of infection and can be detected at a high level in cattle persistently infected with FMDV, irrespective of their vaccination status. Therefore, detection of IgA by ELISA may be considered a diagnostic alternative to RT-PCR for assessing FMDV persistent infection in ruminants in both vaccinated and unvaccinated infected populations. This study reports on the development and validation of a new mucosal IgA ELISA for the detection of carrier animals using nasal, saliva, and oro-pharyngeal fluid (OPF) samples. The diagnostic performance of the IgA ELISA using nasal samples from experimentally vaccinated and infected cattle demonstrated a high level of specificity (99%) and an improved level of sensitivity (76.5%). Furthermore, the detection of carrier animals reached 96.9% when parallel testing of samples was carried out using both the IgA-ELISA and NSP-ELISA.

Highlights

Foot-and-mouth disease (FMD) is a highly contagious vesicular disease caused by FMD virus (FMDV), an aphthovirus within the family picornaviridae that infects both domesticated and wild cloven-hoofed animals [1]
Nasal and oro-pharyngeal fluid (OPF) samples were collected from four vaccine challenge experiments, each consisting of 25 Holstein-Friesian cattle, aged 4–8 months, carried out in biosecurity containment at the Pirbright Institute, Pirbright, U.K
Out of 80 vaccinated and 20 unvaccinated control cattle from four vaccine-challenge experiments involving a single dose of vaccine, 32 and 5 cattle were detected as FMDV

Summary

Introduction

Foot-and-mouth disease (FMD) is a highly contagious vesicular disease caused by FMD virus (FMDV), an aphthovirus within the family picornaviridae that infects both domesticated and wild cloven-hoofed animals [1]. The classical FMD symptoms in ruminants are characterised by fever, inappetence, lameness, excess salivation and vesicles in and around the mouth, teats and feet Up to 50% of FMD-recovered cattle may harbour virus in their oro-pharyngeal and naso-pharyngeal cavity at 28 or more days post-infection and are known as FMDV-carriers or persistently infected animals [3,4]. This asymptomatic carrier state of FMD complicates the control and eradication of the disease. A recent experimental study has demonstrated clinical infection in naïve cattle when inoculated with oro-pharyngeal fluids (OPF)

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Conclusion