Comparison of a Flow Assay for Brucellosis Antibodies with the Reference cELISA Test in West African Bos indicus

Barend M Dec Bronsvoort,Fiona Land,Ian G Handel,Theresia H Abdoel,Bronwyn Koterwas,Henk L Smits,Kenton L Morgan,Vincent N Tanya,James Tucker,Matthew Baylis

doi:10.1371/journal.pone.0005221

Abstract

Brucellosis is considered by the Food and Agricultural Organisation and the World Health Organisation as one of the most widespread zoonoses in the world. It is a major veterinary public health challenge as animals are almost exclusively the source of infection for people. It is often undiagnosed in both human patients and the animal sources and it is widely acknowledged that the epidemiology of brucellosis in humans and animals is poorly understood, particularly in sub-Saharan Africa. It is therefore important to develop better diagnostic tools in order to improve our understanding of the epidemiology and also for use in the field for disease control and eradication. As with any new diagnostic test, it is essential that it is validated in as many populations as possible in order to characterise its performance and improve the interpretation of its results. This paper describes a comparison between a new lateral flow assasy (LFA) for bovine brucellosis and the widely used cELISA in a no gold standard analysis to estimate test performance in this West African cattle population. A Bayesian formulation of the Hui-Walter latent class model incorporated previous studies' data on sensitivity and specificity of the cELISA. The results indicate that the new LFA is very sensitive (∼87%) and highly specific (∼97%). The analysis also suggests that the current cut-off of the cELSIA may not be optimal for this cattle population but alternative cut-offs did not significantly change the estimates of the LFA. This study demonstrates the potential usefulness of this simple to use test in field based surveillance and control which could be easily adopted for use in developing countries with only basic laboratory facilities.

Highlights

Brucellosis is considered by the Food and Agricultural Organisation and the World Health Organisation as one of the most widespread zoonosis in the world
This paper describes a comparison between this new lateral flow assasy (LFA) for bovine brucellosis and the O.I.E. reference competitive ELISA (cELISA) in a no gold standard analysis
The plot suggests that there may be a better %optical density (OD) cut-off of 50% for the cELISA in this African cattle population which we have explored later in the analysis

Summary

Introduction

Brucellosis is considered by the Food and Agricultural Organisation and the World Health Organisation as one of the most widespread zoonosis in the world. Brucellosis in humans (mainly due to Brucella melitensis and B. abortus) produces an acute febrile disease that may progress to a chronic form. Brucellosis in animals is a sub-acute or chronic disease affecting a range of domestic and wildlife species [1]. Mortality rates may be around 5% higher in calves from seropositive cows [2], with high morbidity rates in adults. Brucellosis it is the leading cause of contagious abortion in livestock. The most important species are B. abortus, B melitensis and B. suis causing abortions, premature births and retained placentae in livestock [3]. Animals are almost exclusively the source of infection for people and any attempts at reducing the human disease burden is dependent on identifying the infected animal source

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Conclusion