Comparative performance of lateral flow immunochromatography, iELISA and Rose Bengal tests for the diagnosis of cattle, sheep, goat and swine brucellosis.

Background Brucellosis is a world-wide extended zoonosis that causes a grave problem in developing economies. Animal vaccination and diagnosis are essential to control brucellosis, and the need for accurate but also simple and low-cost tests that can be implemented in low-infrastructure laboratories has been emphasized. Methodology We evaluated bovine, sheep, goat and swine lateral flow immunochromatography assay kits (LFA), the Rose Bengal test (RBT) and a well-validated protein G indirect ELISA (iELISA) using sera of Brucella culture-positive and unvaccinated brucellosis free livestock. Sera from cattle vaccinated with S19 and RB51 brucellosis vaccines were also tested. Finally, we compared RBT and LFA using sera of white Fulani cattle of unknown bacteriological status from a brucellosis endemic area of Nigeria. Results and conclusions Although differences were not statistically significant, RBT showed the highest values for diagnostic sensitivity/specificity in cattle (LFA, 96.6/98.8; RBT, 98.9/100; and iELISA, 96.6/100) and the iELISA yielded highest values in sheep (LFA, 94.0/100; RBT, 92.0/100; iELISA, 100/100), goats (LFA, 95.7/96.2; RBT, 97.8/100; iELISA, 100/100) and pigs (LFA, 92.3/100; RBT, 92.3/100; iELISA, 100/100). Vaccine S19 administered subcutaneously interfered in all tests but conjunctival application minimized the problem. Although designed not to interfere in serodiagnosis, vaccine RB51 interfered in LFA and iELISA but not in the RBT. We found closely similar apparent prevalence results when testing the Nigerian Fulani cattle by RBT and LFA. Although both RBT and LFA (showing similar diagnostic performance) are suitable for small laboratories in resource-limited areas, RBT has the advantage that a single reagent is useful in all animal species. Considering these advantages, its low cost and that it is also useful for human brucellosis diagnosis, RBT might be a good choice for resource-limited laboratories. Author summary Brucellosis is an important zoonosis of worldwide distribution with a heavy impact wherever domestic livestock are bred, including extensive areas of developing economies. The diagnosis of brucellosis is hampered by the absence of pathognomonic symptoms, and thus accurate laboratory tests are essential. Many serological tests have been proposed but most of them are technically sophisticated and expensive and, therefore, unsuitable for laboratories in resource-limited areas. The need for simple and inexpensive tests has been expressed continuously in works dealing with brucellosis in Africa. We present an evaluation of two simple tests, the lateral flow immunochromatography assay (LFA) and the Rose Bengal test (RBT), carried out with gold standard sera (i.e, sera from Brucella culture-positive and brucellosis-free unvaccinated animals) from cattle, sheep, goats and swine, in comparison with an indirect ELISA (iELISA). We also performed an evaluation in cattle vaccinated with S19 and RB51 brucellosis vaccines. Moreover, we compared RBT and LFA for assessing the apparent prevalence of brucellosis in cattle in an endemic area of Nigeria. Our results showed similar diagnostic sensitivity and specificity for the three tests and disproved the extended misconception that rough brucellosis vaccines do not to interfere in serodiagnosis and that, therefore, are optimal tools for controlling the disease in resource-limited areas. Considering their diagnostic performance and simplicity, we conclude that both RBT and LFA are suitable for laboratories in resource-limited areas. RBT has the additional advantage of its low cost and usefulness for the diagnosis of human brucellosis.