Short report: Serodiagnosis of plague in humans and rats using a rapid test.

Serodiagnosis of plague is very useful for its retrospective confirmation and for epidemiologic studies in humans and in rodents, since rats constitute the main natural reservoir of Yersinia pestis. We have developed a rapid test for the detection of IgG antibodies to fraction 1 (F1) based on immunochromatography and protein A to detect both human and rat IgG. When tested with reference human sera (35 positive and 37 negative), this assay showed a sensitivity of 94.3% and a specificity of 89.2%. When Rattus rattus and R. norvegicus reference sera (22 positive and 24 negative) were used, the sensitivity was 100% and the specificity was 91.7%. This simple serodiagnostic tool is of great potential value in the surveillance of plague. As far as we know, this test is the first of its kind designed for diagnosis of both humans and animals.