Performance assessment of a new indirect rapid diagnostic test for plague detection in humans and other mammalian hosts

Plague is a flea-borne zoonosis that affects a wide range of mammals and still causes outbreaks in human populations yearly across several countries. While crucial for proper treatment, early diagnosis is still a major challenge in low- and middle-income countries due to poor access to laboratory infrastructure in rural areas. To tackle this issue, we developed and evaluated a new F1-based rapid diagnostic test (RDT) as an alternative method for plague diagnosis in humans and other mammals in the field. In this study, 187 serum samples from humans, dogs, rodents and rabbits were retrospectively assessed using the Plague RDT method. To calculate its performance rates, results were confronted to those obtained by hemagglutination (HA) and ELISA, considered as the reference standards. Remarkably, the results from RDT were in full agreement with those from the ELISA and HA assays, resulting in 100% (CI 95% = 95.5-100%) of sensitivity and 100% (CI 95% = 96.6-100%) of specificity. Accordingly, the Cohens Kappa test coefficient was 1.00 (almost perfect agreement). Moreover, the RDT showed no cross-reaction when tested with sera from individuals positive to other pathogens, such as Yersinia pseudotuberculosis, Yersinia enterocolitica, Anaplasma platys, Erliquia canis and Leishmania infantum. Although preliminary, this study brings consistent proof-of-concept results with high performance rates of the Plague RDT when compared to other methods well-established in the plague routine serodiagnosis. Although further human and animal population-based studies will be necessary to validate these findings, the data presented here show that the Plague RDT is highly sensitive and specific, polyvalent to several mammal species and simple to use in field surveillance or point-of-care situations with instant results.