Thus, in developing countries such as Peru, where access to reference serodiagnostic assays like MAT may be difficult in many regions and limited resources could preclude the purchase of commercial ELISA assays, this in-house ELISA IgM assay may be useful to ‘rule-out’ a diagnosis of leptospirosis in the early stages of febrile illness where timely initiation of anti-leptospiral antibiotics may be critical [13]. This evidence concerns the gene CD40LG and leptospirosis.