Seropositivity for dengue and Leptospira IgM among patients with acute febrile illness: an indicator of co-infection?

Introduction Presentation of febrile illness with nonspecific features, overlapping manifestations of dengue and leptospirosis, limited laboratory diagnostic tests, make the clinical diagnosis of pyrexia a challenge. The present study aimed to determine the prevalence of Leptospira and dengue IgM co-infection among acute febrile illness patients. Methods This is a retrospective hospital-based study which included patient data collected from June 2016 to May 2017. Inpatients' samples (n=2139) were tested for dengue and/or Leptospira IgM at the Microbiology Laboratory. Data like duration of fever, platelet count, hemoglobin, white blood cell count, erythrocyte sedimentation rate, results of liver and renal function tests, mode of treatment, were collected from medical records of laboratory-confirmed co-infection cases. Results Among 1612 serum samples tested for dengue IgM by ELISA, 382 (23.7%) were positive, 17 equivocal and 1213 were negative. Of the 811 Leptospira IgM ELISA done, 119 (14.7%) were positive, 17 equivocal and 675 negative. Two hundred eighty-four samples were tested for both infections and nine (3.2%) were positive for both and 275 were negative. These nine patients positive for dual infections showed elevated transaminases, alkaline phosphatase, serum bilirubin, creatinine, and blood urea, thrombocytopenia and leukocytosis. They received effective antibiotics along with supportive treatment and were cured of the infection. Conclusions The study emphasizes the possibility of leptospirosis and dengue co-infection (3.2%) and need for confirmation by a highly specific test like PCR. If co-infection is suspected, treatment with specific antibiotics for leptospirosis and supportive treatment for dengue is mandatory, with due attention to complexity of organ involvement.