Leptospirosis coexistent with dengue Fever: a diagnostic dilemma.

Sir,

Leptospirosis, a zoonosis and dengue, a mosquito-borne arboviral infection are two of the most common acute febrile illnesses in the tropics. In recent years, with increasing awareness and improvement in diagnostic facilities there has been a rise of leptospirosis cases in and around Chandigarh, with most cases presenting during monsoon and post- monsoon periods (July to November).[1] During the same months, the peak incidence of dengue has been documented in this part of the country.[2] Leptospirosis may present as self-limited febrile illness to severe form (Weil's syndrome) presenting with jaundice and multiple organ dysfunction syndrome (MODS) with high mortality (5−15%).[1] Clinical manifestations of dengue fever (DF) range from a mild febrile illness to severe illness as dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS) leading finally to MODS. Fever in both may be biphasic and may recur after a remission of about 4 days. Headache, retro-orbital pain, photophobia, and thrombocytopenia are also common manifestations. Though rash is more common with dengue viral infection, and jaundice is predominant with leptospira; however, these features are not specific and can also occur in both.[123] Thus, both the diseases have similar clinical manifestation during the initial phase and in severe form posing difficulties in clinical diagnosis. Due to simultaneous transmission during rainy season, it is expected that acute dual infections may occur. However, such co-infections have been reported rarely as an uncommon occurrence.[345] Between July and November 2010, 900 serum samples were received for leptospira serology from suspected cases and these were also tested prospectively for anti-dengue IgM. Specific IgM antibody were detected by anti-leptospiral IgM MAC ELISA (Panbio diagnostics, Brisbane, Australia) and anti-dengue IgM MAC ELISA (NIV, Pune, India) with a sensitivity and specificity of more than 90 and 98%, respectively.

Of these, eight cases (0.9%) were found to be positive for both dengue and leptospiral IgM antibodies. Fever, headache, and myalgia were the most common symptoms among all these eight cases along with thrombocytopenia (<100 000/mm3) and bleeding manifestations in the form of bleeding gums and hematemesis. Jaundice was present in majority of cases (6/8; 75%) whereas hepatomegaly was detected in four (50%) cases.

Our results show that co-infections are not uncommon in Chandigarh and suburbs. As outbreak of dengue is common and for longer periods as compared to leptospirosis, the diagnosis of later is often overshadowed. A reverse scenario may occur during a confirmed leptospirosis outbreak. Dual infection may possibly change the clinical spectrum to a more fulminant one, presenting a diagnostic dilemma. Since the management of DF and leptospirosis are different, failure to recognize them can lead to various complications and higher mortality. Clinicians should be alerted to the potential for a dual infection when facing a patient with protean clinical manifestations. Since jaundice is relatively uncommon in cases of dengue, patients with jaundice and a dengue-like illness should be considered for early evaluation for both dengue and leptospirosis. Laboratory investigations remain mandatory for confirmation.