Persistent dengue NS1 antigen in a patient with visceral leishmaniasis: A diagnostic and therapeutic odyssey

Visceral leishmaniasis (VL) and dengue are both life-threatening vector-borne diseases and are endemic in many low- and middle-income countries (LMICs). Despite being caused by different pathogens and transmitted by distinct vectors, Leishmania parasite-dengue virus (DENV) coinfection can complicate the course of diseases, their diagnoses and their treatments due to their some similar clinical features. This study presents a 23-year-old male patient from the Dang district of Nepal, a migrant worker in Malaysia who experienced a prolonged intermittent fever. The patient’s symptoms, clinical diagnosis and disease management approach across three different countries (Malaysia, India, and Nepal) were recorded. The patient was initially diagnosed positive for dengue in Malaysia during his immigration period as a worker. Due to a persistent fever, he had to return to Nepal. In India, other investigations erroneously suspected hematological malignancy. Finally, after a third febrile episode, VL was correctly diagnosed, but initial treatment with Liposomal Amphotericin B (LAMB) failed, resulting in relapse. During this period, the dengue NS1 antigen remained positive. Despite treatment with six doses of LAMB, the patient showed no adequate response. After negative test results for dengue NS1 antigen, IgM, and IgG antibody, a highly effective rescue intervention of miltefosine led to the resolution of VL. This study underscores the challenges and complexities of diagnosis associated with Leishmania -DENV coinfection. These concomitant infections appear to be the cause of the prolonged persistence of dengue fever, and progression from an asymptomatic Leishmania infection to a symptomatic VL. It also highlights the need for diagnostic tools and effective management strategies to address coinfections.