Fortuitous discovery of a microfilaria of the genus Loa loa during a routine blood smear at the Hematology Laboratory of the Mohamed V Military Instruction Hospital in Rabat: a case report

Loiasis is a parasitic infection transmitted by a vector, specifically through the bites of Chrysops genus tabanid flies. It is often associated with marked and persistent eosinophilia in affected individuals. We report the case of a 28-year-old Cameroonian male patient. His medical history includes an episode of malaria treated on an outpatient basis. As part of a diving internship in Morocco, the young serviceman underwent a medical fitness examination at the Medical Expertise Center for Aircrew Personnel of the Mohamed V Military Hospital, which included a biological assessment. This revealed a mildly elevated bilirubin level, lactate dehydrogenase activity at the upper limit of normal and eosinophilia at 1500 µl–1, without anaemia or thrombocytopaenia. A blood smear was prepared and stained with May-Grünwald Giemsa, revealing the presence of several small worms, with an appearance consistent with Loa loa microfilariae. This case of L. loa, identified in the haematology laboratory, is one of the rare diagnoses in Morocco. Therefore, biologists need to remain vigilant and carry out a thorough analysis of the blood count and blood smear.