Molecular identification of Hypoderma sinense cutaneous myiasis in a child from a cattle-raising pastoral region of China: a case report

Abstract

Abstract Background Zoonotic parasitic infestations may be overlooked when they mimic common pediatric skin infections. Cutaneous myiasis caused by Hypoderma species is mainly associated with livestock, whereas human infestation by Hypoderma sinense ( H. sinense ) is rarely reported. Early lesions may resemble furunculosis, leading to delayed recognition and species-level diagnosis. We report a molecularly confirmed case of H. sinense cutaneous myiasis in a preschool child from a cattle-raising pastoral region of China, highlighting the diagnostic value of ultrasonography, minimally invasive larval extraction and whole-genome shotgun sequencing-based molecular identification. Case presentation A 3-year-2-month-old boy presented with painful subcutaneous nodules on the trunk, posterior neck and right scapular region for more than one month. He lived in Aba Tibetan and Qiang Autonomous Prefecture, Sichuan Province, where cattle and sheep are commonly raised and fly exposure is frequent. The lesions were initially diagnosed as furuncles, and topical fusidic acid was ineffective. Laboratory tests showed marked eosinophilia (10.03×10 9 /L) and elevated total IgE (740.35IU/mL). Ultrasonography detected linear hyperechoic structures in the subcutaneous tissue and muscle layer, suggesting parasitic infestation. Because the posterior neck lesion had a pre-existing opening, wide incision was avoided. After infiltration of 2% lidocaine at the lesion base, a larva protruded through the opening and was removed intact with minimal tissue injury. Whole-genome shotgun sequencing of larval DNA, followed by host-read subtraction and de novo assembly, generated a 16,888-bp mitochondrial contig containing a full-length COI barcode region. The contig showed high similarity to the complete mitochondrial genome of H. sinense , confirming the diagnosis. The patient improved after albendazole and prophylactic antibiotics. Conclusions This case represents an accidental livestock-associated zoonotic cutaneous infestation in a child from a pastoral environment. In children with painful, treatment-resistant subcutaneous nodules and relevant cattle or fly exposure, myiasis should be considered. Ultrasonography-guided suspicion, minimally invasive extraction and sequencing-based molecular identification can improve diagnostic accuracy, reduce unnecessary tissue injury and support surveillance of rare zoonotic parasites.