Ultrasound and DNA identify rare cattle-associated botfly in Chinese child

A 3-year-old boy with painful skin nodules was found to have a Hypoderma sinense larva beneath his skin.

Editorial illustration — not from the study.

A 3-year-2-month-old boy from Sichuan Province had painful nodules on his trunk, neck and shoulder for more than a month. The lesions were initially diagnosed as furuncles, but topical fusidic acid did not help. Blood tests showed marked eosinophilia and elevated total IgE, while ultrasound revealed structures consistent with parasites beneath the skin and in the muscle layer.

A larva was removed through an existing opening in one lesion, avoiding a wide incision. Whole-genome shotgun sequencing of the larval DNA produced a mitochondrial sequence that matched Hypoderma sinense, confirming the species. The child improved after treatment with albendazole and preventive antibiotics.

How the larva was identified

The case involved a 3-year-2-month-old boy living in Aba Tibetan and Qiang Autonomous Prefecture in Sichuan Province, where cattle and sheep are commonly raised and fly exposure is frequent. He had painful subcutaneous nodules on his trunk, posterior neck and right scapular region for more than one month.

The lesions had initially been treated as furuncles, without improvement from topical fusidic acid. Laboratory tests found eosinophilia of 10.03×10⁹/L and a total IgE level of 740.35 IU/mL. Ultrasound detected linear bright structures in the tissues, raising suspicion of a parasite.

A larva emerged after local anesthetic was applied at the base of a neck lesion and was removed intact with minimal tissue injury. Sequencing generated a 16,888-base-pair mitochondrial segment containing the full COI barcode region. Its close match to the complete mitochondrial genome of H. sinense confirmed the diagnosis of cutaneous myiasis caused by this species.

Why the diagnosis matters

Hypoderma infections are mainly associated with livestock, and human infection with H. sinense is rarely reported. Early lesions can look like ordinary furuncles, which may delay recognition and species-level diagnosis.

For children with painful subcutaneous nodules that do not respond to usual treatment, a history of cattle or fly exposure may provide an important clue. In this case, ultrasound helped suggest an infestation, while removing the larva through an existing opening limited tissue injury. DNA sequencing also provided a way to identify the parasite and could support monitoring of rare zoonotic infections.

Evidence and caveats

This is a single-patient case report, not a study of how common H. sinense infestation is or how well these diagnostic approaches work across patients. The diagnosis was supported by the clinical presentation, ultrasound findings, intact larval removal and mitochondrial DNA sequencing. The child improved after albendazole and prophylactic antibiotics, but this case cannot determine the separate effects of those treatments or establish a preferred treatment for all patients.

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