The clinical scenario is one that travel medicine specialists encounter repeatedly. Myiasis, the infestation of living human or animal tissue by dipterous larvae, is endemic across much of Central and South America, sub-Saharan Africa, and other tropical regions, and it is increasingly diagnosed in travelers returning home from rural or wilderness destinations. The human botfly, Dermatobia hominis, is the classic culprit in the Americas. Its larvae develop within a subdermal cavity, breathing through a central pore that the host’s skin forms around the parasite. Patients typically present with a firm, dome-shaped, erythematous nodule that is tender to the touch, often with a tiny central punctum, and many report a crawling or moving sensation within the lesion. Because these features overlap with furunculosis, cellulitis, foreign-body granulomas, and even vascular tumors, misdiagnosis is common, and well-intentioned incision and drainage can rupture the larva, complicate extraction, and raise the risk of secondary bacterial infection.

In the case described by Isabella Andrea Bolaños Bermúdez and colleagues, the patient had developed persistent nodular lesions after rural travel, and the clinical picture alone was not decisive. The team turned to gray-scale ultrasonography using a 13-MHz high-frequency linear transducer, the kind of probe routinely available in emergency departments and radiology suites for evaluating soft-tissue complaints. Gray-scale imaging demonstrated an echogenic subcutaneous structure with posterior acoustic shadowing, a pattern consistent with a solid, calcified, or chitinous object within the tissue rather than a fluid-filled abscess cavity. Posterior acoustic shadowing occurs when the ultrasound beam is strongly reflected or absorbed at an interface, leaving a dark band deep to the structure, and in this context it pointed away from the simple pus collection the clinicians might otherwise have suspected.

The most compelling findings emerged when the investigators added color Doppler and dynamic, real-time assessment. Color Doppler ultrasonography, which maps the direction and velocity of blood flow by detecting frequency shifts in reflected sound waves, revealed surrounding hyperemia: an increased flow signal in the tissues encircling the lesion. Hyperemia is the vascular signature of inflammation, and it explains why the nodule looked and felt like an infection. Yet the decisive observation was inside the lesion itself. Real-time imaging captured rhythmic internal movement within the echogenic structure, the visible consequence of larval muscular activity as the maggot contracted and repositioned itself within its burrow. That single dynamic finding transformed a differential diagnosis that had included abscess, foreign body, and vascularized soft-tissue mass into a near-certain diagnosis of larval infestation, and it guided the team toward definitive mechanical extraction of the parasite rather than drainage or empirical antibiotic therapy alone.

The logic of the ultrasound findings is worth unpacking, because it illustrates why this modality is so well suited to the problem. An abscess appears on gray-scale imaging as a hypoechoic or anechoic collection, often with irregular walls and, on Doppler, peripheral hyperemia but no internal vascularity and no internal motion. A foreign body, such as a retained splinter, appears echogenic with shadowing but is motionless. A vascularized soft-tissue mass, such as a hemangioma or a hypervascular tumor, shows internal flow on Doppler but no rhythmic, peristalsis-like movement. A living larva uniquely combines several of these features: an echogenic, shadowing body; a surrounding inflammatory hypervascular rim; and, above all, spontaneous internal motion that can be documented on video and demonstrated to the patient and the clinical team. Recognizing this combination allows the radiologist to act as more than an image interpreter, effectively converting the ultrasound suite into the place where a parasitological diagnosis is made.

The Colombian report is not the first to describe sonographic detection of fly larvae, but it adds to a small but growing literature that deserves wider attention. Richter and colleagues documented sonographic detection of subcutaneous fly larvae in human myiasis in the Journal of Clinical Ultrasound in 2008, and comprehensive reviews by Francesconi and Lupi in Clinical Microbiology Reviews and by McGraw and Turiansky in the Journal of the American Academy of Dermatology have long emphasized the clinical spectrum of myiasis. What the new brief report contributes is a concise, imaging-focused description using modern high-frequency transducers and color Doppler, framed explicitly as a diagnostic clue for distinguishing myiasis from its common mimics. In an era of expanding global travel, in which emergency physicians in non-endemic countries will increasingly meet larvae that boarded a plane inside a patient, that framing has practical value far beyond a single case.

From a treatment standpoint, the ultrasound findings also change management in concrete ways. Definitive therapy for furuncular myiasis is mechanical removal of the intact larva, achieved by occluding the respiratory pore with petrolatum or other occlusive substances to force the larva upward, by manual expression after lidocaine infiltration, or by careful surgical extraction with forceps. Knowing in advance the exact depth, size, orientation, and viability of the larva allows the operator to plan the extraction, confirm afterward that the parasite has been removed in its entirety, and avoid leaving behind retained fragments that can perpetuate inflammation or seed infection. Ultrasound can likewise be used to survey for additional lesions in patients with multiple nodules, a recognized scenario in heavy infestations, and to follow the resolution of the inflammatory changes after removal. In resource-limited settings where ultrasound machines are increasingly available but parasitology laboratories and travel medicine expertise may be scarce, this represents a genuinely accessible diagnostic pathway.

The broader lesson for clinicians and travelers alike is one of calibrated suspicion. Any traveler returning from a rural or tropical destination with a persistent, enlarging, or tender skin nodule should be asked about insect bites, crawling sensations within the lesion, and exposure to forests, rivers, or livestock. The classic patient history of feeling movement under the skin, sometimes described as intermittent stabbing pain, should immediately raise the possibility of myiasis. When the diagnosis remains uncertain, high-frequency ultrasound with dynamic assessment and color Doppler offers a rapid, noninvasive, radiation-free method to confirm or exclude a living larva before any incision is made. The alternative, treating every such nodule as a bacterial abscess, risks unnecessary surgery, ruptured larvae, retained parasite fragments, and delayed relief for a condition whose definitive cure is often as simple as a well-timed extraction.

For the 54-year-old man at the center of this report, the wriggling signature on the ultrasound screen resolved a diagnostic puzzle that could easily have led to a fruitless drainage procedure. For the wider medical community, the case is a reminder that some of the most memorable diagnostic clues in medicine are also the most low-tech: watching, patiently and in real time, for something to move. As international travel continues to bring tropical parasites into contact with clinicians who rarely see them, reports like this one serve as an inexpensive form of collective education, ensuring that the next physician confronted with an unexplained post-travel nodule will at least consider placing a probe on the skin, turning on the Doppler, and waiting to see whether the lump gives itself away.

Subject of Research: Dynamic Doppler ultrasonographic diagnosis of travel-associated subcutaneous myiasis

Article Title: Subcutaneous Myiasis After Travel: Dynamic Doppler Ultrasonography as a Diagnostic Clue

Article References: Bolaños Bermúdez, I. A., Panqueva Giraldo, L. N., Torres Castiblanco, J. L., & Triana Rodríguez, G. A. (2026). Subcutaneous Myiasis After Travel: Dynamic Doppler Ultrasonography as a Diagnostic Clue. Acta Parasitologica, 71(5), Article 204. https://doi.org/10.1007/s11686-026-01386-y

Image Credits: AI Generated

DOI: 10.1007/s11686-026-01386-y

Keywords: cutaneous myiasis, Dermatobia hominis, ultrasonography, Doppler ultrasound, travel medicine, soft-tissue infection, parasitology, subcutaneous larva, diagnostic imaging, hyperemia, Subcutaneous, Myiasis