Answer: fly larva; clinical presentation is consistent with myiasis
Many commented that identification becomes more challenging when arthropods are sectioned and stained since the external features are obscured or lost. However, there are still features that allow us to positively identify this as a fly larva such as the overall size and shape, mandibles, and yellow cuticular spines:
Unfortunately, definitive identification to the genus or species level is not possible without macroscopic examination of the larva. Therefore, we instead must rely on the clinical history, which would suggest that this larva is likely Cordylobia anthropophaga, otherwise known as the mango fly, tumbu fly, or putzi fly. This myiasis causing fly is endemic to parts of east and central Africa, including Uganda, where it is a common cause of human myiasis.
One reader commented on the difficulty of identifying fly larvae, particularly in settings without access to a microbiology lab with entomologic expertise. In these cases, a service that I find to be incredibly useful is the free and rapid e-consult service through the CDC DPDx team. Turn-around-time is generally < 24 hours. You can access their email and submission form HERE.