Chrysomya Bezziana - Medical Importance

Medical Importance

Chrysomya bezziana usually infects livestock causing myiasis. Myiasis is the infestation of tissue (living or dead) on a living mammal by fly larvae. Mammals such as sheep, dogs, cattle, pigs, and even humans can become infested.

The adult female will lay her eggs on superficial wounds in live animals preferring wounds that are several days old. Eggs of C. bezziana are commonly laid in the navel of newborn livestock species or on castration wounds in cattle. Eggs are also laid on open sores, ulcers, scratches externally or on mucus membranes throughout the body. Wounds as small as a tick bite are large enough for a female to lay her eggs.

When the eggs hatch, the larvae burrow into the animal’s living tissue and feed on it. Their common name, the “screwworm”, is derived from the maggots that embed themselves into the flesh of their host in a screw-like fashion. The larvae can burrow as deep as 15 centimetres (5.9 in) into the host’s living tissue. As the maggots feed and cause tissue damage, the wound produces a characteristic odor, which can go unnoticed by humans. However, this wound entices female flies to the wound and encourages them to lay their eggs there as well, causing further infestation.

C. bezziana is different from other fly species because tissue infestation can occur in the absence of necrotic tissue. The C. bezziana maggots may cause serious and permanent tissue damage. Extremely infested wounds can lead to death if not treated. The sexually mature adult imago feeds on decomposing corpses, decaying matter, excreta, and flowers. Due to their diet, these adult flies can be a mechanical vector for pathogens.