Evaluation of Larval Therapy Compared to Antibiotic Therapy in the Treatment of Skin Wounds in Rabbits

Larval therapy (LT) is a therapeutic modality that uses larvae of necrophagous flies for the treatment of wounds. The use of this therapy presents several benefits, due to the action of the larvae that remove necrotic tissue selectively, exercising antimicrobial action, and promoting healing. There are situations in which LT proves to be the only or the best alternative for the patient, such as wounds infected by multidrug-resistant microorganisms or when treatment difficulties may lead to an indication for amputation. The purpose of this study was to compare the efficiency of LT, using larvae of Chrysomya megacephala, with that of antibiotic therapy in the treatment of cutaneous wounds infected with Pseudomonas aeruginosa. Twenty-four rabbits were used to perform the experiment, distributed in four groups: group 1, induced wound without bacterial infection; group 2, induced wound with bacterial infection; group 3, induced wound with bacterial infection and antibiotic therapy; group 4, induced wound with bacterial infection and LT. The macroscopic, microscopic, and statistical analyses indicated that LT was as effective as antibiotic therapy in wound healing.

First Use of an Entire Age Cohort to Evaluate the Role of Sex in the Development of the Forensically Important Chrysomya megacephala (Diptera: Calliphoridae)

The age of a blow fly larval specimen found on a body can be used to estimate a minimum postmortem interval by comparing a physical feature of a larva (e.g., length) to a reference growth curve created under similar conditions. A better understanding of factors known to influence growth rates would lead to more precise estimates of larval age. A factor known to influence insect development, but almost always lacking in blow fly larval growth curves, is sex. We wanted to understand how sex might affect larval growth rates and therefore lead to more precise age estimates, in the forensically important blow fly Chrysomya megacephala (F.). We examined sex for an entire age cohort at 70 h and found on average, males were longer than females. To assess whether this difference would cause an investigator to interpret the results differently if comparing a larval specimen of one sex based on reference data from the other sex, we made sex-specific 95% prediction intervals. We did not find a difference when comparing a male specimen with the female prediction interval, but did find more females outside the interval than expected using the male interval. All females outside the male interval were shorter. Investigators commonly remove the largest individuals from a body to estimate age, so these females are less likely to be chosen. These results do not support the generation of sex-specific growth curves for this species, though this study's narrow scope means more information is required before making a final conclusion.

Effect of Temperature and Tissue Type on the Development of the Forensic Fly Chrysomya megacephala (Diptera: Calliphoridae)

Chrysomya megacephala Fabricius is one of the most common myiasis-causing and carrion-feeding fly species in the tropics. This species has a worldwide distribution due to globalization and therefore is of critical importance to the public health sector and forensic investigations. Development studies carried worldwide show that Ch. megacephala reared at similar temperatures may require different amounts of time to complete their cycle of growth. The present study determined for the first time the life-history information of this species in Sri Lanka. Chrysomya megacephala colonies were reared on three different food sources (bovine muscle, swine muscle, and swine liver) considering the most common forensic entomology rearing mediums and the capability of Ch. megacephala to cause myiasis in cattle. Furthermore, colonies were reared at four temperature regimes representing several specific development conditions of this blowfly: 1) 20°C representing the estimation of the lower developmental threshold for this species in Sri Lanka; 2) 25 and 27°C representing typical room/environmental temperatures in Sri Lanka; and 3) 38°C as this is the typical living animal temperature, representing myiasis conditions. Results show that temperature significantly affected larval length and width over time; however, tissue type was not a significant factor. The fastest development was recorded at 38°C for immature feeding on bovine muscle (162.15 h), followed by those fed swine liver (184.15 h) and swine muscle (208.00 h). The calculated minimum temperature threshold for Ch. megacephala was 13°C. Data generated will be crucial for future forensic investigations involving living or deceased individuals colonized by this species.