Lucilia cuprina (Wiedemann; Diptera: Calliphoridae) is a facultative ecto-parasitic fly, distributed throughout the temperate and subtropical regions of the world. This blow fly species is of medical, veterinary, and forensic importance due to it being used in maggot debridement therapy (MDT), a causative agent of myiasis, and a decomposer of vertebrate carrion. The current study examined the combined effects of temperature and tissue type on the development of L. cuprina. Specimens were reared on three tissue types; swine muscle, swine liver, and bovine muscle at 20°C, 25°C, 27°C, and 38°C. The optimum condition for L. cuprina development was for immatures reared on bovine muscle (287.4 h) followed by those reared on swine muscle (288.0 h) and swine liver (288.4 h) at 27°C. The minimum temperature threshold of L. cuprina was deduced to be 14°C. No significant differences in larval width and length over time were determined for the tissue type.

Background

Myiasis, or the invasion of living tissues of humans and other mammals by dipterous larvae, is considered the world's fourth most common travel-associated skin disease after cutaneous larval migrants, pyodermas, and pruritic arthropod-reactive dermatitis.

Method

The present study recorded the cause, anatomical position, and severity of the wounds of myiasis patients admitted to 11 hospitals located in the central region of Sri Lanka from February 2016 to July 2017.

Results

Altogether, 28 myiasis incidences were noted within the study period. Of the total identified myiasis patients, nine were female while the remainder were male. The greatest number of patients was recorded from the Mawanella Base Hospital and Peradeniya Teaching Hospital (seven patients each). The ages of recorded patients ranged between 30 and 92 years with the average being 59.4 years. The greatest number of myiasis cases was diagnosed in wounds located in lower limbs (24). In addition, scalp, urogenital, and umbilical infestations were recorded. Eighteen out of the total patients had diabetes mellitus, and two patients suffered from filarial lymphedema. Psychiatric illnesses were a predisposing factor of larval infestation of six patients including the recorded scalp and two urogenital myiasis patients. Of the 28 myiasis cases, 27 were caused by the old world screwworm, Chrysomya bezziana Villeneuve (Diptera: Calliphoridae), and one by the blowfly, Chrysomya megacephala Fabricius (Diptera: Calliphoridae).

Conclusion

The awareness of patients with ulcers about this disease helps to decrease further risk of being infected by fly larvae.

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.