Comparison between Musca domestica and Chrysomya megacephala as carriers of bacteria in northern Thailand.

A comparison between the common house fly, Musca domestica, and the Oriental latrine fly, Chrysomya megacephala, was assessed for their potential as carriers of bacteria in urban areas of Chiang Mai Province, northern Thailand. C. megacephala was significantly more likely to carry bacterial species than M. domestica; however, no significant difference was found between the number of positive male and female flies within the same species. A total of 42 bacterial species were isolated. The most common bacterium isolated from M. domestica was coagulase-negative staphylococci (n=57) followed by Escherichia coli (n=10) and Viridans streptococci (n=10), while that of C. megacephala was non-fermentative gram-negative bacilli (n=59) followed by coagulase-negative staphylococci (n=54).

Forensically important fly maggots in a floating corpse: the first case report in Thailand.

The authors report herein the entomological evidence from the first documented forensic floating corpse in Thailand. The male remains of unknown name and age was found in the waterside of a reservoir in Lampang province, northern Thailand. Approximately 13-16 wounds resulting from sharp-edged material were found on the body. Numerous third-instar of blowflies Chrysomya megacephala (F) and Chrysomya rufifacies Macquart (Diptera: Calliphoridae) were collected, and the entomological evidence of the latter species could be used to estimate approximately 7 days of the postmortem interval. This is the first report of C. megacephala as forensic important fly species in Thailand. Additional research is needed to ascertain the effects of water on the succession and development of both fly species subsequently coming to associate with a corpse so treated in Thailand.

Effect of microwave irradiation on the blow fly Chrysomya megacephala (F.) (Diptera: Calliphoridae).

Chrysomya megacephala (F) is a blow fly species of medical importance, being pestiferous and a mechanical carrier of various microorganisms to human food. Various strategies to reduce the fly population in endemic areas are needed. We investigated the effects of microwaves at 2,450 MHz, with third-instar exposure times of 7, 10, 15, 30 and 60 seconds on the larvae. Survival of the larvae was monitored by their emergence. About 60% of the larvae lived after 7 seconds of exposure, most died by 15 seconds, and all were dead at 30 and 60 seconds. The number of survivals decreased with increasing exposure times. This indicates the effect of microwave irradiation on fly larval survival.

Some ultrastructural superficial changes in house fly (Diptera: Muscidae) and blow fly (Diptera: Calliphoridae) larvae induced by eucalyptol oil

Alterações ultraestruturais superficiais no terceiro estágio da mosca doméstica (Musca domestica) e da mosca varejeira (Chrysomya megacephala) induzidas pelo óleo de eucalipto foram observadas usando-se microscopia eletrônica de varredura. Imersos em 0,902 g/ml de óleo de eucalipto durante 30 segundos os tegumentos das larvas de ambas espécies mostraram aparência aberrante significativa da superfície corporal, particularmente edema do tegumento, formação de bolhas, fenda parcial e deformação das espículas.

Fine structure of the eggs of blowflies Aldrichina grahami and Chrysomya pacifica (Diptera: Calliphoridae)

We report here the fine structure of the eggs of blowflies Aldrichina grahami (Aldrich) and Chrysomya pacifica Kurahashi. For A. grahami, the plastron is wide and extends to almost the entire length of the eggs. The plastron near the micropyle is truncated. The polygonal patterns of chorionic sculpture bear a distinct swollen boundary. Regarding C. pacifica, the plastron is narrow and extends to almost the entire length of the eggs. The plastron near the micropyle bifurcates to a Y-shape, but the arms of the 'Y' are short. Information presented herein allows some distinctive features to differentiate among eggs of blowfly species.

Evaluation of the formalin-Tween concentration technique for parasitic detection

O método de detecção de parasitas por meio de sedimentação com Tween 20Õ foi comparado com o de formalina-éter. De um total de 297 amostras fecais examinadas, 72,1 por cento foram positivas. A técnica de formalina-Tween foi eficaz para demonstrar a presença de helmintos, particularmente ovos de Ascaris lumbricoides, Trichuris trichiura e ancilostomídeos. Entretanto, foi menos capaz de revelar protozoários. Este método é simples, de rápida execução e altamente sensível; revela infecções por parasitas, especialmente por meio da identificação de ovos de helmintos.

Intestinal parasitic infections in hill-tribe schoolchildren in Chiang Mai, northern Thailand.

We surveyed intestinal parasitic infections in hill-tribe schoolchildren residing permanently in Chiang Mai Province. The positive rate, of 403 stool specimens examined using the formalin-ether sedimentation technique, was 48.9%. No significant difference between male (50.8%) and female (47.1%) students was found for the infection. The most common protozoa was Entamoeba coli (40.9%), followed by Giardia lamblia (14.9%). The most common helminth was hookworm (13.4%), followed by Ascaris lumbricoides (8.0%), and Trichuris trichiura (6.9%). Opisthorchis viverrini, the most important liver fluke infection in northern Thailand, was found in only 1.5%. Children harbored 1-5 species of parasites, with the most being single infections (67.5%), followed by double infections (26.9%). This finding promoted an urgent need for the treatment of infected schoolchildren, and the prevention of re-infection must be underlined.

Comparison of the effectiveness of baits used in traps for adult fly collection.

The effectiveness of 6 different baits used in fly traps for adult fly collection was compared in October-November, 2000, near the cafeteria of Maharaj Nakhon Chiang Mai Hospital, Chiang Mai Province, northern Thailand. The baits used were fresh viscera (pork, beef and fish) and fresh meat (pork, beef and fish), with 500 g of each kind being used in each fly trap for each experiment. All were replicated four times. Pork viscera yielded the highest effectiveness (35.2%), followed by fish meat (30%). Four other kinds of bait showed relatively low efficiency, ie fish viscera (12.0%), beef viscera (9.0%), pork meat (8.4%) and beef meat (5.4%). The calliphorid Chrysomya megacephala was the most abundant fly species collected, while sarcophagids and muscid flies were found in much smaller numbers. The number of females was higher than males in all collections. Although all baits used were parts of animal carcasses that were very attractive for adult flies to feed upon and oviposit, the result of this study showed the differences in their effectiveness for fly collection, particularly during the late rainy season to early winter in Chiang Mai. Pork viscera showed the highest efficacy for metallic fly collection, but not for all species. Further study of suitable baits for the medically important fly species that exist in urban areas should, therefore, be performed.

Scanning electron microscopy of third-instar sarcophagid (Diptera: Sarcophagidae) recovered from a mummified human corpse in Thailand

The third-instar of an unidentified sarcophagid, recovered from a mummified body of a 32-yr-old Thai male was examined using scanning electron microscopy (SEM). Although the morphological features of this larva are similar to the other sarcophagid larvae, some features could be helpful for species identification, which is a basic requirement for estimation of postmortem interval in forensic investigation. These features included number and arrangement of papillae on the anterior spiracle, structure of spines, size of circumspiracular tubercles at caudal segment and branching peculiarity of the posterior spiracular hairs. This information could benefit future identification of the sarcophagid larvae that exist in Thailand

Pineapple juice as an agent for the digestion of fish prior to the harvesting of metacercariae.

The efficacy of crude pineapple juice obtained from Ananus comosus in digesting fish for the harvesting of trematode metacercariae was investigated. No significant difference was found between the total number of metacercariae detected from fish (Cirrhina jullieni) digested by acid pepsin and those digested by freshly prepared pineapple juice that was kept for 15 days at a temperature of either -4 degrees C or -75 degrees C. However, fewer metacercariae were found when using juice that had been kept for more than 30 days. This study showed that freshly prepared pineapple juice kept frozen for 15 days could be used instead of commercial acid pepsin to digest fish for harvesting metacercariae, some of which could be used for further biological studies.