Apichat Vitta

Survey of Angiostrongylus cantonensis in rats and giant African land snails in Phitsanulok province, Thailand.

OBJECTIVE To survey the Angiostrongylus cantonensis (A. cantonensis) or the rat lungworm in a rat, definitive host, and in a giant African land snail (Achatina fulica), the intermediate host, in Phitsanulok, Thailand. METHODS Rats and giant African land snails were captured from Tha Pho sub-district, Phitsanulok, Thailand. Rats were killed and examined for adult A. cantonensis. The artificial digestion method following Baermann technique were used for isolation third stage larvae of A. cantonensis. RESULTS Sixty-two rats were captured and they were identified as Rattus argentiventer, Rattus rattus (R. rattus), Bandicota savilei, and Bandicota indica but only one animal (R. rattus) of 62 rats (1.61%) was positive with adult worm of A. cantonensis. The third stage larvae of A. cantonensis were examined on 307 Angiostrongylus fulica snails. It was found that the overall infection rate was 12.38% (38 infected out of 307 Achatina snails). CONCLUSIONS This study demonstrates that A. cantonensis is available in the natural hosts of Phitsanulok. This suggests that the transmissions of this parasite to human may occur in this region.

Morphology and Developmental Rate of the Blow Fly, Hemipyrellia ligurriens (Diptera: Calliphoridae): Forensic Entomology Applications

Hemipyrellia ligurriens (Diptera: Calliphoridae) is a forensically important blow fly species presented in many countries. In this study, we determined the morphology of all stages and the developmental rate of H. ligurriens reared under natural ambient conditions in Phitsanulok province, northern Thailand. Morphological features of all stages based on observing under a light microscope were described and demonstrated in order to use for identification purpose. Moreover, development time in each stage was given. The developmental time of H. ligurriens to complete metamorphosis; from egg, larva, pupa to adult, took 270.71 h for 1 cycle of development. The results from this study may be useful not only for application in forensic investigation, but also for study in its biology in the future.

Screening of the Antimicrobial Activity against Drug Resistant Bacteria of Photorhabdus and Xenorhabdus Associated with Entomopathogenic Nematodes from Mae Wong National Park, Thailand

Photorhabdus and Xenorhabdus are symbiotic with entomopathogenic nematodes (EPNs) of the genera Heterorhabditis and Steinernema, respectively. These bacteria produce several secondary metabolites including antimicrobial compounds. The objectives of this study were to isolate and identify EPNs and their symbiotic bacteria from Mae Wong National Park, Thailand and to evaluate the antibacterial activities of symbiont extracts against drug resistant bacteria. A total of 550 soil samples from 110 sites were collected between August 2014 and July 2015. A total of EPN isolates were obtained through baiting and White trap methods, which yielded 21 Heterorhabditis and 3 Steinernema isolates. Based on molecular identification and phylogenetic analysis, the most common species found in the present study was P. luminescens subsp. akhurstii associated with H. indica. Notably, two species of EPNs, H. zealandica and S. kushidai, and two species of symbiotic bacteria, X. japonica and P. temperata subsp. temperata represented new recorded organisms in Thailand. Furthermore, the association between P. temperata subsp. temperata and H. zealandica has not previously been reported worldwide. Disk diffusion, minimal inhibitory concentration, and minimal bactericidal concentration analyses demonstrated that the crude compound extracted by ethyl acetate from P. temperata subsp. temperata could inhibit the growth of up to 10 strains of drug resistant bacteria. Based on HPLC-MS analysis, compound classes in bacterial extracts were identified as GameXPeptide, xenoamicin, xenocoumacin, mevalagmapeptide phurealipids derivatives, and isopropylstilbene. Together, the results of this study provide evidence for the diversity of EPNs and their symbiotic bacteria in Mae Wong National Park, Thailand and demonstrate their novel associations. These findings also provide an important foundation for further research regarding the antimicrobial activity of Photorhabdus bacteria.

Larvicidal activity of Xenorhabdus and Photorhabdus bacteria against Aedes aegypti and Aedes albopictus

Objective: To evaluate the efficacy of symbiotic bacteria, Xenorhabdus indica, Xenorhabdus stockiae, Photorhabdus luminescens subsp. akhurstii and Photorhabdus luminescens subsp. hainanensis as a larvicide against Aedes aegypti and Aedes albopictus. Methods: Larvae (L3-L4) of Aedes aegypti and Aedes albopictus were given 2 mL of a suspension 107-108 CFU/mL of each symbiotic bacterium. Distilled water and Escherichia coli ATCC® 25922 were used as the control. The mortality rate of the larval mosquitoes was observed at 24, 48, 72 and 96 h. The experiment was performed in triplicates. Results: The larvae of both Aedes species started to die at 24 h exposure. Aedes aegypti showed the highest mortality rate (87%-99%), 96 h after exposure to Xenorhabdus stockiae (bNBP22.2_TH). The mortality rate of Aedes albopictus was between 82% and 96% at 96 h after exposure to Xenorhabdus indica (bKK26.2_TH). Low effectiveness of distilled water and Escherichia coli ATCC® 25922 were observed in both Aedes larvae, with a mortality rate of 2% to 12%. Conclusions: The study confirms the oral toxicity of Xenorhabdus and Photorhabdus bacteria against Aedes spp. Xenorhabdus stockiae and Xenorhabdus indica may be an alternative agent for control Aedes spp. This is basic information for further study on the mechanism of action on Aedes larvae or application to control mosquito larvae in the community.

Identification of entomopathogenic nematodes and symbiotic bacteria from Nam Nao National Park in Thailand and larvicidal activity of symbiotic bacteria against Aedes aegypti and Aedes albopictus

Entomopathogenic nematodes (EPNs) that are symbiotically associated with Xenorhabdus and Photorhabdus bacteria can kill target insects via direct infection and toxin action. There are limited reports identifying such organisms in the National Park of Thailand. Therefore, the objectives of this study were to identify EPNs and symbiotic bacteria from Nam Nao National Park, Phetchabun Province, Thailand and to evaluate the larvicidal activity of bacteria against Aedes aegypti and Ae. albopictus. A total of 12 EPN isolates belonging to Steinernema and Heterorhabditis were obtained form 940 soil samples between February 2014 and July 2016. EPNs were molecularly identified as S. websteri (10 isolates) and H. baujardi (2 isolates). Symbiotic bacteria were isolated from EPNs and molecularly identified as P. luminescens subsp. akhurstii (13 isolates), X. stockiae (11 isolates), X. vietnamensis (2 isolates) and X. japonica (1 isolate). For the bioassay, bacterial suspensions were evaluated for toxicity against third to early fourth instar larvae of Aedes spp. The larvae of both Aedes species were orally susceptible to symbiotic bacteria. The highest larval mortality of Ae. aegypti was 99% after exposure to X. stockiae (bNN112.3_TH) at 96 h, and the highest mortality of Ae. albopictus was 98% after exposure to P. luminescens subsp. akhurstii (bNN121.4_TH) at 96 h. In contrast to the control groups (Escherichia coli and distilled water), the mortality rate of both mosquito larvae ranged between 0 and 7% at 72 h. Here, we report the first observation of X. vietnamensis in Thailand. Additionally, we report the first observation of P. luminescens subsp. akhurstii associated with H. baujardi in Thailand. X. stockiae has potential to be a biocontrol agent for mosquitoes. This investigation provides a survey of the basic diversity of EPNs and symbiotic bacteria in the National Park of Thailand, and it is a bacterial resource for further studies of bioactive compounds.

Species composition and nocturnal activity of phlebotomine sand flies (Diptera: Psychodidae) inhabiting a limestone cave in Thailand

ABSTRACT: We investigated the nocturnal activity of cave-dwelling sand flies at different time intervals and determined their species composition and seasonal variation. Sand flies were captured on one night each month using CDC light traps from 18:00-06:00 with the collecting bag being changed every two h between February, 2010 and January, 2011. A total of 18,709 individuals, including 10,740 males and 7,969 females, was collected. The overall ratio between male and female specimens was 1:0.74. The collected specimens included 14 species from four genera, Chinius, Idiophlebotomus, Phlebotomus, and Sergentomyia. Sergentomyia phadangensis was the most abundant species (comprising 31.9% of the collected individuals), followed by Se. anodontis (22.8%) and Ph. mascomai (18.2%). The highest number of specimens was collected in July (15.6%), followed by May (15.5%) with the peak of collection recorded at the time interval of 00:01–02:00, followed by 22:01–00:00. However, there were no significant differences observed among time intervals of sand fly collections (p=0.154). Observations of the nocturnal activity of male and female sand flies throughout the night suggest that phlebotomine sand flies show the greatest activity level after midnight.

Prevalence of intestinal parasitic infections among schoolchildren in Phitsanulok Province, Northern Thailand

Abstract Objective To determine the prevalence of intestinal parasites in children from six schools located in Bang Rakam and Mueang Districts, Phitsanulok Province, Northern Thailand. Methods The study sites were the following six schools: Wat Krab Phuang, Wat Wang Ped, Wat Tha Ko, Wat Sao Hin, Wat Kung Waree and Wat Sakat Namman. Fecal samples were collected from 352 students in the age range 7-15 years old, and examined for intestinal parasites by formalin-ethyl acetate concentration method. Additionally, Scotch tape technique was used to recover Enterobius vermicularis eggs from 576 children. Result It was found that the overall prevalence of intestinal parasites among 352 examined students was 5.4%: Strongyloides stercoralis (2.5%), Entamoeba coli ( E. coli ) (0.6%), Giardia lamblia (0.6%), Enterobius vermicularis (0.6%), hookworm (0.3%), hookworm and E. coli (0.3%), hookworm and Trichuris trichiura (0.3%) and Strongyloides stercoralis and E. coli (0.3%). The overall prevalence of enterobiasis among 576 schoolchildren by Scotch tape technique was 14.1%. The highest infection rate (19.3%) was observed at Wat Sao Hin School. The selective anthelminthic drugs were administered to all positive cases. Conclusions In this study, low prevalence of parasitic infections was demonstrated among schoolchildren in Phitsanulok Province. However, the control and prevention including the transmission of parasites detected should be explained for more concern and attention and the proper hygienic health education should be implemented.