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.

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 m L of a suspension 107-108 CFU/m L of each symbiotic bacterium. Distilled water and Escherichia coli ATCC襅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(b NBP22.2_TH). The mortality rate of Aedes albopictus was between 82% and 96% at 96 h after exposure to Xenorhabdus indica(b KK26.2_TH). Low effectiveness of distilled water and Escherichia coli ATCC襅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.