Molecular screening of Plasmodium infections among migrant workers in Thailand.

Background & objective: A cross-sectional study was conducted to determine the prevalence of Plasmodium infections among migrant workers in Thailand. Methods: A total of 241 migrants at Kanchanaburi, Pathumthani and Nakornpathom provinces of Thailand were recruited in our surveillance. Blood samples were examined for human malaria parasites by using microscopy and semi-nested multiplex PCR (SnM-PCR). Results: Laboratory diagnosis revealed 6.2% total positive rate. As compared to microscopy (26.7%), SnM-PCR was more sensitive (93.3%) for malaria. Plasmodium falciparum was predominant than P. vivax (53% : 40%, respectively). The majority of positive cases were from Myanmar workers who had low parasitaemia and without symptoms. The highest prevalence (13.7%) was found among migrant workers from Kanchanaburi province in western Thailand. Conclusion: These findings indicate risk of malaria transmission from migrant workers. Malaria surveillance should be included in the health-screening program for migrants in Thailand to manage this health risk.

The exsheathment of Necator americanus infective larvae.

Infective 3rd-stage larvae of Necator americanus were treated with human sweat under various conditions, and compared with human serum, 1.5% saline solution, and distilled water. The infective larvae were observed under inverted microscopy. The highest percentage (14.0%) of the exsheathed larvae was found in human sweat after 2 hours' incubation at 37 degrees C. The proportion of exsheathed larvae in human sweat was significantly different from human serum (p<0.001), 1.5% saline solution (p<0.001), and distilled water (p<0.001). This may reflect the effect of human sweat on the process of skin penetration by Necator americanus larvae.

Methylene blue staining method for identification of Opisthorchis viverrini egg.

Methylene blue staining method was used to distinguish O. viverrini eggs from Haplorchis taichui and Prosthodendrium molenkampi eggs. All eggs were obtained from dissected adult worms, fixed in 10% formalin, and stained with methylene blue prior to light microscopy observation. The distinct musk-melon-like texture of the O. viverini eggshell surface and the thread-like texture of H. taichui eggshell surface were recognized, while P. molenkampi eggs showed a smooth eggshell. We also evaluated the sensitivity and specificity of the method by training investigators to differentiate surface textures. After training, the investigators were randomly tested with 10 slides containing fluke eggs. The sensitivity and specificity were 95% and 95%, respectively.