Scanning electron microscopy of newly excysted metacercariae of Paragonimus westermani-like, Nakhon Nayok, Thailand.

Scanning electron microscope (SEM) observation of surface structure was done on newly excysted metacercariae of Paragonimus westermani-like (Nakhon Nayok, Thailand). The surface of the body was covered with numerous single-pointed tegumentary spines, large dome-shaped papillae, small one with a pit, and small one with a smooth surface were situated around the suckers. There were 27 to 30 of the small dome-shaped papillae with a pit around the oral sucker and 10 to 13 of the small ones with a smooth surface around the ventral sucker. The present report is the new record of excysted metacercariae of P. westermani-like (Nakhon Nayok, Thailand) by SEM.

Vitamin B1, B2 and B6 deficiency in primary school children infected with hookworm.

One thousand and seven hundred thirty-six school children from two districts in Nakhon Si Thammarat Province were screened for hookworm infection using the Kato-Katz stool examination technic. Two hundred students who have at least 2,000 eggs per g of stool were recruited into the program. The students were divided into six groups: groups 1, 2 and 3 were from Tha Sala district while groups 4, 5 and 6 were from Ronpibul district. Three milliliter blood samples were obtained from the cubital vein of each subject and were evaluated for erythrocyte transketolase activity (ETK) for vitamin B1, erythrocyte glutathione oxidoreductase activity (EGR) for vitamin B2, and erythrocyte aspartate aminotransferase activity (EAST) for vitamin B6. The school children were divided into three groups: those infected only with hookworm, those with both hookworm and Trichuris trichiura, and those whose stools show no parasite eggs. The results show that 10-20% of the school children are vitamin B1 deficient, about 40% to 80% are vitamin B2 deficient, and about 14% to 23% are vitamin B6 deficient. No correlation could be made between vitamin deficiencies and parasitic infection.

The natural first intermediate host of Paragonimus siamensis (Miyazaki and Wykoff, 1965) in Thailand.

The first intermediate host of six-known the Paragonimus species in Thailand had not been found until the Filopaludina (Siamopaludina) martensi martensi snail was discovered to maintain the cercariae of a Paragonimus species. An extensive study examined cercarial development through to adult worms by infecting 3 genera of 7 crab species with penetration of cercariae and feeding of snails containing such cercariae. These crabs provided many metacercariae which were fed to cats and bandicoots. The animals gave many Paragonimus adult worms which were characterized as Paragonimus siamensis by the following criteria: 6-lobed ovary and cuticular spines in groups. It is concluded that the Filopaludina martensi martensi snail is a susceptable natural first intermediate host of P. siamensis. Second intermediate hosts Somanniathelphusa brandti, S. sexpunctatum and S. bangkokensis were experimentally infected; prior to this study only S. germaini and S. dugasti had ever been naturally infected with metacercariae of this species.

Gnathostomiasis in Thailand: a survey on intermediate hosts of Gnathostoma spp. with special reference to a new type of larvae found in Fluta alba.

To clarify current status of gnathostomiasis in Thailand, a survey on intermediate hosts has been carried out at various localities since 1987. It was found that Fluta alba (Fresh water eel) as well as Channa striata (snake-headed fish) might be important in playing a role of transmitting the infection either among humans or reservoir animals. During the three years from 1987 to 1989, larvae of Gnathostoma spinigerum were found in 80-100% of F. alba obtained from markets in Nakhon Nayok, with a maximum recovery of 2,582 larvae per eel. Among larvae found in these eels, five were peculiar in possessing four rows of hooklets with complicated branches at the base. Epithelial cells of the intestine of these larvae contained 1-2 nuclei. These observations indicate that the larvae are different from those of reported species of Gnathostoma from Thailand including G. spinigerum, suggesting a possibility of the advanced third-stage larvae of G. malaysiae.

The route of migration of Paragonimus siamensis Miyazaki & Wykoff, 1965 in the white rat.

After they were ingested, the metacercariae of Paragonimus siamensis excysted in the stomach, penetrated through the stomach wall and the first 3 centimetres of small intestinal wall into the abdominal cavity, then penetrated into abdominal muscle. The worms stayed in abdominal muscle for about one week, then appeared again in the abdominal cavity before entering the pleural cavity and lungs; they also appeared in thoracic muscle, diaphragm, liver, and muscle of foreleg. The worm's size increased steadily until worm reaches sexual maturity then body size increased slowly. Genital primordia could be recognized at one week, of the reproductive system vitellaria were the last to appear at week 5, and eggs were first seen in the 7-week-old worms.