Leptospirosis in man and rodents in North and Northeast Thailand.

A seroepidemiological study of leptospirosis in man and rodents in the North and Northeast Thailand revealed that 0.27% of the rural people from three different ecologic areas were positive. The positivity rate has dropped dramatically when compared to a previous survey (28%). Of 1,135 wild rodents studied, 42 of 365 (11.5%) B. indica and 50 of 676 (7.4%) R. rattus were serologically positive. Others were negative. Only two of 157 R. rattus had positive cultures in which L. javanica and L. autumnalis were isolated. The study shows that wild rats are naturally implicated in human disease as a common reservoir and that the yearly rat eradication campaigns attributed as one of the effective factors in a major reduction of disease to a level of non significant public health hazard.

Schistosoma mansoni-like infection in Phayao Province, Northern Thailand.

Schistosome ova were found in the serosa of colon mass of a 65-year old Thai woman from Dokkhumtai District, Phayao Province. On the basis of the shape and microscopic appearance of the ova, they probably belonged to those of Schistosoma mansoni complex. In follow-up study, no ova were found by faecal examinations and rectal biopsy. There are evidences suggesting the presence of two distinct mammalian strains in Thailand: Orientobilhorzia harinasutai, a schistosome of water buffalo in Southern region and Tricula bollingi schistosome, a rodent schistosome in Northern region. This case is believed to be the first human schistosome infection with mammalian strain of S. mansoni complex in Thailand.

Schistosoma incognitum and its zoonotic potential role in Phitsanulok and Phichit provinces, northern Thailand.

A study on Schistosoma incognitum, a blood fluke of a variety of mammals, was conducted in different ecological conditions in Phitsanulok and Phichit, northern Thailand. The intermediate host of S. incognitum in permanent water habitats studied, i.e; swamps and ditches is Radix (Lymnaea) auricularia rubiginosa. Of 44,412 mollusks representing 13 different species collected from 24 water habitats studied, 7,186 were R. a. rubiginosa. S. incognitum infection rate in the snails was 2.1%. 483 Rattus rattus, 8 R. argentiventer, 280 Bandicota indica and 65 B. savilei were found infected with S. incognitum with an overall infection rate of 41.7%. R. argentiventer and B. savilei are reported as new mammalian hosts of the parasite. Also, 3.9% of dogs in the study area were found excreting S. incognitum eggs in their stools for the first time. The possibility of S. incognitum as a zoonotic potentiality to humans is discussed and is still an equivocal issue deserving further study.

Seroepidemiology of amoebiasis in the villagers in Phichit Province and urban slum dwellers in Bangkok, Thailand.

A serological survey was conducted in the villages of Phichit Province, Northern region and in the urban slum communities in Bangkok to determine whether amoebiasis was endemic in the areas and to determine the prevalence rates. Six rural villages, ethnically and culturally alike with a population of 3,019 and two urban slums with a population of 1,510 were surveyed. Sera were tested for indirect hemagglutination antibody (IHA) to Entamoeba histolytica and the stools examined for the parasite by direct smear method. Positive IHA titres (greater than or equal to 1:128) were detected in 482 (11%) and 176 (20%) sera, and E. histolytica found in 639 (2%) and 208 (3%) stool specimens of rural and urban slum populations respectively. Out of a total of 88 persons who showed significant levels of IHA antibodies to E. histolytica antigen, 5 had E. histolytica cysts in their stool specimens. The survey confirmed, serologically and parasitologically, that amoebiasis is endemic in the lower socio-economic areas. Substandard living and sanitary conditions within the areas were considered responsible for the transmission of the disease.

Study on pathogenicity and central nervous system migration of the larval stage of Gnathostoma spinigerum in experimental animals.

Studies were conducted on the pathogenicity and the route of migration to the central nervous system by the immature larval stage of G.spinigerum in experimental animals. Five mice and one rat showed signs of nervous tissue damage and CNS involvement. The significant findings were massive haemorrhagic areas and blood clot around large lower nerve trunk and spinal cord invasion by the worm. The possible roles of the immature larval stages of G.spinigerum in human was discussed.