Schistosoma japonicum-like infection in Phichit province, northern Thailand: a case report.

A case of human schistosomiasis from Phichit Province is presented. Schistosome eggs were found in the ileo-caecal mass of a 44-year old woman, native of Sak-Lek, Muang District. Histologic pictures revealed an early acute granulomatous lesion which consisted of predominantly eosinophils without multinucleated giant cells and fibrotic change suggesting a recent infection. On the basis of the shape and microscopic appearance of the eggs, they are smaller than those described previously for Schistosoma japonicum, probably those of S. mekongi, a related species. This is the third histologic-confirmed case of schistosomiasis in this locality. Addendum: At the time of the manuscript preparation, another case of schistosomiasis was diagnosed. A 55-year old man who lives entirely in the very close adjacent village to the present case was admitted to the Ramathibodi Hospital, Bangkok with chronic hepatosplenomegaly in January 1986. Amyloidosis was suspected and rectal biopsy revealed schistosome eggs, some contained miracidia with varying degrees of degeneration, some were empty and/or fragmented shells and were surrounded with fibrotic changes and chronic cellular infiltration (Fig. 5). They were identical to those of Schistosoma japonicum. Several fecal examinations, miracidium hatching and COPT yielded negative results. This finding showed significantly that all schistosomiasis cases reported from this locality, except the second one, were in the old age group of 40 and above. Further epidemiologic investigation is in progress to delineate this locality as a potential endemic area for this infection.

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.

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 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.

Potential health hazards of the water resources development: a health survey in the Phitsanulok Irrigation Project, Nan River Basin, Northern Thailand.

A health survey was carried out among residents of 33 villages under the Phitsanulok Irrigation Project Area, Nan River Basin, Northern Thailand, whereby general health conditions were examined including intradermal tests for schistosomiasis japonica, stools for intestinal parasites and sera tested by circumoval precipitin test for antibodies to S. japonicum and by agglutination test for leptospiral infection. Health investigations revealed that 913 (60.9%) of 1,499 people examined had experienced gastro-intestinal disorders, 254 (17%) had poor oral hygiene and a few had mild anemia. 799 (62%) of 1,298 examined had intestinal parasites. Hookworm (45%) was most common, followed by Opisthorchis viverrini (20%), Entamoeba coli (10%), Ascaris lumbricoides (6%), intestinal flukes (2%), Enterobius vermicularis (1%) and Giardia lamblia (1%). 149 (10%) of 1,422 people gave positive skin reaction to crude S. japonicum antigen. Circumoval precipitin test was strongly positive in 7 (1.6%) persons out of 449 tested for schistosome infection and 6 (4.0%) out of 1,358 people were positive for leptospiral infection. The significant endemic diseases as potential health problems in this water resources development are discussed.

Sewage stabilization pond: The effects on Schistosoma Mansoni transmission.

The "facultative" sewage-stabilization pond was investigated with respect to transmission of S. mansoni. The results of field and laboratory experiments suggest that the ecologic factors i.e., physical and chemical play important roles in a combined interplay affecting the hatchability of S. mansoni eggs, infectivity of miracidia of S. mansioni and the potential existence of the planorbid snails host, B. glabrata. The results seem to indicate the successful reduction of S. mansoni transmission in the pond itself. If the pond is designed properly in terms of depth, detention time, etc., it will serve as an efficient barrier for transmission of S. mansoni. It is expected that the same would be true for other human schistosomes.

Nidal delineation of Thailand: an approach to disease ecology in major nidal base regions.

Provisional nidal base regions have veen delineated for Thailand. The nidal base regions so derived were compared by computing the percentages of species common to pairs of provinces (coefficient of community, CC). The results provided a CC matrix and dendrogram showing the relationship between regions, combined with the general geographic and climatologic conditions. Six ecological regions have been designated, of which five are classified as super provinces (Northeast, Central, East, South and Far South), while only one is a subregion (North). Problems of error in the data are discussed and the need for further accurate analysis to further the goal of control of disease.