An attempt to study the economic loss arising from Schistosoma japonicum infection and the benefits derived from treatment.

From the northern and southern portions of Leyte Province, which are endemic for schistosomiasis, a total of 801 infected individuals were interviewed, examined, and classified into mild, moderate, severe and very severe forms of disease with an assumed loss of working capacity for each category. The frequency rate or number of spells of illness for the past year under observation were correlated with the degree of incapacity to get the total days lost per person per year. Following a series of computations, of which the disability rate was considered as the most important, a total of 45.4 days lost per infected person per year was arrived at. Treatment of the disease with praziquantel was carried out and the patients were followed up one year after treatment, at which time the same methodology was applied. The results show that the 45.4 days lost prior to treatment went down to 4 days lost. There was an economic gain of 41.4 days as a result of treatment. This can be expressed in terms of financial value if we consider half of the infected cases as breadwinners receiving a minimum wage. It should be noted that a number of assumptions in this study were made. It is, however, hoped that this work will serve as a guide and a starting point for others to carry out related studies on economic loss and subsequent economic benefits to justify budgetary requests/allocations for the implementation of various preventive and control measures.

Soil factors influencing the distribution of Oncomelania quadrasi, the intermediate host of Schistosoma japonicum, on Bohol Island, Philippines.

Soil conditions essential to the survival of Oncomelania quadrasi on Bohol Island in the Philippines were examined to clarify the factors limiting distribution of the snail and to develop a method for breeding large numbers of the snail in the laboratory. Soil samples in and around snail habitats were analysed and used for breeding experiments in the laboratory. Experiments using paddy soil derived from different parent materials revealed that the numbers of juvenile snails hatched varied widely between several soil samples. The best soils for reproduction generally had a pH of 5.6-7.9 and > 200 mg of available CaO/100 g. These soil factors, in addition to shade and moisture, determine the optimum conditions for the breeding of O. quadrasi in the field as well as in the laboratory. The determination of the optimum conditions for laboratory breeding of O. quadrasi and other intermediate snail hosts should facilitate detailed study of the hosts and the development of better methods to control or eradicate schistosomiasis and other snail-transmitted diseases.

Ultrasonographic and serologic abnormalities in Schistosoma japonicum infection in Leyte, the Philippines.

We have identified specific ultrasonographic changes in Schistosoma japonicum-infected patients associated with serologic indicators of general liver function. An ultrasonographic examination concomitant with hematologic and biochemical serum analyses was performed on 102 patients at the Schistosomiasis Hospital in Leyte, The Philippines. The ultrasonographic liver images were classified into four patterns, according to the development of periportal fibrosis and the patterns of echogenic bands. Eleven cases with a long-term infection showed typical septal formation (network pattern). Other ultrasonographic changes in the portal system, such as the severity of splenomegaly, did not correlate with the age of the study patients or the duration of their infection; however, the production of collateral vessels was clear in the group of older patients. Among various hematologic and biochemical serum indicators of liver damage, the serum levels of total bile acid (TBA) and procollagen-III-peptide (P-III-P) strongly correlated with the development of hepatic fibrosis and protal hypertension. These findings suggest that the ultrasonographic liver patterns classified here, along with the changes in serum levels of TBA and P-III-P, provide useful indicators for field monitoring of S. japonicum infection.

Improvement of ultrasonographic and serologic changes in Schistosoma japonicum-infected patients after treatment with praziquantel.

We previously reported ultrasonographic and serologic abnormalities in 102 patients infected with Schistosoma japonicum in Leyte, The Philippines. These patients were subsequently treated with praziquantel (3 x 20 mg/kg), and changes in ultrasonographic images and the serum levels of liver function markers in 52 patients were followed up every three months for a period of 17 months. Improvement in the thickening of the portal vein wall and the intensity of echogenic bands was detected six months after treatment with praziquantel. The level of splenomegaly was also reduced in 42 patients who originally did not show the production of collateral vessels. A significant decrease in the serum total bile acid (TBA) level was detected in all patients six months after treatment with praziquantel. However, significant ultrasonographic changes could not be detected in the patients classified as type 3, with severe hepatic fibrosis caused by the long-term infection. These results clearly show that ultrasonographic examination, along with data on the serum TBA level, provides a sensitive tool to monitor the severity of hepatic fibrosis and portal hypertension caused by S. japonicum infection, as well as the improvement resulting from praziquantel treatment.

Application of alcohol- or acetone-fixed Schistosoma eggs as an alternative to lyophilized eggs for the circumoval precipitin test.

Antigenicity of Schistosoma mansoni and S. japonicum eggs preserved in ethanol or acetone were assessed in a circumoval precipitin (COP) assay. The egg antigens were found to retain sufficiently their COP reactivity for the diagnosis of both schistosomiasis mansoni and japonica, although their reactivity became lower than that of lyophilized eggs. These alternative preparations for COP tests have advantages, such as keeping eggs directly in fixatives soon after the egg-purification process. Furthermore, evaporation-process may cause eggshell cleavages which facilitate the reaction. The possible usefulness of those eggs in COP assays in local endemic areas is discussed.

Schistosomiasis on Bohol Island, Philippines, with special emphasis on the successful discovery of new habitats of the vector snail, Oncomelania quadrasi, and area-wide mollusciciding.

In the endemic area of schistosomiasis on Bohol Island, we succeeded in locating seven new colonies of the vector snail, Oncomelania quadrasi, four in Trinidad and three in Talibon, in addition to six locations from which the snails were previously recorded. We were led by the proximity of the snail habitat to the residence of the infected individuals. In northern Bohol the continuous wet season would appear to make the major differences between the places that do and those that do not support O. quadrasi. Twice-yearly weed clearance and applying chemical molluscicides (niclosamide and phebrol) for the control of O. quadrasi have been extensively in effect over the snail colonies, since July 1986. Although it has not yet yielded satisfactory results in certain colonies, snails have been eliminated from six habitats in a period of two and a half years.

Negative conversion of COP (circumoval precipitation) reactions after selective mass chemotherapy on schistosomiasis japonica with praziquantel in Bohol, Philippines.

For the longitudinal survey of human schistosomiasis japonica in the villages of Sto. Tomas and San Vicente in the province of Bohol, Philippines, the circumoval precipitin (COP) test was used for case detection. Plasma collected by finger prick from the community people and lyophilized eggs of Schistosoma japonicum were used for the assay. Degree of precipitation at type 2 or 3 of Yokogawa et al. [1] was considered as positive. Selective mass chemotherapy with praziquantel was given to the patients including cases with only positive COP reactions. San Vicente and Sto. Tomas villages were examined in 1984 and 1982, respectively and followed up in 1986. Positive COP reactions were converted to negative in 82.1% or 55 out of 67 cases treated in 1984 and 1985 at San Vicente. Similarly, negative conversion was observed in 75.4% or 43 out of 57 cases treated in 1981 and 1982 at Sto. Tomas. The cases with persistent positive COP reaction after treatment were considered as incomplete cure or reinfection. The concentrated distribution of positive cases around the habitat of Oncomelania snails was observed at San Vicente where the prevalence of COP positives declined from 22.2% to 14.0% in 2 years. These results suggest that in the area with selective mass chemotherapy on schistosomiasis japonica, COP reactions of treated cases are converted to negative at high proportions in 2 years, and the positives detected by subsequent survey after 2 years are considered mostly as new infections or reinfections.

Immunogenetic factors involved in the pathogenesis of distinct clinical manifestations of schistosomiasis japonica in the Philippine population.

Immunogenetic factors were studied in 60 patients with schistosomiasis japonica in the Philippines, of whom 15 were characterized by marked hepatosplenic lesions and 45 characterized by cerebral symptoms. Immune responsiveness of the patients to schistosomal antigen was measured by T cell proliferation in vitro, and their HLA-A and -B specificities were typed. All but one hepatosplenic patients showed strong immune responsiveness to the schistosomal antigen, whereas both low and high responders were observed in the cerebral patients. A significant association between HLA-B40 and high responders to the schistosomal antigen was observed (P = 0.0458), and this HLA specificity was increased in frequency in the hepatosplenic patients. HLA-B16 was not observed in the hepatosplenic patients, but was common in the cerebral patients (26.5%) (P = 0.0255), and this HLA specificity was commoner in the low responders than in the high responders. These observations suggest that an HLA-linked gene governs the clinical manifestations of human schistosomiasis japonica by controlling immune responsiveness of the infected hosts to the schistosomal antigen.

Population studies on Oncomelania quadrasi, the snail intermediate host of Schistosoma japonicum, in the Philippines. 5. Quantitative analysis on successful snail control by land reclamation.

For the control of Oncomelania quadrasi, environmental modifications, i.e., clearing of vegetation, leveling of swampy depression and draining of stagnant water by channeling and excavation were carried out at 3 areas in Leyte, Philippines from 1974 to 1977. The change of snail population resulted in the land reclamation was evaluated by the methods previously developed by the population studies on this snail. As a result of statistical analysis based on y = log(x + 0.01) transformation and the antilogarithmic mean density A-y = (antilog -y) -0.01, the reduction of snail population was observed at 13 out of 18 sites studied at 3 project areas and the significant reduction was statistically confirmed at 9 sites of them. Particularly at Dagami area, which was a wide and heavily snail-infested land adjacent to Dagami Poblacion, the reduction rate of snail density reached 87.7% to 99.2% and some wet depressions have been converted into good rice fields with little snail infestation at the last survey.

An attempt to study the case fatality rate in Schistosoma japonicum infection in the Philippines.

As a sequence to a cross-sectional study on the clinical gradient of the disease by Pesigan et al., (1965) a follow-up of the subjects in that study was made after 12 years. Of the 135 untreated cases followed up, 23 (17.04%) died from various causes of which 12 (8.89%) had signs and symptoms attributable to schistosomiasis as the immediate cause or one of the main causes of death. This occurred in 1 to 11 years with an average of 5 years, which corresponds roughly to 1.78% of the infected cases per year. This is considered a conservative estimate because in the other deaths due to other diseases, schistosomiasis is a contributory cause. A diminishing severity of the disease was observed among the surviving patients which could imply that they must have developed some degree of immunity to the disease.

The cercarial emergence of Schistosoma japonicum from Oncomelania quadrasi under outdoor conditions in the Philippines.

The cercarial emergence of Schistosoma japonicum from Oncomelania quadrasi was observed under outdoor conditions in Leyte, Philippines. Nocturnal periodicity of the emergence within 24 hours was recognized. Peak emergence usually occurs between 18:00 and 20:00 and occasionally between 8:00 and 10:00. The peaks were usually synchronized with a sudden lowering of water temperature and light intensity and occasionally with their increase. As the nocturnal periodicity of the emergence was observed in the dark and outdoors, it was suggested that emergence might be dependent on temperature, which is secondarily influenced by photoperiodicity and light intensity.

Longitudinal study on Schistosoma japonicum infections in the Philippines. 4. Effect of mass-chemotherapy with praziquantel on incidence at Dagami, Leyte.

The effect of selective mass-chemotherapy with praziquantel at a dose of 60 mg/kg a day on the annual incidence of Schistosoma japonicum infection was examined by a follow-up study of 1,800 school children enrolled at 9 primary schools at Dagami Area, Leyte, Philippines. The incidence rates before mass-chemotherapy were 22.2, 24.2, 26.9, 9.6 and 28.4% in a period from school year (SY) 1975/76 to 1979/80, respectively, where the incidence of 9.6% in SY 1978/79 was probably due to extraordinary drought in the previous year. Egg positives including village people were treated and the numbers treated yearly were 22, 943, 273, 300 and 341 from SY 1978/79 to SY 1982/83, respectively. The incidence was reduced drastically as early as one year following the start of mass-chemotherapy, i.e., 8.4, no survey, 6.8 and 15.4%, from SY 1980/81 to SY 1983/84, respectively, and which demonstrated the efficacy of mass-chemotherapy on reduction of transmission.

Seroepidemiology of schistosomiasis japonica by ELISA in the Philippines. II. Unreliability of stool examination in the measurement of incidence.

It was shown in a previous study that a single quantitative stool examination (by technics currently used in the Philippines) is so sensitive that it underestimated by 50% the prevalence of schistosomiasis japonica in children detected by a single serologic assay (ELISA). This paper proves that measurement of incidence of the infection among these same children by stool examination is unreliable as well. Three important sources of error in the measurement of incidence by stool examination are: (a) the inclusion of already infected children in the group of presumably uninfected children in which conversion (change from negative to positive) is being measured; (b) the insensitivity of stool examination in identifying those who do acquire infection among the initially uninfected; and (c) spontaneous, possibly temporary, stool reversion. An overestimation of incidence results from error (a) because already infected children have 5-7 times the tendency to convert than do uninfected children; error (b) tends to produce an underestimation of incidence since stool examination will detect only about one-half of the children who do become infected; while error (c) also tends to cause an underestimation of incidence and is dependent on the frequency of stool examinations--34% of the conversions observed by multiple examinations may not be detected in a single year-end examination. The equivalent sources of error are insignificant when ELISA is employed to measure incidence. In the 3 years of observation, the annual incidence of schistosomiasis japonica measured by ELISA showed no significant change (13.5%, 16.7%, and 15.6%); on the other hand, the annual incidence measured by stool examination showed a significant reduction from 37.5% down to 16.0% and 15.1%. Significant sources of error invalidate measurements by stool examination; it is therefore concluded that incidence measurements have failed to produce acceptable evidence of reduction in transmission in the area of study in the 3 years of control operations. We believe that insistence on relying almost exclusively on the parasitologic technic can result in an erroneous evaluation of the control program currently being implemented.

Seroepidemiology of schistosomiasis japonica by ELISA in the Philippines. III. Selective mass chemotherapy with praziquantel in a control program.

After a pre-control (pre-treatment) prevalence rate of schistosomiasis japonica was established by stool examination and by ELISA in about 400 school children in school year 1979, annual prevalence rates were measured in the following 3 assessment years. From 54-80% of children found infected primarily by stool examination were treated with praziquantel 3-9 months before the assessment examinations. Both stool examination and ELISA showed statistically significant reductions of prevalence from the 1st to the 3rd assessment years (average reduction of 50% measured by stool examination and average reduction of 19% measured by ELISA). These reductions were expected as a result of the biologic activity of the effective schistosomicide; they are therefore not acceptable evidence of reduced transmission levels. By decreasing human sources of snail infection, an effective schistosomicide may have the epidemiologic impact of reducing transmission; assessment prevalence rates can be relevant indices of transmission levels only if the biologic effect of the schistosomicide is dissociated from its epidemiologic impact in a control program in which selective mass chemotherapy plays a dominant role. This dissociation was accomplished in this study by measurements in an essentially untreated group of "new" pupils, i.e., those who entered the school at the beginning of each assessment year. Overall prevalence rates among the "new" pupils did not show a significant reduction until the 3rd assessment year as measured by stool examination (reduction by 36% of pre-control level); as measured by ELISA, a significant reduction (by 15-17%) was detected in the 2nd and 3rd assessment years. The youngest children, and girls more than boys, were the most sensitive indicators of change.(ABSTRACT TRUNCATED AT 250 WORDS)