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.

Seroepidemiology of schistosomiasis japonica by ELISA in the Philippines. I. Underestimation by stool examination of the prevalence of infection in school children.

In a longitudinal seroepidemiological study in the Schistosoma japonicum endemic area of Leyte, the ELISA technique to determine prevalence and incidence rates in elementary school children was compared with similar determinations made by a modified quantitative stool examination (MIFC). In the area of this study, Barrio Salvador, Tanauan, Leyte, the ongoing schistosomiasis japonica control program in the Philippines is dependent on stool examination by MIFC and/or the quantitative thick smear (Kato-Katz) for measurement of prevalence and incidence. Over a 3-year period with multiple periodic examinations, infection rates were measured and the serologic technique was compared to stool examination in 598 untreated children (mostly 7-10 years of age) of Salvador Elementary School. A group of 150 school children from a non-endemic area, Milagros, Masbate, provided sera as a reference negative control. ELISA results are expressed as ELISA activity (EAc) in reference to a positive control serum pooled from parasitologically confirmed cases, dilutions of which were always included in each assay. A convenient positive-negative discrimination level was chosen based on the EAc values obtained from 170 stool-positive Salvador pupils and the 150 pupils of the non-endemic area. Using the chosen discrimination level, ELISA in this study had a sensitivity of 98% and a specificity of 96%. ELISA was significantly more sensitive than stool examination in detecting infections; only 28% of the children were stool positive on a single examination in contrast with 56% positive by ELISA. A single stool examination underestimated serologic positives by 50% while two stool examinations 4 months apart reduced the underestimate to 29%. The underestimation varied by age and sex, and showed no consistent pattern in this regard. Stool-positive children had a wide variation of egg counts with a geometric mean of 6.4 eggs/g of stool, with 52% of the stool positives excreting only 1-5 eggs/g. A high percentage of infected children have a misdiagnosis of infection by stool examination. This has, in the past, resulted in many being misclassified as noninfected. This erroneous classification has serious consequences on the measurement of prevalence and incidence, on studies of clinical manifestations of the disease, and on the evaluation of serologic techniques for diagnosis. Stool examination does not give an accurate measurement of prevalence, and therefore it cannot be relied upon for the evaluation of the current control program. It is recommended that the capability to undertake serodiagnostic tests for schistosomiasis japonica be encouraged and adopted in the Philippines for field

Lymphocyte responsiveness to phytohemagglutinin and to worm and egg antigens in human schistosomiasis japonica.

Using a whole blood culture technique, lymphocyte responsiveness was assayed as 3H thymidine incorporation in 41 individuals infected with Schistosoma japonicum. In comparison with controls, response to phytohemagglutinin (PHA) was suppressed but was unrelated to egg excretion levels or duration of infection. Reactivity to whole worm antigens was significantly greater in individuals with a higher level of egg excretion and presumably greater infection intensity. The response to egg antigens significantly decreased with age and duration of infection. Some individuals with a depressed responsiveness to PHA maintain a high reactivity to parasite antigens, suggesting that different subpopulations of lymphocytes may be involved in these measurements.

Schistosomiasis japonica in Barrio San Antonio, Basey, Samar , The Philippines. I. Epidemiology and morbidity.

Barrio San Antonio is a coastal settlement on the San Juanico straits in the municipality of Basey on the island of Samar, the Philippines. It has a population of approximately 1,900 in 320 households. Initially, 851 residents (45%) of 240 households participated in this survey to determine the prevalence and intensity of Schistosoma japonicum infection, and morbidity as indicated by associated hepatomegaly and splenomegaly. As a result of an initial single stool examination of 1 ml by a modified formalin concentration technique, 40% of this population was found to be infected. On subsequent examinations, with the addition of serologic techniques and recording the history of therapy, approximately 70% of this population was found to be infected with S. japonicum after the age of 10 years. If judged by the number of eggs produced per milliliter of feces, infection intensity in this population might be considered to be low. However, 25% (73 of 391 positives on single examination) exhibited schistosomal hepatomegaly or hepato-splenomegaly and had a mean egg count of 10.9. Those infected but without hepatomegaly had a slightly lower mean egg count of 8.4. Of the infected males with hepatomegaly, 75% were 19 years of age or less and 45% of these were producing less than 10 eggs/ml of stool. Of infected females with hepatomegaly, only 28% were 19 years of age or less, and 68% of these were producing less than 10 eggs/ml. Abdominal pain, distress, diarrhea, and dysentery were significantly more frequent in the infected than uninfected persons, and this frequency was related to egg output. The heights and weights of these infected individuals were less than those of the uninfected members of this population and significantly less than the Filipino norm. The small percentage of the infected population (6.6%) that were producing 51% of the eggs had a mean egg count of approximately 260 with a mean age of 33.7. In this group, 7 of the 22 individuals were in the age group 10--14 years and 15 were above 20 years of age. Although some individuals of Barrio San Antonio have sought therapy, this population and area have been largely unstudied and have not up to the present been involved in control or mass chemotherapy programs. The findings of this survey give an opportunity to determine the impact of such programs when they are instituted in this area.

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)

Schistosomiasis japonica in Barrio San Antonio, Basey, Samar in the Philippines. IV. "Atypical" precipitates in the circumoval precipitin test--a reaction of recent infection.

Morphologically distinct circumoval precipitin reactions, not having the usual "segmented" appearance, are characteristic of recently acquired infection of man with Schistosoma japonicum. In contrast to the precipitins seen in plasma of those with chronic infections, reactions of recent infection (RRI) are commonly, large, vacuolated blebs or, if elongate, are smooth and vacuolated in structure. Recognition of these RRI provides a practical, simple method to study incidence of infection and the techniques used are readily accepted by children in primary school grades.

Analysis of the immunoglobulins responsible for the circumoval precipitation reaction.

Two morphologically distinct types of circumoval precipitates (COP) have been observed in human Schistosoma japonicum infections. An elongated segmented COP occurs in chronic human infections. An unsegmented "reaction of recent infection" (RRI) occurs in serum from humans with recently acquired infections and is morphologically similar to the reaction observed in the sera of mice infected with S. japonicum. Sera from infected mice and humans were separated by G-200 chromatography to determine whether the unsegmented "RRI" was due to IgM antibody and the segmented COP reaction due to IgG. There was an elevation of the 19S fraction of sera of mice with 10 and 16 week infections. In addition, the murine 7S fraction was elevated in the 16 week infections. The COP activity was confined to the 7S fraction in the murine sera. Sera from Philippine patients which produced reactions of recent infection (acute sera), segmented COP reactions (chronic sera), and mixed reactions (believed to be from a transition stage between acute and chronic schistosomiasis) were tested. All human sera had elevation of both the 19S and 7S fractions of the acute serum. However, COP-reactive antibodies were confined to the 7S fraction of sera from the transition stage and acute stage infections. The results suggest that although IgM antibodies do in certain cases participate in the COP and produce reactions of recent infection, antibody class is not responsible for the different morphology of this reaction.

Efficacy of purified schistosoma japonicum egg antigens for ELISA serodiagnosis of human Schistosomiasis japonica: specificity and sensitivity.

At present, there is no consensus that purified schistosome egg antigens offer any advantage in the diagnosis of schistosomiasis by enzyme linked immunosorbent assay (ELISA). Previously, we demonstrated by multiple techniques that the major serologic antigens in Schistosoma japonicum soluble egg antigen (SEA) are glycoproteins, and that the glycoproteins with highest specificity and sensitivity are hydrophobes. We therefore tested these materials for their specificity, sensitivity and cost effectiveness in the ELISA. In this study we used five SEA fractions that varied in their purity and antigenicity. The order of immunologic specific activity in the ELISA, measured by titration of a standard sera pool, was: hydrophobic glycoproteins (highest), crude SEA glycoproteins, hydrophilic glycoproteins, crude SEA, and SEA proteins (lowest). Complexity (purity) of these materials were (in rank order), hydrophilic glycoproteins (purest), hydrophobic glycoproteins, crude glycoproteins, SEA proteins, and crude SEA (most complex). Epidemiologic sensitivity in the ELISA was tested on limited but well characterized populations. At high antigen coating concentration (0.5 microgram/well), the only antigen fraction with poor sensitivity was SEA proteins. There was little difference in epidemiologic sensitivity between the purer fractions with highest immunologic sensitivity (hydrophobic glycoproteins and crude SEA glycoproteins) and the crude SEA which possesses intermediate immunologic sensitivity. Differences in epidemiologic sensitivity were most pronounced when wells were coated at an antigen concentration (0.1 microgram/well) where crude SEA began to fail. Specificity for all preparations, assessed by reactivity with sera from patients with other trematode infections and with cestode and nematode infections, was excellent. The clinical sensitivity of the ELISA employing crude S. japonicum SEA is so high, and the specificity so good, that the increased immunologic sensitivity of partially purified antigens had little effect on epidemiologic sensitivity. This is not true for the S. mansoni ELISA where crude antigens had inferior sensitivity and specificity.

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.

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.

The emergence of Schistosoma japonicum cercariae from Oncomelania quadrasi.

The release of Schistosoma japonicum cercariae from Leytean Oncomelania quadrasi snails was observed under laboratory conditions. Two patterns of emergence were noted. The initial, nonperiodic emergence occurred immediately after submerging the snails in water and was followed by a periodic, diurnal emergence which peaked in the afternoon. The daily cercarial output of the periodic emergence appeared to be affected by exogenous light intensity. Furthermore, there was a cessation or reduction in cercarial output every 3rd or 4th day.

Agro-engineering and sanitation improvement in the control of schistosomiasis japonica in the Philippines: a review.

Measures that would change the habitat of the snails were found to prevent its breeding. Among these are clearing and drainage of waterlogged areas; filling of depressions where filling materials are available; ponding of areas which cannot be drained, and improved rice culture. The degree of success in snail control depends to a large extent on the amount of change brought about in the habitat. The more radical the change, the greater the reduction in snail density. It can be expected that improvement in sanitation in the form of toilet construction and use, provision of safe water supply, building of footbridges and the control of stray animals will bring a further decline in the transmission of the disease. Studies have shown that perfect sanitation in the form of toilet construction and use will reduce transmission by about 75%, the other 25% being contributed by lower mammals. Agro-engineering control measures are presently being carried out intensively in 7 town of Leyte, with food assistance from the UN/FAO World Food Program being given to volunteer workers as incentives for them to work. Snail evaluation after 2 years has shown a snail reduction by 72% in the areas covered. It may be mentioned here that sanitation improvement, especially latrine construction, is an ongoing program of the Department of Health in all rural areas.

Ambilhar in the treatment of Schistosoma japonicum infection and as an egg suppressant for mass treatment.

Ambilhar or niridazole at a dose of 25 mg per kg body weight for 7 days was found ineffective against Sl japonicum infection. Longer period of treatment for 10 to 14 days gave impressive stool negative conversion and egg reduction rates but with moderately severe reactions, the most alarming of which was hallucination. To minimize toxicity, the daily dose was reduced but given for a longer duration so that the total amount of the drug given per kilogram body weight was approximately the same as the 25 mg pre kg per day for 10 to 14 days. Of the two treatment schedules tried, the 15 mg per kg per day for 24 days was found relatively effective. Although the drug with this treatment regimen was well tolerated, a drop-out of 50.8% was observed. Ambilhar was therefore tried as an egg suppressant. With a 10-day treatment, all patients were again positive after 6 months. Egg reduction rates during the 6 months stool follow-up ranged from 69.8 to 93.5%. Further trials using this dose to be repeated every 3 to 6 months is contemplated.

Experimental infection of Oncomelania quadrasi with Paragonimus ohirai.

Two hundred Oncomelania quadrasi collected from Leyte, Philippines were exposed to infection with Paragonimus ohirai, a rodent type lung fluke. In a group, each snail was exposed individually to 10 miracidia hatched from eggs which were brought from Japan to the Philippines. In another group, 100 snails were placed in a Petri dish and P. ohirai miracidia were added to provide 10 per snail. The observations were made each successive week after exposure. All the snails examined were positive for the larvae of P. ohirai. Nine-ten weeks after exposure, many cercariae were recognized. It was proved that O. quadrasi is highly susceptible to P. ohirai.

Schistosomiasis japonica in Barrio San Antonio, Basey, Samar in the Philippines: II. Quantitative fecal examination and circumoval precipitin tests.

An improved quantitative stool examination technique (MFCT) and two variations in the performance of the circumoval precipitin test, one using whole serum (SCOPT) and the other employing the eluate from finger prick blood dried on filter paper (FPCOPT), were evaluated in a field study to detect infection with S. japonicum among residents of an endemic barrio in Samar. The sensitivity of SCOPT was above 90%, that of MFCT was between 80 to 90%, while that of FPCOPT was only about 50%. Intensity of infection as judged by fecal egg excretion and duration of infection as indicated by age were shown to be determinants of serum reactivity (and hence sensitivity of the two serodiagnostic tests). The relative insensitivity of FPCOPT observed in this work, also evident in some published data of previous workers, puts to doubt the wisdom of using this technique as the procedure of choice in epidemiologic surveys in the Philippines as currently favored in that country. Atypical positive reactions in circumoval precipitin tests using whole serum were detected which may make the differentiation of relatively recent from old infections possible.

Schistosomiasis japonica in Barrio San Antonia, Basey Samar, in the Philippines: III. The plasma circumoval precipitin test-procedure and use in epidemiologic studies.

A plasma circumoval precipitin test is proposed as the basic diagnostic tool for epidemiologic studies on schistosomiasis japonica in the Philippines. The collection of plasma, the preparation of the COP test slide, and the reading and interpretation of results are described in detail with pertinent comments. The cost, advantages and usefulness of the test are also discussed.

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.

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.