Endemic Area In Japan Research Articles

High Prevalence of HTLV-1 Carriers Among the Elderly Population in Kagoshima, a Highly Endemic Area in Japan.

Japan is one of the world's highly endemic areas for human T cell leukemia virus type 1 (HTLV-1), and it is known that the infection rate of HTLV-1 increases with age. The infection rate among the elderly has been estimated based on data from blood donors under the age of 65, and the actual number and rate of infection among the elderly are unknown. Data of 26,090 preoperative HTLV-1 screening tests conducted at Kagoshima University Hospital from 2001 to 2020, including 2726 HTLV-1-positive patients, were used for calculating the decadal infection rates for the year of birth. Estimated infection rates by birth year and demographic tables were used to estimate the current number of infected people in Kagoshima. The estimated total numbers of people infected with HTLV-1 in Kagoshima prefecture were 139,436 in 2005 and 80,975 in 2019. The infection rate increased with age for both men and women, reaching 17.3% for women born before the 1920s. Next, we tried to clarify whether the increase in infection rates with age was due to post-school age infections. The age of birth with the greatest increase in infection rate after 10 years was women born in the 1970s, and the increase in infection rate was only 0.98%, which is not a statistically significant increase. The number of infected people in Kagoshima was >80,000 in 2019. No data were available in this study to point to the involvement of horizontal transmission after school age in the high infection rate among the elderly. The high infection rate among the elderly is thought to have been high even when they were infants.

Extracellular vesicles from HTLV-1 infected cells modulate target cells and viral spread

BackgroundThe Human T-cell Lymphotropic Virus Type-1 (HTLV-1) is a blood-borne pathogen and etiological agent of Adult T-cell Leukemia/Lymphoma (ATLL) and HTLV-1 Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP). HTLV-1 has currently infected up to 10 million globally with highly endemic areas in Japan, Africa, the Caribbean and South America. We have previously shown that Extracellular Vesicles (EVs) enhance HTLV-1 transmission by promoting cell–cell contact.ResultsHere, we separated EVs into subpopulations using differential ultracentrifugation (DUC) at speeds of 2 k (2000×g), 10 k (10,000×g), and 100 k (100,000×g) from infected cell supernatants. Proteomic analysis revealed that EVs contain the highest viral/host protein abundance in the 2 k subpopulation (2 k > 10 k > 100 k). The 2 k and 10 k populations contained viral proteins (i.e., p19 and Tax), and autophagy proteins (i.e., LC3 and p62) suggesting presence of autophagosomes as well as core histones. Interestingly, the use of 2 k EVs in an angiogenesis assay (mesenchymal stem cells + endothelial cells) caused deterioration of vascular-like-tubules. Cells commonly associated with the neurovascular unit (i.e., astrocytes, neurons, and macrophages) in the blood–brain barrier (BBB) showed that HTLV-1 EVs may induce expression of cytokines involved in migration (i.e., IL-8; 100 k > 2 k > 10 k) from astrocytes and monocyte-derived macrophages (i.e., IL-8; 2 k > 10 k). Finally, we found that EVs were able to promote cell–cell contact and viral transmission in monocytic cell-derived dendritic cell. The EVs from both 2 k and 10 k increased HTLV-1 spread in a humanized mouse model, as evidenced by an increase in proviral DNA and RNA in the Blood, Lymph Node, and Spleen.ConclusionsAltogether, these data suggest that various EV subpopulations induce cytokine expression, tissue damage, and viral spread.

S907 DEVELOPMENT OF HUMANIZED MOUSE MODEL FOR STUDYING MOTHER TO CHILD HTLV‐1 TRANSMISSION AND PREVENTION WITH HTLV‐1 ANTIBODY TREATMENT

Background:Human T‐cell leukemia virus type 1 (HTLV‐1) infects mature T cells and causes adult T‐cell leukemia (ATL) and a chronic inflammatory central nervous system disease called HAM/TSP. HTLV‐1 transmissions mainly occurred in children via the breast milk of HTLV‐1+ carrier mothers. Thus, bottle‐feeding or avoiding long term breastfeeding are recommended in the endemic areas of Japan and this resulted in a drastic decrease in new HTLV‐1 infections. Previous studies have shown that approximately 3% of children born from HTLV‐1+ carrier mothers were still infected even when they were exclusively bottle‐fed. This suggested the possible involvement of alternative HTLV‐1 transmission routes, such as placental or birth canal transmission.Aims:Here, we attempted to develop new humanized mouse model of HTLV‐1 mother to child (MTC) transmission for evaluating HTLV‐1 antibody to prevent HTLV‐1 MTC infection.Methods:NOD/SCID/gammac (null) (NOG) pregnant mice were intraperitoneally injected with human PBMCs before being transplanted with a mitomycin C‐treated HTLV‐1‐infected cell line (MT‐2). To evaluate the importance of HTLV‐1 infections via breastfeeding or before birth, we designed a study that switched HTLV‐1‐infected carrier mother (CM) mice with non‐infected healthy mother (HM) mice. HTLV‐1 infection was determined by the real‐time PCR quantification of HTLV‐1 DNA isolated from mouse liver, peripheral blood and breastmilk.Results:Although no HTLV‐1‐infected T cells were detected in the peripheral blood of newborn mice at day 14, HTLV‐1‐infected cells were exclusively observed in the liver tissues via FACS and PCR. Furthermore, highly enriched HTLV‐1+ cells were still detected in mouse breast milk 26 days after birth by PCR. These data suggest that there might be an enrichment system of HTLV‐1 infectious cells in mouse breast tissue. We next performed the mother‐pup pair switching study. After switching, CM mice were maintained with HM mice pups (potentially HTLV‐1−), and HM mice were maintained with CM mice pups (potentially HTLV‐1+). This switching at birth resulted in 28% of the potentially HTLV‐1− pups to become HTLV‐1+, since they were breastfed by an HTLV‐1+ mother. Similarly, 42% of the potentially HTLV‐1+ pups were HTLV‐1+ at 40 days after switching, as they were breastfed by an HTLV‐1− mother. These results suggested that both breastfeeding and canal or placental transmissions presented equal risks with respect to HTLV‐1 infections. We finally analyzed the HTLV‐1 infectious status both in mouse embryo and placenta at E17.5 and found HTLV‐1+ cells both in fetal liver (25%) and placenta (37%).Summary/Conclusion:Together, these data suggest that during pregnancy, HTLV‐1 cells invade the fetal tissues and might be a potential resource of HTLV‐1 infection. We are now trying to assess the effect of HTLV‐1 antibody for preventing MTC HTLV‐1 infection.

Subclinical Infection of Babesia gibsoni in Dogs in an Endemic Area in Japan

Subclinical Infection of <i>Babesia gibsoni</i> in Dogs in an Endemic Area in Japan

Investigation of antibody to severe fever with thrombocytopenia syndrome virus (SFTSV) in blood samples donated in a SFTS-endemic area in Japan.

The risk of transfusion-transmitted infection (TTI) for severe fever with thrombocytopenia syndrome virus (SFTSV) is a concern because person-to-person transmission resulting from contact with SFTSV-contaminated blood has been reported. To obtain information regarding the risk of TTI-SFTSV, antibody testing was performed for blood samples donated in an severe fever with thrombocytopenia syndrome-endemic area in Japan. No antibody-positive samples were detected among 3990 samples. This finding suggested that there were few cases of SFTSV infection among donors and that the risk of TTI-SFTSV was also estimated low in Japan.

Low Seroprevalence of Severe Fever with Thrombocytopenia Syndrome Virus Antibodies in Individuals Living in an Endemic Area in Japan.

Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne infection with a high mortality rate. It is caused by the SFTS virus (SFTSV) and is endemic in some areas in western Japan, including the Kagoshima prefecture. In the present study, healthy individuals living in this prefecture were examined to assess for anti-SFTSV seroprevalence. An initial study was performed using the serum samples collected from a total of 646 individuals living in Kagoshima. At the same time, a questionnaire was used to collect information (such as occupation and a history of tick bite). Enzyme-linked immunosorbent assay and indirect immunofluorescence assay were used for the screening. Finally, the seroprevalence of anti-SFTSV antibodies was confirmed using a neutralization assay. Only 2 (0.3%) out of 646 study participants were positive for anti-SFTSV antibodies. No significant difference was observed between individuals who are at a high or low risk of tick bite in terms of seropositivity. Next, a total of 1,000 serum samples collected from general blood donors by the Japanese Red Cross Kyushu Block Blood Center were tested. None of these samples tested positive for anti-SFTSV antibodies. These results suggest a low seroprevalence of anti-SFTSV antibodies in healthy individuals living in an endemic area in Japan.

Clinical characteristics of laboratory-confirmed leptospirosis in Okinawa, Japan, 1974-2015: high incidence of Jarisch-Herxheimer reaction.

Leptospirosis is a zoonotic disease known to have wide-ranging clinical manifestations. Despite a number of published case series, culture-confirmed series are few and there is a paucity of data on Jarisch-Herxheimer reaction (JHR) associated with treatment of leptospirosis. Our objective was to describe the clinical and epidemiological factors associated with leptospirosis in an endemic area of Japan, with a focus on the occurrence of JHR, an often unrecognized and likely underestimated phenomenon. We performed a retrospective observational study of laboratory-confirmed leptospirosis at a single center over a 40-year period. We report 100 leptospirosis cases in 99 patients during the period 1974-2015. Seventy-four cases were diagnosed by culture, representing eight different serovars. JHR was seen in 23 (82%) of 28 cases, including 19 (90%) of 21 cases treated with bactericidal antibiotics compared to 4 (57%) of seven cases with bacteriostatic antibiotics (p=0.08). We found a wide variety of clinical manifestations, epidemiological exposures, and causative serovars of disease in an endemic region of Japan. We also found that JHR occurs frequently, and its recognition may be important for the diagnosis and management of leptospirosis in the early stage when laboratory confirmation is pending.

The world first two cases of severe fever with thrombocytopenia syndrome: An epidemiological study in Nagasaki, Japan

Severe fever with thrombocytopenia syndrome (SFTS) caused by the SFTS virus (SFTSV), a novel phlebovirus belonging to the family Bunyaviridae, was reported in China for the first time in 2009. We observed two cases where the SFTSV was isolated for the first time in Nagasaki, Japan, in 2005. Two males in their 60s, a farmer and a hunter, respectively, living in Nagasaki developed SFTS during the same period. The patients developed similar clinical symptoms and signs, such as fever, loss of consciousness, and multiple organ dysfunction. The farmer died and the hunter survived. A retrospective diagnosis of SFTS was made in 2013, and genetic analysis revealed that the patients were infected with different SFTSV strains. Retrospective analysis of cytokine production in non-fatal case revealed interleukin (IL)-6, IL-8 and interferon-γ level of acute phase was low and could be potential prognostic factors. As there are no epidemiological studies of positive rate of SFTSV antibody in people living in endemic areas in Japan, a field study was performed. Volunteers at high risk for tick bites, such as hunters, farmers, and soldiers, were recruited in 6 regions, including the areas where the SFTS cases occurred. Three hundred and twenty six volunteers in Nagasaki prefecture were examined and none of these tested positive for the SFTSV antibody. Our data indicates that the risk for SFTSV infection is not high in Nagasaki prefecture. Further collection of blood samples from endemic areas is warranted for the prevention of SFTSV infection.

Clinical Manifestations of Japanese Spotted Fever: Multi-institution Study in Endemic Areas in Japan

Clinical Manifestations of Japanese Spotted Fever: Multi-institution Study in Endemic Areas in Japan

Increase in incidence of adult T‐cell leukemia/lymphoma in non‐endemic areas of Japan and the United States

Adult T-cell leukemia/lymphoma (ATLL) is a peripheral T cell neoplasm that is associated with infection by the human T-cell leukemia virus type I (HTLV-1). Although the high incidence of ATLL in HTLV-1-endemic areas is well known, population-based evidence concerning the incidence of ATLL in non-endemic areas is scarce. To answer this, we estimated the age-standardized incidence of ATLL from 1993 to 2006 for Japan and 1993 to 2008 for the US and assessed its trend using data from a population-based cancer registry in Japan and Surveillance Epidemiology and End Results (SEER) in the US. The Japanese data were collected from 15 prefectures. A total of 2055 patients in the three prefectures in Kyushu and 1380 patients in the 12 prefectures in Honshu were diagnosed with ATLL in the study period. In the US, a total of 140 patients were diagnosed with ATLL. The results showed that the age-standardized incidence in non-endemic areas in Japan and in the US significantly increased during this period (annual percent change [95%CI]; Japan-Honshu: +4.6% [1.1, 8.2]; US: +6.2% [1.5, 11.1]), while in the endemic areas of Japan there was no change (annual percent change [95%CI]; Japan-Kyushu: 0.0% [-1.6, 1.7]). This result indicates that the disease has been spread by carriers to non-endemic areas, and suggests the necessity of establishing a standard preventive strategy.

HTLV-1 uveitis

Human T cell lymphotropic virus type 1 (HTLV-1) is the first retrovirus described as a causative agent of human disease. Following adult T cell leukemia/lymphoma and HLTV-1-associated myelopathy/tropical spastic paraparesis, HTLV-1 uveitis (HU) has been established as a distinct clinical entity caused by HTLV-1 based on seroepidemiological, clinical, and virological studies. HU is one of the most common causes of uveitis in endemic areas of Japan and can be a problematic clinical entity all over the world. HU occurs with a sudden onset of floaters and foggy vision, and is classified as an intermediate uveitis. Analysis of infiltrating cells in eyes with HU revealed that the majority of infiltrating cells were CD3+ T cells, but not malignant cells or leukemic cells based on their T cell receptor usage. HTLV-1 proviral DNA, HTLV-1 protein, and viral particles were detected from infiltrating cells in eyes with HU. HTLV-1-infected CD4+ T cell clones established from infiltrating cells in eyes with HU produced large amounts of various inflammatory cytokines, such as IL-1, IL-6, IL-8, TNF-α, and interferon-γ. Taken together, HU is considered to be caused by inflammatory cytokines produced by HTLV-1-infected CD4+ T cells that significantly accumulate in eyes; therefore, topical and/or oral corticosteroid treatment is effective to treat intraocular inflammation in patients with HU. Further investigation is needed to establish a specific treatment for HU.

Molecular Determinants of Human T-lymphotropic Virus Type 1 Transmission and Spread

Human T-lymphotrophic virus type-1 (HTLV-1) infects approximately 15 to 20 million people worldwide, with endemic areas in Japan, the Caribbean, and Africa. The virus is spread through contact with bodily fluids containing infected cells, most often from mother to child through breast milk or via blood transfusion. After prolonged latency periods, approximately 3 to 5% of HTLV-1 infected individuals will develop either adult T-cell leukemia/lymphoma (ATL), or other lymphocyte-mediated disorders such as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The genome of this complex retrovirus contains typical gag, pol, and env genes, but also unique nonstructural proteins encoded from the pX region. These nonstructural genes encode the Tax and Rex regulatory proteins, as well as novel proteins essential for viral spread in vivo such as, p30, p12, p13 and the antisense encoded HBZ. While progress has been made in the understanding of viral determinants of cell transformation and host immune responses, host and viral determinants of HTLV-1 transmission and spread during the early phases of infection are unclear. Improvements in the molecular tools to test these viral determinants in cellular and animal models have provided new insights into the early events of HTLV-1 infection. This review will focus on studies that test HTLV-1 determinants in context to full length infectious clones of the virus providing insights into the mechanisms of transmission and spread of HTLV-1.

Filariasis control with diethylcarbamazine in three major endemic areas in Japan.

Filariasis control with diethylcarbamazine in three major endemic areas in Japan.

Electrophysiological features of familial amyloid polyneuropathy in endemic area

The process of deterioration of peripheral nerve function in familial amyloid polyneuropathy (FAP) with amyloidogenic transthyretin (ATTR) Val30Met has not been systematically evaluated hitherto. We performed nerve conduction studies in 69 patients with FAP with ATTR Val30Met from one of the endemic areas in Japan. Sensory conduction velocity (SCV), motor conduction velocity (MCV), the size of the compound muscle action potential (CMAP) and distal latency (DL) were measured in the ulnar and tibial nerves. SCV was evaluated using the orthodromic method with needle recording electrodes. These electrophysiological parameters were compared with clinical stage of FAP and duration of neuropathy. When subjects noted minimal neuropathic symptoms only in the feet, motor and sensory nerve function in both the hands and feet had already been disturbed. Sensory nerve action potential on the foot disappeared more rapidly than CMAP. CMAP on foot muscle rapidly decreased during the initial 2 years and completely disappeared within 10 years. The duration of illness and deterioration parameters (CMAP of the abductor digiti minimi muscle, MCV and SCV of the ulnar nerve and DL of both ulnar and tibial nerves) were linearly correlated. CMAP was the most sensitive and reliable parameter to evaluate motor nerve degeneration in FAP.

Trends in Human T-Cell Leukemia Virus Type-1 (HTLV-1) Prevalence and the Incidence of Adult T-Cell Leukemia/Lymphoma (ATL) in Nagasaki, Japan: A Hospital-Based and Population-Based Study.

Abstract 1920Poster Board I-943 Introduction:The prevalence of HTLV-1 is mostly evaluated by the age-specific seroprevalence in blood donors, and the results have been conventionally used to estimate the age-specific incidence of ATL in Japan. However, the results may be underestimated due to an age limit (16-69 yr) for donation, a healthy donor effect, and a birth cohort effect. Data concerning the birth-year specific incidence of ATL among HTLV-1 carriers other than blood donors are scarce. Methods:The study evaluated data of the anti-HTLV-1 antibody testing of 10,261 patients (males: 5,523, females: 4,737) who visited the Nagasaki University Hospital during 2000-2007 and data of 360 ATL cases (males: 188, females: 172) who were diagnosed in Nagasaki City (an endemic area in Japan) in a population-based Nagasaki Prefectural Cancer Registry (NPCR). To estimate birth-year specific incidence rates of ATL in population-based HTLV-1 carriers, we used the 2006 census population for Nagasaki City by applying the hospital-based seroprevalence data. Results:Of 10,261 patients, 1,392 (males: 653, females: 739) were HTLV-1 antibody positive. The overall HTLV-1 seroprevalence was 13.57% (95%CI: 12.90-14.23%). The seroprevalence was significantly higher in females than in males (15.60% vs. 11.82%, P<0.0001). The birth-year specific seroprevalence was 18.69% (before 1926), 17.83% (1927-1936), 15.91% (1937-1946), 13.80% (1947-1956), 9.19% (1957-1966), 4.07% (1967-1976), 2.07% (1977-1986), and 0% (after 1987) (a significantly declining trend: P <0.0001). The estimated annual number of HTLV-1 carriers by birth-year in Nagasaki city was 5257, 8093, 8151, 8083, 4434, 2180, 785, and 0, respectively. Finally, we estimated the annual incidence rate of ATLL per 100,000 HTLV-1 carriers by birth-year; 171 (before 1926), 86 (1927-1936), 41 (1937-1946), 32 (1947-1956), 11 (1957-1966), and 0 (after 1967). The crude lifetime risk of developing ATLL in HTLV-1 carriers was estimated to be 7.29% for males and 3.78% for females. Conclusions:The birth-year specific HTLV-1 seroprevalnces in the present study were approximately 50% higher than those previously reported in blood donors1 (for example: 6.22% in those born before 1950). Although it is possible that our results are over-estimated2, the present study suggests that there is still a large pool of elderly HTLV-1 carriers in this endemic area. Further studies are needed to investigate the mechanism of the development of ATL among HTLV-1 carriers for preventing the development. Reference: 1) Iwanaga M et al. Int J Hematol, 2009. 2) Arisawa K et al. Int J Cancer, 2000. Disclosures:No relevant conflicts of interest to declare.

Epidemiology, clinical features and prevention of HTLV‐I infection

Human T-cell leukemia virus type I (HTLV-I) [1,2] is the main cause of Adult T-cell leukemia ⁄ lymphoma (ATLL) [3] and HTLV-I associated myelopathy ⁄ Tropical spastic paraparesis (HAM ⁄ TSP) [4,5]. From the long-term epidemiological observation, the HTLV-I carriers are clustered in limited groups in the world, i.e., Southwestern Japanese, native Oceanians, Amerindians in Andes and Northeast British Colombia, North Iranians as well as Central Africans and their descendants in the Caribbean basin and South America [6]. According to evidence obtained from a biennial nationwide surveillance of adult T-cell leukemia ⁄ lymphoma (ATLL) carried out in Japan since 1986, the annual incidence is estimated to be 700 within approximately one million HTLV-I carriers in Japan [7]. The affected individuals mainly inhabit the southern and northern ATLL endemic areas. Among 3499 ATLL patients newly diagnosed during the last ten years from 1988 to 1997 [8], approximately 70% were born in the southwestern districts of Kyushu and Shikoku, and 10% in the northern districts of Hokkaido and Tohoku (Fig. 1). This epidemic pattern of ATLL is still continuous up until now. The main reasons of unique geographical clustering of ATLL in Japan might be linked to a history of old Japanese migration with unique geographical clustering of HTLV-I carriers in Japanese archipelago due to the natural transmission routes of mother-to-child through breast milk and man-to-woman through semen [9,10]. In the ATLL endemic areas in Japan a systematic prevention trial against HTLV-I transmission through breast milk from HTLV-I carrying mothers to newborn babies, e.g., strong recommendation to pregnant women with HTLV-I to completely stop breast milk and ⁄ or to raise their babies by short-term breast feeding [11,12]. Clinically contrasting HTLV-I related diseases

Trends in the seroprevalence of HTLV-1 in Japanese blood donors in Nagasaki Prefecture, 2000–2006

Human T cell leukemia virus type-1 (HTLV-1) is the established cause of adult T cell leukemia/lymphoma. Monitoring time trends in HTLV-1 seroprevalence in blood donors is important to assess the safety of the blood supply in the viral endemic area. We analyzed changes in HTLV-1 seroprevalence in 48415 first-time blood donors who donated blood from 2000 to 2006 in Nagasaki prefecture, an endemic area in Japan. The donors were divided into 10-year birth cohorts: before 1950, 1951-1960, 1961-1970, 1971-1980, and 1981-1990. Among the first-time blood donors, 622 were tested positive for HTLV-1 [overall seroprevalence: 1.28%, (95% CI 1.19-1.39)]. Seroprevalence was significantly high in the birth cohort of before 1950 (6.22%) and declined with birth-year. The time trend of the birth-cohort-specific seroprevalence showed almost no change within each birth cohort, except for the birth cohort of 1981-1990 that showed a significantly declining trend (P for trend = 0.006). Among the birth cohort of 1981-1990, the seroprevalence was stable among those born during 1981-1986 (0.66-0.83%), but was lower among those born during 1987-1990 (0-0.38%). Detail analyses showed that HTLV-1 seroprevalence among blood donors clearly declined in those born after 1987.

Human T‐lymphotropic virus type 1 (HTLV‐1) genetic typing in Kakeroma Island, an island at the crossroads of the ryukyuans and Wajin in Japan, providing further insights into the origin of the virus in Japan

Peripheral blood samples were collected from 23 human T-lymphotropic virus type-1 (HTLV-1) carriers residing in Kakeroma Island, Japan (Kagoshima Prefecture, Oshima County, Setouchi Town), one of the most highly endemic areas in Japan. The samples were subjected to amplification by PCR and sequencing of the Long Terminal Repeat in order to reconstruct a phylogenetic tree of HTLV-1 isolates. Restriction Fragment Length Polymorphism (RFLP) analysis of env region was also conducted for subgrouping of HTLV-1. Although one sample could not be amplified by PCR, and three more could not be sequenced due to the existence of conspicuous nonspecific bands or repeated sequences, the phylogenetic analysis revealed that the remaining 19 isolates obtained from Kakeroma Island belonged to either the Transcontinental or the Japanese subgroups of the Cosmopolitan subtype, one of the three major subtypes. The RFLP data corresponded closely with the typing data throughout the sequencing. The proportion of the Transcontinental subgroup among the isolates was 26.3% (5 of 19) by sequence analysis and 27.3% (6 of 22) by RFLP. Unlike in Taiwan, China and Okinawa, the Japanese subgroup was dominant in Kakeroma Island. The analysis would also suggest that the Japanese subgroup seems not to have derived from the Transcontinental subgroup, but rather that the Transcontinental subgroup came to Japan first and was followed later by the Japanese one.

Trends of incidence rate of adult T‐cell leukemia/lymphoma in an HTLV‐1 endemic area in Japan

Trends of incidence rate of adult T‐cell leukemia/lymphoma in an HTLV‐1 endemic area in Japan

Spatial Analysis and Remote Sensing for Monitoring Systems of &lt;i&gt;Oncomelania nosophora&lt;/i&gt; Following the Eradication of Schistosomiasis Japonica in Yamanashi Prefecture, Japan

In order to develop an inexpensive, simple, and accurate method of monitoring for the reemergence of schistosomiasis japonica in Yamanashi Prefecture, Japan, the distribution and habitation density of the intermediate host, Oncomelania nosophora, were spatially analyzed using geographic information systems. The 1967-1968 density distribution maps prepared by Yamanashi Prefecture and Nihei were digitized and geocoded. The habitats and population density of O. nosophora were estimated by referring to the data compiled by the Yamanashi Association for Schistosomiasis Control (1977). These earlier findings were compared with average population densities between 1996 and 2000 previously recorded (Nihei, N., Kajihara, N., Kirinoki, M., et al., Parasitol. Int., 52, 395-401, 2003 and Nihei, N., Kajihara, N., Kirinoki, M., et al., Parasitol. Int., 53, 199-205, 2004). A variance map was created to compare the spatial distribution maps of population density from each of the two periods of interest. The changes in distribution were remarkable and the map was found to be effective for future control. The most appropriate monitoring sites were chosen on the basis of the spatial population density maps and the variance map. Moreover, the paddy fields at risk were extracted using the normalized difference vegetation index value based on Advanced Land Observation Satellite images. The combination of this method with the global positioning system provides an inexpensive means of monitoring modern schistosomiasis endemic areas in Japan and also in China, the Philippines, and other countries as well, where the intermediate snail grows in paddy fields and marshlands under consistently wet conditions.