Analysis of Suspected Measles Cases with Discrepant Measles-Specific IgM and rRT-PCR Test Results, Japan.

We investigated clinically suspected measles cases that had discrepant real-time reverse transcription PCR (rRT-PCR) and measles-specific IgM test results to determine diagnoses. We performed rRT-PCR and measles-specific IgM testing on samples from 541 suspected measles cases. Of the 24 IgM-positive and rRT-PCR--negative cases, 20 were among children who received a measles-containing vaccine within the previous 6 months; most had low IgG relative avidity indexes (RAIs). The other 4 cases were among adults who had an unknown previous measles history, unknown vaccination status, and high RAIs. We detected viral nucleic acid for viruses other than measles in 15 (62.5%) of the 24 cases with discrepant rRT-PCR and IgM test results. Measles vaccination, measles history, and contact history should be considered in suspected measles cases with discrepant rRT-PCR and IgM test results. If in doubt, measles IgG avidity and PCR testing for other febrile exanthematous viruses can help confirm or refute the diagnosis.

Isolation and whole-genome sequencing analysis of Escherichia fergusonii harboring a heat-labile enterotoxin gene from retail chicken meat in Okinawa, Japan.

This study aimed to reveal the prevalence of heat-labile enterotoxin (LT) gene-positive Escherichia fergusonii in retail chicken meat and genetically characterize these strains. E. fergusonii harboring LT gene was isolated from 6 out of 60 (10%) retail chicken samples in Okinawa, Japan. Whole-genome sequencing analysis revealed that LT gene-positive E. fergusonii from chicken meat and feces contain an IncFII plasmid harboring elt1AB, and suggested to spread clonally to retail chicken through fecal contamination. Additionally, it was found that these strains harbor multidrug-resistant genes on their plasmids. Their pathogenicity and continuous monitoring are required for confirmation.

The Spread of Heat-Labile Enterotoxin-Harboring Escherichia fergusonii in Broiler Chickens and Pigs in Okinawa, Japan.

In 2012, Escherichia fergusonii harboring a heat-labile enterotoxin (LT) was isolated from healthy chickens in South Korea. However, little is known regarding the prevalence, spread, and pathogenicity of these strains in humans and animals. This study aimed to understand the public health threats, such as the distribution, antimicrobial resistance, and genetic diversity of E. fergusonii carrying LTs. E. fergusonii containing LT was isolated from 15.0% (52/346) of chicken fecal samples from all three tested chicken farms but not from 360 pig fecal samples. The antimicrobial susceptibility testing revealed that over 75% of strains were resistant to ampicillin, kanamycin, nalidixic acid, streptomycin, or tetracycline; additionally, 71.2% (37/52) of strains were resistant to all five of these antimicrobials. The 52 strains were clustered into eight pulsed-field gel electrophoresis (PFGE) types, with types V and type VI accounting for 84.6% (44/52). In the present study, multiple chicken farms harbored E. fergusonii with similar antimicrobial resistance patterns and genetic clonality. Since the pathogenicity of LT-bearing E. fergusonii in humans and animals, such as food poisoning and sporadic diarrhea via meat, the transmission of the strains, and the dissemination of antimicrobial resistance genes are unknown, additional research is required.

Antimicrobial resistance and molecular epidemiological analysis of Escherichia fergusonii harboring the mcr gene in pigs and broiler chickens in Okinawa, Japan.

The dissemination of mcr-harboring Enterobacteriaceae, e.g., Escherichia fergusonii, with resistance to colistin via animal products is a public health concern. In our previous study, E. fergusonii harboring the mcr gene were isolated from 11 pigs and 43 chickens. To understand the spread of mcr-harboring E. fergusonii in Okinawa, Japan, and to gain further insights into how they can be controlled, an antimicrobial susceptibility testing, pulsed-field gel electrophoresis (PFGE), a conjugation test for the transferability of mcr-harboring plasmids, and PCR-based replicon typing (PBRT) were performed using the 54 strains. According to the disk-diffusion and broth microdilution methods, 9 of the 11 strains from pigs and 9 of the 43 strains from chickens had multidrug resistance (MDR). The broth microdilution method showed that all strains were resistant to colistin, and the minimum inhibitory concentration of colistin was 4-16 µg/mL. PFGE suggested identical PFGE types were being transmitted within one pig farm, within one chicken farm, and among several chicken farms. These findings showed that some mcr-harboring E. fergusonii in Okinawa exhibited MDR, and these had spread within farms and between farms. In the mcr gene conjugation test and PBRT, a type IncI2 plasmid replicon was detected in all mcr-1-harboring transconjugants. Therefore, evidence suggests that the IncI2 plasmid is probably involved in the transmission of the mcr-1 gene. It is important to monitor the antimicrobial resistance profile and dissemination of the IncI2 plasmid in mcr-harboring E. fergusonii.

Leptospirosis with multiple organ dysfunction in a mongoose-scat-detection dog infected with Leptospira interrogans serogroup Hebdomadis, Okinawa, Japan.

A 2-year-old male mongoose-scat-detection dog was diagnosed with leptospirosis by urine PCR. The patient developed acute renal failure, hepatic dysfunction, and disseminated intravascular coagulation. Treatment with antibiotics was administered, including ampicillin and doxycycline, and supportive care management was provided. Seroconversion against serogroup Hebdomadis was observed on day 8. The leptospiral gene flaB was detected only in urine collected on day 1, from which Leptospira interrogans ST329 was identified by multilocus sequence typing using seven housekeeping genes. L. interrogans serogroup Hebdomadis ST329 has been isolated from mongooses and humans in Okinawa, Japan. This patient received early treatment with antibiotics, which may have contributed to the early recovery of renal function and removal of L. interrogans from kidney tissue.

Severe Fever with Thrombocytopenia Syndrome Virus RNA in Ticks from Wild Mongooses in Okinawa Prefecture, Japan.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging zoonotic tick-borne disease caused by SFTS virus (SFTSV). SFTSV has a wide spectrum of animal hosts and is considered to circulate in an enzootic tick-vertebrate-tick cycle. A previous seroepidemiological study showed the presence of anti-SFTSV antibodies in wild mongooses (Herpestes auropunctatus) and indicated that outdoor activity was associated with an increased risk of tick bites among Okinawa residents. However, the association of SFTSV with wild mongooses and ticks remains unclear. To understand the association between ticks and mongooses with respect to the SFTSV enzootic cycle, we investigated the presence of SFTSV RNA in ticks collected from wild mongooses on the Okinawa Island. A total of 638 ticks belonging to 2 genera and 3 species (Haemaphysalis hystricis, Haemaphysalis formosensis, and Ixodes granulatus) were collected from 22 wild mongooses from 2016 to 2021. SFTSV RNA was detected in two pools of H. hystricis larvae collected from a wild mongoose in the central area of the main island of Okinawa in 2017. Although the prevalence of SFTSV in ticks from wild mongooses is low, endemic circulation of the virus in Okinawa should be carefully monitored to prevent future infections.

Laboratory diagnostic, epidemiological, and clinical characteristics of human leptospirosis in Okinawa Prefecture, Japan, 2003-2020.

BACKGROUND: Leptospirosis is considered an endemic disease among agricultural workers in Okinawa Prefecture, which is the southernmost part of Japan and has a subtropical climate, but data on the current status and trend of this disease are scarce. METHODOLOGY/PRINCIPAL FINDINGS: We conducted a retrospective study of clinically suspected leptospirosis patients whose sample and information were sent to the Okinawa Prefectural Institute of Health and Environment from November 2003 to December 2020. Laboratory diagnosis was established using culture, nested polymerase chain reaction (PCR), and/or microscopic agglutination test (MAT) with blood, cerebrospinal fluid, and/or urine samples. Statistical analyses were performed to compare the epidemiological information, clinical features, and sensitivities of diagnostic methods among laboratory-confirmed cases. Serogroups and the species of Leptospira isolates were determined by MAT using 13 antisera and flaB sequencing. A total of 531 clinically suspected patients were recruited, among whom 246 (46.3%) were laboratory confirmed to have leptospirosis. Among the confirmed cases, patients aged 20-29 years (22.4%) and male patients (85.7%) were the most common. The most common estimated sources of infection were recreation (44.5%) and labor (27.8%) in rivers. Approximately half of the isolates were of the L. interrogans serogroup Hebdomadis. The main clinical symptoms were fever (97.1%), myalgia (56.3%), and conjunctival hyperemia (52.2%). Headache occurred significantly more often in patients with Hebdomadis serogroup infections than those with other serogroup infections. The sensitivities of culture and PCR exceeded 65% during the first 6 days, while the sensitivity of MAT surpassed that of culture and PCR in the second week after onset. PCR using blood samples was a preferable method for the early diagnosis of leptospirosis. CONCLUSIONS/SIGNIFICANCE: The results of this study will support clinicians in the diagnosis and treatment of undifferentiated febrile patients in Okinawa Prefecture as well as patients returning from Okinawa Prefecture.

Seroepidemiological study of severe fever with thrombocytopenia syndrome in animals and humans in Okinawa, Japan.

In Okinawa prefecture, Japan, the first case of severe fever with thrombocytopenia syndrome (SFTS) was confirmed in August 2016, and this case remains to be the only reported case of SFTS in Okinawa. The epidemiological investigation indicated that the patient had been infected on the main island of Okinawa, but source and route of infection were unknown. Therefore, to understand the possible source and route of SFTS virus (SFTSV) infection in Okinawa, we performed a seroepidemiological study of SFTSV among animals and dwellers in Okinawa and conducted a questionnaire survey to investigate risk factors for tick bites in Okinawa. Among the 1,035 serum samples from four different animal species, anti-SFTSV antibodies were detected in only 4.2% wild mongoose (Herpestes auropunctatus) serum samples. To our knowledge, this is the first study to report the detection of anti-SFTSV antibodies in wild mongooses. Meanwhile, all 1,104 human inhabitants tested negative for anti-SFTSV antibodies, suggesting that the frequency of SFTSV exposure is low in Okinawa. Logistic regression analysis of the questionnaire results showed that outdoor activity was associated with an increased risk of tick bite among Okinawa residents. Despite the current low frequency of SFTSV infection in animals and humans, endemic circulation of the virus in Okinawa should be carefully monitored in the area for preventing future infections.

Toxoplasma gondii antibody prevalence and isolation in free-ranging cats in Okinawa, Japan.

Cats are an important host of Toxoplasma gondii from an epidemiological perspective because they are the only definitive hosts that excrete oocysts in their feces. In this study, 201 free-ranging cats in Okinawa were examined for T. gondii infection. Using the latex agglutination test, we detected antibodies against T. gondii in 26.9% (54/201) of the cats. Oocysts of T. gondii were not detected upon microscopic examination of the feces of 128 cats. T. gondii was isolated from the tissues of 9 out of 24 seropositive or pseudo-seropositive cats with a bioassay using laboratory mice. Genotyping for the GRA6 gene revealed that five and four of the isolates were type I and II, respectively.

Characteristics of Household Transmission of COVID-19 during Its Outbreak in Okinawa, Japan from February to May 2020.

The Okinawa prefecture confirmed 142 cases of coronavirus disease from February 14 to May 2020. Among them, 78 were the first cases of a household with 174 household contacts. Of the 174 contacts, 21 contracted the disease, indicating a secondary attack rate of 12.1% (95% confidence interval [CI] 7.6-17.9%). No significant differences were observed in the demographics and quantitative reverse transcription-polymerase chain reaction test results between the first cases that became the sources of infection to the household members. The secondary attack rates with respect to the various characteristics of the household members were significantly different: aged >69 years (40.9% [95% CI 20.7-63.6%]) and those with underlying diseases (36.0% [95% CI 18.0-57.5%]). When the period from the onset to isolation of the first household case was within 3 days, the secondary attack rate was low (4.5% [95% CI 0.1-22.8%]). Among the 21 secondary cases, 11 (52.4%) developed within 5 days of symptom onset in the first case within the same household. This indicates that secondary infection within the household occurred immediately after symptom onset in the first case. Therefore, isolation of a suspected patient can help reduce secondary household infections.

Molecular and serological epidemiology of Leptospira infection in cats in Okinawa Island, Japan.

Leptospirosis is a zoonosis caused by pathogenic Leptospira spp. Cats have been reported to be infected with Leptospira spp. and shed the bacteria in the urine. However, the importance of cats as an infection source for humans remains unclear. In this study, Leptospira infection in cats in Okinawa Prefecture, Japan, where leptospirosis is endemic, was investigated by leptospiral antibody and DNA detection using microscopic agglutination test and nested PCR, respectively. Moreover, multilocus sequence typing (MLST) and whole genome sequencing (WGS) were conducted on the Leptospira borgpetersenii serogroup Javanica isolated from cats, black rats, a mongoose, and humans. Anti-Leptospira antibodies were detected in 16.6% (40/241) of the cats tested, and the predominant reactive serogroup was Javanica. The leptospiral flaB gene was detected in 7.1% (3/42) of cat urine samples, and their sequences were identical and identified as L. borgpetersenii. MLST and WGS revealed the genetic relatedness of L. borgpetersenii serogroup Javanica isolates. This study indicated that most seropositive cats had antibodies against the serogroup Javanica and that cats excreted L. borgpetersenii in the urine after infection. Further, genetic relatedness between cat and human isolates suggests that cats may be a maintenance host for L. borgpetersenii serogroup Javanica and a source for human infection.

Novel genotypes of Leptospira interrogans serogroup Sejroe isolated from human patients in Okinawa Prefecture, Japan.

Leptospirosis is a zoonotic disease caused by pathogenic spirochetes of Leptospira species. It is a public health issue in the tropics, including Okinawa, the southernmost prefecture of Japan. This study reports the first isolation of L. interrogans serogroup Sejroe from two human patients in Japan, and describes its molecular characterization using multilocus sequence typing (MLST) and multiple-locus variable-number tandem repeat analysis (MLVA). MLST on the two isolates, 168036 and 178129, showed that pfkB in 178129 is a novel allele, and that both isolates constitute novel sequence types (STs); ST286 for 168036 and ST287 for 178129. A minimum spanning tree based on seven alleles of L. interrogans indicates that both isolates are genetically close, but are distinct from known L. interrogans serogroup Sejroe strains. MLVA using 11 loci demonstrated that seven of the 11 loci were identical between the two isolates, whereas the identity between the isolates and the seven reference strains of L. interrogans serogroup Sejroe was zero to three loci. These results indicate that the isolates investigated in this study have novel genotypes, and are genetically closest to each other among the known L. interrogans serogroup Sejroe strains.

Molecular and biological analysis revealed genetic diversity and high virulence strain of Toxoplasma gondii in Japan.

Toxoplasma gondii is classified into 16 haplogroups based on a worldwide genotyping study of the parasite. However, only a few isolates from Japan were included in this analysis. To conduct more precise genotyping of T. gondii, we examined the genotypes of Japanese isolates in this study. DNA sequences of 6 loci were determined in 17 Japanese isolates and compared with those of strains of 16 haplogroups. As a result, Japanese isolates were classified into four groups. We investigated the virulence of some Japanese isolates and found a highly virulent strain in mice, comparable to that of RH strain, although this Japanese isolate was sister to strains of haplogroup 2, which show moderate virulence in mice. We further investigated whether this high virulence isolate had different virulence mechanism and strategy to adapt to Japanese host from other strains by comparing the virulence-related genes, ROP5, 18 and the immunomodulatory gene, ROP16 of the isolate with those of archetypical strains (GT1, ME49 and VEG). This analysis indicated the high virulence of the isolate in mice was partly explained by gene sequences of ROP5 and ROP16. These findings lead to the elucidation of biodiversity of T. gondii and have potential to optimize the diagnostic protocol.

Emergent measles-containing vaccination recommendation for aged 6-11 months and detection of vaccine-associated measles during a large measles outbreak in Okinawa, Japan, in 2018.

Okinawa Prefecture, Japan, experienced a large measles outbreak from March to May 2018. During this outbreak, there were 99 laboratory-confirmed cases and 14 vaccine-associated measles cases. In addition to the reinforcement of routine immunization, Okinawa prefectural government introduced emergent measles-containing vaccination recommendations for infants aged 6-11 months as part of the outbreak response. Increased concern exists in Okinawa about measles in infants following a previous outbreak from 1998 to 2001, when nine children including four infants died. Of 8062 infants aged 6-11 months who received measles-containing vaccine (MCV), six developed vaccine-associated measles; incidence was 0.74 per 1000 doses (95%CI 0.27-1.62). This was similar to that of first dose routine immunization recipients at one year of age (IR 0.60, 95%CI 0.20-1.78). Among 14 vaccine-associated measles cases, throat swab samples showed the highest positive rate (92.9%) by real-time reverse transcription polymerase chain reaction (RT-qPCR), followed by urine (25.0%) and whole blood (7.7%) samples. Furthermore, one throat swab sample classified as equivocal by RT-qPCR was positive by conventional RT-PCR (RT-PCR). During an outbreak, it is critical to distinguish between cases with measles-like symptoms caused by wild circulating virus and those caused by vaccine-derived virus as accurately and urgently as possible because the public health response will be quite different. No infant deaths were observed during this outbreak, and no severe adverse events following immunization were seen among infants 6-11 months old who were given MCV as a public health response. Thus, we conclude that introduction of emergent MCV was effective and describing the characteristics of vaccine-associated measles cases during a measles outbreak will be helpful for future outbreak response efforts.

Detection of antibodies against Toxoplasma gondii in cats using an immunochromatographic test based on GRA7 antigen.

Toxoplasmosis, caused by Toxoplasma gondii, is one of the most common parasitic diseases worldwide. The GRA7 of T. gondii (TgGRA7) is an essential component of the parasitophorous vacuole (PV) and PV membrane surrounding the tachyzoites and the cyst wall of the bradyzoites. While it has been widely employed as antigen for ELISA, there is only one study that has reported its potential as antigen for immunochromatographic test (ICT) in pigs. There is no study yet documenting its potential for ICT serodiagnosis of T. gondii infection in cats. In this study, we assessed the efficacy of an ICT using TgGRA7 in the detection of Toxoplasma infections in 100 cats and compared the results with iELISAs using TgGRA7 and lysate antigens of T. gondii strains, RH, PLK, and VEG. Our results revealed that TgGRA7-ICT is a reliable test for the diagnosis of anti-T. gondii antibodies in cats, producing comparable results as conventional serological methods. This study is the first report on the use of TgGRA7 as ICT antigen for the serodiagnosis of T. gondii infection in cats.

A Toxoplasma gondii strain isolated in Okinawa, Japan shows high virulence in Microminipigs.

Toxoplasma gondii strains have been isolated all over the world and their virulence has been examined mainly using laboratory mice. However, T. gondii differs in virulence depending on the host animal species. Therefore, to evaluate the virulence of each strain in domestic animals, it is necessary to examine using not only mice but also the concerned animals. We have shown that TgCatJpOk4, a T. gondii strain recently isolated in Okinawa, Japan, has a high virulence against laboratory mice, comparable to highest virulent RH strain in mice; however, the virulence to domestic animals remains unknown. In this study, we examined the virulence using the Microminipig. After infection, four out of five infected pigs showed severe clinical symptoms: inappetence, hypoactivity and tachypnea. Eventually, three out of the five infected pigs succumbed before the end of the observation. Among the three dead pigs, histological analysis revealed that interstitial pneumonia and spotty necrosis in the liver indicating that the TgCatJpOk4 strain has a high virulence not only in laboratory mice, but in pigs as well.

Childhood leptospirosis in an industrialized country: Population-based study in Okinawa, Japan.

Leptospirosis is considered underdiagnosed because of its nonspecific presentation and lack of proper understanding of its epidemiology. Early diagnosis and treatment are crucial. However, few data are available on confirmed leptospirosis cases in children in industrialized countries. We therefore aimed to describe epidemiologic and clinical characteristics of laboratory-confirmed childhood leptospirosis in Okinawa, Japan. We reviewed the national surveillance data of pediatric leptospirosis in Okinawa, Japan from January 2003 through December 2015. The database included all of laboratory-confirmed leptospirosis diagnosed at the only central laboratory for leptospirosis in the region. There were 44 children (0-20 years of age) with laboratory-confirmed leptospirosis. Of these, 90% were male, 91% were 10-20 years of age, and 96% of cases occurred in August and September. The number of laboratory-confirmed patients ranged from 0 to 11 per year (mean: 3.3 per year), and the estimated annual rate was 1.0 per 100,000 pediatric populations. In all cases, the presumed infection route was recreational exposure to river water. Commonly observed manifestations include fever (95%), myalgia (52%), and conjunctival suffusion (52%). Childhood leptospirosis in Okinawa, Japan occurred predominantly in teenage boys after freshwater exposure in summer, and most patients had characteristic conjunctival suffusion. Cohort studies would be helpful to better understand more detailed clinical manifestations in association with prognosis.

Molecular Epidemiological Study of Mumps Epidemics of 2015 in Okinawa, Japan.

Although major mumps epidemics occurred every 4-5 years in Okinawa Prefecture in Japan, no laboratory diagnoses were conducted. A mumps epidemic started in Okinawa in October 2014, and we collected clinical samples from 31 patients in 4 areas (Hokubu, Nanbu, Miyako, and Yaeyama) from July to December 2015, for virus isolation and RT-PCR, whose positive ratios were 52% and 87%, respectively. Phylogenetic analyses showed that all isolates were classified into genotype G, and with one exception, consisted of 2 subgenotypes, Ge (55.6%) and Gw (40.7%), which have been prominent in Japan recently. One isolate was classified in another lineage, which was detected in Japan for the first time, and was similar to a Hong Kong isolate from 2014. Remarkably, the geographic distributions of the 2 major lineages were separated. The Ge viruses were isolated from the main island of Okinawa and the Yaeyama Islands, whereas the Gw isolates were mainly detected from the Miyako Islands. These results suggest that the Ge and Gw mumps viruses mainly caused the mumps epidemics of 2015 in Okinawa, and that they spread independently in separate regions. This is the first report describing the molecular epidemiology of mumps epidemics in Okinawa Prefecture.

Molecular evolution of VP3, VP1, 3C(pro) and 3D(pol) coding regions in coxsackievirus group A type 24 variant isolates from acute hemorrhagic conjunctivitis in 2011 in Okinawa, Japan.

A large acute hemorrhagic conjunctivitis (AHC) outbreak occurred in 2011 in Okinawa Prefecture in Japan. Ten strains of coxsackievirus group A type 24 variant (CA24v) were isolated from patients with AHC and full sequence analysis of the VP3, VP1, 3C(pro) and 3D(pol) coding regions performed. To assess time-scale evolution, phylogenetic analysis was performed using the Bayesian Markov chain Monte Carlo method. In addition, similarity plots were constructed and pairwise distance (p-distance) and positive pressure analyses performed. A phylogenetic tree based on the VP1 coding region showed that the present strains belong to genotype 4 (G4). In addition, the present strains could have divided in about 2010 from the same lineages detected in other countries such as China, India and Australia. The mean rates of molecular evolution of four coding regions were estimated at about 6.15 to 7.86 × 10(-3) substitutions/site/year. Similarity plot analyses suggested that nucleotide similarities between the present strains and a prototype strain (EH24/70 strain) were 0.77-0.94. The p-distance of the present strains was relatively short (<0.01). Only one positive selected site (L25H) was identified in the VP1 protein. These findings suggest that the present CA24v strains causing AHC are genetically related to other AHC strains with rapid evolution and emerged in around 2010.