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 and phylogenetic analysis of hepatitis E viruses from mongooses in Okinawa, Japan.

Hepatitis E virus (HEV) infection has previously been reported in wild mongooses on Okinawa Island; to date however, only one HEV RNA sequence has been identified in a mongoose. Hence, this study was performed to detect HEV RNA in 209 wild mongooses on Okinawa Island. Six (2.9%) samples tested positive for HEV RNA. Phylogenetic analysis revealed that 6 HEV RNAs belonged to genotype 3 and were classified into groups A and B. In group B, mongoose-derived HEV sequences were very similar to mongoose HEV previously detected on Okinawa Island, as well as to those of a pig. This investigation emphasized the possibility that the mongoose is a reservoir animal for HEV on Okinawa Island.

Evaluation of the petrifilm aerobic count plate for enumeration of aerobic marine bacteria from seawater and Caulerpa lentillifera.

The enumeration and evaluation of the activity of marine bacteria are important in the food industry. However, detection of marine bacteria in seawater or seafood has not been easy. The Petrifilm aerobic count plate (ACP) is a ready-to-use alternative to the traditional enumeration media used for bacteria associated with food. The purpose of this study was to evaluate the usefulness of a simple detection and enumeration method utilizing the Petrifilm ACP for enumeration of aerobic marine bacteria from seawater and an edible seaweed, Caulerpa lentillifera. The efficiency of enumeration of total aerobic marine bacteria on Petrifilm ACP was compared with that using the spread plate method on marine agar with 80 seawater and 64 C. lentillifera samples. With sterile seawater as the diluent, a close correlation was observed between the method utilizing Petrifilm ACP and that utilizing the conventional marine agar (r=0.98 for seawater and 0.91 for C. lentillifera). The Petrifilm ACP method was simpler and less time-consuming than the conventional method. These results indicate that Petrifilm ACP is a suitable alternative to conventional marine agar for enumeration of marine microorganisms in seawater and C. lentillifera samples.

Survey of Japanese encephalitis virus in pigs on Miyako, Ishigaki, Kume, and Yonaguni Islands in Okinawa, Japan.

Serum specimens were collected from 125 pigs on Miyako Island, 112 pigs on Ishigaki Island, and 42 pigs on Kume Island from 2005 to 2007, and 54 pigs on Yonaguni Island from 2006 to 2007. Their sera were tested for Japanese encephalitis virus (JEV) antibody by hemagglutination inhibition (HI) assay. Five serum samples (4.5%) from Ishigaki Island were positive for HI antibody, and 4 of the 5 samples were positive for 2-mercaptoethanol- sensitive antibody (IgM Ab). All samples from Miyako, Kume, and Yonaguni Islands were negative for HI antibody. Our results indicate that JEV transmission activity was extremely low on Miyako, Ishigaki, Kume, and Yonaguni Islands. The JEV genome (JEV-RNA) was detected from the sera of one pig on Ishigaki Island. The partial gene of the E region (151 nt) was analyzed phylogenetically. The analysis showed that the new JEV-RNA belonged to genotype 3 and was closely related to JEV strains isolated in Taiwan from 1985 to 1996. It was suggested that JEV previously introduced from Taiwan had been maintained on Ishigaki Island.

[Investigation and culture of microbial contaminants of Caulerpa lentillifera (Sea Grape)].

Caulerpa lentillifera is a kind of edible seaweed, known as 'sea grape' or 'green caviar'. It is used in fresh salads. However, it is sensitive to low temperature and osmotic pressure, and is easily spoilt by storage in a refrigerator or washing with tap water. That is the reason why it is difficult to prevent food poisoning, especially due to Vibrio parahaemolyticus. In this study we investigated of marine bacteria and V. parahaemolyticus in C. lentillifera and cultured them in order to develop effective control of bacteria in commercial farms. The sixteen farms in the Okinawa Islands were investigated from August to September in 2006. A total of 176 samples were collected from eleven points during the cultivation processes and from the products. About 10(3) cfu/mL of marine bacteria were detected in the seawater used in the tank culture, but after cultivation of C. lentillifera the number had increased to about 10(6) cfu/mL. The number of marine bacteria in C. lentillifera did not change significantly through the process of planting to the final product (about 10(7) cfu/g). V. parahaemolyticus was detected in seawater from all processes and C. lentillifera was isolated from 56% of seawater, 25% of seed-stocks, and 18.8% of product samples, though but thermostable direct hemolysin gene was not detected from enrichment cultures or isolated V. parahaemolyticus strains. These results indicate that for prevention of food poisoning by V. parahaemolyticus in C. lentillifera, it is important to establish a suitable sterilization procedure for each process.

Recent change of the antigenicity and genotype of Japanese encephalitis viruses distributed on Okinawa Island, Japan.

In this study, five isolates of Japanese encephalitis virus (JEV) were obtained from swine serum samples collected on Okinawa Island, Japan, between 2002 and 2003. All five JEV isolates belonged to genotype 1, and JEV isolates obtained from the island before 1992 were genotype 3. Genotype 1 was known to be distributed from northern Thailand to Cambodia and recently expanded to Australia, Vietnam, the Republic of Korea, and Japan. However, phylogenetic analysis showed that the source of the newly emerging genotype 1 in Asia is different from that in Australia. Sero-epidemiologic investigations showed that serum samples collected from 1985 to 1988 from JEV-immune swine neutralized both the Naha Meat 54 strain (1985 JEV Okinawan isolate from swine, genotype 3) and the Oki 431S strain (2002 JEV Okinawan isolate from swine, genotype 1), and many samples collected in 2002 neutralized the Oki 431S strain but not the Naha Meat 54 strain. These results strongly suggest that the genotype and antigenicity of JEV on Okinawa Island have changed significantly over the past decade.

Survey of the antibody against japanese encephalitis virus in Ryukyu wild boars (Sus scrofa riukiuanus) in Okinawa, Japan.

Serum specimens were collected from 99 wild boars in the Northern area of the main Okinawa Island and from 27 wild boars on Iriomote Island in Okinawa Prefecture from 1997 to 2005. Sera were tested for Japanese encephalitis virus (JEV) antibody by hemagglutination inhibition assay and IgG enzyme-linked immunosorbent assay. Sixty-four samples (64.6%) in the Northern area and 1 sample (3.7%) from Iriomote Island were positive for the JEV antibody. The difference in seroprevalence between the Northern area and Iriomote Island was statistically significant (P < 0.01, chi2 test). This difference may be due to the lack of a pig farm on Iriomote Island, whereas wild boars in the Northern area may be infected with JEV, amplified on pig farms. It is likely that there has recently been an increase in the number of wild boars living close to humans in certain areas of Japan. This in turn increases the possibility that wild boars are infected with JEV, which is amplified on pig farms, and these infected animals may play a role in carrying JEV to other regions of the country.

Molecular epidemiological analyses of Japanese encephalitis virus isolates from swine in Japan from 2002 to 2004.

To characterize Japanese encephalitis virus (JEV) strains recently prevalent in Japan, JEV surveillance was performed in pigs from 2002 to 2004. Eleven new JEV isolates were obtained and compared with previous isolates from Japan and other Asian countries. All of the isolates were classified into genotype 1 by nucleotide sequence analysis of the E gene. Two new isolates with different levels of neurovirulence and neuroinvasiveness, but with only one nucleotide difference in the E gene, Sw/Mie/34/2004 and Sw/Mie/40/2004, were isolated at the same farm on the same day. Sw/Mie/40/2004 displayed higher neurovirulence and neuroinvasiveness in mice than the other four new isolates. Another new isolate, Sw/Hiroshima/25/2002, was neutralized by antiserum to Beijing-1 at a level similar to the homologous Beijing-1 strain, whilst seven other new isolates were neutralized at 10-fold-lower titres. However, there were no amino acid differences in the E protein among these eight isolates. The present study indicated that the 11 new JEV isolates were genetically similar, but biologically and serologically heterogeneous.

Sporadic cases and an outbreak of leptospirosis probably associated with recreational activities in rivers in the northern part of Okinawa Main Island.

In the summer of 2003, sporadic cases and an outbreak of human leptospirosis probably related to recreation in rivers occurred in the northern part of Okinawa Main Island. Sixteen of 22 suspected cases were definitely diagnosed as leptospirosis by serological test or isolation. The infective leptospiral serovar in 14 cases was presumed to be Hebdomadis. Transmission was thought to occur by exposure to river water that was contaminated by the urine of infected animals. The findings indicate that recreation in rivers in this area is a significant risk factor for infection with leptospires.

Characterization of Salmonella isolated in Okinawa, Japan.

Salmonella enterica strains isolated in Okinawa between 1995 and 2005 were analyzed with respect to their serovars and antimicrobial susceptibility, and pulsed-field gel electrophoresis (PFGE) was used to examine their digestion patterns. A total of 1,071 isolates, including 610 from humans, 358 from animal rectal swabs and 103 from meat obtained at grocery stores, were examined. The first 3 most frequent serovars in human isolates were Enteritidis, Weltevreden and Bareilly, together accounting for 65% of the isolates. In isolates from the rectal swabs of laying hens, the predominant serovars were Albany, Saintpaul and Aarhus, accounting for 82% of the isolates. In broilers, 123 of 124 isolates belonged to serovar Infantis, which reflected the high ratio of this serovar in the chicken sold at grocery stores. An antibiogram of human isolates was different from that of broilers and chicken. Chromosomal DNAs of S. Infantis isolated from humans and from the rectal swab of broilers and chickens were examined by PFGE using the restriction enzymes XbaI and BlnI. The digestion patterns of human isolates were not coincident with those of the isolates from the rectal swab of broilers and chicken-meat samples.