Tadao Imada

National Institute of Animal Health, Tsukuba, Ibaraki, Japan

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Publications (31)65.31 Total impact

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    ABSTRACT: The sequences of short fiber genes of the Fowl adenovirus serotype 4 (FAdV-4), including isolates from chickens with hydropericardium syndrome (HPS), in Japan, India, and Pakistan were compared. By phylogenetic analysis based on complete nucleotide sequences of this gene, FAdV-4 strains from HPS (HPS-FAdV-4) in Japan, India, and Pakistan fell into a different cluster from FAdV-4 strains not derived from HPS. Hydropericardium syndrome-FAdV-4 isolates were differentiated from other FAdV-4 strains by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis using the enzyme the Alu I. The use of PCR-RFLP analysis of short fiber genes may be useful to distinguish among FAdV-4 strains.
    Journal of veterinary diagnostic investigation: official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc 03/2010; 22(2):218-23. · 1.18 Impact Factor
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    ABSTRACT: We genetically characterized fowl adenoviruses (serotype 4 FAdV, FAdV-4) isolated from chickens with hydropericardium syndrome (HPS) in Japan by the polymerase chain reaction (PCR) method coupled with direct sequencing. Phylogenetic analysis based on the part of the hexon gene that included the L1 region revealed that all FAdV-4 isolates from chickens with HPS in Japan were identical and were distinguished completely from the cluster including FAdV strains from chickens with HPS in India and Pakistan. This suggested that FAdV-4 from the HPS chickens in India and Pakistan was derived from a common ancestor, but the origin of the FAdV-4 from the HPS chickens in Japan was completely different.
    Journal of Veterinary Medical Science 11/2009; 71(11):1455-8. · 0.88 Impact Factor
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    ABSTRACT: Polymerase chain reaction (PCR) coupled with direct sequencing of the product of the hexon gene was applied to avian adenoviruses (formerly group I-III). The expected sizes of DNA fragments were successfully amplified by PCR from all of the group I-III avian adenoviruses with our designed primers. The resulting PCR product contained diagnostically relevant hexon sequences that could be used to identify the group and type of avian adenovirus.
    Journal of Veterinary Medical Science 09/2009; 71(9):1239-42. · 0.88 Impact Factor
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    ABSTRACT: Seventeen isolates of Newcastle disease virus (NDV) were obtained from various prefectures in Japan during the years 2001-2007 and were genotypically analyzed by the reverse transcriptase-polymerase chain reaction (RT-PCR) method coupled with direct sequencing. These NDV isolates were classified into three genetic groups that had been reported previously, namely, genotypes I, VI and VII. The isolate from an aigamo duck was classified into genotype I with isolates mainly from waterfowl. All isolates from pigeons were classified into genotype VI, the predominant genotype responsible for most Newcastle disease outbreaks in pigeons. The isolate from a pet bird was classified into genotype VI, distinct from the remaining viruses in genotype VI. All isolates from chickens were classified into genotype VII, the predominant genotype responsible for most Newcastle disease outbreaks in the East Asian countries. Among the isolates from chickens, isolates after 2002 were genetically most closely related with isolates in Korea. The single isolate from a wild cormorant was also classified into genotype VII, although it was different from the recent NDV epidemic strain in Japan.
    Journal of Veterinary Medical Science 09/2009; 71(8):1101-4. · 0.88 Impact Factor
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    ABSTRACT: To understand the genetic diversity of the S2 gene of infectious bronchitis viruses (IBV) isolated in Japan, we determined the nucleotide sequences of these IBVs using the reverse transcriptase polymerase chain reaction method coupled with direct sequencing. IBV isolated in Japan were classified into six different groups by phylogenetic analysis based on the S2 gene. However, the classification based on the S2 gene of IBV isolated in Japan was different for some of the strains from those obtained with our previous analysis of the S1 gene. This suggested that genetic recombination between the virus strains classified into different genetic groups had occurred in poultry, and that recombinant viruses might be epidemic in Japan.
    Journal of Veterinary Medical Science 04/2009; 71(3):287-91. · 0.88 Impact Factor
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    ABSTRACT: Cuatro aislados de pneumovirus de pollos diagnosticados clínicamente con el síndrome de la cabeza hinchada fueron caracterizados genéticamente hasta su subtipo. Los resultados de transcriptasa reversa y reacción en cadena por la polimerasa basados en los iniciadores específicos para subtipo y el análisis directo de la secuencia de los genes G indicaron la presencia en Japón de los subtipos A y B, pero no la de los subtipos C o D. Se analiza la posibilidad de varias fuentes o rutas que pueden invadir al Japón con el pneumovirus. Abbreviations: APV = avian pneumovirus; CPE = cytopathic effects; PCR = polymerase chain reaction; RT = reverse transcriptase; SHS = swollen head syndrome
    Avian Diseases 01/2009; · 1.73 Impact Factor
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    ABSTRACT: Eight isolates of infectious bronchitis virus (IBV) were obtained from various prefectures in Japan during 2003-2007 and were genetically analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR) coupled with direct sequencing. These IBV isolates were classified into three genetic groups, including two that have already been reported (JP-I and JP-III). The remaining group is related to the 4/91 (also known as 793/B) type, prevalent mainly in European countries, and has not been identified in Japan until now.
    Journal of Veterinary Medical Science 01/2009; 70(12):1341-4. · 0.88 Impact Factor
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    ABSTRACT: Highly pathogenic avian influenza (HPAI) viruses of the H5N1 subtype have caused several rounds of outbreaks in Thailand. In this study, we used 3 HPAI viruses isolated in Thailand in January 2004 from chicken, quail, and duck for genetic and pathogenetic studies. Sequence analysis of the entire genomes of these isolates revealed that they were genetically similar to each other. Chickens, quails, domestic ducks, and cross-bred ducks were inoculated with these isolates to evaluate their pathogenicity to different host species. A/chicken/Yamaguchi/7/04 (H5N1), an HPAI virus isolated in Japan, was also used in the chicken and quail studies for comparison. All four isolates were shown to be highly pathogenic to chickens and quails, with 100% mortality by 10(6) EID50 inoculants of the viruses. They caused sudden death in chickens and quails within 2-4 days after inoculation. The mean death times (MDT) of quails infected with the Thai isolates were shorter than those of chickens infected with the same isolates. Mortality against domestic and cross-bred ducks ranged from 50 to 75% by intranasal inoculation with the 10(6) EID50 viruses. Neurological symptoms were observed in most of the inoculated domestic ducks and appeared less severe in the cross-bred ducks. The MDTs of the ducks infected with the Thai isolates were 4.8-6 days post-inoculation. Most of the surviving ducks infected with the Thai isolates had sero-converted until 14 dpi. Our study illustrated the pathobiology of the Thai isolates against different poultry species and would provide useful information for improving control strategies against HPAI.
    Veterinary Microbiology 08/2008; 133(1-2):65-74. · 3.13 Impact Factor
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    ABSTRACT: Specific-pathogen-free chickens inoculated with H5N1 highly pathogenic avian influenza (HPAI) viruses isolated in Japan in 2004 were investigated pathologically. The chickens inoculated intravenously with the viruses died within 26 hr after inoculation. Macroscopically, minimal necrosis of the tip of the comb, and hemorrhages of the palpebral conjunctiva, liver, cerebellum, and muscles were rarely observed. Histologically, dead chickens had minimal focal necrosis of hepatocytes with fibrinous thrombi in sinusoids, mild necrosis of splenic ellipsoids with fibrinous exudation, minimal necrosis of the brain, mild necrosis of epidermal cells of the comb with congestion of the lamina propria, and hemorrhages and edema of the lamina propria of the conjunctiva. Virus antigens were seen in the sinusoidal endothelial cells and hepatocytes in the liver, the capillary endothelial cells of the spleen, the capillary endothelial cells and cardiac myocytes in the heart, the capillary endothelial cells and necrotic nerve cells in the brain, the capillary endothelial cells in the lamina propria of the comb, the renal tubular epithelial cells, and the pancreatic acinar cells. The chickens inoculated by natural infectious routes died within 1-4 days after inoculation. Macroscopically, some chickens had hemorrhages in the conjunctiva, edematous swelling of the face and wattles, hydropericardium, hemorrhages of the proventriculus and bursa of Fabricius, increased secretion of tracheal mucus, and congestion and edema of lungs. Histologic lesions by natural infectious routes were similar to those by intravenous inoculation, except for the pancreatic necrosis. This study suggests H5N1 HPAI viruses isolated in Japan in 2004 cause pathologic conditions similar to natural cases.
    Avian Diseases 04/2008; 52(1):8-13. · 1.73 Impact Factor
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    ABSTRACT: Typically highly pathogenic avian influenza (HPAI) viruses spread very rapidly among chickens within sheds. However, the spread was slower than expected for the initial 10 days of the index farm in Japan during 2004. This slow spread, as well as the lack of gross lesions, clinical signs, or high mortality, hindered the field veterinarian from reporting a suspected HPAI outbreak to the veterinary office. To understand the field conditions for the slow virus spread, we examined contact and airborne transmission of the H5N1 virus to chickens in a negative-pressure isolator using various numbers of infected chickens and separate compartments. We found that the contact transmission did occur inefficiently when one or two chickens were infected, whereas the transmission was efficient when four chickens were infected. Airborne transmission of the HPAI virus was also dependent on the number of infected chickens and was less efficient than contact transmission. These data together with field observations suggested that number of infected chickens, chicken house types, and amount of environmental contamination might affect the virus transmission efficiency to chickens.
    Avian Diseases 04/2007; 51(1):129-32. · 1.73 Impact Factor
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    ABSTRACT: To evaluate the potential pathogenicity to mammals of the recent H5N1 avian influenza A virus, viruses recovered from dead mice infected with A/chicken/Yamaguchi/7/2004 isolated in Japan were examined. All recovered viruses from the brains of dead mice infected with this strain (without any prior adaptation to mice) had substituted the amino acid at position 627 of the PB2 protein from glutamic acid to lysine. Their mouse lethality had increased by approximately 5 x 10(4) times over that of the original virus. Histopathological analysis reinforced the finding that these variants caused more rapid and severe damage to mice than the original virus. This revealed that it might be useful to characterize the recovered virus to assess its potential pathogenicity to mammals.
    Journal of General Virology 01/2007; 87(Pt 12):3655-9. · 3.13 Impact Factor
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    ABSTRACT: The protective effect of the A/Ck/Yoko/aq55/01 (H9N2) avian influenza virus against the highly pathogenic H5N1 virus, i.e., A/Ck/Yama/7/04 (genotype V), was examined. Three 5-week-old chickens were inoculated intranasally with the H9N2 virus (10(8.6) EID(50)/head) and were kept with two contact chickens. All of the infected chickens were reinoculated with the same virus at 20 weeks of age, and 10 days later, they were challenged intranasally with the H5N1 virus (10(4.0) EID(50)/head). Five chickens simultaneously challenged with only the H5N1 virus (challenge control) died within 4 days postchallenge (d.p.c.). In contrast, four out of the five challenged, immune chickens died from 5 to 8 d.p.c. The median time to death in the immune chickens (6.3 days) was significantly longer than that in the challenge controls (3.4 days) (P < 0.01). No H5N1 virus shedding into the tracheae and feces of the challenged, immune chickens were detected for 3 d.p.c., but H5 genes were detectable in only one chicken by a loop-mediated isothermal amplification method. The H5N1 viruses were detected in the tracheae and/or feces of the dead immune chickens at death or 1 to 2 days before death. Only one out of the five challenged, immune chickens survived the H5N1 challenge without any signs for 14 d.p.c., but the virus and H5 gene were sporadically detected in the trachea only 7 and 14 d.p.c., respectively. This study shows that the H9N2 viruses may have the potential to induce cross-protection to the challenge with a recent lethal H5N1 virus (genotype V).
    Archives of Virology 01/2007; 152(7):1395-400. · 2.03 Impact Factor
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    ABSTRACT: Highly pathogenic H5N1 avian influenza viruses were isolated in 9 large-billed crows that died in Kyoto and Osaka prefectures in Japan from March to April in 2004. We studied 3 of the 9 crows using standard histologic methods, immunohistochemistry, and virus isolation. The most prominent lesions were gross patchy areas of reddish discoloration in the pancreas. The consistent histologic lesions included severe multifocal necrotizing pancreatitis, focal degeneration and necrosis of neuron and glial cells in the central nervous system, and focal degeneration of cardiac myocytes. All of these tissues contained immunohistochemically positive influenza viral antigens. The virus was isolated from the brain, lung, heart, liver, spleen, and kidney of the crows examined. Thus we concluded that highly pathogenic avian influenza virus was associated with clinical disease, severe pathologic changes, and death in the 3 crows.
    Veterinary Pathology 08/2006; 43(4):500-9. · 1.93 Impact Factor
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    ABSTRACT: Cutaneous fowlpox occurring in vaccinated layer hens was investigated pathologically and microbiologically. Anorexia, decrease of egg production, increased mortality, yellow scabs on faces, and alopecia of feathered skins with yellow scabs were observed in affected hens. Histologically, proliferative and necrotic dermatitis with eosinophilic ring-shaped cytoplasmic inclusions (Bollinger bodies) and clumps of gram-positive cocci (Staphylococcus hyicus) were noted in the affected birds. Fowlpox lesions were primarily observed in the feathered skins. Proliferation of feather follicle epidermal cells, with cytoplasmic inclusions and degeneration of the feather, and bacterial clumps in the feather follicles were noted in the affected skins. Ultrastructurally, characteristic fowlpox viral particles were observed in the cytoplasmic inclusions of hyperplastic epidermal cells. Amyloid deposition was observed in the Disse space of the liver, splenic sinus, and lamina propria of the bronchiolar, bronchial, and tracheal areas. Amyloidosis could be one factor inducing the fowlpox infection in vaccinated chickens.
    Avian Diseases 04/2006; 50(1):152-6. · 1.73 Impact Factor
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    ABSTRACT: We examined the pathogenicity for chickens of two H5N1 avian influenza viruses isolated in Japan, A/chicken/ Yamaguchi/7/2004 (Ck/Yamaguchi/7/04) isolated from outbreaks in commercial layer chickens, and A/duck/Yokohama/aq10/ 2003 (Dk/Yokohama/aq10/03) isolated from duck meat imported from China. All chickens inoculated intranasally with either strain died, and the viruses were reisolated from all organs examined. However, both the mean time of onset of clinical signs and the mean death time of Ck/Yamaguchi/7/04 were shorter than those of Dk/Yokohama/aq10/03.
    Avian Diseases 01/2006; 49(4):582-4. · 1.73 Impact Factor
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    ABSTRACT: An isolate of Nipah virus was injected into fertile eggs via the allantoic cavity or yolk sac. Allantoic inoculation resulted in considerable pathological variation and only partial mortality. Dead embryos showed severe necrosis in the brain and congestion in the kidney and the subcutis of limbs. In contrast, yolk sac inoculation led to uniform infection and mortality, the dead embryos exhibiting the same lesions as those described above but without the subcutaneous congestion. Histological lesions in dead embryos inoculated by either route were similar and particularly severe in the central nervous system. Viral antigens were detected mainly in the vasculature and neurons. The results indicated that Nipah virus is highly pathogenic to chicken embryos, and that the route of inoculation is an important determinant of the course of disease. The findings also suggested that yolk sac inoculation can be used for viral titration, and that the chicken embryo represents a useful model for studying the vascular and neuronal tropisms of Nipah virus.
    Journal of Comparative Pathology 01/2006; 135(2-3):74-82. · 1.38 Impact Factor
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    ABSTRACT: In Japan, between the end of December 2003 and March 2004, four outbreaks of acute, highly transmissible and lethal disease occurred in birds in three prefectures separated by 150-450 km, involving three chicken farms and a group of chickens raised as pets. The cause of each outbreak was an H5N1 influenza A virus-the first highly pathogenic virus to be isolated from the outbreaks in Japan since 1925. The H5N1 virus was also isolated from dead crows, apparently infected by contact with virus-contaminated material. These H5N1 viruses were antigenically similar to each other, but could be differentiated from other H5 viruses, including those isolated from Hong Kong in 1997 and 2003, by use of a panel of monoclonal antibodies in hemagglutination inhibition assays. Genetically, the H5N1 viruses in Japan were closely related to each other in all genes and were genetically closely related to a single isolate of genotype V that was isolated in 2003 in the Guandong Province of mainland China (A/chicken/Shantou/4231/2003). The virulence of the index isolate (A/chicken/Yamaguchi/7/2004) was studied in chickens and mice. Chickens intravenously or intranasally inoculated with the isolate died within 1 or 3 days of inoculation, respectively. In mice, although this virus replicated well in the lung without prior adaptation and spread to the brain, the dose lethal to 50% of the mice was 5 x 10(5) 50% egg infectious doses (EID50), which is less pathogenic than the Hong Kong 1997 H5N1 viruses isolated from humans. Our findings indicate that the H5N1 viruses associated with the influenza outbreaks in chickens in Japan were genotypically closely related to an H5N1 virus isolated from chicken in China in 2003 (genotype V), but were different from those prevalent in southeastern Asia in 2003-2004 (i.e., genotype Z) and that these highly pathogenic viruses can be transmitted to crows, which are highly susceptible to these viruses.
    Virology 03/2005; 332(1):167-76. · 3.37 Impact Factor
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    ABSTRACT: Outbreaks of highly pathogenic avian influenza (HPAI) caused by H5N1 virus occurred during 2003 to 2004 in Korea and Japan. The H5N1 viruses isolated in both countries were genetically similar at > 99% identity in the nucleotide sequences of all eight RNA segments, indicating that they belong to genotype V and are distinct from HPAI viruses prevalent in southeast Asia that belong to genotype Z. These findings indicate that the H5N1 viruses that caused the HPAI outbreaks in both Korea and Japan were derived from a common ancestor.
    Microbiology and Immunology 01/2005; 49(9):871-4. · 1.55 Impact Factor
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    ABSTRACT: A monoclonal antibody (MAb) based solid-phase blocking ELISA was developed for detection of antibodies to Nipah virus. The ELISA was designed to detect remaining antigens on the plate with anti-Nipah MAb conjugate after the reaction with sample serum, and enabled simple procedure, detection of neutralizing antibody to Nipah virus, and application of samples from different animal species. Forty of 200 swine reference sera examined were positive by the ELISA, of which thirty seven were found positive by serum neutralization test. Sera from a total of 131 fruit bats captured in Malaysia were also tested and all found negative by the both tests. It is considered that the solid-phase blocking ELISA can be used as a screening test for Nipah virus infection followed by the serum neutralization test as confirmatory test.
    Journal of Virological Methods 12/2004; 121(2):259-61. · 1.90 Impact Factor
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    ABSTRACT: The immunohistochemical reactivity of seven clones of mouse monoclonal antibodies raised to Nipah virus antigens were investigated using formalin-fixed, paraffin embedded porcine and equine lung tissues from experimental Nipah and Hendra virus infection, respectively. Either microwave irradiation or enzymatic digestion effectively unmasked the viral antigens in formalin-fixed, paraffin-embedded tissue sections. Four clones showed positive reaction to both Nipah virus-infected porcine lung tissue and Hendra virus-infected equine lung tissue. Two clones (11F6 and 13A5) reacted with Nipah virus-infected porcine lung tissue, but not with Hendra virus-infected equine lung tissue. These Nipah virus-specific monoclonal antibodies may therefore be useful for immunohistological diagnosis of Nipah virus infection and for further research on Nipah virus pathogenesis.
    Journal of Veterinary Medical Science 11/2004; 66(10):1263-6. · 0.88 Impact Factor