Ken-ichiro Kameyama

The recent prevalence of bovine leukemia virus (BLV) infection among Japanese cattle

A seroepidemiological survey of bovine leukemia virus (BLV) infection was conducted in Japan in 2007 using an enzyme-linked immunosorbent assay (ELISA) and an agar gel immunodiffusion (AGID) test. A total of 5420 cattle (dairy, 3966; breeding beef, 797; fattening beef, 657) from 209 farms in seven prefectures in Japan were tested. The overall prevalence of BLV infection was 28.6%. The prevalence of BLV infection in dairy cattle (34.7%) was higher than for both fattening beef cattle (7.9%) and breeding beef cattle (16.3%). Age-specific prevalence showed that BLV prevalence increased with age in all types of cattle and was notably different between dairy and beef cattle under 1 year of age. Among 207 farms, 141 herds (68.1%) had one or more positive animals. The proportion of these positive farms was significantly higher among dairy farms (79.1%) than among beef breeding farms (39.5%) and beef fattening farms (51.9%) (P<0.001). Dairy farms (40.5%) also showed a significantly higher within-herd prevalence than beef breeding (27.4%) and fattening (14.9%) farms (P=0.001). This study indicated that BLV is more widely spread in dairy cattle than in beef breeding cattle in Japan. Given the prevalence of BLV infection in dairy and beef cattle was 8- and 1.7-fold higher, respectively, than rates previously found in 1980-1982, BLV appears to be spreading particularly among the dairy cattle population during the last two decades. Further investigation is required to determine the risk factors necessary to control BLV infection that take into account the different farming practices that exist between dairy and beef sectors.

Phylogenic analysis of the M genes of influenza viruses isolated from free-flying water birds from their Northern Territory to Hokkaido, Japan

During 2000–2007, 218 influenza viruses of 28 different combinations of HA (H1–H13) and NA (N1–N9) subtypes were isolated from fecal samples of free-flying water birds at two distant lakes in Hokkaido, Japan. Phylogenic analysis of the matrix (M) genes of 67 strains, selected on the basis of their subtype combinations, revealed that A/duck/Hokkaido/W95/2006 (H10N8) was a reassortant whose M gene belonged to North American non-gull-avian and the other seven genes to Eurasian non-gull-avian lineages. The M genes of other 65 strains belonged to Eurasian non-gull-avian and the one to Eurasian-gull lineages. The M genes of 65 strains were grouped into three different sublineages, indicating that influenza viruses circulating in different populations of free-flying water birds have evolved independently in nature.

Complete Genome Sequence of the First Isolate of Genotype C Bovine Parainfluenza Virus Type 3 in Japan

ABSTRACT Bovine parainfluenza virus type 3 (BPIV3) isolates are classified into three genotypes (BPIV3a to -c). Here, we report the complete genome sequence of the BPIV3c isolate for the first time in Japan. Our results indicate that new primer sets will be required to detect all genotypes of BPIV3 strains.

Cleavage of the NS2-3 protein in the cells of cattle persistently infected with non-cytopathogenic bovine viral diarrhea virus

The NS2‐3 of BVDV is cleaved in cultured cells infected with cp BVDV but not in those infected with ncp BVDV when tested more than 10 hours post infection. However, it is not known whether cleavage of NS2‐3 occurs in vivo. In the present study, cleavage of NS2‐3 in cattle persistently infected with BVDV was investigated. All BVDV isolated from PI animals were of the ncp biotype, and NS2‐3 proteins were detected in bovine fetal muscular cells infected with these viruses. On the other hand, in the leukocytes of those PI animals, NS3 proteins, products of the cleavage of NS2‐3 proteins, were detected. In addition, the NS3 proteins were also detected in leukocytes artificially infected with ncp BVDV. These results reveal that the NS2‐3 protein of BVDV is cleaved in leukocytes. Furthermore, NS3 proteins were detected in many tissues of PI cattle, such as lymphoid tissue, brain, thyroid, lung, and kidney. These results suggest that the NS2‐3 protein of ncp BVDV cleaves in vivo.

First isolation of border disease virus in Japan is from a pig farm with no ruminants

The first isolation of border disease virus (BDV) in Japan was from a pig farm of the farrow-to-finishing type that kept no small ruminants or cattle. The infection was detected in the course of sero-surveillance for classical swine fever virus (CSFV) in Japan. The infected pigs had no clinical symptoms of CSFV or other disease; nevertheless, a high sero-positive rate of 58.5% was identified. A persistently infected pig with the BDV was found and suspected to be the cause of sero-prevalence in the farm. The isolated BDV was genetically close to BDV strains from New Zealand, but there was no epidemiological evidence concerning the route(s) of the invasion into the farm.

The role of neighboring infected cattle in bovine leukemia virus transmission risk

A cohort study was conducted to evaluate the risk of bovine leukemia virus (BLV) transmission to uninfected cattle by adjacent infected cattle in 6 dairy farms. Animals were initially tested in 2010–2011 using a commercial ELISA kit. Uninfected cattle were repeatedly tested every 4 to 6 months until fall of 2012. The Cox proportional hazard model with frailty showed that uninfected cattle neighboring to infected cattle (n=53) had a significant higher risk of seroconversion than those without any infected neighbors (n=81) (hazard ratio: 12.4, P=0.001), implying that neighboring infected cattle were a significant risk factor for BLV transmission. This finding provides scientific support for animal health authorities and farmers to segregate infected cattle on farms to prevent spread of BLV.

Complete Genome Sequences of Bovine Parainfluenza Virus Type 3 Strain BN-1 and Vaccine Strain BN-CE

ABSTRACT Bovine parainfluenza virus type 3 (BPIV3) is associated with upper respiratory disease in cattle in many countries. Here, we report the complete genome sequences of the BPIV3 BN-1 strain, isolated from cattle in Japan, and the BN-CE vaccine strain, derived from the BN-1 strain by passages in chicken embryo fibroblasts.

Infection of the upper respiratory tract of hamsters by the bovine parainfluenza virus type 3 BN-1 strain expressing enhanced green fluorescent protein

Bovine parainfluenza virus type 3 (BPIV3) is an important pathogen associated with bovine respiratory disease complex (BRDC). We have generated a recombinant BPIV3 expressing enhanced green fluorescent protein (rBPIV3-EGFP) based on the BN-1 strain isolated in Japan. After intranasal infection of hamsters with rBPIV3-EGFP, EGFP fluorescence was detected in the upper respiratory tract including the nasal turbinates, pharynx, larynx, and trachea. In the nasal turbinates, rBPIV3-EGFP attained high titers (>10(6) TCID50/g of tissue) 2-4 days after infection. Ciliated epithelial cells in the nasal turbinates and trachea were infected with rBPIV3-EGFP. Histopathological analysis indicated that mucosal epithelial cells in bronchi were shed by 6 days after infection, leaving non-ciliated cells, which may have increased susceptibility to bacterial infection leading to the development of BRDC. These data indicate that rBPIV3-EGFP infection of hamsters is a useful small animal model for studying the development of BPIV3-associated BRDC.

Serological survey of caprine arthritis-encephalitis virus infection in Japan.

A serological survey of caprine arthritis-encephalitis virus (CAEV) infection was conducted from September 2006 to February 2007 in Japan. A total of 857 serum samples were collected from 113 herds in 28 prefectures and were analyzed for the presence of CAEV antibodies using agar gel immunodiffusion test. The seroprevalence of CAEV infection at the herd and animal levels was 15.0% (17/113) and 10.0% (86/857), respectively. Large farms with more than 10 goats and with animals for dairy and breeding purposes had higher seroprevalence (P<0.05). The results of this study provide useful information to consider effective control programs against CAEV infection in Japan.

Stability of recombinant bovine interferon-γ antiviral activity in the absence of stabilizing additives

The stability of recombinant bovine interferon‐γ (rbIFN‐γ) produced by a baculovirus expression system was investigated under different storage conditions: freezing‐thawing and storage for 30 days at temperatures of −80, 4, 25, and 37°C. Antiviral activity was not significantly decreased by freeze‐thawing at least five times. Furthermore, although not statistically different, antiviral activity gradually decreased as temperature increased. These findings suggest that rbIFN‐γ possesses high thermal and freeze‐thaw stability.