Research Note: Molecular and pathologic characterization of avian adenovirus isolated from the oviducts of laying hens in eastern Japan.

Cases of poor egg production were investigated in 2 layer farms from Ibaraki Prefecture in eastern Japan. To identify any microbial agents that may have caused the problem, necropsy, bacterial isolation, histopathology, and virus detection were performed. Members of the avian adenoviruses was detected by PCR in oviduct samples from both farms; chicken anemia virus coinfection was also confirmed in one of the farms. Avian adenovirus was isolated from the oviducts of the affected chickens on each farm. Inoculation into chick embryos showed tropism for the chorio-allantoic membrane. Stunting and hemorrhaging was observed in all infected embryos, as well as death in a few. Inoculation of 1-day-old specific pathogen-free chicks, and 400-day-old commercial hens, did not result in any significant findings. The isolated viruses were analyzed by sequencing of the hexon gene and were confirmed as fowl adenovirus type-c serotype-4 (FAdV-4). The 2 virus strains were found to be 99.29% similar to each other. One of the strains, Japan/Ibaraki/Y-H6/2016, was 99.15% similar to the KR5 strain. The other, Japan/Ibaraki/M-HB2/2016, was 99.57% similar to the KR5 strain. Fiber-2 gene analysis confirmed the identity as FAdV-4 that is closely related to nonpathogenic strains. Although nonpathogenic to chicks and laying hens, this infection can possibly cause economic damage. Perhaps the bigger concern is the effect on infected breeder operations. Because the virus is fatal to 9.09% of infected embryos, this could translate to a considerable loss in chick production owing to embryonic death. This is the first report of detection and isolation of FAdV-4 from the chicken oviduct; however, further studies are needed to elucidate its impact on both layer and breeder flocks. Indeed, FAdV-4 has negative effects on the avian reproductive tract as well.

The Expanded Role of Roof-Rats (Rattus rattus) in Salmonella spp. Contamination of a Commercial Layer Farm in East Japan.

Rodents serve as amplifiers of Salmonella infections in poultry flocks and can serve as a source of Salmonella contamination in the environment even after thorough cleaning and disinfection. This study aims to determine the dynamics of Salmonella occurrence in rodents and its relation to Salmonella contamination in the layer farm environment, including air dusts and eggs. From 2008 to 2017, roof rats (Rattus rattus), environmental swabs, air dusts, and eggs were collected from an intensive commercial layer farm in East Japan and were tested for Salmonella spp. using standard procedures. In roof rat samples, the Salmonella isolation rate was reached at 10% (95% confidence interval [CI] 8.1-21.9) in which Salmonella Corvallis, Salmonella Infantis, Salmonella Potsdam, and Salmonella Mbandaka were the frequent isolates from the cecal portion of the intestines. On the other hand, the prevalence rate of Salmonella in environmental swabs was at 5.1% (95% CI 2.2-7.4) while air dusts were at 0.9% (95% CI 0.2-1.8). It was observed that the prevalence of predominant Salmonella serotypes shifted over time; in roof rats, it was noted that Salmonella Potsdam gradually replaced Salmonella Infantis. In environmental swabs and eggs, Salmonella Corvallis and Salmonella Potsdam increased significantly while Salmonella Infantis became less frequent. In air dusts, Salmonella Corvallis was observed to decrease and Salmonella Potsdam became more common. Based on our findings, the role of roof rats in the epidemiology of Salmonella in layer farms was expanded from being a reservoir and an amplifier host into a shifting vessel of the most predominant serotypes.

Antibody response and protective immunity of chickens vaccinated with booster dose of recombinant oil-adjuvanted Leucocytozoon caulleryi subunit vaccine.

Leucocytozoon caulleryi is an economically important poultry pathogen that causes subclinical to fatal disease in chickens. Because of limited preventive and treatment options against this disease, an oil-adjuvanted recombinant vaccine (O-rR7) targeting the R7 protein of L. caulleryi second-generation schizonts was developed. Different vaccination programs, namely, single vaccination at 45 days (0.1-ml dose), single vaccination at 130 days (0.25 ml), and initial vaccination at 45 days (0.1 ml) followed by a booster dose at 130 days (0.25 ml) were explored to compare the effects of single and booster vaccination on antibody response, duration of protective immunity, and degree of clinical signs after experimental L. caulleryi infection. Of the three treatments groups, initial vaccination at 45 days followed by a booster vaccination at 130 days of age resulted to rapid increase in antibody titers, which persisted for up to 182 days. Antibody titers reached peak values 35 days and 14 days after initial and booster vaccination, respectively. In comparison, single vaccination at 45 days of age resulted in production of antibodies above 1600 ELISA units for 56 days postvaccination, and single vaccination at 130 days of age produced peak antibody titers 35 days postvaccination, which remained above 1600 ELISA units for 126 days. Experimental infection of L. caulleryi at 256 days, when antibody titers had waned, did not result to severe clinical disease in chickens that received booster vaccination, whereas mild to severe disease was observed in chickens that received a single vaccination. Evaluation of immune response at 15 and 21 days postinfection showed that chickens that received booster vaccination had a twofold increase (P < 0.01) in antibody titers as compared to those receiving a single vaccination. Administering booster shots of O-rR7 is therefore recommended, especially in farms located in areas where Leucocytozoon is endemic.