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Persistent Infection with Chicken Anemia Virus in 3-Week-Old Chickens Induced by Inoculation of the Virus by the Natural Route
Open AccessArticle

Oral Inoculation of Specific-Pathogen-Free Chickens with Chicken Anemia Virus Induces Dose-Dependent Viremia and Transient Anemia

1
Department of Veterinary Medicine, College of Veterinary Medicine, National Pingtung University of Science and Technology, Pingtung 91201, Taiwan
2
Faculty of Veterinary Medicine, Rajamangala University of Technology Tawan-ok, Chonburi 20110, Thailand
3
School of Chinese Pharmaceutical Sciences and Chinese Medicine Resources, China Medical University, Taichung 40402, Taiwan
4
Research Center of Animal Biologics, National Pingtung University of Science and Technology, Pingtung 91201, Taiwan
5
Center for Shockwave Medicine and Tissue Engineering, Department of Medical Research, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung 833, Taiwan
*
Authors to whom correspondence should be addressed.
Pathogens 2019, 8(3), 141; https://doi.org/10.3390/pathogens8030141
Received: 10 July 2019 / Revised: 29 August 2019 / Accepted: 3 September 2019 / Published: 7 September 2019
(This article belongs to the Special Issue Chicken Anaemia Virus Infection)
Chicken infectious anemia caused by chicken anemia virus (CAV) is a very important immunosuppressive disease in chickens. The horizontal spread of CAV in field chickens has been confirmed mainly through oral infection in our published article. Anemia is the main symptom of this disease. Studies by other scientists have shown that infection of CAV in 1-day-old chicks can cause anemia, and the degree of anemia is directly proportional to the dose of infectious virus. However, the pathogenesis of oral inoculation of CAV in older chickens is still not well understood. The purpose of this study was to determine whether 3-weeks-old specific-pathogen-free (SPF) chickens infected with different viral doses in oral route would cause anemia, as well as other signs associated with age-resistance. The experimental design was divided into a high-dose inoculated group (106 1050), low-dose inoculated group (103 TCID50), and non-virus inoculated control group, and 12 birds in each group at the beginning of the trial. The packed cell volumes (PCVs), CAV genome copies in tissues, CAV titer in peripheral blood fractions, and serology were evaluated at 7, 14, and 21 days post-infection (dpi). Virus replication and spread were estimated using quantitative polymerase chain reaction (qPCR) and viral titration in cell culture, respectively. The results showed that the average PCVs value of the high-dose inoculated group was significantly lower than that of the control group at 14 dpi (p < 0.05), and 44.4% (4/9) of the chickens reached the anemia level (PCVs < 27%). At 21 dpi, the average PCV value rebounded but remained lower than the control group without significant differences. In the low-dose inoculated group, all birds did not reach anemia during the entire trial period. Peripheral blood analysis showed that the virus titer in all erythrocyte, granulocyte and mononuclear cell reached the peak at 14 dpi regardless of the high-dose or low-dose inoculated group, and the highest virus titer appeared in the high-dose inoculated group of mononuclear cell. In the low-dose inoculated group, CAV was detected only at 14 dpi in erythrocyte. Taken together, our results indicate that the older birds require a higher dose of infectious CAV to cause anemia after about 14 days of infection, which is related to apoptosis caused by viral infection of erythrocytes. In both inoculated groups, the viral genome copies did not increase in the bone marrow, which indicated that minimal cell susceptibility to CAV was found in older chickens. In the low-dose inoculated group, only mononuclear cells can still be detected with CAV at 21 dpi in seropositive chickens, indicating that the mononuclear cell is the target cell for persistent infection. Therefore, complete elimination of the CAV may still require the aid of a cell-mediated immune response (CMI), although it has previously been reported to be inhibited by CAV infection. Prevention of early exposure to CAV could be possible by improved hygiene procedures. View Full-Text
Keywords: chicken anemia virus; viremia; anemia chicken anemia virus; viremia; anemia
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Tongkamsai, S.; Lee, M.-S.; Tsai, Y.-L.; Chung, H.-H.; Lai, G.-H.; Cheng, J.-H.; Cheng, M.-C.; Lien, Y.-Y. Oral Inoculation of Specific-Pathogen-Free Chickens with Chicken Anemia Virus Induces Dose-Dependent Viremia and Transient Anemia. Pathogens 2019, 8, 141.

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