Abstract:

The object of this study was to understand the pathogenicity, virus shedding and horizontal transmission ability of chicken infectious anemia virus (CAV) on SPF chickens. In this study, 1-day-old and 28-day-old SPF chickens were infected with CAV JL17/1204 strain by intraperitoneal inoculation and cohabitation. At 3 days post infection (dpi), 5 dpi, 7 dpi, 9 dpi, 11 dpi, 14 dpi, 21 dpi, 28 dpi, 42 dpi, 56 dpi, 84 dpi and 112 dpi, the anticoagulant blood of 3 chickens in each group was collected and the thymus was dissected to detect anemia and thymus atrophy. Throat swabs and anal swabs of 20 chickens in each group were collected at each time point to detect the virus shedding by PCR method. The clinical observation results showed that the mortality rates of 1-day-old infected chickens and cohabiting infected chickens were 50.0% and 10.0%, respectively, and the death occurred at 12-15 dpi; 28-day-old infected and cohabiting infected chickens did not die. The results of autopsy showed that the thymus atrophy and/or anemia symptoms appeared in the diseased chickens of each group. The incidence rate of the 1-day-old infected chickens and the cohabiting infected chickens were 100.0% and 20.0%, respectively; The incidence of 28-day-old infected chickens and cohabiting infected chickens were 10.0% and 8.0%, respectively. The virus shedding results showed that the respiratory tract and digestive tracts of the 1-day-old infected chickens began to shed from 3 dpi and 5 dpi, respectively. The detoxification period of the respiratory and digestive tracts of the 1-day-old cohabiting infected chickens were 5-84 days and 7-42 days after cohabitation, respectively; The respiratory and digestive virus shedding periods in the 28-day-old infected chickens were 3-9 dpi and 5-14 dpi, respectively; The respiratory and digestive virus shedding periods in the 28-day-old cohabiting infected chickens were 5-9 days and 5-42 days after cohabitation, respectively. The results showed that CAV was highly pathogenic to 1-day-old SPF chickens, and could cause high mortality, thymus atrophy and/or anemia after infection, but its pathogenicity was obviously weakened to 28-day-old SPF chickens. Infected chickens excrete virus through respiratory tract and digestive tract, and the excreted virus can infect cohabiting chickens to get sick or even die, which indicates that CAV has high horizontal transmission ability. The results of this study systematically expounded the pathogenic characteristics and virus shedding of CAV infection, which provided theoretical guidance and scientific basis for the scientific purification of CAV in chickens.

Key words: chicken infectious anemia virus, SPF chickens, pathogenicity, shedding virus, horizontal transmission