Pathogenicity and transmissibility studies on live attenuated duck enteritis virus vaccine in non-target species

FIGURE 1. Replicative capacity of live attenuated duck enteritis virus (DEV) vaccine to chicken embryos in vivo. (A) Pathogenicity and gross damage of live attenuated DEV vaccine in chicken embryos. (B) Virus replication of live attenuated DEV vaccine in chicken embryos. SPF-chicken embryos, 1-day-old, were randomly divided into four groups, and each group covers ten chicken embryos. From left to right being challenged with DEV AV1221 (105.42 TCID50), 1 dose of vaccine (103.00 ELD50), and 10 dose of vaccine (104.00 ELD50), at the same dose in 100 μL, respectively. The results are representative of two tests. ****P < 0.0001.

FIGURE 2. Diagram of animal regression experiments. (A) Ducks were randomly divided into four groups of twenty ducks. A quarter of ducks were infected with corresponding DEV AV1221 at a dose of 105.42 TCID50 in 0.1ml volume. A quarter of ducks were used as negative controls. The rest of the ducks was equally divided into two groups, half ducks were immunized with live attenuated DEV vaccine of 104.00 ELD50 in 0.1 ml volume, and the other half of ducks were immunized with the same vaccine of 105.00 ELD50 in 0.1 ml volume. SPF chickens were contacted with the challenged ducks in the same isolator, respectively. (B) Chickens were randomly divided into four groups of twenty chickens. A quarter of chickens were infected with corresponding DEV AV1221 at a dose of 105.42 TCID50 in 0.1ml volume. A quarter of chickens were used as negative controls. The rest of the chickens were equally divided into two groups, half chickens were immunized with live attenuated DEV vaccine of 104.00 ELD50 in 0.1 ml volume, and the other half of chickens were immunized with the same vaccine of 105.00 ELD50 in 0.1 ml volume. SPF chickens were directly challenged.

FIGURE 3. Live attenuated duck enteritis virus (DEV) vaccine in targeted ducks retains in vivo growth kinetics activity. (A) Gross lesions of target ducks. (B) The hematoxylin- and eosin (H&E)-stained tissue section in target ducks. From left to right are liver, heart, spleen, glandular stomach, liver, kidney, and intestine. (C) The survival curve of target ducks. (D) DEV effectively replicates in different tissue of target ducks. Data are representative of four experiments related to challenge. **P < 0.01, ***P < 0.001, and ****P < 0.0001.

FIGURE 4. Live attenuated duck enteritis virus (DEV) vaccine replicated in non-target chickens and resulted in effectively virus transmission. (A) Pathogenic lesions of non-target chickens. (B) The hematoxylin- and eosin (H&E)-stained tissue section in non-target chickens. From left to right are liver, heart, spleen, glandular stomach, liver, kidney, and intestine. (C) The survival curve of non-target chickens. (D) DEV effectively replicates in different tissue of non-target chickens. Data are representative of four experiments related to challenge. **P < 0.01, ***P < 0.001, and ****P < 0.0001.

FIGURE 5. Duck enteritis virus (DEV) replicated and resulted in effectively virus shedding. During the target ducks-to-non-target chicken transmission, the virions shed in sink, soil, and feed trough may persist for long periods in the environment. Virus titer was expressed as lg(copies/μl). ***P < 0.001, ****P < 0.0001.

FIGURE 6. Both duck enteritis virus (DEV) and Live attenuated DEV vaccine replicated directly in targeted chickens and resulted in tissue damage. (A) Serious lesions of target chickens. (B) The hematoxylin- and eosin (H&E)-stained tissue section in target chickens. From left to right are liver, heart, spleen, glandular stomach, liver, kidney, and intestine. (C) The survival curve of target chickens. (D) DEV effectively replicates in different tissue of target chickens. Data are representative of four experiments related to challenge. **P < 0.01, ***P < 0.001, ****P < 0.0001.