Background: Chicken anemia virus (CAV) causes chicken infectious anemia, which results in immunosuppression; the virus has spread widely in chicken flocks in China. Objectives: The aim of this study was to understand recent CAV genetic evolution in chicken flocks in Guangxi Province, southern China. Methods: In total, 350 liver samples were collected from eight commercial broiler chicken farms in Guangxi Province in southern China from 2018 to 2020. CAV was detected by conventional PCR, and twenty CAV complete genomes were amplified and used for the phylogenetic analysis and recombination analysis. Results: The overall CAV-positive rate was 17.1%. The genetic analysis revealed that 84 CAVs were distributed in groups A, B, C (subgroups C1-C3) and D. In total, 30 of 47 Chinese CAV sequences from 2005-2020 belong to subgroup C3, including 15 CAVs from this study. There were some specific mutation sites among the intergenotypes in the VP1 protein. The amino acids at position 394Q in the VP1 protein of 20 CAV strains were consistent with the characteristics of a highly pathogenic strain. GX1904B was a putative recombinant. Conclusions Subgroup C3 was the dominant genotype in Guangxi Province from 2018–2020.The 20 CAV strains in this study might be virulent according to the amino acid residue analysis. These data help improve our understanding of the epidemiological trends of CAV in southern China.

Objective:To evaluate the intestinal function in rats with exertional heat stroke (EHS) and explore the protective role of Ruifuping pectin (RFP) against heat related intestinal mucosal injury.Methods:One hundred and twenty healthy special pathogen free (SPF) male Sprague-Dawley (SD) rats were randomly divided into normothermic control group, EHS model group, hyperthermic plus drinking water group (H 2O+EHS group) and hyperthermic plus pectin group (RFP+EHS group) with 30 rats in each group. The rats in the H 2O+EHS group and RFP+EHS group were given water 20 mL/kg or RFP 20 mL/kg orally for 5 days during adaptive training period. After 1 week, the temperature control range was adjusted to (37±1)℃ using the temperature control treadmill, and the rat model of EHS was reproduced by one-time high temperature exhaustive exercise. No rehydration intervention was given during the training adaptation period in the EHS model group. The rats in the normothermic control group were maintained to room temperature (25±2)℃ and humidity (55±5)% without other treatment. Behavior tests including withdraw response, righting, and muscle strength were performed immediately after onset of EHS. Blood of inferior vena cava was collected, and the serum inflammatory cytokines [tumor necrosis factor-α (TNF-α) and interleukins (IL-6, IL-1β, IL-10)] and activity of diamine oxidase (DAO) were detected by enzyme linked immunosorbent assay (ELISA). The intestinal mucosa was collected, after hematoxylin-eosin (HE) staining, and Chiu score was performed to assess EHS induced pathological changes under light microscope. Results:The rats in the EHS model group had behavioral, inflammatory and pathological changes, such as delayed withdraw response and righting, decreased forelimb pulling, increased inflammatory index, and obvious intestinal mucosal injury, which indicated that the reproduction of the EHS model was successful. There was no significant difference in above parameters between the H 2O+EHS group and the EHS model group except that the inflammatory index in the RFP+EHS group was improved. Compared with the EHS model group, the withdraw reflex to pain and righting after RFP pretreatment in the RFP+EHS group were significantly improved (righting score: 1.4±0.2 vs. 0.3±0.2, withdraw reflex to pain score: 1.0±0.1 vs. 0.2±0.1, both P < 0.05), the muscle strength was significantly increased (N: 13.0±0.5 vs. 8.2±0.6, P < 0.01). The levels of pro-inflammatory factors in the RFP+EHS group were significantly lower than those in the EHS model group [TNF-α (ng/L): 67.5±9.2 vs. 194.3±13.7, IL-6 (ng/L): 360.0±54.1 vs. 981.2±84.4, IL-1β (ng/L): 33.7±9.0 vs. 88.7±6.1, all P < 0.01], while the level of anti-inflammatory factor IL-10 was higher than that in the EHS model group (ng/L: 208.7±10.5 vs. 103.7±7.0, P < 0.01). The degree of intestinal mucosal injury in the RFP+EHS group was less severe than that in the EHS model group, and the Chiu score and DAO were significantly lower than those in the EHS model group [Chiu score: 1.5±0.2 vs. 3.8±0.0, DAO (U/L): 83.7±6.7 vs. 128.7±10.5, both P < 0.05]. Conclusions:High temperature training can damage the intestinal barrier function, and induce endotoxemia and systemic inflammatory response syndrome (SIRS) in rats. Oral prophylactic RFP can protect the intestinal barrier function, alleviate SIRS, and promote the recovery of basic nerve reflex and muscle strength after the occurrence of EHS in rats.