Protective efficacy of Lactobacillus plantarum BS22 against Eimeria tenella and Eimeria acervulina co-infection in broiler chickens.

Avian coccidiosis, caused by Eimeria spp., is a major constraint on global poultry production, and mixed-species infections-particularly Eimeria tenella and Eimeria acervulina-are common and more pathogenic in the broiler breeding. Rising concerns over anticoccidial drug resistance and residues have stimulated interest in probiotics as alternative or complementary control strategies. This study evaluated the protective efficacy of Lactobacillus plantarum BS22 (LP-BS22), a chicken-derived strain with confirmed in vitro antimicrobial activity and stability, against this clinically prevalent mixed infection. Seventy-two broiler chickens were randomly assigned to four groups: uninfected control (CG), probiotic control (LP-BS22), co-infected model (DIG), and probiotic-treated co-infected group (LP-BS22+DIG). Efficacy was assessed via growth performance, oocyst output, lesion scoring, and histopathology. To elucidate the underlying mechanism, the expressions of intestinal tight junction (TJ)-related zonula occluden-1 (ZO-1) and claudin 5 (CLDN5) proteins as well as pro-inflammatory (interleukin [IL]-6) and regulatory (IL-10 and IL-22) cytokines were also quantified. The results demonstrated that prophylactic administration of LP-BS22 significantly mitigated growth retardation, reduced fecal oocyst shedding, and lowered intestinal lesion scores compared to the untreated DIG group (P < 0.05). Histologically, the probiotic treatment alleviated intestinal villus atrophy and crypt hyperplasia. Mechanistically, LP-BS22 preserved intestinal barrier integrity by preventing the downregulation of ZO-1 and CLDN5; furthermore, the probiotic modulated the immune response by suppressing pro-inflammatory IL-6 while upregulating regulatory IL-10 and the tissue-repair cytokine IL-22 (P < 0.05). The calculated anticoccidial index (ACI) ranged from 126.76 to 133.46, classifying the efficacy as moderate. These findings indicated that LP-BS22 conferred protection against mixed Eimeria infections by enhancing mucosal barrier function and regulating inflammation, positioning it as a promising sustainable strategy for coccidiosis control in broiler production.