Background: Eimeria coccidiosis is a significant intestinal parasitic disease, which can lead to weight loss, disease and even death of many animals. At present, there is no information about the prevalence of Eimeria among the world’s endangered species of Père David’s deer (Elaphurus davidianus). Therefore, the purpose of this study is to identify an unknown Eimeria genus in the Père David’s deer in Dafeng Milu National Nature Reserve, China. Results: A new Eimeria species is described from Père David’s deer. Sporulated oocysts (n = 54) are pyriform, with a rough, yellowish brown, 2-layered oocyst wall (2.5 μm thick). A numerous small granules are dispersed randomly on the wall. Oocysts measured 41.2 (39.2–42.8) μm × 29.5 (27.9–30.5) μm, oocyst length/width (L/W) ratio, 1.4. Oocyst residuum, a polar granule and a polar cap are absent. The micropyle (3.5 μm wide) is present. Sporocysts are spindle shaped, 18.2 (16.5–20.0) μm × 10.5 (9.8–11.9) μm, sporocyst L/W ratio, 1.7 (1.5–1.9). A thin convex Stieda body is present and the sporocyst residuum is composed of numerous small granules less than 2.0 μm in diameter dispersed randomly. Each sporocyst contained 2 comma-shaped sporozoites in head-to-tail arrangement. A nucleus is located immediately anterior to the posterior, strong refractive and subspherical refractile body (~ 8 μm). Molecular analysis was conducted at the 18S, ITS-1 and COI loci. Conclusion: Based on the morphological and molecular data, this isolate is a new species of coccidian parasite, which is named Eimeria davidianusi after its host, the Père David’s deer (Elaphurus davidianus).

The burden of gastrointestinal parasites in zoo animals has serious implications for their welfare and the health of veterinarians and visitors. Zhuyuwan Zoo is located in the eastern suburb of Yangzhou city in eastern China, in which over 40 species of zoo animals are kept. In order to understand the infection status of GI parasites in Zhuyuwan Zoo, a total of 104 fresh fecal samples collected randomly from birds (n = 19), primates (n = 19), and non-primate mammals (n = 66) were analyzed using the saturated saline flotation technique and nylon sifter elutriation and sieving method for eggs/oocysts, respectively. Two Ascaris species were molecularly characterized. The results showed that the overall prevalence of parasitic infection was 42.3% (44/104). The parasitic infection rate in birds, primates, and non-primate mammals were 26.3% (5/19), 31.6% (6/19), and 50.0% (33/66), respectively. A total of 11 species of parasites were identified, namely, Trichostrongylidae, Capillaria sp., Trichuris spp., Strongyloides spp., Amidostomum sp., Toxascaris leonina, Baylisascaris transfuga, Parascaris equorum, Paramphistomum spp., Fasciola spp., and Eimeria spp. Paramphistomum spp. eggs were first detected from the captive Père David’s deer, and Fasciola spp. eggs were first reported from sika deer in zoo in China. A sequence analysis of ITS-2 and cox1 showed that the eggs isolated from the African lion (Panthera leo Linnaeus, 1758) were T. leonina, and the eggs from the brown bear (Ursus arctos Linnaeus, 1758) were B. transfuga. The public health threat posed by these potential zoonotic parasitic agents requires attention. These results lay a theoretical foundation for prevention and control of wild animal parasitic diseases at zoos in China.

Background: Eimeria necatrix , a member of the Apicomplexa phylum, is one of the most pathogenic parasites, causing high mortality in chickens. Microneme proteins (MICs) play essential roles in host cell recognition and invasion by apicomplexan parasites and are also attractive candidates for vaccine development. However, comprehensive studies on E. necatrix MICs remain limited. Methods: Eimeria necatrix MIC3 gene (En MIC3 ) was amplified and expressed in Escherichia coli . The recombinant protein (rEnMIC3) was characterized via SDS-PAGE and Western blot. The antigenicity of rEnMIC3 and its localization in sporozoites (SZ) and second-generation merozoites (MZ-2) of E. necatrix were determined by Western blot and indirect immunofluorescence analyses (IFAs). The dynamic expression of EnMIC3 across different developmental stages and its impact on sporozoite invasion of host cells were analyzed. The immune protection provided by rEnMIC3 was evaluated in chickens using weight gain, lesion scores, oocyst production, anticoccidial index (ACI), and antibody levels. Results: The open reading frame of En MIC3 was 798 bp, encoding a 265-amino acid protein with a predicted molecular weight of 28.50 kDa. EnMIC3 contained a signal peptide and a single epidermal growth factor (EGF)-like domain. The rEnMIC3 with an approximate molecular weight of 36 kDa could be specifically recognized by convalescent sera from chickens infected with E. necatrix . The molecular mass of the native protein was approximately 35 kDa, and it localizes to the apical region in SZ but exhibits a cytoplasmic distribution in MZ-2. EnMIC3 mRNA was expressed at significantly higher levels in SZ than in MZ-2, whereas protein expression displayed an inverse pattern. Anti-rEnMIC3 polyclonal antibodies inhibited sporozoite invasion of DF-1 cells in a dose-dependent manner. Vaccination with rEnMIC3 conferred effective protection against E. necatrix challenge, with the high-dose group (200 µg) achieving the highest ACI value (171.32) and markedly elevated serum antibody levels. Conclusions: These findings not only offer a foundation for understanding the role of EnMIC3 protein in the host invasion of E. necatrix but also present a potential protective antigen of E. necatrix for the development of a subunit vaccine against avian coccidiosis.

Limosilactobacillus reuteri is one of the common lactic acid bacteria in the chicken gastrointestinal tract. Our previous study revealed that L. reuteri abundance declined in White Leghorn chickens following infection with Eimeria tenella, E. maxima, and E. necatrix, suggesting a potential role of this species in gut homeostasis during coccidiosis. In this study, eight L. reuteri strains were isolated from the intestinal tract of White Leghorn chickens. Strain S3 was selected as the most promising candidate after screening for acid and bile tolerance, adhesion ability, antagonism against pathogens. Oral administration of S3 strain at dose of 4 × 10⁷ CFU/bird, 1.2 × 10⁸ CFU/bird or 2 × 10⁸ CFU/bird for 18 days improved average daily gain (ADG) in both White Leghorn chickens and Suqin laying hens. The ADG value in groups treated with 4 × 10⁷ CFU/bird was significantly higher compared to that in the control group (p < 0.05). This treatment did not cause adverse effects on hepatic or renal function, but significantly increased the thymus index in both breeds and the levels of total protein and globulin in Suqin laying hens (p < 0.05). S3 strain also modulated gut microbiota composition in White Leghorn chickens, promoting beneficial lactobacilli colonization in the jejunum and achieving persistent colonization in the cecum. S3 strain selectively increased the proportion of CD3⁺CD4⁺ T lymphocytes in peripheral blood of Suqin laying hens. The anticoccidial efficacy of S3 strain was evaluated in Suqin laying hens challenged with E. tenella, E. maxima, and E. necatrix. The results showed that S3 strain alleviated clinical signs, reduced lesion scores, decreased oocyst output, and attenuated body weight loss. Anticoccidial index (ACI) values were 130.67, 148.06, and 163.40 for E. tenella, E. maxima, and E. necatrix infection, respectively. These results suggest that L. reuteri S3 is a safe chicken-derived probiotic with immunomodulatory and anticoccidial properties, and may serve as a feed additive for coccidiosis control in poultry production.