Melophagus ovinus (sheep ked) is a hematophagous ectoparasite that mainly parasitizes sheep. In addition to causing inflammation, wool loss, and skin damage to the animal hosts, M. ovinus also serves as a vector for a variety of pathogens and is highly likely to participate in the life and transmission cycle of pathogenic organisms. Herein, we investigated the presence and molecular characterization of vector-borne pathogens in M. ovinus from Qinghai-Tibet Plateau, China. A total of 92 M. ovinus pools collected from the Qinghai province of China were screened for the presence of selected vector-borne pathogens. The overall positive rate of A. ovis, A. bovis, A. phagocytophilum, and T. ovis in M. ovinus was 39.1%, 17.4%, 9.8%, and 89.1%, respectively. All of the samples were negative for Border disease virus (BDV), other Anaplasma species, Babesia spp., Rickettsia spp., and Borrelia spp. Co-infection of different Anaplasma species and T. ovis occurred in 51.2% of all samples with T. ovis. The positive rates of A. ovis, A. bovis, and A. phagocytophilum in different regions and altitudes of the sampling sites were significantly different. Sequence and phylogenetic analysis of target genes confirmed their identity with corresponding pathogens. Our results elucidate the occurrence and molecular characterization of Anaplasma spp. and Theileria spp. in M. ovinus, which could act as potential zoonotic reservoirs. To the best of our knowledge, this is the first report of the detection of A. bovis and A. phagocytophilum DNA in M. ovinus. This study gives the first extensive molecular survey of vector-borne pathogens with veterinary and public health significance in M. ovinus from the Qinghai-Tibet Plateau, China.

The impact of lactoferrin, an antimicrobial peptide (AMP) with iron-binding properties, on the intestinal barrier and microflora of mice infected with highly pathogenic avian influenza A (H5N1) virus remains unclear. To investigate the effects of lactoferrin on the histopathology and intestinal microecological environment, we conducted a study using H5N1-infected mice. H5N1 infection resulted in pulmonary and intestinal damage, as well as an imbalance in gut microbiota, significantly increasing the abundance of pathogenic bacteria such as Helicobacter pylori and Campylobacter. The consumption of lactoferrin in the diet alleviated lung injury and restored the downregulation of the INAVA gene and intestinal dysfunction caused by H5N1 infection. Lactoferrin not only reduced lung and intestinal injury, but also alleviated inflammation and reversed the changes in intestinal microflora composition while increasing the abundance of beneficial bacteria. Moreover, lactoferrin rebalanced the gut microbiota and partially restored intestinal homeostasis. This study demonstrated that lactoferrin exerts its effects on the intestinal tract, leading to improvements in gut microbiota and restoration of the integrity of both the intestinal wall and lung tissue. These findings support the notion that lactoferrin may be a promising candidate for systemic treatment of influenza by locally acting on the intestine and microbiota.

Cryptosporidium spp., Blastocystis, Giardia duodenalis, Balantioides coli, Pentatrichomonas hominis, and Enterocytozoon bieneusi are enteric protozoan parasites and fungal species in humans and animals. Père David’s deer is an endangered species in China, but the prevalence of enteric protozoans in this species still needs to be further studied. Thus, we investigated the prevalence and genetic diversity of zoonotic parasites in Père David’s deer during the period of 2018–2021. Among the 286 fecal samples collected from Père David’s deer in the Nanhaizi Nature Reserve, 83 (29.0%) were positive for Blastocystis, 70 (24.5%) were positive for E. bieneusi, while other protozoan parasites were negative. Based on a phylogenetic analysis, three Blastocystis subtypes (ST10, ST14, and ST21) and ten E. bieneusi genotypes (Genotype D, MWC_d1, HLJD-V, Peru6, BEB6, BJED-I to BJED-I V) were identified. In addition, the Blastocystis subtype ST14 and the E. bieneusi genotype D and Peru6 were first detected in Père David’s deer. Our study first reports the presence of two enteric protozoans in Père David’s deer during a 4-year active surveillance and provides more information about zoonotic subtypes/genotypes of Blastocystis and E. bieneusi in deer.

Trichomonas gallinae (T. gallinae) is an infectious parasite that is prevalent worldwide in poultry and can cause death in both poultry and wild birds. Although studies have shown that T. gallinae damages host cells through direct contact, the mechanism is still unclear. In this study, we found that T. gallinae can kill host cells by ingesting fragments of the host cells, that is, by trogocytosis. Moreover, we found that the PI3K inhibitor wortmannin and the cysteine protease inhibitor E-64D prevented T. gallinae from destroying host cells. To the best of our knowledge, our study has demonstrated for the first time that T. gallinae uses trogocytosis to kill host cells. Understanding this mechanism is crucial for the prevention and control of avian trichomoniasis and will contribute to the development of vaccines and drugs for the prevention and control of avian trichomoniasis.

The abundance and prevalence of parasitic infection often vary in different host sexes, and this phenomenon has been named sex-biased parasitism. Brandt’s voles are the dominant rodent species in typical steppe habitat and are widely distributed in Inner Mongolia, China, but the prevalence of parasites in Brandt’s voles are poorly reported. In this study, we investigated the prevalence of six intestinal parasites in Brandt’s voles in May, June, July, and August 2022 around the Xilingol Grassland in Inner Mongolia, China. The results showed that Syphacia obvelata, Aspiculuris tetraptera, and Trichostrongylidae family were the dominant intestinal parasites in Brandt’s voles that we captured in this study, and the infection rates of the three parasites were significantly higher in males than females, which showed obvious male-biased parasitism. Season and human activities such as grazing had no significant effect on the infection rates for different parasites, while the parasite reproduction level was higher when the ambient temperature was around 18 °C. Sexual size dimorphism was ubiquitous in Brandt’s voles, and it was mainly manifested by the differences in body weight and length between males and females. Simple linear regression analysis showed a significant positive correlation between bodyweight and parasite infection rates, so the sex-biased parasitism in Brandt’s voles could be explained by the body size hypothesis, as a larger body could provide more ecological niches for parasitic infection.

In October 2021, a wild bird-origin H3N8 influenza virus-A/Chinese pond heron/Jiangxi 5-1/2021 (H3N8)-was isolated from Chinese pond heron in China. Phylogenetic and molecular analyses were performed to characterize the genetic origin of the H3N8 strain. Phylogenetic analysis revealed that eight gene segments of this avian influenza virus H3N8 belong to Eurasian lineages. HA gene clustered with avian influenza viruses is circulating in poultry in southern China. The NA gene possibly originated from wild ducks in South Korea and has the highest homology (99.3%) with A/Wild duck/South Korea/KNU2020-104/2020 (H3N8), while other internal genes have a complex and wide range of origins. The HA cleavage site is PEKQTR↓GLF with one basic amino acid, Q226 and T228 at HA preferentially bind to the alpha-2,3-linked sialic acid receptor, non-deletion of the stalk region in the NA gene and no mutations at E627K and D701N of the PB2 protein, indicating that isolate A/Chinese pond heron/Jiangxi 5-1/2021 (H3N8) was a typical avian influenza with low pathogenicity. However, there are some mutations that may increase pathogenicity and transmission in mammals, such as N30D, T215A of M1 protein, and P42S of NS1 protein. In animal studies, A/Chinese pond heron/Jiangxi 5-1/2021 (H3N8) replicates inefficiently in the mouse lung and does not adapt well to the mammalian host. Overall, A/Chinese pond heron/Jiangxi 5-1/2021 (H3N8) is a novel wild bird-origin H3N8 influenza virus reassortant from influenza viruses of poultry and wild birds. This wild bird-origin avian influenza virus is associated with wild birds along the East Asian-Australasian flyway. Therefore, surveillance of avian influenza viruses in wild birds should be strengthened to assess their mutation and pandemic risk in advance.