Bartonella is an intracellular parasitic zoonotic pathogen that can infect animals and cause a variety of human diseases. This study investigates Bartonella prevalence in small mammals in Yunnan Province, China, focusing on tissue tropism. A total of 333 small mammals were sampled from thirteen species, three orders, four families, and four genera in Heqing and Gongshan Counties. Conventional PCR and real-time quantitative PCR (qPCR) were utilized for detection and quantification, followed by bioinformatic analysis of obtained DNA sequences. Results show a 31.5% detection rate, varying across species. Notably, Apodemus chevrieri, Eothenomys eleusis, Niviventer fulvescens, Rattus tanezumi, Episoriculus leucops, Anourosorex squamipes, and Ochotona Thibetana exhibited infection rates of 44.4%, 27.7%, 100.0%, 6.3%, 60.0%, 23.5%, and 22.2%, respectively. Genetic analysis identified thirty, ten, and five strains based on ssrA, rpoB, and gltA genes, with nucleotide identities ranging from 92.1% to 100.0%. Bartonella strains were assigned to B. grahamii, B. rochalimae, B. sendai, B. koshimizu, B. phoceensis, B. taylorii, and a new species identified in Episoriculus leucops (GS136). Analysis of the different tissues naturally infected by Bartonella species revealed varied copy numbers across different tissues, with the highest load in spleen tissue. These findings underscore Bartonella’s diverse species and host range in Yunnan Province, highlighting the presence of extensive tissue tropism in Bartonella species naturally infecting small mammalian tissues.

The genetic diversity of coronaviruses (CoVs) is high, and their infection in animals has not yet been fully revealed. By RT-PCR detection of the partial RNA-dependent RNA polymerase (RdRp) gene of CoVs, we screened a total of 502 small mammals in the Dali and Nujiang prefectures of Western Yunnan Province, China. The number of overall CoV positives was 20, including β-CoV (n = 13) and α-CoV (n = 7), with a 3.98% prevalence in rectal tissue samples. The identity of the partial RdRp genes obtained for 13 strains of β-CoV was 83.42–99.23% at the nucleotide level, and it is worth noting that the two strains from Kachin red-backed voles showed high identity to BOV-36/IND/2015 from Indian bovines and DcCoV-HKU23 from dromedary camels (Camelus dromedarius) in Morocco; the nucleotide identity was between 97.86 and 98.33%. Similarly, the identity of the seven strains of α-CoV among the partial RdRp sequences was 94.00–99.18% at nucleotide levels. The viral load in different tissues was measured by quantitative RT-PCR (qRT-PCR). The average CoV viral load in small mammalian rectal tissue was 1.35 × 10⁶ copies/g; differently, the mean CoV viral load in liver, heart, lung, spleen, and kidney tissue was from 0.97 × 10³ to 3.95 × 10³ copies/g, which revealed that CoV has extensive tropism in rectal tissue in small mammals (p < 0.0001). These results revealed the genetic diversity, epidemiology, and infective tropism of α-CoV and β-CoV in small mammals from Dali and Nujiang, which deepens the comprehension of the retention and infection of coronavirus in natural hosts.

Rat hepatitis E virus (rat HEV, Rocahepevirus genotype C1) represents a potential zoonotic threat, but its epidemiological and evolutionary characteristics in small mammals remain poorly understood, especially in regions with complex geography. Between 2022 and 2024, we collected 818 small mammals from seven border counties and cities in Yunnan, China. Rat HEV RNA was detected by RT-PCR, risk factors were assessed using binary logistic regression, and full genomes were sequenced for phylogenetic and molecular clock analysis. The overall prevalence of rat HEV was 6.23% (51/818), with significantly higher odds observed in Gengma and Heqing counties, in oriental house rat (Rattus tanezumi) and Chevrieri’s field mouse (Apodemus chevrieri), in residential habitats, and at mid-high altitudes (all p < 0.001). The 51 partial genomic sequences (RdRp gene) obtained in this study clustered within Rocahepevirus, forming two distinct subclades associated with host species. The two complete genomes, GS188 and GS197 from Rattus tanezumi, were classified as subtypes C1b and C1d, respectively. Bayesian analysis estimated that GS197 diverged from a closely related Rattus tanezumi-derived strain around 1998, while GS188 diverged from a lineage containing shrew and human strains around 1931. These findings reveal a relatively high prevalence and substantial genetic diversity of Rochepevirus in southwestern Yunnan, suggesting human-influenced transmission dynamics and a potential for cross-species infection.

The genetic diversity of coronavirus (CoV) is high, and its infection in animals has not yet been fully revealed. By RT-PCR detection of partial RNA dependent RNA polymerase (RdRp) gene of CoV, we screened a total of 502 small mammals belonging to 18 species in 12 genera and 4 orders collected in Dali and Nujiang Prefecture of Western Yunnan Province, China. The prevalence of β-CoV in Chevrieri's field mouse (Apodemus chevrieri) and Lancangjiang field mouse (A. ilex) were 3.54% (4/113) and 6.67% (6/90), respectively; the prevalence of α-CoV in White-footed Indochinese rat (Rattus nitidus) and long-tailed red-toothed shrew (Episoriculus leucops) was 75% (3/4) and 5.88% (1/17), respectively. The co-infection rates of β-CoV and α-CoV in Kachin red-backed vole (Eothenomys cachinus), Norway rat (R. norvegicus) were 2.22% (2/90), 3.85% (1/26) respectively. The identity of the partial RdRp genes obtained of 13 strains of β-CoV was 83.42%-99.23% at nucleotide level, and it is worth noting that the two strains from Kachin red-backed vole showed highly homology to BOV-36/IND/2015 from Indian bovine and DcCoV-HKU23 from one-humped camel (Camelus dromedarius) in Morocco, the nucleotide similarity between 97.86%-98.33%. Similarly, the identity of the 7 strains of α-CoV among the partial RdRp sequences was 94.00%-99.18% at nucleotide levels. The viral load in different tissues was measured by quantitative RT-PCR (qRT-PCR). The average CoV viral load in small mammalian intestinal tissue was 1.25×106copies/g, differently, the mean CoV viral load in liver, heart, lung, spleen and kidney tissue was from 1.29×103 to 4.02×103copies/g, which revealed that CoV has extensive tropism of intestinal tissue in small mammals (P < 0.0001). This result revealed the genetic diversity, epidemiology, and infective tropism of α-CoV and β-CoV in small mammals from Dali and Nujiang, which deepens the comprehending of the retention and infection of coronavirus in natural hosts.

Bartonella species, intracellular parasitic zoonotic pathogens, has drawn increasing attention for their diverse host range and associated human diseases. This study investigates Bartonella infection in small mammals in Yunnan Province, China, focusing on tissue tropism. 333 small mammals were sampled from 13 species, 3 orders, 4 families, and 4 genera in Heqing and Gongshan Counties. Conventional PCR and real-time quantitative PCR (qPCR) were utilized for detection and quantification, followed by bioinformatic analysis of obtained DNA sequences. Results show a 31.5% detection rate, varying across species. Notably, Apodemus chevrieri, Eothenomys eleusis, Niviventer fulvescens, Rattus tanezumi, Episoriculus leucops, Anourosorex squamipes, and Ochotona Thibetana exhibited infection rates of 44.4%, 27.7%, 100.0%, 6.3%, 60.0%, 23.5%, and 22.2%, respectively. Genetic analysis identified 30, 10, and 5 strains based on ssrA, rpoB, and gltA genes, with nucleotide identities ranging from 92.1% to 100.0%. Bartonella strains were assigned to B. grahamii, B. rochalimae, B. sendai, B. koshimizu, B. phoceensis, B. taylorii, and a new species identified in the Episoriculus leucops (GS136). Tissue distribution analysis revealed varied copy numbers across different tissues, with the highest load in spleen. These findings underscore Bartonella's diverse species and host range in Yunnan Province, highlighting its broad tissue tropism in small mammals.

Black-headed gulls have been confirmed as the natural hosts of Deltacoronavirus (δ-CoV) and Gammacoronavirus (γ-CoV). A total of 59 CoV-PCR-positive fecal samples were identified among 509 fecal samples collected from overwintering black-headed gulls in Yunnan Province, China. The prevalence of black-headed gull deltacoronavirus (BHG-DCoV) was 3.54% (18/509), while that of black-headed gull gammacoronavirus (BHG-GCoV) was 8.06% (41/509). The prevalence of BHG-GCoV was significantly higher than that of BHG-DCoV (χ² = 9.518, p < 0.01). Two complete genome sequences of BHG-GCoVs were obtained, with lengths of 27,358 bp and 27,355 bp, respectively, from the fecal samples of black-headed gulls. The nucleotide similarity between the two complete genomes is 98.75%. Phylogenetic analysis based on the whole genome has confirmed that the two strains of BHG-GCoVs clustered into the species Gammacoronavirus anatis. Although BHG-GCoVs belong to the species Gammacoronavirus anatis, they are distantly related to the representative strain Duck_CoV 2714 and exhibit a closer genetic relationship with GCoVs from Xenus cinereus (AvXc-GCoV) and Numenius phaeopus (AvNp-GCoV). Similarity analysis of the five conserved domains revealed a high amino acid similarity not only with AvXc-GCoV and AvNp-GCoV but also with GCoVs from common gulls detected in Poland and those from ruddy turnstones identified in Australia. Additionally, we found that, except for the common gull, the amino acid sequences of the S protein of BHG-GCoVs showed a 88.69% to 96.44% similarity with those of GCoVs carried by Charadriiformes, while the similarity with GCoVs carried by Anseriformes ranged from 31.15% to 54.81%. Furthermore, recombination events were detected in BHG-GCoVs, suggesting that these strains are likely recombinant strains of common gull GCoV and the GCoV of Arenaria interpres (AvAi-GCoV), indicating that recombination events may occur frequently among GCoVs.