Isolation, molecular characterization, and phylogenetic analysis of encephalomyocarditis virus from South China tigers in China

Developmental stage variation in the gut microbiome of South China tigers

South China tigers (Panthera tigris amoyensis, SC) are the most threatened tiger subspecies in the world. All the living SCs are captive in zoos or reserves and depend on artificial feeding. The composition of the gut microbiome plays an important role in sustaining the health of the host. A comprehensive understanding of the composition and development of the microbial community of SC is helpful to improve the feeding of captive SC. In this study, we collected 47 fecal samples, 37 of which were from SC of three developmental stages, 5 from adult Amur tigers (Am), and 5 from adult Bengal tigers (Bg), which were all housed in the same zoo. We investigated the diversity, richness, and composition of the bacterial microbiomes and we found that the gut microbiome of SC is strongly affected by host aging. The composition of the gut microbiome of juvenile SC experienced dramatic changes from 5 months old to 1 year old, and it showed much less difference when compared to the samples of 1 year old and the subadult. No significant differences were observed between the samples of subadult and the adult groups. The predominant phylum of 5-month-old SC is Fusobacteriota (33.99%) when the juvenile tigers were older than 5 months, and Firmicutes, but not Fusobacteriota, became the predominant phylum of bacteria in their gut. The gut microbiome of SC, Am, and Bg is possibly affected by their genetic variation; however, the core microbiome of these three subspecies is the same. Our data suggest that the gut microbiome of SC undergoes a developmental progression: a developmental phase (cub), a transitional phase (subadult), and a stable phase (adult). These results expand our understanding of the role of age in the development of the gut microbiome of SC.

Rapid detection of porcine encephalomyocarditis virus (EMCV) by isothermal reverse transcription recombinase polymerase amplification assays

In this study, we combined reverse transcription recombinase polymerase amplification assay with the fluorescence detection platform (qRT-RPA) and lateral flow biosensor (LFB RT-RPA) to allow for rapid detection of porcine encephalomyocarditis virus (EMCV). Primers and probes were designed to target the highly conserved region of 3D gene of porcine EMCV. The optimal reaction condition of qRT-RPA and LFB RT-RPA was set as 42 °C for 20 min. The assays were highly specific to EMCV and no cross-reactions were observed with seven other porcine viruses. With a 10-fold serially diluted EMCV genomic RNA as template, the limit of detection was 1.0 × 10² and 1.0 × 10¹ copies for qRT-RPA assay and LFB RT-RPA assay, respectively. A total of 92 samples from different sources were examined using qRT-RPA, LFB RT-RPA and qRT-PCR. We found 100% diagnostic agreement between qRT-RPA (23/92) and qRT-PCR (23/92), and 97.83% diagnostic agreement between LFB RT-RPA (25/92) and qRT-PCR (23/92). There was no significant difference in performance between the RT-RPA assays developed in this study and a previously described qRT-PCR. However, RT-RPA assays were rapid and easy to perform while LFB RT-RPA exhibited higher sensitivity for EMCV than qRT-PCR. Therefore, the developed EMCV RT-RPA assays provide an attractive and promising tool for effective detection of EMCV in low-resource settings.

Detection and molecular characterisation of intestinal parasites in the South China tiger Panthera tigris amoyensis (Hilzheimer)

Parasitic infections of the South China tigers in the Meihua Mountains have not been explored previously. Faeces of 22 South China tigers from the China Tiger Park in the Meihua Mountains were examined. Eggs of ascaridoid nematodes and oocysts of coccidia were detected by Mini-FLOTAC assay. Morphological observation and molecular characterisation of the oocysts were carried out. The prevalence of Toxascaris leonina (von Linstow, 1902) was 18% (4/22), and the highest egg per gram (EPG) count in the faeces was 27,150. The prevalence of Cystoisospora sp. was 45% (1 0/22) and the highest oocysts per gram (OPG) in the faeces was 6,000. In addition, we found one ascaridoid nematode in the South China tiger's faeces and was molecularly and morphologically identified as T. leonina. The oocysts in the faeces were sporulated in vitro and identified as Cystoisospora sp. Amplification of full-length internal transcribed spacers (ITS) resulted in sequences 1,622 bp long. Using the sequences, Cystoisospora sp. of the South China tiger was closest to Isospora belli (Wenyon, 1923) and Cystoisospora suis (Biester, 1934).

Identification and molecular analysis of Ixodid ticks (Acari: Ixodidae) infesting wild boars (Sus scrofa) and tick-borne pathogens at the Meihua mountain of southwestern Fujian, China

Wildlife is essential to the biodiversity of the Meihua mountain, southwestern Fujian province, China. However, there have been few surveys of the distribution of ixodid ticks (Acari: Ixodidae) and tick-borne pathogens affecting wild animals at these locations. In this study, 1197 adult ixodid ticks infesting wild boars were collected from 10 sampling sites during 2019. Ticks were identified to species based on morphology, and the identification was confirmed based on mitochondrial 16S, ITS1 and ITS2 rRNA sequences. Eight tick species belonging to 2 genera were identified, including H. longicornis (n = 373, 31.1%), H. flava (n = 265, 22.1%), D. auratus (n = 153, 12.8%), H. hystricis (n = 119, 9.9%), D. silvarum (n = 116, 9.7%), H. bispinosa (n = 114, 9.5%), D. atrosignatus (n = 33, 2.8%), and D. taiwanensis (n = 24, 2.0%). DNA sequences of Rickettsia spp. (spotted fever group) and Babesia spp. were detected in these ticks. Phylogenetic analyses revealed the possible existence of Candidatus Rickettsia laoensis and Rickettsia raoultii. This study illustrates the potential threat to wild animals and humans from tick-borne pathogens.

Construction and characterization of an infectious cDNA clone of encephalomyocarditis virus from pigs in China

Encephalomyocarditis virus (EMCV) infects animals of various species and causes a variety of clinical symptoms. In this study, an infectious full-length cDNA clone was constructed, and the characteristics of the rescued virus were investigated in vitro and in vivo. Our data demonstrated that the growth kinetics in vitro and plaque morphology of the rescued EMCV rNJ08 strain were similar to those of the parental strain. Although rNJ08 infected BALB/c mice, none of the mice died during the observation period of 14 days post-inoculation. The availability of the infectious cDNA clone provides a genetic platform for studying gene function and for the rational design of vaccines.