Absence of genetic structure in Baylisascaris schroederi populations, a giant panda parasite, determined by mitochondrial sequencing

Using Blood Transcriptome Analysis to Determine the Changes in Immunity and Metabolism of Giant Pandas with Age

A low reproductive rate coupled with human activities has endangered the giant panda, a species endemic to southwest China. Although giant pandas feed almost exclusively on bamboo, they retain carnivorous traits and suffer from carnivorous diseases. Additionally, their immune system is susceptible to aging, resulting in a reduced ability to respond to diseases. This study aimed to determine the genes and pathways expressed differentially with age in blood tissues. The differentially expressed genes in different age groups of giant pandas were identified by RNA-seq. The elderly giant pandas had many differentially expressed genes compared with the young group (3 years old), including 548 upregulated genes and 401 downregulated genes. Further, functional enrichment revealed that innate immune upregulation and adaptive immune downregulation were observed in the elderly giant pandas compared with the young giant pandas. Meanwhile, the immune genes in the elderly giant pandas changed considerably, including genes involved in innate immunity and adaptive immunity such as PLSCR1, CLEC7A, CCL5, CCR9, and EPAS1. Time series analysis found that giant pandas store glycogen by prioritizing fat metabolism at age 11, verifying changes in the immune system. The results reported in this study will provide a foundation for further research on disease prevention and the energy metabolism of giant pandas.

Genomic Signatures of Coevolution between Nonmodel Mammals and Parasitic Roundworms

Antagonistic coevolution between host and parasite drives species evolution. However, most of the studies only focus on parasitism adaptation and do not explore the coevolution mechanisms from the perspective of both host and parasite. Here, through the de novo sequencing and assembly of the genomes of giant panda roundworm, red panda roundworm, and lion roundworm parasitic on tiger, we investigated the genomic mechanisms of coevolution between nonmodel mammals and their parasitic roundworms and those of roundworm parasitism in general. The genome-wide phylogeny revealed that these parasitic roundworms have not phylogenetically coevolved with their hosts. The CTSZ and prolyl 4-hydroxylase subunit beta (P4HB) immunoregulatory proteins played a central role in protein interaction between mammals and parasitic roundworms. The gene tree comparison identified that seven pairs of interactive proteins had consistent phylogenetic topology, suggesting their coevolution during host–parasite interaction. These coevolutionary proteins were particularly relevant to immune response. In addition, we found that the roundworms of both pandas exhibited higher proportions of metallopeptidase genes, and some positively selected genes were highly related to their larvae’s fast development. Our findings provide novel insights into the genetic mechanisms of coevolution between nonmodel mammals and parasites and offer the valuable genomic resources for scientific ascariasis prevention in both pandas.

High genetic diversity of Giardia duodenalis assemblage E in Chinese dairy cattle

Giardia duodenalis is a common protozoan parasite that can infect humans and animals. Although previous studies demonstrated that the assemblage E of G. duodenalis is prevalent in cattle, studies on its genetic diversity were mostly based on single loci and very few involved multilocus analysis. To better understand the genetic variability and structure of G. duodenalis assemblage E in Chinese dairy cattle, 651 multilocus sequences derived from nine provinces (Gansu, Guangdong, Henan, Jiangsu, Ningxia, Shaanxi, Shanghai, Sichuan and Xinjiang) of China were analyzed in this study. Results showed that a total of 220 haplotypes were identified in the G. duodenalis assemblage E, with a high haplotype diversity (Hd = 0.97225) and low nucleotide diversity (π = 0.00259). The genetic differentiation index (FST) and gene flow (Nm) results indicated low degree of genetic differentiation, implying frequent genetic communication. Combined with the analysis of molecular variance (AMOVA), genetic variation within populations (81.7%) was higher than that among populations (18.3%), indicating low degree of genetic differentiation between populations. Such low rates of gene differentiation supported no significant correlations with geographical divisions. Moreover, both negative Tajima's D and Fu's FS values of neutrality tests and unimodal curve of mismatch distribution analyses indicated that G. duodenalis assemblage E population in Chinese dairy cattle had experienced demographic expansion. Overall, these findings contribute to an improved understanding of the population genetics and evolutionary biology of G. duodenalis assemblage E and assist in its control in cattle.

Review on parasites of wild and captive giant pandas (Ailuropoda melanoleuca): Diversity, disease and conservation impact

The giant panda (Ailuropoda melanoleuca) is a rare species with a small global population size, and lives in the wild in only a few fragmented mountain ranges of Southwest China. Parasitic infections are among the important causes of death of giant pandas that hamper their group development. We reviewed the parasitic infections prevailing in giant pandas, and the parasitic diversity, diseases and their impact on conservation of this animal. A total of 35 parasitic species were documented in giant pandas, belonging to nematode (n = 6), trematode (n = 1), cestode (n = 2), protozoa (n = 9), and ectozoa (n = 17 (tick = 13, mite = 2, and flea = 2)). Among them, Baylisascaris schroederi had the highest prevalence and was the leading cause of death for giant pandas. Some parasites caused asymptomatic infections in giant pandas, and their health implications for the pandas remain unknown. As a whole, parasites are reported to be an important threat to the conservation of the giant pandas. Regular deworming and environmental disinfection appear to be effective ways to prevent captive giant pandas from parasitoses. In wild panda populations, parasitic control measures are suggested to include detailed examination of the ecology of the host-parasite assembly, with particular attention to density-dependent transmission. The parasitic pathogenesis and detection methods together with their biology, epidemiology, treatment, prevention and control need to be further studied for better protection of giant pandas from parasitoses.

Transcriptome analysis reveals immune-related gene expression changes with age in giant panda (Ailuropoda melanoleuca) blood

The giant panda (Ailuropoda melanoleuca), an endangered species endemic to western China, has long been threatened with extinction that is exacerbated by highly contagious and fatal diseases. Aging is the most well-defined risk factor for diseases and is associated with a decline in immune function leading to increased susceptibility to infection and reduced response to vaccination. Therefore, this study aimed to determine which genes and pathways show differential expression with age in blood tissues. We obtained 210 differentially expressed genes by RNA-seq, including 146 up-regulated and 64 down-regulated genes in old pandas (18-21yrs) compared to young pandas (2-6yrs). We identified ISG15, STAT1, IRF7 and DDX58 as the hub genes in the protein-protein interaction network. All of these genes were up-regulated with age and played important roles in response to pathogen invasion. Functional enrichment analysis indicated that up-regulated genes were mainly involved in innate immune response, while the down-regulated genes were mainly related to B cell activation. These may suggest that the innate immunity is relatively well preserved to compensate for the decline in the adaptive immune function. In conclusion, our findings will provide a foundation for future studies on the molecular mechanisms underlying immune changes associated with ageing.

The population genetics of parasitic nematodes of wild animals

Parasitic nematodes are highly diverse and common, infecting virtually all animal species, and the importance of their roles in natural ecosystems is increasingly becoming apparent. How genes flow within and among populations of these parasites - their population genetics - has profound implications for the epidemiology of host infection and disease, and for the response of parasite populations to selection pressures. The population genetics of nematode parasites of wild animals may have consequences for host conservation, or influence the risk of zoonotic disease. Host movement has long been recognised as an important determinant of parasitic nematode population genetic structure, and recent research has also highlighted the importance of nematode life histories, environmental conditions, and other aspects of host ecology. Commonly, factors influencing parasitic nematode population genetics have been studied in isolation, such that an integrated view of the drivers of population genetic structure of parasitic nematodes is still lacking. Here, we seek to provide a comprehensive, broad, and integrative picture of these factors in parasitic nematodes of wild animals that will be a useful resource for investigators studying non-model parasitic nematodes in natural ecosystems. Increasingly, new methods of analysing the population genetics of nematodes are becoming available, and we consider the opportunities that these afford in resolving hitherto inaccessible questions of the population genetics of these important animals.

Parasites of the Giant Panda: A Risk Factor in the Conservation of a Species

The giant panda, with an estimated population size of 2239 in the world (in 2015), is a global symbol of wildlife conservation that is threatened by habitat loss, poor reproduction and limited resistance to some infectious diseases. Of these factors, some diseases caused by parasites are considered as the foremost threat to its conservation. However, there is surprisingly little published information on the parasites of the giant panda, most of which has been disseminated in the Chinese literature. Herein, we review all peer-reviewed publications (in English or Chinese language) and governmental documents for information on parasites of the giant pandas, with an emphasis on the intestinal nematode Baylisascaris schroederi (McIntosh, 1939) as it dominates published literature. The purpose of this chapter is to: (i) review the parasites recorded in the giant panda and describe what is known about their biology; (ii) discuss key aspects of the pathogenesis, diagnosis, treatment and control of key parasites that are reported to cause clinical problems and (iii) conclude by making some suggestions for future research. This chapter shows that we are only just 'scratching the surface' when it comes to parasites and parasitological research of the giant panda. Clearly, there needs to be a concerted research effort to support the conservation of this iconic species.

Beyond the raccoon roundworm: The natural history of non-raccoon Baylisascaris species in the New World

A total of 10 species of Baylisascaris, a genus of ascaridoid nematodes, occur worldwide and 6 of them occur in the New World. Most of the Baylisascaris species have a similar life cycle with carnivorous mammals or marsupials serving as definitive hosts and a smaller prey host serving as paratenic (or intermediate) hosts. However, one species in rodents is unique in that it only has one host. Considerable research has been conducted on B. procyonis, the raccoon roundworm, as it is a well-known cause of severe to fatal neurologic disease in humans and many wildlife species. However, other Baylisascaris species could cause larva migrans but research on them is limited in comparison. In addition to concerns related to the potential impacts of larva migrans on potential paratenic hosts, there are many questions about the geographic ranges, definitive and paratenic host diversity, and general ecology of these non-raccoon Baylisascaris species. Here, we provide a comprehensive review of the current knowledge of New World Baylisascaris species, including B. columnaris of skunks, B. transfuga and B. venezuelensis of bears, B. laevis of sciurids, B. devosi of gulonids, B. melis of badgers, and B. potosis of kinkajou. Discussed are what is known regarding the morphology, host range, geographic distribution, ecoepidemiology, infection dynamics in definitive and paratenic hosts, treatment, and control of these under-studied species. Also, we discuss the currently used molecular tools used to investigate this group of parasites. Because of morphologic similarities among larval stages of sympatric Baylisascaris species, these molecular tools should provide critical insight into these poorly-understood areas, especially paratenic and definitive host diversity and the possible risk these parasites pose to the health to the former group. This, paired with traditional experimental infections, morphological analysis, and field surveys will lead to a greater understanding of this interesting and important nematode genus.

Fatty-binding protein and galectin of Baylisascaris schroederi: Prokaryotic expression and preliminary evaluation of serodiagnostic potential

Baylisascaris schroederi is a common parasite of captive giant pandas. The diagnosis of this ascariasis is normally carried out by a sedimentation-floatation method or PCR to detect eggs in feces, but neither method is suitable for early diagnosis. Fatty acid-binding protein (FABP) and galectin (GAL) exist in various animals and participate in important biology of parasites. Because of their good immunogenicity, they are seen as potential antigens for the diagnosis of parasitic diseases. In this study, we cloned and expressed recombinant FABP and GAL from B. schroederi (rBs-FABP and rBs-GAL) and developed indirect enzyme-linked immunosorbent assays (ELISAs) to evaluate their potential for diagnosing ascariasis in giant pandas. Immunolocalization showed that Bs-FABP and Bs-GAL were widely distributed in adult worms. The ELISA based on rBs-FABP showed sensitivity of 95.8% (23/24) and specificity of 100% (12/12), and that based on rBs-GAL had sensitivity of 91.7% (22/24) and specificity of 100% (12/12).

Absence of population genetic structure in Heterakis gallinarum of chicken from Sichuan, inferred from mitochondrial cytochrome c oxidase subunit I gene

Population genetics information provides a foundation for understanding the transmission and epidemiology of parasite and, therefore, may be used to assist in the control of parasitosis. However, limited available sequence information in Heterakis gallinarum has greatly impeded the study in this area. In this study, we first investigated the genetic variability and genetic structure of H. gallinarum. The 1325 bp fragments of the mitochondrial COX1 gene were amplified in 56 isolates of H. gallinarum from seven different geographical regions in Sichuan province, China. The 56 sequences were classified into 22 haplotypes (H1-H22). The values of haplotype diversity (0.712) and nucleotide diversity (0.00158) in Sichuan population indicate a rapid expansion occurred from a relatively small, short-term effective population in the past. The haplotype network formed a distribution around H1 in a star-like topology, and the haplotypes did not cluster according to their geographical location. Similar conclusions could be made from MP phylogenetic tree. The Fst value (Fst<0.16965) and AMOVA analysis revealed that no significant genetic differentiation was observed among the seven different geographical populations. Neutrality tests (Tajima's D and Fu's Fs) and mismatch analysis indicated that H. gallinarum experienced a population expansion in the past. Our results indicated that H. gallinarum experienced a rapid population expansion in the past, and there was a low genetic diversity and an absence of population structure across the population.