New record of the Oriental house rat, Rattus tanezumi, in Nepal inferred from mitochondrial Cytochrome B gene sequences

The complete mitochondrial genome and phylogenetic analysis of Rattus tanezumi (Niethammer, 1975), captured from North China

Rattus tanezumi (Niethammer, 1975) is one of the commensal rodent species in South China. With the development of transportation and climate change, R. tanezumi has gradually migrated north and become the dominant rat species for the past few years. In this study, we assembled a complete mitochondrial genome of R. tanezumi, captured from North China. The mitogenome contains 16,307 nucleotide pairs, including 13 protein-coding genes, 2 ribosomal RNA genes, and 22 transfer RNA genes, as well as one non-coding control region. Based on whole mitogenome phylogenetical analysis showed that R. tanezumi captured from North China had a close phylogenetic relationship with that from Japan and South Korea. These findings are valuable for further studies on the evolution, genetic diversity, and taxonomy of Asian commensal rodent.

Region-Specific Genetic Diversity of Black Rats (Rattus rattus Complex) in Southeast and East Asia Shaped by Rapid Population Expansion Events

Among the six mitochondrial DNA lineages of the black rat (Rattus rattus Complex; RrC), lineages II and IV are widespread in Southeast and East Asia. This study explored their demographic history using 17 new sequences from the Miyako Islands in the Ryukyu archipelago, together with 178 publicly available cytochrome b sequences. We defined six and two haplotype groups showing rapid population expansion signals in Lineages II and IV, respectively. The six haplotype groups of Lineage II were represented by haplotypes from 1) Myanmar/Bangladesh/Northeast India, 2) Laos, 3) Thailand, 4) Indonesia/Philippines, 5) Vietnam/southern China, and 6) the Ryukyu archipelago. These expansion times were estimated using time-dependent evolutionary rates to be 115,300 years ago (ya), 128,500 ya, 9600 ya, 10,600 ya, 7200 ya, and 1400 ya, respectively, although all had large confidence intervals. The two groups of Lineage IV were recovered from the mainland and islands of Southeast Asia with predicted expansion times of 197,000 ya and 5800 ya, respectively. These results suggest that climatic fluctuations during the last 200,000 years of the Quaternary, affected the population dynamics in subtropical areas at different times. Furthermore, the results of the younger rapid expansion events of RrC suggest the possibility of agricultural advancement and dispersal of Neolithic farmers to different areas within the mainland and islands of Southeast Asia during the Holocene. A subset of rats from the Miyako Islands were found to have the same lineage IV haplotypes as those in Southeast Asia, suggesting a recent introduction of these new lineages.

An Overview of Angiostrongylus cantonensis (Nematoda: Angiostrongylidae), an Emerging Cause of Human Angiostrongylosis on the Indian Subcontinent

Human angiostrongylosis is an emerging zoonosis caused by the larvae of three species of metastrongyloid nematodes of the genus Angiostrongylus, with Angiostrongylus cantonensis (Chen, 1935) being dominant across the world. Its obligatory heteroxenous life cycle includes rats as definitive hosts, mollusks as intermediate hosts, and amphibians and reptiles as paratenic hosts. In humans, the infection manifests as Angiostrongylus eosinophilic meningitis (AEM) or ocular form. Since there is no comprehensive study on the disease in the Indian subcontinent, our study aims at the growing incidence of angiostrongylosis in humans, alongside its clinical course and possible causes. A systematic literature search revealed 28 reports of 45 human cases from 1966 to 2022; eosinophilic meningitis accounted for 33 cases (75.5%), 12 cases were reported as ocular, 1 case was combined, and 1 case was unspecified. The presumed source of infection was reported in 5 cases only. Importantly, 22 AEM patients reported a history of eating raw monitor lizard (Varanus spp.) tissues in the past. As apex predators, monitor lizards accumulate high numbers of L3 responsible for acute illness in humans. For ocular cases, the source was not identified. Most cases were diagnosed based on nematode findings and clinical pathology (primarily eosinophilia in the cerebrospinal fluid). Only two cases were confirmed to be A. cantonensis, one by immunoblot and the other by q-PCR. Cases of angiostrongylosis have been reported in Delhi, Karnataka, Kerala, Maharashtra, Madhya Pradesh, Puducherry, Telangana, and West Bengal. With a population of more than 1.4 billion, India is one of the least studied areas for A. cantonensis. It is likely that many cases remain undetected/unreported. Since most cases have been reported from the state of Kerala, further research may focus on this region. Gastropods, amphibians, and reptiles are commonly consumed in India; however, typical preparation methods involve cooking, which kills the nematode larvae. In addition to studying rodent and mollusk hosts, monitor lizards can be used as effective sentinels. Sequence data are urgently needed to answer the question of the identity of Angiostrongylus-like metastrongylid nematodes isolated from all types of hosts. DNA-based diagnostic methods such as q-PCR and LAMP should be included in clinical diagnosis of suspected cases and in studies of genetic diversity and species identity of nematodes tentatively identified as A. cantonensis.

Molecular Evidence Reveals the Sympatric Distribution of Cervus nippon yakushimae and Cervus nippon taiouanus on Jeju Island, South Korea

Non-native species threaten native ecosystems and species, particularly on islands where rates of endemism and vulnerability to threats are high. Understanding species invasion will aid in providing insights into ecological and evolutionary processes. To identify the non-native sika deer (Cervus nippon) population in Jeju, South Korea, and their phylogenetic affinities, we collected tissue samples from roadkill and the World Natural Heritage Headquarters in Jeju. Mitochondrial DNA cytochrome B (CytB) gene sequences were analyzed to determine two distinct CytB haplotypes. Phylogenetic analysis using maximum likelihood tree revealed two haplotypes of CytB clustered into two different groups representing two subspecies: C. n. yakushimae, native to Japan, and C. n. taiouanus, native to Taiwan. The tentative divergence time between the two subspecies was estimated at 1.81 million years. Our study confirmed that the two subspecies of sika deer are sympatric in the natural ecosystem of Jeju Island. This study provides valuable information to help government and conservation agencies understand alien species and determine control policies for conserving native biodiversity in South Korea.