High diversity of medically important gastrointestinal rodent-borne helminths in Singapore

Evolution and ecology of Jeilongvirus among wild rodents and shrews in Singapore

BACKGROUND

Jeilongvirus was proposed as a new genus within the Paramyxoviridae in 2018. The advancement in metagenomic approaches has encouraged multiple reports of Jeilongvirus detection following the initial species discovery, enriching species diversity and host range within the genus. However, Jeilongvirus remains understudied in Singapore, where interfaces between humans and small mammals are plentiful.

METHODS

Here, we utilized metagenomic sequencing for the exploration of viral diversity in small mammal tissues. Upon discovery of Jeilongvirus, molecular screening and full genome sequencing was conducted, with the data used to conduct statistical modelling and phylogenetic analysis.

RESULTS

We report the presence of Jeilongvirus in four species of Singapore wild small mammals, detected in their spleen and kidney. We show that full genomes of three Singapore Jeilongvirus encode for eight ORFs including the small hydrophobic and transmembrane proteins. All generated genomes cluster phylogenetically within the small mammal subclade, but share low genetic similarity with representative Jeilongvirus species. Statistical modelling showed no spatial or temporal patterns and differences among species, life history traits and habitat types.

CONCLUSIONS

This study serves as a basis for understanding dynamics between Jeilongvirus and small mammal hosts in Singapore by displaying the virus generalist nature. In addition, the initial detection can help to invoke improved routine surveillance and detection of circulating pathogens in synanthropic hosts.

Habitat impacts the abundance and network structure within tick (Acari: Ixodidae) communities on tropical small mammals

Ticks of small mammals pose a significant risk to public health but these hazards are poorly understood in the tropics due to the paucity of information on the disease ecology of ticks in these regions. Mapping and quantifying the diversity of small mammal/tick networks and the effects of habitat on these medically important systems is key to disease prevention. Singapore represents a microcosm of much of tropical Asia as it has a diverse, though poorly studied, community of ticks and small mammals. Singapore also has a range of terrestrial habitats exhibiting a gradient of degradation. Small mammals and their ticks were sampled across the island in four main habitat types (old secondary forest, young secondary forest, scrubland, urban) across 4.5 years. Four tick species were collected (Amblyomma helvolum, Dermacentor auratus, Haemaphysalis semermis, Ixodes granulatus) from 10 small mammal species. Habitat was found to have a significant effect on both the abundance and structure of tick communities on small mammals. Old secondary forest communities had the highest tick abundance, comparatively high connectance, niche overlap (among ticks), linkage density, and were the preferred habitat of the zoonotic tick I. granulatus. Therefore, future disease spillover is likely to emerge from small mammal-tick communities in old secondary forests.

Morphological and genetic description of Moniliformis necromysi sp. n. (Archiacanthocephala) from the wild rodent Necromys lasiurus (Cricetidae: Sigmondontinae) in Brazil

A new species of Moniliformis Travassos, 1915 (Acanthocephala: Moniliformidae) is described from the hairy-tailed bolo mouse, Necromys lasiurus Lund, 1840 (Cricetidae: Sigmondontinae), captured in the Brazilian Cerrado, in Uberlândia, state of Minas Gerais, Brazil. The specimens were studied by light and scanning electron microscopy. Molecular phylogenies were inferred from partial nuclear large subunit ribosomal RNA gene sequences and partial mitochondrial cytochrome c oxidase subunit I gene. The new species is distinguished from other moniliformid species by the number of rows and number of hooks per row, size of the proboscis, size of the eggs, host species and geographical distribution. Molecular phylogenies and genetic distances analyses demonstrated that Moniliformis necromysi sp. n. forms a well-supported monophyletic group with sequences of other species of Moniliformis and is distinguished from them, which agrees with the morphological characteristics, allocating the new species to this genus and to the family Moniliformidae Van Cleave, 1924. This is the first moniliformid acanthocephalan described from a wild rodent in Brazil.

First Report of Co-invasion by the Reptile Nematode Ozolaimus megatyphlon (Nematoda: Pharyngodonidae) with Invasive Green Iguanas (Iguana iguana) in the Asia-Pacific

PURPOSE

Co-invasion of naïve ecosystems by non-native parasites is a serious threat to global biodiversity, though such events are difficult to detect early in the invasion process. Green iguanas (Iguana iguana) are an emerging invasive species and have colonised several countries in the Asia-Pacific. A survey was undertaken to determine whether parasites of the green iguana had co-invaded naïve ecosystems with their introduced host.

METHODS

Over a 10-month period, wild green iguanas were trapped and euthanised in Singapore. All animals were necropsied and sampled for parasites. Parasites were then identified morphologically and subsequently characterised molecularly at the cytochrome c oxidase I (COI) locus.

RESULTS

The reptile nematode Ozolaimus megatyphlon was found in 38% of the sampled green iguanas, with burdens of 100 + worms in all infected animals. This represents the first recorded co-invasion of this species with wild green iguanas in the Asia-Pacific. Based on the molecular characterisation of the cytochrome c oxidase I (COI) locus, the first DNA barcode is provided for O. megatyphlon.

CONCLUSION

For the first time, the reptile nematode Ozolaimus megatyphlon is shown to be invasive and to have colonised the Asia-Pacific region with its introduced host, the green iguana. The DNA barcode provided here will facilitate future monitoring programmes as O. megatyphlon invades new habitats and countries.

New morphological and genetic data of Gigantorhynchus echinodiscus (Diesing, 1851) (Acanthocephala: Archiacanthocephala) in the giant anteater Myrmecophaga tridactyla Linnaeus, 1758 (Pilosa: Myrmecophagidae)

Gigantorhynchus echinodiscus (Diesing, 1851) is a parasite of anteaters in South America. Although described by Diesing in 1851, there is still a lack of taxonomic and phylogenetic information regarding this species. In the present study, we redescribe G. echinodiscus collected from a giant anteater, Myrmecophaga tridactyla Linnaeus, 1758, from the Brazilian Cerrado (Savannah) in the State of São Paulo by light and scanning electron microscopy. In addition, phylogenies were inferred from partial DNA gene sequence of the nuclear large subunit ribosomal RNA gene (28S rRNA). We provide for the first time details of the proboscis with a crown having 18 large hooks and numerous small hooks, a lateral papilla at the base of the proboscis, a ringed pseudo-segmented body, large testes, cemented glands in pairs, and a non-segmented region in the posterior end of the body, which contributed to the diagnosis of the species. Molecular phylogenetic analyses recovered G. echinodiscus forming a well-supported monophyletic group with Mediorhynchus sp., which was congruent with morphological studies that allocate both genera within the family Gigantorhynchidae. In conclusion, the present work adds new morphological and molecular information, emphasizing the importance of adopting integrative taxonomic approaches in studies of Acanthocephala.

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Redescription of Gigantorhynchus echinodischus from Brazilian giant anteater.

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First molecular data of the genus Gigantorhynchus with 28S rRNA partial gene.

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Phylogenetic relationships of Gigantorhynchidae are assessed.