RESUMO
To determine whether fruit bats in Singapore have been exposed to filoviruses, we screened 409 serum samples from bats of 3 species by using a multiplex assay that detects antibodies against filoviruses. Positive samples reacted with glycoproteins from Bundibugyo, Ebola, and Sudan viruses, indicating filovirus circulation among bats in Southeast Asia.
Assuntos
Quirópteros/sangue , Quirópteros/virologia , Ebolavirus , Marburgvirus , Proteínas do Envelope Viral/sangue , Animais , Glicoproteínas/sangue , Glicoproteínas/genética , Glicoproteínas/isolamento & purificação , Estudos Soroepidemiológicos , Singapura/epidemiologiaRESUMO
BACKGROUND: Astroviruses are comprised of two genera with Avastrovirus infecting birds and Mamastrovirus infecting mammals. Avastroviruses have primarily been associated with infections of poultry, especially chicken, turkey, duck, and guineafowl production systems, but also infect wading birds and doves. Outcomes result in a spectrum of disease, ranging from asymptomatic shedding to gastroenteritis with diarrhea, stunting, failure to thrive and death. FINDINGS: Virological surveillance was conducted in birds from two sites in Cambodia in 2010. Samples were screened for influenza, astroviruses, coronaviruses, flaviviruses, and paramyxoviruses. A total of 199 birds were tested and an astrovirus was detected in a black-naped monarch (Hypothymis azurea). CONCLUSIONS: This is the first astrovirus detection in a passerine bird. Phylogenetic analysis and nucleotide distances suggest that this avastrovirus forms a distinct lineage and may constitute a fourth avastrovirus group.
Assuntos
Infecções por Astroviridae/veterinária , Avastrovirus/classificação , Avastrovirus/isolamento & purificação , Doenças das Aves/virologia , Passeriformes/virologia , Animais , Infecções por Astroviridae/virologia , Camboja , Análise por Conglomerados , Dados de Sequência Molecular , Filogenia , Reação em Cadeia da Polimerase , RNA Viral/genética , Análise de Sequência de DNA , Homologia de SequênciaRESUMO
Bats and ticks are important sources of zoonotic pathogens. Therefore, understanding the diversity, distribution, and ecology of both groups is crucial for public health preparedness. Soft ticks (Argasidae) are a major group of ectoparasites commonly associated with bats. The multi-host life cycle of many argasids make them important vectors of pathogens. Over nine years (2011-2020), surveillance was undertaken to identify the ticks associated with common bats in Singapore. During this period, the bat tick Ornithodoros batuensis was detected within populations of two cave roosting bat species: Eonycteris spelaea and Penthetor lucasi. We examined the relationship between bat species, roosting behaviour, and probability of O. batuensis infestation. We also estimated the relationship between bat life history variables (body condition index, sex, and age) on the probability of infestation and tick count. This represents the first detection of O. batuensis and the genus Ornithodoros within Singapore. We also provide evidence of the continued persistence of Argas pusillus in Singapore with the second local record.
Assuntos
Quirópteros , Ornithodoros , Infestações por Carrapato , Animais , Quirópteros/parasitologia , Singapura/epidemiologia , Feminino , Masculino , Infestações por Carrapato/veterinária , Infestações por Carrapato/epidemiologia , Infestações por Carrapato/parasitologia , Argasidae , ArgasRESUMO
Orthonairovirus is a genus of viruses in the family Nairoviridae, order Bunyavirales, with a segmented circular RNA genome. They typically infect birds and mammals and are primarily transmitted by ectoparasites such as ticks. Four of nine Orthonairovirus genogroups can infect humans, with Crimean-Congo hemorrhagic fever virus infections displaying case fatality rates up to 40%. Here, we discover and describe a novel Orthonairovirus as Cencurut virus (CENV). CENV was detected in 34 of 37 Asian house shrews (Suncus murinus) sampled in Singapore and in a nymphal Amblyomma helvolum tick collected from an infected shrew. Pairwise comparison of CENV S, M, and L segments had 95.0 to 100% nucleotide and 97.5 to 100% amino acid homology within CENV genomes, suggesting a diverse viral population. Phylogenetic analysis of the individual gene segments showed that CENV is related to Erve, Lamgora, Lamusara, and Thiafora viruses, with only 49.0 to 58.2% nucleotide and 41.7 to 61.1% amino acid homology, which has previously been detected in other shrew species from France, Gabon, and Senegal respectively. The high detection frequency suggests that CENV is endemic among S. murinus populations in Singapore. The discovery of CENV, from a virus family with known zoonotic potential, underlines the importance of surveillance of synanthropic small mammals that are widely distributed across Southeast Asia.
RESUMO
The Asian rodent tick (Ixodes granulatus) occurs throughout much of Asia, it frequently bites humans, and zoonotic pathogens, such as Borrelia burgdorferi (sensu lato) and Rickettsia honei, have been detected within it. Unfortunately, the ecology of I. granulatus remains poorly known, including drivers of its abundance and the interaction ecology with its sylvatic hosts. To elucidate the ecology of this medically important species, the habitat preferences of I. granulatus were assessed in Singapore and Malaysia. Ixodes granulatus showed strong associations with old forest habitats, though across different age classes of old forest there was limited variation in abundance. Ixodes granulatus was absent from other habitats including young forest, scrubland, and parks/gardens. Within its sylvatic rodent hosts, a range of factors were found to be statistically significant predictors of I. granulatus load and/or infestation risk, including sex and body condition index. Male rodents were significantly more likely to be infested and to have higher loads than females, similarly, animals with a lower body condition index were significantly more likely to be infested. Proactive public health efforts targeted at preventing bites by this tick should carefully consider its ecology to minimise ecological overlap between humans and I. granulatus.
Assuntos
Ixodes , Ixodidae , Humanos , Animais , Feminino , Masculino , Ixodes/microbiologia , Roedores , Estações do Ano , Ecossistema , MalásiaRESUMO
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.
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Bats are known natural reservoirs of several highly pathogenic zoonotic viruses, including Hendra virus, Nipah virus, rabies virus, SARS-like coronaviruses, and suspected ancestral reservoirs of SARS-CoV-2 responsible for the ongoing COVID-19 pandemic. The capacity to survive infections of highly pathogenic agents without severe disease, together with many other unique features, makes bats an ideal animal model for studying the regulation of infection, cancer, and longevity, which is likely to translate into human health outcomes. A key factor that limits bat research is lack of breeding bat colonies. To address this need, a captive bat colony was established in Singapore from 19 wild-caught local cave nectar bats. The bats were screened for specific pathogens before the start of captive breeding. Custom-made cages and an optimized diet inclusive of Wombaroo dietary formula, liquid diet, and supplement of fruits enabled the bats to breed prolifically in our facility. Cages are washed daily and disinfected once every fortnight. Bats are observed daily to detect any sick bat or abnormal behavior. In addition, bats undergo a thorough health check once every 3 to 4 mo to check on their overall wellbeing, perform sampling, and document any potential pregnancy. The current colony houses over 80 bats that are successfully breeding, providing a valuable resource for research in Singapore and overseas.
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COVID-19 , Quirópteros , Animais , Cruzamento , Reservatórios de Doenças , Humanos , Pandemias , Filogenia , Néctar de Plantas , SARS-CoV-2 , SingapuraRESUMO
Astroviruses are a genetically diverse group of viruses that infect a wide range of hosts, including small mammals. Small mammals were trapped at 19 sites across Singapore from November 2011 to May 2014. Pooled oropharyngeal and rectal swabs (n = 518) and large intestine tissue (n = 107) were screened using a PCR to detect the presence of Astrovirus RNA-dependent RNA polymerase (RdRp) gene. Astroviruses were detected in 93 of 625 (14.9%) of samples tested, with eight of 11 species of rats, shrews, and squirrels testing positive. This is the first detection of astroviruses in seven species (Callosciurus notatus, Mus castaneus, Rattus tanezumi, Rattus tiomanicus, Sundamys annandalei, Suncus murinus and Tupaia glis). Phylogenetic analysis of 10 RdRp gene sequences revealed that astroviruses from Singapore small mammals fall in three distinct clades, one that is specific to the common treeshrew (Tupaia glis), and two comprised of multiple species. One of these includes viruses from the cave nectar bat (Eonycteris spelaea), two rodent species, and a squirrel, suggesting that virus spillover from bats to small mammals may have occurred. Our results show an increased host range for astroviruses and highlight their potential for intra- and inter-species transmission.
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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.
Assuntos
Ixodidae/fisiologia , Doenças dos Roedores/epidemiologia , Roedores , Musaranhos , Infestações por Carrapato/veterinária , Tupaiidae , Animais , Ecossistema , Dinâmica Populacional , Doenças dos Roedores/parasitologia , Singapura/epidemiologia , Infestações por Carrapato/epidemiologia , Infestações por Carrapato/parasitologiaRESUMO
Haemosporidians infect a wide diversity of bat genera and species, yet little is known about their transmission cycles or epidemiology. Though several recent studies have focused on the genus Hepatocystis, an Old World parasite primarily infecting bats, monkeys, and squirrels, this group is still understudied with little known about its transmission and molecular ecology. These parasites lack an asexual erythrocytic stage, making them unique from the Plasmodium vertebrate life cycle. In this study, we detected a prevalence of 31% of Hepatocystis in short-nosed fruit bats (Cynopterus brachyotis) in Singapore. Phylogenetic reconstruction with a partial cytochrome b sequence revealed a monophyletic group of Hepatocystis from C. brachyotis in Malaysia, Singapore, and Thailand. There was no relationship with infection and bat age, sex, location, body condition or monsoon season. The absence of this parasite in the five other bat species sampled in Singapore indicates this Hepatocystis species may be host restricted.
RESUMO
Bat flies are highly-specialized, hematophagous arthropods that are globally ubiquitous. There is little published research on bat flies (Diptera: Nycteribiidae) in Singapore and understanding the diversity of nycteribiids, host association and infestation rates can provide insight into this host-ectoparasite relationship. Nycteribiids were collected from bats trapped in Singapore (2011-2016) and identified using morphological keys. Host-ectoparasite relationships were investigated with logistic regression and Bayesian poisson regression. Nycteribiids were found to be monoxenously associated with their host bat species and host age, sex, species, and BBCI appear to contribute to differences in prevalence and intensity. Differences in host specificity between bat fly species in Singapore and their conspecifics in less disturbed habitats with higher bat biodiversity, such as Malaysia, Philippines and Thailand, suggest that the high host specificity in Singapore derives from the paucity of suitable hosts and abundance of single species roosts and not from their coevolved restrictions to them.
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Bats are unique mammals that are reservoirs of high levels of virus diversity. Although several of these viruses are zoonotic, the majority are not. Astroviruses, transmitted fecal-orally, are commonly detected in a wide diversity of bat species, are prevalent at high rates and are not thought to directly infect humans. These features make astroviruses useful in examining virus evolutionary history, epidemiology in the host, and temporal shedding trends. Our study screened for the presence of astroviruses in bats in Singapore, reconstructed the phylogenetic relations of the polymerase genes and tested for population characteristics associated with infection. Of the seven species screened, astroviruses were detected in Rhinolophus lepidus and Eonycteris spelaea. The R. lepidus sequences grouped with other Rhinolophus astrovirus sequences from China and Laos, while the Eoncyteris sequences formed a distinct clade with astroviruses from Rousettus spp. in Laos and Pteropus giganteus in Bangladesh, but not with other E. spelaea sequences. Longitudinal collections of Eonycteris feces demonstrated variable shedding. Juvenile status of bats was a risk factor for astroviruses. This study highlights the diversity of astroviruses in nectivorous and insectivorous bats in Singapore and provides a predictive framework for understanding astrovirus infection in these bats. It also suggests that in addition to host phylogenetic relatedness, host ecology, such as roosting behavior, may drive co-infections, virus maintenance and spillover.