Host specificity of Hepatocystis infection in short-nosed fruit bats (Cynopterus brachyotis) in Singapore.

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.

Genetic diversity and expanded host range of astroviruses detected in small mammals in Singapore.

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.

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.