Daytime behavior of Pteropus vampyrus in a natural habitat: the driver of viral transmission

Nipah Virus Disease: Epidemiological, Clinical, Diagnostic and Legislative Aspects of This Unpredictable Emerging Zoonosis

Nipah virus (NiV) infection is a viral disease caused by a Henipavirus, belonging to the Paramyxoviridae family, responsible for a zoonosis. The course of the disease can be very serious and lead to death. NiV natural hosts are fruit bats (also known as megabats) belonging to the Pteropodidae family, especially those of the Pteropus genus. Natural infection in domestic animals has been described in farming pigs, horses, domestic and feral dogs and cats. Natural NiV transmission is possible intra-species (pig-to-pig, human-to-human) and inter-species (flying bat-to-human, pig-to-human, horse-to-human). The infection can be spread by humans or animals in different ways. It is peculiar how the viral transmission modes among different hosts also change depending on the geographical area for different reasons, including different breeding methods, eating habits and the recently identified genetic traits/molecular features of main virus proteins related to virulence. Outbreaks have been described in Malaysia, Singapore, Bangladesh, India and the Philippines with, in some cases, severe respiratory and neurological disease and high mortality in both humans and pigs. Diagnosis can be made using different methods including serological, molecular, virological and immunohistochemical methods. The cornerstones for control of the disease are biosecurity (via the correct management of reservoir and intermediate/amplifying hosts) and potential vaccines which are still under development. However, the evaluation of the potential influence of climate and anthropogenic changes on the NiV reservoir bats and their habitat as well as on disease spread and inter-specific infections is of great importance. Bats, as natural reservoirs of the virus, are responsible for the viral spread and, therefore, for the outbreaks of the disease in humans and animals. Due to the worldwide distribution of bats, potential new reports and spillovers are not to be dismissed in the future.

Re-examining extreme sleep duration in bats: implications for sleep phylogeny, ecology, and function

Bats, quoted as sleeping for up to 20 h a day, are an often used example of extreme sleep duration amongst mammals. Given that duration has historically been one of the primary metrics featured in comparative studies of sleep, it is important that species specific sleep durations are well founded. Here, we re-examined the evidence for the characterization of bats as extreme sleepers and discuss whether it provides a useful representation of the sleep behavior of Chiroptera. Although there are a wealth of activity data to suggest that the diurnal cycle of bats is dominated by rest, estimates of sleep time generated from electrophysiological analyses suggest considerable interspecific variation, ranging from 83% to a more moderate 61% of the 24 h day spent asleep. Temperature-dependent changes in the duration and electroencephalographic profile of sleep suggest that bats represent a unique model for investigating the relationship between sleep and torpor. Further sources of intra-specific variation in sleep duration, including the impact of artificial laboratory environments and sleep intensity, remain unexplored. Future studies conducted in naturalistic environments, using larger sample sizes and relying on a pre-determined set of defining criteria will undoubtedly provide novel insights into sleep in bats and other species.

Viral-derived DNA invasion and individual variation in an Indonesian population of large flying fox Pteropus vampyrus

Here, we performed next-generation sequencing (NGS) on six large flying foxes (Pteropus vampyrus) collected in Indonesia. Seventy-five virus species in the liver tissue of each specimen were listed. Viral homologous sequences in the bat genome were identified from the listed viruses. This finding provides collateral evidence of viral endogenization into the host genome. We found that two of the six specimens bore partial sequences that were homologous to the plant pathogens Geminiviridae and Luteoviridae. These sequences were absent in the P. vampyrus chromosomal sequences. Hence, plant viral homologous sequences were localized to the hepatocytes as extrachromosomal DNA fragments. Therefore, this suggests that the bat is a potential carrier or vector of plant viruses. The present investigation on wild animals offered novel perspectives on viral invasion, variation, and host interaction.

Dispersal history of Miniopterus fuliginosus bats and their associated viruses in east Asia

In this study, we examined the role of the eastern bent-winged bat (Miniopterus fuliginosus) in the dispersion of bat adenovirus and bat alphacoronavirus in east Asia, considering their gene flows and divergence times (based on deep-sequencing data), using bat fecal guano samples. Bats in China moved to Jeju Island and/or Taiwan in the last 20,000 years via the Korean Peninsula and/or Japan. The phylogenies of host mitochondrial D-loop DNA was not significantly congruent with those of bat adenovirus (m2XY = 0.07, p = 0.08), and bat alphacoronavirus (m2XY = 0.48, p = 0.20). We estimate that the first divergence time of bats carrying bat adenovirus in five caves studied (designated as K1, K2, JJ, N2, and F3) occurred approximately 3.17 million years ago. In contrast, the first divergence time of bat adenovirus among bats in the 5 caves was estimated to be approximately 224.32 years ago. The first divergence time of bats in caves CH, JJ, WY, N2, F1, F2, and F3 harboring bat alphacoronavirus was estimated to be 1.59 million years ago. The first divergence time of bat alphacoronavirus among the 7 caves was estimated to be approximately 2,596.92 years ago. The origin of bat adenovirus remains unclear, whereas our findings suggest that bat alphacoronavirus originated in Japan. Surprisingly, bat adenovirus and bat alphacoronavirus appeared to diverge substantially over the last 100 years, even though our gene-flow data indicate that the eastern bent-winged bat serves as an important natural reservoir of both viruses.

The spleen morphophysiology of fruit bats

Spleen is one of the important lymphoid organs with wide variations of morphological and physiological functions according to species. Morphology and function of the spleen in bats, which are hosts to several viral strains without exhibiting clinical symptoms, remain to be fully elucidated. This study aims to examine the spleen morphology of fruit bats associated with their physiological functions. Spleen histological observations were performed in three fruit bats species: Cynopterus titthaecheilus (n = 9), Rousettus leschenaultii (n = 3) and Pteropus vampyrus (n = 3). The spleens of these fruit bats were surrounded by a thin capsule. Red pulp consisted of splenic cord and wide vascular space filled with blood. Ellipsoids in all three studied species were found numerously and adjacent to one another forming macrophages aggregates. White pulp consisted of periarteriolar lymphoid sheaths (PALS), lymphoid follicles and marginal zone. The lymphoid follicle contained a germinal centre and a tingible body macrophage that might reflect an active immune system. The marginal zone was prominent and well developed. This study reports some differences in spleen structure of fruit bats compared to other bat species previously reported and discusses possible physiological implications of the spleen based on its morphology.

Seasonal variation in the number of deaths in Pteropus lylei at Wat Pho Bang Khla temple, Thailand

Flying foxes have been widely studied as they are well-known reservoirs of infectious agents. Understanding their population dynamics might help to explain seasonal patterns of disease prevalence, and contribute towards the conservation of flying fox populations. Therefore, this study explored the annual variation in the number of deaths in P. lylei. The study was conducted from 2015-2017, at a Buddhist temple in Thailand, which is the roosting site of P. lylei. The average total number of bat deaths in a month significantly varied between times of a year. A peak was observed during March and May, which ranged in the period of birthing and lactating. There were no significant differences in the average total number of bat deaths in a month between sexes or age classes across times of a years.

Nighttime behavioral study of flying foxes on the southern coast of West Java, Indonesia

Flying foxes are important in the maintenance of forests and diversity. However, knowledge of their behavioral ecology, especially of movement and foraging patterns, which are essential for conservation and management of their populations, are not well known. Therefore, movement behavior of two individuals of Pteropus vampyrus were examined using an Argos telemetry system, and foraging pattern of Pteropus spp. was directly observed, at West Java province, Indonesia in October 2017. The maximum distance between the location at which bats were released and their furthest roost, recorded via satellite telemetry, was approximately 100 km. This reflects the long-distance flight ability of P. vampyrus. Daytime roosting sites and nighttime foraging places consisted of several types of habitats, such as intact forests, agricultural lands, and residential areas. This evidence indicated that there was habitat overlap between humans and bats in West Java province. According to direct observation of the behaviors of flying foxes at two locations within residential areas, various activities such as wing spreading, excretion, fighting, aggressive calls, movement, hanging relax, and hanging alert were found. The number of bat-visits to the trees varied among night hours, and had a positive correlation with the number of fruit dropping. The data obtained in this study have improved our understanding of nighttime behavior and habitat utilization of P. vampyrus, that can be used to support landscape management, species conservation, and disease prevention in regions of Southeast Asia.

Diurnal behavior and activity budget of the golden-crowned flying fox (Acerodon jubatus) in the Subic bay forest reserve area, the Philippines

Acerodon jubatus (the Golden-Crowned flying fox) is an endemic species in the Philippines, which was suspected to be a host of the Reston strain of the Ebola virus. As nocturnal animals, the flying foxes spend daytime at the roosting site, which they use for self-maintenance and reproduction. To understand the variation in diurnal behavior and time allocation for various activities in the Golden-Crowned flying fox, we investigated their daytime behavior and activity budget using instantaneous scan sampling and all occurrence focal sampling. Data collection was performed from 07:00 to 18:00 hr during January 8–17, 2017. The most frequent activity was sleeping (76.3%). The remaining activities were wing flapping (5.0%), self-grooming (4.2%), hanging relaxation (3.4%), wing spread (2.9%), movement (2.4%), mating/courtship (2.4%), aggression (1.9%), hanging alert (1.2%), excretion (0.1%) and scent marks (0.05%). The frequency of sleeping, wing flapping, self-grooming, hanging relaxation, aggression, mating/courtship and movement behaviors changed with the time of the day. Females allocated more time for resting than males, while males spent more time on the activities that helped enhance their mating opportunities, for example, movement, sexual activity and territorial behavior.