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

Abstract

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.

Keywords: Bat; Ecology; Evolution; Haemosporidia; Hepatocystis; Host specificity; Singapore.

Graphical abstract

Fig. 1

Micrographs from Giemsa-stained blood smears from short-nosed fruit bats (Cynopterus brachyotis) (a) showing Hepatocystis parasites shown at 1000X magnification. Early-stage gametocytes (b) presented as a ring form with a chromatin dot, while more developed young gametocytes had a solid nucleus (c). Microgametocytes had a large nucleus that was absent of granules, with the majority stained light red and a smaller portion stained dark red (d). The macrogametocyte stained blue with pigment granules throughout the cytoplasm, had a comparatively smaller nucleus that stained purple (e). Photo of C. brachyotis by Lim Zong Xian.

Fig. 2

Evolutionary relationships of the mitochondrial cytochrome B (Cyt-b) gene sequences of Hepatocystis parasites detected in different mammalian hosts. The tree phylogeny was reconstructed using the maximum likelihood method in RAxML. Coloured branches denote different host species. Bootstrap values above 50% are indicated at the major nodes. Scale bar indicates the number of nucleotide substitutions per site. Red fonts represent novel Hepatocystis sequences generated from this study. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 3

Co-variate analysis for the probability of infection in Cynopterus brachyotis in relation to site, age, season, and sex. Error bars are 89% CI. (a) Logit-transformed model estimates of Hepatocystis prevalence among four sampled sites in Singapore; (b) Logit-transformed model estimates of Hepatocystis prevalence among seasons; (c) Logit-transformed model estimates for probability of infection by age; (d). Logit-transformed model estimates for probability of infection by sex.

Fig. 4

Relationship of body condition (weight of individual/forearm length) to probability of Hepatocystis infection. Open blue circles are the observed data. The red line is the estimated linear relationship, and the shaded area represents the 89% CI. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)