High diversity of West African bat malaria parasites and a tight link with rodent Plasmodium taxa

Abstract

As the only volant mammals, bats are captivating for their high taxonomic diversity, for their vital roles in ecosystems--particularly as pollinators and insectivores--and, more recently, for their important roles in the maintenance and transmission of zoonotic viral diseases. Genome sequences have identified evidence for a striking expansion of and positive selection in gene families associated with immunity. Bats have also been known to be hosts of malaria parasites for over a century, and as hosts, they possess perhaps the most phylogenetically diverse set of hemosporidian genera and species. To provide a molecular framework for the study of these parasites, we surveyed bats in three remote areas of the Upper Guinean forest ecosystem. We detected four distinct genera of hemosporidian parasites: Plasmodium, Polychromophilus, Nycteria, and Hepatocystis. Intriguingly, the two species of Plasmodium in bats fall within the clade of rodent malaria parasites, indicative of multiple host switches across mammalian orders. We show that Nycteria species form a very distinct phylogenetic group and that Hepatocystis parasites display an unusually high diversity and prevalence in epauletted fruit bats. The diversity and high prevalence of novel lineages of chiropteran hemosporidians underscore the exceptional position of bats among all other mammalian hosts of hemosporidian parasites and support hypotheses of pathogen tolerance consistent with the exceptional immunology of bats.

Keywords: Chiroptera; Haemosporida; host–pathogen coevolution; molecular phylogeny; vector-borne disease.

Fig. 1.

Bat sampling areas in West Africa. Bats were captured during the dry season between November and December 2006 in Taï National Park, Côte d’Ivoire, in December 2008 in the Forêt Classée de Pic de Fon in the Simandou range of Guinea, and between November and December 2010 in the Putu range in southeastern Liberia.

Fig. 2.

Haemosporida from West African bats separate into four distinct genera. (A) Three-genome phylogeny of the hemosporidian parasites of the bats of this study, including published sequences for context, obtained by ML. Phylogeny was constructed with partitioned analysis of mitochondrial (cytb, cox1), apicoplast (clpc), and nuclear (ef2a) genes, rooted with Leucocytozoon taxa. ML bootstrap values (100 replicates) and Bayesian posterior probabilities are indicated above and below nodes, respectively. Recent divergences with high nodal support are indicated by black dots. Genera of bat malaria parasites are labeled to the right. Hemosporidian parasites from this study are highlighted in bold type. (B) ML phylogeny of bat and rodent Plasmodium species obtained via analysis of four genes as in A, plus nine additional nuclear genes (actin-1, actin-2, adenylosuccinate lyase, cysteine proteinase, dihydrofolate reductase/thymidylate synthase, histone H2A, inosine monophosphate-dehydrogenase, ookinete surface protein P25, and polyubiquitin), with three primate taxa included as outgroups.

Fig. 3.

Hemosporidian parasites and their host species. Shown are captured bats and representative micrographs of Giemsa-stained thin blood films of their respective hemosporidian parasite blood stages (r, ring stage; s, schizont; g, gametocyte). (A) P. cyclopsi and P. voltaicum blood stages isolated from H. cyclops and M. angolensis, respectively. (B) Polychromophilus gametocytes isolated from miniopterid and vespertilionid bats. (C) Nycteria gametocytes isolated from two rhinolophid bats. (D) Hepatocystis blood stages isolated from six pteropodid bats. Shown are two (Micropteropus pusillus, Myonycteris leptodon) of six host species and different blood stages of their parasites. Micrographs were taken at 1,000× magnification.