Unraveling the complex relationships between Afrotropical bats, eukaryotic parasites, and the microbial communities that mediate their interactions
Recent research reveals that microbial communities on bats may determine their susceptibility to parasites, opening new windows into disease transmission and wildlife conservation.
Imagine a moonless night in the African tropics. A bat emerges from its roost, taking flight in search of food. But it carries with it an entire ecosystem—a complex world of microbes and parasites living on and inside its body. This isn't just a single organism, but a living, breathing community of species, all interacting in ways science is just beginning to understand.
Recent research has revealed that the skin, mouth, and gut of bats host diverse bacterial communities that may determine whether these winged mammals fall victim to parasites. The discovery that microbes mediate relationships between bats and their parasites opens new windows into understanding disease transmission, wildlife conservation, and even human health. As bats face growing threats from habitat loss and emerging diseases, understanding these intricate relationships becomes increasingly urgent 1 2 .
Investigating how microbial communities on bats influence their interactions with parasites like bat flies and malaria-causing pathogens.
Field research conducted across 14 sites in Kenya and Uganda, sampling diverse Afrotropical bat species.
To understand the significance of this research, we first need to understand the key players in this ecological drama.
Specialized blood-feeding insects that spend most of their lives on bats 2 .
Malaria-causing parasites that complete part of their life cycle in bat blood 4 .
Communities of bacteria living on bat skin and in their bodies 1 .
Scientists have hypothesized that a host's microbiome influences its attractiveness to parasites and its susceptibility to infection. This idea, called the "microbial mediator hypothesis," suggests that the bacteria living on and in an animal produce chemical signals that either attract or repel parasites 1 2 .
Specific bacteria colonize bat skin
Bacteria produce volatile organic compounds (VOCs)
Bat flies detect VOCs as host location cues
Attraction or repulsion determines parasitism
For blood-feeding insects like mosquitoes and bat flies, volatile organic compounds (VOCs) released by skin bacteria serve as important chemical cues that help locate hosts. The specific blend of VOCs produced depends on which bacteria are present and in what quantities. Similarly, the oral and gut microbiomes may influence whether an animal succumbs to infections once parasites enter the body 1 2 .
To test the microbial mediator hypothesis in wild bats, an international team of researchers embarked on an extensive field study across Kenya and Uganda. From August to October 2016, they collected samples from multiple bat species at 14 different field sites, using mist nets and hand nets to capture their subjects 2 .
14 field sites identified across Kenya and Uganda representing diverse habitats
Mist nets and hand nets used to capture bats during nightly foraging activities
Comprehensive sampling protocol implemented for each captured bat
Samples transported to laboratories for DNA extraction and analysis
The sampling protocol was meticulously designed to capture comprehensive data about each bat's parasites and microbial communities:
| Sample Type | Collection Method | Purpose | Storage Method |
|---|---|---|---|
| Skin biopsies | 3mm punches from wing, tail, ear, back, and chest | Characterize skin microbiome | Combined per individual in 95% ethanol |
| Oral tissue | Whole tongue collection | Characterize oral microbiome | 95% ethanol |
| Blood samples | Cardiac puncture (2-4ml) | Detect malarial parasites | FTA cards, blood films, and cryovials in liquid nitrogen |
| Ectoparasites | Physical examination after fumigation | Identify and count bat flies | 95% ethanol for morphological ID |
Back in the laboratory, each sample underwent specialized analysis:
DNA from skin, oral, and gut samples was sequenced to identify which bacteria were present and in what proportions 2 .
Bat flies were identified under microscopes using specialized taxonomic keys. Malarial parasites were detected through DNA extraction from blood samples 2 .
Advanced statistical methods were used to determine whether bacterial communities differed between bats with and without ectoparasites 1 .
This comprehensive approach allowed scientists to compare parasitized and non-parasitized bats while accounting for factors like bat species, location, and evolutionary history.
The analysis revealed several fascinating patterns. Most notably, researchers found significant correlations between the composition of skin bacterial communities and the presence of bat flies across four major bat lineages. The skin microbial networks differed strikingly between bats with ectoparasites and those without 1 2 .
This suggests that the particular combination of bacteria living on bat skin—not just the presence or absence of specific types—might influence whether bat flies are attracted to a particular host. Certain bacterial communities may produce chemical profiles that bat flies find either attractive or repellant 1 .
| Finding | Significance | Bat Groups Affected |
|---|---|---|
| Skin microbiome composition correlated with bat fly prevalence | Supports role of skin bacteria in attracting or repelling ectoparasites | Across four major bat lineages |
| Differences in skin microbial network characteristics between parasitized and non-parasitized bats | Suggests specific bacterial community structures may deter parasites | All studied bat species |
| Oral microbiome linked to malarial parasite presence | Indicates mouth bacteria may influence susceptibility to blood parasites | Miniopterid bats specifically |
| Weak correlation between bat evolutionary history and microbiome composition | Shows environment is more important than ancestry in shaping microbiome | All studied bat species |
Perhaps even more intriguing was the discovery of links between the oral microbiome and the presence of haemosporidian parasites in miniopterid bats. While the exact mechanism remains unclear, researchers hypothesize that bacteria in the mouth might influence whether malarial parasites can successfully establish infection 1 3 .
This finding parallels studies in other systems that have shown gut microbiota can influence susceptibility to malarial parasites. For example, some research suggests that certain gut bacteria can enhance immune responses that protect against malaria, while others might create conditions that favor parasite establishment .
Another important insight from the study was that host environment appears more important than shared evolutionary history in shaping the composition of bat-associated bacterial communities. When researchers compared the microbiomes of different bat species, they found only a weak correlation between how closely related bats were and how similar their microbiomes were 3 .
A bat's microbial community is apparently shaped more by where it lives and how it behaves than by its evolutionary lineage.
Conducting comprehensive wildlife microbiome research requires specialized tools and reagents. The following table details key materials used in the Afrotropical bat study and their specific functions:
| Tool/Reagent | Specific Function | Application in the Study |
|---|---|---|
| Sterile disposable biopsy punches (3mm) | Collect uniform skin samples without cross-contamination | Sampling bat wing, tail, ear, back, and chest skin |
| 95% ethanol | Preserve DNA and morphological structures | Storage of skin biopsies, oral tissue, and bat flies |
| Qiagen DNeasy kits | Extract high-quality DNA from various sample types | Isolate DNA from blood samples for parasite detection |
| PCR reagents and Sanger sequencing | Amplify and identify specific DNA sequences | Confirm presence and identity of malarial parasites |
| Illumina sequencing platforms | Characterize microbial community composition | Analyze 16S rRNA genes to identify bacterial taxa |
| Leica MZ16 stereozoom microscope | Examine morphological features of ectoparasites | Identify bat flies to species level using taxonomic keys |
| FTA cards | Stabilize and preserve DNA from blood samples | Transport blood samples from field to laboratory |
Working in remote African locations required portable equipment and preservation methods that could withstand tropical conditions and limited access to laboratory facilities.
Analyzing microbiome data required sophisticated bioinformatics tools to process millions of DNA sequences and identify meaningful patterns across hundreds of samples.
The discovery that microbial symbionts may serve as indirect mediators of parasitism among bats and their eukaryotic parasites has profound implications for our understanding of host-parasite evolution. If certain bacterial communities make bats less attractive to parasites or less susceptible to infection, then over evolutionary time, bats might evolve mechanisms to cultivate these protective microbes 1 .
This introduces a fascinating third party to the classic evolutionary arms race between hosts and parasites. Rather than a simple two-player game, we now see a more complex relationship where hosts, their microbes, and parasites are all engaged in a delicate dance of adaptation and counter-adaptation 1 .
Understanding these relationships becomes especially important in the context of bat conservation and human health. Bats face numerous threats worldwide, including habitat destruction and white-nose syndrome. If disturbances affect bat microbiomes, they might inadvertently make bats more vulnerable to parasites and pathogens 1 2 .
Habitat destruction may disrupt the delicate balance of bat microbiomes, potentially increasing susceptibility to parasites and disease.
Understanding parasite transmission in bats could help predict and prevent spillover events of pathogens to human populations.
Additionally, as bats are reservoirs for several human pathogens, understanding the factors that influence parasite and pathogen transmission in bat populations could help predict and prevent spillover events. The study of bat flies is particularly relevant since they're known to harbor several pathogens of human concern 2 .
While the Afrotropical bat study provided compelling evidence for microbiome-parasite links, many questions remain unanswered. Future research aims to:
The hidden world of bats and their microbial companions reminds us that no animal exists in isolation. Each bat is a complex ecosystem, a flying community whose invisible residents may determine its health and survival.
The bacteria living on bat skin and in their mouths appear to play crucial roles in mediating interactions with larger, more noticeable parasites. This research transforms our understanding of relationship dynamics in nature, revealing that sometimes the smallest players—the microbial symbionts—may exert surprising influence over the fates of their larger hosts.
As we continue to unravel these complex interactions, we gain not only deeper appreciation for ecological complexity but also potential new tools for conserving wildlife and protecting human health.
you're not just looking at a single creature, but at an entire world in flight.