Felicia Keesing

• Ph.D. University of California, Berkeley
• David & Rosalie Rose Distinguished Professor of the Sciences Mathematics & Computing at Bard College

Many terrestrial ecosystems are characterized by intermittent production of abundant resources for consumers, such as mast seeding and pulses of primary production following unusually heavy rains. Recent research is revealing patterns in the ways that consumer communities respond to these pulsed resources. Studies of the ramifying effects of pulsed...

Globally, most wildlife lives outside of protected areas, creating potential conflicts between the needs of wildlife and the needs of humans. East African savannas epitomize this challenge, providing habitat for wildlife such as giraffes and elephants as well as for people and their livestock. Conflicts over land use are common, leading to the assu...

Zoonotic diseases are infectious diseases of humans caused by pathogens that are shared between humans and other vertebrate animals. Previously, pristine natural areas with high biodiversity were seen as likely sources of new zoonotic pathogens, suggesting that biodiversity could have negative impacts on human health. At the same time, biodiversity...

For decades, people have reduced the transmission of pathogens by adding low‐quality hosts to managed environments like agricultural fields. More recently, there has been interest in whether similar ‘dilution effects’ occur in natural disease systems, and whether these effects are eroded as diversity declines. For some pathogens of plants, humans a...

Rodents are ubiquitous and typically unwelcome dwellers in human habitats worldwide, infesting homes, farm fields, and agricultural stores and potentially shedding disease-causing microbes into the most human-occupied of spaces. Of the vertebrate animal taxa that share pathogens with us, rodents are the most abundant and diverse, with hundreds of s...

Opportunistic sampling of ticks from animals during veterinary treatment offers important insights about wildlife exposure to pathogens. Here, we report pathogens and other tick‐borne organisms detected in ticks sampled from 10 animal species in and near Laikipia County, Kenya, in 2014–2016. Pathogen analysis was performed using a combination of Fl...

Medically important ixodid ticks often carry multiple pathogens, with individual ticks frequently coinfected and capable of transmitting multiple infections to hosts, including humans. Acquisition of multiple zoonotic pathogens by immature blacklegged ticks (Ixodes scapularis) is facilitated when they feed on small mammals, which are the most compe...

How frequently, and under what conditions, biodiversity reduces disease through “dilution effects” has been a subject of ongoing research. A new study of forest pests in PLOS Biology provides strong evidence for their generality.

Although human exposure to the ticks that transmit Lyme-disease bacteria is widely considered to occur around people’s homes, most studies of variation in tick abundance and infection are undertaken outside residential areas. Consequently, the patterns of variation in risk of human exposure to tick-borne infections in these human-dominated landscap...

Controlling the abundance of blacklegged ticks is considered the foundation for the prevention of human exposure to pathogens transmitted by these vectors in eastern North America. The use of broadcast or host-targeted acaricides is generally found to be effective at reducing the local abundance of ticks. However, studies that incorporate randomiza...

Background Controlling populations of ticks with biological or chemical acaricides is often advocated as a means of reducing human exposure to tick-borne diseases. Reducing tick abundance is expected to decrease immediate risk of tick encounters and disrupt pathogen transmission cycles, potentially reducing future exposure risk. Materials and Meth...

Acaricides are hypothesized to reduce human risk of exposure to tick-borne pathogens by decreasing the abundance and/or infection prevalence of the ticks that serve as vectors for the pathogens. Acaricides targeted at reservoir hosts such as small mammals are expected to reduce infection prevalence in ticks by preventing their acquisition of zoonot...

Despite the widespread adoption of motion-triggered camera traps, studies using camera traps to characterize wildlife communities in residential areas in North America are limited. To fill this data gap, we placed camera traps over three seasons in 22 residential neighborhoods within Dutchess County, NY. To account for imperfect detection, we appli...

Tickborne diseases (TBDs) such as Lyme disease result in ≈500,000 diagnoses annually in the United States. Various methods can reduce the abundance of ticks at small spatial scales, but whether these methods lower incidence of TBDs is poorly understood. We conducted a randomized, replicated, fully crossed, placebo-controlled, masked experiment to t...

Decades ago, a multi-factor perspective offered valuable insights into the causes of population cycles in arvicoline (= microtine) rodents. Multi-factor perspectives are also critical for understanding the ecology of infectious diseases. Here, we provide examples of how these perspectives inform our ability to predict variation in disease risk thro...

Lyme disease (also known as Lyme borreliosis) is the most common vector-borne disease in the United States with an estimated 476,000 cases per year. While historically, the long-term impact of Lyme disease on patients has been controversial, mounting evidence supports the idea that a substantial number of patients experience persistent symptoms fol...

We develop an agent-based model on a network meant to capture features unique to COVID-19 spread through a small residential college. We find that a safe reopening requires strong policy from administrators combined with cautious behavior from students. Strong policy includes weekly screening tests with quick turnaround and halving the campus popul...

Despite the widespread adoption of motion-triggered cameras, studies using camera-traps to characterize wildlife communities in human-impacted, residential areas in North America are limited. To fill this data gap, we placed camera traps over three seasons in 22 residential neighborhoods within Dutchess County, NY. To account for imperfect detectio...

Genetic diversity of Anaplasma phagocytophilum was assessed in specimens from 16 infected patients and 16 infectedIxodes scapularis ticks. A region immediately downstream of the 16S rRNA gene, which included the gene encoding SdhC, was sequenced. For the A. phagocytophilum strains from patients no sequence differences were detected in this region....

Borrelia miyamotoi, a bacterium that causes relapsing fever, is found in ixodid ticks throughout the northern hemisphere. The first cases of human infection with B. miyamotoi were identified in 2011. In the eastern USA, blacklegged ticks (Ixodes scapularis) become infected by feeding on an infected vertebrate host, or through transovarial transmiss...

We develop an agent-based model on a network meant to capture features unique to COVID-19 spread through a small residential college. We find that a safe reopening requires strong policy from administrators combined with cautious behavior from students. Strong policy includes weekly screening tests with quick turnaround and halving the campus popul...

Does the conversion of natural habitats to human use favour animals that harbour agents causing human disease? A global analysis of vertebrates provides an answer to this pressing question. Animals that can cause zoonotic disease flourish in human-altered areas.

Informed management of livestock on rangelands underpins both the livelihoods of communities that depend on livestock for sustenance, and the conservation of wildlife that often depend on livestock-dominated landscapes for habitat. Understanding spatial patterns of rangeland productivity is therefore crucial to designing global development strategi...

Following publication of the original article [1], one of the authors, Dr. Sarah E. Bowden reported that at the time of the study she wasn't working for the Division of Global Migration and Quarantine, Centers for Disease Control, 1600 Clifton Road, Atlanta, GA 30329-4027, USA.

Background: Exposure to blacklegged ticks Ixodes scapularis that transmit pathogens is thought to occur peri-domestically. However, the locations where people most frequently encounter infected ticks are not well characterized, leading to mixed messages from public health officials about where risk is highest. Methods: We conducted a systematic...

The emergence and spread of Lyme disease and other infections associated with blacklegged ticks is causing a public health crisis. No human vaccines are available, and both diagnosis and treatment are sometimes ineffectual, leading to advocacy for self-directed preventative measures. These recommendations are widely communicated to the public but w...

Public health authorities recommend a range of nonchemical measures to control blacklegged ticks Ixodes scapularis Say, 1821 (Ixodida: Ixodidae) in residential yards. Here we enumerate these recommendations and assess their relationship to larval tick abundance in 143 yards in Dutchess County, New York, an area with high Lyme disease incidence. We...

Tick microbiomes may play an important role in pathogen transmission. However, the drivers of microbiome variation are poorly understood, and this limitation has impeded mechanistic understanding of the functions of microbial communities for pathogen acquisition. The goal of this research was to characterize the role of the blood meal host in struc...

Populations of large wild mammals are declining worldwide, while the abundance of livestock is increasing. The absence of large mammals frequently leads to increases in the abundance of small mammals such as rodents, but little is known about how the loss of large mammals affects the behaviour of small mammals. To investigate this question, we anal...

The blacklegged tick Ixodes scapularis is the primary vector for the bacterium causing Lyme disease in eastern North America and for other medically important pathogens. This species is vulnerable to attack by fungal pathogens and arthropod predators, but the impacts of interactions between biocontrol agents have not been examined. The biocontrol a...

Exposure to environmental toxins such as heavy metals can perturb the development and stability of microbial communities associated with human or animal hosts. Widespread arsenic contamination in rivers and riparian habitats therefore presents environmental and health concerns for populations living near sources of contamination. To investigate how...

Compared observed richness of ASVs and OTUs.

Principle coordinates analysis (PCoA) based on unweighted UniFrac scores of zebrafish microbiota, using OTU table.

R markdown file with scripts outlining DADA2 forward read processing.

Mapping file with sample data.

ANOVA tables for PCoA comparisons.

OTUs differentially abundant in the presence of arsenic.

Genera counts of differentially abundant ASVs and OTUs.

Polynomial regressions for effect of arsenic on OTU alpha diversity.

OTUs differentially abundant in the presence of arsenic (P ≤ 0.01).

ASVs differentially abundant in the presence of arsenic (P ≤ 0.01).

ASVs differentially abundant in the presence of arsenic (P ≤ 0.05).

PCoA based on unweighted UniFrac scores of ASVs from zebrafish microbiota amplified for int1.

R markdown file with scripts outlining community analyses.

Fasta file with representative ASVs.

Alpha diversity metrics, measured with OTUs, with arsenic exposure.

Fasta file with representative OTUs.

Core microbiome in control population.

Changes to the community ecology of hosts for zoonotic pathogens, particularly rodents, are likely to influence the emergence and prevalence of zoonotic diseases worldwide. However, the complex interactions between abiotic factors, pathogens, vectors, hosts, and both food resources and predators of hosts are difficult to disentangle. Here we (1) us...

Most emerging infectious diseases of humans are transmitted to humans from other animals. The transmission of these “zoonotic” pathogens is affected by the abundance and behavior of their wildlife hosts. However, the effects of infection with zoonotic pathogens on behavior of wildlife hosts, particularly those that might propagate through ecologica...

Prevention of tick-borne diseases in humans is challenging. To date, no prevention strategies have been shown to be consistently effective. Here, we describe the design of a new large-scale study, involving hundreds of households in Dutchess County, New York, testing whether environmental interventions, applied intensively and over 4 years, can pre...

Previous studies have found that Met52®, which contains the entomopathogenic fungus Metarhizium brunneum, is effective in reducing the abundance of Ixodes scapularis, the tick vector for the bacterium causing Lyme disease and for other tick-borne pathogens. Given widespread interest in effective, safe methods for controlling ticks, Met52 has the po...

Analysis of deviance for the best-fitting model of arthropod abundance in bulk samples, considering data taken pre-treatment and 1 week post-treatment. There was a significant effect of habitat. (CSV)

Pitfall sample means and BACI effects. Order-level means (standard errors) and Before-After-Control-Impact effects (SEs) for pitfall samples. (CSV)

Analysis of deviance for the best-fitting model of arthropod abundance in pitfall samples, considering data taken pre-treatment and 1 week post-treatment. There was a significant effect of period. (CSV)

R code for retrospective and prospective bootstrap power analysis. (ZIP)

Analysis of deviance for the best-fitting model of arthropod abundance in bulk samples, considering data taken pre-treatment and 3 weeks post-treatment. There were significant effects of period, habitat, and location. (CSV)

Bulk sample means and BACI effects. Order-level means (standard errors) and Before-After-Control-Impact effects (SEs) for bulk samples. (CSV)

Analysis of deviance for the best-fitting model of arthropod abundance in pitfall samples, considering data taken pre-treatment and 5 weeks post-treatment. There was a significant effect of period and habitat. (CSV)

Arthropod abundance over time in bulk samples. Mean and standard error abundance for each order and sampling occasion for Met52 and control (H2O) plots for bulk sample data. (PNG)

Arthropod abundance over time in pitfall samples. Mean and standard error abundance for each order and sampling occasion for Met52 and control (H2O) plots for pitfall sample data. (PNG)

East Africa is a global hot spot for the diversity of ixodid ticks. As ectoparasites and as vectors of pathogens, ticks negatively affect the well-being of humans, livestock and wildlife. To prevent tick infestations, livestock owners and managers typically treat livestock with acaricides that kill ticks when they attempt to feed on livestock hosts...

Evolutionary traps occur when rapid environmental change causes animals to prefer poor-quality resources (e.g., habitats) or behaviors over higher-quality ones that lead to greater survival or reproductive success. Here, we bring together science from the pest-control, eco-evolutionary, and conservation communities to outline how evolutionary traps...

Because wildlife and livestock compete for grazing resources, biodiversity conservation and livestock ranching typically have been portrayed as conflicting uses of African savannas. Here, we offer an alternative perspective by describing a savanna ecosystem in central Kenya where wildlife and livestock exhibit a suite of potential positive interact...

Natural ecosystems provide services that support human well-being, but ecosystems may also contain elements that can endanger humans. Some researchers have argued that ecosystems that support high vertebrate diversity pose a danger to human health because they are likely to support a high diversity of zoonotic pathogens, leading to the emergence of...

Recent controversy over whether biodiversity reduces disease risk (dilution effect) has focused on the ecology of Lyme disease, a tick-borne zoonosis. A criticism of the dilution effect is that increasing host species richness might amplify disease risk, assuming that total host abundance, and therefore feeding opportunities for ticks, increase wit...

Global losses of biodiversity have galvanised efforts to understand how changes to communities affect ecological processes, including transmission of infectious pathogens. Here, we review recent research on diversity-disease relationships and identify future priorities. Growing evidence from experimental, observational and modelling studies indicat...

High-profile epidemics such as Ebola, avian influenza, and severe acute respiratory syndrome (SARS) repeatedly thrust infectious diseases into the limelight. Because the emergence of dis-eases involves so many factors, the need for interdisciplinary approaches to studying emerging infections, particularly those originating from animals (i.e., zoono...

On a floodplain of the River Saale near Jena, Germany, grassland plants are naturally bombarded by spores of pathogenic fungi. But whether or not those fungi cause infection turns out to be largely about the neighborhood: Plants on highly diverse experimental plots have much lower levels of infection than plants grown in monoculture ( 1 ) (see the...

The phenology of tick emergence has important implications for the transmission of tick-borne pathogens. A long lag between the emergence of tick nymphs in spring and larvae in summer should increase transmission of persistent pathogens by allowing infected nymphs to inoculate the population of naive hosts that can subsequently transmit the pathoge...

An age-old conflict around a seemingly simple question has resurfaced: why do we conserve nature? Contention around this issue has come and gone many times, but in the past several years we believe that it has reappeared as an increasingly acrimonious debate between, in essence, those who argue that nature should be protected for its own sake (intr...

Animal and plant species differ dramatically in their quality as hosts for multi-host pathogens, but the causes of this variation are poorly understood. A group of small mammals, including small rodents and shrews, are among the most competent natural reservoirs for three tick-borne zoonotic pathogens, Borrelia burgdorferi, Babesia microti, and Ana...

Humans in the northeastern and midwestern United States are at increasing risk of acquiring tickborne diseases - not only Lyme disease, but also two emerging diseases, human granulocytic anaplasmosis and human babesiosis. Co-infection with two or more of these pathogens can increase the severity of health impacts. The risk of co-infection is intens...

African savannas are home to an abundant and diverse assemblage of wild herbivores, but the very grasses that sustain these wild herds also make savannas attractive to humans and their livestock We used the Kenya Long-term Exclosure Experiment to investigate the ecological effects of different combinations of native and domestic grazers. The experi...

Anaplasmosis is an emerging infectious disease caused by infection with the bacterium Anaplasma phagocytophilum. In the eastern United States, A. phagocytophilum is transmitted to hosts through the bite of the blacklegged tick, Ixodes scapularis. We determined the realized reservoir competence of 14 species of common vertebrate hosts for ticks by e...

Biodiversity supports and protects human health in many ways, and the continuing loss of biodiversity will compromise this support system. Some species currently or potentially of conservation concern provide animal models important for basic biomedical research. Others contain substances that can be used or modified to produce medicines of enormou...

In African savannas, large mammals, both wild and domestic, support an abundant and diverse population of tick ectoparasites. Because of the density of ticks and the many pathogens that they vector, cattle in East Africa are often treated with acaricides. While acaricides are known to be effective at reducing tick burdens on cattle, their effects o...

Mixed hardwood forests of the northeast United States support a guild of granivorous/omnivorous rodents including gray squirrels (Sciurus carolinensis), eastern chipmunks (Tamias striatus), and white-footed mice (Peromyscus leucopus). These species coincide geographically, co-occur locally, and consume similar food resources. Despite their idiosync...

Detailed information on the overall trapping schedule and exceptions to that schedule. (DOCX)

The AICc-related metrics of fit of the Huggins robust design models used to examine the effects of mouse and chipmunk abundance on the apparent survival and capture probability of squirrels. (DOCX)

The AICc-related metrics of fit of the Huggins robust design models used to examine the effects of mouse and squirrel abundance on the apparent survival and capture probability of chipmunks. (DOCX)

How sites were assigned to removal and recipient/addition treatments, or to the control treatment. (DOCX)

The AICc-related metrics of fit of the Huggins robust design models used to examine the effects of chipmunk and squirrel abundance on the apparent survival and capture probability of mice. (DOCX)

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Invasive species, range-expanding species, genetically modified organisms (GMOs), synthetic organisms, and emerging pathogens increasingly affect the human environment. We propose a framework that allows comparison of consecutive stages that such novel organisms go through. The framework provides a common terminology for novel organisms, facilitati...

Infectious diseases involve at least two species - the host and the pathogen - which must come into contact either directly or indirectly for the pathogen to be transmitted. Thus, transmission is an inherently spatial process. Landscape epidemiology, broadly defined, is the study of spatial variation in disease risk or incidence. In this entry, maj...

Human babesiosis is an increasing health concern in the northeastern United States, where the causal agent, Babesia microti, is spread through the bite of infected Ixodes scapularis ticks. We sampled 10 mammal and 4 bird species within a vertebrate host community in southeastern New York to quantify reservoir competence (mean percentage of ticks in...