Project

Disease ecology

Traditionally, ecologists studied only “healthy animals and plants” while doctors and veterinarians studied the effects of microorganisms and pathogens on animals and people.

However, with the emergence of the ‘One Health concept’ (www.onehealthinitiative.com) it becomes increasingly clear that these disciplinary boundaries are an impediment to improve the health of people, livestock and wildlife. Ecologists can contribute to the ‘One Health’.The Resource Ecology Group has identified this as an important new development: we have been working hard on movement ecology, and in combination with our knowledge on the ecology and distribution of wild living herbivores, we believe that we can make an important contribution. Moreover, parasite prevalence and infectious diseases play a primary role in ecological, social and evolutionary processes, but the drivers are still poorly understood. Our group wants to become an important player in Disease Ecology and we will concentrate on zoonotic, vector-borne or livestock/wildlife related disease transfer, focussing on a distinctive group of vectors or carriers. For our Disease Ecology Programme the mission is: “To improve understanding of wild animals as vectors of (zoonotic) diseases in a landscape context through conducting state of the art animal (movement) ecology”. These studies are typically carried out in collaboration with molecular ecologists and epidemiologists. Besides initiating new research projects we also teach Disease Ecology at the highest possible academic level.


Disease-impala.jpg

Our expertise is based on why and how animals are moving, which can have large consequences for disease transmission and dispersal. We concentrated on the issue of resource acquisition to explain movement and distribution of animals: what are the most optimal ways of animals moving through a two-dimensional space, given a particular resource distribution (Hengeveld et al. 2009). So far, attention was paid to the optimal strategy in different densities of resource points. Our group added the effect of resource aggregation and resource quality on resource acquisition (Hengeveld et al. 2009; Huisman et al. submitted). We then started looking at real animals (first with goats, De Knegt et al. 2007), and put radio-collars on some of the species under study: a large data set of movements of African elephant was thus collected and analysed (De Knegt et al. 2010, 2011). We also use camera-trapping and other techniques to quantify animal movements, densities and community compositions in the rainforest over different gradients of disturbance. Using these approaches, we now better understand how daily and seasonal movements of large herbivores are related to resources availabilty at different spatial scales, which are important to understand disease spread and difference in prevalence rates.

An important result of De Knegt’s work was that temperature plays a significant role not only in habitat selection but also in explaining movement patterns, and hence in determining animal distribution. This we further investigate currently through the implantation of thermologgers in the abdominal cavity and thermometers on top of the head of eland antelopes, wildebeest and impala in two climatically contrasting areas; results of the PhD student Anil Shrestha shows that temperature indeed plays a significant role in species’ distribution and habitat selection. Currently we upscale this to research that we conduct in South Africa with implants on lions, and GPS-loggers on wildebeest, zebra and lions.

New molecular tools enable us to take on the movements of wild geese as possible vectors of avian influenza: the results are clear and show that they can carry such a disease and that migrating wildfowl are important vectors that might be implicated in the spread of avian influenza (Si et al. 2009, 2010, 2013). Hence, changes in landscape configuration can modify migration routes, and thereby also change disease risk through changes in movement of infected birds (PhD student Mikhail Grishchenko). Additional analyses show that geese wintering in the Netherlands pick up AI viruses on their wintering grounds and not before suggesting that arctic breeding species unlikely to disperse Asian AI viruses from their Siberian breeding grounds to their European wintering areas (Kleijn et al. 2010). Genetic exchange of material can also be related to large probabilities of disease transmission. For instance we analyse how corridors linking different habitat fragments influence genetic exchange (PhD student Joost de Jong), which could potentially also affect the spread of diseases through increased dispersal of their hosts. To better quantify the genetic landscape we developed SNP-sets for the genetic typing of mallards from all over the northern hemisphere: they prove to be panmictic (Kraus et al 2012). For sampling we developed the use of FTA-cards for the safe transportation of blood and faecal samples from all over the world (Kraus et al. 2010, 2011). A similar approach is now being used for the wild boar as well and we have demonstrated recent genetic introgression from domestic pigs into wild boar populations with large implications for disease transmission (PhD student Daniel Goedbloed). The movements of geese have taken us further, so that we now understand much better their migratory behaviour (Jonker et al 2010, 2011) through both modelling work and very detailed genetic analyses. We have linked this to research on personalities of leading and following in geese (e.g., Kurvers et al. 2010, 2011). This work resulted in a RUBICON scholarship. For the period 2013-2015 we will continue the work on migratory geese and their genetics.

Disease-bosmuis2.jpg

We started research on Lyme’s disease and especially the ecology of ticks in relation to the occurrence of roe deer and mice. To understand mouse behaviour and movements better, we investigate the resource distribution of acorns and the effect of hoarding by mice (PhD student Lennart Suselbeek), and to understand ticks better PhD student Jasper van der Linden investigates patterns in their densities and in the incidence of infection of ticks with Borrelia. We aim to quantify host quality of different mammal species for ticks and Borrelia. By studying species with different reproductive strategies, we aim to find a relationship between life history traits and host quality using both field work and lab experiments (PhD student Tim Hofmeester).

We also analysed interactions between host genetics, body condition and bovine tuberculosis (bTB) in African buffalo showing that the genetic background played a critical rôle in disease transmission (Van Hooft et al. 2007, 2010). This work can have important implications for management of bTB at the human-livestock-wildlife interface.

Understanding the factors driving parasite prevalence and the spread of infectious diseases is at the heart of disease ecology. The effects of habitat disturbance on the prevalence of animal parasites, with associated risk of infectious disease transmission, are still poorly understood. By improving our understanding of the relations between anthropogenic and natural stress factors and the occurrence of parasites we increased our insight into disease prevalence of wild non-human primates (PhD student Iris de Winter).

We also showed that disease competence is related to species traits, which has large consequences for the loss of species in disturbed systems (PhD student Zheng Huang). These relationships are probably at the basis of the so-called dilution effect, the negative effect of species richness on disease prevalence. The dilution effect has recently attracted large attention, especially in relation to the world-wide increase in habitat fragmentation and decrease in species richness. This species richness – disease prevalence relationship was also detected in bTB outbreaks in cattle in Africa, using the large database of the OIE (World Organisation for Animal Health; PhD student Zheng). We also study how the community composition of vertebrates affect the parasite assemblage such as ticks and fleas, and ultimately agents of infectious diseases, including diseases that are harmful to people, such as the Rocky Mountain Spotted Fever caused by Rickettsia bacteria. We aim to determine how host-specific parasites are to vertebrates, how host-specific disease agents are to their parasite hosts, and how suitable different vertebrates are as reservoirs for diseases (PhD student Helen Esser).

At present we have initiated new research initiatives that focus on the ecology of diseases, the spread of diseases in relation to movement of hosts, and the underlying causal mechanisms that drive these movements and change disease prevalence.

Staff

PhD candidates

Former PhD students


Dr. Dick Dekker
Dr. Dick Dekker
Dr. Vincent Comor
Dr. Vincent Comor
Dr. Ralf Kurvers
Dr. Ralf Kurvers
Dr. Rudy Jonker
Dr. Rudy Jonker
Dr. Robert Kraus
Dr. Robert Kraus
Dr. Daniël Goedbloed
Dr. Daniël Goedbloed
Dr. Tom Huisman
Dr. Tom Huisman
Dr. Zheng Huang
Dr. Zheng Huang

Former PhD student without picture

Dr. Yali Si