Effect of host populations on the intensity of ticks and the prevalence of tick-borne pathogens: how to interpret the results of deer exclosure experiments

Parasitology ◽  
2008 ◽  
Vol 135 (13) ◽  
pp. 1531-1544 ◽  
Author(s):  
A. PUGLIESE ◽  
R. ROSÀ
Keyword(s):  
Ixodes Ricinus ◽  
Dynamic Models ◽  
Infection Risk ◽  
Northern Italy ◽  
Pathogen Transmission ◽  
Infection Prevalence ◽  
Tick Density ◽  
Dead End ◽  
Tick Borne Encephalitis ◽  
Experimental Plots

SUMMARYDeer are important blood hosts for feeding Ixodes ricinus ticks but they do not support transmission of many tick-borne pathogens, so acting as dead-end transmission hosts. Mathematical models show their role as tick amplifiers, but also suggest that they dilute pathogen transmission, thus reducing infection prevalence. Empirical evidence for this is conflicting: experimental plots with deer removal (i.e. deer exclosures) show that the effect depends on the size of the exclosure. Here we present simulations of dynamic models that take into account different tick stages, and several host species (e.g. rodents) that may move to and from deer exclosures; models were calibrated with respect to Ixodes ricinus ticks and tick-borne encephalitis (TBE) in Trentino (northern Italy). Results show that in small exclosures, the density of rodent-feeding ticks may be higher inside than outside, whereas in large exclosures, a reduction of such tick density may be reached. Similarly, TBE prevalence in rodents decreases in large exclosures and may be slightly higher in small exclosures than outside them. The density of infected questing nymphs inside small exclosures can be much higher, in our numerical example almost twice as large as that outside, leading to potential TBE infection risk hotspots.

scholarly journals Prevalence and genetic variability of tick-borne encephalitis virus in host-seeking Ixodes ricinus in northern Italy

2009 ◽  
Vol 90 (12) ◽  
pp. 2877-2883 ◽  
Author(s):  
Giovanna Carpi ◽  
Luigi Bertolotti ◽  
Sergio Rosati ◽  
Annapaola Rizzoli
Keyword(s):  
Genetic Variability ◽  
Ixodes Ricinus ◽  
Evolutionary Dynamics ◽  
Phylogenetic Analyses ◽  
Northern Italy ◽  
Nucleotide Sequence Analysis ◽  
Envelope Gene ◽  
North East ◽  
Tick Borne Encephalitis ◽  
Pcr Targeting

Tick-borne encephalitis (TBE) is a severe disease that has been endemic in north-east Italy since 1992. Over the past two decades, there has been an increase in the number of human cases reported in many European countries, including Italy. To assess the current TBE infection risk, questing ticks were collected from known TBE foci, as well as from a site in northern Italy where no human infections have been reported previously. A total of 1739 Ixodes ricinus (1485 nymphs and 254 adults) was collected and analysed for TBEV prevalence by a real-time RT-PCR targeting the 3′ untranslated region. Phylogenetic analyses of the partial envelope gene were conducted on two newly sequenced TBE virus (TBEV) strains and 28 previously published sequences to investigate the genealogical relationships of the circulating TBEV strains. These phylogenetic analyses confirmed a previous report that the European TBEV subtype is the only subtype circulating within the TBE foci in north-east Italy. Interestingly, nucleotide sequence analysis revealed a high degree of divergence (mean 2.54 %) between the TBEV strains recovered in the Italian province of Trento, despite the circulation of a single TBEV subtype. This elevated genetic variability within a single TBE focus may reflect local differences in the long-standing evolutionary dynamics of TBEV at this site relative to previously characterized sites, or more recent and continuous reintroduction of various TBEV strains.

scholarly journals Loss of migratory behaviour increases infection risk for a butterfly host

2015 ◽  
Vol 282 (1801) ◽  
pp. 20141734 ◽  
Author(s):  
Dara A. Satterfield ◽  
John C. Maerz ◽  
Sonia Altizer
Keyword(s):  
Human Activities ◽  
Wildlife Conservation ◽  
Protozoan Parasite ◽  
Infection Risk ◽  
Pathogen Transmission ◽  
Infection Prevalence ◽  
Evolutionary Divergence ◽  
Science Data ◽  
Long Distance ◽  
Southern Us

Long-distance animal migrations have important consequences for infectious disease dynamics. In some cases, migration lowers pathogen transmission by removing infected individuals during strenuous journeys and allowing animals to periodically escape contaminated habitats. Human activities are now causing some migratory animals to travel shorter distances or form sedentary (non-migratory) populations. We focused on North American monarch butterflies and a specialist protozoan parasite to investigate how the loss of migratory behaviours affects pathogen spread and evolution. Each autumn, monarchs migrate from breeding grounds in the eastern US and Canada to wintering sites in central Mexico. However, some monarchs have become non-migratory and breed year-round on exotic milkweed in the southern US. We used field sampling, citizen science data and experimental inoculations to quantify infection prevalence and parasite virulence among migratory and sedentary populations. Infection prevalence was markedly higher among sedentary monarchs compared with migratory monarchs, indicating that diminished migration increases infection risk. Virulence differed among parasite strains but was similar between migratory and sedentary populations, potentially owing to high gene flow or insufficient time for evolutionary divergence. More broadly, our findings suggest that human activities that alter animal migrations can influence pathogen dynamics, with implications for wildlife conservation and future disease risks.

scholarly journals Defining the risk landscape in the context of pathogen pollution: Toxoplasma gondii in sea otters along the Pacific Rim

2018 ◽  
Vol 5 (7) ◽  
pp. 171178 ◽  
Author(s):  
Tristan L. Burgess ◽  
M. Tim Tinker ◽  
Melissa A. Miller ◽  
James L. Bodkin ◽  
Michael J. Murray ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Population Density ◽  
Spatial Scale ◽  
Infection Risk ◽  
Pathogen Transmission ◽  
Small Scale ◽  
Infection Prevalence ◽  
Marine Animal ◽  
Sea Otter ◽  
Individual Level

Pathogens entering the marine environment as pollutants exhibit a spatial signature driven by their transport mechanisms. The sea otter ( Enhydra lutris ), a marine animal which lives much of its life within sight of land, presents a unique opportunity to understand land–sea pathogen transmission. Using a dataset on Toxoplasma gondii prevalence across sea otter range from Alaska to California, we found that the dominant drivers of infection risk vary depending upon the spatial scale of analysis. At the population level, regions with high T. gondii prevalence had higher human population density and a greater proportion of human-dominated land uses, suggesting a strong role for population density of the felid definitive host of this parasite. This relationship persisted when a subset of data were analysed at the individual level: large-scale patterns in sea otter T. gondii infection prevalence were largely explained by individual exposure to areas of high human housing unit density, and other landscape features associated with anthropogenic land use, such as impervious surfaces and cropping land. These results contrast with the small-scale, within-region analysis, in which age, sex and prey choice accounted for most of the variation in infection risk, and terrestrial environmental features provided little variation to help in explaining observed patterns. These results underscore the importance of spatial scale in study design when quantifying both individual-level risk factors and landscape-scale variation in infection risk.

scholarly journals Ecological Factors Characterizing the Prevalence of Bacterial Tick-Borne Pathogens in Ixodes ricinus Ticks in Pastures and Woodlands

2010 ◽  
Vol 76 (13) ◽  
pp. 4413-4420 ◽  
Author(s):  
Lénaïg Halos ◽  
Séverine Bord ◽  
Violaine Cotté ◽  
Patrick Gasqui ◽  
David Abrial ◽  
...  
Keyword(s):  
Forest Fragmentation ◽  
Ixodes Ricinus ◽  
Spotted Fever ◽  
Ecological Factors ◽  
Adult Tick ◽  
Reservoir Host ◽  
Host Community ◽  
Infection Prevalence ◽  
Spotted Fever Group ◽  
Reservoir Hosts

ABSTRACT Ecological changes are recognized as an important driver behind the emergence of infectious diseases. The prevalence of infection in ticks depends upon ecological factors that are rarely taken into account simultaneously. Our objective was to investigate the influences of forest fragmentation, vegetation, adult tick hosts, and habitat on the infection prevalence of three tick-borne bacteria, Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, and Rickettsia sp. of the spotted fever group, in questing Ixodes ricinus ticks, taking into account tick characteristics. Samples of questing nymphs and adults were taken from 61 pastures and neighboring woodlands in central France. The ticks were tested by PCR of pools of nymphs and individual adults. The individual infection prevalence was modeled using multivariate regression. The highest infection prevalences were found in adult females collected in woodland sites for B. burgdorferi sensu lato and A. phagocytophilum (16.1% and 10.7%, respectively) and in pasture sites for Rickettsia sp. (8.7%). The infection prevalence in nymphs was lower than 6%. B. burgdorferi sensu lato was more prevalent in woodlands than in pastures. Forest fragmentation favored B. burgdorferi sensu lato and A. phagocytophilum prevalence in woodlands, and in pastures, the B. burgdorferi sensu lato prevalence was favored by shrubby vegetation. Both results are probably because large amounts of edges or shrubs increase the abundance of small vertebrates as reservoir hosts. The Rickettsia sp. prevalence was maximal on pasture with medium forest fragmentation. Female ticks were more infected by B. burgdorferi sensu lato than males and nymphs in woodland sites, which suggests an interaction between the ticks and the bacteria. This study confirms the complexity of the tick-borne pathogen ecology. The findings support the importance of small vertebrates as reservoir hosts and make a case for further studies in Europe on the link between the composition of the reservoir host community and the infection prevalence in ticks.

scholarly journals Early detection of tick-borne encephalitis virus spatial distribution and activity in the province of Trento, northern Italy

2007 ◽  
Vol 1 (2) ◽  
pp. 169 ◽  
Author(s):  
Annapaola Rizzoli ◽  
Markus Neteler ◽  
Roberto Rosà ◽  
Walter Versini ◽  
Antonio Cristofolini ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Early Detection ◽  
Northern Italy ◽  
Encephalitis Virus ◽  
Tick Borne Encephalitis ◽  
Tick Borne Encephalitis Virus

scholarly journals THE IDENTIFICATION OF «NEW» PATHOGENS FOR FOCAL INFECTIONS IN IXODES TICKS ON THE TERRITORY OF TULA REGION

2018 ◽  
Vol 23 (4) ◽  
pp. 172-177
Author(s):  
T. V. Kozlova ◽  
T. I. Khomyakova ◽  
V. G. Dedkov ◽  
M. V. Safonova ◽  
L. S. Karan ◽  
...  
Keyword(s):  
Lyme Disease ◽  
Ixodes Ricinus ◽  
Mixed Infection ◽  
Dermacentor Reticulatus ◽  
Encephalitis Virus ◽  
Tick Borne Encephalitis ◽  
Ixodes Ticks ◽  
Pcr Method ◽  
Tick Borne Encephalitis Virus ◽  
Human Monocytic Ehrlichiosis

The most of ixodes ticks in Tula region belongs to the group of pasture mites. It is generally accepted to estimate the tick’s contamination by the tick-borne encephalitis virus and raoueti inducing Lyme Borellia. The aim of the present work was to educe the aetiologic agents of the set of potentially-enable infections out of ticks Dermacentor reticulatus, Ixodes ricinus and Ixodes сrenulatus collected at the different terrains of Tula Region by PCR method. The results: a considerable number of pathogenic rickettsiae R. raoultii was educes from the ticks D. reticulatus, which including them as the component of mixed infection together with the human monocytic ehrlichiosis agent. R. raoultii was determined in more than a half of the cases in ticks I. ricinus including the mixed infection together with ticks’ borreliosis virus and Kemerovo fever agent. Conclusion. The reasons, induced the quantity changes of the ticks’ distribution at Tula Region terrains, apparently promote the rise in frequency of the ticks contamination with the agents of herd tick-transmissive infection. It demand an infectiologist’s attention rise and dictate the necessity of the above mentioned diseases monitoring as well as Fr. tularensis, the tick-borne encephalitis virus and Lyme disease.

Climate change and tick-borne encephalitis in the Greater Alpine region.

2021 ◽  
pp. 354-359
Author(s):  
Franz Rubel
Keyword(s):  
Climate Change ◽  
Far East ◽  
Climate Change Impacts ◽  
Alpine Region ◽  
European Alps ◽  
Far East Of Russia ◽  
The Caucasus ◽  
Tick Density ◽  
Tick Borne Encephalitis ◽  
Tick Borne Disease

Abstract Tick-borne encephalitis (TBE) is a viral tick-borne disease. The distribution of human TBE cases ranges from the French departments bordering Germany through Central and Eastern Europe, the Caucasus and Kazakhstan to the Far East of Russia and China. In this expert opinion, TBE is described in the greater area of the European Alps, denoted as the Greater Alpine Region (GAR). It also includes reported tick-borne encephalitis cases and evidence for climate change impacts on tick density and distribution as well as the prevalence and intensity of TBE.

scholarly journals Relative Importance of Ixodes ricinus and Ixodes trianguliceps as Vectors for Anaplasma phagocytophilum and Babesia microti in Field Vole (Microtus agrestis) Populations

2008 ◽  
Vol 74 (23) ◽  
pp. 7118-7125 ◽  
Author(s):  
K. J. Bown ◽  
X. Lambin ◽  
G. R. Telford ◽  
N. H. Ogden ◽  
S. Telfer ◽  
...  
Keyword(s):  
United Kingdom ◽  
Ixodes Ricinus ◽  
Anaplasma Phagocytophilum ◽  
Babesia Microti ◽  
Infection Prevalence ◽  
Microtus Agrestis ◽  
Relative Importance ◽  
The United Kingdom ◽  
Ixodes Trianguliceps ◽  
Larval Burden

ABSTRACT The importance of Ixodes ricinus in the transmission of tick-borne pathogens is well recognized in the United Kingdom and across Europe. However, the role of coexisting Ixodes species, such as the widely distributed species Ixodes trianguliceps, as alternative vectors for these pathogens has received little attention. This study aimed to assess the relative importance of I. ricinus and I. trianguliceps in the transmission of Anaplasma phagocytophilum and Babesia microti among United Kingdom field voles (Microtus agrestis), which serve as reservoir hosts for both pathogens. While all instars of I. trianguliceps feed exclusively on small mammals, I. ricinus adults feed primarily on larger hosts such as deer. The abundance of both tick species and pathogen infection prevalence in field voles were monitored at sites surrounded with fencing that excluded deer and at sites where deer were free to roam. As expected, fencing significantly reduced the larval burden of I. ricinus on field voles and the abundance of questing nymphs, but the larval burden of I. trianguliceps was not significantly affected. The prevalence of A. phagocytophilum and B. microti infections was not significantly affected by the presence of fencing, suggesting that I. trianguliceps is their principal vector. The prevalence of nymphal and adult ticks on field voles was also unaffected, indicating that relatively few non-larval I. ricinus ticks feed upon field voles. This study provides compelling evidence for the importance of I. trianguliceps in maintaining these enzootic tick-borne infections, while highlighting the potential for such infections to escape into alternative hosts via I. ricinus.

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