CiteULike: neteler's Rizzoli

LAND USE CHANGE AND BIODIVERSITY CONSERVATION IN THE ALPS

C Chemini — 2007-12-18T09:53:55-00:00

Journal of Mountain Ecology, Vol. 7 (2003), pp. 1-7.

Human activities are changing the Planet, inducing high rates of extinction and a worldwide depletion of biological diversity at genetic, species, and ecosystem level. Biodiversity not only has an ethical and cultural value, but also plays a role in ecosystem function and, thus, ecosystem services, which are essential to civilization, economic production, and human wellbeing. The functional role of biodiversity is still poorly known; a minimum level of biodiversity is required for sustainable preservation of ecosystem functions, and as an insurance for future environmental changes. A large part of the biodiversity of the Alps is linked to an interaction between the natural environment and traditional human practices. At present, the change in land-use, with both intensification and abandonment, and other environmental and socioeconomic processes at different scales (urbanization, tourism, pol- lution, global change, etc.) are important forces of environmental change. Mowing and livestock grazing are prima- ry factors inhibiting woody plant succession in many areas of the Alps. Abandonment and fragmentation has result- ed in an expansion of ecotones and edge, with increase in tick-hosts and possibly changes in host-parasite interac- tions resulting from species concentration. The abandonment of mountain fields and meadows with a consequent expansion of shrubs and forests has caused a decrease of several grassland species, such as rock partridge Alectoris graeca; some arthropod communities of grassland have also been affected. Many forest species should find new opportunities, but in several cases the forests have become too dense for some species, such as for capercaille Tetrao urogallus. In the low altitude belts, a high species diversity co-occurs with human disturbance. Biodiversity studies require an interdisciplinary approach by the life sciences, and an interface to socioeconomic sciences. Preservation of species and landscape diversity cannot prescind from a dialogue between different actors and interests.

Anaplasmataceae in wild rodents and roe deer from Trento Province (northern Italy).

T Beninati — 2007-12-27T11:11:41-00:00

Eur J Clin Microbiol Infect Dis, Vol. 25, No. 10. (October 2006), pp. 677-678.

In recent decades, a number of intracellular bacterial strains within the family Anaplasmataceae have been identified around the globe. These bacteria include Anaplasma phagocytophilum, the causative agent of human granulocytic anaplasmosis and Anaplasma marginale, which causes disease in ruminants. Bacteria from this family often have a wide range of hosts, infecting both vertebrates and invertebrates. A. phagocytophilum is an obligate intracellular pathogen that parasitises the granulocytes of humans and animals, such as domesticated dogs, sheep, cows and horses, as well as wildlife species, such as deer and rodents [1]. Various strains of A. phagocytophilum have been identified, but only some are considered human pathogens [2]. ...

Tick infestation on roe deer in relation to geographic and remotely sensed climatic variables in a tick-borne encephalitis endemic area.

G Carpi — 2008-01-02T09:47:23-00:00

Epidemiology and Infection (17 December 2007), pp. 1-9.

Roe deer Capreolus capreolus are among the most important feeding hosts for the sheep tick Ixodes ricinus, thus contributing to the occurrence of tick-borne diseases in Europe. Tick-borne encephalitis (TBE), which is transmitted by co-feeding of larvae and nymphs on rodents, requires precise climatic conditions to occur. We used roe deer as sentinels for potential circulation of TBE virus in Northern Italy, by examining the association between tick infestation, occurrence of TBE human cases, geographical and climatic parameters. Tick infestation on roe deer, and particularly frequency of co-feeding, was clearly associated with the geographic location and the autumnal cooling rate. Consistently, TBE occurrence in humans was geographically related to co-feeding tick abundance. The surveillance of tick infestation on roe deer, combined with remotely sensed climatic data, could therefore be used as an inexpensive early risk assessment tool of favourable conditions for TBE emergence and persistence in humans.

Temporal Variation of Ixodes ricinus Intensity on the Rodent Host Apodemus flavicollis in Relation to Local Climate and Host Dynamics.

R Rosà — 2007-10-27T13:52:37-00:00

Vector Borne Zoonotic Dis, Vol. 7, No. 3. (2007), pp. 285-295.

The risk to humans of contracting tick-borne zoonotic diseases depends on the risk of a bite from an infected tick, which can be broken down into its component parts as the number of host-seeking ticks in the environment, in particular nymphs, and the prevalence of tick-borne pathogens they are carrying. In turn, the prevalence of tick-borne pathogens is dependent upon tick biting intensity on hosts that support transmission between ticks; namely rodents. These ticks once fed moult into the next life stage and search for the next blood meal, thus posing a zoonotic risk. Here, we analyse tick biting intensity on rodents in a known tick-borne encephalitis (TBE) focus in Trentino (northern Italy). We examine patterns of tick demography and the influence of host densities and climate on ticks' generation time, development rates, tick density and intensity. During the period 2000-2004, a population of the yellow-necked mouse, Apodemus flavicollis, the most important TBE transmission host, was intensively monitored. Ticks feeding on individual rodents were counted, distinguishing between the larval and nymph life-stages. Local temperature and relative humidity was calculated using both data-loggers in the field site and regional weather stations. We investigated which factors had a predictive value both on feeding tick intensity and on the overall density of larvae or nymphs feeding on rodents in a year. We observed a negative effect of rodent density on tick intensity, while temperature influenced positively both larvae and nymph intensity. Overall larval density was higher in the years and trapping grids where rodent density was higher, while for nymphs no such effect was observed. The best explanatory variable for nymph density was the larval density in the previous year, confirming the discrete nature of tick demography. This provides important information in terms of monitoring the risk to humans of acquiring pathogen-infected ticks.

West Nile Virus Circulation Detected in Northern Italy in Sentinel Chickens.

Annapaola Rizzoli — 2007-09-13T14:31:42-00:00

Vector Borne Zoonotic Dis (3 September 2007)

Ninety percent (56/62) of sentinel chickens introduced to two regions within the Italian Alps seroconverted to West Nile virus (WNV) during the summer of 2005, showing a range of antibody titres from 1/20 to 1/320 in a virus neutralization test. Neutralization specificity for WNV antibodies was confirmed on an additional 34 sera that were tested in parallel against WNV (16/34 seropositivity), Usutu virus (3/34 seropositivity) and Koutango virus. The geometric mean neutralizing titre (GMT) calculated for WN-specific antibodies was 33.68 and did not differ significantly amongst sample sites, although the overall results indicate more active circulation of WNV at the higher elevations. Such high levels of seroconversion raise the possibility that many chickens may have been exposed to virus via routes other than mosquito transmission. No chickens or any other local animals were associated with illness due to WNV implying that WNV, and to a much lower extent Usutu virus, circulate harmlessly amongst wildlife species in northern Italy from late May onwards until early autumn.

Early detection of TBEv spatial distribution and activity in the Province of Trento assessed using serological and remotely-sensed climatic data

A Rizzoli — 2007-05-05T20:13:14-00:00

Geospatial Health, Vol. 1, No. 2. (May 2007), pp. 169-176.

New human cases of tick borne encephalitis (TBE) have recently been recorded outside the recognized foci of this disease, i.e. in the province of Trento in northern Italy. In order to predict the highest risk areas for increased tick-borne encephalitis virus activity, we have combined cross-sectional serological data, obtained from 459 domestic goats, with analysis of the autumnal cooling rate based on Moderate Resolution Imaging Spectroradiometer (MODIS) Land Surface Temperature (LST) data. A significant relationship between finding antibodies against the virus in serum (seroprevalence) in goats and the autumnal cooling rate was detected, indicating that the transmission intensity of the virus does not only vary spatially, but also in relation to climatic factors. Virus seroprevalence in goats was correlated with the occurrence of tick-borne encephalitis in humans and also with the average number of forestry workers' tick bites, demonstrating that serological screening of domestic animals, combined with an analysis of the autumnal cooling rate, can be used as early-warning predictors of tick-borne encephalitis risk in humans.

Spatial aspects of disease dynamics

G Hess — 2007-01-24T17:34:47-00:00

(2002), pp. 102-118.

Prevalence of Borrelia burgdorferi s.l. and Anaplasma phagocytophilum in the wood tick Ixodes ricinus in the Province of Trento, Italy

B Mantelli — 2006-10-27T13:52:29-00:00

European Journal of Clinical Microbiology & Infectious Diseases

In Europe, lyme borreliosis (LB) and human granulocytic anaplasmosis (HGA) are emerging tick-borne zoonoses. Both are transmitted by the hard tick Ixodes ricinus, which is widespread in the Province of Trento in northeastern Italy [1]. The risk of infection with the agents of LB and HGA is dependent on local tick distribution and abundance, and the proportion of infected ticks, which are in turn correlated with the type of habitat and the density of vertebrate reservoir hosts. The etiological agent of LB, the spirochete Borrelia burgdorferi s.l., causes a wide range of clinical symptoms, and levels of pathogenicity are associated with different genospecies. In Italy, reports of LB infection have been increasing, especially in the northeastern regions of the country [2, 3].

Ixodes ricinus (Acari: Ixodidae) infestation on roe deer (Capreolus capreolus) in Trentino, Italian Alps.

C Chemini — 2006-08-02T15:34:06-00:00

Parassitologia, Vol. 39, No. 1. (March 1997), pp. 59-63.

The most important tick-deer system potentially supporting the epidemiology of Lyme disease in the Italian Alps is that regarding Ixodes ricinus (L.) and roe deer (Capreolus capreolus L.). In this study, the pattern of tick infestation on 562 male roe deer harvested in September 1994 in 56 game districts of Trentino, Northern Italy, was assessed. The prevalence and density of infestation by I. ricinus were analyzed by a model based on classification and regression trees (CART), using both discrete and continuous variables concerning environmental and host parameters. The model discriminated attitude and host density as the 2 variables having the greatest effect on the prevalence and density of infestation of deer; the levels of infestation were higher at an altitude below 1125 m or at roe deer densities over 8.5 head per 100 ha. The density of tick infestation tended to be higher in older roe deer.

Empirical evidence for key hosts in persistence of a tick-borne disease.

SE Perkins — 2006-07-11T07:43:18-00:00

Int J Parasitol, Vol. 33, No. 9. (August 2003), pp. 909-917.

An important epidemiological consequence of aggregated host-parasite associations occurs when parasites are vectors of pathogens. Those hosts that attract many vectors will tend to be the focus of transmission. But to what extent, and can we identify characteristics of these key hosts? We investigated these questions with respect to the host-tick relationship of the yellow-necked mouse, Apodemus flavicollis, a critical host in the maintenance of the zoonotic disease, tick-borne encephalitis. Transmission of the virus occurs when ticks feed in a 'co-feeding' aggregation. Thus, the number and frequency of co-feeding groups provides an estimate of the potential rate of virus transmission. We recorded the spatio-temporal variations in co-feeding on a population of rodents in conjunction with recording individual host characteristics. Using Lorenz curves, we revealed conformation of tick-borne encephalitis transmission potential to the 20/80 Rule, where the 20% of hosts most infested with ticks were accountable for 80% of transmission potential. Hosts in the transmission cohort were identified as the sexually mature males of high body mass. Therefore control efforts targeted at this group would substantially reduce transmission potential compared to non-targeted control of the population, which resulted in a linear reduction in transmission potential. Focusing on the 'wrong' functional group would have little impact upon transmission potential until a considerable proportion of the population had been subject to control. However, individuals can change their functional status over time making it difficult to predict the contribution of these individuals to future transmission.

The ecology of tick-borne infections in wildlife reservoirs

SE Randolph — 2006-04-02T21:57:25-00:00

(2002), pp. 119-138.

Hantavirus and arenavirus antibody prevalence in rodents and humans in Trentino, Northern Italy.

H Kallio-Kokko — 2006-01-02T12:33:48-00:00

Epidemiology and Infection (22 December 2005), pp. 1-7.

The spatial and temporal distribution of hantavirus and arenavirus antibody-positive wild rodents in Trentino, Italy, was studied using immunofluorescence assays (IFA) in two long-term sites trapped in 2000-2003, and six other sites trapped in 2002. The overall hantavirus seroprevalence in the bank voles, Clethrionomys glareolus (n=229) screened for Puumala virus (PUUV) antibodies was 0.4%, and that for Apodemus flavicollis mice (n=1416) screened for Dobrava virus (DOBV) antibodies was 0.2%. Antibodies against lymphocytic choriomeningitis virus (LCMV) were found in 82 (5.6%) of the 1472 tested rodents; the seroprevalence being 6.1% in A. flavicollis (n=1181), 3.3% in C. glareolus (n=276), and 14.3% in Microtus arvalis (n=7). Of the serum samples of 488 forestry workers studied by IFA, 12 were LCMV-IgG positive (2.5%) and one DOBV-IgG positive (0.2%), however, the latter could not be confirmed DOBV-specific with a neutralization assay. Our results show a widespread distribution but low prevalence of DOBV in Trentino, and demonstrate that the arenavirus antibodies are a common finding in several other rodent species besides the house mouse.

Geographical information systems and bootstrap aggregation (bagging) of tree-based classifiers for Lyme disease risk prediction in Trentino, Italian Alps.

A Rizzoli — 2005-04-28T09:22:23-00:00

J Med Entomol, Vol. 39, No. 3. (May 2002), pp. 485-492.

The risk of exposure to Lyme disease in the province of Trento, Italian Alps, was predicted through the analysis of the distribution of Ixodes ricinus (L.) nymphs infected with Borrelia burgdorferi s.l. with a model based on bootstrap aggregation (bagging) of tree-based classifiers within a geographical information system (GIS). Data on L ricinus density assessed by dragging the vegetation in 438 sites during 1996 were cross-correlated with the digital cartography of a GIS, which included the variables altitude, exposure and slope, substratum, vegetation type and roe deer density. Ticks were more abundant at altitudes below 1,300 m a.s.l., in the presence of limestone and vegetation cover with thermophile deciduous forests and high densities of roe deer. A bootstrap aggregation procedure (bagging) was used to produce a model for the prediction of tick occurrence, the accuracy of which was tested on actual tick counts assessed by a further dragging campaign carried out during 1997 to determine infection prevalence and resulted in average 77%. Other tests of the model were made on additional and independent data sets. The prevalence of infection with Borrelia burgdorferi s.l, determined by polymerase chain reaction on 2,208 nymphs collected by random dragging in 245 transects selected within eight areas where the model predicted the occurrence of I. ricinus during 1997, was 17.5% and was positively correlated to tick abundance and roe deer density. These findings were used to relate the output of the bagged model (probability of tick occurrence) to the density of infected nymphs through a stepwise model selection procedure and thus to produce a GIS digital map of the probability distribution of infected nymphs in the Province of Trento at high resolution scale (50 by 50-m cell resolution). The application of the bagging procedure increased the accuracy of the prediction made by a single classification tree, a well-known classification method for the analysis of epidemiological data.

Tick-borne encephalitis virus in northern Italy: molecular analysis, relationships with density and seasonal dynamics of Ixodes ricinus.

PJ Hudson — 2005-04-28T09:21:08-00:00

Med Vet Entomol, Vol. 15, No. 3. (September 2001), pp. 304-313.

Ixodes ricinus ticks were collected from dragging vegetation and from shot roe deer in the province of Trento and Belluno in northern Italy. Ticks were pooled for analyses and from 1060 pools of ticks collected in the province of Belluno and 12390 tick samples collected in Trentino, four proved positive by immunofluorescence microscopy using a tick-borne encephalitis (TBE)-specific antiserum. The identity of the virus isolates was determined by RT-PCR cycle sequencing and they were all found to be closely similar (> 98% nucleotide identity) to typical western European TBE complex viruses as found in Austria. The isolates from Trentino differed from the Neudorfl strain of western European TBE virus at eight nucleotide positions but as these nucleotide substitutions were all synonymous, there were no amino acid changes. These results imply that the virus isolates in Trentino have changed slightly from the typical European strains isolated in nearby Austria. The abundance of questing ticks and ticks feeding on roe deer was greater in TBE positive hunting districts than in hunting districts where TBE complex viruses were only probable or believed to be absent. In TBE positive and probable districts synchrony in the seasonal dynamics of larvae and nymphs of L. ricinus was observed. This study provides evidence to suggest that roe deer may have an important role to play in the maintenance of tick density and in the persistence of TBE virus.

Ixodes ricinus, transmitted diseases and reservoirs

A Rizzoli — 2005-04-27T19:51:32-00:00

Parassitologia, Vol. 46, No. 1-2. (June 2004), pp. 119-122.

The tick Ixodes ricinus has been recorded in most Italian regions especially in thermo-mesophilous woods and shrubby habitats where the relative humidity allow the tick to complete its 3 year developmental cycle, as predicted for the European climatic ranges. This tick acts both as vector and reservoir for a series of wildlife zoonotic pathogens, especially the agents of Lyme diseases, Tick borne encephalitis and Human Granulocytic Ehrlichiosis, which are emerging in most of Europe. To assess the spatial distribution of these pathogens and the infection risk for humans and animals within the territory of the Province of Trento, we carried out a long term study using a combination of eco-epidemiological surveys and mathematical modelling. An extensive tick collection with a GIS based habitat suitability analysis allowed us to identify the areas where tick occurs at various density. To identify the areas with higher infection risk, we estimated the values of R0 for Borrelia burgdorferi s.l., TBE virus and Anaplasma phagocytophila under different ecological conditions. We assessed the infection prevalence in the vector and in the wildlife reservoir species that play a central role in the persistence of these infections, ie the small mammals A. flavicollis and C. glareolus. We also considered the double effect of roe deer (Capreolus capreolus) which act as reservoir for A. phagocytophila but is an incompetent host for B. burgdorferi and TBE virus, thus reducing the infection prevalence in ticks of these last two pathogens. Infection prevalence with B. burgdorferi and A. phagocytophila in the vector was assessed by PCR screening 1212 I. ricinus nymphs collected by dragging in six main study areas during 2002. The mean infection prevalence recorded was 1.32% for B. burgdorferi s.l. and 9.84% for A. phagocytophila. Infection prevalence in nymphs with TBE virus, as assessed in a previous study was 0.03%. Infection prevalence in rodents was assessed by screening (with ELISA and PCR) tissues and blood samples collected from 367 rodent individuals trapped extensively during 2002 within 6 main study areas. A. flavicollis (N=238) was found to be infected with all three pathogens investigated, with infection prevalence ranging from 3.3% for TBE virus to 11.7% for A. phagocytophila, and 16.6% with B. burgdorferi s.l. C. glareolus (N=108) showed an infection prevalence of 6.5% with A. phagocytophila and 12.7% with B. burgdorferi s.l., while no individuals were infected with TBE virus. We also screened 98 spleen samples collected from roe deer with PCR, resulting in a mean prevalence of infection with A. phagocytophila of 19.8%. Using a deterministic model we explored the condition for diseases persistence under different rodent and roe deer densities. R0 values resulted largely above 1 for B. burgdorferi s.l. in the vast majority of the areas classified as suitable for I. ricinus occurrence in Trentino, while the condition for TBE persistence appeared to be more restricted by a combination of climatic condition and host densities.

GIS and the Random Forest Predictor: Integration in R for Tick-Borne Disease Risk Assessment

Cesare Furlanello — 2005-04-27T19:43:30-00:00

We discuss how sophisticated machine learning methods may be rapidly integrated within a GIS for the development of new approaches in landscape epidemiology. A multitemporal predictive map is obtained by modeling in R, analyzing geodata and digital maps in GRASS, and managing biodata samples and weather data in PostgreSQL. In particular, we present a risk mapping system for tick-borne diseases, applied to model the risk of exposure to Lyme borreliosis and tick-borne encephalitis (TBE) in...