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1.
Vet Parasitol ; 249: 2-16, 2018 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-29279082

RESUMEN

Ticks are economically and medically important ectoparasites due to the injuries inflicted through their bite, and their ability to transmit pathogens to humans, livestock, and wildlife. Whereas hard ticks have been intensively studied, little is known about soft ticks, even though they can also transmit pathogens, including African Swine Fever Virus (ASFV) affecting domestic and wild suids or Borrelia bacteria causing tick-borne relapsing fever (TBRF) in humans. We thus developed a regional model to identify suitable spatial areas for a community of nine Ornithodoros tick species (O. erraticus, O. sonrai, O. alactagalis, O. nereensis, O. tholozani, O. papillipes, O. tartakovskyi, O. asperus, O. verrucosus), which may be of medical and veterinary importance in the Western Palearctic region. Multi-Criteria Decision Analysis was used due to the relative scarcity of high-quality occurrence data. After an in-depth literature review on the ecological requirements of the selected tick community, five climate-related factors appeared critical for feeding activity and tick development: (i) a spring temperature exceeding 10°C to induce the end of winter soft tick quiescent period, (ii) a three-months summer temperature above 20°C to allow tick physiological activities, (iii) annual precipitation ranging from 60mm to 750mm and, in very arid areas, (iv) dry seasons interrupted by small rain showers to maintain minimum moisture inside their habitat along the year or (v) residual water provided by perennial rivers near habitats. We deliberately chose not to include biological factors such as host availability or vegetation patterns. A sensitivity analysis was done by performing multiple runs of the model altering the environmental variables, their suitability function, and their attributed weights. To validate the models, we used 355 occurrence data points, complemented by random points within sampled ecoregions. All models indicated suitable areas in the Mediterranean Basin and semi-desert areas in South-West and Central Asia. Most variability between models was observed along northern and southern edges of highly suitable areas. The predictions featured a relatively good accuracy with an average Area Under Curve (AUC) of 0.779. These first models provide a useful tool for estimating the global distribution of Ornithodoros ticks and targeting their surveillance in the Western Palearctic region.


Asunto(s)
Distribución Animal , Ecosistema , Modelos Biológicos , Ornithodoros/fisiología , Animales , Lluvia , Estaciones del Año , Temperatura
2.
Vet Parasitol Reg Stud Reports ; 14: 41-49, 2018 12.
Artículo en Inglés | MEDLINE | ID: mdl-31014735

RESUMEN

Species distribution modelling is a very useful tool in vector management. Ticks are vectors of various pathogens which cause serious problems in livestock production in tropical countries. They have a high dispersal potential which is mainly facilitated by the movement of animals from one area to another. In light of the observed geographic expansion of Rhipicephalus microplus in Zimbabwe, we used species distribution modelling techniques to identify areas which may provide suitable habitats for the occurrence of this invasive tick species as well as the autochthonous Rhipicephalus decoloratus. Our results suggest that, despite the geographic expansion of R. microplus, climate will continue to be a limiting factor for the further expansion of this tick species. We expect its distribution to be restricted to the most favourable areas in the eastern and northern parts. The greater part of Zimbabwe is suitable for R. decoloratus, although in areas where R. microplus occurs, displacement of the former by the latter will be expected to occur. A heterogeneous climate, unregulated movement of cattle and episodic droughts are suggested to be possible factors for the continued existence of R. microplus and R. decoloratus in Zimbabwe and the partial displacement.


Asunto(s)
Distribución Animal , Enfermedades de los Bovinos/epidemiología , Ecosistema , Rhipicephalus/fisiología , Infestaciones por Garrapatas/veterinaria , Animales , Bovinos , Enfermedades de los Bovinos/parasitología , Clima , Ganado , Infestaciones por Garrapatas/epidemiología , Zimbabwe/epidemiología
3.
Transbound Emerg Dis ; 63(3): 333-47, 2016 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-25377758

RESUMEN

African buffaloes (Syncerus caffer) are reservoir hosts of Southern African Territories (SAT) foot-and-mouth disease (FMD) virus strains. In South Africa, infected buffaloes are found in the FMD-infected zone comprising the Kruger National Park (KNP) and its adjoining reserves. When these buffaloes stray into livestock areas, they pose a risk of FMD transmission to livestock. We assessed 645 records of stray buffalo events (3124 animals) from the FMD infected zone during 1998-2008 for (i) their temporal distribution, (ii) group size, (iii) age and gender composition, (iv) distance from the infected zone fence and (v) outcome reported for each event. A maximum entropy model was developed to evaluate spatial predictors of stray buffalo events and assess current disease control zones. Out of all buffaloes recorded straying, 38.5% escaped from the FMD infected zone during 2000/2001, following floods that caused extensive damage to wildlife fences. Escape patterns were not apparently influenced by season. The median size of stray groups was a single animal (IQR [1-2]). Adult animals predominated, comprising 90.4% (620/686) of the animals for which age was recorded. Of the 315 events with accurate spatial information, 204 (64.8%) were recorded within 1 km from the FMD infected zone. During late winter/spring (June-October), stray buffaloes were found significantly closer to the FMD infected zone (median = 0.3 km, IQR [0.1-0.6]). Less than 13% (40/315) of stray groups reached the FMD protection zone without vaccination, posing a higher risk of spreading FMD to these more susceptible livestock. Model outputs suggest that distance from the FMD infected zone, urban areas and permanent water sources contributed almost 85% to the spatial probability of stray buffalo events. Areas with a high probability for stray buffalo events were well covered by current disease control zones, although FMD risk mitigation could be improved by expanding the vaccination zone in certain areas.


Asunto(s)
Distribución Animal , Búfalos , Enfermedades de los Bovinos/transmisión , Virus de la Fiebre Aftosa/fisiología , Fiebre Aftosa/transmisión , Animales , Búfalos/fisiología , Bovinos , Enfermedades de los Bovinos/virología , Femenino , Fiebre Aftosa/prevención & control , Fiebre Aftosa/virología , Masculino , Sudáfrica
4.
Prev Vet Med ; 118(1): 8-21, 2015 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-25466219

RESUMEN

Rhipicephalus microplus is one of the most widely distributed and economically important ticks, transmitting Babesia bigemina, B. bovis and Anaplasma marginale. It was recently introduced to West Africa on live animals originating from Brazil. Knowing the precise environmental suitability for the tick would allow veterinary health officials to draft vector control strategies for different regions of the country. To test the performance of modelling algorithms and different sets of environmental explanatory variables, species distribution models for this tick species in Benin were developed using generalized linear models, linear discriminant analysis and random forests. The training data for these models were a dataset containing reported absence or presence in 104 farms, randomly selected across Benin. These farms were sampled at the end of the rainy season, which corresponds with an annual peak in tick abundance. Two environmental datasets for the country of Benin were compared: one based on interpolated climate data (WorldClim) and one based on remotely sensed images (MODIS). The pixel size for both environmental datasets was 1 km. Highly suitable areas occurred mainly along the warmer and humid coast extending northwards to central Benin. The northern hot and drier areas were found to be unsuitable. The models developed and tested on data from the entire country were generally found to perform well, having an AUC value greater than 0.92. Although statistically significant, only small differences in accuracy measures were found between the modelling algorithms, or between the environmental datasets. The resulting risk maps differed nonetheless. Models based on interpolated climate suggested gradual variations in habitat suitability, while those based on remotely sensed data indicated a sharper contrast between suitable and unsuitable areas, and a patchy distribution of the suitable areas. Remotely sensed data yielded more spatial detail in the predictions. When computing accuracy measures on a subset of data along the invasion front, the modelling technique Random Forest outperformed the other modelling approaches, and results with MODIS-derived variables were better than those using WorldClim data. The high environmental suitability for R. microplus in the southern half of Benin raises concern at the regional level for animal health, including its potential to substantially alter transmission risk of Babesia bovis. The northern part of Benin appeared overall of low environmental suitability. Continuous surveillance in the transition zone however remains relevant, in relation to important cattle movements in the region, and to the invasive character of R. microplus.


Asunto(s)
Demografía , Modelos Biológicos , Rhipicephalus/fisiología , Medición de Riesgo/métodos , África Occidental , Agricultura , Algoritmos , Animales , Vectores Arácnidos , Bovinos/parasitología , Clima , Bases de Datos Factuales , Ecosistema , Modelos Lineales , Análisis Espacial
6.
J Med Entomol ; 50(2): 237-43, 2013 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-23540109

RESUMEN

Mosquito (Diptera: Culicidae) distribution data from a recent inventory of native and invading mosquito species in Belgium were compared with historical data from the period 1900-1960 that were retrieved from a revision of the Belgian Culicidae collection at the Royal Belgian Institute of Natural Sciences. Both data sets were used to investigate trends in mosquito species richness in several regions in Belgium. The relative change in distribution area of mosquito species was particularly important for species that use waste waters and used tires as larval habitats and species that recently shifted their larval habitat to artificial larval habitats. More importantly, several of these species are known as vectors of arboviruses and Plasmodium sp. and the apparent habitat shift of some of them brought these species in proximity to humans. Similar studies comparing current mosquito richness with former distribution data retrieved from voucher specimens from collections is therefore encouraged because they can generate important information concerning health risk assessment at both regional and national scale.


Asunto(s)
Distribución Animal , Biota , Culicidae/fisiología , Ecosistema , Insectos Vectores/fisiología , Animales , Infecciones por Arbovirus/transmisión , Arbovirus/fisiología , Bélgica , Culicidae/clasificación , Culicidae/parasitología , Culicidae/virología , Humanos , Insectos Vectores/clasificación , Insectos Vectores/parasitología , Insectos Vectores/virología , Larva/clasificación , Larva/fisiología , Malaria/transmisión , Plasmodium/fisiología , Dinámica Poblacional , Estaciones del Año , Factores de Tiempo
7.
Bull Entomol Res ; 103(2): 193-203, 2013 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-22971463

RESUMEN

To advance our restricted knowledge on mosquito biodiversity and distribution in Belgium, a national inventory started in 2007 (MODIRISK) based on a random selection of 936 collection points in three main environmental types: urban, rural and natural areas. Additionally, 64 sites were selected because of the risk of importing a vector or pathogen in these sites. Each site was sampled once between May and October 2007 and once in 2008 using Mosquito Magnet Liberty Plus traps. Diversity in pre-defined habitat types was calculated using three indices. The association between species and environmental types was assessed using a correspondence analysis. Twenty-three mosquito species belonging to traditionally recognized genera were found, including 21 indigenous and two exotic species. Highest species diversity (Simpson 0.765) and species richness (20 species) was observed in natural areas, although urban sites scored also well (Simpson 0.476, 16 species). Four clusters could be distinguished based on the correspondence analysis. The first one is related to human modified landscapes (such as urban, rural and industrial sites). A second is composed of species not associated with a specific habitat type, including the now widely distributed Anopheles plumbeus. A third group includes species commonly found in restored natural or bird migration areas, and a fourth cluster is composed of forest species. Outcomes of this study demonstrate the effectiveness of the designed sampling scheme and support the choice of the trap type. Obtained results of this first country-wide inventory of the Culicidae in Belgium may serve as a basis for risk assessment of emerging mosquito-borne diseases.


Asunto(s)
Biodiversidad , Culicidae , Animales , Bélgica , Ambiente
8.
J Med Entomol ; 49(6): 1226-32, 2012 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-23270149

RESUMEN

Adults of an exotic mosquito, Aedes (Finlaya) koreicus (Edwards) (Diptera: Culicidae) were identified by morphology and genotyping from one site in Belgium in 2008. In late summer of that year, the occurrence of adults and immature stages reconfirmed its presence. This is the first record of this species outside its native range and in particular in Europe. Two subsites of the original location were prospected from April until October 2009 with different traps to evaluate the extent of its presence and establishment in the area and to understand the dynamics of the species' population. Next to Ae. koreicus, 15 other mosquito species were collected. Adult individuals of Ae. koreicus were found from May to September and larvae were still found early October. Larvae were mainly retrieved from artificial containers both in 2008 as in 2009. Containers with eggs and/or larvae were found up to 4 km away from the initial location, indicating the species is spreading locally. Though the introduction route is unknown, it may have occurred via international trade as a large industrial center was located nearby. A comparison of different climatic variables between locations in Belgium with Ae. koreicus and putative source locations in South Korea, revealed similarities between winter temperatures and the number of freezing days and nights in four consecutive years (2004-2008), while humidity and precipitation values differed strongly. The introduction of a new potential disease vector into Europe seems to be a result of proper entrance points, created by intense worldwide trade and suitable environmental conditions.


Asunto(s)
Aedes , Especies Introducidas , Animales , Bélgica , Clima , Femenino , Masculino , Dinámica Poblacional
9.
Exp Appl Acarol ; 58(4): 441-52, 2012 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-22689006

RESUMEN

The cattle tick Rhipicephalus microplus is currently invading the West African region, and little information is available on the spread of this exotic tick in this region. We set out a country-wide field survey to determine its current distribution in Benin. Ticks were collected on cattle from 106 farms selected by random sampling covering all regions of the country. Rhipicephalus annulatus was found on 70 % of all farms, R. decoloratus on 42 %, R. geigyi on 58 %, and R. microplus on 49 %. There is a clear geographic separation between the indigenous Rhipicephalus species and R. microplus. Rhipicephalus annulatus occurs mainly in the northern departments, but it was also observed in lower numbers in locations in the south. The presence of R. decoloratus is limited to the northern region, and in most locations, this tick makes up a small proportion of the collected ticks. The tick R. geigyi tends to be dominant, but occurs only in the four northern departments. The observations concerning R. microplus are entirely different, this species occurs in the southern and central region. The results of this survey confirm the invasive character and displacement properties of R. microplus, since in less than a decade it has colonized more than half of the country and has displaced indigenous ticks of the same genus in many of the sampled locations.


Asunto(s)
Enfermedades de los Bovinos/epidemiología , Enfermedades de los Bovinos/parasitología , Rhipicephalus/fisiología , Infestaciones por Garrapatas/veterinaria , Animales , Benin/epidemiología , Bovinos , Geografía , Densidad de Población , Infestaciones por Garrapatas/epidemiología
10.
Parasitology ; 139(14): 1831-42, 2012 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-22717001

RESUMEN

In the last decade, mobile technology offered new opportunities and challenges in animal health surveillance. It began with the use of basic mobile phones and short message service (SMS) for disease reporting, and the development of smartphones and other mobile tools has expanded the possibilities for data collection. These tools assist in the collection of data as well as geo-referenced mapping of diseases, and mapping, visualization and identification of vectors such as ticks. In this article we share our findings about new technologies in the domain of animal health surveillance, based on several projects using a wide range of mobile tools, each with their specific applicability and limitations. For each of the tools used, a comprehensive overview is given about its applicability, limitations, technical requirements, cost and also the perception of the users.The evaluation of the tools clearly shows the importance of selecting the appropriate tool depending on the envisaged data to be collected. Accessibility, visualization and cost related to data collection differ significantly among the tools tested. This paper can thus be seen as a practical guide to the currently available tools.


Asunto(s)
Teléfono Celular , Recolección de Datos/instrumentación , Recolección de Datos/métodos , Programas Informáticos , África/epidemiología , Animales , Especies Introducidas , Vigilancia de la Población/métodos , Enfermedades por Picaduras de Garrapatas/epidemiología , Garrapatas/fisiología
11.
J Med Entomol ; 48(4): 924-8, 2011 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-21845955

RESUMEN

For the majority of native species, human-created habitats provide a hostile environment that prevents their colonization. However, if the conditions encountered in this novel environment are part of the fundamental niche of a particular species, these low competitive environments may allow strong population expansion of even rare and stenotopic species. If these species are potentially harmful to humans, such anthropogenic habitat alterations may impose strong risks for human health. Here, we report on a recent and severe outbreak of the viciously biting and day-active mosquito Anopheles plumbeus Stephens, 1828, that is caused by a habitat shift toward human-created habitats. Although historic data indicate that the species was previously reported to be rare in Belgium and confined to natural forest habitats, more recent data indicate a strong population expansion all over Belgium and severe nuisance at a local scale. We show that these outbreaks can be explained by a recent larval habitat shift of this species from tree-holes in forests to large manure collecting pits of abandoned and uncleaned pig stables. Further surveys of the colonization and detection of other potential larval breeding places of this mosquito in this artificial environment are of particular importance for human health because the species is known as a experimental vector of West Nile virus and a potential vector of human malaria.


Asunto(s)
Anopheles/fisiología , Insectos Vectores/fisiología , Fiebre del Nilo Occidental/transmisión , Animales , Bélgica , Ecosistema , Actividades Humanas , Humanos , Larva , Crecimiento Demográfico , Fiebre del Nilo Occidental/virología , Virus del Nilo Occidental
12.
Prev Vet Med ; 100(1): 15-28, 2011 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-21496932

RESUMEN

Data-driven models for the prediction of bluetongue vector distributions are valuable tools for the identification of areas at risk for bluetongue outbreaks. Various models have been developed during the last decade, and the majority of them use linear discriminant analysis or logistic regression to infer vector-environment relationships. This study presents a performance assessment of two established models compared to a distribution model based on a promising ensemble learning technique called Random Forests. Additionally, the impact of false absences, i.e. data records of suitable vector habitat that are, for various reasons, incorrectly labelled as absent, on the model outcome was assessed using alternative calibration-validation schemes. Three reduction methods were applied to reduce the number of false absences in the calibration data, without loss of information on the environmental gradient of suitable vector habitat: random reduction and stratified reduction based on the distance between absence and presence records in geographical (Euclidean distance) or environmental space (Mahalanobis distance). The results indicated that the predicted vector distribution by the Random Forest model was significantly more accurate than the vector distributions predicted by the two established models (McNemar test, p<0.01) when the calibration data were not reduced with respect to false absences. The performance of the established models, however, increased considerably by application of stratified false absence reductions. Model validation revealed no significant difference between the performance of the three distinct Culicoides imicola distribution models for the majority of alternative stratified reduction schemes. The main conclusion of this study is that the application of Random Forests, or linear discriminant analysis and logistic regression on the condition that calibration data were first reduced on geographical or environmental information, potentially lead toward better vector distribution models.


Asunto(s)
Virus de la Lengua Azul/aislamiento & purificación , Ceratopogonidae/crecimiento & desarrollo , Ceratopogonidae/virología , Insectos Vectores/crecimiento & desarrollo , Insectos Vectores/virología , Modelos Biológicos , Animales , Lengua Azul/epidemiología , Lengua Azul/transmisión , Métodos Epidemiológicos , Curva ROC , Sensibilidad y Especificidad , Ovinos , España
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