Experimental Study of the Mechanical Transmission of Rabbit Hemorrhagic Disease Virus (RHDV2/b) by Aedes albopictus (Diptera: Culicidae) and Phlebotomus papatasi (Diptera: Psychodidae)

Rabbit hemorrhagic disease (RHD) is caused by a lagovirus mainly affecting European rabbits (Oryctolagus cuniculus), although other European and North American lagomorph species are also susceptible to fatal infection by the new viral variant RHDV2/b. In the present work, direct mechanical transmission of the rabbit hemorrhagic disease virus (RHDV2/b variant) by the hematophagous Diptera Aedes albopictus (Skuse) (Diptera: Culicidae) and the sand fly Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae) was tested. For each species, six and three laboratory rabbits were exposed to bites of dipterous females partially fed on RHDV2/b viral suspension 2 h and 24 h prior to exposure, respectively. The rabbits were then monitored for clinical changes and mortality for 35 d, and seroconversion was assessed by indirect ELISA. No rabbit died or showed clinical signs of disease, and seroconversion was recorded in two rabbits challenged with P. papatasi females fed the viral suspension 2 h prior to exposure. The number of RHDV2/b RNA copies/female was higher in Ae. albopictus than in P. papatasi but the decrease over time of RNA load in Ae. albopictus was greater than that in P. papatasi. The results of this study suggest the inability of Ae. albopictus to serve as a direct mechanical vector of RHDV2/b, but sand flies could play a role in the local transmission of RHD.

Changes in European wild rabbit population dynamics and the epidemiology of rabbit haemorrhagic disease (RHD) in response to artificially increased viral transmission

European wild rabbit (Oryctolagus cuniculus) populations are severely affected by rabbit haemorrhagic disease (RHD), currently aggravated by the spread of the new lagovirus serotype RHDV2 that replaced the classical RHDV strains (RHDV/RHDVa). This virus causes high mortality in both adult and young rabbits and to date, there is no management tool to effectively reduce its impact in wild rabbit populations. This hinders the success of common strategies, such as habitat management or restocking, in areas where rabbits are native. However, the present study, conducted on enclosed wild rabbit populations, showed that spreading RHDV2 on baits during breeding periods induced infection of young rabbits, reducing mortality rates, presumably due to maternal antibody protection. This reduced the young rabbit mortality hazard by a third and more juvenile rabbits immune to RHDV2 were recruited into the adult breeding population. Young rabbits from populations in which the force of infection of RHDV2 was increased, however, exhibited considerably higher susceptibility to infection by RHDV than those from non-treated control populations. Since co-circulation of classical RHDVs was ruled out, differences in the type and degree of immunisation, the level of cross-protection and/or other unknown factors, such as the circulation of undetected non-pathogenic lagoviruses, arose as possible explanations. This meant that although the present work demonstrated the possibility of successfully modulating the impact of RHD in wild populations, the epidemiological complexity of the situation where several lagoviruses circulate requires additional research to determine final applicability of the proposed method. This article is protected by copyright. All rights reserved.

Infectivity of rabbit haemorrhagic disease virus excreted in rabbit faecal pellets

Rabbit haemorrhagic disease (RHD) is caused by a lagovirus affecting European rabbits (Oryctolagus cuniculus). Viral RNA is detected in tissues or faeces of convalescent rabbits, suggesting persistent infections; however, this RNA has not been shown to be related to infective viruses to date. In the present work, seven laboratory rabbits were challenged with the RHDV2/b virus variant. Viral RNA was individually detected by duplex qPCR in faeces collected for four weeks after infection, and the infective capacity of viral RNA excreted in the faeces of surviving rabbits was tested by challenging new rabbits with faecal inocula. As results, viral RNA was detected in faeces until the end of the assay. Viral RNA detected in the fourth week was infective only in the case of one rabbit that did not exhibit clear seroconversion, suggesting persistent infection as a result of an impaired immune response. Since the surviving rabbits were apparently healthy individuals, the importance of detecting carriers and the correct management of faeces to control RHD outbreaks in rabbitries are highlighted.

Assessment of targeted selective treatment criteria to control subclinical gastrointestinal nematode infections on sheep farms

Control of sheep gastrointestinal nematode (GIN) infections mostly relies on the use of anthelmintics. Refugia-based control strategies as targeted selective treatments (TST) can delay anthelmintic resistance development, but the optimal decision criteria for selecting individuals to be treated in subclinical infection scenarios remain unclear. The present study aimed to evaluate the suitability of body condition score (BCS) and faecal egg counts (FEC) as treatment indicators and to determine their optimized threshold values for treatment in TST by determining the relationships of BCS, FEC and anthelmintic treatment with several productive parameters in pre-mating and pre-partum periods at an individual level. Deworming in pre-mating period increased BCS gain, but its magnitude was directly associated with strongyle FEC before treatment. Deworming also increased fertility in ewes with BCS < 2.75 and the proportion of lambing ewes that got pregnant during the first ovulation cycle. Nevertheless, treatment did not yield productive benefits in ewes with higher BCS values. On the other hand, deworming in the pre-partum lowered lamb peri-partum mortality and increased lamb weight at birth and the growth of lambs during lactation, especially in lambs born from ewes with strongyle FEC > 400 epg before treatment. These results showed that FEC and especially BCS can be potential decision criteria for the implementation of TST in these types of scenarios. The TST scheme derived from the present results on the control of GIN infections should include anthelmintic treatment of ewes with BCS lower than ≈ 3 approximately five weeks before mating and lambing. In the pre-lambing period, treatment may be unnecessary if flock mean strongyle FEC is lower than ≈ 200 epg, as the proportion of ewes with individual FEC > 400 epg would be very low. The results suggest that implementation of this TST scheme would provide benefits, such as the improvement of productivity, a rational management of parasites in refugia, and preservation of future efficacy of anthelmintics, in comparison to traditional deworming schemes.

Preferences of Pet Owners in Regard to the Use of Insecticides for Flea Control

A survey conducted from 2002 to 2012 of 759 customers from 84 veterinary practices allows us to examine the habits of dog and cat owners regarding the use of insecticides for flea control. The results indicate that the percentage of animals treated during the 12 mo prior to the survey was not very high (71% in dogs and 50% in cats), considering that 100% of animals included in the study were flea-infested. Statistical analysis shows that animals older than 4 mo are treated more frequently and that dogs are more likely to be treated than cats. Among cats, those living in houses with gardens or farms are treated at a higher rate than those that live in houses without gardens or in flats. The main variable associated with the degree of satisfaction and product loyalty is the active ingredient, and the choice of a commercial product is generally associated with high-efficacy products. The mode of application of a flea treatment does not seem to have a strong influence on pet owner satisfaction or loyalty. Likewise, we do not find a clear correlation between owners' satisfaction and loyalty, so pet owners may find the results of the selected product more or less satisfactory for reasons other than simple effectiveness. Finally, because of the complexity of the life cycle of these ectoparasites, the importance of the advice of a veterinarian when planning flea control is emphasized.

Proposal for a unified classification system and nomenclature of lagoviruses

Lagoviruses belong to the Caliciviridae family. They were first recognized as highly pathogenic viruses of the European rabbit (Oryctolagus cuniculus) and European brown hare (Lepus europaeus) that emerged in the 1970-1980s, namely, rabbit haemorrhagic disease virus (RHDV) and European brown hare syndrome virus (EBHSV), according to the host species from which they had been first detected. However, the diversity of lagoviruses has recently expanded to include new related viruses with varying pathogenicity, geographic distribution and host ranges. Together with the frequent recombination observed amongst circulating viruses, there is a clear need to establish precise guidelines for classifying and naming lagovirus strains. Therefore, here we propose a new nomenclature based on phylogenetic relationships. In this new nomenclature, a single species of lagovirus would be recognized and called Lagovirus europaeus. The species would be divided into two genogroups that correspond to RHDV- and EBHSV-related viruses, respectively. Genogroups could be subdivided into genotypes, which could themselves be subdivided into phylogenetically well-supported variants. Based on available sequences, pairwise distance cutoffs have been defined, but with the accumulation of new sequences these cutoffs may need to be revised. We propose that an international working group could coordinate the nomenclature of lagoviruses and any proposals for revision.

Prevalence of Rickettsia and Bartonella species in Spanish cats and their fleas

The aim of this study was to determine the prevalence of Bartonella henselae, Rickettsia felis, and Rickettsia typhi in fleas and companion cats (serum and claws) and to assess their presence as a function of host, host habitat, and level of parasitism. Eighty-nine serum and claw samples and 90 flea pools were collected. Cat sera were assayed by IFA for Bartonella henselae and Rickettssia species IgG antibodies. Conventional PCRs were performed on DNA extracted from nails and fleas collected from cats. A large portion (55.8%) of the feline population sampled was exposed to at least one of the three tested vector-borne pathogens. Seroreactivity to B. henselae was found in 50% of the feline studied population, and to R. felis in 16.3%. R. typhi antibodies were not found in any cat. No Bartonella sp. DNA was amplified from the claws. Flea samples from 41 cats (46%) showed molecular evidence for at least one pathogen; our study demonstrated a prevalence rate of 43.3 % of Rickettsia sp and 4.4% of Bartonella sp. in the studied flea population. None of the risk factors studied (cat's features, host habitat, and level of parasitation) was associated with either the serology or the PCR results for Bartonella sp. and Rickettsia sp.. Flea-associated infectious agents are common in cats and fleas and support the recommendation that stringent flea control should be maintained on cats.

Variability of the egg hatch assay to survey benzimidazole resistance in nematodes of small ruminants under field conditions

The egg hatch assay (EHA) is one of the main in vitro methods for detection of benzimidazole resistance in nematode parasites of small ruminants. However, although the EHA has been standardised at the laboratory level, the diagnostic performance of this method has not been fully characterised for field screenings. In the present work, monthly variation of benzimidazole resistance estimated by EHA was surveyed over two years in three sheep flocks and in one goat and an additional sheep flock sharing the same pastures. Resistance was measured by calculating both the effective dose of thiabendazole (TBZ) that inhibited hatching of ≥50% of parasite eggs (ED₅₀) and the proportion (Pdd) of eggs hatching at a discriminating dose of 0.1 μg/ml TBZ. Pdd exhibited higher variability than ED₅₀, in agreement with the higher sensitivity of Pdd to changes in resistance levels. Both resistance parameters, however, were highly correlated, and their variation was similarly related to the same factors. Resistance levels differed among sheep flocks, and the resistance level of the goat flock was higher than that measured for the sheep flock sharing the same pasture. Moreover, monthly variation of resistance in goats did not mirror that recorded in sheep. Resistance levels varied seasonally, with the highest values recorded in the spring, and they were inversely related to the number of days that samples were stored under anaerobic conditions. In addition, they were directly associated with the relative abundance of Teladorsagia spp. but inversely related to the relative abundance of Haemonchus spp. After controlling for the effects of these identified factors for variation, inter-monthly sampling variation due to unknown factors was the main source of variability, accounting for more than 60-70% of variance for both resistance parameters and yielding absolute estimation errors higher than 0.06 for ED₅₀ or 0.2 for Pdd when resistance was estimated from a single sampling. Optimum sample size, estimated from variance components, suggested that at least 4-5 samplings would be needed to halve this absolute error, whereas additional samplings would slightly increase precision but at the cost of substantially increasing sampling effort. More research is needed to identify the main factors involved in this inter-sampling variation to standardise the implementation of EHA under field conditions.

Abundance modelling of invasive and indigenous Culicoides species in Spain

In this paper we present a novel methodology applied in Spain to model spatial abundance patterns of potential vectors of disease at a medium spatial resolution of 5 x 5 km using a countrywide database with abundance data for five Culicoides species, random regression Forest modelling and a spatial dataset of ground measured and remotely sensed eco-climatic and environmental predictor variables. First the probability of occurrence was computed. In a second step a direct regression between the probability of occurrence and trap abundance was established to verify the linearity of the relationship. Finally the probability of occurrence was used in combination with the set of predictor variables to model abundance. In each case the variable importance of the predictors was used to biologically interpret results and to compare both model outputs, and model performance was assessed using four different accuracy measures. Results are shown for C. imicola, C. newsteadii, C. pulicaris group, C. punctatus and C. obsoletus group. In each case the probability of occurrence is a good predictor of abundance at the used spatial resolution of 5 x 5 km. In addition, the C. imicola and C. obsoletus group are highly driven by summer rainfall. The spatial pattern is inverse between the two species, indicating that the lower and upper thresholds are different. C. pulicaris group is mainly driven by temperature. The patterns for C. newsteadii and C. punctatus are less clear. It is concluded that the proposed methodology can be used as an input to transmission-infection-recovery (TIR) models and R0 models. The methodology will become available to the general public as part of the VECMAP™ software.

Survey of flea infestation in cats in Spain

Fleas are a common cause of feline skin disorders as well as vectors of zoonotic diseases. This study evaluated the flea species infesting domestic cats in Spain and assessed factors influencing their distribution. Fleas from 217 cats from 57 localities in Spain were identified and associations between abundance, and host-dependent, host habitat and environmental factors were examined. Variations in infracommunity and component community structure were also explored. Three species were present, of which Ctenocephalides felis (Bouché) (Siphonaptera: Pulicidae) was the most abundant (98.4%), followed by Ctenocephalides canis (Curtis) (1.1%) and Pulex irritans (L.) (Siphonaptera: Pulicidae) (0.5%). Overall abundance and abundances of both C. felis and C. canis were higher on farms than in apartments, but overall flea abundance and abundances of both C. felis and C. canis were lower in rural than urban environments. Overall abundance and C. felis abundance were lower during the warmest months, and mean annual rainfall was positively correlated with overall, C. felis and C. canis abundances. No relationship between the number of species per cat and any host, habitat or physiographical variable was found. Species richness was not correlated with mean annual temperature or rainfall. Flea abundance was mainly associated with host habitat and environmental factors.

Host feeding patterns of Culicoides species (Diptera: Ceratopogonidae) within the Picos de Europa National Park in northern Spain

Blood meal identification can provide information about the natural host-feeding patterns or preferences of Culicoides species. Such information could indirectly provide data indicating which reservoirs are significant in associated vector-borne diseases. We positively identified the host species through DNA sequencing of the cytochrome b gene in 144 of the 170 (84.7%) blood meal specimens tested. In the remaining samples, identification of the blood-meal source was unsuccessful, possibly due to the post-ingestion time prior to sampling or the availability of the species-specific cytochrome b gene sequences in the database. The majority of identified blood meals were derived from mammalian blood (95.8%), and only six contained chicken blood. We identified five species as mammalian hosts for Culicoides spp.: sheep (87.7%), human (6.5%), cattle (3.7%) and Savi's Pine Vole (Micrototus savii) (2.1%). The results suggested that large mammals, specifically ruminants, were most frequently fed upon by biting midges (Culicoides spp.), but evidence of opportunistic feeding behaviour was also found. Host feeding behaviour of Culicoides species may also be influenced by the relative abundance of a particular host species in the area being studied. In this sense, Savi's Pine Vole, a wild species, was found to be a locally relevant host and a putative reservoir for viruses transmitted by species of biting midges belonging to the Culicoides genus. Finally, feeding on multiple potential host species was observed. One midge acquired blood meals from human and chicken hosts, while four other midges fed on two different sheep.

Recovery rates of bluetongue virus serotypes 1, 2, 4 and 8 Spanish strains from orally infected Culicoides imicola in South Africa

Bluetongue (BT) is an infectious disease of ruminants that has spread northwards in Europe during the last decade. The aetiological agent of the disease is an arbovirus [bluetongue virus (BTV)] that belongs to the genus Orbivirus (family Reoviridae). The virus is transmitted by certain species of biting midge within the genus Culicoides (Diptera: Ceratopogonidae). Information on the vector status of the Culicoides species in a specific area will be essential to predict the risk for BTV incursion. Field-collected Culicoides (Avaritia) imicola Kieffer from South Africa were fed on blood containing several Spanish isolates of BTV. Despite the high virus concentrations in the bloodmeal (5.1-6.4 log(10) TCID(50) /mL of blood), virus was recovered from <1% of midges assayed after incubation. Virus concentrations >2.5 log(10) TCID(50) /midge in individual infected C. imicola suggest virus replication with possible risk for transmission to susceptible vertebrate hosts in the field for at least two of the serotypes assayed (BTV-1 and BTV-2). A third serotype (BTV-4) was very close to the estimated threshold for transmission. The relatively low to near refractory status of C. imicola compared with other vector species such as Culicoides bolitinos supports previous results, indicating that Culicoides species other than C. imicola may play a more important role in the epidemiology of BTV.

Widespread exposure to Sarcoptes scabiei in wild European rabbits (Oryctolagus cuniculus) in Spain

Sarcoptic mange was recently described in the wild European rabbit (Oryctolagus cuniculus) in north-eastern Mediterranean Spain, the first such infection reported in this species anywhere in the world. This finding has created concern in conservationists and game managers given that an outbreak of mange after a translocation would have catastrophic consequences for naïve rabbit populations in other parts of Spain. A retrospective serosurvey using an 'in house' ELISA test based on the use of a recombinant antigen aimed at determining the rates of contact with Sarcoptes scabiei was carried out on sera from 966 rabbits collected between 1993 and 2010 in Spain. Antibodies were found in 13% of wild rabbits in 60% of the 53 areas surveyed, as well as in 16 of the 17 Spanish provinces and islands studied. Seropositive rabbits were found amongst the oldest samples analyzed and in all studied years. Antibodies were also detected in 36% of rabbits from the protected island of Dragonera, where rabbits have probably not been released since the 1970s. On Mallorca, where 89 rabbits were inspected for both lesions and antibodies, the prevalence of lesions (5.6%) was much lower than the seroprevalence (22.5%), indicating that rabbits often survive infection or that ELISA detects infected rabbits before they develop visible lesions. Seroprevalence was higher in areas with medium levels of rabbit abundance, no restocking and high rainfall. The results show that mange is widespread in rabbits and that the mite is not a recent introduction. Thus, sarcoptic mange could be considered as an enzootic disease in the wild rabbit and so prophylactic measures implemented during rabbit translocations are to be encouraged to avoid local outbreaks in naïve populations.

Modelling the effects of past and future climate on the risk of bluetongue emergence in Europe

Vector-borne diseases are among those most sensitive to climate because the ecology of vectors and the development rate of pathogens within them are highly dependent on environmental conditions. Bluetongue (BT), a recently emerged arboviral disease of ruminants in Europe, is often cited as an illustration of climate's impact on disease emergence, although no study has yet tested this association. Here, we develop a framework to quantitatively evaluate the effects of climate on BT's emergence in Europe by integrating high-resolution climate observations and model simulations within a mechanistic model of BT transmission risk. We demonstrate that a climate-driven model explains, in both space and time, many aspects of BT's recent emergence and spread, including the 2006 BT outbreak in northwest Europe which occurred in the year of highest projected risk since at least 1960. Furthermore, the model provides mechanistic insight into BT's emergence, suggesting that the drivers of emergence across Europe differ between the South and the North. Driven by simulated future climate from an ensemble of 11 regional climate models, the model projects increase in the future risk of BT emergence across most of Europe with uncertainty in rate but not in trend. The framework described here is adaptable and applicable to other diseases, where the link between climate and disease transmission risk can be quantified, permitting the evaluation of scale and uncertainty in climate change's impact on the future of such diseases.

Absence reduction in entomological surveillance data to improve niche-based distribution models for Culicoides imicola

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.

Protection of livestock against bluetongue virus vector Culicoides imicola using insecticide-treated netting in open areas

The protection of livestock against Culicoides species (Diptera: Ceratopogonidae) using physical barriers or chemically treated barriers is difficult owing to the small size of these biting midges and animal welfare concerns associated with the reduction of air flow. Culicoides imicola Kieffer is the main bluetongue virus vector in the Mediterranean basin, including the southern Iberian peninsula, where livestock is mainly housed in open pens or sheds which offer no physical protection against C. imicola. In this study we assessed the efficacy of surrounding yearling ewe pens with a canvas barrier or a cypermethrin-treated canvas barrier in reducing the entry of Culicoides spp. and C. imicola. Analyses were based on comparisons of Culicoides catches in traps in pens with and without barriers, and in traps located outside pens. Although there was no clear reduction in the abundance of Culicoides other than C. imicola in pens with either barrier, the C. imicola presence was markedly reduced by the insecticide-treated barrier compared with the untreated barrier; the latter did not reduce the abundance of this species in pens. Estimates of the protection conferred against C. imicola by the treated barrier differed depending on whether catch comparisons were based on outside traps or on traps located inside no-barrier pens. The results suggest that the use of insecticide-treated barriers may reduce contact between livestock and C. imicola in open areas or sheds. More research is necessary to assess the degree of protection as a function of barrier height, C. imicola abundance, and the size of the area to be protected.

Variations in the mitochondrial cytochrome c oxidase subunit I gene indicate northward expanding populations of Culicoides imicola in Spain

Culicoides imicola is the main vector for bluetongue (BT) and African horse sickness (AHS) viruses in the Mediterranean basin and in southern Europe. In this study, we analysed partial mitochondrial cytochrome c oxidase subunit I (COI) gene to characterize and confirm population expansion of Culicoides imicola across Spain. The data were analysed at two hierarchical levels to test the relationship between C. imicola haplotypes in Spain (n = 215 from 58 different locations) and worldwide (n = 277). We found nineteen different haplotypes within the Spanish population, including 11 new haplotypes. No matrilineal subdivision was found within the Spanish population, while western and eastern Mediterranean C. imicola populations were very structured. These findings were further supported by median networks and mismatch haplotype distributions. Median networks demonstrated that the haplotypes we observed in the western Mediterranean region were closely related with one another, creating a clear star-like phylogeny separated only by a single mutation from eastern haplotypes. The two, genetically distinct, sources of C. imicola in the Mediterranean basin, thus, were confirmed. This type of star-like population structure centred around the most frequent haplotype is best explained by rapid expansion. Furthermore, the proposed northern expansion was also supported by the statistically negative Tajima's D and Fu's Fs values, as well as predicted mismatch distributions of sudden and spatially expanding populations. Our results thus indicated that C. imicola population expansion was a rapid and recent phenomenon.

Entry of bluetongue vector Culicoides imicola into livestock premises in Spain

Culicoides imicola Kieffer is considered to be the main vector of bluetongue disease (BT) and African horse sickness (AHS) in the Mediterranean basin. It has been assumed that this midge species is exophilic and, consequently, that stabling of livestock should provide effective protection against these diseases. This study presents the results of sampling surveys for C. imicola carried out both inside and outside stables on three farms in mainland Spain. The number of C. imicola captured varied as a function of the populations sampled and trap location (inside vs. outside). The daily mean number captured inside during the sampling of each farm population was directly correlated with the daily mean number captured outside, but daily correlation of captures was not observed. By contrast with previous studies, the mean catch of C. imicola inside was consistently higher than that outside. No clear effect of stable characteristics on the degree of entry was detected. In addition, proportions of males and age-graded female groups varied among populations and with trap location. Proportionately more males and fewer engorged females were captured outside than inside, although the proportions varied among stables. These results contrast with those of previous studies, and with the assumed pronounced exophilic behaviour of C. imicola, and raise important questions about the vector activity of this species in the study area and its implications for the epidemiology of BT and/or AHS.

Ecological correlates of bluetongue virus in Spain: predicted spatial occurrence and its relationship with the observed abundance of the potential Culicoides spp. vector

Using data from bluetongue (BT) outbreaks caused by viral serotype 4 (BTV-4) in Spain during 2004-2005, a predictive model for BTV-4 occurrence in peninsular Spain was developed. An autologistic regression model was employed to estimate the relationships between BTV-4 presence and bioclimatic-related and host-availability-related variables. In addition, the observed abundances of the main potential Culicoides vectors during 2004-2005, namely Culicoides imicola, Culicoides obsoletus group, and species of the Culicoides pulicaris group, were compared between BTV-4 presence/absence areas predicted by the model. BTV-4 occurrence was mainly explained by bioclimatic variables, although a consideration of host-availability variables led to improved fit of the model. The area of BTV-4 presence predicted by the model largely resembled the core distribution area of C. imicola, and this species was the most abundant Culicoides spp. in predicted BTV-4 presence areas. The results suggest that the spatial expansion of BTV-4 took place only as far as those areas in which C. imicola populations efficiently transmitted the virus.

Modelling the distributions and spatial coincidence of bluetongue vectors Culicoides imicola and the Culicoides obsoletus group throughout the Iberian peninsula

Data obtained by a Spanish national surveillance programme in 2005 were used to develop climatic models for predictions of the distribution of the bluetongue virus (BTV) vectors Culicoides imicola Kieffer (Diptera: Ceratopogonidae) and the Culicoides obsoletus group Meigen throughout the Iberian peninsula. Models were generated using logistic regression to predict the probability of species occurrence at an 8-km spatial resolution. Predictor variables included the annual mean values and seasonalities of a remotely sensed normalized difference vegetation index (NDVI), a sun index, interpolated precipitation and temperature. Using an information-theoretic paradigm based on Akaike's criterion, a set of best models accounting for 95% of model selection certainty were selected and used to generate an average predictive model for each vector. The predictive performances (i.e. the discrimination capacity and calibration) of the average models were evaluated by both internal and external validation. External validation was achieved by comparing average model predictions with surveillance programme data obtained in 2004 and 2006. The discriminatory capacity of both models was found to be reasonably high. The estimated areas under the receiver operating characteristic (ROC) curve (AUC) were 0.78 and 0.70 for the C. imicola and C. obsoletus group models, respectively, in external validation, and 0.81 and 0.75, respectively, in internal validation. The predictions of both models were in close agreement with the observed distribution patterns of both vectors. Both models, however, showed a systematic bias in their predicted probability of occurrence: observed occurrence was systematically overestimated for C. imicola and underestimated for the C. obsoletus group. Average models were used to determine the areas of spatial coincidence of the two vectors. Although their spatial distributions were highly complementary, areas of spatial coincidence were identified, mainly in Portugal and in the southwest of peninsular Spain. In a hypothetical scenario in which both Culicoides members had similar vectorial capacity for a BTV strain, these areas should be considered of special epidemiological concern because any epizootic event could be intensified by consecutive vector activity developed for both species during the year; consequently, the probability of BTV spreading to remaining areas occupied by both vectors might also be higher.

Fleas parasitizing domestic dogs in Spain

In addition to their importance to veterinary clinical practice as ectoparasites, fleas of domestic dogs are of special concern because they can be vectors of disease, including zoonoses. Flea assemblages parasitizing domestic dogs usually comprise several flea species whose distribution is determined by factors acting at several scales. Knowledge of these factors will aid in assessment of the distribution patterns of flea parasitism, and is an important tool in developing control strategies and in evaluation of flea-borne disease risk in dogs and humans. In this survey we used data from 744 domestic dogs from 79 localities in Spain to explore the associations between the abundance of flea species, host-dependent factors (sex and age), and host habitat factors including abode (farm, house with garden, apartment), location (urban or rural), the presence of other pets, and dog activity (measured as the frequency with which dogs left their abode). We also considered environmental factors including the time of year and mean annual temperature and rainfall. Variations in flea community structure at infracommunity and component community levels were also explored. Four flea species were found parasitizing dogs. Ctenocephalides felis was the most abundant (88.02% of fleas identified), followed by Ctenocephalides canis (10.38%), Pulex irritans (1.47%) and Echidnophaga gallinacea (0.13%). Overall flea abundance was higher on dogs living on farms than in apartments, as was the abundance of Ct. felis, Ct. canis and P. irritans. Ct. felis was more abundant on dogs living in houses than in apartments, but the reverse was found for P. irritans. Overall flea abundance and Ct. canis abundance were highest in rural areas, whereas the presence of other pets sharing the abode was associated with higher overall flea abundance and Ct. felis abundance. Only P. irritans abundance was positively related to the activity of dogs. Ct. canis and P. irritans abundances were higher during the warm period of the year. Mean annual temperature was negatively correlated with overall, Ct. canis and P. irritans abundances, but positively related to Ct. felis abundance. Annual rainfall was negatively correlated with Ct. canis and P. irritans abundances. Variations in the number of flea species found on a dog reflected the abundance distribution patterns for each species and their associations with host habitat and environmental factors. At the component community level, flea species richness was inversely related to annual mean temperature. The structure of flea assemblages on dogs was mainly associated with host habitat and environmental variables, and not with host-dependent variables. However, a large amount of variation in flea abundance remained unexplained, suggesting the effect of other non-controlled factors.

Seroprevalence of Neospora caninum in non-carnivorous wildlife from Spain

Serum samples from 1034 non-carnivorous wildlife from Spain were tested for antibodies to Neospora caninum by competitive screening enzyme linked immunosorbent assay (ELISA) and confirmed by an indirect fluorescent antibody test (IFAT). High agreement was observed between results in both techniques (kappa value higher than 0.9). Prevalences of N. caninum antibodies positive by both techniques were 11.8% of 237 red deer (Cervus elaphus), 7.7% of 13 barbary sheep (Ammotragus lervia), 6.1% of 33 roe deer (Capreolus capreolus) and 0.3% of 298 wild boar (Sus scrofa). In one of 53 hares (Lepus granatensis), antibodies were found in the ELISA but could not be confirmed by IFAT due to lack of sample. Antibodies to N. caninum were not found in any of 251 wild rabbits (Oryctolagus cuniculus), 79 fallow deer (Dama dama), 27 mouflon (Ovis ammon), 40 chamois (Rupicapra pyrenaica) and three Spanish ibex (Capra pyrenaica). Statistically significant differences were observed between N. caninum seroprevalence in red deer and management of hunting estates (open versus fenced) with higher prevalence in fenced estates, and among sampling sites. Seroprevalence was particularly high in some areas (MO estate in South-Central Spain or some estates of Catalonia, North-East Spain), while no contact with N. caninum was observed in others. Results indicate that in certain areas of Spain, N. caninum is present in wildlife, especially in red deer. These results have important implications in both sylvatic cycles and may influence the prevalence of infection in cattle farms in those areas. To our knowledge, this is the first report of antibodies to N. caninum in wildlife from Spain and the first report of N. caninum antibodies in barbary sheep and wild boar.

Kinetics ofOestrus ovisinfection and activity of adult flies

Oestrus Ovis is a common sheep parasite in the Mediterranean region. This study was carried out in the Ebro River Valley near Zaragoza (northeast Spain) using tracer animals to describe the seasons when infestation is more likely. Based on that information and an analysis of the evolution of the parasite within the host, we suggest the most appropriate time for treatment. Adult instars appeared in May until November and there was a diapause beginning in October-November and as least until February, so it is suggested than sheep be treated with larvicide in December.

Modeling the effect of population dynamics on the impact of rabbit hemorrhagic disease

The European wild rabbit (Oryctolagus cuniculus) is a staple prey species in Mediterranean ecosystems. The arrival and subsequent spread of rabbit hemorrhagic disease throughout southwestern Europe, however has caused a decline in rabbit numbers, leading to considerable efforts to enhance wild rabbit populations, especially through habitat management. Because rabbit population dynamics depend on habitat suitability and changes in habitat structure and composition subsequent to habitat management, I evaluated the effects of population dynamics on the long-term impact of rabbit hemorrhagic disease on rabbit populations. I used an age-structured model with varying degrees of population productivity and turnover and different habitat carrying capacities, and I assumed the existence of a unique, highly pathogenic virus. My results suggest that disease impact may be highly dependent on habitat carrying capacity and rabbit population dynamics, and the model provided some insight into the current abundance of wild rabbits in different locations in southwestern Europe. The highest disease impact was estimated for populations located in habitats with low to medium carrying capacity In contrast, disease impact was lower in high-density populations in habitats with high carrying capacity, corresponding to a lower mean age of rabbit infection and a resulting lower mortality from rabbit hemorrhagic disease. The outcomes of the model suggest that management strategies to help rabbit populations recover should be based on improving habitats to their maximum carrying capacity and increasing rabbit population productivity. In contrast, the use of strategies based on temporary increases in rabbit density, including vaccination campaigns, translocations, and temporal habitat improvements at medium carrying capacities, may increase disease impact, resulting in short-term decreases in rabbit population density.

Habitat factors related to wild rabbit population trends after the initial impact of rabbit haemorrhagic disease

The European wild rabbit (Oryctolagus cuniculus) is an introduced pest species in Australia and New Zealand. Rabbits have a devastating negative impact on agricultural production and biodiversity in these countries, and Rabbit Haemorrhagic Disease (RHD) is currently included in control strategies for rabbit populations. On the other hand, the European wild rabbit is a key native prey species in the Iberian Peninsula. Since the arrival of RHD, however, rabbit populations have undergone dramatic decreases and several predator species at risk of extinction are currently dependent on the rabbit population density. Therefore, from the point of view of biodiversity conservation, evaluating habitat correlates and trends of rabbit populations after the first RHD epizootic is of great interest to improve the long-term control or promotion of wild rabbit populations. We estimated the relationship between habitat factors and long-term population trends as well as the relationships between habitat factors and rabbit abundance 2 and 14 years after the arrival of RHD in several Iberian rabbit populations. We observed that only 26% of surveyed populations seemed to experience an increase in rabbit abundance over the last 12 years and that this increase was higher in the low-rabbit-abundance areas of l992, leading to high rabbit abundance in 2004. Our results suggested that short- and long-term impacts of RHD were related to habitat quality. The initial impact of RHD was higher in more suitable habitats, but increasing long-term population trends were positively related to good habitat quality.

Effects of vaccination against viral haemorrhagic disease and myxomatosis on long-term mortality rates of European wild rabbits

The effects of vaccination against myxomatosis and viral haemorrhagic disease (VHD) on long-term mortality rates in European rabbits (Oryctolagus cuniculus) were studied from 1993 to 1996 by radiotracking a free-living population of wild rabbits. During the three months after immunisation, unvaccinated young rabbits weighing between 180 and 600 g were 13.6 times more likely to die than vaccinated young rabbits. In adult rabbits, vaccination did not significantly decrease mortality, mainly owing to the high proportion of rabbits which had previously been exposed to the antigens of both diseases. Compared with adult rabbits with natural antibodies to VHD, rabbits without these antibodies were 5.2 times more likely to die of VHD during annual outbreaks.

Factors affecting the seroprevalence of Toxoplasma gondii infection in wild rabbits (Oryctolagus cuniculus) from Spain

Sera from 456 wild rabbits (Oryctolagus cuniculus) collected between 1992 and 2003 from five geographical regions of Spain were examined for antibodies to Toxoplasma gondii by the modified agglutination test. Antibodies to T. gondii were found in 65 (14.2%) wild rabbits. Prevalence of infection was significantly higher in samples collected from wild rabbits from Catalonia, northeast Spain (53.8%), where rabbits lived in forest, compared to other areas (Huelva and Cádiz, Andalucía, south Spain; Toledo, Castilla-La Mancha, central Spain; and Zaragoza, Aragón, northeast Spain) with more dry conditions, where prevalence ranged from 6.1 to 14.6%. No differences were observed on prevalence and age (young animals <7 months of age compared to older animals), sex, date of samples collection or season of samples collection. The results indicate that prevalence of T. gondii in some areas of Spain is high, and this finding could have environmental and/or public health implications if wild rabbits are to be used as a source of food.

Spatial variation in helminth community structure in the red-legged partridge (Alectoris rufaL.): effects of definitive host density

Parasite community ecology has recently focused on understanding the forces structuring these communities. There are few surveys, however, designed to study the spatial repeatability and predictability of parasite communities at the local scale in one host. The purpose of our study was to address the relationship between infracommunity and component community richness, and to describe spatial variations on the local scale, of helminth parasite communities in an avian host, the red-legged partridge (Alectoris rufa). We sampled 235 wild partridges from 8 separate localities, with different partridge population densities, in the Ciudad Real and Toledo provinces of central Spain, and we determined their overall and intestinal helminth species. We found that habitat variables (mean temperature and land use) were not significantly associated with any component community. The partridge population abundance index was directly correlated with the prevalence and mean intensity of infection but not with component community species richness. There was a curvilinear relationship between infracommunity and component community species richness, as well as negative interspecific associations, for the helminth species assemblage parasitizing the intestine. A nestedness/anti-nestedness pattern, considered as part of a continuum, was associated with prevalence, mean intensity and partridge population abundance index, but not with component community richness. Increases in the partridge population abundance index and the prevalence and mean intensity of infection were associated with increases in helminth community nestedness. Although negative interactions between helminth species could not be ruled out as forces structuring helminth communities, our results suggest that parasite community structure in the red-legged partridge was primarily determined by the extrinsic influence of parasite habitat heterogeneity and its amplification of the differing probabilities of colonization of parasite species.

Correlates of helminth community in the red-legged partridge (Alectoris rufa L.) in Spain

Between 1992 and 1996, 587 wild red-legged partridges (Alectoris rufa) from 16 Spanish provinces were examined to study the variations of helminth communities in this game species across a broad geographical area. The survey revealed 13 species of helminth parasites. Dicrocoelium sp.. Rhabdometra nigropunctata, and Cheilospirura gruweli were the most common species, whereas Raillietina bolivari, Choanotaenia infundibulum, Tetrameres sp., and Capillaria anatis were the most rare. Subulura suctoria, Heterakis gallinarum, Heterakis tenuicaudata, Capillaria contorta, Trichostrongylus tenuis, and Raillietina tetragona occurred with intermediate frequencies. The abundance of C. gruweli, S. suctoria, H. tenuicaudata, T. tenuis, and R. tetragona was inversely correlated to latitude and directly correlated to yearly mean temperature, whereas the abundance of Dicrocoelium sp. was directly correlated to latitude and inversely correlated to yearly mean temperature. The abundance of R. tetragona was inversely correlated to latitude and yearly mean humidity. The number of helminths per partridge and the number of helminth species per partridge were lower in young birds than in adults. Partridge body condition was inversely correlated to abundance of C. contorta. Richer infracommunities were linked to richer component communities. At the infracommunity level, total number of helminths per partridge and number of helminth species per partridge were inversely correlated to latitude and directly correlated to yearly mean temperature. At the component community level, both species richness and diversity (Simpson's index) were inversely correlated to latitude and directly correlated to mean temperature. Across the broad geographical range of the study area, the helminth parasite communities of red-legged partridges had marked geographical variation in their structure. Our results suggest that this variation is determined by the distribution of both intermediate and definitive hosts. We discuss the implications of this variation for the hypothesis that supplementary releases of captive-bred partridges for sport hunting can affect the helminth fauna of wild red-legged partridges.

Ectoparasite ticks and chewing lice of red-legged partridge, Alectoris rufa, in Spain

During the 1992-1993 and 1993-1994 shooting seasons, 212 wild red-legged partridge, Alectoris rufa (Galliformes: Phaisanide) were captured in 18 Spanish provinces and examined for chewing lice and ticks. Three tick species and six species of chewing lice were found. Ticks (Acari: Ixodidae) Haemaphysalis punctata Canestrini & Fanzago, Hyalomma lusitanicum Koch and Ixodes frontalis Panzer were found at the lowest prevalence (1.4% overall tick prevalence). The louse (Mallophaga) species, Goniodes dispar Burmeister (Goniodidae) (52.8%) and Cuclotogaster obscurior Hopkins (Philopteridae) (28.8%) were the most prevalent, while Goniocotes obscurus Giebel (Philopteridae) (10.8%), Menopon pallens Clay (Menoponidae) (7.5%) and Menacanthus lyali Rodriguez et al. (Menoponidae) (3.3%) were found at medium to low prevalence. Columbicola columbae columbae Linnaeus (Philopteridae) was found at the lowest prevalence (0.5%). The intensity of C. obscurior and overall intensity of all lice species were directly related to the environmental mean temperature and the Normalized Difference Vegetation Index (NDVI), whereas intensity of G. dispar was directly related to NDVI only. The intensity of G. dispar, C. obscurior, all louse intensity, and louse species richness were higher in male than female birds. Intensity of each louse species, all louse intensity and louse species richness were inversely associated with the nutritional index. No relationship was observed between bird age and louse intensity or species richness.

Epidemiology of viral haemorrhagic disease and myxomatosis in a free-living population of wild rabbits

From January 1993 to June 1996, the epidemiology of myxomatosis and viral haemorrhagic disease (VHD) was studied in a free-living population of wild rabbits (Oryctolagus cuniculus) in Spain by means of serological surveys and radiotracking. Myxomatosis was endemic and associated with the breeding period. Its serological pattern was characterised by a 100 per cent prevalence of antibodies in adult rabbits and a rapid increase in antibodies in young rabbits in their first year. No mortality from myxomatosis was detected in adults, and mortality in young rabbits could not be estimated because of interference by predators and scavengers and the deaths of many radiotagged rabbits inside their burrows. VHD was also an endemic disease associated with the breeding period. Adults had a higher prevalence of antibodies against VHD than young rabbits, reaching values of 80 to 90 per cent. During the study, there was an increase in rabbit numbers as a result of a decrease in mortality from predation which was associated with an increase in mortality due to VHD and in the prevalence of antibodies to VHD. Mortality from VHD was lower in rabbits with VHD antibodies than in seronegative rabbits, but some mortality from the disease was also detected in seropositive rabbits. The annual mean mortality rate due to VHD in adult rabbits was estimated to be 21.8 per cent.

Seasonal abundance of fleas (Siphonaptera: Pulicidae, Ceratophyllidae) on wild rabbits in a semiarid area of northeastern Spain

This paper reports the annual dynamics of wild rabbit fleas in a study site located in the Middle Ebro Valley, northeastern Spain. Fleas collected directly from wild rabbits included the species Spilopsyllus cuniculi (Dale), Xenopsylla cunicularis (Smit), Echidnophaga iberica (Ribeiro, Lucientes, Osácar, and Calvete), Caenopsylla laptevi (Beaucournu, Gil-Collado and Gilot), and Pulex irritans (L.). Monthly collections of adult and larval fleas made from within the first meter of selected burrow entrances also yielded fleas belonging to the same five species. Larval specimens of X. cunicularis, E. iberica, and C. laptevi were also found. Spilopsyllus cuniculi, a winter species that can only breed during the rabbit breeding season, was common on hosts from November to April. Xenopsylla cunicularis and E. iberica were summer species, whereas C. laptevi was abundant during the autumn and winter. Xenopsylla cunicularis and E. iberica larvae were found in burrows only during April and May, whereas those of C. laptevi were collected from October to January. The data suggested that X. cunicularis and E. iberica might diapause during the egg stage whereas C. laptevi diapauses during the pupal stage.

Gastrointestinal helminth parasites in stray cats from the mid-Ebro Valley, Spain

Gastrointestinal helminths were collected from 58 necropsied stray cats (Felis catus) in the mid-Ebro Valley, North-East Spain, from December 1989 to March 1992. The prevalence was 89.7%, with those of individual parasites being Toxocara cati 55.2%C, Ancylostoma tubaeforme 29.3% Joyeuxiella pasqualei 55.2%, Diplopylidium acanthotetra 20.7%, Dipylidium caninum 20.7%, Mesocestoides spp. 13.8%, Taenia taeniformis 8.6% and Diplopylidium nölleri 8.6%. In relation to sex, the differences were not significant. However, the season of the year significantly affected the prevalence of A. tubaeforme and D. acanthotetra.

New species of flea (Siphonaptera: Pulicidae) from Spain

The male holotype and female allotype of Echidnophaga iberica Ribeiro, Lucientes, Osacar & Calvete, a new species of rabbit flea from the Zaragoza area, northeastern Spain, is described on the basis of examination of a type series of six males and 13 females. Similarities of the new species with other species of the genus Echidnophaga are discussed and a key to identification of the four known Mediterranean species of the genus is provided.

Factors affecting Dirofilaria immitis prevalence in red foxes in northeastern Spain

We determined the prevalence of Dirofilaria immitis (Nematoda, Filariidae) among 433 red foxes (Vulpes vulpes) in northeastern Spain, between 1990 and 1992. Forty-six (11%) of 433 foxes were infected; the intensity ranged from 1 to 36 (mean +/- SE; 4.39 +/- 0.92) nematodes per host. The prevalence of D. immitis was higher in foxes inhabiting riparian zones of the study area. This population has a very high juvenile/adult ratio. Heartworm prevalences did not differ among host sex, weight, or fat condition categories.

First epizootic of rabbit hemorrhagic disease in free living populations of Oryctolagus cuniculus at Doñana National Park, Spain

The first known epizootic of rabbit hemorrhagic disease (RHD) occurred in two free-living wild rabbit (Oryctolagus cuniculus) populations at Doñana National Park, Spain. Rabbit population density was not correlated to RHD mortality. Only adult animals were affected; males and females had similar mortality rates.

An account of the ticks of the northeastern of Spain (Acarina: Ixodidae)

The tick species commonly collected at the Northeast of Spain are reported in this paper. Data on hosts, temperature and humidity requirements, vegetation relationships, altitudinal distribution, and seasonal activity are included. R. sanguineus is commonly collected in areas with Mediterranean vegetation, esteppe, and semi-desertic esteppe, ranging from 190 to 1,000 meters above the sea level. R. sanguineus is related with sparse vegetal areas, and it is absent from areas with dense shrub or forests of every kind; sometimes, small populations may be collected in ecotones between Pinus spp. and esteppe formations. R. pusillus is closely related to areas of Mesomediterranean vegetation, sometimes subordinate to Pinus spp. and Quercus spp. The climate to which the species ally is always of continental type, with a hot and dry summer, and cold winter; although the species is commonly restricted to its main host, Oryctolagus cuniculus, several specimens have been collected from V. vulpes. Our data display the clear affinity of I. ricinus to the Supramediterranean vegetation (Aceri-Quercion faginae), places of Quercetum-Buxetum, as well as the Iberian Oromediterranean vegetation (Pinus sylvestris-Buxus sempervirens). Captures are scarce in forest of Fagus sylvatica, but data suggest that the species may be locally common on such places. Climate for the zones of collection of I. ricinus is Atlantic attenuated, with mild summers and humid winters. D. marginatus is strongly related to the xerophilic vegetation, widely spread through the Mediterranean, Supramediterranean, and hill levels, but does not colonize the true Oromediterranean vegetation. In our captures, the species is commonly collected in pubescent oak formations, but it does not penetrate in true forest associations.(ABSTRACT TRUNCATED AT 250 WORDS)