Hedgerows interact with forests to shape the abundance of mesopredators and their predation rate on eggs in farmland landscapes

Nest predation is the main cause of reproductive failure, particularly in ground-nesting birds on farmlands. Understanding the links between nest predation and habitat change can help design effective management schemes to constrain the negative impact of predation pressure on birds. However, the mechanisms underlying the relationships between landscape attributes, predator distribution, and nest predation are still unclear. Here, we use an experimental approach to examine the effects of distance to the hedgerow as well as hedgerow and forest densities on the abundance of major mesopredators of ground nests of our study area (i.e., corvids) and on the predation rate of artificial ground nests (n = 2576). We found evidence that landscape configuration influenced predation patterns differently depending on the predator species. Nest predation by corvids was more likely in homogeneous and open agricultural landscapes with a low density of forest and hedgerows, whereas predation by other predators was more likely close to hedgerows. Nest predation by corvids and the abundance of corvids also tended to be lower in landscapes dominated by grasslands. Other variables such as road density and distance to human settlements had contrasted effects on the likelihood of a nest being depredated by corvids, i.e., no effect with proximity to human settlements and decreasing trend with road density. Altogether, our results suggest that landscape features interact with mesopredator distribution and their predation rates of ground nests. Therefore, from a conservation and management perspective, a heterogeneous agricultural landscape that includes a mixture of crops associated with patches of forests, hedgerows, and grasslands offering alternative food to generalist predators should contribute to reducing ground-nesting bird predation.

Common names of the Asiatic ibex superspecies at a turning point in its taxonomy and management

Common names of species matter in species management. However, taxonomic inertia and a blurred perception of a species can hinder the updating of framework documents and conservation schemes. Ibexes from Asia are a notable case of a polytypic species with numerous common names. This review examines data on the common names and taxonomy used for this superspecies. Some taxonomic units and common names are more consistent with recent genetic data than others and highlight management and/or conservation issues. The standardized use of this information in management schemes for the Capra sibirica complex will help lessen the risk of the extinction of distinguishable ibex conservation units from Asia, and, indirectly, of other species that share their geographical ranges.

Detectability and predator strategy affect egg depredation rates: Implications for mitigating nest depredation in farmlands

Predation is a major evolutionary force in animal ecology. Mechanisms by which prey coloration provides camouflage has been widely studied. However, predator response to prey camouflage and concealment has received less attention. Understanding vegetation structure effect on depredation success could help managers design strategies to mitigate the depredation of managed species (e.g., threatened or hunted). We aimed to investigate the relationship between depredation rate, nest camouflage and concealment in ground-nesting birds of farmlands, and their predators. We set up an experiment of 2576 artificial ground nests to assess the role of egg coloration (white, light green, and dark green), egg size (small, medium, and large), and vegetation structure (vegetation height and land use) in nest survival rates. We also explored the role of predator searching strategies by analysing clumped depredation and multiple depredation events. Of the nests, 34.0% were depredated, with corvids as the predators 78.5% of the time. Corvid depredation decreased by 40-60% in grasslands and spring crops above a vegetation height of 30 cm. In contrast, vegetation height and land use may be of far less importance in avoiding depredation by other predators. The probability of depredation was spatially clumped, suggesting that predators increase search effort in areas where a nest was previously encountered. Neighboring depredation and depredation repetition were more frequent in corvids than in other predators. Our study indicates that nests in vegetation higher than 30 cm had a drastic reduction in depredation rates by corvids. Management of vegetation structure is a key tool to mitigate depredation risk, and improving the availability of alternative food resources may be a complementary tool.

Diel cycle in a farmland bird is shaped by contrasting predation and human pressures

In human-dominated landscapes, human disturbances may contrast (spatially and/or temporally) with risk imposed by non-human predators. However, how prey adjust behaviour to minimize risk from multiple threats remains unclear. In Central-Western France, we investigated patterns of activity, space and habitat use, and causes of variations during the diel cycle of the grey partridge (captive-reared, released), a farmland bird facing multiple risks (nocturnal predation, diurnal hunting pressure). We also investigated influence of individual space use, relative to risk-related features on the fate of birds. Birds adjusted their behaviours in ways consistent with the reduction of risk from nocturnal carnivores at night and hunters during daytime. We recorded bimodal crepuscular activity, likely explained by commuting movements between spatially-separated diurnal and nocturnal sites composed of different habitats: selection of open terrains and avoidance of predator reservoirs at night vs. use of high-vegetation cover during daytime. We observed space use differences between surviving, hunted and predated birds. Predation and hunting activities act as contrasting pressures, selecting birds based on their spatial behaviour, which has likely shaped diel adjustments at the population level. An improved consideration of temporal variation in environmental pressures would help to reliably address factors constraining populations, so increasing wildlife management efficiency.

Revisiting an old question: Which predators eat eggs of ground-nesting birds in farmland landscapes?

Nest predation is a major cause of reproductive failure in birds, but predator identity often remains unknown. Additionally, although corvids are considered major nest predators in farmland landscapes, whether breeders or floaters are involved remains contentious. In this study, we aimed to identify nest predators using artificial nests, and test whether territorial or non-breeders carrion crow (Corvus corone) and Eurasian magpie (Pica pica) were most likely involved. We set up an experiment with artificial ground nests (n = 1429) in farmland landscapes of western France, and assessed how different combinations of egg size and egg material (small plasticine egg, large plasticine egg, quail and natural hen eggs) might influence predation rates and predator species involved. Nest predators were identified using remotely triggered cameras and marks left in plasticine eggs. Corvids were by far the predators most involved (almost 80% of all predation events), independent of egg type. Carrion crows alone were involved in 60% of cases. Probability of predation increased with egg size, and predation rate was higher for natural than for artificial eggs, suggesting that, in addition to egg size, predators might perceive plasticine and natural eggs differently. Predation rates of artificial nests by corvids were related significantly to corvid abundance, and far more to breeder than floater abundances, for both carrion crows and magpies. This study emphasizes the importance of identifying predators at species level, and considering their social status when assessing corvid abundance impact on prey population dynamics. Combining camera traps and plasticine eggs can achieve this objective. Given the high predation rate by carrion crows, a better understanding of landscape-mediated changes in predator diet seems mandatory to design mitigation schemes able to confront ecological challenges raised by generalist predators.

Plasma Aβ42/40 Ratio Detects Early Stages of Alzheimer's Disease and Correlates with CSF and Neuroimaging Biomarkers in the AB255 Study

BACKGROUND

Easily accessible biomarkers are needed for the early identification of individuals at risk of developing Alzheimer's disease (AD) in large population screening strategies.

OBJECTIVES

This study evaluated the potential of plasma β-amyloid (Aβ) biomarkers in identifying early stages of AD and predicting cognitive decline over the following two years.

DESIGN

Total plasma Aβ42/40 ratio (TP42/40) was determined in 83 cognitively normal individuals (CN) and 145 subjects with amnestic mild cognitive impairment (a-MCI) stratified by an FDG-PET AD-risk pattern.

RESULTS

Significant lower TP42/40 ratio was found in a-MCI patients compared to CN. Moreover, a-MCIs with a high-risk FDG-PET pattern for AD showed even lower plasma ratio levels. Low TP42/40 at baseline increased the risk of progression to dementia by 70%. Furthermore, TP42/40 was inversely associated with neocortical amyloid deposition (measured with PiB-PET) and was concordant with the AD biomarker profile in cerebrospinal fluid (CSF).

CONCLUSIONS

TP42/40 demonstrated value in the identification of individuals suffering a-MCI, in the prediction of progression to dementia, and in the detection of underlying AD pathology revealed by FDG-PET, Amyloid-PET and CSF biomarkers, being, thus, consistently associated with all the well-established indicators of AD.

Exposure of Wild Ungulates to the Usutu and Tick-Borne Encephalitis Viruses in France in 2009-2014: Evidence of Undetected Flavivirus Circulation a Decade Ago

Abstract: Flaviviruses have become increasingly important pathogens in Europe over the past few decades. A better understanding of the spatiotemporal distribution of flaviviruses in France is needed to better define risk areas and to gain knowledge of the dynamics of virus transmission cycles. Serum samples from 1014 wild boar and 758 roe deer from 16 departments (administrative units) in France collected from 2009 to 2014 were screened for flavivirus antibodies using a competitive ELISA (cELISA) technique. Serum samples found to be positive or doubtful by cELISA were then tested for antibodies directed against West Nile virus (WNV), Usutu virus (USUV), Bagaza virus (BAGV), and tick-borne encephalitis/Louping ill viruses (TBEV/LIV) by microsphere immunoassays (except BAGV) and micro-neutralization tests. USUV antibodies were detected only in southeastern and southwestern areas. TBEV/LIV antibodies were detected in serum samples from eastern, southwestern and northern departments. The results indicate continuous circulation of USUV in southern France from 2009 to 2014, which was unnoticed by the French monitoring system for bird mortality. The findings also confirm wider distribution of TBEV in the eastern part of the country than of human clinical cases. However, further studies are needed to determine the tick-borne flavivirus responsible for the seroconversion in southwestern and northern France.

Influence of flavivirus co-circulation in serological diagnostics and surveillance: A model of study using West Nile, Usutu and Bagaza viruses

This study aims at assessing the serological cross-reactions existing between three mosquito-borne flaviviruses with avian reservoirs co-circulating in Europe: West Nile (WNV), Usutu (USUV) and Bagaza (BAGV). The study is useful for a better interpretation of serological results in diagnostics and surveillance. Serum samples obtained from a natural host, the red-legged partridge (Alectoris rufa), experimentally infected with WNV, USUV or BAGV were analysed using two commercially available WNV competition ELISAs suitable for serological surveillance, and by the confirmatory virus neutralization test (VNT). The ELISAs examined showed different levels of specificity for WNV, as judged by cross-reaction observed with the other flaviviruses. By VNT, virus-specific antibodies were confirmed in 80%, 50% or 0% of sera from WNV-, BAGV-, or USUV-inoculated birds, respectively. The results indicate how the co-circulation of cross-reacting flaviviruses may affect the outcomes of WNV serological surveillance when applying currently available serological tools. On the one hand, the choice of the ELISA test for antibody screening should consider the differences found in specificity, since one test is more specific for WNV while the other one is more suitable for detection of a broader range of flavivirus antibodies. On the other hand, besides corroborating that cross-neutralization occurs between flaviviruses from different serocomplexes (WNV/USUV and BAGV), this study points out that cross-neutralization between WNV and USUV is not symmetric, and reveals the difficulty to identify USUV infections serologically. This finding indicates that actual USUV infections might be underestimated in the current diagnostic schemes.

Monitoring black grouse Tetrao tetrix in Isère, northern French Alps: cofactors, population trends and potential biases

Wildlife management benefits from studies that verify or improve the reliability of monitoring protocols. In this study in Isère, France, we tested for potential links between the abundance of black grouse (Tetrao tetrix) in lek–count surveys and cofactors (procedural, geographical and meteorological cofactors) between 1989 and 2016. We also examined the effect of omitting or considering the important cofactors on the long–term population trend that can be inferred from lek–count data. Model selections for data at hand highlighted that the abundance of black grouse was mainly linked to procedural cofactors, such as the number of observers, the time of first observation of a displaying male, the day, and the year of the count. Some additional factors relating to the surface of the census sector, temperature, northing, altitude and wind conditions also appeared depending on the spatial or temporal scale of the analysis. The inclusion of the important cofactors in models modulated the estimates of population trends. The results of the larger dataset highlighted a mean increase of +17 % (+5.3 %; +29 %) of the abundance of black grouse from 1997 to 2001, and a mean increase in population of +47 % (+16 %; +87 %) throughout the study period (1989–2016). We discuss the hypothesis of plausible links between this past increase in the number of black grouse and the ecological impact of the winter storm ‘Vivian’. Findings from our study and the ecological phenomena that were concomitant with the observed population trend provide opportunities to strengthen the monitoring and management of black grouse in the Alps.

Changes in habitat selection patterns of the gray partridge Perdix perdix in relation to agricultural landscape dynamics over the past two decades

Changes in agricultural practices have reshaped agricultural landscapes and triggered a drastic decline in spatial and temporal heterogeneity leading to changes in habitat quality and food resources for birds. However, the precise relationships between landscape changes, spatial and temporal heterogeneity, and habitat preferences in response to those changes remain poorly known.We investigated patterns of habitat selection and causes for changes over the years 1997-2017 for the gray partridge Perdix perdix, an iconic farmland species which has experienced a severe decline since the 1950s. Using a long-term (1997-2017) dataset collected over 435 km2, we modeled relationships between annual land-cover maps and partridge sightings over 17 5-year moving windows, assessing the effects of landscape metrics, the strength of the relationships, and the dynamics of habitat suitability.We detected a shift in gray partridge habitat preferences over time, toward more risky habitats. Avoidance of predator reservoirs (woodlands and buildings) has weakened, and selection of human infrastructure, such as roads and tracks, has increased. Since 1997, the mean size of suitable patches has also decreased by about 26%.We have interpreted these changes in habitat selection as being the result of decreasing habitat quality and the increasing prevalence of captive-reared birds, currently released in their thousands in the study site. Synthesis and applications. The gray partridge has not adjusted well to changes in farming practices, and the low, still decreasing, population density suggests that it is not sustainable, despite local initiatives and the investment in captive-bird releases. We emphasize that efforts must be redirected toward habitat improvement to restore the density of refuge cover, insects, and seeds in the landscape, hunting management to ensure self-sustainable populations and massive releases of high-quality birds. Only integrated local management, involving hunters, farmers, gamekeepers, and scientists can ensure the recovery of this species.

Complete mitochondrial genome of the Western Capercaillie Tetrao urogallus (Phasianidae, Tetraoninae)

The Western Capercaillie (Tetrao urogallus) is a galliform bird of boreal climax forests from Scandinavia to eastern Siberia, with a fragmented population in southwestern Europe. We extracted the DNA of T. urogallus aquitanicus and obtained the complete mitochondrial genome (mitogenome) sequence by combining Illumina and Sanger sequencing sequence data. The mitochondrial genome of T. urogallus is 16,683 bp long and is very similar to that of Lyrurus tetrix (16,677 bp). The T. urogallus mitogenome contains the normal 13 protein-coding genes (PCGs), 22 transfer RNAs, 2 ribosomal RNAs, and the control region. The number, order, and orientation of the mitochondrial genes are the same as in L. tetrix and in other species of the same and other bird families. The three domains of the control region contained conserved sequences (ETAS; CSBs), boxes (F, E, D, C, B, BS box), the putative origin of replication of the H-strand (OH) and bidirectional promoters of translation (LSP/HSP).

Correlations between plasma and PET beta-amyloid levels in individuals with subjective cognitive decline: the Fundació ACE Healthy Brain Initiative (FACEHBI)

BACKGROUND

Peripheral biomarkers that identify individuals at risk of developing Alzheimer's disease (AD) or predicting high amyloid beta (Aβ) brain burden would be highly valuable. To facilitate clinical trials of disease-modifying therapies, plasma concentrations of Aβ species are good candidates for peripheral AD biomarkers, but studies to date have generated conflicting results.

METHODS

The Fundació ACE Healthy Brain Initiative (FACEHBI) study uses a convenience sample of 200 individuals diagnosed with subjective cognitive decline (SCD) at the Fundació ACE (Barcelona, Spain) who underwent amyloid florbetaben(18F) (FBB) positron emission tomography (PET) brain imaging. Baseline plasma samples from FACEHBI subjects (aged 65.9 ± 7.2 years) were analyzed using the ABtest (Araclon Biotech). This test directly determines the free plasma (FP) and total plasma (TP) levels of Aβ40 and Aβ42 peptides. The association between Aβ40 and Aβ42 plasma levels and FBB-PET global standardized uptake value ratio (SUVR) was determined using correlations and linear regression-based methods. The effect of the APOE genotype on plasma Aβ levels and FBB-PET was also assessed. Finally, various models including different combinations of demographics, genetics, and Aβ plasma levels were constructed using logistic regression and area under the receiver operating characteristic curve (AUROC) analyses to evaluate their ability for discriminating which subjects presented brain amyloidosis.

RESULTS

FBB-PET global SUVR correlated weakly but significantly with Aβ42/40 plasma ratios. For TP42/40, this observation persisted after controlling for age and APOE ε4 allele carrier status (R2 = 0.193, p = 1.01E-09). The ROC curve demonstrated that plasma Aβ measurements are not superior to APOE and age in combination in predicting brain amyloidosis. It is noteworthy that using a simple preselection tool (the TP42/40 ratio with an empirical cut-off value of 0.08) optimizes the sensitivity and reduces the number of individuals subjected to Aβ FBB-PET scanners to 52.8%. No significant dependency was observed between APOE genotype and plasma Aβ measurements (p value for interaction = 0.105).

CONCLUSION

Brain and plasma Aβ levels are partially correlated in individuals diagnosed with SCD. Aβ plasma measurements, particularly the TP42/40 ratio, could generate a new recruitment strategy independent of the APOE genotype that would improve identification of SCD subjects with brain amyloidosis and reduce the rate of screening failures in preclinical AD studies. Independent replication of these findings is warranted.

FACEHBI: A Prospective Study of Risk Factors, Biomarkers and Cognition in a Cohort of Individuals with Subjective Cognitive Decline. Study Rationale and Research Protocols

BACKGROUND

Long-term longitudinal studies with multimodal biomarkers are needed to delve into the knowledge of preclinical AD. Subjective cognitive decline has been proposed as a risk factor for the development of cognitive impairment. Thus, including individuals with SCD in observational studies may be a cost-effective strategy to increase the prevalence of preclinical AD in the sample.

OBJECTIVES

To describe the rationale, research protocols and baseline characteristics of participants in the Fundació ACE Healthy Brain Initiative (FACEHBI).

DESIGN

FACEHBI is a clinical trial (EudraCT: 2014-000798-38) embedded within a long-term observational study of individuals with SCD.

SETTING

Participants have been recruited at the memory clinic of Fundació ACE (Barcelona) from two different sources: patients referred by a general practitioner and individuals from an Open House Initiative.

PARTICIPANTS

200 individuals diagnosed with SCD with a strictly normal performance in a comprehensive neuropsychological battery.

MEASUREMENTS

Individuals will undergo an extensive neuropsychological protocol, risk factor assessment and a set of multimodal biomarkers including florbetaben PET, structural and functional MRI, diffusion tensor imaging, determination of amyloid species in plasma and neurophthalmologic assessment with optical coherence tomography.

RESULTS

Two hundred individuals have been recruited in 15 months. Mean age was 65.9 years; mean MMSE was 29.2 with a mean of 14.8 years of education.

CONCLUSIONS

FACEHBI is a long-term study of cognition, biomarkers and lifestyle that has been designed upon an innovative symptom-based approach using SCD as target population. It will shed light on the pathophysiology of preclinical AD and the role of SCD as a risk marker for the development of cognitive impairment.

HPLC-QTOF method for quantifying 11-ketoetiocholanolone, a cortisol metabolite, in ruminants' feces: Optimization and validation

Studies of animal ecology can benefit from a quantified understanding of eco-physiological processes and, in particular, of the physiological responses in free-ranging animals to potential stressors. The determination of fecal cortisol metabolites as a noninvasive method for monitoring stress has proved to be a powerful tool. High-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) has emerged as the most accurate method for avoiding problems related to the nonspecificity of immunoassays. In this study, we optimize and validate a reliable method using HPLC-MS/MS for quantifying 11-ketoetiocholanolone (11-k), a representative fecal cortisol metabolite in ruminants. An appropriate extraction and purification procedure was developed taking into account the complex nature of feces. The final extract obtained was then analyzed with HPLC-MS/MS using a quadrupole-time-of-fly (QTOF) tandem mass spectrometer with an electrospray ionization interface operating in positive mode, which allowed an unequivocal determination of the metabolite due to its accurate mass capabilities. After rigorous optimization of both sample extraction and the HPLC-QTOF parameters, making use of feces from free-ranging Iberian ibex, ideal conditions were established. Matrix-matched standards were used to calibrate the method. The limit of detection and quantification was 13- and 40- ng/g, respectively. The validation of the method was performed with recoveries in the range of 85-110%, a figure much higher than the 60% obtained with the previous extraction methods used in our laboratory, and with relative standard deviations (RSDs) no higher than 15% for the complete analytical procedure, including extraction and analysis. The time required for the fecal 11-k analysis was greatly reduced in comparison with the previous work carried out in our laboratory. This is the first time that QTOF mass detection coupled with HPLC has been validated for 11-k quantification in feces from free-ranging ruminants such as Iberian ibex. Given the high selectivity and sensitivity attained, our method could become a useful tool for noninvasive stress quantification in ruminants.

Experimental infection of grey partridges with Bagaza virus: pathogenicity evaluation and potential role as a competent host

Bagaza virus (BAGV; synonymous to Israel turkey meningoencephalomyelitis virus, ITV) is a relevant arthropod-borne epornitic flavivirus. In its first emergence in Europe (southern Spain, 2010) BAGV caused an outbreak, severely affecting red-legged partridges and common pheasants. The effects (pathogenicity, role as reservoir host) of BAGV in other European phasianids are unknown. To fill this gap, grey partridges were experimentally infected with BAGV. The clinical course of the disease was severe, with neurological signs, significant weight loss and 40% mortality. Low viral loads in the blood and the absence of contact transmission suggest a limited—if any—role on BAGV transmission for this European phasianid.

Does wintering north or south of the Sahara correlate with timing and breeding performance in black-tailed godwits?

Migrating long distances requires time and energy, and may interact with an individual's performance during breeding. These seasonal interactions in migratory animals are best described in populations with disjunct nonbreeding distributions. The black‐tailed godwit (Limosa limosa limosa), which breeds in agricultural grasslands in Western Europe, has such a disjunct nonbreeding distribution: The majority spend the nonbreeding season in West Africa, while a growing number winters north of the Sahara on the Iberian Peninsula. To test whether crossing the Sahara has an effect on breeding season phenology and reproductive parameters, we examined differences in the timing of arrival, breeding habitat quality, lay date, egg volume, and daily nest survival among godwits (154 females and 157 males), individually marked in a breeding area in the Netherlands for which wintering destination was known on the basis of resightings. We also examined whether individual repeatability in arrival date differed between birds wintering north or south of the Sahara. Contrary to expectation, godwits wintering south of the Sahara arrived two days earlier and initiated their clutch six days earlier than godwits wintering north of the Sahara. Arrival date was equally repeatable for both groups, and egg volume larger in birds wintering north of the Sahara. Despite these differences, we found no association between wintering location and the quality of breeding habitat or nest survival. This suggests that the crossing of an important ecological barrier and doubling of the migration distance, twice a year, do not have clear negative reproductive consequences for some long‐distance migrants.

Molecular characterization of bot flies, Oestrus spp., (Diptera, Oestridae), from domestic and wild Bovidae hosts

The identification of Oestrus spp. larvae from Bovidae hosts is a difficult task due to the great morphological similarity between species. The lack of unambiguous identification criteria could have also serious epidemiological implications since domestic and wild hosts are sympatric in many natural areas. In order to accurately identify the Oestrus parasitizing hosts, we characterized two different genetic markers, 28S (rRNA) and COI, in larvae collected from domestic sheep and goats, European mouflon and Iberian ibex. Our sequence analyses demonstrate that all samples, except those from Iberian ibex, greatly resembles O. ovis and so we conclude that the species parasitizing this ibex is not O. ovis. Further studies will be needed to confirm whether it is in fact O. caucasicus, as previously suggested, or even a new species.

Population estimates, density–dependence and the risk of disease outbreaks in the Alpine ibex Capra ibex

Wildlife monitoring and the identification of factors associated with disease outbreaks are major goals in wildlife conservation. We reviewed demographic and epidemiological data for the Alpine ibex Capra ibex from 1975–2013 to characterize the species’ abundance and distribution dynamics on a large scale. We also explored methodological bias in monitoring and analyzed the factors potentially associated with the risk of disease outbreaks. Our results revealed that the overall abundance and distribution of Alpine ibex appeared to be increasing at both national and international scales, in agreement with the IUCN’s ‘Least Concern’ conservation status on the international scale and on the national scale for Italy, Switzerland and France. Our comparative analysis of common monitoring methods highlights the fact that abundance values from counts are underestimated and suggests that the Alpine ibex is more abundant than is usually reported. The appearance and persistence of disease outbreaks (e.g. sarcoptic mange, keratoconjunctivitis or brucellosis) are related to local ibex density and abundance. The observed correlation between the demographic growth of ibex populations and disease outbreaks suggests that the risk of epizooties may be increasing or might already be high in several populations of Capra ibex.

Changes in the brain and plasma Aβ peptide levels with age and its relationship with cognitive impairment in the APPswe/PS1dE9 mouse model of Alzheimer's disease

Double transgenic mice expressing mutant amyloid precursor protein (APPswe) and mutant presenilin 1 (PS1dE9) are a model of Alzheimer-type amyloidosis and are widely used in experimental studies. In the present work, the relationships between brain and plasma amyloid-β peptide (Aβ) levels and cognitive impairments were examined in male APPswe/PS1dE9 double transgenic mice at different ages. When compared with non-transgenic littermates, APPswe/PS1dE9 mice exhibited significant learning deficits from the age of 6months (M6), which were aggravated at later stages of life (M8 and M12). Sporadic brain amyloid plaques were observed in mice as early as M3 and progressively increased in number and size up to M12. A similar increase was observed in brain insoluble Aβ levels as assessed by enzyme-linked immunosorbent assay (ELISA). In particular, the levels of brain insoluble Aβ peptides rose steeply from M4 to M6. Interestingly, this pronounced amyloid deposition was accompanied by a temporary fall in the concentration of brain soluble and membrane-bound Aβ peptides at M6 that rose again at M8 and M12. The plasma levels of Aβ40 and Aβ42 decreased with advancing age up to M8, when they stabilized at M12. This decrease in plasma Aβ levels coincided with the observed increase in insoluble brain Aβ levels. These results could be useful for developing plasma Aβ levels as possible biomarkers of the cerebral amyloidosis and provide advances in the knowledge of the Aβ peptide biochemical changes that occur in the brain of Alzheimer's disease patients.

Advances in studies of disease-navigating webs: Sarcoptes scabiei as a case study

The discipline of epidemiology is the study of the patterns, causes and effects of health and disease conditions in defined anima populations. It is the key to evidence-based medicine, which is one of the cornerstones of public health. One of the important facets of epidemiology is disease-navigating webs (disease-NW) through which zoonotic and multi-host parasites in general move from one host to another. Epidemiology in this context includes (i) classical epidemiological approaches based on the statistical analysis of disease prevalence and distribution and, more recently, (ii) genetic approaches with approximations of disease-agent population genetics. Both approaches, classical epidemiology and population genetics, are useful for studying disease-NW. However, both have strengths and weaknesses when applied separately, which, unfortunately, is too often current practice. In this paper, we use Sarcoptes scabiei mite epidemiology as a case study to show how important an integrated approach can be in understanding disease-NW and subsequent disease control.

Reliability of an ELISA test for diagnosing oestrosis in Iberian ibex

Oestrosis is one of the most prevalent parasitosis affecting the Iberian ibex, Capra pyrenaica . To date, both the diagnosis of oestrosis and the determination of the intensity of parasitism require the use of invasive methods (necropsy), which necessarily limit research possibilities. We analyzed the immune humoral response (IgM and IgG) against Oestrus ovis L. excretory/secretory larval antigens in 32 sera taken from Iberian ibex from the Sierra Nevada Natural Space (southern Spain). Three antigens were collected: L1OES (from L1 larvae), L2OES (L2), and L3OES (L3). Necropsy was considered as the gold standard. The percentage of ibexes harboring Oestrus spp. larvae was 88%, the mean intensity of parasitism being 16.96 ± 14.96 larvae per parasitized host (range: 2-52). In our sample, first-instar larvae (L1) were found in 9% of ibexes, while 69% of hosts carried L2 larvae and 88% L3 larvae. Positive correlations between L1 and L2 numbers, and between L2 and L3 numbers were detected. The best results with the immunoenzymatic assay were obtained using IgG antibodies against the L1OES antigens (specificity = 89%; sensitivity = 100%; positive predictive value = 100%; negative predictive value = 57%). The IgG seroprevalence against L1OES was 78%. Thus, the analysis of IgG antibodies against antigens collected from L1 O. ovis larvae would seem to be a noninvasive method for reliably diagnosing oestrosis in naturally infested Iberian ibex. Nevertheless, additional immunological and methodological advances are still required because false positive and false negative results still represent a non-negligible part of the results of the ELISA tests.

Trophy hunting, size, rarity and willingness to pay: inter–specific analyses of trophy prices require reliable specific data

Awareness of the importance of the wildlife trade and human perception in animal conservation is growing. Recent studies carried out on a continental and world scale have analysed the associations between trophy score, rarity and prices. As a large range of ungulates are legally hunted throughout the world and numerous ungulate taxa are threatened, the relationship between rarity and trophy prices has been studied in several species. This article briefly reviews verifiable data on species and trophy prices and compares findings with data used in recent articles. The findings show that several elements of intra–specific data were inadequately addressed and that the trophy prices considered were not necessarily representative of real trophy prices. Furthermore, the body mass used for numerous taxa did not fit current knowledge of species, and several subspecies and rarity indexes that were considered disagreed with recognized subspecies or with the real conservation status of taxa. Thus, caution should be taken when considering some reported results. To improve our understanding of the associations between wildlife trade and wildlife conservation, further studies should take into account reliable specific data, such as that from government agencies, rather than publicity data.

Effect of age and severity of cognitive dysfunction on two simple tasks in pet dogs

Dogs exhibit age-dependent losses in learning and memory as well as a progressive accumulation of neuropathology that parallels that observed in normal human aging and early Alzheimer's disease. These deficits have been extensively studied using a number of standard cognitive tasks in the laboratory; however, appropriate tools for their assessment in veterinary clinics are still lacking. The aim of this study was to evaluate the effect of age and the severity of cognitive dysfunction syndrome (CDS) on two simple tests conducted in a clinical setting. A food searching (FS) task and a problem-solving (PS) task were administered to young (1-4 years, n=9), middle-aged (5-8 years, n=10), cognitively unimpaired aged (≥9 years, n=31), and cognitively impaired aged (≥ 9 years, n=37) dogs. Cognitive status was classified using an owner-based questionnaire, and in the impaired group, dogs were categorized as having either mild or severe CDS. During the FS task, younger dogs (<9 years) were able to locate the food more quickly and with more success than the aged groups (≥9 years). Dogs with severe CDS exhibited poorer performance than those with mild CDS or their healthy counterparts. In the PS task, younger dogs performed better than the aged dogs in obtaining food, but there were no differences related to CDS severity. The FS task might help to better characterize cognitively affected dogs in the clinical setting than the PS task. These and similar tasks require further investigations in the field.

Intensive monitoring suggests population oscillations and migration in wild boar Sus scrofa in the Pyrenees

As few studies have analysed local variability in populations of wild boar Sus scrofa in Western Europe in recent years, our understanding of ecological processes currently affecting this species is limited. To analyse questions regarding local variability in wild boar abundance, we used information from 442 traditional drive hunts monitored throughout eight hunting periods in the Pyrenees mountain range (Urdués, N Spain). Results showed temporal oscillations in abundance, and a non–linear decrease of 23% in the number of wild boar seen per drive hunt between 2004 and 2011. Numbers of dogs and hunters per drive hunt also affected indexes of wild boar abundance. Inter–annual variations in bag size may cause overestimations of variations in boar abundance and may even deviate from the population dynamics inferred from the number of wild boars seen per drive hunt. The multimodal patterns of wild boar abundance during the hunting periods suggest migrations in the Pyrenees. Our findings highlight the limitations of hunting bag statistics in wild boar. Further studies are required to guarantee information–based sustainable management of wild boar populations.

Is nursing a kid detrimental to nonimmunological compatibility to contact-transmitted foreign bodies in female Iberian ibex (Capra pyrenaica)?

Reproductive costs may increase the susceptibility of breeding females to parasites. Compatibility may be modulated by immunity and nonimmunological factors. However, experimental tests attempting to unravel the role of nonimmunological compatibility to parasites are scarce. We experimentally infected breeding and nonbreeding females with pseudoectoparasites (PEPs) to analyse how nursing a kid affects neatness in the Iberian ibex ( Capra pyrenaica Schinz, 1838). Our results revealed that nursing a kid does not seem detrimental to neatness in female Iberian ibex in terms of nonimmunological compatibility to contact-transmitted foreign bodies. Consequently, it seems that increased susceptibility of breeding females to contact-transmitted parasites may be mainly mediated by increased exposure or increased immunological compatibility to parasites.

Applicability of major histocompatibility complex DRB1 alleles as markers to detect vertebrate hybridization: a case study from Iberian ibex × domestic goat in southern Spain

Background

Hybridization between closely related wild and domestic species is of great concern because it can alter the evolutionary integrity of the affected populations. The high allelic variability of Major Histocompatibility Complex (MHC) loci usually excludes them from being used in studies to detect hybridization events. However, if a) the parental species don’t share alleles, and b) one of the parental species possesses an exceptionally low number of alleles (to facilitate analysis), then even MHC loci have the potential to detect hybrids.

Results

By genotyping the exon2 of the MHC class II DRB1 locus, we were able to detect hybridization between domestic goats (Capra hircus) and free-ranging Iberian ibex (Capra pyrenaica hispanica) by molecular means.

Conclusions

This is the first documentation of a Capra pyrenaica × Capra hircus hybridization, which presented us the opportunity to test the applicability of MHC loci as new, simple, cost-effective, and time-saving approach to detect hybridization between wild species and their domesticated relatives, thus adding value to MHC genes role in animal conservation and management.

Effect of age and severity of cognitive dysfunction on spontaneous activity in pet dogs - part 1: locomotor and exploratory behaviour

Age-related cognitive dysfunction syndrome (CDS) has been reported in dogs and it is considered a natural model for Alzheimer's disease in humans. Changes in spontaneous activity (including locomotor and exploratory behaviour) and social responsiveness have been related to the age and cognitive status of kennel-reared Beagle dogs. The aim of this study was to assess the influence of age and severity of CDS on locomotor and exploratory behaviour of privately owned dogs. This is the first part of a two-part report on spontaneous activity in pet dogs. An open-field (OF) test and a curiosity test were administered at baseline and 6 months later to young (1-4 years, n=9), middle-aged (5-8 years, n=9), cognitively unimpaired aged (≥ 9 years, n=31), and cognitively impaired aged ( ≥ 9 years, n=36) animals. Classification of cognitive status was carried out using an owner-based observational questionnaire, and in the cognitively impaired group, the dogs were categorised as having either mild or severe cognitive impairment. Dogs were recorded during sessions in the testing room and the video-recordings were subsequently analysed. The severity of CDS (but not age) influenced locomotion and exploratory behaviour so that the more severe the impairment, the higher the locomotor activity and frequency of corner-directed (aimless) behaviours, and the lower the frequency of door-aimed activities. Curiosity directed toward novel stimuli exhibited an age-dependent decline although severely affected animals displayed more sniffing episodes directed towards the objects. OF activity did not change after 6 months. Testing aged pet dogs for spontaneous behaviour might help to better characterise cognitively affected individuals.

Effect of age and severity of cognitive dysfunction on spontaneous activity in pet dogs - part 2: social responsiveness

Changes in social interactions with owners and other dogs are frequently observed in dogs with cognitive dysfunction syndrome (CDS). The aim of this work was to assess the effect of age and severity of CDS on social responsiveness. This is the second part of a 2-part report on spontaneous activity in pet dogs. A human interaction test and a mirror test were administered at baseline and 6 months later to assess social responses to humans and conspecifics, respectively, to four groups of privately-owned dogs: young (n=9), middle-aged (n=9), cognitively unimpaired aged (n=31), and cognitively impaired aged (n=36). The severity of cognitive impairment was considered in the last group and dogs were categorised as having either mild or severe CDS. The influence of the person and the mirror on locomotion and exploratory behaviour was also studied. Dogs were recorded in a testing room and the video recordings were subsequently analysed. Young dogs displayed more interactions involving physical contact with a person. Young and middle-aged dogs showed more vocalisations in response to social isolation. In contrast, aged animals spent more time in front of the mirror. Changes in social responsiveness associated with severe CDS included decreased response to social isolation and human interaction and increased time in front of the mirror, suggesting a deficit in habituation. Testing of spontaneous activity might help to characterise CDS in aged dogs, a condition increasingly diagnosed in veterinary clinics and a potentially useful natural model of Alzheimer's disease in humans.

Usefulness of estimated surface area of damaged skin as a proxy of mite load in the monitoring of sarcoptic mange in free-ranging populations of Iberian wild goat, Capra pyrenaica

In this study we examined the influence of several factors, like the surface of skin with lesions attributable to Sarcoptes scabiei, the time of year and host sex and age on variations of mite load in Iberian wild goats, Capra pyrenaica, from the Sierra Nevada Natural Space, southern Spain. As well, the surface area of skin with scabietic lesions estimated during field surveys were compared with measurements taken in the laboratory and the potential for using categories based on surface areas estimated during monitoring and management programs was analyzed. The surface area of the skin lesions measured in the laboratory and the time of year were the main factors affecting mite load. Results also revealed discrepancies between the surface area of lesions estimated in the field and those measured in the laboratory. The highest error percentages were associated with lesions ranging between 25 and 75% of host skin surface area. By reducing the number of categories of mange infestation (from 5 to 3) the proportion of cases correctly classified using data from field surveys increases. Our analyses suggest that the estimated surface areas of scabietic lesions is a useful relative index of mite abundance and/or intensity of parasitation in Iberian wild goat. Therefore, we conclude that revised classifications should be used in the monitoring of sarcoptic mange in wild populations, since data can be obtained in an inexpensive, fast and non-invasive fashion.

Negative effect of the arthropod parasite, Sarcoptes scabiei, on testes mass in Iberian ibex, Capra pyrenaica

Testes mass is a key factor in male reproductive success and is potentially exposed to so-called 'parasitic castration'. This is the result of the direct destruction or alteration of reproductive cell lineages (parasitic castration sensu stricto), or the indirect detrimental effects - for example, via body condition - on the ability of progenitors to produce or rear offspring (parasitic castration sensu lato). There are enormous gaps in our knowledge on the effects of parasites on the testes of wild mammals and in an attempt to rectify this dearth of data we examined the relationship between the skin parasite Sarcoptes scabiei and testes mass in Iberian ibex Capra pyrenaica. We considered data from 222 males that were culled in the population from the Sierra Nevada in Spain. Our results provide evidence that sarcoptic mange is associated with reduced size-corrected testes mass in Iberian ibex which supports the hypothesis that parasitism is a determining factor in gonad plasticity in male mammals. We discuss several hypothetical causes of this relationship and highlight the need to deepen the sub-lethal effects of pathogens if we are to accurately understand their modulator effects on host population dynamics.

Memantine versus donepezil in mild to moderate Alzheimer's disease: a randomized trial with magnetic resonance spectroscopy

BACKGROUND AND PURPOSE

To compare memantine with the most prescribed cholinesterase inhibitor (donepezil) from a clinical viewpoint when administered in early phases of Alzheimer disease (AD), and to find out whether memantine may produce changes in brain metabolite concentrations in comparison with donepezil.

METHODS

In this comparative rater-blinded parallel group randomized trial we recruited a consecutive sample of patients with probable mild to moderate AD. At baseline we carried out neuropsychological assessment with mini-mental, Clinical Dementia Rating Scale (CDR), Blessed Dementia Rating Scale, Alzheimer's Disease Assessment Scale, cognitive part (ADAS-cog), neuropsychiatric inventory (NPI), and disability assessment for dementia (DAD), as well as (1)H magnetic resonance spectroscopy (MRS) in several areas of the brain. Patients were randomized to receive either donepezil or memantine for 6 months. After this elapse of time we repeated the same procedures and observed the changes in clinical scales (ADAS-cog, NPI, DAD), as well as the changes in metabolite levels in every area of exploration (temporal, pre-frontal, posterior cingulated (PCG), and occipital), especially those of N-acetyl-aspartate (NAA) which is regarded as a surrogate marker of neuronal density.

RESULTS

A total of sixty-three patients completed the trial. We did not see significant differences in clinical scales and metabolite levels between those on donepezil (n = 32) and those on memantine (n = 31). In general, more patients worsened than improved on either of the drugs. The changes in the NAA/creatine ratio in the PCG correlated significantly with the changes in the ADAS-cog (P = 0.004).

CONCLUSIONS

Donepezil and memantine have similar modest clinical and spectroscopic effect on mild to moderate AD. MRS could be useful to monitor progression of the disease.

Sarcoptes scabiei: Specific immune response to sarcoptic mange in the Iberian ibex Capra pyrenaica depends on previous exposure and sex

Host acquired immunity is a critical factor that conditions the survival of parasites. Nevertheless, there is a shortage of data concerning inter-individual immunological inequalities in wild mammals. Sarcoptic mange is a widespread parasitosis that severely affects mammals such as the Iberian ibex (Capra pyrenaica). Despite some work on the subject, the immune response to sarcoptic mange infestation is still a complex and poorly understood phenomenon. To improve knowledge of the host-Sarcoptes immunological interaction, 18 Iberian ibexes were experimentally infested. IgG levels were assessed using ELISA to test for potential factors determining the specific immune response to infestation. Previous exposure and sex appeared to affect the IgG response to infestation and our results suggest a sex-biased immunomodulation. We discuss the immunological pattern of host-Sarcoptes interactions and also suggest further lines of work that may improve the understanding of immunological interactions of host-Sarcoptes systems.

Pharmacokinetic interaction between rifampicin and ritonavir-boosted atazanavir in HIV-infected patients

BACKGROUND

Tuberculosis (TB) is a common opportunistic infection among HIV-infected people, and rifampicin is an important drug for the treatment of TB. However, administration of rifampicin in combination with antiretroviral therapy, particularly protease inhibitors, is difficult because of drug-drug interactions.

METHODS

We have performed a prospective study in three HIV-infected patients with TB treated with a rifampicin-containing regimen (rifampicin 600 mg per day) and antiretroviral therapy including only nucleoside reverse transcriptase inhibitors (NRTIs) plus atazanavir 300 mg once a day (qd) and ritonavir 100 mg qd, to evaluate whether the inducing effect of rifampicin on the drug-metabolizing enzyme cytochrome P450 (CYP) 3A4 could be overcome by the inhibitory effect of ritonavir. A complete pharmacokinetic evaluation of the steady-state concentrations of atazanavir and ritonavir was performed.

RESULTS

In all three cases, more than 50% of the time the atazanavir level was below the minimum recommended trough plasma level (150 ng/mL according to current pharmacokinetic guidelines) to inhibit HIV wild-type replication.

CONCLUSION

These results strongly indicate that the administration of rifampicin with a combination of atazanavir 300 mg qd plus ritonavir 100 mg qd must be avoided because subtherapeutic concentrations of atazanavir are produced.

Impact of steady-state lopinavir plasma levels on plasma lipids and body composition after 24 weeks of lopinavir/ritonavir-containing therapy free of thymidine analogues

OBJECTIVES

To study the impact of lopinavir/ritonavir-containing therapy on plasma lipids and body fat of HIV-infected adults and to assess whether lopinavir plasma levels at steady state are correlated with plasma lipids and body fat after 24 weeks.

METHODS

Patients had their antiretroviral therapy switched to an antiretroviral regimen containing lopinavir/ritonavir plus one or two non-thymidine analogues. Body composition was assessed by dual energy X-ray absorptiometry at baseline and at week 24 and an intensive pharmacokinetic (PK) 12 h profile was performed at week 2.

RESULTS

Twenty-six patients were included. Plasma triglycerides (from 206 mg/dL to 261 mg/dL, P = 0.09) and total cholesterol (from 201 to 206 mg/dL, P = 0.03) increased from baseline to week 24. There was a significant rise in total fat (from 10.9 to 11.9 kg, P = 0.02) and limb fat (from 3.8 to 4.4 kg, P = 0.02) from baseline to week 24. We did not find any correlation between PK lopinavir levels and changes over time for triglycerides, cholesterol or body fat composition.

CONCLUSIONS

There was an increase in plasma triglycerides and total cholesterol levels and a gain in both total and limb fat at 24 weeks, but these changes were not correlated with lopinavir plasma levels.

Inhibitory quotient as a prognostic factor of response to a salvage antiretroviral therapy containing ritonavir-boosted saquinavir. The CIVSA Study

BACKGROUND

The addition of a low dose of ritonavir to protease inhibitors (PIs) has become a widespread strategy to improve PI pharmacokinetics. As resistance is a major barrier to long-term suppression, in salvage therapy genotype and/or phenotype scoring is currently used to predict the response. We evaluated the relationship between the saquinavir (SQV) inhibitory quotient (IQ) (virtual and genotypic) and virological response.

METHODS

Eligible patients were on a PI-containing highly active antiretroviral therapy (HAART) regimen excluding SQV and had a viral load >5000 HIV-1 RNA copies/mL. The PI was switched to SQV/ritonavir (RTV) 1000/100 mg twice a day (bid) and the same two backbone nucleoside reverse transcriptase inhibitors (NRTIs) were maintained at least until week 4, when the resistance test results became available. Genotype and virtual phenotype were determined at baseline, while the SQV trough plasma concentration was determined at week 4.

RESULTS

Fifty-three patients were included in the study. Mean baseline viral load and CD4 count were 137,693 copies/mL and 263 cells/microL, respectively, the mean number of previous PIs was 2.3 and the mean number of protease gene mutations (PGMs) was 4.1. Using an on-treatment analysis, at week 16 the mean increase in CD4 count was 70.9 cells/microL, viral load was <200 copies/mL in 17 out of 37 patients (45.9%), and 30 out of 45 patients (66.7%) were considered virological responders (VRs) (viral load <200 copies/mL or viral load declined > or =1 log(10) at week 16). Median virtual phenotype was 1.3 (0.6-6.9). Baseline differences were detected between VR and non-VR populations: the mean numbers of PGMs were 3.2 and 5.8 (P<0.05), the mean numbers of SQV-associated mutations were 2 and 3.8 (P<0.05), and the mean CD4 counts were 365.9 and 184.3 cells/microL (P<0.05), respectively. Mean SQV trough concentrations at week 4 were 1.1 and 1.0 microg/mL (not significant), and mean virtual IQs were 0.7 and 0.1 (P<0.01), respectively. Multivariate analysis showed that baseline PGMs >5 or SQV-associated mutations>5, virtual phenotype, baseline viral load >50,000 copies/mL, and virtual IQ <0.5, but not genotypic IQ, were the variables independently associated with non-VR.

CONCLUSION

In heavily pretreated patients, the use of SQV virtual IQ or alternatively virtual phenotype, as well as PGMs, is a useful tool for the prediction of virological response.

Penetration of levofloxacin into the anterior chamber (aqueous humour) of the human eye after intravenous administration

In the study presented here, levofloxacin concentrations in serum samples and the aqueous humour (AH) of 16 patients undergoing cataract extraction were measured in order to determine the penetration characteristics of levofloxacin into the AH of the non-inflamed human eye. Cataract removal was performed at various times (from 90 to 270 min) after the end of a 30-min intravenous infusion of 500 mg of levofloxacin. Serum samples were obtained 1 h after the end of levofloxacin administration (Cmax); AH and a second serum sample were taken simultaneously during the operation, and the concentrations of levofloxacin in AH (C(AH)) and serum (C(S)) were determined using a rapid high-performance liquid chromatography assay. The mean Cmax was 6.07 microg/ml (range 3.75-9.53 microg/ml, SD 1.83). The mean C(AH) at the first hour following levofloxacin administration was 1.37 microg/ml (range 1.17-1.6 microg/ml, SD 0.22) and the mean ratio (R=C(AH)/C(S)) was 0.26 (range 0.24-0.3, SD 0.02). The mean C(AH) at 125-270 min following levofloxacin administration was 1.39 microg/ml (range 0.82-1.98 microg/ml, SD 0.33) and the mean R was 0.3 (range 0.15-0.53, SD 0.11). Of 16 patients, 15 had a C(AH) of >1 microg/ml 1 h after levofloxacin administration. In conclusion, 1 h after administration of 500 mg of levofloxacin, the levels obtained were higher than the MIC at which 90% of methicillin-susceptible Staphylococcus aureus and certain gram-negative bacteria strains are inhibited.

[Experimental models for Alzheimer's disease research]

INTRODUCTION AND DEVELOPMENT

Current animal models for Alzheimer's research include transgenic mice that express a mutant form of human beta-amyloid precursor protein (APP). However, the mutant mice with the human APP transgene also have their own endogenous APP gene, which may interfere with APP processing to generate beta-amyloid peptide.

CONCLUSION

By genetic and immunochemical analyses, our laboratory has discovered that there are animals in the nature, the chick embryo and the dog in particular, which may be better experimental models than the transgenic mice, because they contain the same machinery as humans to process APP and they are easier to access, manipulate or explore their neurology. These species may be natural experimental models to study the cell biology of Alzheimer's APP and potential assay systems for drugs used to regulate beta-amyloid production as well as for the assay of new therapeutic strategies against so devasting disease.

The chick embryo appears as a natural model for research in beta-amyloid precursor protein processing

This study reveals that the chick embryo has active the machinery for the production and degradation of the amyloid beta peptide characteristic of Alzheimer's disease. We cloned the principal beta-amyloid precursor protein isoforms in the chick embryo and observed that they are highly homologous to the human sequences and identical at the C-terminal sequence, including the amyloid beta domain. Mammals such as rat or mouse, more commonly used as animal models of human diseases, have a distinct amyloid beta sequence. The distribution of beta-amyloid precursor protein isoforms in the chick embryo revealed that, as in humans, their expression is ubiquitous and the prototype beta-amyloid precursor protein-695 predominated in the nervous system. We also found that the chick embryo expresses the genes for the main proteolytic proteases implicated in the production of amyloid beta, including BACE-1, BACE-2, presenilin-1, presenilin-2 and nicastrin, as well as the amyloid beta-degrading enzyme neprilysin, or ADAM-17, a protease implicated in the non-amyloidogenic processing of beta-amyloid precursor protein. We have also found that between amyloid beta40 and amyloid beta42, this latter seems to be the major amyloid beta peptide produced during chick embryogenesis. The chick embryo appears as a suitable natural model to study cell biology and developmental function of beta-amyloid precursor protein and a potential assay system for drugs that regulate beta-amyloid precursor protein processing.