Bird species with wider geographical ranges have higher blood parasite diversity but not prevalence across the African-Eurasian flyway

Avian blood parasites, from the genera Plasmodium, Haemoproteus and Leucocytozoon, are predicted to alter their range and prevalence as global temperatures change, and host and vector ranges shift. Understanding large-scale patterns in the prevalence and diversity of avian malaria and malaria-like parasites is important due to an incomplete understanding of their effects in the wild, where studies suggest even light parasitaemia can potentially cause rapid mortality, especially in naïve populations. We conducted phylogenetically controlled analyses to test for differences in prevalence and lineage diversity of haemoparasite infection (for Plasmodium, Haemoproteus and Leucocytozoon) in and between resident and migratory species along the African-Eurasian flyway. To test whether migratory strategy or range size drives differences in parasite prevalence and diversity between resident and migrant species, we included three categories of resident species: Eurasian only (n = 36 species), African only (n = 41), and species resident on both continents (n = 17), alongside intercontinental migrants (n = 64), using a subset of data from the MalAvi database comprising 27,861 individual birds. We found that species resident on both continents had a higher overall parasite diversity than all other categories. Eurasian residents had lower Plasmodium diversity than all other groups, and both migrants and species resident on both continents had higher Haemoproteus diversity than both African and Eurasian residents. Leucocytozoon diversity did not differ between groups. Prevalence patterns were less clear, with marked differences between genera. Both Plasmodium and Leucocytozoon prevalence was higher in species resident on both continents and African residents than in migrants and Eurasian residents. Haemoproteus prevalence was lower in Eurasian residents than species resident on both continents. Our findings contrast with previous findings in the North-South American flyway, where long-distance migrants had higher parasite diversity than residents and short-distance migrants, although we found contrasting patterns for parasite diversity to those seen for parasite prevalence. Crucially, our results suggest that geographic range may be more important than migratory strategy in driving parasite diversity within species along the African-Palaearctic flyway. Our findings differ between the three parasite genera included in our analysis, suggesting that vector ecology may be important in determining these large-scale patterns. Our results add to our understanding of global patterns in parasite diversity and abundance, and highlight the need to better understand the influence of vector ecology to understand the drivers of infection risk and predict responses to environmental change.

Parasite exchange and hybridisation at a wild-feral-domestic interface

Interactions between wild, feral, and domestic animals are of economic and conservation significance. The pigeon Columba livia is a synanthropic species in a feral form, but it also includes the rare Rock Dove. Columba livia is an important player at the wild-domestic interface, acting as a carrier of avian diseases, and the feral form threatens Rock Doves with extinction via hybridisation. Despite its abundance, little is known about drivers of disease prevalence in C. livia, or how disease and hybridisation represent synergistic threats to Rock Doves. We focused on infection by the parasite Trichomonas, first collating prevalence estimates in domestic and free-living populations from relevant studies of C. livia. Second, we characterised variation in the diversity and prevalence of Trichomonas among three C. livia populations in the United Kingdom: a feral, a Rock Dove, and a feral-wild hybrid population. Across multiple continents, free-living pigeons had lower Trichomonas infection than captive conspecifics, but the effect was weak. Environmental factors which could impact Trichomonas infection status did not explain variation in infection among populations. Among the British populations, strain diversity varied, and there was lower parasite prevalence in Rock Doves than feral pigeons. Individual infection status was not explained by the available covariates, including hybrid score and site. The drivers of Trichomonas prevalence are unclear, perhaps due to idiosyncratic local-scale drivers. However, given the population-level variation in both infection prevalence and introgressive hybridisation, the potential combined effects could accelerate the extinction of the Rock Dove. Further study of the synergistic effects of multiple types of biotic interactions at the wild-feral-domestic interface is warranted, especially where vagile, globally distributed and superabundant animals are involved.

Successful storage of Trichomonas gallinae on Whatman FTA cards following culture

Logistical constraints concerning parasite sample storage can hinder progress with the discovery of genetic variation on a global scale. New storage methods are being developed to address this, but require testing in order to understand how widely applicable these methods are. Whatman FTA cards have been tested previously under laboratory conditions for storing low-concentration Trichomonas gallinae isolates with the conclusion that they are not suitable, but have not been tested under field conditions. Here, we conducted a field-test, comparing FTA cards with storage in ethanol for T. gallinae samples collected and cultured from wild Columbiformes in Africa using standard field methods, before transportation to the UK. After 6 months storage, both methods resulted in an overall prevalence of 100% following PCR amplification (n = 59), suggesting that FTA cards are suitable for estimation of T. gallinae prevalence. However, samples stored in ethanol produced more, and longer, sequences than those stored on FTA cards. These data suggest storage in ethanol is preferable for the acquisition of high quality genetic strain data, but that FTA cards can be used successfully to ascertain infection prevalence and identify parasite strains under field conditions.

Assessing rates of parasite coinfection and spatiotemporal strain variation via metabarcoding: insights for the conservation of European Turtle Doves Streptopelia turtur

Understanding the frequency, spatiotemporal dynamics and impacts of parasite coinfections is fundamental to developing control measures and predicting disease impacts. The European turtle dove (Streptopelia turtur) is one of Europe's most threatened bird species. High prevalence of infection by the protozoan parasite Trichomonas gallinae has previously been identified, but the role of this and other coinfecting parasites in turtle dove declines remains unclear. Using a high‐throughput sequencing approach, we identified seven strains of T. gallinae, including two novel strains, from ITS1/5.8S/ITS2 ribosomal sequences in turtle doves on breeding and wintering grounds, with further intrastrain variation and four novel subtypes revealed by the iron‐hydrogenase gene. High spatiotemporal turnover was observed in T. gallinae strain composition, and infection was prevalent in all populations (89%–100%). Coinfection by multiple Trichomonas strains was rarer than expected (1% observed compared to 38.6% expected), suggesting either within‐host competition, or high mortality of coinfected individuals. In contrast, coinfection by multiple haemosporidians was common (43%), as was coinfection by haemosporidians and T. gallinae (90%), with positive associations between strains of T. gallinae and Leucocytozoon suggesting a mechanism such as parasite‐induced immune modulation. We found no evidence for negative associations between coinfections and host body condition. We suggest that longitudinal studies involving the recapture and investigation of infection status of individuals over their lifespan are crucial to understand the epidemiology of coinfections in natural populations.

Forest maturity has a stronger influence on the prevalence of spider monkeys than howler monkeys in an anthropogenically impacted rainforest landscape

The transformation and depletion of primary forest over the past few decades have placed almost half of the world’s primate species under the threat of extinction. Developing any successful conservation program for primates requires distribution and demography data, as well as an understanding of the relationships between these factors and their habitat. Between March and June 2010 and 2011 we collected data on the presence and demographic parameters of howler and spider monkeys by carrying out surveys, and validated our findings using local knowledge. We then examined the relationship between forest type and the presence of these primates at 54 sites in the northern area of the Selva Zoque Corridor, Mexico. We detected 86 spider monkey groups across 31 plots and censused 391 individuals (mean ± SD = 5.9 ± 3.0 individuals per sub-group, n = 67 sub-groups). We also detected 69 howler monkey groups across 30 plots and censused 117 individuals (mean ± SD = 5.3 ± 2.4 individuals per group, n = 22 groups). Howler monkey presence was not related to any specific vegetation type, while spider monkeys were present in areas with a higher percentage of tall forest (trees > 25 m high). Overall, spider monkeys were more prevalent than howler monkeys in our sampling sites and showed demographic characteristics similar to those in better protected areas, suggesting that the landscape features in the Uxpanapa Valley are suitable for their needs. Conversely, howler monkey presence was found to be more limited than in other regions, possibly due to the extended presence of spider monkeys.

Fungal microbiomes are determined by host phylogeny and exhibit widespread associations with the bacterial microbiome

Interactions between hosts and their resident microbial communities are a fundamental component of fitness for both agents. Though recent research has highlighted the importance of interactions between animals and their bacterial communities, comparative evidence for fungi is lacking, especially in natural populations. Using data from 49 species, we present novel evidence of strong covariation between fungal and bacterial communities across the host phylogeny, indicative of recruitment by hosts for specific suites of microbes. Using co-occurrence networks, we demonstrate marked variation across host taxonomy in patterns of covariation between bacterial and fungal abundances. Host phylogeny drives differences in the overall richness of bacterial and fungal communities, but the effect of diet on richness was only evident in the mammalian gut microbiome. Sample type, tissue storage and DNA extraction method also affected bacterial and fungal community composition, and future studies would benefit from standardized approaches to sample processing. Collectively these data indicate fungal microbiomes may play a key role in host fitness and suggest an urgent need to study multiple agents of the animal microbiome to accurately determine the strength and ecological significance of host-microbe interactions.

The genome sequence of the European turtle dove, Streptopelia turtur Linnaeus 1758

We present a genome assembly from an individual female Streptopelia turtur (the European turtle dove; Chordata; Aves; Columbidae). The genome sequence is 1.18 gigabases in span. The majority of the assembly is scaffolded into 35 chromosomal pseudomolecules, with the W and Z sex chromosomes assembled.

The genome sequence of the European robin, Erithacus rubecula Linnaeus 1758

We present a genome assembly from an individual female Erithacus rubecula (the European robin; Chordata; Aves; Passeriformes; Turdidae). The genome sequence is 1.09 gigabases in span. The majority of the assembly is scaffolded into 36 chromosomal pseudomolecules, with both W and Z sex chromosomes assembled.

The evolution of mammalian brain size

Relative brain size has long been considered a reflection of cognitive capacities and has played a fundamental role in developing core theories in the life sciences. Yet, the notion that relative brain size validly represents selection on brain size relies on the untested assumptions that brain-body allometry is restrained to a stable scaling relationship across species and that any deviation from this slope is due to selection on brain size. Using the largest fossil and extant dataset yet assembled, we find that shifts in allometric slope underpin major transitions in mammalian evolution and are often primarily characterized by marked changes in body size. Our results reveal that the largest-brained mammals achieved large relative brain sizes by highly divergent paths. These findings prompt a reevaluation of the traditional paradigm of relative brain size and open new opportunities to improve our understanding of the genetic and developmental mechanisms that influence brain size.

High prevalence of the neonicotinoid clothianidin in liver and plasma samples collected from gamebirds during autumn sowing

Since neonicotinoid insecticides were introduced to the agricultural market, evidence of the negative impacts of these systemic compounds on non-target species has accumulated. Birds are one of the largest groups of species to inhabit farmland, but the extent of neonicotinoid exposure in avian communities is poorly understood and very little is known about how any exposure may affect wild birds. Here, free-living gamebirds were used as a model group to measure the extent of avian exposure to the neonicotinoid clothianidin via seed treatment. During a typical sowing period of winter cereals treated with clothianidin, blood and liver samples were collected simultaneously from individual hunted gamebird carcasses, both pre- (n = 18) and post-sowing (n = 57) and were analysed for clothianidin via LC/MS-MS. Body weight, fat score and faecal parasite load were also quantified in the birds to ascertain whether any of these health parameters were associated with clothianidin exposure under field conditions. Clothianidin was detected in 6% of individuals sampled pre-sowing and 89% of individuals sampled post-sowing. The frequency of clothianidin detection in plasma samples and the concentration of clothianidin in liver and plasma samples decreased significantly between the first week and 2-4 weeks post-sowing. Faecal parasite load was positively associated with concentrations of clothianidin in the liver (but not plasma) of partridge species, but there was no association between clothianidin concentration and fat score or body weight, for either sample type. This study provides clear evidence that treated seed is a source of pesticide exposure for gamebirds following autumn sowing. These findings have implications for gamebirds worldwide where seed treatments are in use, and will aid the design of any future avian biomonitoring studies for agrochemical compounds.

From seeds to plasma: Confirmed exposure of multiple farmland bird species to clothianidin during sowing of winter cereals

Neonicotinoids are the largest group of systemic insecticides worldwide and are most commonly applied as agricultural seed treatments. However, little is known about the extent to which farmland birds are exposed to these compounds during standard agricultural practices. This study uses winter cereal, treated with the neonicotinoid clothianidin, as a test system to examine patterns of exposure in farmland birds during a typical sowing period. The availability of neonicotinoid-treated seed was recorded post-sowing at 39 fields (25 farms), and camera traps were used to monitor seed consumption by wild birds in situ. The concentration of clothianidin in treated seeds and crop seedlings was measured via liquid chromatography-tandem mass spectrometry, and avian blood samples were collected from 11 species of farmland bird from a further six capture sites to quantify the prevalence and level of clothianidin exposure associated with seed treatments. Neonicotinoid-treated seeds were found on the soil surface at all but one of the fields surveyed at an average density of 2.8 seeds/m². The concentration of clothianidin in seeds varied around the target application rate, whilst crop seedlings contained on average 5.9% of the clothianidin measured in seeds. Exposure was confirmed in 32% of bird species observed in treated fields and 50% of individual birds post-sowing; the median concentration recorded in positive samples was 12 ng/mL. Results here provide clear evidence that a variety of farmland birds are subject to neonicotinoid exposure following normal agricultural sowing of neonicotinoid-treated cereal seed. Furthermore, the widespread availability of seeds at the soil surface was identified as a primary source of exposure. Overall, these data are likely to have global implications for bird species and current agricultural policies where neonicotinoids are in use, and may be pertinent to any future risk assessments for systemic insecticide seed treatments.

Using long-term datasets to assess the impacts of dietary exposure to neonicotinoids on farmland bird populations in England

Over the last 20 years, a new group of systemic insecticides-the neonicotinoids-has gained prominence in arable systems, and their application globally has risen year on year. Previous modelling studies using long-term data have suggested that neonicotinoid application has had a detrimental impact on bird populations, but these studies were either limited to a single species or neglected to analyse specific exposure pathways in conjunction with observed population trends. Using bird abundance data, neonicotinoid usage records and cropping data for England at a 5x5 km resolution, generalised linear mixed models were used to test for spatio-temporal associations between neonicotinoid use and changes in the populations of 22 farmland bird species between 1994 and 2014, and to determine whether any associations were explained by dietary preferences. We assigned farmland bird species to three categories of dietary exposure to neonicotinoids based on literature data for species diets and neonicotinoid residues present in dietary items. Significant estimates of neonicotinoid-related population change were obtained for 13 of the 22 species (9 positive effects, 4 negative effects). Model estimates for individual species were not collectively explained by dietary risk categories, so dietary exposure to neonicotinoids via ingestion of treated seeds and seedlings could not be confirmed as a causal factor in farmland bird declines. Although it is not possible to infer any generic effect of dietary exposure to neonicotinoids on farmland bird populations, our analysis identifies three species with significant negative estimates that may warrant further research (house sparrow Passer domesticus, skylark Alauda arvensis and red-legged partridge Alectoris rufa). We conclude that there was either no consistent effect of dietary exposure to neonicotinoids on farmland bird populations in England, or that any over-arching effect was not detectable using our study design. The potential for indirect effects of insecticide use on bird populations via reduced food availability was not considered here and should be a focus for future research.

Molecular and morphological characterization of Hepatozoon spp. in Brazilian snakes

The genus Hepatozoon represents one of six genera in the hemogregarine group. Some studies in snakes indicated effects in the host, from slight influences on fitness to severe effects on growth rate, reproduction and offspring survival rates. Diagnosis and identification are usually through blood smear analyses; but not all infected animals show parasitemia. Based on this, the present study established an adapted molecular protocol to identify Hepatozoon spp. to be used as a complementary test for routine diagnoses at the Clinical Analysis Laboratory at São Paulo Zoological Park Foundation. The study was conducted with 113 individuals. Microscopical analysis and molecular techniques were used to identify the parasite. Microscopic analyses showed 13.3% of the samples to be positive. The first pair of primers, targeting 18S rRNA gene, amplified parasite DNA in 6.3% of the samples. The second pair of primers, targeting Apicoplast fragment, were used only on samples that were identified microscopically as being positive, detecting the presence of parasite DNA in 93.3% of these. Phylogenetic analysis of the resulting sequences found five clusters for the 18S gene and five clusters for the Apicoplast fragment. Studies involving Hepatozoon spp. are still scarce and limited, mainly in snakes and the impacts of this parasite on the vertebrate host, so diagnostic studies are essential for wildlife conservation, especially in ex situ work.

The decline of the Turtle Dove: Dietary associations with body condition and competition with other columbids analysed using high-throughput sequencing

Dietary changes linked to the availability of anthropogenic food resources can have complex implications for species and ecosystems, especially when species are in decline. Here, we use recently developed primers targeting the ITS2 region of plants to characterize diet from faecal samples of four UK columbids, with particular focus on the European turtle dove (Streptopelia turtur), a rapidly declining obligate granivore. We examine dietary overlap between species (potential competition), associations with body condition in turtle doves and spatiotemporal variation in diet. We identified 143 taxonomic units, of which we classified 55% to species, another 34% to genus and the remaining 11% to family. We found significant dietary overlap between all columbid species, with the highest between turtle doves and stock doves (Columba oenas), then between turtle doves and woodpigeons (Columba palumbus). The lowest overlap was between woodpigeons and collared doves (Streptopelia decaocto). We show considerable change in columbid diets compared to previous studies, probably reflecting opportunistic foraging behaviour by columbids within a highly anthropogenically modified landscape, although our data for nonturtle doves should be considered preliminary. Nestling turtle doves in better condition had a higher dietary proportion of taxonomic units from natural arable plant species and a lower proportion of taxonomic units from anthropogenic food resources such as garden bird seed mixes and brassicas. This suggests that breeding ground conservation strategies for turtle doves should include provision of anthropogenic seeds for adults early in the breeding season, coupled with habitat rich in accessible seeds from arable plants once chicks have hatched.

New universal ITS2 primers for high-resolution herbivory analyses using DNA metabarcoding in both tropical and temperate zones

DNA metabarcoding is a rapidly growing technique for obtaining detailed dietary information. Current metabarcoding methods for herbivory, using a single locus, can lack taxonomic resolution for some applications. We present novel primers for the second internal transcribed spacer of nuclear ribosomal DNA (ITS2) designed for dietary studies in Mauritius and the UK, which have the potential to give unrivalled taxonomic coverage and resolution from a short-amplicon barcode. In silico testing used three databases of plant ITS2 sequences from UK and Mauritian floras (native and introduced) totalling 6561 sequences from 1790 species across 174 families. Our primers were well-matched in silico to 88% of species, providing taxonomic resolution of 86.1%, 99.4% and 99.9% at the species, genus and family levels, respectively. In vitro, the primers amplified 99% of Mauritian (n = 169) and 100% of UK (n = 33) species, and co-amplified multiple plant species from degraded faecal DNA from reptiles and birds in two case studies. For the ITS2 region, we advocate taxonomic assignment based on best sequence match instead of a clustering approach. With short amplicons of 187-387 bp, these primers are suitable for metabarcoding plant DNA from faecal samples, across a broad geographic range, whilst delivering unparalleled taxonomic resolution.

High prevalence of Trichomonas gallinae in wild columbids across western and southern Europe

Background

Avian trichomonosis is known as a widespread disease in columbids and passerines, and recent findings have highlighted the pathogenic character of some lineages found in wild birds. Trichomonosis can affect wild bird populations including endangered species, as has been shown for Mauritian pink pigeons Nesoenas mayeri in Mauritius and suggested for European turtle doves Streptopelia turtur in the UK. However, the disease trichomonosis is caused only by pathogenic lineages of the parasite Trichomonas gallinae. Therefore, understanding the prevalence and distribution of both potentially pathogenic and non-pathogenic T. gallinae lineages in turtle doves and other columbids across Europe is relevant to estimate the potential impact of the disease on a continental scale.

Results

We examined 281 samples from four wild columbid species for Trichomonas infection and determined the genetic lineages. The overall prevalence was 74%. There were significant differences between the species (P = 0.007). The highest prevalence was found in stock doves Columba oenas (86%, n = 79) followed by wood pigeons Columba palumbus (70%, n = 61) and turtle doves (67%, n = 65), while three of five collared doves Streptopelia decaocto (60%) were infected. We found seven different lineages, including four lineages present in columbids in the UK, one lineage already described from Spain and three new lineages, one of those found in a single turtle dove migrating through Italy and another one found in a breeding stock dove. Stock doves from Germany and collared doves from Malta were infected with a potentially pathogenic lineage (lineage A/B), which is known to cause lesions and mortality in columbids, raptors and finches.

Conclusions

Generally, turtle doves showed high prevalence of Trichomonas infection. Furthermore, the potentially pathogenic lineage A/B (or genotype B according to previous literature) was found in a recovering stock dove population. Both findings are worrying for these columbid species due to the occasional epidemic character of trichomonosis, which can have severe negative effects on populations.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2170-0) contains supplementary material, which is available to authorized users.

Pancarpal dissociation with palmar Capitate fracture-dislocation: Case report

Capitate fractures are rare and dislocations are even more uncommon. To our knowledge, there has been no report of a Capitate fracture with complete dislocation in the literature. Here, we present the first case of a Capitate fracture-dislocation, sustained after a motorcycle accident.

Can hedgerow management mitigate the impacts of predation on songbird nest survival?

Nest predators can have significant impacts on songbird reproductive success. These impacts may be amplified by habitat simplification and here we test whether sympathetic management of farmland hedgerows can reduce nest depredation, especially by corvids. We test whether songbirds select nest sites according to structural features of hedgerows (including nest visibility and accessibility), and whether these features influence nest predation risk. Songbirds selected nesting sites affording higher vegetation cover above the nest, increased visibility on the nest-side of the hedgerow and reduced visibility on the far side of the hedge. Nest survival was unrelated to corvid abundance and only weakly related (at the egg stage) to corvid nest proximity. Nest survival at the chick stage was higher where vegetation structure restricted access to corvid-sized predators (averaging 0.78 vs. 0.53), and at nests close to potential vantage points. Overall nest survival was sensitive to hedgerow structure (accessibility) particularly at low exposure to corvid predation, while the overall impact of corvid exposure was dependent on the relationship involving proximity to vantage points. Nest survival over the chick stage was much higher (0.67) in stock-proof, trimmed and mechanically cut hedgerows, (which tended to provide lower side visibility and accessibility) than in recently laid, remnant or leggy hedgerows (0.18). Long-term reductions in the management of British hedgerows may therefore be exposing nesting songbirds to increased predation risk. We recommend regular rotational cutting of hedgerows to maintain a dense woody structure and thereby reduce songbird nest predation.

Genomic evidence of demographic fluctuations and lack of genetic structure across flyways in a long distance migrant, the European turtle dove

BACKGROUND

Understanding how past climatic oscillations have affected organismic evolution will help predict the impact that current climate change has on living organisms. The European turtle dove, Streptopelia turtur, is a warm-temperature adapted species and a long distance migrant that uses multiple flyways to move between Europe and Africa. Despite being abundant, it is categorized as vulnerable because of a long-term demographic decline. We studied the demographic history and population genetic structure of the European turtle dove using genomic data and mitochondrial DNA sequences from individuals sampled across Europe, and performing paleoclimatic niche modelling simulations.

RESULTS

Overall our data suggest that this species is panmictic across Europe, and is not genetically structured across flyways. We found the genetic signatures of demographic fluctuations, inferring an effective population size (Ne) expansion that occurred between the late Pleistocene and early Holocene, followed by a decrease in the Ne that started between the mid Holocene and the present. Our niche modelling analyses suggest that the variations in the Ne are coincident with recent changes in the availability of suitable habitat.

CONCLUSIONS

We argue that the European turtle dove is prone to undergo demographic fluctuations, a trait that makes it sensitive to anthropogenic impacts, especially when its numbers are decreasing. Also, considering the lack of genetic structure, we suggest all populations across Europe are equally relevant for conservation.

Active blood parasite infection is not limited to the breeding season in a declining farmland bird

Avian blood parasites can have significant impacts on adult breeding birds but studies of parasitism outside the breeding season are rare, despite their potentially important implications for host-parasite dynamics. Here we investigate temporal dynamics of blood parasite infection in adult yellowhammers Emberiza citrinella . We screened blood samples collected between December and April of 2 consecutive winters using PCR. We found a high prevalence of both Haemoproteus and Leucocytozoon parasites, with a mean prevalence of 50% across 2 winters. Prevalence of both parasites was higher during the second, colder winter of the study. Temporal trends differed between the 2 genera, suggesting that chronic Haemoproteus infections gradually disappear throughout the winter but that Leucocytozoon infections exhibit a relapse during late winter, possibly coincident with reduced food availability. Our results highlight the difference in temporal dynamics between 2 blood parasite genera infecting the same host population and emphasize the need for accurate assessment of infection status at appropriate time periods when examining impacts of, and associations with, blood parasite infection. We suggest that further research should investigate the implications of over-winter infection for birds' physiology, behavior, and survival.

Avian blood parasite infection during the non-breeding season: an overlooked issue in declining populations?

Background

Pathogens and parasites can have major impacts on host population dynamics, both through direct mortality and via indirect effects. Both types of effect may be stronger in species whose populations are already under pressure. We investigated the potential for blood parasites to impact upon their hosts at the immunological, physiological and population level during the non-breeding season using a declining population of yellowhammers Emberiza citrinella as a model.

Results

Yellowhammers infected by Haemoproteus spp. showed both a reduced heterophil to lymphocyte (H:L) ratio, and an elevated standardised white blood cell (WBC) count compared to uninfected birds, indicating an immunological response to infection. Infected birds had shorter wings during the first winter of sampling but not during the second, colder, winter; survival analysis of 321 birds sampled across four winters indicated that increased wing length conferred a survival advantage.

Conclusions

We suggest that the potential impacts of blood parasite infections on over-wintering birds may have been underestimated. Further research should consider the potential impacts of sub-clinical parasite infections on the dynamics of vulnerable populations, and we suggest using declining populations as model systems within which to investigate these relationships as well as examining interactions between sub-clinical disease and other environmental stressors.

JEL Code

Q5

The utility of lung biopsy in recipients of stem cell transplantation

BACKGROUND/PURPOSE

Pulmonary infiltrates in recipients of stem cell transplantation often present as diagnostic dilemmas. Although lung biopsy may establish the diagnosis of parenchymal disease, it remains unclear whether such a procedure results in a significant change in the patient's treatment and outcome. This study evaluates the efficacy of lung biopsy in recipients of stem cell transplantation.

METHODS

The medical records of 15 stem cell transplant recipients who underwent 18 lung biopsies were reviewed. The indications for stem cell transplantation were leukemia in 10 patients, lymphoma in 2, histiocytosis in 1, neuroblastoma in 1, and Ewing's sarcoma in 1. The results of the lung biopsies were correlated to the clinical management and outcomes.

RESULTS

The overall mortality rate was 67% (10 patients). Eight of the 9 patients who required mechanical ventilatory support at the time of lung biopsy died. The pathologic diagnoses were pneumonitis in 6 biopsies, fibrosis in 6, brochiolitis obliterans organizing pneumonia in 3, hemorrhage in 2, and infarction in 1. Therapy was changed in 1 patient who improved after a course of steroids for bronchiolitis obliterans organizing pneumonia. Lung biopsy cultures were positive in 6 patients but rarely resulted in changes in antibiotic therapy.

CONCLUSIONS

Results of very few lung biopsies performed in stem cell transplant recipients redirected therapy. Furthermore, the ultimate outcome of these patients were not improved by the results of lung biopsies.

Model complexity: the fit to random data reconsidered

A recent controversy in the field of depth perception has highlighted an important aspect of model testing concerning a model's complexity, defined as the prior propensity of the model to fit arbitrary data sets. The present article introduces an index of complexity, called the mean minimum distance, defined as the average squared distance between an arbitrary data point and the prediction range of the model. It may also be expressed as a dimensionless quantity called the scaled mean minimum distance. For linear models, theoretical values for the scaled mean minimum distance and the variance of the scaled minimum distance can be readily obtained and compared against empirical estimates obtained from fits to random data. The approach is applied to resolving the question of the relative complexity of the Linear Integration model and the Fuzzy Logic of Perception model, both of which have been the subject of controversy in the field of depth perception. It is concluded that the two models are equally complex.

The spectrum of mucin-producing adenocarcinoma of the pancreas

The clinical distinction between cystic and mucinous carcinomas of the pancreas has been poorly defined. Therefore we sought to stratify the entity known as pancreatic mucinous adenocarcinoma based on pathologic and clinical criteria. Clinical data and pathology specimens were reviewed for patients (n = 40) who had been diagnosed as having mucin-producing pancreatic adenocarcinoma and had undergone either resection or intraoperative biopsy of their pancreatic tumor during a 40-year period at the UCLA Medical Center. Based on histologic criteria, three distinct classes of pancreatic adenocarcinoma were identified: mucinous noncystic (colloid) adenocarcinoma (group I), mucinous cystadenocarcinoma (group II), and ductal adenocarcinoma (group III). Based on clinical behavior, groups I and III were indistinguishable. Compared to patients from groups I and III, those from group II were younger, more likely to be female, and had a better prognosis. Among mucin-producing adenocarcinomas of the pancreas, mucinous noncystic adenocarcinoma and ductal adenocarcinoma share similar clinical features, whereas true cystic lesions represent a distinct clinical entity.

Functional and morphologic changes of the ileal mucosa after ileoanal pouch procedure

BACKGROUND

Restorative proctocolectomy is used widely for treatment of ulcerative colitis and familial polyposis coli. Limited information is available regarding the morphologic and functional adaptation of the mucosa in a functioning ileoanal pouch.

STUDY DESIGN

Ileal pouch specimens from patients who underwent pouch reconstruction (mean 7.5 years postcolectomy, n = 12) were compared with normal ileum (n = 15) and normal colon (n = 5). Amino-oligopeptidase (AOP) and maltase activity were measured as parameters of normal ileal function. Histologic samples were examined for the presence of neutrophils and plasma cells, the villus to crypt height ratio, and the degree of crypt hyperplasia, villus blunting, and goblet cell mass. Data were analyzed by analysis of variance.

RESULTS

The AOP activity in the normal ileum was 73 +/- 32 units of enzymatic activity per gram of mucosal protein; the AOP activities of the pouch and colon were 21 +/- 22 and 16 +/- 10, respectively. The maltase activity of the normal ileum measured 254 +/- 116 units of enzymatic activity per gram of mucosal protein, and the maltase activities of the pouch and colon were 57 +/- 71 units and 29 +/- 25 units, respectively. The ileal pouch mucosa demonstrated little acute inflammation and varying degrees of chronic inflammation. Morphologically, the ileal pouch mucosa demonstrated a range of adaptations, including villus blunting and crypt hyperplasia. Several specimens contained immature epithelial cells.

CONCLUSIONS

The AOP and maltase activities in mucosa from ileoanal pouches and colon were significantly lower than those in normal ileal mucosa. Ileoanal pouch mucosa from humans undergoes adaptive changes to resemble colonic mucosa both morphologically and functionally.

Repair of pectus excavatum deformities: 30 years of experience with 375 patients

OBJECTIVE

To review the surgical experience with pectus excavatum chest deformities at UCLA Medical Center during a 30-year period.

BACKGROUND

Pectus excavatum is a relatively common malformation that is often symptomatic; however, children's physicians often do not refer patients for surgical correction.

METHODS

Hospital records from 375 patients who underwent repair of pectus excavatum deformities between 1969 and 1999 were reviewed. Decrease in stamina and endurance during exercise was reported by 67%; 32% had frequent respiratory infections, 8% had chest pain, and 7% had asthma. The mean pectus severity score (width of chest divided by distance between posterior surface of sternum and anterior surface of spine) was 4.65 (normal chest = 2.56). All patients had marked cardiac deviation into the left chest. Repair was performed with subperiosteal resection of the abnormal cartilages, transverse wedge osteotomy of the anterior sternum, and internal support with a steel strut for 6 months. Repair was performed on 177 children before age 11 years; 38 adults with severe symptoms underwent repair.

RESULTS

The mean hospital stay was 3.1 days. With a mean follow-up of 12.6 years, all patients with preoperative respiratory symptoms, exercise limitation, and chest pain experienced improvement. Vital capacity increased 11% (mean) within 9 months in 35 patients evaluated. There were no deaths. Complications included hypertrophic scar formation (35), atelectasis (12), pleural effusion (13), recurrent sternal depression (5), and pericarditis (3). More than 97% had a very good or excellent result.

CONCLUSION

Pectus excavatum deformities can be repaired with a low rate of complications, a short hospital stay, and excellent long-term physiologic and cosmetic results.

Reoperation after esophageal replacement in childhood

BACKGROUND

Esophageal replacement is associated with significant morbidity that may lead to operative interventions. This study reviews the management and outcome of children who underwent reoperation after esophageal replacement.

METHODS

Eighteen patients who underwent esophageal replacement from 1985 to 1997 were reviewed retrospectively. Ten patients underwent reoperation. Patient management, perioperative morbidity, and the dietary intake at follow-up were recorded for each patient.

RESULTS

Of the reoperated patients, 7 had esophageal atresia, 2 had caustic ingestion, and 1 had achalasia. Nine patients received a colon interposition, and 1 received a reverse gastric tube as the initial esophageal replacement. Seven patients required revision of the anastomoses. Three patients required complex esophageal reconstruction: 1 underwent gastric transposition, 1 underwent free jejunal graft, and 1 underwent gastric transposition combined with free jejunal graft. Seven patients were eating well at follow-up. Two patients still required partial gastrostomy tube feeding. One patient died 6 months postoperatively from aspiration pneumonia.

CONCLUSIONS

Esophageal replacement continues to be a challenging operation associated with significant complications. Most reoperative procedures were directed toward strictures and persistent fistulae. Complete graft failure can be managed by gastric transposition or free jejunal graft. Despite the perioperative morbidity, most patients have good functional outcome.

Simplifying the Waterston's stratification of infants with tracheoesophageal fistula

The survival of infants with tracheoesophageal fistula was stratified by David J. Waterston et al. in 1962. This classification has been used as a guide to direct the timing of operative intervention in these infants. This study examines the current applicability of this classification system. The hospital records of 64 infants with esophageal atresia and/or tracheoesophageal fistula were reviewed. The survival rate was analyzed as a function of the infants' risk stratification, birth weight, and additional anomalies. Twenty-three infants were in Waterston Group A, 20 infants in Group B, and 21 infants in Group C. The survival of all infants was 81 per cent. Six infants died after recognition of severe anomalies and withdrawal of care, four infants died of cardiopulmonary arrest, and two infants died of sepsis. The survival of infants in both Groups A and B was 100 per cent, in contrast to 43 per cent survival in Group C. Only infants who weighed <1800 g or had severe additional anomalies were at risk of dying. Therefore, the classification of infants with esophageal atresia and/or tracheoesophageal fistula may be simplified by combining Waterston's Groups A and B into a single risk stratum.

The influence of gestational age and mode of delivery on infants with gastroschisis

BACKGROUND/PURPOSE

It has been proposed that preterm and prelabor cesarean section may improve the outcome of infants with gastroschisis. The purpose of this study is to examine the impact of gestation and delivery method on infants with gastroschisis.

METHODS

The medical records of 60 infants with gastroschisis treated at a tertiary care center from 1985 through 1995 were reviewed retrospectively. The gestational age, the mode of delivery, the type of operative repair, and the length of hospital stay were recorded for each patient.

RESULTS

Infants born vaginally were more likely to require silo stage repair than those delivered by cesarean section (21 of 29 v. 11 of 31, P<.01). Infants born vaginally also had longer hospital stay than those delivered by cesarean section (53 v. 39 days, P = .19). Infants born before 33 weeks' of gestation stayed longer in the hospital than those born after 33 weeks. After 33 weeks' gestation, infants had similar hospital stay regardless of the gestational age.

CONCLUSIONS

Cesarean section delivery was beneficial for infants with gastroschisis. Preterm delivery did not shorten the length of hospital stay. The role of elective cesarean section delivery at term should be considered for infants with gastroschisis diagnosed antenatally.

Glucose uptake in dilated small intestine

BACKGROUND/PURPOSE

The development of dilated small intestine in patients with short bowel syndrome results in increased mucosal surface area. This study examines whether the incremental increase in surface area leads to a proportional increase in absorptive function of the small intestine.

METHODS

Partial obstruction of the small intestine was created in rats by placing an intussusception valve in the proximal jejunum. Rats that underwent sham operations served as controls. One week postoperatively, the small intestine proximal and distal to the valve was removed. The intestinal diameter proximal and distal to the obstruction was measured. The rate of glucose uptake was measured by the everted sleeve technique. The results were analyzed by analysis of variance (ANOVA).

RESULTS

The intestine proximal to the valve was significantly dilated and thickened when compared with the intestine distal to the valve. The wet mass per centimeter of the dilated segment was 2.5 times that of the control group (P<.001). The glucose uptake capacity of the dilated segment was slightly higher than that of the control group (540 v 420 nmol/min/cm, P<.05). However, the specific glucose uptake rate was reduced significantly in the intestine proximal to the valve (247 v 335 nmol/min/cm2, P<.01).

CONCLUSIONS

Although the partial obstruction of small intestine resulted in a substantial increase in the intestinal surface area, the absorptive capacity of the dilated intestine per unit surface area was decreased significantly. This translated ultimately into a slight increase in the overall functional absorptive capacity of glucose in the small intestine. These results suggest that dilated small intestine may not enhance mucosal absorption.

In vivo growth of transplanted genetically altered intestinal stem cells

PURPOSE

Intestinal stem cell transplantation is a potential method of delivering genes to the small intestine. The authors have previously demonstrated the survival of transfected intestinal stem cells implanted into the rat small intestine. This study examines the growth of genetically altered intestinal stem cells that were grown on a polycarbonate membrane and implanted into the rat small intestine.

METHODS

The IEC6 rat intestinal cell line serves as a model for intestinal stem cells. A subclone of the IEC6 cells was developed that stably expresses the lac Z gene introduced by a retroviral vector. The transfected cells were seeded at 500,000 cells/cm2 on a polycarbonate membrane. In 15 male Sprague-Dawley rats, a 0.75-cm enterotomy was created on the antimesenteric side of the small intestine 5 cm distal to the ligament of Treitz. A 0.5-cm2 segment of the membrane was sutured over the enterotomy with the cells facing away from the intestinal lumen. A segment of the omentum was wrapped around the patched enterotomy and sutured to the serosa. Three and 7 days after implantation, the implanted cells were retrieved, then fixed and stained with an X-gal solution. The number of cells was determined from the intensity of the X-gal staining. In five of the rats, frozen sections of the enterotomy sites were examined after staining with X-gal.

RESULTS

All 15 rats survived the implantation procedure. Initially, 0.32 +/- 0.11 million cells were implanted. At both 3 and 7 days, the enterotomy site still contained viable transfected cells. The number of viable cells increased substantially to 1.52 +/- 0.46 and 3.52 +/- 1.87 million cells at 3 and seven days, respectively (P < .05).

CONCLUSIONS

The polycarbonate membrane served as a good vehicle to efficiently deliver genetically altered intestinal stem cells to the small intestine. The transplanted cells continued to grow and stably expressed the gene product. This ex vivo approach to gene therapy has considerable therapeutic potential.

The outcome of research training during surgical residency

BACKGROUND/PURPOSE

The exposure to research during residency is currently an integral part of most academic surgical training programs. In this study, graduates of two surgical programs were surveyed to characterize their research experience and to determine the effects on their careers.

METHODS

Between 1975 and 1990, 86 and 61 residents completed general surgical training programs at UCLA Medical Center and at Harbor-UCLA Medical Center, respectively. An anonymous survey was sent to each graduate regarding his research experience and current practice.

RESULTS

Of the graduates who spent 2 years in research, 47% now hold academic positions, compared with 23% for those who spent less than 2 years (P = .18). When the graduates were segregated according to their desire to enter the laboratory, 49% of graduates who requested research time hold academic positions, whereas only 13% of those who would not request research are in academic positions (P = .01).

CONCLUSIONS

Residents who strongly desire a period of research during surgical residency are also more productive in the laboratory. This information should be considered in selecting residents for research training in the current era of academic budget restriction and managed health care.

Long-term quantitative results following fundoplication and antroplasty for gastroesophageal reflux and delayed gastric emptying in children

BACKGROUND

The operative management of children with combined gastroesophageal reflux and delayed gastric emptying is controversial. This study measures the long-term follow-up of gastric emptying in children who have undergone gastroesophageal fundoplication combined with antroplasty.

METHODS

Fifteen randomly selected children with gastroesophageal reflux and scintigraphically demonstrated delayed gastric emptying underwent fundoplication and antroplasty. Each patient had another gastric emptying scintigraphic study performed an average of 3.6 years postoperation.

RESULTS

All patients reported improvement of their symptoms compared with before the operation, and none required further medical therapy for gastroesophageal reflux or experienced dumping syndrome. Eleven of the 15 patients had significant long-term improvement of their gastric emptying postoperatively. The mean percent of isotope meal remaining in the stomach at 90 minutes improved from 72% preoperatively to 40% postoperatively (P = 0.0005).

CONCLUSIONS

Gastric emptying in children with gastroesophageal reflux and delayed gastric emptying is significantly improved for several years in three-fourths of patients after fundoplication and antroplasty. Fundoplication and concomitant antroplasty are recommended for symptomatic children with documented gastroesophageal reflux and delayed gastric emptying.

Improved survival of infants with omphalocele

BACKGROUND

The surgical management of patients with omphalocele has evolved over the past 4 decades. Despite many improvements in care, the reported mortality has been over 10%.

METHODS

This study reviewed the characteristics, management, and outcome of 31 patients with omphalocele who underwent surgical care between 1980 and 1995 at a single hospital.

RESULTS

Twenty-five patients had additional congenital anomalies. All but 1 patient underwent operative repair; 13 of these patients with large defects had a silo chimney constructed initially. Fourteen patients underwent primary fascial and skin closure at the initial operation. Only 1 patient died perioperatively; another patient died without operation due to other major malformations.

CONCLUSIONS

The results following surgical repair of omphalocele defects depend on the degree of visceroabdominal disproportion and on the severity of associated anomalies. The operative mortality for staged omphalocele repair with limited elevation of intraabdominal pressure is low, and the long-term quality of life of these patients is good.

Epidermal growth factor selectively enhances functional enterocyte adaptation after massive small bowel resection

After massive small bowel resection, the intestine adapts to compensate. In addition to proliferation, enterocytes also undergo selective functional adaptation. In this study we examined the effect of intraperitoneal administration of epidermal growth factor (EGF) on the expression of the brush border dissacharidase sucrase, the sodium glucose cotransporter (SGLT1), and the sodium-potassium ATPase pump (NaK ATPase) by enterocytes in the remnant intestine after massive small bowel resection. Adult Lewis rats underwent either ileal transection or 70% proximal intestinal resection. These animals were subdivided into groups that received either saline or EGF intraperitoneally for 1 week. Ilea from each group were harvested 4 weeks postoperatively. Enterocytes were separated from these segments by calcium chelation. The total protein from the isolated cells was subjected to Western blot analysis. Administration of EGF to animals that underwent transection did not significantly alter the expression of sucrase, SGLT1, or NaK ATPase. After intestinal resection, the expressions of sucrase and SGLT1 were significantly increased. The combination of EGF administration and intestinal resection resulted in a further increase in SGLT1 expression. The intraperitoneal administration of EGF selectively enhanced the expression of SGLT1 by enterocytes after massive small bowel resection. Administration of EGF to sham-operated animals did not have similar effects. These results suggest that EGF augments the adaptive response and may therefore have a therapeutic role in the management of patients with short bowel syndrome.

Management of peritoneal dialysis-induced hydrothorax in children

Continuous ambulatory peritoneal dialysis (CAPD) is a safe and effective treatment for children with end-stage renal failure. Approximately three per cent of patients develop a large hydrothorax as a result of a dialysate leak from the peritoneal cavity through an occult diaphragmatic eventration or attenuation of the pleuroperitoneal membrane. Previously, such patients often discontinued CAPD and were placed on hemodialysis even though the complications, expense, and limitation of activity with hemodialysis are undesirable in children. During the past 15 years, 6 of the 193 children (3%) undergoing CAPD at UCLA Medical Center developed a hydrothorax. Three patients were male and three were female. Four patients were treated surgically with diaphragmatic plication, one was treated by reducing the dialysate volume, and one was switched to hemodialysis in preparation for a renal transplant. Each of the four surgically-treated children was able to return to full-volume peritoneal dialysis and has not experienced recurrence of the hydrothorax. Therefore, diaphragmatic plication permits children to quickly resume full-volume CAPD and avoid hemodialysis.

Endotoxin inhibitor prevents sepsis-induced alterations in intestinal ion transport

BACKGROUND

The intestine is a target of septic insult. The aims of this study were to characterize sepsis-induced alterations in intestinal ion transport and to determine the role endotoxin plays in mediating these changes.

METHODS

Rats underwent cecal manipulation alone (control), cecal ligation and puncture (CLP), or CLP plus intraperitoneal injection of 0.2 mg of a recently synthesized endotoxin inhibitor. At 24 hours, distal ileum was harvested, and transport parameters were determined.

RESULTS

Cecal ligation and puncture produced a significant increase in short-circuit current (Isc) that was attributable to the induction of chloride secretion. There were no alterations in transepithelial resistance or fluxes of mannitol and sodium. The sepsis-induced increase in Isc was prevented by administration of the endotoxin inhibitor.

CONCLUSIONS

In this model of sepsis, the primary alteration in ileal ion transport is an induction of electrogenic chloride secretion. Endotoxin inhibition may represent a strategy for prophylaxis against the intestinal effects of sepsis.

Amiloride inhibits meal-stimulated colonic absorption

Meal-stimulated colonic absorption has recently been described, but the cellular transport mechanisms mediating this response are unknown. The purpose of this study was to determine the contribution of Na+ transport pathways to colonic proabsorption. Distal colonic Thiry-Vella loops were constructed in six dogs. Absorption was measured by infusing the loops with a physiological electrolyte solution containing [14C] polyethylene glycol as the impermeant marker. In the first set of experiments, the dose dependence of amiloride-induced inhibition of basal colonic absorption was determined. In the second set of experiments the effect of amiloride, which inhibits both Na+ channels and Na+/H+ exchange in colonocytes, on meal-stimulated colonic absorption was determined. Luminal amiloride inhibited basal colonic absorption in a dose-dependent manner, with significant reductions in Na+ absorption occurring with concentrations of 10(-2)M and higher. Infusion with 10(-3)M amiloride, a concentration that did not alter basal absorption, resulted in significant reductions in postprandial water, Na+, and Cl- absorption. These results suggest that meal-stimulated colonic absorption is mediated, at last in part, by transcellular Na+ absorptive pathways.

Enterocyte functional adaptation following intestinal resection

Following massive small bowel resection, the remaining intestine undergoes compensatory adaptation to maintain absorptive capacity. The purpose of this study was to determine the relative importance of mucosal hyperplasia and functional adaptation by individual enterocytes in this process. Distal ileum was harvested from rats 2 weeks following 70% small bowel resection or transection with reanastomosis. Transport parameters were determined in Ussing chambers. Short-circuit current (Isc) responses to additions of 3-0-methylglucose were measured to assess Na+/glucose cotransporter kinetics. Microvillus absorptive surface areas were calculated with computer-assisted morphometric modeling. These surface area values were used to normalize transport parameters. Ileal absorptive surface area was 70% greater in resection tissues than in transection tissues (P < 0.05). Na+ and Cl- fluxes were generally lower in the resection group. Na+/glucose cotransporter delta Isc max (an index of cotransporter quantity) for resection and transection tissues were 0.3 +/- 0.1 and 1.8 +/- 0.3, respectively (P < 0.05). Km (an index of cotransporter affinity for substrate) did not differ significantly. Following intestinal resection, ileal surface area increases; however, transport parameters, when normalized to absorptive surface area values, diminish. During early postresection adaptation, expansion of ileal absorptive surface area due to hyperplasia seems to play a greater role than upregulation of enterocyte Na+, Cl- , and glucose absorption.

Assessment of artificial liver support technology

Despite more than 30 yr of research and development, an artificial liver has still not yet become clinical reality. Although previous attempts using a multiplicity of techniques including hemodialysis, hemoperfusion, plasma exchange, extracorporeal perfusion, and crosshemodialysis have shown minor improvement in patients with acute hepatic failure, limited clinical trials have failed to demonstrate any survival benefit. Encouraged by the progress on techniques that maintain long-term cultures of hepatocytes, more recent efforts have been directed at the use of hepatocytes as the basis of liver support. This review takes a critical look at past and present concepts in the development of artificial liver supports and both qualitatively and quantitatively evaluates the advantages and disadvantages of the available methodology.