Pathogen surveillance in wild bottlenose dolphins Tursiops truncatus

A Systematic Review on the Role of Wildlife as Carriers and Spreaders of Campylobacter spp

Campylobacter spp. are important zoonotic pathogens and can cause one of the main bacterial diarrheal diseases worldwide. Research in the context of infection arising from transmission from other humans and other vertebrates has been extensive. A large fraction of these investigations has focused on domestic animals; however, there are also a number of publications which either totally, or at least in part, consider the role of wild or feral animals as carriers or spreaders of Campylobacter spp. Here, we carry out a systematic review to explore the role played by wild vertebrates as sources of Campylobacter spp. with a compilation of prevalence data for more than 150 species including reptiles, mammals and birds. We found that numerous vertebrate species can act as carriers of Campylobacter species, but we also found that some host specificity may exist, reducing the risk of spread from wildlife to domestic animals or humans.

Campylobacter in aquatic and terrestrial mammals is driven by life traits: A systematic review and meta-analysis

Introduction

Campylobacter spp. infections are responsible for significant diarrheal disease burden across the globe, with prevalence thought to be increasing. Although wild avian species have been studied as reservoirs of Campylobacter spp., our understanding of the role of wild mammalian species in disease transmission and persistence is limited. Host factors influencing infection dynamics in wild mammals have been neglected, particularly life traits, and the role of these factors in zoonotic spillover risk is largely unknown.

Methods

Here, we conducted a systematic literature review, identifying mammalian species that had been tested for Campylobacter spp. infections (molecular and culture based). We used logistic regression to evaluate the relationship between the detection of Campylobacter spp. in feces and host life traits (urban association, trophic level, and sociality).

Results

Our analysis suggest that C. jejuni transmission is associated with urban living and trophic level. The probability of carriage was highest in urban-associated species (p = 0.02793) and the most informative model included trophic level. In contrast, C. coli carriage appears to be strongly influenced by sociality (p = 0.0113) with trophic level still being important. Detection of Campylobacter organisms at the genus level, however, was only associated with trophic level (p = 0.0156), highlighting the importance of this trait in exposure dynamics across host and Campylobacter pathogen systems.

Discussion

While many challenges remain in the detection and characterization of Camploybacter spp., these results suggest that host life traits may have important influence on pathogen exposure and transmission dynamics, providing a useful starting point for more directed surveillance approaches.

Pathogen Exposure in White Whales (Delphinapterus leucas) in Svalbard, Norway

The Svalbard white whale (Delphinapterus leucas) population is one of the smallest in the world, making it particularly vulnerable to challenges such as climate change and pathogens. In this study, serum samples from live captured (2001−2016) white whales from this region were investigated for influenza A virus (IAV) antibodies (Abs) (n = 27) and RNA (n = 25); morbillivirus (MV) Abs (n = 3) and RNA (n = 25); Brucella spp. Abs; and Toxoplasma gondii Abs (n = 27). IAV Abs were found in a single adult male that was captured in Van Mijenfjorden in 2001, although no IAV RNA was detected. Brucella spp. Abs were found in 59% of the sample group (16/27). All MV and T. gondii results were negative. The results show that Svalbard white whales have been exposed to IAV and Brucella spp., although evidence of disease is lacking. However, dramatic changes in climate and marine ecosystems are taking place in the Arctic, so surveillance of health parameters, including pathogens, is critical for tracking changes in the status of this vulnerable population.

Vitamin B12 biosynthesis of Cetobacterium ceti isolated from the intestinal content of captive common bottlenose dolphins (Tursiops truncatus)

In comparison with terrestrial mammals, dolphins require a large amount of haemoglobin in blood and myoglobin in muscle to prolong their diving time underwater and increase the depth they can dive. The genus Cetobacterium is a common gastrointestinal bacterium in dolphins and includes two species: C. somerae and C. ceti. Whilst the former produces vitamin B₁₂, which is essential for the biosynthesis of haem, a component of haemoglobin and myoglobin, but not produced by mammals, the production ability of the latter remains unknown. The present study aimed to isolate C. ceti from dolphins and reveal its ability to biosynthesize vitamin B₁₂. Three strains of C. ceti, identified by phylogenetic analyses with 16S rRNA gene and genome-based taxonomy assignment and biochemical features, were isolated from faecal samples collected from two captive common bottlenose dolphins (Tursiops truncatus). A microbioassay using Lactobacillus leichmannii ATCC 7830 showed that the average concentration of vitamin B₁₂ produced by the three strains was 11 (standard deviation: 2) pg ml^-1. The biosynthesis pathway of vitamin B₁₂, in particular, adenosylcobalamin, was detected in the draft genome of the three strains using blastKOALA. This is the first study to isolate C. ceti from common bottlenose dolphins and reveal its ability of vitamin B₁₂ biosynthesis, and our findings emphasize the importance of C. ceti in supplying haemoglobin and myoglobin to dolphins.

Comparative Study of the Gut Microbiota Among Four Different Marine Mammals in an Aquarium

Despite an increasing appreciation in the importance of host–microbe interactions in ecological and evolutionary processes, information on the gut microbial communities of some marine mammals is still lacking. Moreover, whether diet, environment, or host phylogeny has the greatest impact on microbial community structure is still unknown. To fill part of this knowledge gap, we exploited a natural experiment provided by an aquarium with belugas (Delphinapterus leucas) affiliated with family Monodontidae, Pacific white-sided dolphins (Lagenorhynchus obliquidens) and common bottlenose dolphin (Tursiops truncatus) affiliated with family Delphinidae, and Cape fur seals (Arctocephalus pusillus pusillus) affiliated with family Otariidae. Results show significant differences in microbial community composition of whales, dolphins, and fur seals and indicate that host phylogeny (family level) plays the most important role in shaping the microbial communities, rather than food and environment. In general, the gut microbial communities of dolphins had significantly lower diversity compared to that of whales and fur seals. Overall, the gut microbial communities were mainly composed of Firmicutes and Gammaproteobacteria, together with some from Bacteroidetes, Fusobacteria, and Epsilonbacteraeota. However, specific bacterial lineages were differentially distributed among the marine mammal groups. For instance, Lachnospiraceae, Ruminococcaceae, and Peptostreptococcaceae were the dominant bacterial lineages in the gut of belugas, while for Cape fur seals, Moraxellaceae and Bacteroidaceae were the main bacterial lineages. Moreover, gut microbial communities in both Pacific white-sided dolphins and common bottlenose dolphins were dominated by a number of pathogenic bacteria, including Clostridium perfringens, Vibrio fluvialis, and Morganella morganii, reflecting the poor health condition of these animals. Although there is a growing recognition of the role microorganisms play in the gut of marine mammals, current knowledge about these microbial communities is still severely lacking. Large-scale research studies should be undertaken to reveal the roles played by the gut microbiota of different marine mammal species.

Development and evaluation of indirect enzyme-linked immunosorbent assays for the determination of immune response to multiple clostridial antigens in vaccinated captive bred southern white rhinoceros (Ceratotherium simum simum)

BACKGROUND

An overall increase in poaching of white rhinoceros results in captive breeding becoming a significant component of white rhinoceros conservation. However, this type of conservation comes with its own difficulties. When wildlife is captured, transported and/or confined to a boma environment, they are more predisposed to diseases caused by bacterial organisms such as spore forming Clostridium spp. A southern white rhinoceros (Ceratotherium simum simum) population on a captive bred farm was suspected to be affected by Clostridium infections. These endangered animals were apparently exposed to Clostridium spp., in the conservation area previously used for cattle farming. The rhinoceros population on the breeding operation property was vaccinated with a multi-component clostridial vaccine registered for use in cattle. Multiple indirect enzyme-linked immunosorbent assays (iELISAs) were developed in order to evaluate the serum antibody titres of these vaccinated animals. In evaluating vaccine efficacy, the gold standard mouse neutralization test (MNT) was not available and therefore iELISAs were developed for the detection of serum antibodies to C. perfringens type A (alpha toxin), C. chauvoei (whole cell), C. novyi (alpha toxin), C. septicum (alpha toxin) and C. sordellii (lethal toxin) in the white rhinoceros population using international reference sera of equine origin. Antibody titres against each clostridial antigen was evaluated in the vaccinated white rhinoceros population (n = 75). Analytical specificity showed slight cross-reactions for C. chauvoei and C. perfringens type A with the other antigens. Individual assay cut-off values were calculated with 95% confidence. Coefficient of variance (CV) values for both the international reference sera and in-house control sera across all the antigens were well below 16%, indicating good assay repeatability. This convenient and fast assay is suitable for monitoring humoral immune responses to clostridial antigens in vaccinated white rhinoceroses.

RESULTS

Checkerboard titrations indicated optimal antigen and antibody concentrations to be used for each respective iELISA developed. Each titration set of the respective international reference and in-house control sera showed good repeatability with low standard deviations and coefficient of variance values calculated between repeats for each antigen. Individual assays proved repeatable and showed good analytical sensitivity and specificity.

CONCLUSIONS

The developed iELISAs are able to evaluate antibody profiles of phospholipase C, C. chauvoei whole cells, TcnA, ATX, TcsL in white rhinoceros serum using international reference sera.

Putative parapoxvirus-associated foot disease in the endangered huemul deer (Hippocamelus bisulcus) in Bernardo O'Higgins National Park, Chile

The huemul (Hippocamelus bisulcus) is an endangered cervid endemic to southern Argentina and Chile. Here we report foot lesions in 24 huemul from Bernardo O’Higgins National Park, Chile, between 2005 and 2010. Affected deer displayed variably severe clinical signs, including lameness and soft tissue swelling of the limbs proximal to the hoof or in the interdigital space, ulceration of the swollen tissues, and some developed severe proliferative tissue changes that caused various types of abnormal wear, entrapment, and/or displacement of the hooves and/or dewclaws. Animals showed signs of intense pain and reduced mobility followed by loss of body condition and recumbency, which often preceded death. The disease affected both genders and all age categories. Morbidity and mortality reached 80% and 40%, respectively. Diagnostics were restricted to a limited number of cases from which samples were available. Histology revealed severe papillomatous epidermal hyperplasia and superficial dermatitis. Electron microscopy identified viral particles consistent with viruses in the Chordopoxvirinae subfamily. The presence of parapoxvirus DNA was confirmed by a pan-poxvirus PCR assay, showing high identity (98%) with bovine papular stomatitis virus and pseudocowpoxvirus. This is the first report of foot disease in huemul deer in Chile, putatively attributed to poxvirus. Given the high morbidity and mortality observed, this virus might pose a considerable conservation threat to huemul deer in Chilean Patagonia. Moreover, this report highlights a need for improved monitoring of huemul populations and synergistic, rapid response efforts to adequately address disease events that threaten the species.

Axiom Microbiome Array, the next generation microarray for high-throughput pathogen and microbiome analysis

Microarrays have proven to be useful in rapid detection of many viruses and bacteria. Pathogen detection microarrays have been used to diagnose viral and bacterial infections in clinical samples and to evaluate the safety of biological drug materials. In this study, the Axiom Microbiome Array was evaluated to determine its sensitivity, specificity and utility in microbiome analysis of veterinary clinical samples. The array contains probes designed to detect more than 12,000 species of viruses, bacteria, fungi, protozoa and archaea, yielding the most comprehensive microbial detection platform built to date. The array was able to detect Shigella and Aspergillus at 100 genome copies, and vaccinia virus DNA at 1,000 genome copies. The Axiom Microbiome Array made correct species-level calls in mock microbial community samples. When tested against serum, tissue, and fecal samples from pigs experimentally co-infected with porcine reproductive and respiratory syndrome virus and porcine circovirus type 2, the microarray correctly detected these two viruses and other common viral and bacterial microbiome species. This cost-effective and high-throughput microarray is an efficient tool to rapidly analyze large numbers of clinical and environmental samples for the presence of multiple viral and bacterial pathogens.

Bridging immunogenetics and immunoproteomics: Model positional scanning library analysis for Major Histocompatibility Complex class II DQ in Tursiops truncatus

The Major Histocompatibility Complex (MHC) is a critical element in mounting an effective immune response in vertebrates against invading pathogens. Studies of MHC in wildlife populations have typically focused on assessing diversity within the peptide binding regions (PBR) of the MHC class II (MHC II) family, especially the DQ receptor genes. Such metrics of diversity, however, are of limited use to health risk assessment since functional analyses (where changes in the PBR are correlated to recognition/pathologies of known pathogen proteins), are difficult to conduct in wildlife species. Here we describe a means to predict the binding preferences of MHC proteins: We have developed a model positional scanning library analysis (MPSLA) by harnessing the power of mixture based combinatorial libraries to probe the peptide landscapes of distinct MHC II DQ proteins. The algorithm provided by NNAlign was employed to predict the binding affinities of sets of peptides generated for DQ proteins. These binding affinities were then used to retroactively construct a model Positional Scanning Library screen. To test the utility of the approach, a model screen was compared to physical combinatorial screens for human MHC II DP. Model library screens were generated for DQ proteins derived from sequence data from bottlenose dolphins from the Indian River Lagoon (IRL) and the Atlantic coast of Florida, and compared to screens of DQ proteins from Genbank for dolphin and three other cetaceans. To explore the peptide binding landscape for DQ proteins from the IRL, combinations of the amino acids identified as active were compiled into peptide sequence lists that were used to mine databases for representation in known proteins. The frequency of which peptide sequences predicted to bind the MHC protein are found in proteins from pathogens associated with marine mammals was found to be significant (p values <0.0001). Through this analysis, genetic variation in MHC (classes I and II) can now be associated with the binding repertoires of the expressed MHC proteins and subsequently used to identify target pathogens. This approach may be eventually applied to evaluate individual population and species risk for outbreaks of emerging diseases.

Environmental Sources of Bacteria Differentially Influence Host-Associated Microbial Dynamics

These results provide valuable insights into the ecological influence of exogenous microbial exposure, as well as laying the foundation for improving aquarium management practices. By comparing data for dolphins from aquaria that use natural versus artificial seawater, we demonstrate the potential influence of aquarium water disinfection procedures on dolphin microbial dynamics.

Host-associated microbial dynamics are influenced by dietary and immune factors, but how exogenous microbial exposure shapes host-microbe dynamics remains poorly characterized. To investigate this phenomenon, we characterized the skin, rectum, and respiratory tract-associated microbiota in four aquarium-housed dolphins daily over a period of 6 weeks, including administration of a probiotic during weeks 4 to 6. The environmental bacterial sources were also characterized, including the animals’ human handlers, the aquarium air and water, and the dolphins’ food supply. Continuous microbial exposure occurred between all sites, yet each environment maintained a characteristic microbiota, suggesting that the majority of exposure events do not result in colonization. Small changes in water physicochemistry had a significant but weak correlation with change in dolphin-associated bacterial richness but had no influence on phylogenetic diversity. Food and air microbiota were the richest and had the largest conditional influence on other microbiota in the absence of probiotics, but during probiotic administration, food alone had the largest influence on the stability of the dolphin microbiota. Our results suggest that respiratory tract and gastrointestinal epithelium interactions with air- and food-associated microbes had the biggest influence on host-microbiota dynamics, while other interactions, such as skin transmission, played only a minor role. Finally, direct oral stimulation with a foreign exogenous microbial source can have a profound effect on microbial stability.

IMPORTANCE These results provide valuable insights into the ecological influence of exogenous microbial exposure, as well as laying the foundation for improving aquarium management practices. By comparing data for dolphins from aquaria that use natural versus artificial seawater, we demonstrate the potential influence of aquarium water disinfection procedures on dolphin microbial dynamics.