Associations between animal welfare indicators and Campylobacter spp. in broiler chickens under commercial settings: A case study

Few studies have previously investigated how poor animal welfare might be associated with infection of zoonotic pathogens in humans. This paper assesses the predictive value of the presence of Campylobacter spp. in broiler chicken flocks when animal-based measures related to footpad dermatitis, hock burns, body lesions and arthritis are identified under commercial conditions (high density). The study population included 32 flocks analysed on farm and at slaughter, slaughtered between April and August 2008 in six different slaughter plants in Brittany, France. Welfare and health indicators are those indicated by the European legislation and sampling was carried out in the framework of the European baseline survey on the prevalence of Campylobacter in broiler chicken. Caecal contents, sampled both on farm and at slaughter, and carcass skin samples from the neck and breast at slaughter, were investigated for the presence of Campylobacter spp. Logistic models/classification trees were used to estimate the probability of the presence (or absence) of a specific foodborne pathogen in a flock based on specific animal-based measures (or combinations of measures) in order to study the potential relationship between welfare indicators and foodborne pathogen prevalence/incidence levels. On farm, flocks with more than 25% animals with severe lesions on between 25 and 50% of the footpad are predicted to be Campylobacter-positive whereas flocks where less than 13 individuals have arthritis are predicted to be Campylobacter-negative. The error rate on farm and at slaughter was 10 and 4% respectively indicating good predicting abilities. A poor welfare environment may result in stress, which reduces chicken immunocompetence making them more susceptible to Campylobacter spp. An infection with Campylobacter spp may lead to impaired defence and susceptibility to other pathogens which may result in greater intestinal excretion. Poor welfare and high growing rate lead to digestive troubles that lead to litter humidity. Litter humidity that, among other things, causes footpad dermatitis may also influence the horizontal transmission of the Campylobacter spp. infection due to the normal coprophagic behaviour of poultry. Reducing welfare problems by a better management of rearing conditions would not only improve broiler welfare, but it would also decrease the risks of Campylobacter contamination, of carcass condemnations and of economic loss for the poultry industry.

One Health Economics to confront disease threats

Global economic impacts of epidemics suggest high return on investment in prevention and One Health capacity. However, such investments remain limited, contributing to persistent endemic diseases and vulnerability to emerging ones. An interdisciplinary workshop explored methods for country-level analysis of added value of One Health approaches to disease control. Key recommendations include: 1. systems thinking to identify risks and mitigation options for decision-making under uncertainty; 2. multisectoral economic impact assessment to identify wider relevance and possible resource-sharing, and 3. consistent integration of environmental considerations. Economic analysis offers a congruent measure of value complementing diverse impact metrics among sectors and contexts.

Drivers for emerging issues in animal and plant health

The history of agriculture includes many animal and plant disease events that have had major consequences for the sector, as well as for humans. At the same time, human activities beyond agriculture have often driven the emergence of diseases. The more that humans expand the footprint of the global population, encroach into natural habitats, alter these habitats to extract resources and intensify food production, as well as move animals, people and commodities along with the pathogens they carry, the greater the potential for pathogens and pests to spread and for infection to emerge or re-emerge. While essential to human well-being, producing food also plays a major role in disease dynamics. The risk of emergence of pests and pathogens has increased as a consequence of global changes in the way food is produced, moved and consumed. Climate change is likely to increase pressure on the availability of food and provide newly suitable conditions for invasive pests and pathogens. Human population displacements due to economic, political and humanitarian crises represent another set of potential drivers for emerging issues. The overlapping drivers of plant, animal and human disease emergence and environmental changes point towards the concept of 'One Health'. This paradigm underlines the urgent need to understand the influence of human behaviour and incorporate this understanding into our approach to emerging risks. For this, we face two major challenges. One is cultural; the second is methodological. We have to look at systems not under the narrow view of specific hazards but with a wider approach to system dynamics, and consider a broad spectrum of potential outcomes in terms of risk. In addition, we have to make sense of the vast amounts of data that are available in the modern age. This paper aims to help in preparing for the cultural and methodological shifts needed in our approach to emerging risks.

Human-Dromedary Camel Interactions and the Risk of Acquiring Zoonotic Middle East Respiratory Syndrome Coronavirus Infection

Middle East respiratory syndrome coronavirus (MERS‐CoV) cases without documented contact with another human MERS‐CoV case make up 61% (517/853) of all reported cases. These primary cases are of particular interest for understanding the source(s) and route(s) of transmission and for designing long‐term disease control measures. Dromedary camels are the only animal species for which there is convincing evidence that it is a host species for MERS‐CoV and hence a potential source of human infections. However, only a small proportion of the primary cases have reported contact with camels. Other possible sources and vehicles of infection include food‐borne transmission through consumption of unpasteurized camel milk and raw meat, medicinal use of camel urine and zoonotic transmission from other species. There are critical knowledge gaps around this new disease which can only be closed through traditional field epidemiological investigations and studies designed to test hypothesis regarding sources of infection and risk factors for disease. Since the 1960s, there has been a radical change in dromedary camel farming practices in the Arabian Peninsula with an intensification of the production and a concentration of the production around cities. It is possible that the recent intensification of camel herding in the Arabian Peninsula has increased the virus' reproductive number and attack rate in camel herds while the ‘urbanization’ of camel herding increased the frequency of zoonotic ‘spillover’ infections from camels to humans. It is reasonable to assume, although difficult to measure, that the sensitivity of public health surveillance to detect previously unknown diseases is lower in East Africa than in Saudi Arabia and that sporadic human cases may have gone undetected there.

Integrating surveillance of animal health, food pathogens and foodborne disease in the European Union

The European Food Safety Authority (EFSA) is the keystone of European Union (EU) risk assessment for food and feed safety. In collaboration with national authorities and in consultation with its stakeholders, EFSA provides independent scientific advice and information about existing and emerging risks. Assessing biological risks at the human-animal interface is becoming ever more challenging because this interface is in a permanent state of flux. In addition, questions about food safety cannot usually be categorised under one discipline; most of the time, they need to be addressed in a transdisciplinary way. Two scientific panels of EFSA, on biological hazards (BIOHAZ) and on animal health and welfare (AHAW), have, in many instances, jointly addressed such complex, multifaceted questions of risk. This paper reviews the integrated approach of the EU towards risk assessment, with a special focus on human health and the whole food chain, and on science-based interventions to lower the risk to consumers.

Risk assessment in fish welfare, applications and limitations

The Treaty of Amsterdam, in force since 1 May 1999, has established new ground rules for the actions of the European Union (EU) on animal welfare. It recognizes that animals are sentient beings and obliges the European Institutions to pay full regard to the welfare requirements of animals when formulating and implementing Community legislation. In order to properly address welfare issues, these need to be assessed in a scientific and transparent way. The principles of risk assessment in terms of transparency and use of available scientific data are probably well suited for this area. The application of risk assessment for terrestrial and aquatic animal welfare is a relatively new area. This paper describes the work developed in the context of the European Food Safety Authority (EFSA) opinions on the application of a risk assessment methodology to fish welfare. Risk assessment is a scientifically based process that seeks to determine the likelihood and consequences of an adverse event, which is referred to as a hazard. It generally consists of the following steps: (i) hazard identification, (ii) hazard characterisation, (iii) exposure assessment and (iv) risk characterisation. Different approaches can be used for risk assessments, such as qualitative, semi-quantitative and quantitative approaches. These are discussed in the context of fish welfare, using examples from assessments done to aquaculture husbandry systems and stunning/killing methods for farmed fish. A critical review of the applications and limitations of the risk methodology in fish welfare is given. There is a need to develop appropriate indicators of fish welfare. Yet, risk assessment methodology provides a transparent approach to identify significant hazards and support recommendations for improved welfare.

Viral gametocytic hypertrophy of Crassostrea gigas in France: from occasional records to disease emergence?

Viral gametocytic hypertrophy was reported for the first time in 2001 in Pacific oyster Crassostrea gigas in France. Since this date, the number of reported cases and the distribution area have increased every year; however, the cases are not associated with macroscopic signs or increased mortality rates. Both male and female gametes were hypertrophied and basophilic inclusions were observed in gamete nuclei. Transmission electron microscopy revealed the presence of viral particles in these intranuclear basophilic inclusions. These particles had characteristics similar to those of the Papillomaviridae and Polyoma viridae families: they were small, non-enveloped, icosahedral, and 44 to 56 nm in diameter. The viral particles were found in male, female and hermaphrodite oysters and no significant difference in viral infection was observed between those groups. The frequency of detection and the intensity of infection were low and no host defence reaction was recognised, suggesting that the viral particles had a weak impact on C. gigas. The viral particles described in the present study seem to be similar to these described in C. virginica in the USA and Canada and in C. gigas in Korea, but further studies are required to confirm their identity. The issue of a possible emergence of this infection is discussed.

Phylogenetic study and identification of Vibrio splendidus-related strains based on gyrB gene sequences

Different strains related to Vibrio splendidus have been associated with infection of aquatic animals. An epidemiological study of V. splendidus strains associated with Crassostrea gigas mortalities demonstrated genetic diversity within this group and suggested its polyphyletic nature. Recently 4 species, V. lentus, V. chagasii, V. pomeroyi and V. kanaloae, phenotypically related to V. splendidus, have been described, although biochemical methods do not clearly discriminate species within this group. Here, we propose a polyphasic approach to investigate their taxonomic relationships. Phylogenetic analysis of V. splendidus-related strains was carried out using the nucleotide sequences of 16S ribosomal DNA (16S rDNA) and gyrase B subunit (gyrB) genes. Species delineation based on 16S rDNA-sequencing is limited because of divergence between cistrons, roughly equivalent to divergence between strains. Despite a high level of sequence similarity, strains were separated into 2 clades. In the phylogenetic tree constructed on the basis of gyrB gene sequences, strains were separated into 5 independent clusters containing V. splendidus, V. lentus, V. chagasii-type strains and a putative new genomic species. This phylogenetic grouping was almost congruent with that based on DNA-DNA hybridisation analysis. V. pomeroyi, V. kanaloae and V. tasmaniensis-type strains clustered together in a fifth clade. The gyrB gene-sequencing approach is discussed as an alternative for investigating the taxonomy of Vibrio species.

Specificity of PCR and in situ hybridization assays designed for detection of Marteilia sydneyi and M. refringens

Primers and DNA probes designed for use in the specific detection of the paramyxean parasites Marteilia sydneyi and Marteilia refringens were tested for their potential to cross-react with closely related species in Polymerase Chain Reaction (PCR) and in situ hybridization. PCR primers and a DNA probe designed within the ITS1 rRNA of M. sydneyi were specific for M. sydneyi when compared with related species of Marteilia and Marteilioides. PCR primers designed within the 18S rRNA of M. refringens were specific in the detection of this species in PCR while a DNA probe (named Smart 2) designed on the same gene cross-reacted with M. sydneyi in tissue sections of Saccostrea glomerata as well as Marteilioides sp. infecting Striostrea mytiloides. Though not species specific, the Smart 2 probe provided a stronger signal in detection of all stages of M. sydneyi than the ITSI probe. The ITS probe is proposed for use as a confirmatory diagnostic tool for M. sydneyi.

[Characterization of pathogenic bacteria of the cupped oyster Crassostrea gigas]

The French mollusc production is mainly based on the Pacific cupped oyster, Crassostrea gigas. Since 1991, outbreaks of mass mortality of juveniles are reported during the summer period. These outbreaks are a major concern of oyster industry. Several studies have established given bacterial strains to be pathogenic for bivalve species, including oysters. Here we present a study of mortality outbreaks of C. gigas, as initiated in 1995. In a first step, bacterial strains were isolated during mass mortality outbreak and were biochemically characterised. Among the isolated strains, some strains of Vibrio splendidus biovar II were found to be pathogenic by means of experimental challenge of oyster juveniles. In the second step, a genotypical identification of the pathogenic strain was undertaken, based on 16S RNA sequences and phylogenetic analysis. It confirmed that the pathogenetic strain belonged to Vibrio splendidus biovar II.

Needle in a haystack: involvement of the copepod PARACARTIA grani in the life-cycle of the oyster pathogen Marteilia refringens

Marteilia refringens is a major pathogen of the European flat oyster, Ostrea edulis Linnaeus. Since its description, the life-cycle of this protozoan parasite has eluded discovery. Attempts to infect oysters experimentally have been unsuccessful and led to the hypothesis of a complex life-cycle involving several hosts. Knowledge of this life-cycle is of central importance in order to manage oyster disease. However, the exploration of M. refringens life-cycle has been previously limited by the detection tools available and the tremendous number of species to be screened in enzootic areas. In this study, these two restrictions were circumvented by the use of both molecular detection tools and a mesocosm with low biodiversity. Screening of the entire fauna of the pond for M. refringens DNA was systematically undertaken using PCR. Here, we show that the copepod Paracartia (Acartia) grani is a host of M. refringens. Not only was DNA of M. refringens consistently detected in P. grani but also the presence of the parasite in the ovarian tissues was demonstrated using in situ hybridization. Finally, successful experimental transmissions provided evidence that P. grani can be infected from infected flat oysters.

Traceability of aquatic animals

Effective methods of traceability are urgently required for use in research as well as in different types of aquaculture operations and to control trade in aquatic animals and products. In regard to the marking of fish, many different tagging methods have been described and the method to be used depends on the purpose and need for tagging. In contrast, for molluscs and crustaceans, only a few methods of marking such animals have been described, due to the practical difficulties. The authors first describe the different methods for tracing fish and fishery products, by means of external tags, such as Floy tags, Carlin tags and passive integrated transponder tags; chemical marking using inorganic substances such as silver nitrate or potassium nitrate, pigments, oxytetracycline, etc.; and several different types of electronic devices in which basic information such as the strain of fish, farm of origin or weight can be stored. Genetic traceability using deoxyribonucleic acid profiling is developing quite rapidly for cultured brood stocks and wild populations. This technique may be used with very high degrees of confidence to assign to or exclude animals or products from their claimed origin, paternity or strain, and may be used as evidence in court proceedings. The second section of this paper describes the traceability of live molluscs for restocking and for human consumption. In these applications, genetic markers have been demonstrated to be suitable. Mechanical tagging on a small scale for research purposes has also been used. Otherwise, the only means of tracing live molluscs are the movement documents and the labelling on boxes that certifies the origin of the commodity. The third section describes the methods available for tracing live and dead crustaceans. A large variety of physical tagging methods for decapod crustaceans is described, such as the injection of biological stains (fast green, Niagara sky blue, trypan red and blue) and external tags such as coloured streamer tags, wire tags and a variety of anchor tags. Furthermore, a number of different internal coding methods, such as the coded micro-wire tags and injected elastomer tags are discussed in detail. As is the case for fish, genetic molecular techniques are also applied in population studies of crustaceans; some of the molecular genetic methods are described. Prawns for human consumption are most frequently packed whole or as tails after the necessary sorting, washing and freezing and the only way of performing a traceback is through documents relating to movement, invoices, health certificates and labelling of the boxes. The minimum requirements for labelling would be the content of the packages, i.e. species, quantity, identification of the manufacturer (name and address), packing place, importer/exporter or vendor of the product, in addition to the loading bill number.

Molecular evidence for the existence of two species of Marteilia in Europe

Marteilia refringens is one of the most significant pathogens of bivalve molluscs. Previous sequencing of the small subunit ribosomal RNA gene of M. refringens isolates derived from the infected mussels (Mytilus edulis and Mytilus galloprovinciallis) and the oyster (Ostrea edulis) in Europe did not reveal genetic polymorphisms despite indications from epizootiological data that distinct types may exist. We investigated the existence of polymorphisms in the internal transcribed spacer region of the ribosomal RNA genes. The sequences of this region proved to be clearly dimorphic among Marteilia from five sampling sites. The distribution of the two genetic types, named "O" and "M", appeared to be linked to the host species, oysters and mussels, respectively. We therefore support the recognition of two species of Marteilia in Europe and propose that the "O" type corresponds to M. refringens and the "M" type to M. maurini.

Cg-TIMP, an inducible tissue inhibitor of metalloproteinase from the Pacific oyster Crassostrea gigas with a potential role in wound healing and defense mechanisms(1)

We have cloned and characterized a cDNA encoding Cg-TIMP, the first tissue inhibitor of metalloproteinase identified in mollusks. The isolated cDNA encodes a protein of 221 residues that has a domain organization similar to that of vertebrate TIMPs including a signal sequence, and the 12 cysteines characteristic of the TIMP signature. Analysis of Cg-TIMP expression in adult oyster tissues, by Northern blot and in situ hybridization, indicates that Cg-TIMP was only expressed in hemocytes which are the key components of defense mechanisms in mollusks. We also observed that Cg-TIMP mRNA accumulated during shell damage and bacterial challenge. This pattern of expression suggests that Cg-TIMP may be an important factor in wound healing and defense mechanisms.

Haplosporidiosis in the Pacific oyster Crassostrea gigas from the French Atlantic coast

Two cases of haplosporidian infection occurred during 1993 in Pacific oysters Crassostrea gigas from the French Atlantic coast. The localization and ultrastructure of the plasmodia are described. In situ hybridization of infected tissue sections was conducted with DNA probes for oyster-infecting haplosporidians. The Haplosporidium nelsoni-specific DNA probe MSX1347 hybridized with the C. gigas parasite, and the H. costale-specific probe SSO1318 did not hybridize. Total genomic DNA was extracted from the infected tissue sections for polymerase chain reaction (PCR) amplification of the haplosporidian. PCR amplifications with H. nelsoni-specific primers and with 'universal' actin primers did not yield the expected products of 573 and 700 bp, respectively. A series of primers was designed to amplify short regions of small subunit ribosomal DNA (SSU rDNA) from most haplosporidians. The primers encompass a highly variable region of the SSU rDNA and did not amplify oyster DNA. PCR amplification of the infected C. gigas genomic DNA with these primers yielded the expected-sized product from the primer pair targeting the shortest region (94 bp). This PCR product was sequenced and it was identical to the corresponding SSU rDNA region of H. nelsoni.

Detection of Bonamia ostreae based on small subunit ribosomal probe

Bonamia ostreae is a protozoan parasite of the flat oyster, Ostrea edulis, which has caused significant loss of oysters in Europe over the last decade. B. ostreae was purified from infected flat oysters and DNA was extracted. The nearly complete small subunit rDNA gene of B. ostreae was amplified using universal oligonucleotides and the PCR product was cloned and sequenced. BLAST research with this sequence revealed similarities to Haplosporidium nelsoni, Haplosporidium costale, and Minchinia teredinis. These data suggest that B. ostreae may be included in the genus Haplosporidium. Specific B. ostreae primers were designed for labeling, by PCR, a probe. This probe was successfully used by in situ hybridization to detect B. ostreae in infected fiat oysters, thus confirming the accuracy of this SSU rDNA sequence. The probe lead also to the detection of Bonamia sp. in infected Tiostrea chilensis and H. nelsoni in infected Crassostrea virginica but not Mikrocytos mackini infected Crassostrea gigas. These primers were also used to detect B. ostreae from infected oyster tissues by PCR. This B. ostreae SSU rDNA gene sequence provides genetic information as a first step toward elucidation of the taxonomic boundaries among the microcell organisms. Moreover, the development of DNA detection assays will be valuable specific diagnostic tools.

DNA Probes As Potential Tools for the Detection of Marteilia refringens

Since its first description, the paramyxean parasite Marteilia refringens has been recognized as a significant pathogen of bivalve mollusks. The existence of a complex life cycle was postulated by many authors. Here we report the development of DNA-based detection assays as powerful tools to elucidate the Marteilia refringens life cycle. After alignment of the Marteilia refringens ribosomal DNA small subunit sequence with those of various eukaryotic organisms, polymerase chain reaction primers were designed. Specific primers were used to amplify DNA extracted from purified Marteilia refringens and infected hosts. The specificity of amplified fragments was confirmed by Southern blotting with an oligoprobe. For in situ hybridization, four probes were tested for specific detection of 18S rRNA isolated from Marteilia refringens and other eukaryotic cells by Northern blotting. The most specific probe, Smart 2, was successfully used to detect Marteilia refringens by in situ hybridization in infected oysters and mussels.

Arbitrarily primed PCR to type Vibrio spp. pathogenic for shrimp

A molecular typing study on Vibrio strains implicated in shrimp disease outbreaks in New Caledonia and Japan was conducted by using AP-PCR (arbitrarily primed PCR). It allowed rapid identification of isolates at the genospecies level and studies of infraspecific population structures of epidemiological interest. Clusters identified within the species Vibrio penaeicida were related to their area of origin, allowing discrimination between Japanese and New Caledonian isolates, as well as between those from two different bays in New Caledonia separated by only 50 km. Other subclusters of New Caledonian V. penaeicida isolates could be identified, but it was not possible to link those differences to accurate epidemiological features. This contribution of AP-PCR to the study of vibriosis in penaeid shrimps demonstrates its high discriminating power and the relevance of the epidemiological information provided. This approach would contribute to better knowledge of the ecology of Vibrio spp. and their implication in shrimp disease in aquaculture.