Showing papers by "An Martel published in 2012"

Poultry as a host for the zoonotic pathogen Campylobacter jejuni.

Abstract: Campylobacteriosis is the most reported foodborne gastroenteritic disease and poses a serious health burden in industrialized countries. Disease in humans is mainly caused by the zoonotic pathogen Campylobacter jejuni. Due to its wide-spread occurrence in the environment, the epidemiology of Campylobacter remains poorly understood. It is generally accepted, however, that chickens are a natural host for Campylobacter jejuni, and for Campylobacter spp. in general, and that colonized broiler chicks are the primary vector for transmitting this pathogen to humans. Several potential sources and vectors for transmitting C. jejuni to broiler flocks have been identified. Initially, one or a few broilers can become colonized at an age of >2 weeks until the end of rearing, after which the infection will rapidly spread throughout the entire flock. Such a flock is generally colonized until slaughter and infected birds carry a very high C. jejuni load in their gastrointestinal tract, especially the ceca. This eventually results in contaminated carcasses during processing, which can transmit this pathogen to humans. Recent genetic typing studies showed that chicken isolates can frequently be linked to human clinical cases of Campylobacter enteritis. However, despite the increasing evidence that the chicken reservoir is the number one risk factor for disease in humans, no effective strategy exists to reduce Campylobachter prevalence in poultry flocks, which can in part be explained by the incomplete understanding of the epidemiology of C. jejuni in broiler flocks. As a result, the number of human campylobacteriosis cases associated with the chicken vector remains strikingly high.

Waterfowl: potential environmental reservoirs of the chytrid fungus Batrachochytrium dendrobatidis.

Abstract: Infections with Batrachochytrium dendrobatidis (B. dendrobatidis), the causal agent of chytridiomycosis, have been shown to play an important role in the decline of amphibians worldwide. Spread of the fungus is poorly understood. Bird movement might possibly contribute to the spread of B. dendrobatidis in the environment. Therefore, 397 wild geese in Belgium were screened for presence of B. dendrobatidis on their toes using real-time quantitative PCR (qPCR). In addition, chemotaxis towards, adhesion, survival after desiccation and proliferation of B. dendrobatidis on keratinous toe scales from waterfowl were examined in vitro. qPCR revealed that 76 geese (15%) were positive for B. dendrobatidis. Results of the in vitro tests showed that B. dendrobatidis is attracted to the keratinous toes of aquatic birds on which they can adhere and even proliferate. However, desiccation is poorly tolerated. This suggests waterfowl are potential environmental reservoirs for B. dendrobatidis.

A tolerogenic mucosal immune response leads to persistent Campylobacter jejuni colonization in the chicken gut

Abstract: Campylobacter enteritis is the most reported zoonotic disease in many developed countries where it imposes a serious health burden. Campylobacter transmission to humans occurs primarily through the chicken vector. Chicks are regarded as a natural host for Campylobacter species and are colonized with C. jejuni in particular. But despite carrying a very high bacterial load in their gastrointestinal tract, these birds, in contrast to humans, do not develop pathological signs. It seems that in chickens C. jejuni principally harbors in the cecal mucosal crypts, where an inefficient inflammatory response fails to clear the bacterium from the gut. Recent intensive research resulted in an increased insight into the cross talk between C. jejuni and its avian host. This review discusses the chicken intestinal mucosal immune response upon C. jejuni entrance, leading to tolerance and persistent cecal colonization. It might in addition provide a solid base for further research regarding this topic aiming to fully understand the host-bacterium dynamics of C. jejuni in chicks and to develop effective control measures to clear this zoonotic pathogen from poultry lines.

Germ tube mediated invasion of Batrachochytrium dendrobatidis in amphibian skin is host dependent.

Abstract: Batrachochytrium dendrobatidis (Bd) is the causative agent of chytridiomycosis, a fungal skin disease in amphibians and driver of worldwide amphibian declines. We focussed on the early stages of infection by Bd in 3 amphibian species with a differential susceptibility to chytridiomycosis. Skin explants of Alytes muletensis, Litoria caerulea and Xenopus leavis were exposed to Bd in an Ussing chamber for 3 to 5 days. Early interactions of Bd with amphibian skin were observed using light microscopy and transmission electron microscopy. To validate the observations in vitro, comparison was made with skin from experimentally infected frogs. Additional in vitro experiments were performed to elucidate the process of intracellular colonization in L. caerulea. Early interactions of Bd with amphibian skin are: attachment of zoospores to host skin, zoospore germination, germ tube development, penetration into skin cells, invasive growth in the host skin, resulting in the loss of host cell cytoplasm. Inoculation of A. muletensis and L. caerulea skin was followed within 24 h by endobiotic development, with sporangia located intracellularly in the skin. Evidence is provided of how intracellular colonization is established and how colonization by Bd proceeds to deeper skin layers. Older thalli develop rhizoid-like structures that spread to deeper skin layers, form a swelling inside the host cell to finally give rise to a new thallus. In X. laevis, interaction of Bd with skin was limited to an epibiotic state, with sporangia developing upon the skin. Only the superficial epidermis was affected. Epidermal cells seemed to be used as a nutrient source without development of intracellular thalli. The in vitro data agreed with the results obtained after experimental infection of the studied frog species. These data suggest that the colonization strategy of B. dendrobatidis is host dependent, with the extent of colonization most likely determined by inherent characteristics of the host epidermis.

Germination of Aspergillus fumigatus inside avian respiratory macrophages is associated with cytotoxicity.

Abstract: Although aspergillosis is one of the most common diseases in captive birds, the pathogenesis of avian aspergillosis is poorly known. We studied the role of avian respiratory macrophages as a first line of defense against avian aspergillosis. The phagocytic and killing capacities of avian respiratory macrophages were evaluated using pigeon respiratory macrophages that were inoculated with Aspergillus fumigatus conidia. On average, 25% of macrophage-associated conidia were phagocytosed after one hour. Sixteen percents of these cell-associated conidia were killed after 4 h and conidial germination was inhibited in more than 95% of the conidia. A. fumigatus conidia were shown to be cytotoxic to the macrophages. Intracellularly germinating conidia were located free in the cytoplasm of necrotic cells, as shown using transmission electron microscopy. These results suggest that avian respiratory macrophages may prevent early establishment of infection, unless the number of A. fumigatus conidia exceeds the macrophage killing capacity, leading to intracellular germination and colonization of the respiratory tract.

Dermatological diseases in lizards

Abstract: Lizards with dermatological disease are routinely encountered in veterinary practice and it is often challenging to establish a thorough and adequate case management for these otherwise highly visible conditions. Most skin diseases in lizards are primarily a consequence of environmental stressors such as substandard husbandry and underlying disease, facilitating the onset of mainly secondary bacterial and mycotic dermal infections. This review provides an overview of common dermatological problems in lizards and aetiology, treatment and prevention are discussed for both infectious and non-infectious conditions. Although investigational approaches may be directed by the primary clinical manifestation of dermatological problems, the importance of a multidirectional approach cannot be over-emphasized. Proper treatment can only be initiated when the correct diagnosis has been made and husbandry issues dealt with. Current information on susceptibility patterns and on the use of appropriate chemotherapeutics in lizards is limited for the treatment of infectious causes of dermatitis.

Novel Chlamydiaceae disease in captive salamanders.

Abstract: To the Editor: Although 2 major diseases of amphibians, chytridiomycosis and ranavirosis, have been relatively well studied, enigmatic amphibian disease and death not attributable to any of the known amphibian diseases frequently occur (1). We describe an apparently new disease in salamanders that is associated with a novel genus within the family Chlamydiaceae. The salamanders seen in our clinic belonged to 1 of the following species: Salamandra corsica, the Corsican fire salamander (5 animals from 1 collection); Neurergus crocatus, the yellow spotted newt (11 animals from 3 collections); or N. strauchii, Strauch’s spotted newt (6 animals from 2 collections). All salamanders were captive bred; housed in breeding colonies in private collections in Elsloo and Eindhoven, the Netherlands, Munich, Germany, and Brugge, Belgium; and 1–3 years of age. Disease was characterized by anorexia, lethargy, edema, and markedly abnormal gait. Mortality rate was 100%. Animals in these collections had no histories of disease. All animals were in good nutritional condition. Necropsy did not yield any macroscopic lesions. All animals had mild intestinal nematode or protozoan infections. Results of real-time PCRs for iridoviruses in liver and skin (2) or Batrachochytrium dendrobatidis fungus of skin (3) were negative for all animals. We placed liver suspensions from the dead salamanders on Columbia agar with 5% sheep blood and tryptic soy agar and then incubated the samples up to 14 days at 20°C. No consistent bacterial growth was observed. Histologic examination of 2 Corsican fire salamanders and 1 yellow spotted newt revealed hepatitis in 1 of the Corsican fire salamanders and the yellow spotted newt. Hepatitis was characterized by high numbers of melanomacrophages and a marked infiltration of granulocytic leukocytes. Immunohistochemical staining for chlamydia (IMAGEN Chlamydia; Oxoid, Basingstone, UK) showed cell-associated fluorescently stained aggregates in liver tissue, suggestive of Chlamydiales bacteria. Transmission electron microscopic examination of the liver of a yellow spotted newt revealed intracellular inclusions containing particles matching the morphology of reticulate or elementary bodies of Chlamydiaceae (Technical Appendix). A PCR (4) to detect the 16S rRNA of all Chlamydiales bacteria, performed on liver tissue samples from all animals, yielded positive results in all 5 Corsican fire salamanders; in 4/7, 1/3, and 1/1 yellow spotted newts; and in 4/5 and 1/1 Strauch’s spotted newts. For taxon identification, the 16S rRNA gene of the Chlamydiales bacteria was amplified and sequenced from the livers from 2 yellow spotted newts (1 from the collection in Elsloo, the Netherlands and 1 from the collection in Munich, Germany), 1 Strauch’s spotted newt, and 5 Corsican fire salamanders. The sequences shared >90% nt identity with the 16S rRNA gene of C. abortus B577 (GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"D85709","term_id":"2114161","term_text":"D85709"}}D85709) and therefore can be identified as a member of the family Chlamydiaceae (5). The closest 16S rRNA similarity (92%) was observed with C. psittaci strain CPX0308 ({"type":"entrez-nucleotide","attrs":{"text":"AB285329","term_id":"148537245","term_text":"AB285329"}}AB285329). The sequence obtained from all spotted newt species specimens was identical (GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"JN392920","term_id":"358009359","term_text":"JN392920"}}JN392920) but differed slightly (1%) from that obtained from the fire salamander species specimens (GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"JN392919","term_id":"358009358","term_text":"JN392919"}}JN392919). These sequence differences point to the existence of multiple strains with possible host adaptation. We determined the phylogenetic position of the novel taxon, named Candidatus Amphibiichlamydia salamandrae (Technical Appendix), identified by using neighbor-joining analysis with Kodon software (Applied Maths, Sint-Martens-Latem, Belgium). The novel Chlamydiales forms a distinct branch in the well-supported monophyletic clade with the genera Chlamydia and Candidatus Clavochlamydia salmonicola (family Chlamydiaceae) (Figure). Maximum parsimony and unweighted pair group with arithmetic mean analyses yielded cladograms with the same topology (results not shown). Previous reports of members of the family Chlamydiaceae in amphibians concerned species occurring in other vertebrate taxa as well: C. psittaci, C. pneumoniae, C. abortus, and C. suis (6–10). To our knowledge, this member of the family Chlamydiaceae has been seen in amphibians, but not in other vertebrate hosts. The 16S rRNA analysis showed this taxon to belong to a clade with Candidatus Clavochlamydia salmonicola, a taxon found in fish. The phylogenetic position of the novel taxon in the family Chlamydiaceae thus roughly reflects the phylogenetic relation between the host species, providing evidence for host–bacterium co-evolution in the family Chlamydiaceae. Figure Topology of the novel amphibian Chlamydiaceae (Candidatus Amphibiichlamydia salamandrae) within the phylogenetic tree obtained by neighbor-joining and based on 16S rRNA gene data from representative species. Numbers show the percentage of times each branch ... Although the results obtained are not conclusive with regard to the pathogenic potential of this novel genus and species of Chlamydiales, we were not able to attribute the clinical signs to any known disease. We therefore suggest that we discovered a novel bacterial taxon with possible considerable impact on amphibian health.

Antibacterial therapeutics for the treatment of chytrid infection in amphibians: Columbus's egg?

Abstract: The establishment of safe and effective protocols to treat chytridiomycosis in amphibians is urgently required. In this study, the usefulness of antibacterial agents to clear chytridiomycosis from infected amphibians was evaluated. Florfenicol, sulfamethoxazole, sulfadiazine and the combination of trimethoprim and sulfonamides were active in vitro against cultures of five Batrachochytrium dendrobatidis strains containing sporangia and zoospores, with minimum inhibitory concentrations (MIC) of 0.5-1.0 μg/ml for florfenicol and 8.0 μg/ml for the sulfonamides. Trimethoprim was not capable of inhibiting growth but, combined with sulfonamides, reduced the time to visible growth inhibition by the sulfonamides. Growth inhibition of B. dendrobatidis was not observed after exposure to clindamycin, doxycycline, enrofloxacin, paromomycin, polymyxin E and tylosin. Cultures of sporangia and zoospores of B. dendrobatidis strains JEL423 and IA042 were killed completely after 14 days of exposure to 100 μg/ml florfenicol or 16 μg/ml trimethoprim combined with 80 μg/ml sulfadiazine. These concentrations were, however, not capable of efficiently killing zoospores within 4 days after exposure as assessed using flow cytometry. Florfenicol concentrations remained stable in a bathing solution during a ten day period. Exposure of Discoglossus scovazzi tadpoles for ten days to 100 μg/ml but not to 10 μg florfenicol /ml water resulted in toxicity. In an in vivo trial, post metamorphic Alytes muletensis, experimentally inoculated with B. dendrobatidis, were treated topically with a solution containing 10 μg/ml of florfenicol during 14 days. Although a significant reduction of the B. dendrobatidis load was obtained, none of the treated animals cleared the infection. We thus conclude that, despite marked anti B. dendrobatidis activity in vitro, the florfenicol treatment used is not capable of eliminating B. dendrobatidis infections from amphibians.

Susceptibility of adult pigeons and hybrid falcons to experimental aspergillosis

Abstract: Aspergillosis caused by Aspergillus fumigatus seems to be more prevalent in some avian species than in others. We compared the development of aspergillosis in 8-month-old Gyr-Saker hybrid falcons and 8-month-old pigeons after a single intratracheal inoculation of different dosages of A. fumigatus conidia (10(7), 10(5) and 10(3)). Clinical signs, including vomiting, discoloration of the urates, loss of appetite and dyspnoea, were observed in four out of five falcons and in four out of five pigeons inoculated with 10(7) A. fumigatus conidia. Necropsy revealed the presence of granulomas in the air sacs and/or lungs in four out of five falcons and in four out of five pigeons in the high dosage group. A. fumigatus was isolated from these granulomas in three falcons and in three pigeons. The presence of fungal hyphae was detected with Periodic acid Shiff reagent staining in three out of five falcons and in three out of five pigeons in the high dosage group. Avian respiratory macrophages were clearly present in and around the fungal granulomas. In the other dosage groups, no granulomas, positive A. fumigatus cultures or fungal hyphae were present, except for one falcon in the middle dosage group in which a sterile granuloma without fungal hyphae was noticed. In conclusion, the study shows that adult falcons and pigeons are susceptible to aspergillosis after inoculation of a single dose of conidia intratracheally.

Road-killed Common Toads (Bufo bufo) in Flanders (Belgium) Reveal Low Prevalence of Ranaviruses and Batrachochytrium dendrobatidis

Abstract: Road-killed common toads (Bufo bufo; n=1,740) from Flanders, Belgium, were tested for ranavirus and Batrachochytrium dendrobatidis (Bd) using polymerase chain reaction. Both infections were present at a very low prevalence (<0.2% with a confidence interval of 95% for ranavirus and 0.63% for Bd).

High Brachyspira colonization rates of Belgian layer flocks and boiler hen carcasses

Abstract: Brachyspira intermedia, B. alvinipulli and B. pilosicoli have been associated with diarrhea, fecal eggshell-staining and reduced egg production in laying hens. B. pilosicoli has also been associated with enteric disease in humans. We screened Belgian layer flocks for the presence of Brachyspira spp. and studied contamination of boiler hen carcasses with these bacteria as a possible source of human infections.

Deoxynivalenol predisposes for the development of necrotic enteritis in broilers

Abstract: 1) Dept. of Pathology, Bacteriology and Poultry Diseases 2) Dept. of Pharmacology, Toxicology and Biochemistry 3) Dept. of Reproduction, Obstetrics and Herd Health, Faculty of Veterinary Medicine 4) Dept. of Food Science and Technology, Faculty of Biosciences and Landscape Architecture 5) Dept. of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University 6) Institute for Agricultural and Fisheries Research (ILVO) Animal Sciences Unit, Belgium E-mail: Gunther.Antonissen@UGent.be