Tom Hellebuyck

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

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.

Voriconazole, a safe alternative for treating infections caused by the Chrysosporium anamorph of Nannizziopsis vriesii in bearded dragons (Pogona vitticeps)

Dermal and systemic infections caused by the Chrysosporium anamorph of Nannizziopsis vriesii (CANV) are highly prevalent in reptiles and may result in severe disease and high mortality. Due to the high incidence of therapeutic failures, optimizing treatment is required. We first determined in this study the minimal inhibitory concentrations (MIC) of itraconazole, voriconazole, amphotericin B and terbinafine against 32 CANV isolates. For voriconazole, amphotericin B and terbinafine a monomodal MIC distribution was seen, whereas a bimodal MIC distribution was present for itraconazole, indicating acquired resistance in one isolate. Fourteen naturally-infected bearded dragons (Pogona vitticeps), from the same owner, were treated orally with either itraconazole (5 mg/kg q24h) or voriconazole (10 mg/kg q24h). The clinical condition, drug plasma concentrations and the presence of CANV in skin samples were followed. The animals were treated until complete clearance of the fungus. The plasma concentrations of voriconazole and itraconazole exceeded the minimal inhibitory concentrations of the CANV isolates. Elimination of CANV was achieved on average after 27 and 47 days of treatment with itraconazole and voriconazole, respectively. Whereas only 2 out of 7 survived after itraconazole treatment, only a single animal died in the voriconazole treated group. In conclusion, based on a limited number of animals, voriconazole applied at a regimen of 10 mg/kg bodyweight (BW) q24h seems to be a safe and effective antimycotic drug to eliminate CANV infections in bearded dragons.

Cutaneous hyalohyphomycosis in a girdled lizard (Cordylus giganteus) caused by the Chrysosporium anamorph of Nannizziopsis vriesii and successful treatment with voriconazole

The Chrysosporium anamorph of Nannizziopsis vriesii was associated with dermatomycosis and high mortality in a group of captive giant girdled lizards (Cordylus giganteus). Treatment of one of the infected girdled lizards with voriconazole, which was selected on the basis of in vitro sensitivity testing of the isolate, resulted in resolution of lesions and negative fungal cultures from the skin. Three hours after oral administration of 10 mg/kg, the plasma level of voriconazole exceeded the 0.25-μg/mL minimal inhibitory concentration tenfold. In conclusion, administration of voriconazole at 10 mg/kg of body weight once daily for 10 weeks resulted in clinical cure and was well tolerated. A longer follow-up time and larger studies will be necessary to determine the long-term efficacy and safety of this treatment in giant girdled lizards.

Devriesea agamarum gen. nov., sp. nov., a novel actinobacterium associated with dermatitis and septicaemia in agamid lizards.

Five bacterial isolates were recovered from dermatitis or organ lesions of five agamid lizards. Three strains were recovered from Uromastyx species with dermatitis or septicaemia. All five isolates were Gram-positive small rods that could not be identified using conventional phenotypic systems. They grew on sheep blood agar as small haemolytic colonies after 24 h of incubation at temperatures between 25 and 42 degrees C under aerobic, microaerophilic or anaerobic conditions. They were catalase-positive and non-motile. Comparative analysis of 16S rRNA gene sequences revealed that the strains represent a new taxon within the class Actinobacteria. Their nearest phylogenetic neighbours were determined as Brachybacterium faecium LMG 19847(T) (95.9% 16S rRNA gene sequence similarity) and Dermabacter hominis NCIMB 13131(T) (95.3% similarity). The DNA G+C content of one of the novel isolates, strain IMP2(T), was 61 mol%. On the basis of morphological, chemotaxonomic and phylogenetic differences from other species of coryneform bacteria, it is proposed that this novel taxon be classified as Devriesea agamarum gen. nov., sp. nov. The type strain is IMP2(T) (=LMG 24257(T)=CCUG 55056(T)).

Devriesea agamarum causes dermatitis in bearded dragons (Pogona vitticeps).

Devriesea agamarum is frequently isolated from dermatitis in lizards, notably from cheilitis in spiny tailed lizards (genus Uromastyx). It was the aim of the present study to assess the role of this bacterium as a causative agent of dermatitis by fulfilling Kochs postulates. First, its association with diseased lizards was demonstrated. The bacterium was isolated from several, mainly desert dwelling squamate species showing symptoms of dermatitis and/or septicaemia. The affected lizards mainly belonged to the family of the Agamidae (genera Pogona, Uromastyx, Agama) and in one case to the Iguanidae (genus Crotaphytus). Secondly, the occurrence of D. agamarum in 66 clinically healthy bearded dragons, 21 clinically healthy Uromastyx species and 40 squamate eggshells was studied. The bacterium was isolated from the oral cavity of 10 bearded dragons but from none of the healthy Uromastyx species. Hence D. agamarum was found to be part of the oral microbiota in Pogona vitticeps. Finally, bearded dragons (P. vitticeps) were experimentally inoculated with D. agamarum by direct application of a bacterial suspension on intact and abraded skin. At the scarified skin of all inoculated lizards, dermatitis was induced from which D. agamarum was re-isolated. In conclusion, D. agamarum is a facultative pathogenic bacterium, able to cause dermatitis in agamid lizards when the integrity of the skin is breached.

Designing a successful antimicrobial treatment against Devriesea agamarum infections in lizards

Dermatitis caused by Devriesea agamarum poses a major health problem for the captive maintenance of several desert lizard species. This study was conducted to determine the optimal antimicrobial treatment to eliminate D. agamarum infections from lizards. First, the in vitro susceptibility of 42 D. agamarum isolates was determined for 10 different antimicrobial agents using an agar dilution method. In none of the isolates acquired antimicrobial resistance was demonstrated. Then, two intramuscular treatment protocols using either enrofloxacin or ceftiofur were tested in bearded dragons (Pogona vitticeps) experimentally infected with a D. agamarum strain showing a MIC of 2 microg/ml for enrofloxacin and 0.12 microg/ml for ceftiofur. While D. agamarum could no longer be isolated after 17-18 days of ceftiofur administration, enrofloxacin administration and sham treatment failed in clearing the infection after 27 days of treatment. Based on these results, intramuscular injection of ceftiofur at 5 mg/kg BW q24h was used to treat naturally and clinically infected Uromastyx lizards. This resulted in marked clinical improvement and clearance of infection after 12 days on average. In conclusion, intramuscular administration of ceftiofur at 5 mg/kg BW q24h eliminates D. agamarum in lizards, resulting in clinical cure.

Bearded dragons (Pogona vitticeps) asymptomatically infected with Devriesea agamarum are a source of persistent clinical infection in captive colonies of dab lizards (Uromastyx sp.).

Devriesea agamarum causes dermatitis and septicaemia in a variety of lizards, notably those belonging to the genus Uromastyx, whereas other species such as bearded dragons (Pogona vitticeps) seem to be asymptomatic carriers. Using amplified fragment length polymorphism (AFLP), the relatedness between 69 D. agamarum isolates was examined. The isolates derived from 44 diseased lizards, of which 31 belonged to the genus Uromastyx, and from 25 healthy lizards, of which 21 were bearded dragons. Eight AFLP genotypes were obtained, four of which comprised 93% of the isolates. These four genotypes were each present in 2, 2, 8 and 13 different captive colonies. Up to three genotypes were isolated from a single infected colony simultaneously. On two occasions, the same genotype was found in healthy bearded dragons and diseased Uromastyx lizards from the same colony, confirming the role of the former as an asymptomatic source of infection for the latter. Two genotypes, comprising 12 isolates, were exclusively associated with diseased Uromastyx lizards, suggesting strain dependent host adaptation. Finally, D. agamarum was shown to be able to persist for at least seven years in a lizard colony, persistently causing severe disease in several lizard species.

Prolonged environmental persistence requires efficient disinfection procedures to control Devriesea agamarum-associated disease in lizards.

Aims:  Devriesea agamarum infection causes chronic proliferative dermatitis, especially in desert dwelling lizards. The present study was concerned with evaluating persistency of D. agamarum in the environment and the evaluation of the efficacy of various disinfection procedures.

Dermatological diseases in lizards

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.

Antimicrobial peptides in frog poisons constitute a molecular toxin delivery system against predators

Animals using toxic peptides and proteins for predation or defense typically depend on specialized morphological structures, like fangs, spines, or a stinger, for effective intoxication. Here we show that amphibian poisons instead incorporate their own molecular system for toxin delivery to attacking predators. Skin-secreted peptides, generally considered part of the amphibian immune system, permeabilize oral epithelial tissue and enable fast access of cosecreted toxins to the predator’s bloodstream and organs. This absorption-enhancing system exists in at least three distantly related frog lineages and is likely to be a widespread adaptation, determining the outcome of predator–prey encounters in hundreds of species.To avoid being eaten, poisonous prey animals must rely on fast passage of toxins across a predator’s oral tissue, a major barrier to large molecules. Here, Raaymakers et al. show that antimicrobial peptides co secreted with frog toxins enhance intoxication of a snake predator by permeabilizing oral cell layers.