Amphibian virology

An Aerolysin-like Pore-Forming Protein Complex Targets Viral Envelope to Inactivate Herpes Simplex Virus Type 1

Because most of animal viruses are enveloped, cytoplasmic entry of these viruses via fusion with cellular membrane initiates their invasion. However, the strategies in which host cells counteract cytoplasmic entry of such viruses are incompletely understood. Pore-forming toxin aerolysin-like proteins (ALPs) exist throughout the animal kingdom, but their functions are mostly unknown. In this study, we report that βγ-crystallin fused aerolysin-like protein and trefoil factor complex (βγ-CAT), an ALP and trefoil factor complex from the frog Bombina maxima, directly blocks enveloped virus invasion by interfering with cytoplasmic entry. βγ-CAT targeted acidic glycosphingolipids on the HSV type 1 (HSV-1) envelope to induce pore formation, as indicated by the oligomer formation of protein and potassium and calcium ion efflux. Meanwhile, βγ-CAT formed ring-like oligomers of ∼10 nm in diameter on the liposomes and induced dye release from liposomes that mimic viral envelope. Unexpectedly, transmission electron microscopy analysis showed that the βγ-CAT-treated HSV-1 was visibly as intact as the vehicle-treated HSV-1, indicating that βγ-CAT did not lyse the viral envelope. However, the cytoplasmic entry of the βγ-CAT-treated HSV-1 into HeLa cells was totally hindered. In vivo, topical application of βγ-CAT attenuated the HSV-1 corneal infection in mice. Collectively, these results uncovered that βγ-CAT possesses the capacity to counteract enveloped virus invasion with its featured antiviral-acting manner. Our findings will also largely help to illustrate the putative antiviral activity of animal ALPs.

Research-Relevant Background Lesions and Conditions in Common Avian and Aquatic Species

Non-mammalian vertebrates including birds, fish, and amphibians have a long history of contributing to ground-breaking scientific discoveries. Because these species offer several experimental advantages over higher vertebrates and share extensive anatomic and genetic homology with their mammalian counterparts, they remain popular animal models in a variety of fields such as developmental biology, physiology, toxicology, drug discovery, immunology, toxicology, and infectious disease. As with all animal models, familiarity with the anatomy, physiology, and spontaneous diseases of these species is necessary for ensuring animal welfare, as well as accurate interpretation and reporting of study findings. Working with avian and aquatic species can be especially challenging in this respect due to their rich diversity and array of unique adaptations. Here, we provide an overview of the research-relevant anatomic features, non-infectious conditions, and infectious diseases that impact research colonies of birds and aquatic animals, including fish and Xenopus species.

Intraerythrocytic iridovirus in central bearded dragons (Pogona vitticeps)

Three adult central bearded dragons ( Pogona vitticeps) originating from a commercial breeding facility presented with clinical signs, including anorexia, dehydration, white multifocal lesions on the dorsal aspect of the tongue, blepharospasm, and weight loss. In 1 of 3 lizards, a marked regenerative anemia was noted, and all 3 bearded dragons had erythrocytic intracytoplasmic inclusion bodies. Nine bearded dragons housed in contact also had identical, but fewer intraerythrocytic inclusions. Inclusion bodies examined by electron microscopy had particles consistent with iridoviruses. Attempts to culture the virus were unsuccessful; however, amplification and sequencing of regions of the viral DNA polymerase by polymerase chain reaction confirmed the presence of an iridovirus. One of the bearded dragons died, while the 2 others showing clinical signs were euthanized. The remaining 9 infected bearded dragons of the teaching colony were also euthanized. Postmortem examination revealed a moderate, multifocal, lymphoplasmacytic or mononuclear adenitis of the tongue in the 3 bearded dragons, and a lymphohistiocytic hepatitis with bacterial granulomas in 2 lizards.

Tracking viral particles in the intestinal contents of the American bullfrog, Lithobates catesbeianus, by Transmission Electron Microscopy

Feces are an important viral agent elimination route for infected carrier animals and in aquatic organisms these pathogenic agents can very rapidly propagate due to the habitation environment. The objective of this work is to track viral particles in the intestinal contents of bullfrogs (Lithobates catesbeianus) from five commercial frog farms in the region of Vale do Paraíba, in the State of São Paulo, Brazil, using negative contrast transmission electron microscopy (TEM). The Coronaviridae, Paramyxoviridae, Parvoviridae and Herpesviridae families were observed and photographed in specimens. This work emphasizes the importance of adopting sanitary measures in commercial farms and confirms that observing feces by TEM is an efficient and rapid diagnostic tool for detecting viral agents.

Clinical approach to dermatologic disease in exotic animals

Skin disease is an extremely common presenting complaint to the exotic animal practitioner. A systematic diagnostic approach is necessary in these cases to achieve a diagnosis and formulate an effective treatment plan. In all exotic species, husbandry plays a central role in the pathogenesis of cutaneous disease, so a thorough evaluation of the husbandry is critical for successful management. The clinical approach to skin disease in exotic animal patients is reviewed with specific focus on structure and function of the skin, diagnostic testing, and differential diagnoses for commonly encountered cutaneous diseases.

Selected emerging infectious diseases of squamata

It is important that reptile clinicians have an appreciation for the epidemiology, clinical signs, pathology, diagnostic options, and prognostic parameters for novel and emerging infectious diseases in squamates. This article provides an update on emerging squamate diseases reported in the primary literature within the past decade. Updates on adenovirus, iridovirus, rhabdovirus, arenavirus, and paramyxovirus epidemiology, divergence, and host fidelity are presented. A new emerging bacterial disease of Uromastyx species, Devriesea agamarum, is reviewed. Chrysosporium ophiodiicola-associated mortality in North American snakes is discussed. Cryptosporidium and pentastomid infections in squamates are highlighted among emerging parasitic infections.

Diseases of Amphibians

The development and refinement of amphibian medicine comprise an ongoing science that reflects the unique life history of these animals and our growing knowledge of amphibian diseases. Amphibians are notoriously fastidious in terms of captive care requirements, and the majority of diseases of amphibians maintained in captivity will relate directly or indirectly to husbandry and management. Investigators have described many infectious and noninfectious diseases that occur among various species of captive and wild amphibians, and there is considerable overlap in the diseases of captive versus free-ranging populations. In this article, some of the more commonly reported infectious and noninfectious diseases as well as their etiological agents and causative factors are reviewed. Some of the more common amphibian diseases with bacterial etiologies include bacterial dermatosepticemia or "red leg syndrome," flavobacteriosis, mycobacteriosis, and chlamydiosis. The most common viral diseases of amphibians are caused by the ranaviruses, which have an impact on many species of anurans and caudates. Mycotic and mycotic-like organisms cause a number of diseases among amphibians, including chytridiomycosis, zygomycoses, chromomycoses, saprolegniasis, and ichthyophoniasis. Protozoan parasites of amphibians include a variety of amoeba, ciliates, flagellates, and sporozoans Common metazoan parasites include various myxozoans, helminths (particularly trematodes and nematodes), and arthropods. Commonly encountered noninfectious disease etiologies for amphibians include neoplasia, absolute or specific nutritional deficiencies or overloads, chemical toxicities, and inadequate husbandry or environmental management.

Amphibian renal disease

Amphibians by nature have an intimate connection with the aquatic environment at some stage of development and fight an osmotic battle due to the influx of water. Many amphibians have acquired a more terrestrial existence at later stages of development and consequently have physiologic adaptations to conserve moisture. Renal adaptations have allowed amphibians successfully to bridge the gap between aqueous and terrestrial habitats. The kidneys, skin,and, in many amphibian species, the urinary bladder play key roles in fluid homeostasis. Renal impairment may be responsible for the clinical manifestation of disease, morbidity, and mortality.