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Description |
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(Batrachochytrium Dendrobatidis)
The chytrid fungus Batrachochytrium (B.) dendrobatidis was first identified in Australia in 1998 and named in 1999. This fungus is thought to be responsible for the population
decline and the global extinction of >200 amphibian species. Infections with B. dendrobatidis are in many cases associated with very high mortality rates (in lab up to 100%), but the fungus is not necessarily lethal. Other factors such as stress or co-infections with other pathogens also appear to play a role. B. dendrobatidis multiplies in keratinized tissue and therefore affects primarily the outer skin of adult animals (stratum corneum to the stratum granulosum). In larvae, the horn strips on the mouth are affected. During metamorphosis the infections can lead to dramatic high mortality rates. The clinical symptoms are often nonspecific and may, in addition to the skin (often appear acroscopically unchanged or „blunt“ or depigmented; hyperkeratosis and massive skinning episodes, mixed infections with severe erosions of the skin) or behavioural changes (atypical behaviour, such as prolonged stay in the water, ataxia and CNS problems). Spontaneous deaths without previous overt clinical disease are also observed.
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Description |
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Ranaviruses: Overview and Host Impact
Ranaviruses are enveloped, double-stranded DNA viruses belonging to the family Iridoviridae. They are globally distributed and possess a remarkably broad host range, infecting multiple animal classes including amphibians, reptiles, and fish. Transmission occurs via direct contact, environmental contamination, or cannibalism (ingestion of infected animals).
Amphibians
Ranaviruses are increasingly detected in amphibians and are associated with systemic disease and mass mortality. Two clinical forms are recognized:
Haemorrhagic form: marked by erythema (especially on the abdomen and upper legs), ulceration of the toes, and increased bleeding tendency.
Cutaneous form: may present with skin lesions.
Some animals succumb rapidly without prior signs of illness, while others may act as inapparent carriers.
Chelonians (Turtles and Tortoises)
In chelonians, ranaviruses are linked to:
Stomatitis
Hepatitis
Rhinitis and pneumonia
Sudden death
Detection in live animals is typically performed using oral swabs or blood samples. In deceased animals, liver, tongue, and skin are preferred tissues for virus identification.
Lizards
Ranavirus infection in lizards is associated with:
Skin lesions
Stomatitis
Granulomatous inflammation
Hepatitis
Mass mortality
Diagnostic sampling includes oral swabs or skin in live animals, and liver, tongue, and skin in post-mortem cases.
Snakes
In snakes, ranaviruses have been observed to cause:
Granulomatous lesions in the oral cavity and liver
Stomatitis and hepatic changes
Detection is carried out using oral swabs or liver samples.
Fish
Ranaviruses also affect fish, with presentations ranging from clinically inapparent infections to systemic disease with mass mortality.
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Sample Requirements |
Snakes:Oral and cloacal swabs, liver
Chelonian: Oral and cloacal swabs, blood, tongue, liver
Lizards: Oral and cloacal swabs, skin, liver
Fish: biopsy (gills), blood, tissue (e.g. Liver or kidney), swab (skin)
Amphibians: biopsy (toe clips, tail clips), EB or drops of blood on filter paper, tissue (above all liver, kidney), perhaps swab without medium (skin) .
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