Etiologic agents of infectious diseases are numerous. They comprise viral, bacterial, mycotic, protozoal, helminthic species.

A number of diseases induced by different agents will be discussed.

Ranavirus infections have been associated with amphibian mass mortalities, and, as they are considered to be emerging diseases, the infection has been listed as notifiable by the World Organization for Animal Health. In the United Kingdom, where the infection emerged in the 1980s, significant local declines in numbers of adult common frogs (Rana temporaria) have been recorded. In mainland Europe, Ranavirus disease and mortality in wild amphibians have been reported unambiguously only in Spain in common midwife toads (CMT, Alytes obstetricans) and alpine newts (Ichthyosaura alpestris cyreni) and in Denmark in wild edible frogs (Pelophylax kl. esculentus). Frogs may show hemorrhages in the skin from the eardrums and mouth; tadpoles severe edema and erythema.

In red leg disease, the animals may show erythema in the skin, hemorrhages, subcutaneous edema and ulceration of the skin. It is a multifactorial disease, starting with inadequate husbandry and complicated by bacteria like Pseudomonas or Aeromonas.

Another bacterial-induced disease is mycobacterial infection, mostly by atypical mycobacteria like Mycobacterium marinum. Clinical signs can be ulceration in the skin, but very often only aspecific signs such as emaciation occur. In the latter, diagnosis is challenging in the living animal.

Batrachochytrium dendrobatidis (Bd) infections have been associated with amphibian mass mortalities and population decline worldwide. Batrachochytrium salamandrivorans (Bsal) is an emerging fungal pathogen that has caused recent die-offs of native salamanders in Europe. Bsal appears to have originated in Asia and may have been introduced by humans into wild populations in Europe through commercial trade of amphibians. Clinical signs in the amphibia may be dry, greyish skin with the animals spending more time in the water than usual, anorexia and death.

Different protozoal species can cause disease in amphibians. The animals may present with diarrhea and even in advanced cases cloacal prolapse. Different clinical diseases will be discussed.

Nematodes in the lungs are rather common in wild amphibia. In captivity, when the infection pressure gets higher and maybe the immune system somewhat compromised, the presence of lungworms may lead to pneumonia and disease.

Different parasitic infestations will be presented.