The mode of transmission is via contaminated water. The most common presentation is an explosive mortality event with death due to peracute systemic haemorrhagic disease. In these cases, usually there are no external lesions. Diagnosis is by virus culture followed by identification using electron microscope or PCR. There is currently no known prevention or control method.
A study in the UK has confirmed that ranavirus not only causes sudden
mass-mortality events, but also long term population declines. The
researchers examined wild common frog (Rana temporaria) numbers in a
selection of populations around the country where ranavirus disease
had been previously reported since 1996. The finding was that half of
the populations has had repeated outbreaks of the disease. In almost a
quarter of the cases, frog numbers had dropped by 81 percent over the
last 12 years."
Read more: RANAVIRUS, FROG - NETHERLANDS: OIE