In the last decades more scientific research has been done on viral diseases in the different species of reptiles (snakes, lizards, chelonians and crocodiles). New techniques for the detection of viral antigens have been developed. The presence of genetic viral material can be demonstrated with polymerase chain reaction (PCR) or in situ hybridization. Antibodies against a number of known viruses can be detected.

However, very often primary damage caused by viruses is overshadowed by secondary bacterial, mycotic or parasitic invasions. Moreover, from many families of viruses it is not known whether they are able to infect reptiles, or are pathogenic for them. The type of disease caused by these viruses in reptiles is not always known.

Therefore, demonstrating the presence of viral genetic material, DNA or RNA, with the aid of molecular biological techniques, is still not proof for the pathogenicity of the virus.

The way in which people keep reptiles can lead to spread of viruses. Not only within the collection of animals, but with the possibilities of good and fast transportation, global distribution of viruses is very well possible. Many private reptile owners don't have the opportunity to organize a good quarantine unit. The insight in spread of viruses often lacks. The people exchange animals far too easy. Besides, commercially available diagnostic tests on the presence of viruses in an individual or group of animals are vastly insufficient. Only few laboratories offer these tests.

In viral induced disease in a reptile, the clinical signs are often not determined by the initial virus. A variety of secondary pathogens can cloud the clinical signs in such a way, that people forget to investigate whether a virus might be the primary cause of the disease.

When one animal in a collection suddenly falls ill the owner may not immediately take action to have the animal thoroughly checked medically. If the animal is not immediately isolated and quarantined, and aggressive hygienic measurements are not taken, a viral induced outbreak of disease is very fast a fact. The virus gets the chance of spreading within a population of reptiles in a short period of time.

The introduction of a highly virulent virus in a naïve, susceptible population of reptiles can lead to devastating disease. A number of viral infections can cause high mortality and morbidity. Therefore, reptile veterinarians must educate their clients in achieving a good quarantine program when introducing new individuals in their collection. A good quarantine unit, physically separated from the established collection should be the goal.

High standards of hygiene should be maintained. Used materials, hands, shoes and clothes of the caretaker should be cleaned and disinfected. When disinfectants like chlorhexidine, quaternary ammonium agent, formalin, or iodophores are used, good ventilation and removing remnants of the disinfectant is essential.

Housing, temperature and feeding should be optimally adjusted to the species of reptile. A complete physical examination should be accomplished. Common parasitic infestations should be established and eliminated.

Antibodies against ophidian paramyxo viruses (OPMV) can be determined in a number of laboratories. Some laboratories claim to be able to detect OPMV antigen with PCR techniques. Serological determination of chelonian herpes virus infection and PCR on the virus is sometimes possible. Full administration for every individual animal should be kept. When an animal from the quarantine area or the established collection dies, a complete necropsy should be done as soon as possible by a reptile specialized pathologist.

A number of DNA and RNA viruses that commonly may occur in different species of reptiles will be discussed in this lecture. Clinical and pathological changes, diagnostics, (possible) therapy, control and epizootiology will be discussed.