The Science

Sialodacryoadenitis Virus (SDA) is a naturally occurring pathogen in rats, and is related to mouse hepatitis, rat coronavirus and human coronavirus. It is a highly infectious disease but on its own will cause very few deaths. It is only when it is mixed with another disease (i.e. your rat has something else on top of SDA) that it becomes a real killer. Although mostly affecting the younger rats, it has also been found to be quite lethal in older rats (who have not been exposed before), with death usually following pretty quickly after the older rat getting the disease.

It can be passed fairly quickly through the air, by direct contact with an infected rat, or by handling of rats without proper cleaning in between.


Symptoms can be pretty varied and you may not see them all. If in doubt, always contact your Vet. Symptoms can include sneezing, red discharge around the eyes and nose, swelling/infection around the eyes, dislike of bright light, eye ulcers and squinting or blinking. Some swelling around the neck glands may occur as this is the most likely site for the virus to attack. Most rats will appear healthy in all other ways although some may go off their food.

Generally, adults will be immune due to previous infection with the Virus, although this is not always the case. Young weanlings who are infected will normally show signs of conjunctivitis (normally for a week or less).

Most clinical signs usually disappear within about a week, but any eye problems may take longer to clear up.


SDA is normally diagnosed by a Vet using any clinical signs you can tell him, tissue tests, and blood tests to detect if there are any antibodies to the virus. Since blood tests are extremely hard to do on rats (you need a lot of blood for testing) this is sometimes difficult to achieve and so the Vet may just rely on any clinical signs you tell him about.


There is no cure for SDA, but any secondary infections that arise can be treated quite successfully. Mycoplasma seems to be the most common secondary infection seen with SDA and should be treated as promptly as possible to prevent complications and even death. Antibiotics will probably be what your Vet gives you to fight of the secondary infections. Make sure to quarantine any pregnant females as, although they don't seem as susceptible to SDA and antibiotics may harm the unborn babies, they have a small chance of still becoming infected.


Do not handle any rats that are not your own (this includes at pet shops, friend's, shows, etc. without thoroughly disinfecting your hands and changing your clothes first.

Since quarantining new rats is always a standard practice we should follow anyway, this should help identify if new rats (or rats that have been in contact with rats outside the home - at shows, etc) are carrying the disease. Basically, if you don't want the disease make sure you use a long quarantine period (6-8 weeks) and perhaps rethink taking rats to shows.

Do not breed from infected stock for at least 6-8 weeks to let the disease run its course. Do not sell or give away any rats known to have been exposed and do not expose anyone else rats to any infected stock either.