SDA Virus (contagious rat virus sweeping through the USA)

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Staff member
Jul 21, 2007
Toronto, Canada, Earth
Unfortunately SDA outbreaks are sweeping across the USA again...it happens every few years. It often flares out of control at rat mills, BYB's (backyard breeders), not so ethical breeders, rescues etc...if its not controlled it gets out into the main rat population and spreads like wildfire from there.

SDA (Sialodacryoadenitis virus or Rat Coronavirus)

Key Points
1) Its ONLY contagious to other rats (not humans or other pets)
2) The rat is only truly contagious for a week afterwards the virus sheds the body and they are immune to that particular strain of SDA (there is no carrier state)
3) If you only have a couple of rats the virus will go through them quickly. If you have larger groups or rats in different rooms etc. then it could take a lot longer to slowly spread and affect each rat, shed and have your colony clear of any contagious virus. If you have babies it takes even longer as a mother's immune system protects her babies until they develop their own immune system and this is when these babies will become symptomatic. A rattery should shut down for 3 months to be safe and make sure the virus has cleared their colony.
4) Antibiotics will not affect the virus but once it sheds the opportunistic secondary infections kick in and this is what you are fighting with the antibiotics. Its best to start the antibiotics ASAP to allow them time to build up in the system so they can fight the secondary infections.
5) Antibiotics are required for any symptomatic rats and will be needed long term. if you only have a few rats it might be better to treat them all just in case.
6) IF you feel you are dealing with SDA with your rat/rats/colony you need to go into a very strict lockdown, no rats in or out, no handling of healthy rats within 3 hours of handling sick ones as the virus can live off-host for 3 hours on fomites, including your skin, clothes and even in your nasal passages.
7) You have to treat this lockdown like you do with covid-19 without the masks. YOU are the person responsible in stopping the spread. If your rat has to go to the vet, let them know you have a suspected case of SDA virus and cannot have an appointment within 3 hours of another rat patient (just to be safe). When going out to a petstore, make sure to wash your hands and change your clothes IF going before that 3 hour window expires from handling your sick rats and handling items at a petstore. A shower and change of clothes (blow your nose as well) is the only way you can prevent the transmission of the virus in that 3 hour window.

Symptoms and Timeline
You usually bring home SDA with a new sick rat (not necessarily showing symptoms) or on your own body after handling or being near a sick rat, then going home and handling your resident rats in less than 3 hours. For eg. at the vet clinic, someone brings in their sick rat when you are there and you get exposed. Sneezing is the main method of transmission and a sneeze can travel up to 6 feet.

There's 2 possible starts to this virus, one where a formerly sick rat or one who you thought was healthy suddenly dies (within 24-72 hours or going downhill and not responding to anything), or your rats start to sneeze. You may find facial swelling/eye issues (you would see the connective tissue showing in front of the eye) and/or a round lump in the middle of their throat (swollen lymph nodes/glands) in SOME rats, not all. This is a very definitive sign that you are dealing with SDA.
eyes/facial swelling in a rat with SDA

lump under throat in rats with SDA
this is what you usually will see...

but it can be huge as well...

The eyes and throat will resolve within a week or so but giving Metacam or ibuprofen during this time can help with discomfort and swelling.

Sneezing will spread throughout your colony and the crackling, wheezing could start with some. The sickest rats will look very ill, be labouring for air, and might need emergency attention. You will have to get used to holding your rats sides to your ear to listen to their breathing as sometimes the worst cases have lungs that are constricted (like asthma) and they cannot get air in to breathe and your can only hear it with this method of "ratphoning". They may be using their abdominal muscles to breathe, may panic and run, breathe open-mouthed (gasps). These are the most severe cases, some/most should just get very sick and need long term antibiotics. Older or compromised rats are the ones most likely to die from this even with antibiotics.

Rats often don't respond right away to the antibiotics with a virus, but will slowly improve rather than the faster improvement with a regular respiratory infection. As long as they are eating, drinking you have a good chance.

If your rat is having issues eating hard foods, offer soft foods they can lick up. Eating solids is chewing/swallowing while not breathing, which a rat that is already having trouble breathing cannot do. Soft foods like baby food, flavoured baby cereal (a good one especially to keep weight on), even a lab block mush, or Ensure (meal replacement) they can lick, swalllow, breathe...and are more comfortable doing so.

• Baytril or enrofloxacin or ciprofloxacin at 15 mg/kg BID (twice a day)

• Doxycycline at 10 mg/kg BID

• Metacam at 0.8 mg/kg SID (once a day) for eye/throat issues
Ibuprofen at 20 mg/kg every 4-6 hours (only for a few days as its hard on the kidneys)

• Other alternatives are Clavamox (20 mg/kg BID) or Azithromycin (20 mg/kg SID), paired with Baytril/Enro.

• An inhaler or oral steroids (prednisone) or injectable steroids (dexamethasone given orally or injected sub-cutaneously) can help open up the constricted lungs of the worst cases

• Euthanasia for rats that are suffering, not eating or drinking even when offered to be hand fed or syringe fed

Locations (will be updated as needed) with reported cases of SDA in the U.S. so far

SDAV has been confirmed in:
Arkansas (rats purchased in Feb, deaths from SDA suspected - test results came back positive in AUGUST)
OKLAHOMA - SDAV+ rats unknowingly purchased by a Breeder in September.
West Linn, Oregon (lady knowingly selling SDAV rats on Craigslist)
Iowa (confirmed by rattery )
Colorado (confirmed by rattery )
Michigan (confirmed by rattery )
Also reported (not yet confirmed) in:
Florida (rattery/rescue) - adopter has had definitive symptoms of SDA with her own rat after bringing home sick babies, and Rattery has lost a LOT of their own rats.
Las Vegas has reported Breeder selling SDA rats for pets & feeders (reported by member )
A death in Vegas (fits SDA profile )
******Possible Sendai in New York waiting on confirmation*****

Last edited:


Well-Known Member
Feb 1, 2019
You said only rats can catch it. That means mice cannot yes..? Just wondering here


Active Member
May 9, 2020
New York
I just lost a rat a couple weeks ago to an unexplained illness that came on very suddenly. Could we discuss this in more detail to figure out if she had SDA or not? I’m worried as she was living in my colony of 7 other rats. They have sneezed a little bit she was not sneezing before she died so I just want to make sure it’s ok. Pepper has been sneezing and was put on antibiotics over a week ago and is recovering with no more sneezing but I’m still very worried. The vet was very surprised to hear about the quick illness that took Bean’s life but he never brought up SDA. Let me know if we can talk more in-depth about bean’s illness to know if it was SDA or not. I have a video of her breathing too.

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