This rat shows typical SDA symptoms of neck and facial
swelling as well as an enlarged, ulcerated eye.
(Picture from: Facing Deadly Viruses by A. Gandi)
SDA: Be aware of this deadly threat
to pet rats
What is SDA?
SDA is an abbreviation for the Sialodacryoadentitis virus, a highly
contagious coronavirus. Although related to the mouse hepatitis virus, SDA is a separate type of virus
and affects only rats (it not possible for humans to contract SDA). SDA
weakens the immune system, allowing secondary infections to quickly take hold and cause severe
damage. In laboratory environments where rats are shielded from most infectious organisms,
SDA causes few deaths. However, bacterial infections such as mycoplasma pulmonis
(myco) are almost always present in the pet population. When SDA is contracted by an animal
with any secondary infection, a much higher mortality rate is the result
because of the compromised immune system.
Some pet rats die after contracting the SDA virus.
Possible Symptoms
The most obvious signs of SDA are seen in the head region. Sneezing and porphyrin discharge around the nose and eyes often accompanies swelling under the neck caused by enlarged lymph nodes and inflamed salivary glands. Swelling and infection of the eyes leads to squinting, eye rubbing, ulcers of the cornea, and bleeding inside the eye. These symptoms sometimes promote self-mutilation as rats scratch their eyes. Damage can be permanent in the form of lost eyes.
This rat shows typical SDA symptoms of neck and facial
swelling as well as an enlarged, ulcerated eye.
(Picture from: Facing Deadly Viruses by A. Gandi)
Sometimes infected rats show no symptoms. These rats are highly contagious yet appear to remain healthy.
The aggressive secondary infections are often too much for rats to handle, especially older ones with chronic respiratory problems, and death can occur within days of infection.
How is it spread?
The SDA virus is passed through the air and by direct contact with respiratory secretions. These secretions may remain on food containers, bedding, and even your clothes and hair if you have handled an infected rat.
SDA is self-limiting, meaning it runs its course and resolves without medication. The length of time a rat is contagious (sheds the virus) is approximately seven days. If an infected rat enters a colony, it can infect the other rats one by one over the course of days. This means that the virus has the potential to exist much longer in a colony than it does in an individual. If litters are born in this period, the babies can get the virus, extending the virus's life in the colony even further.
The virus does not exist in a latent carrier state (there are no instances where a rat can become a long-term carrier). Once infected, it may take a rat up to 2 months to recover.
Treatment
There is no treatment for SDA itself. Antibiotics are only effective in treating the secondary bacterial infections. Myco is the most common secondary infection that accompanies SDA infection. It should be treated aggressively with antibiotics.
Eye moisturizers such as opthamatic ointment may help to keep eyes clean and moist. Fluids can be administered to prevent dehydration while the rat is ill.
Prevention
It is very important that you wash your hands, hair and clothing after handling rats that may have been exposed to the virus such as rats at a pet store. This removes any respiratory secretions before you handle your own rats.
Quarantine is a very important policy to prevent the spread of SDA. If you buy or adopt a new rat, you must consider the newcomer as a potential carrier of SDA and quarantine before allowing him/her into your established colony. To be effective, quarantine MUST be done in another building. All rooms in a house share the same air and SDA is passed easily through the air. Do not make the mistake of believing that "quarantining" new animals in another room of the house will be enough. Alicia Gandi of rodentfancy.com indicates that the 2-week quarantine period that is often recommended is not long enough. Her rat colony became infected with SDA even though she quarantined new rats for 2 weeks. Therefore, a quarantine period of 3 weeks is highly recommended for new rats.
If a rat is healthy after 3 weeks, it is considered safe to introduce it to the other rats. However, if you have an infected rat, it is recommended that you isolate the rat for 6-8 weeks (in the separate facility away from other rats where it was quarantined to begin with).
If a rat colony becomes infected, the colony must be isolated for a minimum of 6-8 weeks. If rats are breeding in the colony, all breeding must be stopped for at least 6-8 weeks after the last litter is weaned. Of course, no new rats should be introduced during this time.
SDA in Canada
SDA outbreaks in the United States are becoming alarmingly common. (See SDA Outbreak Tracking Data) Our close proximity to the States and easy trade relations have allowed infected rats to cross the border. I have been informed that suspected SDA infections have been observed in rats in southern Ontario and in British Columbia. It is often irresponsible breeders for the pet/feeder trade who get these infections in their rat colonies and they are never responsible enough to get it confirmed by a vet. One rat breeder in Ontario apparently had to stop breeding after an SDA outbreak. SDA is certainly not as common in Canada as it is in the United States. Let's help keep it that way. If you bring a rat from the United States into Canada, please please please make sure you quarantine in a separate facility for 3-4 weeks. Rat owners in areas of Canada where SDA is known to have occurred should be aware and take precautions as well.
Conclusion
In a perfect world, all pet owners would take the threat of SDA seriously and take proper measures to protect their pets and the pets of others. Sadly, this is not always the case. If you are buying from a breeder, ask about their quarantine procedures. If you get new rats, always quarantine them at the house of a friend or family member. Quarantines are inconvenient because they involve extra planning and extra work. However, this inconvenience is much easier to bear than the guilt a person would feel if they had been impatient and skipped quarantine and caused the death of many of their beloved pet rats as a result.
It is important to be honest about SDA infection. If your rats are infected it is important to inform the breeder or store where you got the rat and encourage them to take measures to begin a full-length quarantine. It is also important to be supportive. Hostile reactions to people with infected rats only encourages people to lie and keep SDA infections a secret.
The measures we must take to prevent further outbreaks of SDA may sound extreme, but it is our responsibility to our pets to be vigilant and protect their health and well-being.
References
Sialodacryoadentitis in Pet Rats: http://www.rmca.org/Articles/sda.htm
Facing Deadly Viruses (by A. Gandi): http://www.rodentfancy.com/rmfe/virus.shtml
SDA Virus in Brief: http://www.ratlovers.org/articles/SDA.html