(Sialodacryoadenitis virus or Rat corona virus)

Abbreviations

SDAV
SDA virus
SDA

Definition

Sialo= “salivary” + dacryo = “lacrimal” + adenitis= “inflammation of lymph nodes and glands”

Sialodacryoadenitis virus is an RNA virus, genus coronavirus.

Clinical Signs

Swelling around the neck and cervical nodes. Bulging of eyes. May see porphyrin staining, bleeding, or discoloration of tissue around the eyes. May see symptoms of secondary respiratory infection with sneezing, fluid filled lungs, weight loss, and loss of appetite.

*Note: for additional information on recognizing various signs of pain or discomfort refer to: Signs of Pain In Rats.

Etiology

SDAV is a highly contagious virus that weakens the immune system. Alone it is not fatal, however it opens the door for secondary bacterial infections that can kill. In a laboratory environment SDAV has a low mortality rate. This is due to the fact that in the lab the secondary diseases are not in place to cause the infections that kill our rats.

SDAV is an RNA coronavirus. It is an airborne virus that is contracted via respiratory aerosol commonly spread by direct contact with affected rats. Contact with food, bedding, cages, or other accessories used by infected rats can spread the disease. Viral secretions carried on human skin, clothing, or in mucus membranes can also contribute to the spread of this illness.

Once exposed to the SDA virus rats can begin to show symptoms as early as 5 days (porphyrin staining) with respiratory involvement and cervical swelling by 7–8 days. In a laboratory setting the virus remains active in a single rat 7–10 days and doesn’t have a carrier state. In a multiple rat colony this time frame must be altered as the disease spreads form one rat to the next. In a breeding colony the time frame must be altered to include litter transmission as well as multiple rat transmission.

The secondary infections will persist for a longer amount of time, depending on the bacteria or other viruses involved.

In some cases the rats that survive the SDAV outbreak have eye and/or respiratory damage for life.

Not all rats infected with SDAV show symptoms.

The SDA virus often presents as a characteristic inflammation of submaxillary and parotid
salivary gland (which can result in the necrosis of the tissue). This will sometimes give the appearance of a shortened or swollen neck. Cervical lymph nodes can also be affected.

This virus also affects the harderian and intraorbital lacrimal glands behind the eyes. In a visual diagnosis you will often see bulging eyes, lacerations, porphyrin discharge, ocular lesions, bleeding, infection of the eyes or surrounding tissue, or squinting due to photosensitivity. The eyes can be lost due to self-mutilation from scratching or infection. Sight can be lost or compromised for life. In some case the eye infection will cause facial swelling. Eye bulging may take several weeks to subside due to retro-orbital swelling.

In secondary infections of the respiratory tract, and some of the other systems, the organism most often responsible, but not always, is that of mycoplasma. It is this organism that is responsible for the majority of respiratory disease that naturally exists in most pet rats, and which in rats, makes contracting SDAV so deadly. With SDAV respiratory involvement and with the secondary infections you will notice such symptoms as: sneezing, fluid in the lungs, porphyrin staining from eyes and nose, loss of appetite, lowered fluid intake, weight loss, lethargy, and general respiratory distress.

In a laboratory setting where the rats haven’t been exposed to mycoplasma or other pathogens, the mortality rate for SDAV is low.

Figures

Case History and Photos

• Fig. 1: SDAV case history and photos of 6–month–old rat (Pepsi).
• Fig. 2: Coronaviruses (RCV and SDAV) courtesy of: University of Missouri – Comparative Medicine Program and IDEXX-BioAnalytics (IDEXX RADIL), and Craig Franklin, DVM, PhD, Associate Professor.

Diagnostics

Testing is the only way to determine what organism has infected your colony. It is recommended to test when there is any major illness whether or not the classic signs of SDAV are present. There have been SDAV cases where the classic signs are absent. There are also instances where other diseases mimic SDAV.

The standard test for Sendai is the ELISA (enzyme-linked immunosorbent assay) which can be performed at several labs.

IDEXX RADIL offers a newer test: MFI (Multiplex Fluorescent Immunoassay) which is more sensitive. Have your veterinarian contact the testing facility for instructions on collecting and sending the blood sample.

During a viral event broad-spectrum antibiotics are given to the exposed rats to treat the often fatal, secondary opportunistic bacterial infections. Usually that approach works well. However, there are times when the bacteria involved is resistant. A culture and sensitivity test can ensure that the antibiotics given are appropriate.

*Note: Before having blood drawn for an ELISA test you must allow time for antibodies to
develop. This will take 2–3 weeks after the initial exposure (1–2 weeks after clinical symptoms appear). Testing a clinically ill rat can often result in false negative results.

Treatment

SDAV is a self-limiting disease. There is no treatment for SDAV. It must run its course and will clear up within 7–10 days. After antibodies have been made as a natural response to the virus the affected rat will be immune (only) to that particular strain.

Treatment for secondary bacterial infections that often accompany this particular viral infection, and seen most often in very young, and very old rats, or those rats that are immunosuppressed are as follows:

Broad-spectrum antibiotics such as those used for mycoplasma respiratory infection given at the maximum dosage for 3—4 weeks. Refer to the Rat Medication Guide for broad-spectrum antibiotics.

*Note: Treatment with antibiotics must be aggressive to be effective.

For eyes, use a topical ophthalmic antibiotic ointment. Lubricate with natural “tears” to help with dryness.

Nursing Care

• Maintain a clean, quiet, draft free environment.
• Provide additional warmth to maintain body temperature within normal limits. It is essential that the rat does not become overheated or dehydrated. The rat should also be able to move away from the heat source if it becomes uncomfortable. If the rat is unconscious or immobile extreme care must be taken to keep the heat low and stable.
  • You can use an isothermic product that is heated in the microwave such as SnuggleSafe®. Make sure to follow the product directions carefully and wrap in a towel before placing in the cage. SnuggleSafe® will provide heat for 12 hours before needing to be reheated. Other similar types of products may vary in re-heat time. Check directions for individual product.
  • If using a heating pad (good for long term use) use only the low heat setting, put a thick towel in between the pad and the cage bottom, and place beneath a corner of the cage.
  • If none of these options are available you can use a plastic bottle filled with hot water, and wrapped in a towel, in the corner of the cage.
• Provide extra fluids and nutrition support appropriate for an ill rat.
• Keep affected rats away from bright lighting.

Outcome

• Reduced severity of symptoms by treating aggressively
• Reduced mortality rate

Prevention

As rat owners it is our responsibility to keep our rats healthy. No matter what diseases are in our area implementing the proper safety procedures can ensure us of a relatively safe environment for our rats. Bringing in a new rat from ANY source is always a risk. If you don’t have the means to properly quarantine, then please reconsider getting new rats.

Keeping your colony healthy can give the rats an edge in the event of an outbreak. Good nutrition and cleanliness can help a rat’s immune system stay strong. Rats suffering from inadequate nutrition or that live in poorly maintained environment will have a significantly lower chance of surviving a major outbreak.

*Note: Rat keepers who breed even one litter need to focus on the extended responsibilities of the breeder.

SDA Virus “Shelf Life”

The SDA virus can remain infectious for up to 3 hours away from its host. It can be killed immediately using detergents and lipid solvents or by exposing the virus to a temperature of (or above) 133^oF. for 30 minutes.

Quarantine (New Rats – Post Infection)

Quarantine is the singularly most effective tool we have to prevent and contain viral outbreaks.

• New Rats:
  Anytime there are new rats coming into a colony there must be a strict isolation period. Generally, 3 weeks at a separate location where there are no rats is considered safer than the standard 2-week quarantine. A two–week quarantine should be fine if you are isolating a single rat. A group of new rats require a longer time period. If the quarantined rat(s) becomes ill, then there must be a new quarantine put into effect that begins when the rat is no longer showing symptoms.

  During this time any visitations to your quarantined rat(s) must be followed by waiting at least 3 hours before returning to your main colony. Sanitizing your hands, blowing your nose, and washing your clothes will minimize the risk of infection.
  
  Being airborne, an in-home quarantine is not effective for a virus.

• Post Infection Quarantine:
  For a single rat the post infection quarantine is at least 2 weeks after the rat is completely recovered. For a larger group it is recommended that the quarantine be 6–8 weeks. In a breeding colony the 6–8-week quarantine, begins after any weaned babies have ceased to be symptomatic, should be sufficient as long as no litters are born. Generally, 8 weeks is considered the minimal post infection breeding colony quarantine.

High Risk Scenarios

• Rat-inclusive events (shows, swaps, meetings)
• Acquiring rats from multiple sources at once
• Letting people visit with rats
• People visiting after contact with other rats
• Bringing in rescues
• Acquiring rats from pet stores
• Handling rats at pet stores or other colonies
• Visiting pet stores and returning straight home
• Allowing exposure to wild rats (House pet rats indoors)
• Rescuing rats and other animals
• Breeding during quarantine

SDA Virus and Breeding

The breeder has a special responsibility to the rat community. A breeder with a viral infection can spread the disease like wildfire and have a deadly impact on local fanciers.

A breeding colony that has a viral infection MUST be completely shut down. Once it has recovered the breeder must observe a full post infection-quarantine.

A full post-infection quarantine consists of absolutely no rats in or out (including no litters born). The length of the quarantine varies anywhere from 2–4 months after the last signs of illness or the last babies are weaned and symptom free. It is highly important that NO new litters be bred during this time. Viral infections can literally be perpetuated forever if litters are continuously breed during & after an outbreak. When this happens, you can have a situation where the SDAV becomes enzootic.

The breeder has a responsibility to make others aware of the outbreak. In case of exposure and to keep the diseases contained immediately alert other rat keepers and breeders to the possibility of contamination in the area. To reduce the risk of an outbreak it is recommended that new clients NOT visit the rattery. A closed rattery is less likely to contract or transmit disease. All ratteries, even closed ratteries, should practice a quarantine time each year for several months (no new rats and NO breeding) to ensure a virus free population.

SDA Virus & Rat Rescue

Groups or individuals that perform rat rescue are at a particularly high risk for viral contagion. It is recommended that there be a separate building (no shared air) or location for the intake of new rescues and that there be a proper quarantine before rescued rats are placed in their foster or permanent homes.

Due to the extremely high risk of viral infection groups or individuals that perform rat rescue services should NOT breed their rats unless the strictest of quarantine procedures are followed. It is also a good practice to limit your rescuing to one species.

Tracking the SDAV Virus

The RMCA has created a database for tracking viral outbreaks. To view when and
where outbreaks have occurred visit https://www.rmca.org/Data/

There you will also find a form for reporting your own viral outbreaks. By honestly entering information to this database people will become more aware of the dangers and it will provide the rat community with the necessary data to help in the prevention of viral outbreaks.

Resources

1. Barthold, S., & Percy, D. (2001). Pathology of Laboratory Rodents and Rabbits, Second Edition. Ames, Iowa: Iowa State Press.
2. Biology of the Rat. (n.d.). Retrieved December 23, 2008, from http://www.lvma.org/rat.html.
3. Charles River Laboratories. (1983). Rat coronaviruses. CLR Technical Bulletin, 2(2). Retrieved December 23, 2008, from http://info.criver.com/flex_content_area/documents/rm_rm_r_rat_coronaviruses.pdf.
4. Charles River Laboratories. (1991). Serologic Testing of Rodents for Viral Infections: Interpretation of Results. CLR Technical Bulletin. Retrieved December 23, 2008, from https://www.criver.com/SiteCollectionDocuments/rm_rm_r_serologic_test_rodents_viral_infect.pdf.
5. Common Rodent Pathogens That Can Compromise Your Research. (2003, January 10). Retrieved December 23, 2008, from https://www.utexas.edu/research/arc/misc/viruses.htm.