PLAN FOR ERADICATION: Rollins
& Dental
Time Table
March 23, 2000: Deadline for ordering rats for the next
five weeks.
March 28, 2000: Moratorium on adding new rats to Rollins
animal research facility colonies by purchase, transfer from another
investigator, or breeding colony births.
March 28,2000: Tentative start of deliberate SDAV infection
campaign. Inoculation of rats with SDAV live virus, strain 681.
May 2, 2000: Tentative end of the moratorium. Return to
business as usual.
This plan was approved by
the DAR faculty advisory
committee on March 16, 2000.
Moratorium Exceptions
Investigators acquiring animals for acute use may continue to
order animals or maintain standing orders for rats under one of
the following conditions:
Use within 24 hours of delivery from the vendor: Rats will not
be uncrated and housed in the animal research facility, but will
be kept in the original shipping crate for subsequent delivery
to the laboratory.
Use after 24 hours of delivery: Such rats will be housed at a
remote site and will be delivered on a scheduled, as-need-basis
to laboratories for immediate terminal use.
Investigators wishing to be exempted from the moratorium and
abiding by the conditions above should contact Michelle in the
DAR office (7-8395).
Special Procedures
All rats in the Rollins Center and Dental School are under quarantine
and will be so until at least May 2, 2000. This means that investigators,
research personnel, and DAR staff should not cycle through other
buildings after being in the Rollins Center and should schedule
Rollins activities last in any day before going home. It goes
without saying that rats should not be moved from building-to-building.
History
An outbreak of sialodacryoadenitis virus (SDAV, coronavirus)
was diagnosed in the Rollins Research Center animal research facility
on February 29, 2000 based upon clinical signs and was subsequently
confirmed by seroconversion. The epizootic appeared to be the
consequence of an outbreak that occurred at Harlan Sprague-Dawley
production sites and disseminated nationally (www.harlan.com)
in late January.
Frequently Asked Questions (FAQs)
What is SDAV? SDAV is highly infectious and spreads rapidly
by aerosol. It is rarely lethal and is self-limiting. Suckling
and weanling rats are most at risk of developing severe clinical
disease. Rats will recover from disease and develop immunity.
Providing new susceptible animals are not added to the population
through breeding or purchase, infection will eventually run its
course. This is the rationale for a moratorium. It takes 3-5 weeks
for infection to spread completely through a large animal research
facility providing barrier caging systems are not used. The incubation
period from exposure until virus shedding is generally less than
a week and often as short as 2 days. Acute clinical signs are
seen about 7 days post-exposure and infected animals shed infective
virus for only about 7 days. The virus is short-lived in the environment
lasting only 2-3 days in areas of contamination.
What are the clinical signs of infection? Typically, infection
with SDAV is characterized by ocular squinting or bulging eyes,
corneal ulcerations, mild pneumonia, nasal and ocular discharges,
sneezing and often spectacular “mumps-like” swelling
of salivary glands in the neck. Rats may also show cyanosis or
respiratory distress upon restraint. Previous outbreaks of SDAV
at Emory University were in 1994 and 1988. Because of general
malaise and pneumonia, SDAV-infected rats should be expected to
lose weight, perform abnormally in behavioral paradigms and are
at high risk of dying under anesthesia. Infection is generally
not fatal except in certain cases in suckling rats.
How long does it take to resolve infection in a single animal?
Clinical signs last about a week after which rats should begin
regaining weight and return to normal. However, ocular and microscopic
salivary gland lesions may take up to 6 weeks to resolve.
Are mice, humans or other species at risk of infection?
SDAV is a virus disease specific for rats. No other species are
at risk.
What if we do not do anything and decide to coexist with infection?
If we fail to take action, the virus will become enzootic in our
colonies. This means that many animals will be immune, but some
animals will always be infected and shedding virus. Suckling rats,
protected by maternal antibody, will become infected after weaning.
Naive rats newly acquired from vendors will become infected sometime
after arrival. Infection will always be smoldering and pockets
of animals will be infected introducing variability into behavioral
research, pulmonary studies, safety of anesthesia, and potentially
confounding reproduction.
Is there a protective vaccine? There is no vaccine against
SDAV; infection is the only means to confer immunity. Rats acquired
from commercial vendors have not been exposed to SDAV, are not
immune, and are at great risk of clinical disease.
What is the purpose of deliberate virus infection? The
key to terminating infection is to create a “fire wall”
against infection by creating immunity in all rats. This is done
by placing a moratorium on new acquisitions, building-up an inventory
of rats for research, and actively infecting all of these rats
with live virus. Simultaneous infection reduces the 3-5 week period
necessary for natural spread of the virus to 7-10 days. We used
this strategy successfully in 1994 to halt a similar outbreak.
Are there any other management options? Other options
are to depopulate all rats (an unpalatable consideration) or to
enarct a moratorium and let natural infection take its course.
The latter requires 6-8 weeks (1-3 weeks longer than our plan)
and, with our increasing use of ventilated caging systems, there
is no guarantee that we will have effective transmission to all
rats.
What complications can be expected for research? Rats
should not be anesthetized for the first 10-14 days after infection
due to impaired pulmonary physiology. Behavioral studies will
also be confounded by clinical illness and for some period during
convalescence. Studies involving the eyes, salivary glands, olfactory
system or lungs are obviously at risk for up to 6 weeks post-infection.
Breeding colonies may show reduced reproduction and poor growth
of sucklings and weanlings. Pulmonary macrophages will have inhibited
phagocytosis and interleukin-1 production. Not all projects may
be affected in these adverse ways. Many rats already on hand have
probably recovered from SDAV infection and should be immune to
further clinical involvement.
