A small lab at OSU is a critical component of the state’s complex system that protects the public from rabies.
Wendy Black has been testing brain tissue, looking for rabies infection, for twenty-six years. She and fellow technicians process about 80 samples every week. They work for the Oregon Veterinary Diagnostic Laboratory (OVDL), the only lab in the state that does rabies testing.
The laboratory space for rabies testing resides in a seventy-year-old building on the western edge of the OSU campus. The faded, old linoleum on the floors is in stark contrast to state-of-the-art equipment set up throughout the building. Most of the rooms contain automated processers conducting sophisticated diagnostic testing, but the rabies lab follows a Center for Disease Control (CDC) protocol that has been the standard for decades, and it’s all done by hand.
When a dead bat comes into the OVDL, the first thing Wendy does is remove its brain. “We separate the cerebellum and brain stem; that’s where the concentration of rabies will be found.”
Wendy prepares a slice of brain tissue by fixing it to a slide then treating it with two different kinds of rabies antibodies. “Essentially, we have two different agents looking for the same thing,” she says. This is one of many steps they take to ensure accurate diagnosis.
The slide sits for thirty minutes, letting the animal tissue and antibodies incubate together, then Wendy uses a microscope to view the result. She looks at forty different tiny sections, searching for a grouping of bright green spots called ‘green apple granules’, the evidence of rabies. Her colleague duplicates the process with the same brain tissue to make sure they are not missing a low-level infection. There is absolutely no automation involved; it’s just people working efficiently, and time is a factor. “From the time of receipt to the time of reporting, we can usually get it done in 2-3 hours,” says Wendy. “We want no more than a 24-hour turn around, for peace of mind of the clients.”
Most rabies testing at the OVDL is done on dead bats (only about 30% is done on larger animals) and most of those bats come from the general public. When a slide tests positive for rabies, the OVDL contacts the state veterinarian at the Oregon Health Authority, who notifies the county where the animal resided. He may also question the person who found the animal to determine if anyone was exposed and needs treatment, a process that involves many weeks of shots.
When a slide tests negative for rabies, Wendy quickly contacts the person who submitted the bat. “I like to call them personally with the negative result,” she says. “They might be worried about exposure to their pets and family, and it is nice to hear the sigh of relief in their voice.”
In cases where a dog or cat brings home a dead bat, or when a veterinarian suspects a pet’s neurological symptoms may be due to rabies, there is only one sad, stressful way to diagnose the disease: euthanize the animal and remove its brain. However, the CDC has recently developed a promising, new rabies test that uses tiny DNA samples instead of brain tissue. “It will be very sensitive,” says Wendy, “And the neat thing is they can use it on different kinds of samples, like saliva, so the animal would not have to be euthanized.”
