UC-Davis mounts investigation of rare calicivirus

Los Angeles-A virulent, hemorrhagic strain of calicivirus ran through several practices in the L.A.-area like a brushfire and disappeared almost as quickly.

Close to 50 cats fell victim to the outbreak from early July to earlyAugust, and about one-half of those died as a result. The outbreak was tracedto three veterinary practices in the area, and has opened up a new inquiryabout this rare strain of calicivirus (FCV-Ari) at the University of California-Davis.Researchers want answers.

Dr. Kate F. Hurley, resident DVM at the Maddie's Shelter Medicine Programat UC-Davis' Center for Companion Animal Health, reports that by the timeone practice identified this hemorrhagic strain, it had already swept throughthe entire hospital. In one hospital alone about 20 cats died from the viralstrain. Drs. Janet Foley, Mike Bannasch and Hurley were running the scientificinvestigation.

The majority of the cats confirmed with the virus were also vaccinated,Hurley adds. The virus is believed to have originated in a rescue cat.

Presentation of FCV-Ari is different from field strain calicivirus, Hurleyexplains. Unique characteristics include facial, limb and generalized edema.Some cases have shown elevated bilirubin and some cats have become jaundiced.The mutant strains also cause a hemorrhagic-like fever in cats. Like theregular field strain of calicivirus, oral ulcerations were common with thisstrain as well as oral and nasal discharge. (See Table 1.)

Cats with mild signs recover within a few days, while cats with a severecase often die in spite of extensive symptomatic treatment.

Hurley says, "It is very different from what we usually expect frominfectious diseases, targeting sick or weakened animals. If you have a big,robust and healthy cat that comes in contact with a little virus, it isusually not that big of a deal. Not with this."

Hurley adds that the virus can be transmitted very easily. In one case,the virus was believed to have been carried home on a veterinary technician'sclothing and infected her cats.

FCV-Ari was first identified by Dr. Niels Pedersen, an infectious diseaseexpert and director of the Center for Companion Animal Health at UC-Davis.Different outbreaks have spurred research ongoing at the University of Tennesseeand Cornell University. This is believed to be the largest single outbreakever reported.

UC-Davis researchers are conducting several different follow-up investigationson the outbreak, including genetic sequencing from samples of affected catsand follow-up viral cultures on some of the recovered cats to understandhow long the virus is infectious. Detailed pathology, immunohistochemistry,detailed necropsies and electron microscopy work is also under way to understandthe virus in infected tissue.

Hurley explains that from their work with necropsies, they have foundlesions in the GI tract, liver, spleen, pancreas and lungs. But these lesionsare not found consistently in these organs.

"In some cases, the liver was trashed, in other cases the liverswere relatively unaffected but there were horrible ulcers in the GI tract,"Hurley says.

Researchers want to know why.

Good news

The good news is the virus strain is self-limiting; in other words, itdies off fast. But when this virus is hot, it is tough to inactivate.

The virus can be shed in feces and in nasal, ocular and oral secretions.

"The virus can be very readily spread by fomites as well as directtransmission. It can be carried for at least several hours on contaminatedhands, clothing, instrument, shoes, etc.," the university reports.

Droplet transmission is possible over 1-2 meters, while calicivirus canbe carried through ventilation systems on dust and hair, airborne transmissionover distances greater than a few feet has not been documented, the universityadds.

How to kill it

Detergents alone won't kill it either.

"Standard hygienic practices that clinics employ may not be adequateto control this virus," Hurley explains.

When faced with an outbreak like this, bleach (5 percent diluted 1:32)is the most reliable disinfectant. One clinic shut down its cat admissionsfor an entire week to disinfect the premises.

UC-Davis recommends that contaminated exam rooms should be scrubbed downwith the appropriate detergent and then disinfected with the bleach solution.If contamination is suspected, all surfaces should be thoroughly cleanedand disinfected, including offices and dog runs. The recommendation is tobe very thorough too, including disinfecting telephones, keyboards, doorknobsand other frequently handled items.

If it can't be cleaned, officials recommend a quarantine of one to twoweeks.

The university also makes these recommendations:

* Outpatient suspect cases (cats presenting with one or more ofthe signs described in Table 1) should be limited to one exam room, andprotective garments should be worn when examining suspect cases.

* Cats presenting with only signs of upper respiratory infection,fever and/or oral ulceration are unlikely to be infected with virulent calicivirus,particularly if there is no history of likely exposure.

* Cats presenting with additional findings of icterus or oozing/crustingsores on the face or feet should be considered at moderate risk.

* Cats presenting with fever and facial or limb edema and/or ahistory of exposure to a diagnosed case of virulent calicivirus should beconsidered at very high risk.

* Hospitalized suspect cases should be housed in strict isolation,with separate equipment, gowns, gloves, caps and protective footwear used.

* Contact with affected cats should be kept to the minimum necessaryto provide appropriate care, and should be limited to one or a few designatedstaff.

* Owner visits should be discouraged, and owners should wear protectivegarments when handling sick cats.