By Rebecca Phillips
Washington Animal Disease Diagnostic Laboratory at WSU
Hundreds of people, cats, dogs, porpoises, birds, and other animals on Vancouver Island, British Columbia, fell victim to what was diagnosed as a rare fungal infection called Cryptococcus gattii. Though physicians and veterinarians were familiar with the more common Cryptococcus neoformans, C. gattii was considered a tropical disease found only in places like Australia.
Upon deeper investigation, B.C. health officials were alarmed to discover that C. gattiihad established itself in the native trees and soil—and was especially prevalent in decaying wood. Epidemiologists speculate that climate change and warmer summers helped create favorable habitat for the organism.
While C. neoformans primarily attacks those with weakened immunity, C. gattii is more virulent, infecting both healthy and sick alike. Worse yet, the yeast-like microorganism is often resistant to standard fungal medications.
Kulshan Veterinary Hospital, Lynden, Washington It had been a routine day for veterinarian Dorrie Jordan when she was presented with a sick cat, Boots. Jordan’s exam revealed a large tumor in Boots’ abdomen. With a poor prognosis, the cat was euthanized and the tumor, which Jordan described as “a weird yellow color,” was sent to WADDL for expert diagnosis.
Not long after, another cat, Nutmeg, arrived at the clinic with a swollen neck. Jordan removed a small sample. Her technician examined it under a microscope and reported “a strange organism.” Jordan also sent that biopsy to WADDL.
WADDL, Pullman, Washington When WADDL executive director Timothy Baszler and his colleagues received Jordan’s biopsy samples, the lead pathologist ordered a typical histological exam of the tissue. The microscope revealed severe inflammation and budding yeasts. The verdict: Cryptococcus neoformans species. They informed Jordan, who began treating Nutmeg with an antifungal drug.
WADDL, Pullman, Washington Jordan’s preserved samples were transferred to the molecular diagnostic lab managed by Daniel Bradway. Using a pioneering technique, Bradway extracted DNA from the fungus and sequenced its genome. With great surprise, he found it was Cryptococcus neoformans subspecies gattii VGII—the same organism responsible for the Vancouver Island outbreak. It was the “index case,” the first occurrence of the disease in the United States.
WADDL Emerging Infections Surveillance Team Veterinarian Margaret Davis DVM ’85 scrambled to learn everything she could about C. gattii. She coordinated with the Washington State Department of Health (DOH) to alert veterinarians that C. gattii is contracted by inhaling fungal spores and usually causes neurological, skin, or respiratory symptoms. Vehicles, camping equipment, and birds are possible modes of spreading the infection. Animals, especially curious cats, are often the first to pick up a new disease.
Washington State DOH, Olympia, Washington Public health veterinarian Ron Wohrle DVM ’77 had followed the emergence of C. gattii in British Columbia. As it spread to Washington, he and WADDL developed a surveillance system for tracking the disease. The team mapped each new case of the infection, carefully noting range and habitat. They also conducted an extensive environmental search for the fungus, sampling air, trees, and soil. No areas of permanent colonization were detected. The health department added C. gattii to the state’s list of reportable diseases for veterinarians and human health care providers.
Centers for Disease Control and Prevention, Atlanta, Georgia Wohrle received funding to establish a national surveillance program with the Centers for Disease Control Mycotic Diseases Branch. CDC was notified of all C. gattii cases identified by WADDL.
Oak Creek Wildlife Area, Yakima, Washington
Washington Department of Fish and Wildlife veterinarian Kristen Mansfield received an unusual report of a calf elk seen stumbling at the Yakima winter feeding grounds. In samples sent to WADDL, a pathologist found yellow masses in the brain and diagnosed fungal meningitis caused by a Cryptococcus species. Samples were sent to the molecular diagnostic lab and also to Wohrle who routed them to the CDC. Both labs confirmed C. gattii VGII. It was the first documented case in eastern Washington.
Valley Veterinary Clinic, Twisp, Washington
Veterinarian Teresa DeWeert battled a stubborn mouth infection in a cat, Biskit. When antibiotics didn’t help, DeWeert sent a biopsy to WADDL. The diagnosis came back C. gattii and the pathologist advised caution for all those in contact with and sharing the environment with Biskit.
The key word is environment as Baszler says it is very unlikely that humans can “catch” C. gattii from pets. Rather, infected cats and other animals act like sentinelswarning their owners that the fungus could be in their yard.
DeWeert later discovered two more infected cats—all three cases falling far outside the predicted niche.
State of the outbreak
Since 2008, 30 people and 59 animals have been diagnosed with C. gattii in Washington, with many more cases likely unreported, says Wohrle. Is the fungus spreading or has it been here all along? These and other questions remain.
Since first isolating C. gattii in 2005, WADDL has refined and expanded the capabilities of the molecular diagnostic lab. Today, pathologists from across the nation routinely send samples to WSU for DNA sequencing, not only to identify fungus, but also thousands of other organisms including bacteria, viruses, protozoa, and chlamydia.
Baszler says WADDL staff members pay close attention to the details of every sample they receive, to help protect the public.
“You never know what kind of problem is going to come through the door,” he says. “Something as simple as a bump on a cat’s head might turn out to be a public health threat.”
Postscript: All cats, except Boots, recovered completely. Pet names have been changed for owner privacy.