Zoo to re-test elephant Tusko after inconclusive TB results

June 3, 2014 - 2:58pm

Vets formulating new plan to combat Packy's TB; Rama continues to progress well

Tusko, a 44-year-old male Asian elephant at the Oregon Zoo, has tested positive for tuberculosis on one test and negative on another, zoo officials learned today. Zoo veterinarians and elephant-care staff are pursuing further testing to help explain the contradictory results.

TB has been reported in elephants as far back as 1875 and has a history of successful treatment. The zoo routinely tests all its elephants for the disease by taking a trunk culture (collecting fluid from the animal's trunk and sending it to a certified laboratory for testing) as part of its comprehensive health program and in compliance with U.S. Department of Agriculture standards.

Last week, results received from Tusko's March trunk culture indicated the presence of mycobacterium, an organism known to cause tuberculosis. Today, however, a standard follow-up test known as MAPIA (multi-antigen print immunoassay) showed Tusko had not produced the antibodies that typically indicate the presence of TB.

"The results are puzzling," said Bob Lee, the zoo's elephant curator. "Tusko appears to be in fine health and is acting normally. But we want to take every precaution and get to the bottom of this. We've asked the lab to re-run the MAPIA testing. And all the bull elephants had their regularly scheduled trunk washes just this morning, so we'll be submitting those for culturing as well."

The zoo's four female elephants and the 5-year-old male Samudra have all tested negative. Packy and Rama, who tested positive for TB last year, continue to show no signs of illness, according to zoo veterinarian Tim Storms.

"What we've seen to this point is referred to as asymptomatic shedding," Storms said. "We've observed no signs of illness in any of the elephants. Our focus remains on successfully completing Rama's treatment regimen, and finding a plan that works for Packy, while we work to learn more about Tusko."

Rama, diagnosed with TB last May, is now halfway through his 18-month regimen and continuing to progress well. He is no longer actively shedding, according to Storms. Treating Packy — the oldest male Asian elephant in North America — has been more challenging, in part due to his advanced age.

"The effects of these medications can be very different from one patient to another," Storms said. "You see the same thing with human patients, and in fact the medications we're using are the same ones used in human TB cases. Packy seems to be more sensitive to one of the drugs, so we're working to come up with a different regimen."

Zoo animal-care staff first tried treating Packy last August, but that coincided with his entering musth — a period of heightened aggression in bull elephants, marked by soaring testosterone levels and a loss of appetite. Treatment was halted soon after it began. Subsequent attempts also stopped short when Packy's medications caused him to experience a loss of appetite.

The most recent setback occurred in late April. The zoo's vet staff recalibrated Packy's TB regimen and resumed treatment, and the geriatric elephant again lost his appetite. This time though, when the treatments stopped, Packy didn't resume eating. He had once again entered musth, and it was the most pronounced bout his keepers had seen in years. In a span of two weeks, the geriatric pachyderm dropped 1,400 pounds, bringing him down to 11,000 — not the lowest he's ever weighed during musth, but concerning enough that keepers had to be creative to get him to eat.

Senior elephant keeper Shawn Finnell tried cutting sweet potatoes — a treat Packy usually enjoys whole — into little pieces. Once that worked, Finnell and the other keepers started shoveling sweet potato bits to Packy as fast as he would take them, gradually working up to alfalfa and then hay. Around the same time, Packy's testosterone levels dropped again, indicating he was coming out of musth.

Packy has since regained most of his weight — he was up to 12,105 pounds at Friday's weigh-in, well within range of his normal 12,200-pound goal. Keepers plan to bring him above that goal weight, up to about 13,000 pounds, before resuming his medical regimen to help ensure Packy better can handle the treatments. Vets will closely monitor Packy's liver and kidney functions as well, adjust his treatment as necessary, and do everything they can to keep Packy comfortable in the twilight of his life.

"At Packy's age, it's natural for us to be concerned by every setback," Lee said. "We're just thankful for every day he's with us. At this point, everything about his life is teaching our keepers and vets about geriatric care. Nobody knows what happens when a male Asian elephant reaches this age — we're in uncharted waters here, just as we were at the time of Packy's birth."