A third elephant at the Oregon Zoo may have tuberculosis.

According to zoo officials, Tusko, a 44-year-old male Asian elephant, has tested positive for TB on one test and negative on another. Zoo veterinarians and elephant-care staff are pursuing further testing to better understand the contradictory results.

Test results received last week from Tusko’s trunk culture indicated the presence of mycobacterium, an organism known to cause tuberculosis. But on Monday, 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.”

Two other elephants, Packy and Rama, tested positive for TB last year. They continue to show no signs of illness, according to zoo veterinarian Tim Storms.

The zoo’s four female elephants and the 5-year-old male Samudra have all tested negative.

Packy turned 52 in April. According to zoo officials, 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, Packy dropped 1,400 pounds, bringing him down to 11,000 pounds. That's not the lowest he’s ever weighed during musth, zoo officials say, but concerning enough that keepers had to be creative to get him to eat, starting with feeding him sweet potatoes — a treat Packy usually enjoys whole — cut into little pieces.

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 as he ages.

“At Packy’s age, it’s natural for us to be concerned by every setback,” Lee says. “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.”

Rama, a 31-year-old Asian elephant, was diagnosed with TB last May, is now halfway through his 18-month regimen and continuing to progress well, zoo official say. 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 says. “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.”

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