LAS VEGAS (AP) — Wildlife officials say a recent count found more wild desert bighorn lambs this year than last year in the River Mountains of southern Nevada.

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But the herd is still struggling with an outbreak of bacterial pneumonia that researchers say the animals have no natural way to fight.

Nevada Department of Wildlife biologist Pat Cummings tells the Las Vegas Review-Journal that an aerial tally in October counted 15 lambs per 100 ewes in the rugged area between Henderson and Boulder City.

That's more than twice the six-lambs-per-100 ewes found in 2015.

But it's still well below the average of about 33 lambs for every 100 ewes researchers say they find in normal years.

Wildlife officials have been trying since 2012 to stop the pneumonia outbreak in area bighorns.