A pneumonia epidemic that has killed more than 100 bighorn sheep in the nearby Mojave National Preserve this summer, and is decimating another herd, may have come from sick animals illegally dumped off a truck en route to alfalfa fields in the Imperial Valley. Tuesday, Federal land managers said scientists are investigating two areas plagued by disease. The first, at Old Dad Mountain, 15 miles southeast of Baker where experts estimate that half of the 200- to 300-sheep herd died since mid-May and at nearby Kelso Peak. Last month, several sick bighorn sheep were found 35 miles to the south in the Marble Mountains, just south of Interstate 40 and east of Kelbaker Road. Tests showed they suffered the same strain of pneumonia found in bighorn at Old Dad Mountain and Kelso Peak. Linda Slater, spokeswoman for the 1.6 million-acre preserve. Said, “They’re seeing a lot of sick sheep, so they’re expecting a lot of sheep to die in the next couple weeks in the Marble Mountains. It happened pretty quick at Old Dad, within a month.” The majestic bighorn, icons of the American West, are highly susceptible to pneumonia carried by domestic sheep and goats. Bighorn have no immunity to the disease, which is almost always fatal.