BUZZ-Pan American Silver Corp: TD Securities downgrade
** Canadian miner's U.S.-listed shares down 1.5 pct at $11.99 premarket
** TD Securities analysts downgrade stock to "hold" from "buy", citing recent decline in silver prices
** If silver prices do not rebound, company's balance sheet may erode quickly and its growth prospects may be muted, they say
** Cut price target to $15 from $19
** Up to Tuesday, silver prices shed 20.88 pct to average $17.74 an ounce over the last three months
** Up to Tuesday's close, Pan American Silver's Nasdaq-listed stock had risen about 4 pct this year
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