Because of a new restriction designed to limit the cost of the state's private option, plans offered by UnitedHealth Group are available this year only to enrollees in 13 of the state's 75 counties, a spokesman for the state Department of Human Services said last week. Plans offered by the four other companies participating in the expanded Medicaid program are available to private-option enrollees statewide, just as they were last year, Human Services Department spokesman Amy Webb said.