The Board is hereby authorized to contribute annually to any mosquito control commission a sum not more than 25 percent of the gross amount obtained by such commission annually from any special tax levy authorized by this article or contributed to such commission annually by direct appropriation of any county, city, town or combination thereof, but any such amount so contributed by the Board shall not exceed $10,000 in any 1 year; except that where separate mosquito control commissions have been consolidated pursuant to § 32.1-188, such maximum amount shall be computed so as to allow a contribution to that consolidated district in an amount not less than was received prior to such consolidation by all of the separate districts.