This disease shall be granted service connection as a result of tropical service, although not otherwise established as incurred in service if manifested to a compensable degree within the applicable time limits under §3.307 or §3.308 following service in a period of war or following peacetime service provided the rebuttable presumption provisions of §3.307 are also satisfied [38 CFR 3.309 (b) Disease subject to presumptive service connection].