KATHMANDU, Nepal — Many survivors of Nepal’s most recent earthquake remain cut off by blocked roads in isolated villages, a U.N. official said Wednesday, after this Himalayan nation suffered through its second major quake in less than three weeks. The magnitude-7.3 earthquake shook the impoverished country Tuesday, killing at least 79 people and injuring more than 2,300, just as it was beginning to rebuild from a devastating April 25 earthquake. The most recent quake hit hardest in deeply rural parts of the Himalayan foothills, hammering many villages reached only by hiking trails and causing road-blocking landslides. “Damaged houses were further damaged or destroyed. Houses and schools…