Dr. Vichazelhu Iralu, 60, chairman of the department of microbiology at the Philadelphia College of Osteopathic Medicine, died Thursday,  September 14, 1984 at this home in Malvern.  A native of Nagaland, India, he did his undergrad work at Presidency College in Calcutta and earned his master’s in public health and his doctorate in medical parasitology at the University of North Carolina.  From 1967 to 1974,  he was assistant chief of the microbiology department at the William Pepper Laboratory of the Hospital of the University of Pennsylvania and assistant professor of pathology at Penn’s medical school.