The pathogen of pebrine is transmitted to a host either vertically or horizontally. Vertical transmission may arise in two distinct ways depending upon whether the passage of the pathogen occurs on the surface of the egg or within the ovary of the mother moth. Horizontal transmission occurs only in the larval stage. The most frequent source of infection in this stage is that which occurs when feces from infected larvae contaminate the food and are thus ingested by healthy larvae in the same colony. Sanitation and disease-free stock are the principal strategies of pebrine prevention.