A veteran snake handler remained in serious but stable condition Monday at University Hospital after being bitten by a deadly Pakistani pit viper last Wednesday.

William E. Haast, 78, director of Miami Serpentarium Laboratories, admitted himself to the hospital Thursday, almost 24 hours after the incident when he determined he was not immune to the snake's venom.Haast has been bitten 148 times and has routinely inoculated himself with antivenins over a period of years to develop immunities to most snake venoms.

A hospital nursing supervisor said antivenin has been received from Iran, the Soviet Union and from the United Kingdom but is being withheld while doctors evaluate Haast's progress.

Antivenin had to be flown in from San Diego and Los Angeles for Haast's initial treatment, after it was determined he was allergic to the antivenin available at the hospital. The nursing supervisor said the venom's effects last up to 23 days, and hospital officials will keep the new shipments of antivenin on hand until doctors determine Haast is out of danger.