Twenty-three dead and dying Brazilian free-tailed bats from roosts in downtown Mineral Wells, Palo Pinto County, Texas, were tested for rabies and for anticholinesterase (antiChE) effects of or- ganophosphorus (OP) and carbamate pesticides. Seventeen of the 23 bats tested positive for rabies. The cause of death or dying in five of the nonrabid bats is unknown; however, one of the six nonrabid bats had a ChE activity level equivalent to only 27% of the control mean and may have been exposed to a pes- ticide. Three bats (including the bat with depressed ChE) contained sufficient ingesta to analyze for an- tiChE compounds, but no antiChE compounds could be identified in the samples. Exposure may be dermal and pulmonary as well as dietary. It is feasible that other bat deaths not explained by rabies were attributable to a pesticide but missed due to postmortem reactivation of the ChE enzyme. The largest group of rabid bats was young males (13 of 17, 76.5%), and the largest group of nonrabid bats was older females (3 of 6, 50%). All older females were nonrabid, perhaps survivors of the disease in previous years. Rabid bats had a lower mean fat index and weighed less than nonrabid bats. Four bats (not includ- ing the low ChE bat) showed external bleeding, and none was rabid; thus the incidence of bleeding was greater among nonrabid bats than among rabid bats. The four affected bats came from roosts in three different buildings, making a roost-treatment with an anticoagulant chemical seem unlikely.
