The West Nile virus vaccine that is manufactured by Fort Dodge Animal Health may be causing abortions in pregnant mares and deformities in foals, according to an article that appeared Friday on the Denver Post Web site. The article said the problems had been reported by a number of Midwest ranchers who raise Quarter Horses.According to the Post, the ranchers, who call themselves the Lost Foals Group, successfully lobbied Fort Dodge to issue a statement on its Web site to reflect their concerns. Drafted by attorneys representing the company, the statement reads: "A low number of undiagnosed abortions have been reported from the field following use (of the vaccine). These reports appear to be associated with individual animal responses from the vaccine or due to stress, which may occur with any vaccine administered to pregnant animals."Dr. John Tuttle, Fort Dodge's manager of professional services, told the Post that the company had investigated each problem pregnancy report. He said the rate of spontaneous abortions was 3.3 for every million doses of the vaccine sold, or approximately two dozen nationwide. The numbers, he said, do not point to a larger, more worrisome trend.Chuck McDaniel, who is handling the complaints about the vaccine for the U.S. Department of Agriculture (USDA), told the Post he did not know what, if any action, the organization would take. If it has serious concerns about safety, the USDA could launch a formal investigation and order Fort Dodge to stop selling the vaccine and recall doses.