Whether or not you want to believe it, there are circumstances in which your dog would bite someone. Even if your dog patiently suffers all sorts of indignities without protest (children pulling its tail, having its toenails clipped), if a dog is frightened, threatened, or hurt enough, it will bite.
The law presumes that veterinarians know this, even if not all owners do. Courts have ruled that because veterinarians knowingly take the risk of injury as part of the job, and should know from experience how to guard against it, they can't sue an owner if they are injured while handling a dog. As one court put it, "a veterinarian cannot assume a normally gentle dog will act gently while receiving treatment." (Nelson v. Hall, 165 Cal. App. 3d 709, 211 Cal. Rptr. 668 (1985).)
The same rule generally applies to veterinary assistants and others who knowingly take the risk of handling animals in the course of their jobs. A veterinarian's employee might, however, be able to sue a vet who exposes the employee to an unnecessary risk.
Of course, there may be exceptions to this rule. If, for example, a dog was known to be dangerous, but its owner concealed that from the vet, the law might hold the owner responsible if the dog injures the vet. (See Willenberg v. Superior Court, 185 Cal. App. 3d 185, 229 Cal. Rptr. 625 (1986).)
Even dog-bite statutes, which make owners liable for any injury their dog causes, don't usually apply when veterinarians are injured. Courts follow different logical paths to arrive at this conclusion. Some say that because veterinarians take dogs under their control, they themselves are "owners" under the statutes that make owners liable. 4 Other courts say that a veterinarian, by treating a dog, provokes it to bite; provocation is a defense under most dog-bite statutes. (For example, see Mulcahy v. Damron, 168 Ariz. 11, 816 P.2d 270 (Ariz. App. 1991).)
Provocation doesn't have to be deliberate or cruel; it can be completely innocent, as when you accidentally step on a dog's tail. A Florida appeals court, overturning a $25,000 jury verdict awarded a veterinarian's assistant, said that the conditions under which a dog had been treated—"in strange surroundings ... held by two people he had never seen"—constituted provocation. The court concluded that the legislature had not intended that a dog owner should have to pay for injuries under such circumstances. (Wendland v. Akers, 356 So. 2d 368 (Fla. App. 1978).)