The Texas Supreme Court handed property owners a major victory on an issue of increasing importance as West Nile Virus and Zika Virus spread around the country. The court held that the doctrine of ferae naturae limits a property owner’s liability for harm from indigenous wild animals that the property owner has not attracted to its property. As a result, the court dismissed the claims of a worker who asserted that the property owner should have protected him from mosquito bites that infected him with West Nile Virus.

The plaintiff, William Nami, a long-time worker for Union Pacific Railroad, worked in a part of southeast Texas that is well-known for mosquitos, with one town even boasting that it is the “mosquito capital of the world.” Union Pacific issued various bulletins and other warnings about mosquitos.

While Nami operated a piece of equipment, a tamper, the tamper’s cab failed to seal properly, and Nami was bitten regularly by mosquitos. After unsuccessfully complaining to his superiors to change these conditions, Nami ultimately developed flu-like symptoms and was diagnosed with West Nile Virus. He sued Union Pacific under the Federal Employers’ Liability Act (FELA), which is generally based on common law negligence principles.

At trial, the jury attributed fault to both Union Pacific (80 percent) and Nami (20 percent). Nami was awarded $752,000.00 in damages. On appeal, Union Pacific argued that it owed Nami no legal duty to protect him from mosquitoes pursuant to the doctrine of ferae naturae. The intermediate court of appeals held that even if the doctrine applied, which it did not decide, Union Pacific was still liable for negligence because it created the conditions that attracted mosquitos to Nami’s worksite.

In an 8-1 decision, Texas Supreme Court reversed and rendered in favor of Union Pacific. After a brief discussion of how common law generally guides the application of FELA, the court explained that the common law governing responsibility for actions of animals divides animals into tame, domestic animals (domitae naturae) and wild animals (ferae naturae). Mosquitos are classified as wild animals.

The court held that a property owner is generally not liable for harm caused by wild animals on the owner’s property. The court explained that, under the doctrine of ferae naturae, a property owner is not liable for the acts of wild animals against an invitee unless the property owner reduces the animals to his possession, attracts animals to the property, or knows of an unreasonable risk and neither mitigates the risk nor warns the invitee. The court observed that Union Pacific had done nothing to attract or take possession of the mosquitos that are a well-known, indigenous pest throughout that part of the state.

Texas and other states are now tracking the spread of West Nile Virus and Zika Virus on a daily basis.