HOUSTON — Saron Wyatt pointed to the secluded end of her small street in Houston’s impoverished Fifth Ward, where a mound of old tires keeps popping up.

Always a trashy nuisance, it’s now a growing danger. Tires collect water and become prime breeding grounds for mosquitoes — especially the ones that spread Zika virus disease and other tropical mosquito-borne illnesses.

Wyatt, a mother of five, doesn’t know where the tires are coming from. But she’s worried about it, and so are health officials.

Spraying for the type of mosquito that carries Zika is not always effective, and they can breed in pools of standing water as small as a Styrofoam cup. That means vacant lots or messy yards may need to be cleaned up, whether the owner of the mess wants it cleaned or not.

Dr. Umair Shah, the head of Houston’s county health department, called getting the cooperation of local residents has department’s biggest issue. “It’s really about a neighbor who might have sources of breeding on their property that can impact a neighbor two or three houses down,” he said.

Experts believe the vast majority of neighbors will comply. But not all. For months now, the federal government has been urging local health officials to review local nuisance ordinances and plot how to handle property owners who are combative or can’t be found.

During a recent outbreak of dengue fever in Hawaii that involved the same mosquito that can spread Zika, health officials went to more than 500 properties to survey or spray. In 23 cases, residents refused requests to enter.

It happened again in March, when health officials went to see a Kauai resident who was infected with Zika after traveling to an outbreak area in Latin America.