Think you have a rodent problem, Tampa Bay? Here’s what to do.

How will I know if I have a rodent problem?

Listen for scratching behind your walls or in your ceiling. Look for rat or mice droppings in your attic or crawl space.

Roof rats are common here and are especially active when citrus trees offer fresh fruit, according to the University of Florida Institute of Food and Agricultural Sciences.

They slip into buildings through tiny cracks and holes. Roof rats grow to about a foot long and weigh less than a pound.

How do I stop an infestation?

The best way: Don’t let rats or mice into your home in the first place.

The U.S. Environmental Protection Agency says prevention should come before poison. Clean up easy messes like loose garbage and standing water. Rats may enter looking for a meal or drink.

Keep lids on your trash bins. Fill in cracks and holes in your walls. Pest control experts often recommend sealing all possible entrances into a house as part of treatment. It can cost hundreds of dollars.

To stand up to rats’ sharp teeth, the University of Florida encourages using tough materials like concrete and sheet metal for the repairs.

If rats are already inside, the EPA suggests a gradual approach with the most lethal rodenticides deployed as a last resort. Residents can put out traps near areas where they’ve seen or heard rats. The University of Florida recommends using raisins, grapes or nuts as bait and leaving the traps out for several days.

In some spots, like farms, it’s hard to entirely cut off rats from food and shelter, according to the EPA. The agency says rodenticides may work best in such scenarios.

If I have to use poisons, how do I do it safely?

Always read the instructions. Labels contain information about who should use rodenticides and when, where and how they should be used. It’s against the law to violate rules on a rat poison’s label.

Second-generation anticoagulants, which cause animals to bleed to death, are among the most potent. They include: brodifacoum, bromadiolone, difenacoum and difethialone.

Average homeowners generally shouldn’t use these chemicals on their own, the EPA says.

Another class of rodenticides, first-generation anticoagulants, are slightly less potent but still dangerous. They include: warfarin, chlorophacinone and diphacinone.

According to the National Pesticide Information Center, other types of rat poisons include:

• Bromethalin, which “stops the cells in the central nervous system from producing energy”
• Cholecalciferol, which causes animals to suffer from excess calcium in their blood
• Zinc phosphide, which turns into a toxic gas when mixed with stomach acid

University of Florida experts recommend keeping rodenticides out of reach of children and pets.

Around homes, the rodenticides should be placed inside bait stations to make it less likely that other animals (besides rats and mice) will reach them.

What happens when people are exposed to rodenticides?

Anticoagulants may cause a person to bleed from their nose, gums or skin, according to the National Pesticide Information Center. Meanwhile, bromethalin can lead to an “altered mental status;” cholecalciferol may make people excessively urinate and feel very thirsty; and zinc phosphide can cause people to vomit, cough, feel chills or suffer from shortness of breath.

Last year, more than 250 people in Florida were reportedly exposed to rodenticides, meaning they ingested, inhaled or touched poisons, according to data from the American Association of Poison Control Centers. Many of those cases brought minor consequences at worst, said Alexandra Funk, managing director of the Florida Poison Information Center - Tampa. But she said four people died when they smoked “spice,” a synthetic marijuana substitute, laced with rat poison.

If someone has been exposed to rodenticide, call the Florida Poison Information Center - Tampa at 800-222-1222.

What about pets?

Anticoagulants may cause unusual bleeding, weakness and breathing problems in animals, according to the National Pesticide Information Center. Symptoms can take days to appear. An animal that eats bromethalin could become sensitive to light or noise and experience seizures or muscle tremors. Cholecalciferol may make animals vomit, have diarrhea, lose their appetite or appear depressed. Zinc phosphide can lead to vomiting and cause animals to pace, convulse or appear anxious and weak.

Nearly 1 of every 10 poison control calls to the American Society for the Prevention of Cruelty to Animals involved rodenticides last year, according to a spokesperson.

If your pet ate rat poison, call your veterinarian. The American Society for the Prevention of Cruelty to Animals pet poison control hotline can be reached at 888-426-4435. Another option is the Pet Poison Helpline at 855-764-7661. Both hotlines may charge fees.