One confirmed human case of West Nile virus in Madisonville and lab results that show the virus is present in mosquitoes all over St. Tammany Parish have mosquito-control officials stepping up spraying efforts and warning residents to take precautions against the biting insects.

An LSU lab confirmed that 14 mosquito pools out of 78 tested were positive for West Nile. A pool consists of five to 100 adult mosquitoes in a given location.

The St. Tammany Parish Mosquito Abatement District collected mosquitoes from sites in the Slidell, Mandeville, Covington, Abita Springs and Pearl River areas and from the community of St. Tammany.

Most of the positive samples were Southern house mosquitoes, a roadside-ditch breeder that is the primary carrier of West Nile. But Asian tiger mosquitoes and two other types of mosquito, a marsh-breeding species and an inland floodwater species, also tested positive for the virus.

The district has focused its treatment efforts on the Southern house mosquito and has seen a drop in its numbers. The district also has sprayed all the areas that tested positive last week, using both aerial and ground spraying.

But officials also are urging residents to take precautions, including keeping mosquitoes out of their houses as much as possible and emptying containers in their yards where Asian tiger mosquitoes commonly breed.

“The mosquitoes will only fly about 50 yards from their breeding site, so if an individual is experiencing a problem with them, the source is close by,’’ a district representative said.

Follow Sara Pagones on Twitter, @spagonesadvocat.