The St. Tammany Parish Mosquito Abatement District received test results from the LSU Veterinary School Diagnostic Laboratory that indicated 11 mosquito pools were positive for West Nile virus out of 79 tested.  A mosquito pool consists of 5-50 adult mosquitoes collected from a given location and tested as one sample or pool.  The positive pools were collected from eight locations:  six from the Slidell area, one from Lacombe, and one from Pearl River.  Four positive pools out of 106 tested were received last week from three locations, which included one from Mandeville and two from Covington.  All of the positive mosquito pools were collected from the southern house mosquito, except one which was collected from an inland floodwater mosquito pool.  These test results indicate that the West Nile virus is present in the parish and mainly in one species, the southern house mosquito.  So far this year, a total of 1,650 mosquito pools have been tested throughout the parish, with 16 returning positive.  West Nile virus involves a bird-mosquito cycle.  Birds pick up the virus from the bite of an infected mosquito.  The bird, once infected, can then pass on the virus to non-infected mosquitoes when fed upon. 

The southern house mosquito is considered the primary vector for West Nile virus.  It breeds almost exclusively in roadside ditches that contain high organic content, commonly found in residential areas where homes rely on filter beds and septic tanks for waste water treatment.  The District places great emphasis on the control of the southern house mosquito by treating the ditches every 5-7 days to prevent adult mosquito emergence. Over the past week, the breeding levels of this species has decreased to an index of 3.3 larvae per dip.  If left unchecked, population levels in the ditches can explode to as high as 100-200 per dip.  In addition to the larval controls, ground and aerial treatments have been targeted against the adults of this species.  Last week all of the positive locations were sprayed.  This week large areas in Covington, Mandeville, Lacombe, Slidell and Pearl River will be sprayed by air, especially targeting the southern house mosquito and the locations that were positive for West Nile virus.  Truck spraying will also be conducted throughout the parish.

Residents should take special care to prevent the southern house mosquito from entering their homes.  It is active at night and will readily fly indoors.

The Asian tiger mosquito is another species that is capable of transmitting West Nile virus and is common to this area.  This mosquito breeds in artificial containers commonly found in and around yards.  Residents are urged to survey their yards for any containers that will hold water and discard them or store them where they will not collect water.  These 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.

As a precaution, residents should apply a mosquito repellent containing DEET when going into mosquito prone areas.  Be sure to follow the label directions when applying a repellent.