As an integral part of Integrated Pest Management, Cass County regularly conducts surveillance by trapping and identification of adult mosquitoes.
Cass County uses New Jersey light traps, CDC light traps (commonly refered to as Carbon Dioxide Traps), and gravid traps. Every trap consists of a small motor, fan, and collection net. However, each trap type utilizes a different attractant light and heat, light and carbon dioxide, or hay infused water. Each type of trap will attract various species mosquitoes. Once the adult mosquito is lured in by these traps, it is then blown into the net by the fan. There are as many as thirty five traps running daily in Cass County during the mosquito season.
Mosquito traps are placed out prior to our typical mosquito season (May-September) and are collected and counted daily. Most traps stay in a static location. This frequent monitoring offers Cass County Vector Control a number of benefits. Apart from giving us a "heads up" for overall increased mosquito activity, the number and frequency of trap counts allows Cass County Vector Control technicians to identify each mosquito trapped to the species level.
Speciation is an important part of surveillance. Knowing which species are present provides field aides an idea of where to look for potential breeding sites in the area (breeding habitats can vary between species). Speciation also lets us know if potential disease carrying mosquitoes are present. In addtion to knowing if disease carrying mosquitoes are present; Cass County can test groups (called pools) of mosquitoes for disease, like West Nile Virus.
Trap data can be difficult to understand. In the Fargo and West Fargo Metro area, trapping occurs from the evening hours to the early morning. Collections are taken every weekday, speciated, and reported after the end of the previous night's sampling interval.
In the rural areas, traps are collected every other weekday and the count is divided over the number of nights (intervals).
All traps run throughout the weekend, collected on Monday, counted, and reported as an average of each interval.
The Mosquito Meter
The "Mosquito Meter" is a summary of the data collected from traps in Fargo and West Fargo. In order to simplify the information, the Mosquito Meter is a set scale of female biting mosquitoes with each number corresponding to a 50 mosquito average in all metro traps.
Recently, the scale of the Mosquito Meter was moved from 100 down to 50. This change is a result of aggressive mosquito control efforts and is necessary because in recent summers the meter rarely showed more than 1. This was accurate for the scale at the time.
The Mosquito Meter can be misleading due to the fact that the information that is published was recorded the day before print and the trapping interval occurred the evening prior to that. For example: a "trap night" or sampling interval takes place on a Tuesday evening through Wednesday morning. The collection of mosquitoes is recorded as the Wednesday results. The Wednesday results are sent to the Forum the same afternoon. The most recent Mosquito Meter reading is tabulated and published in print on Thursday.
Cass County Vector Control does its very best to counteract any spikes of major mosquito outbreaks by taking numerous preventative actions. Vector Control also tries to estimate when the next spike will be so that we are prepared to take immediate action. Many times corrective spraying will occur before the Mosquito Meter ever elevates- We labor very intensively to make this the case.
Also at times, the average is not reflective of all areas of town because the population of mosquitoes is not homogeneous. So called "hot spots" do occur and we strive to respond as necessary.