Surveillance

Biology

Mosquito Identification

HOW WE LOOK FOR DISEASE

Samples of Female Mosquitoes 

Dead Blue Jays & Crows (Corvids)

Mosquito-borne disease surveillance is a very important part of our work as it promotes public health within Saginaw County. 

Monitoring virus activity and mosquito populations throughout the season dictates SCMAC’s control strategies both preventive and responsive as well as public notification and education. 

Arboviral disease testing is conducted by the MDHHS Bureau of Laboratories. 

Quality control is an important element of the Biology Department’s operation. Mosquito control products are scrutinized, as are application crews, to ensure effective, consistent, and high quality mosquito control. 

New insecticides and formulations are tested routinely to ensure the most environmentally acceptable and effective products are utilized. Monitoring insecticide resistance and changing management strategies is critical to ensuring effective mosquito control and maintaining a successful control program. 

Research is conducted by SCMAC annually. Only through improved knowledge and understanding of mosquitoes, mosquito-borne diseases, insecticides, and application equipment and techniques are we able to enhance our Integrated Mosquito Management Program.

Dead Bird Reporting

Residents of Saginaw County are encouraged to report dead crow and blue jay sightings

Birds in the Corvidae family, which include crows and blue jays, are very susceptible to West Nile virus (WNV). This often results in death for these birds. 

Depending on the condition and location of the dead bird, an oral swab is taken by biology staff. The swabs are sent to the Veterinary Diagnostic Laboratory at Michigan State University for WNV testing. This further allows the agency to monitor WNV activity in Saginaw County.

Adult Surveillance 

Routine adult mosquito surveillance is conducted using five trapping methods

The traps used are the New Jersey Light Traps, Centers for Disease Control (CDC) Traps, Gravid Traps, BG Sentinel 2 Traps, and Collection Bottle Rotator (CBR) Traps. Adults collected are used for species density information and all primary disease vectoring (transmitting) mosquitoes are processed and shipped to MDHHS Bureau of Laboratories for PCR testing to determine if they are carrying EEE, LAC, JCV, SLE, or WNV.

Approximately 2,000 female samples are collected yearly.

New Jersey Light Trap

The New Jersey Light Trap (NJLT) Program is conducted every Monday, Wednesday, and Friday during the mosquito season. Twenty-five of these traps are placed at geographically assigned locations throughout Saginaw County and manned by citizens. These traps monitor changes in local nuisance mosquito populations. 

Centers for Disease Control (CDC) Trap

The CDC Trap Program is conducted Monday through Thursday during the mosquito season. Spring and Summer Aedes mosquitoes are highly attracted to carbon dioxide (CO2) released by the dry ice. Five CDC traps are placed in tandem with gravid traps. Up to 5 additional CDC traps are placed individually at locations where increased mosquito population resolution is needed. Ten CDC traps allow us to survey 4 townships a night.

Centers for Disease Control (CDC) Elevated Trap

Elevated CDC traps are used to monitor disease, efficiently sampling summer Culex mosquitoes which are the primary vectors of West Nile virus. These customized traps baited with CO2 are placed 15-20 feet off the ground into the tree canopy where the Culex feed on birds (primary host). Elevated trapping begins in June and occurs on Wednesdays utilizing up to 4 elevated CDC traps nightly.

Gravid Trap

Gravid traps are used to monitor disease in Saginaw County. Gravid traps use highly organic water to attract female mosquitoes, especially Culex, looking to lay their eggs. These female mosquitoes have taken a blood meal and therefore are capable of transmitting arboviruses. Deployment occurs Monday through Thursday with 5 gravid traps paired with the 5 aforementioned CDC traps.

BG Sentinel 2 Trap 

The BG Sentinel 2 traps are deployed on Tuesday and run until Thursday, each week. The traps are baited with the BG lures. The BG Sentinel 2 and its lure are designed to attract and catch Aedes aegypti and Aedes albopictus. This is an important tool for Zika vectors should populations migrate into the Saginaw Bay region. 

Larval and Pupal Surveillance

All types of breeding habitat are routinely sampled, logged and specimens identified

The Biology Department samples flooded woodlots before and after aerial larva control in March and April. This monitoring ensures correct timing and application efficacy of the spring aerial program. Catch basins are routinely checked for infestation. Once an area’s infestation is 25% or higher, the entire area is treated.

All types of breeding habitat are routinely sampled, logged and specimens identified. This assists in the development of breeding site maps. 

Larval presence and densities aid in identifying control priorities. 

Mosquito-Borne Virus Surveillance

The female mosquitoes from specific species are submitted to MDHHS Bureau of Laboratories for their respective virus testing using PCR

Species Virus Tests - Virus Tests

Aedes canadensis - Jamestown Canyon virus

Aedes japonicus - West Nile virus, La Crosse Encephalitis

Aedes triseriatus - La Crosse Encephalitis

Culex erraticus - West Nile virus, Eastern Equine Encephalitis

Culex pipiens - West Nile virus, St. Louis Encephalitis

Culex restuans - West Nile virus, St. Louis Encephalitis

Insecticide Resistance

Adult mosquitoes are routinely tested for resistance by exposing them to lethal doses of various insecticides

If resistance appears to be present or developing in a given mosquito population, control strategies are altered to lessen the likelihood of future or continued resistance. If exposure to the insecticide in question is lessened or ceased there is a chance that resistance may subside, and a pesticide may be used again in the future. Mosquito populations can and have developed resistance to insecticides. Their ability to have many generations during a given year or season along with the consistent or prolonged exposure over many years to a single insecticide or group of insecticides may result in pesticide resistance. A resistant population is harder to control and resistance may be amplified if the use of the insecticide is continued.

SCMAC views pesticide resistance as a critical issue to our program’s effectiveness. As a result, a variety of EPA approved pesticides are utilized by SCMAC to combat this real concern. This strategy includes using biological insecticides, varying chemical groups, and using formulations in various combinations for differing habitats, mosquito developmental stages, and times throughout the season. 

Bottle bioassays are utilized by the Biology Department to expose mosquitoes to a given insecticide. A certain number of mosquitoes are placed in a bottle coated with a known amount of pesticide, mortality is monitored over time. Multiple replicates (bottles) and control bottles are used to better define susceptibility within a population. The more bioassays performed on a mosquito species or population the better the ability of SCMAC to monitor and define resistance within the County. Resistance testing is a continuing program to ensure effective and responsible use of pesticides. 

Caged mosquito tests are performed to ensure current adulticides control mosquitoes in the field. Adult mosquitoes are placed in cages and subjected to truck mounted ULV treatment. Mosquito species collected from different areas of Saginaw County are tested for susceptibility to not just current but new adulticide formulations. Testing new formulations allows for an operational understanding and expectation for the adulticide prior to incorporation into field services. The amount of mosquito mortality in the treated cages also allows SCMAC to watch for insecticide resistance. Multiple cage tests are completed each season to better evaluate adulticides.