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Mosquito Borne Disease Control

Mosquito Borne Disease Control

The purpose of the Mosquito Borne Disease Control Program Program is to prevent the transmission of West Nile Virus (WNV) that can cause encephalitis through establishing a mosquito monitoring and collection program.  The program is run by the PA Department of Environmental Protection and is administered at the local level by the Adams County Conservation District. 

The WNV is a mosquito-borne infection that can cause brain inflammation known as encephalitis.  The virus is transmitted by the bite of an infected female mosquito.  Mosquitoes get the virus when they bite or take a blood meal from birds infected with the WNV.  Those mosquitoes then transmit the virus to people, animals, and other birds when taking a blood meal.  It cannot be spread by person-to-person contact and there is no evidence that people can get the virus by handling infected animals, such as dead birds.  Although WNV is not transmitted through handling dead birds, proper precautions should be taken anytime you handle dead animals.

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Adult mosquitoes are trapped from April to October using gravid or dry ice-baited traps.  Once the mosquitoes are collected, they are sent to the PA Department of Environmental Protection (DEP) for identification and then onto the Department of Health for virus testing.  Mosquito surveillance is intensified if WNV is detected in mosquitoes, birds, other animals, and/or humans.

  • Dipping is the technique used when sampling mosquito larvae and pupae from their aquatic habitats.  Some of the habitats that are surveyed are temporary waters (tire ruts, flood plains, drainage ditches, catch basins), natural cavities (tree holes and rock pools), and artificial containers (tires, buckets, plastic covers over pools, bird baths, water troughs). 
  • Larval surveillance is important because it is used for identification of mosquito species and to establish their habitat preferences. 
  • When larvae and pupae are identified and counted, this information is used to determine if control measures are necessary in a particular area.
  • What do the traps look like?


Larval control generally has the least effect on non-target species and the environment. It is used to control mosquitoes in the aquatic stage before they become adults. In Adams County, naturally occurring bacteria are used to control mosquito larvae in problematic areas such as tire piles and catch basins.  

  • The bacteria are applied to standing water where the mosquito larvae are concentrated. 
  • The bacterium kills the mosquito larva after it is ingested. 
  • Adult mosquito control is only considered when evidence of the virus has been established or when nuisance levels become extreme.  
  • A press release will be sent to the local TV and Newspapers specifying the location, product used, and time of application at least 48 hours prior to any adult control operation.

West Nile Virus


Fortunately, very few mosquitoes are infected, so the chance of being bitten by an infected mosquito is very small.  If an infected mosquito does bite a person, it would take 5-15 days to develop the infection.  In many cases, the WNV may cause no symptoms or only mild flu-like illness.  In more severe and rare cases (less than 1% infected), a person may develop encephalitis.  Encephalitis can be a serious health threat for the elderly or people with weakened immune systems. 

Currently there is no vaccine for humans against the West Nile virus, nor is their specific treatment. However, the symptoms and complications of the disease can be treated.
  • Headache
  • High fever
  • Neck stiffness
  • Disorientation
  • Coma
  • Convulsions
  • Muscle weakness
  • Paralysis
  • And occasionally death


Mosquitoes lay their eggs in standing or stagnant water.  By eliminating places for mosquitoes to breed, we can greatly reduce the threat of the West Nile virus.  

Click on the list below to see some of the simple things that you can do to reduce the number of mosquitoes around your home and reduce the risk of being bitten:.  

  • Make sure doors and windows have tight-fitting screens, and repair or replace torn screens
  • Dispose of water-holding containers such as tires, tin cans, empty flowerpots, buckets, etc.
  • Turn over plastic wading pools, toys, wheelbarrows, etc. when not in use
  • Drain water from pool covers and keep pools clean and chlorinated
  • Make sure rain gutters drain properly
  • Change the water in birdbaths at least once a week
  • Aerate ornamental ponds or stock them with fish
  • Use mosquito repellants containing DEET when necessary and follow directions on the label
  • Limit time spent outdoors when mosquitoes are most active (between dusk and dawn)​

 In Horses

Horses become infected with the West Nile virus after being bitten by an infected mosquito.  Horse owners can reduce the likelihood of exposure to mosquitoes by eliminating standing water and by implementing pest management practices on their farm.

  • Loss of appetite 
  • Depression
  • Fever
  • Weakness or paralysis of the hind limbs
  • Impaired vision
  • Head tilt
  • Aimless wandering
  • Convulsions
  • Coma  
Horse owners should quickly contact their veterinarian to examine their horses and test for the disease if they believe it is present.  An equine vaccine for protection against disease from the West Nile virus infection was made available to Pennsylvania veterinarians in September of 2001.   

In Birds

The West Nile virus can also infect certain types of wild birds.  These birds serve as the natural reservoir for the virus. Infected birds, especially crows, can die because they seem to be highly sensitive to the virus.  Dead birds, or an overall decline in bird populations, are a possible indicator of West Nile virus in an area.  

The birds that are most likely to carry the disease, and therefore are the only species being tested currently are:
  • Crows
  • Ravens
  • Jays
  • Raptors 

Citizens are encouraged to report dead birds seen around their property or elsewhere to the Adams County Conservation District.  


Report a Problem

Call or email the Conservation District:

Visit the State's Vector Management webpage to submit complaints about Mosquitos, Dead Birds, or Black Flies: