PRO/AH/EDR> West Nile virus

Published Date: 2012-08-20 10:28:56
Subject: PRO/AH/EDR West Nile virus – USA (05): (ND) comments
Archive Number: 20120820.1252123

WEST NILE VIRUS – USA (05): (NORTH DAKOTA) COMMENTS
***************************************************
A ProMED-mail post
http://www.promedmail.org
ProMED-mail is a program of the
International Society for Infectious Diseases
http://www.isid.org

In this posting:

[1] North Dakota Department of Health news release

[2], [3] Comments

******

[1] North Dakota Department of Health news release

Date: Thu 16 Aug 2012

Source: North Dakota Department of Health news release [edited]

http://www.ndhan.gov/data/mrNews/ND14WNVcases.pdf

The North Dakota Department of Health reports 13 new human cases of West Nile virus [infection] since reporting the 1st case last week [week of 6 Aug 2012], bringing the statewide total to 14. This compares to only 4 cases confirmed in 2011. The North Dakota Department of Health has not detected increases in West Nile virus activity similar to what has been reported in the past week since 2007 when there were 369 human cases reported. Of the 14 confirmed cases, 5 have been hospitalized.

“We are starting to see significant West Nile virus activity in North Dakota and many parts of the country are seeing large numbers of cases,” said Alicia Lepp, epidemiologist with the North Dakota Department of Health. “People need to be aware that there are mosquitoes out there spreading disease even though the mosquitoes are not as visible as in past years. People need to take the proper precautions to protect themselves from this serious disease.”

People in North Dakota may not notice significant numbers of mosquitoes this year [2012], as indicated by the low number of mosquitoes collected in the state mosquito trap network. Many of the mosquitoes normally collected in the mosquito traps are “nuisance” mosquitoes and typically do not carry West Nile virus, meaning the number of mosquitoes collected in the traps does not necessarily indicate the number of mosquitoes carrying West Nile virus. The _Culex tarsalis_ mosquito, the mosquito that transmits West Nile virus in North Dakota, is most active between dusk and dawn and people may not recognize that they are being bitten. Those spending time outdoors, especially between dusk and dawn, need to make sure they are protecting themselves from mosquito bites.

To reduce the risk of being bitten by mosquitoes, the state health department recommends the following protective measures:

- Use insect repellent that contains DEET, picaridin, IR 3535, oil of lemon eucalyptus or permethrin when outdoors. Always follow the directions on the manufacturer’s label.

- Limit outdoor activities between dusk and dawn when mosquitoes are most likely to bite.

- When possible, wear long pants and long-sleeved shirts while outside.

- Eliminate stagnant water and leaf debris in containers around homes where mosquitoes can lay their eggs (such as, buckets, flowerpots, old tires, wading pools, and birdbaths).

- Keep mosquitoes from entering your home by repairing screens in windows and doors.

- Keep the grass around your home trimmed.

The following is a summary of West Nile virus activity in North Dakota to date [16 Aug 2012]:

- Human cases – 14

- Positive horses – 8

- Positive birds – 1

- Positive asymptomatic blood donors – 14 (not counted as cases)

- Statewide, activity has been detected in 16 out of 53 counties in North Dakota: Barnes, Benson, Burleigh, Cass, Grand Forks, Grant, Dickey, LaMoure, McIntosh, Ramsey, Ransom, Richland, Sargent, Stark, Stutsman, and Walsh.

–

Communicated by:

ProMED-mail

promed@promedmail.org

******

[2] Comment

Date: Thu 16 Aug 2012

From: Hugh J Baker [edited]

My guess would be that drought causes increased density of bird populations (aquatic and non-aquatic) visiting dwindling water supplies, making it statistically more likely that infected mosquitoes can feed from a greater number of hosts.

–

Hugh J Baker DVM

Etobicoke Ontario

Canada

******

[3] Comment

Date: Thu 16 Aug 2012

From: Linn David Haramis [edited]

In the Midwest US, “floodwater mosquitoes” (such as _Aedes vexans_) appear after heavy rains but they are very rarely infected with West Nile virus because they do not feed on birds. The larvae of the northern house mosquito (_Culex pipiens_), the vector of West Nile virus, develop in stagnant street catch basins (storm drains) and similar locations in urban areas so they are present during droughts. The house mosquito is a stealthy biter and it is not as noticeable as the swarms of floodwater mosquitoes we see during rainy summers. Furthermore, during drought periods, birds are likely to concentrate near sources of water — those are also likely to be near people. Finally, the human behavior factor has an impact. Because of the absence of swarms of generic “mosquitoes” (meaning non-vector floodwater mosquitoes in the Midwest USA), people see little need to use repellent during periods when the WNV infection rate in _Culex_ mosquitoes is RISING. In Illinois, hotter, drier summers such as in 2002, 2005, and 2006 have seen an increase in WNV activity in _Culex_ mosquitoes and associated human WNV cases. Educating the public that WNV risk increases during hot, dry weather (despite the absence of hordes of non-vector “floodwater” mosquitoes produced by heavy rainfall) continues to be a challenge to local and state officials.

–

Linn David Haramis, PhD

Vector Control Program Manager

Illinois Dept of Public Health

Div of Environmental Health

525 W. Jefferson St.

Springfield, IL 62761

[The sharp increase in North Dakota West Nile virus (WNV) human infections adds another state where clusters of human clinical disease are occurring. It is unfortunate that equine clinical cases are occurring there as well, since there is a commercial vaccine available. One hopes that people will heed the advice offered by the North Dakota Health Department, and other states experiencing human cases as well, to avoid mosquito bites.

ProMED-mail thanks Drs Baker and Haramis for their comments. It would be interesting to know if greater numbers of birds dead from WNV infection have been observed, if WNV antibody prevalence in bird species has increased, as well as if an increase in WNV field infection rates in _Culex_ vector mosquitoes has been observed in any of the focal areas of human cases.

A HealthMap/ProMED-mail interactive map showing the location of North Dakota in north-central USA can be accessed at http://healthmap.org/r/1m88. A North Dakota county map can be accessed at http://www.digital-topo-maps.com/county-map/north-dakota.shtml - Mod.TY]

Username
Password
× 9 = seventy two
	Remember Me Lost your password?

See Also

Share this: