The
most important action which can be taken by an individual property owner is to remove from
their property "all man-made potential sources of stagnant water in which
mosquitoes might breed." (W30.Nov01.WNV3)
- Awareness that mosquitoes are able to breed in any
puddle that lasts for more than four days is key to local source reduction. (W30.Nov01.WNV3)
- It is also important to recognise that many species of mosquito, including those which have been implicated
in the WN virus epizootic in the USA, lay eggs in standing water with an organic content.
(D72)
Local source reduction measures:
The following activities which may be undertaken by individual property
owners to prevent mosquitoes from breeding on their property
- Destroy or dispose of containers that collect and hold
water, such as tin cans, old tires, buckets, unused plastic
swimming pools or other objects.
- Do not allow water to
accumulate at the base of flower pots or in pet dishes for more than two
days.
- Drill holes in the bottom of containers which are left outdoors;
- Clean debris from rain gutters yearly and remove
any standing water under or around structures, or on flat roofs.
- Check around faucets and air conditioner units
and repair leaks or puddles that remain for several days.
- Eliminate seepage from cisterns, cesspools, and septic tanks.
- Change water in bird baths and wading pools at least once a week.
Stock
ornamental pools with top feeding predacious minnows (mosquito fish).
These
minnows are about one to one and a half inches in length and can be purchased, or
native fish may be seined from local streams
and creeks. Ornamental pools may be treated with biological larvicides
(Bacillus thuringiensis subsp. israelensis or products
containing Methoprene,
an insect growth regulator) under some circumstances. (W175.Nov01.WNV2)
- Remove excessive vegetation from ornamental
ponds.
- Fill or drain puddles, ditches and swampy areas, and either remove, drain,
treat with biological larvicides
or products containing insect growth regulators, or fill
tree holes and stumps with mortar.
- Turn over wheelbarrows and plastic wading pools when they are not in use;
- Eliminate standing water around animal watering
troughs, clean out livestock watering troughs thoroughly at least once a
month and preferably flush through twice a week;
- Irrigate lawns and gardens carefully to prevent
excess water that may stand for several days
- Cleaning and chlorinating swimming pools that are not in use; and
- Avoiding letting water collect on the top of swimming pool covers
or covers over boats etc.
- Check around construction sites, including
do-it-yourself improvements, to ensure that proper backfilling and
grading are present, avoiding drainage problems.
- Cover rain barrels with screening, or empty
weekly.
(D67,
D72, D73,
P32.1.w23, P32.1.w27,
W30.Nov01.WNV3,
W175.Nov01.WNV2)
- N.B. a study undertaken in Mississippi in 2002 indicated the
importance of local source reduction; the greatest increases in the risk
of WNV infection were found to be associated with environmental factors
favouring mosquito populations, including the presence of a septic tank in
the yard, the presence of an ornamental pond, having an abandoned property
nearby and having standing puddles nearby. (P48.4.w9)
- Public education is vital to maximise local source reduction
measures (D70,
P32.1.w27). See:
Education and communication for West Nile Virus
Larger scale sanitation measures:
On a larger scale, sanitation involves efforts such as cleaning or flushing storm
drains, removing tire piles, stream restoration, catch basin cleaning etc.
- "To prevent standing water, federal, state and local governments should maintain
the existing drainage structures on their properties such as preserves, sumps, recharge
basins, sewage or wastewater treatment facilities, street catch basins, salt marsh
ditches, upland streams, ponds, and pools (unless law dictates otherwise). IPM [Integrated
Management Plan] strategies to eliminate larval
mosquito breeding should be pursued. Privately owned or operated sewer facilities should
be maintained in a similar fashion to eliminate larval mosquito breeding." (D72)
- It is important to ensure that community-level actions are taken to
clean up used tire piles and other large trash/rubbish sites and to
drain large pooled water sources with vegetated edges and a high organic
content. (V.w42)
- In some situations open breeding sites may be filled with soil to
eliminate standing water. (D73)
- Standing waters such as salt-marshes, sewage lagoons, dairy lagoons,
storm-water retention ponds and farm dug-outs can be modified to be
unsuitable for mosquito breeding by good design, such as shorelines
which slope steeply and are gravelled, manipulation of water levels and
control of emergent vegetation.
- Existing sites may have shallow and marginal areas altered so they are
deeper with an increased slope; this decreases the establishment of
emergent vegetation.
- Wide ditches along major roads may be modified
to make them less efficient mosquito breeding sites by running a
narrower, deeper ditch through the centre.
- Shallow depressions and unnecessary ditches that
hold water may be filled or their drainage improved. (D73)
- Scraping sediment from the bottom of roadside
ditches may make them less attractive mosquito habitat. (D73)
- Patches of flooded habitat near to roadside
ditches may be drained into the ditch, which is more accessible for
further control if required (D73)
- If ditches do not flow and contain stagnant
water for a week or more they may produce large mosquito populations;
persons noting such ditches should report them to an appropriate
authority (e.g. a Mosquito Control Office or Public Health Office). (W175.Nov01.WNV2)
- N.B. local wildlife officials should be
consulted prior to carrying out source reduction to ensure that the
proposed measures are acceptable from the point of view of wildlife
habitat.
(D70, D72,
D73,
P32.1.w27, V.w42,
W175.Nov01.WNV)
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