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After floods, hurricanes and other disasters, mosquitoes and other arthropod vectors and pests can become major public health and nuisance problems. This is particularly true during warm weather months
when various pathogens and parasites that can be transmitted to humans reach their peak abundance and can cause serious threats to human health. In the absence of diseases, these arthropods can become so
abundant that they cause disruptions in community services and cause severe stress in the affected local human, pet and livestock populations. For these reasons, the surveillance for and control of the
arthropod disease vectors and nuisance pests is considered an essential part of disaster recovery efforts and can be eligible for Federal Emergency Management Assistance (FEMA).
There are two primary groups of arthropods, mosquitoes and flies, that are likely to cause concern after a disaster. Since many mosquito control personnel are also involved in the control of other pests,
it is realistic to consider flies as part of post-disaster vector control efforts. Flies, like mosquitoes, will be a problem only during warm months. During warm and wet disasters, vegetation and animals
are killed and often swept away to be deposited in piles of debris. These dead remains can cause major house fly and blow fly problems. Which are of special concern because of their rapid dissemination
of Salmonella, Shigella, Vibrio, Escherichia and other bacterial organisms that can cause serious diarrheal diseases in humans.
Mosquitoes are the most important arthropod vector and nuisance pest problem after warm and wet disasters. During a hurricane adult mosquitoes near the center of the storm may be blown away or killed by
the strong winds. This means that for a week to ten days after a hurricane you will often experience normal or less than normal mosquito populations in those areas near the center of the storm’s path.
However, the heavy rainfall and tidal surges that accompany a hurricane will fill depressions that contain millions of mosquito eggs previously deposited on the soil, grass roots and plant debris. These
eggs will hatch within minutes after flooding and by day ten, post-disaster, will cause huge broods and swarms of mosquitoes that may cause major grief for recovery personnel and property owners working
out-of-doors, displaced persons in temporary shelters, and home owners staying in partially damaged homes. Serious health risks may arise during periods of heavy human and mosquito contact, particularly
if mosquito-borne viruses are circulating in the area.
The role of the local mosquito control program is absolutely essential for the rapid and efficient control of mosquito populations after a disaster. Post-disaster mosquito control can be very different
from Standard Control Efforts. Complaints and requests from the public and pressure for action from civil servants in high positions can become overwhelming and quickly cause burnout in persons working
16 to 20 hours a day in disaster relief. Also, an entire years stock of pesticides can be used up quickly and leave the program manager desperately searching for assistance. Accordingly, it is the
responsibility of the mosquito control program manager to prepare contingency plans for vector control after a disaster.
One of the first priorities of a disaster plan is to devise means to protect the integrity of the program. A vector control program is of no value after a disaster if all of the equipment, pesticides
and/or records are destroyed during the disaster. Protecting the stored pesticides is a must. A major spill situation from stored pesticides damaged in a disaster would create a situation that would
probably end the mosquito control career of the program manager. Looking out for the well-being of his/her employees is another major concern. Equipment and records losses can also cause serious delays
in responding to a disaster situation. Baseline data, including maps from normal operations are essential to quickly locating anticipated mosquito problem areas. However, anticipated areas may be only a
fraction of the actual problem areas that occur after a disaster. Thus, the program manager must build in plans for post-disaster surveillance to document the real problem areas. These plans could follow
those already described by Brown (1997) for the post-Hurricane “Fran” mosquito control efforts. There are a number of priority considerations for a program manager in preparing for vector control
after a disaster.
- The manager must be in communication with and work with the State Emergency Management Personnel in that area.
- The manager must determine the nature of the disaster and the possible vector problems.
- If it is a tornado or earthquake (a dry disaster) mosquitoes probably will not be a major problem, although house flies could be a major problem in warm months.
- If it is a flood, hurricane or other wet disaster during warm months, automatically assume that mosquitoes and flies will quickly become a major problem.
- If it is a wet disaster in cold winter months (floods), assume that later in the spring and early summer there will be large numbers of mosquitoes.
- If it is a disaster due to terrorist activity do not take any action without contacting the Emergency Management and Health officials and always follow their instructions.
- Prior arrangements need to be made to disseminate notices to the public to take personal protection measures against flies and mosquitoes.
- In the problem is larger than the abilities of the local program, the manager has two options:
- Request assistance from nearby control programs and/or the state mosquito control organization (Public Health Pest Management)
- Request assistance from the state and the Centers for Disease Control and Prevention (CDC).
The Public Health Pest Management Section, Division of Environmental Health, is the lead agency in the state for mosquito control and has the statutory responsibility and expertise to coordinate the
activities of over 90 mosquito control programs. In general, state resources are usually inadequate to handle emergency mosquito control. Thus, once there has been an official declaration of a disaster,
Federal (CDC) assistance can be requested. Getting CDC assistance is essential receive FEMA funds for vector control. Once CDC personnel arrive, they must assess the situation to determine if a request
for FEMA funds is justified. To qualify for Federal (FEMA) assistance for emergency vector surveillance and control, at least one of the following conditions must be certified by the CDC as having been
met (CDC 1993).
- Vector transmission of human or animal disease is considered imminent or in progress.
- Large populations of nuisance mosquitoes substantially hamper reconstruction efforts.
- Normal functioning of communities in the disaster area is substantially disrupted by mosquitoes.
- Large populations of nuisance mosquitoes place additional stress on the human population.
CDC prefers to respond to disaster situations with assistance to ongoing state and local mosquito control programs. If such programs do not exist, CDC will take the lead in vector control efforts.
However, if there are local and state programs, the primary function of CDC is a situation assessment per the four criteria above and to assist ongoing efforts. Assessment of a given mosquito problem
follows the guidelines of Moore, et al. (1993) and Nasci and Moore (1993). The three priories are to: 1) establish surveillance (if none is already available) – this is why baseline data from a local
mosquito control program is so valuable; 2) assess the public health threat; and 3) coordinate control (if that is needed). Disaster surveillance primarily targets adults through landing catches and
light trap (supplemented with CO2) collections, and larvae when possible. The latter may not be feasible due to flood waters. Collections help assess the nuisance level of the mosquito
population. Normally, a 3-5 specimens per minute landing rate is considered a problem, and rates in excess of 20 per minute are considered above the normal tolerance level for humans, pets and livestock.
After wet hurricanes, landing rates of 100 to 200 per minute are not uncommon. Light trap collections are used to determine the species emerging, and to reveal the presence of enzootic vectors of
arboviruses and ‘bridge’ vectors of epizootic arboviruses to humans, pets or livestock. Ongoing arbovirus surveillance, e.g., sentinel chicken flocks, can be very important for locating virus
activity. Assessing the public health threat requires a close coordination with state pest management, health and veterinary officials.
The certification of one or more of the above 4 criteria by CDC usually opens the door for FEMA monetary assistance. Because of extensive acreage involved in most disaster, assistance almost always
involves the use of Aerial Applications of Pesticides. Determination of the pesticide(s) of choice is not entirely left up to the state mosquito control personnel. The state toxicologist and health
director are also involved in this determination. Availability of local (state) licensed public health aerial applicators is another major concern. In their absence out-of-state assistance will be
required, which must be coordinated with the state pesticide licensing board. Other key considerations for aerial applications are: the presence and location of chemically sensitive persons, permission
for applications over densely inhabited areas, transportation of large volumes of pesticides, the use of Air Force aerial applicators, coordination with state and federal parks and wildlife refuges,
protection of the honey bee industry and close cooperation with the local media.
The local mosquito control program manager can be of great help to incoming vector control personnel by providing information and assistance when they arrive.
- Information about ongoing mosquito-borne disease activity in or near your area
- Acquire 1:25,000, 1:50,000 and other relief maps for the local disaster area
- Lists of key local personnel and their phone and fax numbers
- Clearance for incoming personnel and their vehicles
- Provide one local employee that knows the area
- Locate work and storage space for incoming personnel and their equipment
- Arrange sleeping and eating facilities for incoming personnel
References:
- Brown, J.S. 1997. Chronology of a mosquito control effort after Hurricane Fran. J. Env. Hlth. 60: 8-13.
- Centers for Disease Control and Prevention. 1993. Emergency mosquito control associated with Hurricane Andrew – Florida and Louisiana, 1992. MMWR 42(13):240-242.
- Moore, C.G., R.G. McLean, C.J. Mitchell, R.S. Nasci, T.F. Tsai, C.H. Calisher, A.A. Marfin, P.S. Moore, and D.J. Gubler. 1993. Guidelines for arbovirus surveillance programs in the United States.
U.S. Dept. Hlth. Human Svc., Public Hlth. Svc., CDC, 81pp.
- Nasci, R.S. and C.G. Moore. 1993. Planning for emergency mosquito surveillance and control. Wing Beats 4: 4-7.
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