West Nile Virus in North American Bird Populations

The Spread of West Nile virus

Prior to 1999, you had probably never heard of West Nile virus, and in fact, until then it was virtually unknown in the US. However, that year 62 human cases, 25 horse cases, and countless bird diagnoses were reported in New York state. Since that time the virus quickly spread throughout the country and has been documented in all of the lower 48 states, affecting more than 40,000 people.

While the effects of West Nile virus on human populations have been studied in great detail, and we have a fairly good understanding of its impact on human health, we are only recently starting to understand how it can make changes to bird populations and the larger ecosystem.

Like many mosquito-borne pathogens, West Nile virus has a complicated life cycle requiring amplification in birds and mosquitoes before being transmitted to people. For a person to become infected, they must be bitten by a mosquito that has previously fed upon an infected bird. It is also important to note that not all mosquito species are capable of carrying the virus, although documented in greater than 150 species.

The majority (80%) of people infected with West Nile virus will experience no symptoms, but it is possible for this disease to be debilitating and even deadly. Approximately 20% of people affected by the virus will experience flu-like symptoms including fever, headache, nausea, muscle pain, and swollen lymph glands. An even smaller proportion of people (1 in 150) will develop West Nile Encephalitis or Meningitis, which can be life-changing and lead to disorientation, coma, tremors, convulsions paralysis, and even death.

While the majority of funding for West Nile mosquito surveillance and control targets protecting human health, it is important to note that humans are not the only animals infected. A recent study by researchers at Colorado State University indicates that bird populations are, and continue to be, hit heavily by the disease, and the consequences of this can have a significant impact on the ecosystem at large.

When a new disease enters an area, disease ecologists expect to see major die-offs in the first year. However, over time, the impact of the disease is expected to decrease as the host population experiences increased immunity and can recover. Using data collected from over a quarter of a million birds belonging to 49 species, researchers have found that about half of the avian species affected by West Nile virus have made a recovery; however, the other half are continuing to experience major decreases in their population. Given the additional pressures on bird populations throughout the United States, of climate change, altered land use patterns, and feral cats, the added impact of West Nile on these populations is concerning.

Why so many bird species are unable to recover from the effects of West Nile virus is currently unknown. But when we think about the effects of mosquito-borne diseases decreasing the population of any species by 8-10% per year, it is quite shocking and should give us all reason for concern. As biologists attempting to control these vector-borne diseases, it is important that we consider not only the effects of the disease on human populations but other animal populations and the greater ecosystem as well.

Contact Us to Learn More About Effective Mosquito Management Strategies:

VDCI_Logo_squareSince 1992, Vector Disease Control International (VDCI) has taken pride in providing municipalities, mosquito abatement districts, industrial sites, planned communities, homeowners associations, and golf courses with the tools they need to run effective mosquito control programs. We are determined to protect the public health of the communities in which we operate. Our mosquito control professionals have over 100 years of combined experience in the field of public health, specifically vector disease control. We strive to provide the most effective and scientifically sound mosquito surveillance and control programs possible based on an Integrated Mosquito Management approach recommended by the American Mosquito Control Association (AMCA) and Centers for Disease Control and Prevention (CDC). VDCI is the only company in the country that can manage all aspects of an integrated mosquito management program, from surveillance to disease testing to aerial application in emergency situations.

Larval Mosquito Surveillance and Control Methods

larval surveillance

6 Components to a Mosquito Larval Surveillance and Control Program

Mosquito larval surveillance and larval control are critical components of any effective Integrated Mosquito Management (IMM) program because when mosquitoes are eliminated prior to becoming adults, they cannot pose a nuisance or disease problem. In fact, larval mosquito control measures are often the largest and most extensive aspect of municipal mosquito control programs and are more important than ever for compliance with state and federal regulations. Below we outline six key components of a successful surveillance larval mosquito surveillance and larva control program.

mosquito surveillance and testing

1. Larval Mosquito Surveillance

Trained field technicians must inspect both known sources of standing water and any newly discovered standing water for the presence of mosquito larvae. When a field technician conducts a larva survey of these mosquito larval habitats, they use standard larva dipping techniques to sample the water for the immature mosquitoes. If larvae or pupae are detected, the stage of development the larvae are in (Instar) and the number of larvae per dip is recorded, typically as an average of 3 – 5 dips per site. After the larval survey dipping takes place, the technician must determine the proper larval control measures that should be taken. Possible actions include: “No Action”, “Physical Control”, “Biological Control” or “Chemical Control”. 

2. Physical Mosquito Larval Control

Physical manipulation of the larval environment can be an effective anti larval control measure. Dumping a birdbath, bucket, or kiddie pool that has mosquito larvae present, unclogging a rain gutter that is holding water, clearing a culvert so a ditch will flow better, and disposing of a tire pile are all examples of physical larval control measures. Physical larva control has the advantage of not requiring any pesticide application and can often be maintained indefinitely through public education.

3. Public Education

Teaching people to be aware of potential mosquito breeding habitat in their area and showing them how to reduce or eliminate such habitat can help reduce mosquito populations. Each interaction with the public is an opportunity to educate citizens about where mosquitoes breed and lay their eggs. This knowledge can then be used to reduce mosquito breeding potential at the local level. Fliers and educational material can enhance this aspect of a larval control program.

4. Biological Mosquito Larval Control

Biological mosquito control involves introducing other living organisms into the mosquitoes’ environment to reduce the mosquito numbers through predation. Local laws must be considered prior to any biological control action, as the introduction of new species to an area is often regulated or prohibited. Fish, such as Gambusia affinis (the mosquito fish) or various minnow and sunfish species are all excellent biological controls for mosquito larvae. Propagating Dragonfly nymphs, either through transplanting or choosing to not use an insect growth regulator in certain areas, is another good biological larval control measure. 

5. Chemical Mosquito Larval Control

Chemical mosquito larval control is the most common form of larval control. The technician must assess the individual site, and if chemical application is warranted, determine what the appropriate larvicide is for that situation. The most commonly used larvicide across the country is Bacillus thuringiensis israelensis (Bti), a naturally occurring soil bacterium that is both target specific and environmentally sound. Other effective larvicides include another bacterium, Bacillus sphaericus (Bs), methoprene, an insect growth regulator, and several larvicide oils (primarily for control of mosquito pupae).

6. Record Keeping

Recording accurate data is one of the most important aspects of a larval control program. By using modern GPS/GIS technology, larval habitats can be mapped for use during further site inspections, to improve the efficiency and effectiveness of the larval control program and to meet regulatory requirements. Maintaining this data from year to year allows a program manager to understand the seasonal population trends in different larval habitats throughout their control area.

An important component of any successful Integrated Mosquito Management program is mosquito surveillance and larval control. A comprehensive larval control program should be one of the primary pillars for controlling nuisance and disease vectoring mosquitoes. Should you have any questions about your existing larval mosquito control program, or if you are considering establishing one, Vector Disease Control International (VDCI) is always available at whatever level of assistance you desire. 

Government Partners in Mosquito Management: Contact Us Today

Mosquito surveillance is an important component of an integrated mosquito management program. Our team of mosquito management experts take pride in partnering with municipalities, mosquito abatement districts, county, and state entities and are here to help guide you in delivering environmentally-conscious and cost-effective mosquito management.

Complete the form below or call 866-419-4716 to connect with a mosquito surveillance expert.

Government Partners in Mosquito ManagementSince 1992, Vector Disease Control International (VDCI) has taken pride in providing municipalities, mosquito abatement districts, industrial sites, planned communities, homeowners associations, and golf courses with the tools they need to run effective mosquito control programs. We are determined to protect the public health of the communities in which we operate. Our mosquito control professionals have over 100 years of combined experience in the field of public health, specifically vector disease control. We strive to provide the most effective and scientifically sound mosquito surveillance and control programs possible based on an Integrated Mosquito Management approach recommended by the American Mosquito Control Association (AMCA) and Centers for Disease Control and Prevention (CDC). VDCI is the only company in the country that can manage all aspects of an integrated mosquito management program, from surveillance to disease testing to aerial application in emergency situations.

Mosquito Surveillance For Effective Mosquito Population Control

mosquito surveillance and testing

What is mosquito surveillance? Why is it important?

While most people believe that mosquito control is nothing more than truck or backpack-based applications of pesticide, in reality, spraying to control adult mosquitoes is just one small aspect of a well-managed integrated mosquito management program. In fact, the foundation of every effective mosquito control program is mosquito surveillance.

What is a Mosquito Surveillance Program?

Mosquito Surveillance Programs involve the routine monitoring of both larval and adult mosquito populations over the course of an entire mosquito season.

While most people believe that mosquito control is nothing more than truck or backpack-based applications of pesticide, in reality, spraying to control adult mosquitoes is just one small aspect of a well-managed integrated mosquito management program. In fact, the foundation of every effective mosquito control program is mosquito surveillance.

Mosquito Surveillance Programs involve the routine monitoring of both larval and adult mosquito populations over the course of an entire mosquito season.

Setting a Mosquito Surveillance Trap

4 Reasons Why Mosquito Surveillance Programs Are Necessary

Mosquito surveillance is critical to a successful municipal or commercial mosquito control program for several reasons:

1. Monitoring changes in mosquito populations
2. Identifying which mosquito species are present
3. Detecting mosquito-borne diseases
4. Determining what control measures need to be conducted

1. Monitoring changes in mosquito populations

Monitoring changes in mosquito populations is important because it allows mosquito control experts to track exactly where the larval and adult mosquito populations are rising or falling. These data, when compared to previous weeks or previous years, provides the knowledge we need in order to identify and predict perennial, sporadic, or new problem areas, as well as to predict possible increases in the risk of mosquito-borne diseases. There is various mosquito surveillance equipment and several types of mosquito surveillance tools that are utilized to help monitor mosquito populations, including larvae dip cups, adult mosquito traps, and laboratory equipment.

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