NE1943: Biology, Ecology & Management of Emerging Disease Vectors

(Multistate Research Project)

Status: Active


The need as indicated by stakeholders. Infectious diseases are on the rise worldwide and account for a quarter of all human mortality and morbidity despite extraordinary medical advances. Diseases once thought to menace only remote tropical regions are now spreading extensively due to dramatic social and environmental changes, including globalization, land use modification, and climate change. Of particular concern are those disease-causing pathogens that are transmitted by arthropod vectors. These diseases can spread rapidly and have complex epidemiologies that are susceptible to changing environmental conditions, and cause unpredictable costly outbreaks. Mosquitoes and ticks are the most important disease vectors in the U.S. and around the world. Worldwide, mosquito-borne diseases have killed more people than all the wars in history combined. Malaria probably killed more Americans than any other disease in the 1800s, except tuberculosis, cholera, and dysentery (Hong 2007, Urban 2010). More recently, West Nile virus (WNV) caused widespread fear in the U.S. when it was first detected in New York in 1999 and rapidly spread across the country within 5 years. WNV has emerged as the most important mosquito-transmitted disease in the U.S., with over 41,000 diagnosed cases and 1,700 deaths to date (CDC 2018a). Within the last 10 years outbreaks of emerging mosquito-borne diseases, such as chikungunya, dengue, Zika, and Rift Valley fever viruses, have revealed new vulnerabilities to the U.S. and around the world. Tick-borne Lyme disease is currently the most commonly reported vector-borne disease in the U.S. with an annual estimate of 300,000 cases, mostly in the northeastern and upper midwestern regions (CDC 2018b). Ticks also transmit a number of other microbial, protozoan, and viral diseases, some of which have only recently been identified and whose impacts on humans, livestock, and wildlife may be profound (e.g., Bourbon virus, heartland virus) (Savage et al 2013, Kosoy et al 2015). Overall, the CDC has reported that disease cases from infected mosquitoes, ticks, and sand flies in the U.S. have tripled in the last 13 years but that 80% of vector control organizations lack critical prevention and control capacities (CDC 2018c). There is also a need for better vector-human contact monitoring tools. These are helpful in calculating the risk of disease and potential pathogen emergence events.

The importance of the work and consequences if not done. With few available vaccines and new vector-borne diseases emerging at a steady rate, minimizing human exposure to disease vectors and managing vector populations remain the primary methods for reducing mosquito- and tick-borne infections.  Lyme disease continues to present the largest vector-borne disease burden in the U.S. with 30,000 cases reported annually to the CDC, but approximately 300,000 total human infections per year (CDC 2018b). In the past decade, several new tick-borne infections have been identified (e.g., Borrelia miyamotoi, B. mayonii, Heartland virus), and well-known infections have re-emerged such as Powassan virus, a potentially lethal tick-borne pathogen (Savage et al 2013, Kosoy et al 2015, Mansfield et al 2017). Other dangerous native pathogens include the mosquito-borne LaCrosse encephalitis virus, responsible for numerous cases of childhood encephalitis every year, eastern equine encephalitis (EEE) with about a 50% case fatality rate, and even pathogens that affect companion animals, such as the fatal dog heartworm.

Our ability to properly control these and other disease threats are limited by our understanding of vector ecology.  Historically and recently, investigations into basic science questions in vector biology have led to innovative control strategies.  However, invasive species threaten to alter the epidemiology and transmission dynamics of existing and new diseases, and ultimately the health of humans, pets, wildlife, and livestock. This presents a “moving target” that requires regular scientific investigation. Mosquito invaders include the yellow fever mosquito (Aedes aegypti) and the Asian tiger mosquito (Aedes albopictus), well established in the southeastern U.S. and recently reported in California as rapidly spreading (Metzger et al 2015). The Asian tiger mosquito is moving northward and newer mosquito species have also arrived, such as the Asian bush mosquito (Ae. japonicus japonicus), a cold weather adapted species that is becoming increasingly common in the urban and suburban landscapes along the eastern seaboard, as well as in the northwest and Canada (Kaufman & Fonseca 2014, Jackson et al 2016, Peterson et al 2017), and the Australian Aedes notoscriptus in southern California (Paterson and Campbell 2015).  Even within the last year, we have witnessed the invasion and spread of the Asian longhorned tick (Haemaphysalis longicornis), which was first discovered on a sheep farm in New Jersey in November 2017 and has since been detected in seven other states as of September 2018 (Beard et al. 2018, Rainey et al. 2018). The Asian longhorned tick can be self-cloning and is known to transmit several human disease agents in its native range in Asia, including spotted fever rickettsiosis and a potentially deadly virus (Severe Fever with Thrombocytopenia Syndrome Virus (SFTSV)) (Heath 2016). Experts expect that it is only a matter of time before this invasive species begins to transmit pathogens to Americans. Its immediate threat, however, is toward the country’s livestock. The Asian longhorned tick is known to multiply rapidly on livestock in Australia and New Zealand and can kill young animals by exsanguination (Heath 2016).

The U.S. will likely continue to experience the arrival of new vector species and pathogenic agents. Consider chikungunya virus, a dangerous pathogen that causes crippling arthritic damage to survivors, that infected more than 2.5 million people in the Indian Ocean region in a massive eruption in 2004-2005 and more than 350,000 people in the Caribbean in the first recorded outbreak outside of tropical Africa and Asia (Weaver et al 2018). Or the 2015-2016 outbreak of Zika virus, which infected tens of thousands of people in the Americas, causing severe birth defects as well as neurological problems in over 3,000 cases. The U.S. was affected during both outbreaks. Over 2,800 chikungunya cases were recorded in the U.S. in 2014 (CDC 2018d). Over 5,000 Zika cases were recorded in the U.S. in 2016, including 224 that were transmitted by local mosquitoes in the continental U.S. Ultimately, if infectious patients meet competent vectors then the disease can establish, amplify, and spread (CDC 2018e). The U.S. not only is a travel and immigrant destination for large numbers of people from around the world but also has highly competent mosquito vectors that include Ae. aegypti and Ae. albopictus.

The economic impact of arthropod-borne illness is devastating. For example, Lyme disease – America’s most common vector-borne disease - has been estimated to cost the U.S. healthcare system between $712 million and $1.3 billion annually in total doctor visits and testing one year after the first diagnosis, as symptoms of fatigue, musculoskeletal pain, and memory problems persist (Adrion et al 2015). The cost of treating WNV infections has been considerable, with Louisiana estimating $70 million for 2002 alone (Zohrabian, 2005). This estimate was made early in the outbreak and more recent estimates have indicated suggested that costs are much higher with total cumulative expenses related to reported hospitalized cases from 1999 through 2012 to be $778 million (95% confidence interval $673 million–$1.01 billion) (Staples et al 2014). The estimated cost per human case of EEE is $3 million in 1995 dollars (Villari et al. 1995). EEE and WNV both threaten the nation’s multi-billion-dollar equine industry. The mortality rate of horses infected with WNV is 34%; the rate for those with EEE approaches 100%. For example, in 2000, the estimated loss in New Jersey alone due to equine cases of WNV was $6 million. Tourism, which increases human exposure to mosquitoes, is similarly impacted by outbreaks of mosquito-borne disease. The recent outbreak of Zika virus, although generally mild in adults, has been conclusively linked to severe birth defects, which carry a tremendous economic and emotional burden on affected families. Recent computational analyses estimate that even a mild Zika outbreak could cost the U.S. in excess of $183 million in medical costs and productivity losses, whereas a severe outbreak could cost up to $1.2 billion.

The lessons learned from new and emerging mosquito- and tick-borne disease risks serve as an impetus for bolstering U.S. vector surveillance and management (Anyamba et al 2014). Encouragingly, important advances are being made in areas that include new methods and tools for monitoring and the control of mosquitoes and ticks. However, the budgets for research and abatement programs have been substantially reduced. In a report released in early 2018, the CDC estimated that 80% of the nation’s vector control organizations lack the critical prevention and control capacities needed to combat the tripling of disease cases from mosquitoes, ticks, and sand flies reported over the past 13 years (CDC 2018). Improved information sharing and coordination and the standardization of monitoring and control tools are needed for researchers and control professionals to make informed decisions and better utilize limited resources.

The technical feasibility of the research. Our research will focus on critical gaps in our understanding of the biology of mosquito and tick disease vectors of disease agents in the U.S. These include Ae. aegypti, Ae. albopictus and Culex pipiens mosquitoes, which are the three most important mosquito vectors nationally, and tick species (e.g., blacklegged tick, Ixodes scapularis; American dog tick, Dermacentor variabilis; lone star tick Amblyomma americanum) that are vectors of human pathogens. We will also gather vital knowledge on the ecology of other invasive vectors, with a focus on the newly invasive Asian longhorned tick, H. longicornis, in the early stages of its invasion and spread into the U.S., as well as encourage the knowledge infrastructure to deal with other potential invasive species. Our project will have three clear objectives:

  1. Develop and strengthen effective surveillance and monitoring of disease vectors at local and regional scales, including the development and testing of novel trapping and vector/pathogen identification techniques. Under this objective, project participants will leverage and strengthen existing surveillance programs in a coordinated fashion to yield robust comparable data across large geographic scales.

  2. Determine the ecology and geographic distribution of invasive and native disease vectors under changing environmental conditions to enhance our ability to predict conditions leading to existing and novel animal and human diseases.

  3. Develop novel control and management interventions and test their impacts on the transmission of human and animal diseases.

Under each of these objectives, we have 3-4 sub-objectives to focus our project, which is described in the Methods section. Our objectives are technically feasible, but only if done by a coordinated team. Our team is composed of 20 top entomologists who study tick and mosquito biology, with the required experience and facilities and we are confident we can succeed with the proposed research.

The advantages of doing the work as a multistate effort. This work cannot be completed without a multistate effort. In a rapidly changing landscape, the experience and guidance of one region are critical to others.  As a specific example, both Ae. aegypti and Ae. albopictus are new to California, and California abatement districts have benefited from the experience of those in the east coast states where these species are often the most common mosquito species. Conversely, researchers in Florida and Texas bring to the table experience working with populations affected with dengue and Zika, a set of skills that may be needed more broadly across the U.S.

What the likely impacts will be from successfully completing the work. The project will build a highly collaborative network of scientific expertise to deal with existing and newly invasive tick and mosquito species. The project will benefit all U.S. residents by understanding, assessing, and mitigating the threat posed by ticks and mosquitoes of public health, veterinary, and wildlife importance. Our efforts will strengthen capacity to detect and predict outbreaks of vectors and associated diseases and evaluate the effectiveness of existing and novel control interventions under different environmental and social conditions. The project further provides for and encourages environmentally sound, scientifically based, and professional control by public health and pest control agencies. Our proposed research directly builds on a prior multistate project (NE1443). Since 2014, we have met and exchanged published and unpublished results, have generated novel hypotheses from group participants and discussed coordination in sampling effort. We have produced numerous accomplishments and deliverables and garnered some competitive grants from newly formed collaborations. For this revision/replacement, we are now ready to expand our collaborative network to develop and strengthen a more coordinated region-wide and multi-state research effort.

Log Out ?

Are you sure you want to log out?

Press No if you want to continue work. Press Yes to logout current user.

Report a Bug
Report a Bug

Describe your bug clearly, including the steps you used to create it.