University of Pittsburgh
ABSTRACT
Introduction: The Asian tiger mosquito, Aedes albopictus, is a vector of public health significance. It is an aggressive, invasive, day-biting mosquito that is a competent disease vector. The Asian tiger mosquito is able to transmit West Nile, zika, dengue, chikungunya and many other viruses. The Allegheny County Health Department monitors the Asian tiger mosquito to control further spreading of this mosquito and prevent illness.
Methods: Oviposition traps and on-site sampling were performed to monitor distribution and relative abundance of Ae. albopictus populations. Public outreach via conversation, distribution of literature and code enforcement were used to engage residents in the reduction of potential mosquito breeding sites present on residential properties.
Results: Ae. albopictus populations emerged in June 2018 and reached peak population levels by September 2018. Public outreach via conversation and literature distribution decreased the number of properties with potential breeding sites by 50%. Code enforcement showed a 100% reduction of residential properties with breeding sites.
Conclusions: Public outreach and code enforcement can be an effective strategy for breeding site reduction but should be focused on small areas because of the time required to perform multiple inspections.
TABLE OF CONTENTS
preface ix
1.0 Introduction 1
1.1 Vector Capability 2
2.0 Background 4
2.1 Feeding behaviors 5
2.2 Oviposition behaviors 5
2.3 Life Cycle 6
2.4 Migratory Patterns 7
2.5 Vector Control Strategies 8
3.0 Methods 13
3.1 Mosquito Surveillance 13
3.2 Public Outreach and Code Enforcement 14
4.0 Results 16
5.0 Discussion 20
5.1 Surveillance 20
5.2 Community Outreach 21
6.0 Conclusion 22
6.1 Limitations 23
6.2 Future Directions 23
Appendix: SUPPLEMENTAL Figures 25
bibliography 32
List of figures
Figure 1: Mosquito Life Cycle 6
Figure 2: Reporting of Ae. albopictus from 1995-2016 in the United States 7
Figure 3: Percent of Trap Sites with Eggs 16
Figure 4: Mosquito Egg Counts 17
Figure 5: Public Outreach and Code Enforcement 18
Figure 6: ARCgis Maps of Trap Sites 19
List of supplemental figures
Supplemental Figure 1: Oviposition trap and dipping examples 25
Supplemental Figure 2: Examples of Egg Counting, Larvae Rearing, and Identification 26
Supplemental Figure 3: Examples of mosquito breeding sites 27
Supplemental Figure 4: Mosquito breeding site inspection form 28
Supplemental Figure 5: Pamphlet distributed as outreach 29
Supplemental Figure 6: Pamphlet distributed as outreach 30
Supplemental Figure 7: Notice of violation example 31
preface
I would like to express my great appreciation to William Todaro for his mentorship and guidance on this project. I would also like to thank Leah Lamonte for her contribution to the project. Both were invaluable sources of knowledge. My grateful thanks are also extended to Dr. Jeremy Martinson, Dr. Martha Terry, and Jamie Sokol for their constructive suggestions and advice.
Introduction
Ae. albopictus, the Asian tiger mosquito, is a nuisance, day-biting mosquito that, once established, can plague communities forcing residents to stay indoors to avoid them. A study by Fonseca, et al. (2013) stated that control strategies for Ae. albopictus have proven to be unsuccessful unless new infestations in small areas are quickly controlled before they spread. This is supported by a study (Farajollahi & Nelder, 2009) in which the introduction of Ae. albopictus in New Jersey in 1995 spread to all but two rural counties (Sussex and Warren) located in the Northwestern region of the state by 2007. The highest Ae. albopictus population levels were seen in densely populated urban and suburban New York City and Philadelphia. Highly populated urban areas are at greater risk for disease outbreaks than rural areas which is why surveillance and effective mosquito management strategies are of the utmost importance. The Allegheny County Health Department (ACHD) performed surveillance for the Asian tiger mosquito in two neighborhoods in Pittsburgh, Pennsylvania. The goal of this study is double-pronged. One is to monitor the abundance and distribution of Ae. albopictus over a breeding season in chronically infested neighborhoods. The other is to learn if door-to-door outreach and code enforcement could have a measurable impact on reducing the number of mosquito breeding sites in those neighborhoods.
1 Vector Capability
Ae. albopictus is a studied disease vector. Westbrook et al. (2010) performed a study that determined the effect of temperature on chikungunya susceptibility in mosquitoes. The Asian tiger mosquito has been shown to produce larger adult mosquitoes and have increased susceptibility to chikungunya virus when larvae grow in temperatures of 18ºC (64.5ºF), as compared to larvae grown at warmer temperatures, 24ºC and 32ºC (Westbrook et al., 2010). An outbreak of chikungunya occurred in northern Italy in 2007 (Fredericks & Fernandez-Sesma, 2014). It was spread by Ae. albopictus and was initiated from an infected traveler returning from India. This reveals a scary truth that only one infected person is needed for an outbreak to occur even if the virus is not endemic to the area. Although chikungunya virus is not currently present in the Northeastern United States, these studies illuminate the effect of the mosquito larval environment in adult size and vector capacity and the ability of Ae. albopictus to transmit chikungunya virus. Another study by Nicholson et al. (2014) showed the effect of temperature on virus titers in adult Ae. albopictus mosquitoes. Mosquitoes at 22ºC had higher virus titer than those at 28ºC. In Tennessee, an estimated 3 out of 1000 adult Ae. albopictus were infected with La Crosse encephalitis virus (Westby et al., 2015). This is a frightening ratio because six to ten thousand adult mosquitoes can emerge from a single catch basin (e.g., sewage drain) every week during the mosquito season, mid-June to October or November depending on temperature. These studies suggest that Ae. albopictus can be an important disease vector in temperate regions. West Nile virus (WNV) is a vector-borne disease endemic to Allegheny County. The primary mosquito vector is Cx. pipiens which maintains the virus transmission cycle by feeding on infected birds and then feeding on humans. Ae. albopictus may serve as a bridge vector for WNV as it is susceptible to and capable of transmitting it to humans (Vanlandingham et al., 2016). In addition to WNV, Ae. albopictus has been recorded to be a vector for dengue (Vitek et al., 2014), zika, Japanese encephalitis (Nicholson et al., 2014), and La Crosse encephalitis virus (Westby et al., 2015). Dengue virus infections result in an estimated 50-100 million disease cases a year (Stanaway et al., 2016). Japanese encephalitis causes 5-50 cases of disease per 100,000 people in endemic regions (Asia and the Middle East). All of these diseases have the potential to be introduced to Allegheny County.
Background
Aedes albopictus, the Asian tiger mosquito, is native to Southeast Asia, but has recently been found in many other countries and continents around the world. The primary form of migration is through international trade, specifically the tire trade. Reiter (1998) discussed the introduction of Ae. albopictus into many different countries. As a result, Venezuela banned the imports of tires in 1993 to stop the spread of invasive mosquito species. The Asian tiger mosquito was first recorded in the United States in Houston, TX, in the 1980’s. The North American strain of Ae. albopictus is believed to be native to a non-tropical region of Japan. Mogi & Tuno (2014) analyzed the effect of climate change on the distribution of Ae. albopictus in Northern Japan, showing that thermal suitability alone did not indicate establishment of populations. Other factors also contribute to Ae. albopictus migration. For instance, rapid range expansion of Ae. albopictus after 1990 in Northern Honshu was supported only for inland areas and the northernmost Pacific coast. The likely reason that climate change supports northern expansion of Ae. albopictus is due to decreasing coldness in the overwintering season instead of increased warmth in the reproductive season (Nicholson et al., 2014, Mogi et al., 2014). A decrease in coldness allows more eggs to survive overwintering which has allowed Ae. albopictus to increase its range and potential to spread disease. Areas on the edge of the potential range of Ae. albopictus require repeated introductions for populations to establish, however, reintroductions do not guarantee the establishment of new populations.
1 Feeding behaviors
Ae. albopictus feed throughout the day, from dawn to dusk, with peak feeding activity in the late afternoon (Kamgang, Nchoutpouen, Simard, & Paupy, 2012). The extended feeding timeframe allows for contact with and feeding on many different hosts. Ae. albopictus take partial blood meals from multiple hosts rather than complete blood meals from a single host. This behavior improves fitness because the mosquito is less likely to be noticed by each individual host. Along with improved fitness the mosquito also has a greater chance to feed on hosts infected with pathogens, such as dengue and chikungunya, that cause human disease.
2 Oviposition behaviors
Ae. albopictus are small container breeders that exercise skip oviposition. They lay groups of eggs in many different breeding locations. This type of oviposition behavior increases the likelihood that at least one group of eggs will successfully hatch and mature into adulthood. Ae. albopictus will lay eggs in areas as small as a bottle cap which provides them with a large pool of breeding sites when introduced to a new location. The ability of Ae. albopictus eggs to hatch quickly gives them a developmental advantage over other species that may be present in the same container (Lounibos, et al., 2001).
3 Life Cycle
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Figure 1: Mosquito Life Cycle
Life cycle of Aedes mosquito species (CDC).
The mosquito life cycle, Figure 1, consists of 4 major phases: egg, larval, pupal, and adult. The egg phase lasts about 3-7 days during the mosquito season but can last for months if eggs are in a hostile environment, e.g., overwintering. The low hatch time of Ae. albopictus eggs gives them an advantage over Ae. triseriatus, the resident tree-hole mosquito in Allegheny County Pennsylvania, which breeds in the same habitats. The larval phase lasts about 5-7 days. In this phase the larvae go through five instars, developmental stages, until they are mature enough to pupate. The pupal phase lasts 2-3 days and is the final phase before the mosquito emerges as an adult. The entire life cycle, from egg to adult, can be completed in as little as 10 days.
4 Migratory Patterns
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Figure 2: Reporting of Ae. albopictus from 1995-2016 in the United States
Number of years with at least one Ae. albopictus report between 1995 and 2016. Map is broken up into counties; no reported records (white), 1 year reported records (yellow), 2 years (orange), and 3 or more years (red). A black dot denotes the first time that that county has recorded Ae. albopictus (Hahn et al. 2017).
Since its introduction in Texas in the late 1980’s Ae. albopictus has spread through the Southwest and Eastern United States. A study by Hahn et al. (2017) gathered data from health departments around the United States to determine where Ae. albopictus has been identified from 1955 to 2016 (Figure 2). The study showed that 1368 counties in 40 states reported the occurrence of Ae. albopictus, and 573 counties in 34 states reported 3 or more years of Ae. albopictus occurrence (Hahn et al., 2017). Surveillance bias could be introduced because counties that had ongoing surveillance for Ae. albopictus would have reports of this mosquito. If all counties in the United States surveyed for the Asian tiger mosquito, there may be more counties with at least one year of reported Ae. albopictus. The Asian tiger mosquito has spread rapidly since its introduction and continues to push its geographic limits through migrations in the used tire trade. The diapause trait exhibited by the Asian tiger mosquito is a key factor in its ability to thrive in many different climatic and geographic areas. Diapause is a trait seen in many different insect species and allows eggs to go into a dormant phase to survive harsh conditions like drought or winter temperatures. Once conditions are more ideal, the eggs can hatch after being flooded with rainfall. Evolutionary pressures have selected for Asian tiger mosquitos that find safe locations for eggs to overwinter and/or outlast droughts. The recent climate change has decreased the intensity and duration of winter temperatures which also allows more mosquitos to survive through winters (Nicholson et al., 2014, Mogi & Tuno, 2014). Although temperature is an important factor in determining range, precipitation is just as important with hot dry conditions being most detrimental to egg survival (Nicholson et al., 2014).
5 Vector Control Strategies
Mosquito control can be accomplished using three different methods: larvae control (either by inhibiting growth or killing larvae with chemicals or predators) breeding habitat removal/destruction and decreasing adult population with trapping and/or spraying adulticides. In many cases a single approach is not adequate to control mosquito populations, so a combination of strategies is used. This is termed as integrated mosquito management (IMM). The most cost-effective forms of treatment are larvae control and breeding habitat removal.
Treatment with bacteria in common breeding sites (e.g., catch basins) can be an effective form of larval control. Bacillus thuringiensis subspecies israelensis (Bti) is a soil-borne bacterium that is toxic to mosquito larvae. Chang et al. (2014) compared mixtures of essential oils with Bti to determine if toxicity would be higher than with only Bti treatment. The study tested E-cinnamaldehyde (CA), eugenol (EU), and E-anethole (AN) which are constituents of cassia bark, clove bud, and star anise, respectively, on Anopheles sinensis and Ae. albopictus. The mixtures of Bti with CA, EU, and AN all proved to be more toxic than any individual treatments. Bti + CA was the most toxic of all mixtures. Although more research needs to be done on the mechanisms involved in Bti/essential oil mixtures, it is important to note that Bti/essential oil mixtures showed similar effectiveness on insecticide-resistance and susceptible mosquito species.
Another form of larvae control uses (S)-methoprene as an insect-growth regulator. Methoprene inhibits progression from larvae to pupal and adult stages by prohibiting the insect juvenile growth hormone from functioning properly, which prolongs the larval life stage (Environmental Protection Agency, 2001). An increase in the larval life stage allows predators and other environmental factors to kill mosquito larvae. This treatment can be administered in a few different formulations: briquettes that provide long lasting effects of about 150 days, granules that work for about 30 days, and pellets that work for about 30 days. A study by Harbison et al. (2018) measured the effectiveness of these three treatment types over a 16-week period during the mosquito season. The study took place in Cook County, Illinois and compared effectiveness of the three formulations of Altosid methoprene based products (listed above) in catch basins. The results of the study showed that all forms of treatment were statistically significant in controlling the mosquito populations, by reducing larval progression into both pupae and adults than the untreated group Out of the treatments, the pellet form of Altosid provided the greatest control, 21.8% of larvae emerged as adults, as compared to briquettes, 64.6%, and granules, 55.5%. This is contradictory to the thought that pellets are more likely to be washed away during heavy rainfall than briquettes (Nasci et al., 1994). This study also stated that Altosid pellet treatment was effective at providing long-term control of Ae. albopictus populations in Lake Charles, LA. Methoprene is not known to act as a repellent to mosquito oviposition in Culex spp. and Aedes japonicus (Butler et al., 2006).
Introduction of predators of Ae. albopictus into catch basins can provide lasting larvae control for an entire season. A study by Veronesi et al. (2015) done in Italy determined the ability of Macrocyclops albidus (Copepoda: Cyclopidae) to reduce larvae populations of Ae. albopictus and Cx. pipiens. First, they established how many larvae one copepod could kill at a saturation of 50 larvae/copepod in 24 hours. One copepod could kill 29 Cx. pipiens larvae and 27 Ae. albopictus larvae on average. The study compared different concentrations of M. albidus, 100 and 500 at a 50/1 larvae/copepod ratio in 200-liter drums. The results showed 99.9% and 100% control of Ae. albopictus larvae and 88.69% and 84.65% of Cx. pipiens, compared to control, in the 100 and 500 copepod trials, respectively.
Community outreach to reduce the number of mosquito breeding sites in urban neighborhoods can provide a long-lasting and inexpensive form of mosquito control but can be difficult to achieve and measure. Bartlett-Healey et al. (2011) implemented two forms of outreach: educational curriculum for 3rd to 5th grade students and educational brochures for adults in Monmouth and Mercer counties in New Jersey. After one year, the program showed a decrease in breeding sites, but it was not statistically significant when compared to the control site that had no intervention. A possible reason for this could have been the presence of mosquito personnel at all of the sites, which may have indirectly caused residents to reduce breeding sites in the treatment and control groups. The same group performed another study (Healey et al., 2014) that looked at the effect of active education (community presentations, media releases, tire pick-up days, and trash can drilling days) and recruitment of community volunteers. They observed a 22.6% decrease in container habitats in the communities being educated, compared with a 32.3% increase in the number of breeding sites in the areas that did not receive education. The goal of the study was to evaluate the use of community peer educators in promoting reduction of mosquito habitats. The introduction of community members as peer leaders in the intervention may have contributed to its success. The members of the community will be more receptive to instructions coming from a fellow member who is setting an example or a local organization leading an educational session (Perez, et al., 2007).
Trapping adult mosquitoes and treating neighborhoods with aerial applied pesticides are other effective forms of adult mosquito control. Many traps exist for adult mosquitoes and trapping can help to reduce the number of adult mosquitoes present in the environment. Trapping can also be performed for surveillance. Two primary traps are used for mosquito surveillance, oviposition and Biogents (BG) sentinel traps. Oviposition traps are targeted for Aedes species mosquitos as these traps replicate small artificial containers. In Allegheny County, the invasive Aedes japonicus and Aedes albopictus mosquito species are commonly found in oviposition traps. Unlike oviposition, the BG sentinel trap can be effective in both surveillance and adult population control. These traps catch and kill adult mosquitos with the use of a lure and fan to collect them. Different mosquito species will prefer different lures, so this trap can be modified for the species of interest.
Ae. albopictus mosquito populations have been high in the Pittsburgh neighborhoods of Bloomfield and Lawrenceville in previous years, as reported by the ACHD. Education of community members in breeding site reduction could provide a long-term solution to controlling mosquito populations. This study was performed to determine if door-to-door outreach could be an effective strategy in encouraging community members to reduce mosquito breeding sites and to continue monitoring the Asian tiger mosquito populations in these neighborhoods.
Methods
1 Mosquito Surveillance
Oviposition trapping: The trap used was a 24 SpringStar “Trap n’Kill” Ovitraps (TK71015), manufactured in Woodville, WA. The attractant was an oak leaf infusion, which was made using two gallons of deionized water and approximately 20 grams of pin oak leaves. The infusion was allowed to sit for 3-10 days before use in the oviposition traps. A pad on which mosquitoes were to lay their eggs was made with a 1”x3” patch of red Velcro-type fabric stapled to a wood paddle (tongue depressor). Twenty-four total trapping sites were chosen in the Pittsburgh neighborhoods of Bloomfield and Lawrenceville, 12 sites each neighborhood. Lawrenceville and Bloomfield were chosen because they have been hot spot areas for Ae. albopictus activity in the past. The 12 trapping locations in each neighborhood were selected randomly, based on environmental conditions observed from the street. Ideal environmental conditions were shaded areas where chances of predation were minimalized by being secured off the ground. All traps were located in shaded areas, but not all traps could be secured off the ground. The traps were secured at each site and left for a week, after which they were collected. The one-week time constraint was to give the mosquitoes enough time to breed but also to reduce the chance of predation (Supplemental Figure 1A). Traps were collected at three different timepoints: June 27, August 1, and September 7 of 2018. The pads and wood paddles from each trap were examined for presence of mosquito eggs. The number of eggs, if any, were counted (Supplemental Figure 2A and 2B). Egg counting was capped at 200 eggs per paddle.
Larvae rearing: Paddles from the oviposition traps that contained eggs were floated in separate containers until larvae hatched from the eggs (Supplemental Figure 2C). The larvae were fed mixtures of finely ground cat food and fish meal until they reached the fourth instar (Supplemental Figure 2D). Mosquito larvae were counted and then sacrificed for species identification (Supplemental Figure 2E).
Larvae identification: Identification was performed using a dissecting microscope and a dichotomous key for mosquitoes of Ohio.
Dipping: Mosquito larvae were collected from breeding sites in the field using hand-held one cup sized dippers. Mosquito larvae is placed in a sealed vial with date and location of collection recorded. Collection occurred during trapping and inspection of properties (Supplemental Figure 1B and 1C).
The data was recorded using Microsoft Excel data sheets.
2 Public Outreach and Code Enforcement
Property inspections: The city blocks surrounding the trap sites in Lawrenceville and Bloomfield were inspected for possible mosquito breeding sites. Possible mosquito breeding sites were defined as artificial containers (e.g., tires, buckets, planters, assorted garbage) holding water upon inspection. Blocked roof gutters and flat garage roofs were included where accessible (Supplemental Figure 3A to 3F). Inspection of property included visual detection of possible mosquito breeding sites in visually accessible areas of properties. If mosquito breeding sites were found, the property address, types of breeding sites, and number of breeding sites were recorded on a generated inspection form (Supplemental Figure 5). The data was then input into an Excel spreadsheet. Locations with probable mosquito breeding sites were re-inspected a week after initial inspection and outreach, either via conversation or via literature. If breeding sites were still present in the control group, which received no public outreach, the location was noted. On the other hand, if the breeding sites were present in the treatment group, which received outreach, further steps were taken to ensure removal of the site.
Public outreach: Door to door outreach was implemented in the same areas that property inspections were performed. If mosquito breeding sites were seen upon inspection, then an attempt was made to talk with the resident and distribute literature on mosquito control and protection tactics for members of the community (Supplemental Figure 6A and 6B, 7A and 7B). If the resident was not home, then one of the two premade pamphlets was left in the mailbox (Supplemental Figure 6A and 6B, and 7A and 7B). The two pamphlets had similar information and were distributed to the residents randomly. Upon reinspection after a week, any location from the treatment group which had not cleared the mosquito breeding site was given a notice of violation (NOV, a Standard Form Letter provided by the Housing and Community Environment office of the Allegheny County Health Department) (Supplemental Figure 8) as a secondary intervention. Inspection occurred again on the date specified on the notice of violation. This is the first year that data was recorded on compliance to literature distribution and NOV at properties where mosquito breeding sites were identified. Twenty-four residential properties were included in the treatment group. A control group consisting of 21 residential properties located in Upper Lawrenceville received no outreach.
Results
Traps in Lawrenceville had 42%, 92%, and 100% presence of mosquito eggs at the June, August, and September trappings, respectively. Bloomfield had 58%, 75%, and 100%, respectively, of traps with mosquito eggs present on each of the 12 trap sites per neighborhood (Figure 3).
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Figure 3: Percent of Trap Sites with Eggs
Percent of trap sites where mosquito eggs were present in Lawrenceville (blue) and Bloomfield (orange), at June 27th, August 1st, and September 7th, 2018.
Lawrenceville traps yielded 113, 773, and 1756 eggs for each round of trapping, respectively. Bloomfield traps yielded 493, 529, and 1493 eggs for each round of trapping, respectively (Figure 4).
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Figure 4: Mosquito Egg Counts
Fifty-four percent of residents with a violation that received outreach, removed or treated possible mosquito breeding sites within one week of inspection. The remaining 46% of residents with a violation that were issued an NOV as a secondary intervention removed or treated possible mosquito breeding sites by the date specified on the NOV (Figure 5). This is the first year data was collected on resident compliance in the removal of mosquito breeding sites.
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Figure 5: Public Outreach and Code Enforcement
Figure 6 compares the presence of Ae. albopictus in Lawrenceville and Bloomfield. Ae. albopictus was identified in 2 of the 12 trap sites in Lawrenceville and Bloomfield after the first round of trapping (Figures 6A and 6D, respectively). The second round of trapping produced Ae. albopictus in 10 of 12 and 9 of 12 sites in Lawrenceville and Bloomfield, respectively (Figures 6B and 6E). 12 of 12 and 10 of 12 traps in Lawrenceville and Bloomfield, respectively were identified to have Ae. albopictus present after the third round of trapping (Figures 6C and 6F).
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Figure 6: ARCgis Maps of Trap Sites
Small red dots indicate trap sites that Ae. albopictus was not identified from larvae. Large blue dots with purple center represent trap sites that Ae. albopictus was identified from larvae.
Discussion
1 Surveillance
The Asian tiger mosquito has been previously reported in Lawrenceville and Bloomfield based on data previously collected by the Allegheny County Health Department. Oviposition traps were set to verify that the Asian tiger mosquito was still present in these neighborhoods and to monitor the population throughout the summer. Egg populations were low in Lawrenceville when comparing the first round of trapping to the second. However, Bloomfield showed similar egg numbers in the first and second rounds of trapping. The third round of trapping yielded a two-fold increase of eggs in Lawrenceville and a three-fold increase of eggs in Bloomfield. This suggests that the Asian tiger mosquito population has a peak between mid-August and early September, so it is important to make reductions in available breeding sites before August. Other factors, such as precipitation and temperature, can influence the time within the season that Asian tiger mosquito populations begin to thrive. In general, they follow a trend that observes peak population numbers in late summer which is consistent with previous years.
2 Community Outreach
The Asian tiger mosquito is a major invasive nuisance mosquito in Allegheny County. Large tire dumps have historically been associated with high levels of the Asian tiger mosquito. For this reason, many illegal tire dumps in Allegheny County have been cleaned up (Allegheny CleanWays, 2017). According to ACHD the removal of illegal tire dumps has been a cost-effective measure because it decreased the need to spray pesticide for high nuisance mosquito populations. Now, densely populated urban areas are the primary concern. These environments provide a myriad of breeding habitats for Ae. albopictus mosquitoes. Tree holes and bamboo shoots were some of the native breeding sites for the Asian tiger, but its aptitude for finding small water holding containers has given it an advantage in these crowded neighborhoods that contain many artificial containers. Tires, rain gutters, catch basins, buckets, and flower pots are common breeding sites in the urban environment, but any object that can allow water to pool for 7-10 days has the potential to breed mosquitoes. The Allegheny County Health Department treats catch basins within the city of Pittsburgh with methoprene containing briquettes to reduce their ability to produce large quantities of mosquitoes. The efforts made to eliminate large possible breeding sites, illegal tire dumps, and a high number of artificial containers has resulted in a major decline of the Asian tiger mosquito populations throughout the summer season. If the Asian tiger mosquito was unable to transmit any medically important diseases, then these mosquito control tactics may suffice, but the ability to carry and transmit a variety of serious diseases like dengue and zika virus make the Asian tiger mosquito an important vector to monitor.
Conclusion
The general population plays a large role in the increase or reduction of potential mosquito breeding sites within a community. It is time to empower members of the community to be vigilant in ridding their properties of mosquito breeding sites. Public outreach is necessary for this to occur but may require community events along with door-to-door outreach and code enforcement. Hot spot areas for mosquito activity should be targeted first. The goal for this intervention was to educate community members on ways to reduce the number of mosquito breeding habitats and limit susceptibility to mosquito bites. Although the study was small (24 and 21 properties in the treatment and control groups) it does indicate that public outreach, even without code enforcement, can have a positive impact on reduction of mosquito breeding site behaviors. Healy et al. (2014) performed a community-based education program and reported a 22.6% reduction in possible breeding sites. Community engagement is imperative to maintain long-term low-cost mosquito control in the city of Pittsburgh. Programs like the Mosquito Surveillance and Control program sponsored by the Allegheny County Health Department and the Pennsylvania Department of Environmental Protection are critical in maintaining control of public health pests, like the Asian tiger mosquito. Controlling the Asian tiger mosquito now will lead to less devastation when the diseases it can transmit are introduced into the Pittsburgh area.
1 Limitations
It is labor intensive to perform property inspections and outreach. Healy et al. used AmeriCorps members to assist with property inspections and community outreach. In areas where it is difficult to recruit volunteers, large scale community outreach may not be feasible. Therefore, outreach should be reserved for areas that have historically high mosquito levels or areas that produce high amounts of complaints.
Another limitation focuses primarily on the metric to measure effectiveness of community outreach. Effectiveness is most easily measured by reduction of mosquito breeding sites. In tight city neighborhoods, it can be difficult to thoroughly inspect properties, due to inaccessibility and/or poor visibility of the property. This can result in undercounting of breeding sites at properties.
2 Future Directions
A partnership with community organizations and/or schools to assist in disseminating educational material could lessen the burden on health departments and more actively involve the community in controlling the mosquito population. A program adapted from Healy, et al. (2014) in which community events are performed from June to August would be used. Examples of community events include community presentations, tire pick-up days, trash can drilling days, and active door-to-door education. The active education would be performed by community peer educators that receive training in mosquito biology and breeding site reduction.
Increased media attention, especially at the beginning of summer, reiterates to the community its role in reducing mosquito populations. The initial zika outbreaks in South America and Florida greatly increased the public’s awareness of the Asian tiger mosquito and its ability to transmit infectious diseases.
Drones could be used to quickly survey large areas for possible mosquito breeding sites that may be difficult or impossible to see from ground level, e.g., rain gutters on rooftops. This would greatly decrease the time required to inspect properties by foot which would allow for more widespread inspection.
Appendix: SUPPLEMENTAL Figures
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Supplemental Figure 1: Oviposition trap and dipping examples
An example of an oviposition trap set in an environment conducive to an Aedes albopictus breeding site (A). Examples of dipping in the field for mosquito larvae (B-C). [Photos (A-C) used by permission of Allegheny County Health Department (2018).]
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Wood paddles from oviposition traps were analyzed with a microscope (A) to count the number of mosquito eggs (B). The wood paddles were floated (C) in order to hatch the eggs (D). The larvae were reared for identification purposes (E). [Photos (A-E) used by permission of Allegheny County Health Department (2018).]
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Examples of mosquito breeding sites found during inspections of residential properties in Allegheny County during summer 2018. Buckets, trash cans, planters, and tires were commonly found sites. Flat rooftops were inspected for pooled water and rain gutters and drains were checked for clogs when possible. [Photos (A-F) used by permission of Allegheny County Health Department (2018).]
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Supplemental Figure 4: Mosquito breeding site inspection form
The form used during residential inspections to record data from the inspections. Each location required an address, the violation (i.e., the potential mosquito breeding site), the type of outreach conducted, if any, and additional notes. [Used by permission of Allegheny County Health Department (2018)]
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This is one of the pamphlets (Purchased from Allen Wayne ltd. by the Allegheny County Health Department) which was distributed as public outreach to inspected sites with violations (i.e., mosquito breeding sites). The pamphlet provides information for the elimination of potential mosquito breeding sites and personal protection from mosquitoes.
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This is the other pamphlet (from the Pennsylvania Department of Environmental Protection) which was distributed as public outreach to inspected sites with violations (i.e., mosquito breeding sites). This pamphlet is specific to Aedes albopictus. The outside cover gives examples of potential mosquito breeding sites and instructions on how to eliminate them (A). The inside cover provides information on the life cycle of the mosquito and possible protective measures against mosquito bites, including insect repellents (B).
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This is an example of a notice of violation that was sent during the outreach arm of the project if residential properties had not removed mosquito breeding sites found on the first inspection. It included the date of the initial inspection, the violation observed, and the date of a future inspection before which the resident was expected to comply. [Used by permission of Allegheny County Health Department (2018)]
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-----------------------
CHASING THE TIGER
A STUDY ON THE SPREAD AND CONTROL OF THE ASIAN TIGER MOSQUITO, AEDES ALBOPICTUS
by
Patrick Aloysius Kapfhammer
BS Biology, Robert Morris University, 2016
Submitted to the Graduate Faculty of
the Department of Infectious Diseases and Microbiology
Graduate School of Public Health in partial fulfillment
of the requirements for the degree of
Master of Public Health
University of Pittsburgh
2018
UNIVERSITY OF PITTSBURGH
GRADUATE SCHOOL OF PUBLIC HEALTH
This essay is submitted
by
Patrick Aloysius Kapfhammer
on
December 10, 2018
and approved by
Essay Advisor:
Jeremy Martinson, DPhil
Assistant Professor
Infectious Diseases and Microbiology
Graduate School of Public Health
University of Pittsburgh
Essay Readers:
Martha A Terry, PhD
Associate Professor
Behavioral and Community Health Sciences
Graduate School of Public Health
University of Pittsburgh
William Todaro, MS
Allegheny County Entomologist
Allegheny County Health Department
Pittsburgh, Pennsylvania
Copyright © by Patrick Aloysius Kapfhammer
2018
Jeremy Martinson, DPhil
CHASING THE TIGER
A STUDY ON THE SPREAD AND CONTROL OF THE ASIAN TIGER MOSQUITO, AEDES ALBOPICTUS
Patrick Aloysius Kapfhammer, MPH
University of Pittsburgh, 2018
Supplemental Figure 2: Examples of Egg Counting, Larvae Rearing, and Identification
Supplemental Figure 3: Examples of mosquito breeding sites
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Supplemental Figure 6: Pamphlet distributed as outreach
Supplemental Figure 7: Notice of violation example
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