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Vector Hazard Report: Zika Virus in Puerto Rico, August 2016

Vector distributions, taxonomic characters and bionomics

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Table of ContentsI. Background: Zika Virus in Puerto Rico

1) Zika Virus Cases in Puerto Rico2) Notes on the Biology of Zika Virus Vectors

II. Zika Virus Vectors1) Species Page: Aedes (Stg.) aegypti2) Taxonomic Characters: Aedes (Stg.) aegypti (Head and Thorax)3) Taxonomic Characters: Aedes (Stg.) aegypti (Legs and Wings)4) Species Page: Aedes (Stg.) albopictus5) Taxonomic Characters: Aedes (Stg.) albopictus (Head and Thorax)6) Taxonomic Characters: Aedes (Stg.) albopictus (Legs and Wings)

III. Climate MapsIV. Month of Maximum Temperature/ PrecipitationV. Habitat Suitability Aedes (Stg.) aegyptiVI. Habitat Suitability Aedes (Stg.) albopictusVII.Habitat Suitability and Human Population Aedes (Stg.) aegyptiVIII.Habitat Suitability and Human Population: Aedes (Stg.)

albopictusIX. Puerto Rico Insecticide Resistance Testing: Aedes (Stg.) aegyptiX. References

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Zika Virus in Puerto Rico: BackgroundThe first locally transmitted case of Zika virus in Puerto Rico was reported on December 31, 2015. According to the CDC, as of August 10, 2016 there have been 6,475 locally transmitted cases of Zika reported from 77 of Puerto Rico’s 78 districts. Since the outbreak began 2 deaths have been attributed to Zika virus in Puerto Rico. Travelers to Puerto Rico are advised to remain alert and practice enhanced precautions due to the ongoing outbreak.

Historically, other arbovirus outbreaks reported from Puerto Rico have an increased number of cases in the late summer and fall (August to September), which are the hottest and wettest months of the year in PR (Sharp et al. 2010, Sharp et al. 2014).

In Puerto Rico, the primary vector of Zika virus is Aedes aegypti (yellow fever mosquito). Although a competent vector of other arboviruses like dengue and chikungunya, Aedes albopictus (Asian Tiger Mosquito) is considered a suspected vector of Zika virus as well. Of these two mosquito species, Ae. aegypti is more closely associated with man, preferring to lay eggs in human containers near human dwellings making it a much more effective vector of disease.

A number of studies have attempted to classify larval breeding sites of Aedes aegypti, the primary vector of Zika virus in Puerto Rico. Of these studies, the breeding sites listed below are identified as the most productive for Ae. aegypti larvae. (Barrera et al. 2006a, Barrera et al. 2006b, Barrera et al. 2011)

• Buckets (small and large)• Barrels• Water Meters• Plant pots• Plastic covers containing water• Tires• Plastic pools

There is evidence that the most productive larval habitats in PR are human containers that are not managed by humans, whether they be trash or other unattended objects around homes (Barrera et al. 2011).

Zika Virus Prevention: Summary for General Public in Puerto Rico, CDC as of August 2016.

Zika Virus 101, CDC as of August 2016.

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Municipality of residence of persons with confirmed and presumptive Zika virus infection (n = 4,986) — Puerto Rico, November 1, 2015–July 7, 2016. (596 additional cases were reported in persons with unknown municipality of residence) Source: CDC 8/10/2016 http://www.cdc.gov/mmwr/volumes/65/wr/mm6530e1.htm?s_cid=mm6530e1_w

Cases of confirmed and presumptive Zika virus infection (N = 5,582), by pregnancy status and week of illness onset or specimen collection, and percentage of persons with test results positive for Zika virus — Puerto Rico, November 1, 2015–July 7, 2016Source: CDC 8/10/2016 http://www.cdc.gov/mmwr/volumes/65/wr/mm6530e1.htm?s_cid=mm6530e1_w

Centers for Disease Control and Prevention (CDC) Update: Ongoing Zika Virus Transmission — Puerto Rico, November 1, 2015–July 7, 2016. Weekly / August 5, 2016 / 65(30);774–77. Morbidity and Mortality Weekly Report (MMWR)

Zika Virus Cases: Puerto Rico

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Notes on the Biology of Zika Virus Vectors

Aedes aegypti and Aedes albopictus, the primary vectors of dengue, chikungunya & Zika viruses, are originally of African and Asian origin, respectively. The spread of these two species around the world in the past 50 years is well documented and facilitated by a unique life trait: their eggs can survive desiccation. This trait allows eggs laid by these species to travel undetected in receptacles like used tires, or lucky bamboo plants, which are distributed throughout the world. When these receptacles are wetted (e.g. by rain), the larva emerge and grow to adults in their new environment. In temperate or tropical environments conditions are highly suitable for populations to quickly become established, as these mosquitoes have done in Brazil and nearly every other country in North, Central and South America.

Compounding this problem is that these mosquito species are capable of ovarian viral transmission – meaning that if the mother is infected with a virus, she can potentially pass it on to her offspring through her eggs. Each female mosquito lays 100-120 eggs, every 4-5 days (c.4-8 times in her life time of 1-3 months), and if she is infected, all her offspring emerge ready to infect the first person they bite. Reducing exposure of infected people to mosquitoes

Reducing the exposure of infected people to mosquitoes requires the widespread availability of rapid diagnostic tests, effective treatment and most importantly, containment of the patients. Given that there is currently no vaccine or effective treatment for Zika virus, reducing the opportunity for mosquitoes to bite infected people is critical in slowing the continued spread of the disease.

CDC Guidance on Zika VirusCDC Dengue and Chikungunya in Our Backyard:

Preventing Aedes Mosquito-Borne DiseasesCDC Preventing Aedes Mosquito-Borne Disease

CDC DEET FactsheetWHO Zika Virus Background

WHO Microcephaly/Zika virusU.S. EPA Controlling Mosquitoes at the Larval Stage

Further guidance on protecting yourself from the Zika Virus:

(L) Aedes aegypti, (R) Aedes albopictus. Images taken by J. Stoffer, Walter Reed Biosystematics

Unit

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Aedes (Stg.) aegypti (Linnaeus, 1762)

Bionomics:In association with man, Ae. aegypti will use any and all natural and artificial containers as larval breeding sites. Away from urban areas the species tends to favor pools in river beds, tree stumps, tree holes and natural containers. Females are primarily day biters and readily enter buildings to feed. They have also been taken in lesser numbers at night (Christophers 1960).

Medical Importance:Primary vector of Yellow Fever, Dengue Fever, Chikungunya Virus and Zika Virus (Christophers 1960).

WRBU Mosquito Catalog Species Page

Identification Keys:Rueda, Leopoldo M. 2004. Pictorial keys for the identification of mosquitoes (Diptera: Culicidae) associated with dengue virus transmission. Walter Reed Army Institute of Research Washington DC Department of Entomology.

Gjullin, C. M. 1946. A key to the Aedes females of America north of Mexico (Diptera, Culicidae)." Proc. Ent. Sot. Washington. Vol. 48.

Distribution:

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Ae. aegypti Head: dorsal view

Ae. aegypti (F)Head: lateral view

Ae. aegypti (F) Thorax: dorsal view

Images also found at wrbu.si.edu

Taxonomic Characters: Aedes (Stg.) aegypti (Linnaeus, 1762)

Ae. aegypti (F)Thorax: lateral view

Ae. aegypti Thorax: lateral view

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Ae. aegypti Wing: dorsal view

Ae. aegypti Abdomen: dorsal view

Ae. aegypti Wing: lateral view

Ae. aegypti Foreleg

Ae. aegypti Midleg

Ae. aegypti Hind leg

Ae. aegypti Hind tarsi

Taxonomic Characters: Aedes (Stg.) aegypti(Linnaeus, 1762)

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Aedes (Stg.) albopictus (Skuse, 1894)

Bionomics:Larval Ae. albopictus are found in natural containers, including tree holes, bamboo stumps, coconut shells, rock holes, palm fronds, and leaf axils. They are also found in all varieties of artificial containers and will breed indoors. Females readily bite man (Huang 1972).

Medical Importance:Vector of dengue and yellow fever in the wild. Under laboratory conditions: bird malarias, Eastern and Western equine encephalitis, West Nile, Zika, Chikungunya and Japanese encephalitis viruses (Huang 1972).

WRBU Mosquito Catalog Species Page

Identification Keys:Rueda, Leopoldo M. 2004. Pictorial keys for the identification of mosquitoes (Diptera: Culicidae) associated with dengue virus transmission. Walter Reed Army Institute of Research Washington DC Department of Entomology.

Gjullin, C. M. 1946. A key to the Aedes females of America north of Mexico (Diptera, Culicidae)." Proc. Ent. Sot. Washington. Vol. 48.

Distribution:

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Ae. albopictus (F) Head: lateral view

Ae. albopictus (F) Thorax: dorsal view

Taxonomic Characters:Aedes (Stg.) albopictus (Skuse, 1894)

Ae. albopictus (F) Thorax: lateral view

Images also found at wrbu.si.edu

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Ae. albopictus Wing: dorsal view

Ae. albopictus Abdomen: dorsal view

Ae. albopictus Abdomen: lateral view

Ae. albopictus Foreleg

Ae. albopictus Midleg

Ae. albopictus Hind leg

Ae. albopictus Hind tarsi

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Taxonomic Characters:Aedes (Stg.) albopictus (Skuse, 1894)

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Consistent Above and Below Average PrecipitationAreas with consistent above average monthly rainfall over the past 3 months may indicate increased mosquito breeding sites which may lead to increased mosquito-borne disease transmission. Areas with consistent below average rainfall may also indicate increased water storage or ponding which can provide additional habitat for mosquito species that lay eggs in human containers, protected micro environments, or long lasting pools. Updated monthly. -NASA Earth Observations.

Temperature anomalyThis map shows where earth’s temperatures were warmer or cooler in the daytime for the past month than the average temperatures for the same month from 2001-2010. Updated monthly. -NASA Earth Observations

Land Surface TemperatureThis map shows the temperature of the earth’s lands during the daytime. Updated monthly.-NASA Earth Observations

Drought Breaking RainAreas receiving above average rainfall for the past month and below average rainfall for the previous 12 months. Drought breaking rain may indicate recent suitable conditions for vectors and diseases in a stressed environment or human population. Updated monthly. -WorldClim, Giovanni online data system NASA GES DISC, Tropical Rainfall Measuring Mission (TRMM).

Climate MapsClick on an image to view the near-real time maps described below

Rainfall This map shows the accumulated rainfall for the past month. Updated monthly. -NASA Earth Observations

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National Oceanic and Atmospheric Administration (NOAA)Get current weather conditions, hazards, forecasts and radar updated daily. -NOAA

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Month of maximum precipitation compiled from the 50 year

average of the WorldClim dataset.

Month of Maximum Precipitation and Temperature: Puerto Rico

Month of maximum temperature compiled from the 50 year

average of the WorldClim dataset.

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Geographic Distribution: Ae. aegypti

Boosted regression tree model of habitat suitability for Ae. aegypti, Puerto Rico. Kraemer

et al. 2015

Boosted regression tree model of habitat suitability for Ae. aegypti, Global. Kraemer et al.

2015

VectorMap data points for Ae. aegypti, Global. 21, 768 records as of August 2016.

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Geographic Distribution: Ae. albopictus

Boosted regression tree model of habitat suitability for Ae. albopictus, Puerto Rico.

Kraemer et al. 2015

Boosted regression tree model of habitat suitability for Ae. albopictus, Global. Kraemer et

al. 2015

VectorMap data points for Ae. albopictus, Global.

37, 426 records as of August 2016. Back to Table of Contents

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Habitat Suitability and Human Population: Aedes aegypti

Human Population Density, LandScan2011

Ae. aegypti habitat suitability, Kraemer et al. 2015

Methods:Zonal statistics/histogram analyses of buffered collection locations against the LandScan (2011) population density raster (Ispop2011) showed that despite the high frequency of pixels of 51-100 people/sq km, the majority of Ae. albopictus and Ae. aegypti positive locations occurred in the categories 101-500 and 501-2500 people/sq km. Aedes aegypti appears more often than Ae. albopictus in denser human habitats but as these are of such low frequency considering the whole they were discounted for the purposed of these figures. Therefore we created a polygon of the population raster for density 101-2500 then converted this to points (Data Management Tools>Features>Feature to point). This was necessary because some polygons are not counted when trying to extract elements of the population raster. Then we used Spatial analyst tools>Extraction>Extract by Mask to reveal instances where both conditions (>50% chance of the vector species and 101-2500 people) occurred.

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Habitat Suitability and Human Population: Aedes albopictus

Human Population Density, LandScan2011

Ae. albopictus habitat suitability, Kraemer et al. 2015

Methods:Zonal statistics/histogram analyses of buffered collection locations against the LandScan (2011) population density raster (Ispop2011) showed that despite the high frequency of pixels of 51-100 people/sq km, the majority of Ae. albopictus and Ae. aegypti positive locations occurred in the categories 101-500 and 501-2500 people/sq km. Aedes aegypti appears more often than Ae. albopictus in denser human habitats but as these are of such low frequency considering the whole they were discounted for the purposed of these figures. Therefore we created a polygon of the population raster for density 101-2500 then converted this to points (Data Management Tools>Features>Feature to point). This was necessary because some polygons are not counted when trying to extract elements of the population raster. Then we used Spatial analyst tools>Extraction>Extract by Mask to reveal instances where both conditions (>50% chance of the vector species and 101-2500 people) occurred.

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Insecticide Resistance testing ofAedes aegypti in Puerto Rico:

Results of CDC Bottle Assay Tests on Aedes aegypti mosquitoes in Puerto Rico, February 2016 to present. Testing conducted in 23 of the 78 districts of Puerto Rico. Resistance was found in other insecticides as well, full results can be found here:

http://www.cdc.gov/zika/vector/insecticideresistancetesting.html

Additional References for Insecticide Resistance by Zika Virus Vectors:

Aguirre-Obando, Oscar A., et al. 2015. Insecticide resistance and genetic variability in natural populations of Aedes (Stegomyia) aegypti (Diptera: Culicidae) from Colombia. Zoologia (Curitiba) 32.1: 14-Aponte, H. Angélica, et al. 2013. The pyrethroid resistance status and mechanisms in Aedes aegypti from the Guerrero state, Mexico. Pesticide Biochemistry and Physiology 107.2: 226-234Bisset, J. A., et al. 2013. Insecticide resistance in two Aedes aegypti (Diptera: Culicidae) strains from Costa Rica. Journal of medical entomology 50.2: 352-361Burnett, G. F., and L. H. Ash. 1961. The susceptibility to insecticides of disease-carrying mosquitos in Fiji. Bulletin of the World Health Organization 24.4-5: 547Liu, Huqi, et al. 2004. Insecticide resistance in Alabama and Florida mosquito strains of Aedes albopictus. Journal of medical entomology 41.5: 946-952Macoris, Maria de Lourdes G., et al. 2012. Resistance of Aedes aegypti from the state of São Paulo, Brazil, to organophosphates insecticides. Memórias do Instituto Oswaldo Cruz 98.5: 703-708Marcombe, Sébastien, et al. 2014. Insecticide resistance status of United States populations of Aedes albopictus and mechanisms involved. PloS one 9.7: e101992Vontas, J., et al. 2012. Insecticide resistance in the major dengue vectors Aedes albopictus and Aedes aegypti. Pesticide Biochemistry and Physiology104.2: 126-131World Health Organization. 1992. Vector resistance to pesticides: fifteenth report of the WHO Expert Committee on Vector Biology and Control [meeting held in Geneva from 5 to 12 March 1991]

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References

1. Barrera, Roberto, Amador Manuel & Clark, Gary G. 2006. Ecological Factors Influencing Aedes aegypti (Diptera: Culicidae) Productivity in Artificial Containers in Salinas, Puerto Rico. Journal of Medical Entomology 43(3): 484-492

2. Barrera, Roberto, Amador Manuel & Clark, Gary G. 2006. Use of The Pupal Survey Technique for Measuring Aedes aegypti (DIPTERA: CULICIDAE) Productivity IN Puerto Rico. Am. J. Trop. Med. Hyg., 74(2): 290–302

3. Barrera R, Amador M, MacKay AJ (2011) Population Dynamics of Aedes aegypti and Dengue as Influenced by Weather and Human Behavior in San Juan, Puerto Rico. PLoS Negl Trop Dis 5(12)

4. Cheong, W. H. 1967. Preferred Aedes aegypti Larval Habitats in Urban Areas. Bulletin of the World Health Organization. 36: 586-589

5. Kraemer, Moritz et al. 2015. The global distribution of the arbovirus vectors Aedes aegypti and Ae. albopictus. ELife: 4:e08347. DOI: 10.7554/eLife.08347

6. Scott, Priyanie, W., Amerasingheh, Morrison, Amy C., Lorenz, Leslie H., Clark, Gary G., Strickman, Daniel, Kittayapong, Pattamaporn, & Edman, John, D. 2000. Longitudinal Studies of Aedes aegypti (Diptera: Culicidae) in Thailand and Puerto Rico: Blood Feeding Frequency. Journal OF Medical Entomology 37(1): 89-101

7. Sharp TM, Hunsperger E, Santiago GA, et al. 2013. Virus-specific differences in rates of disease during the 2010 dengue epidemic in Puerto Rico. PLoS Negl Trop Dis;7:e2159

8. Sharp TM, Roth NM, Torres J, et al. 2014. Chikungunya cases identified through passive surveillance and household investigations—Puerto Rico, May 5–August 12, 2014. MMWR Morb Mortal Wkly Rep; 63:1121–8

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The Walter Reed Biosystematics Unit is part of the Walter Reed Army Institute of Research and is based at the Smithsonian Institution Museum Support Center. To access taxonomic keys, the

Systematic Catalog of Culicidae or to learn more about WRBU visit wrbu.si.edu

VectorMap is only as good as the data you provide. If you have collection records,

models or pathogen testing results please contact the VectorMap team to learn how

to contribute data at mosquitomap@si.edu.

The published material reflects the views of the authors and should not be construed to represent those of the Department of the Army or

the Department of Defense.

Vector Photos Provided by Judith Stoffer, Walter Reed

Biosystematics Unit

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