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Beware the Bug that Bites You: Local Transmission of Malaria in Loudoun County Virginia. Benita L. Boyer, RN, MS, CIC District Epidemiologist, Loudoun Health District Leesburg, Virginia. November 4, 2003. David Goodfriend & ALL Loudoun County Health Department employees

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Beware the Bug that Bites You: Local Transmission of Malaria in Loudoun County Virginia

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beware the bug that bites you local transmission of malaria in loudoun county virginia

Beware the Bug that Bites You:Local Transmission of Malaria in Loudoun County Virginia

Benita L. Boyer, RN, MS, CIC

District Epidemiologist,

Loudoun Health District

Leesburg, Virginia

November 4, 2003

David Goodfriend & ALL Loudoun County Health Department employees

Loudoun Healthcare, Inc.

Mobile Health Van, Lab, Linda Belmonte (ICP)

Loudoun County Government Services

Fairfax County Health Department

Gloria Addo-Ayensu, Happy Callaway

Infectious Disease Physicians

Antonio Pastor, Henry Rhee

Clarke Environmental Mosquito Management


Dee Pettit, Mary Mismas, Kelly Felkey

VDH Office of Epidemiology

John Marr, David Gaines, Diane Woolard, Suzanne Jenkins, Denise Sockwell

Hospitals B & C - ICPs

Maryland Department of Health and Mental Hygiene

Lynn Frank

Montgomery County (MD) Health Department

Tina Lacey, Yvonne Richards, Carol Garvey

Uniformed Services University of Health Sciences

CDC Malaria Branch

Louise Causer, John MacArthur, Robert Wirtz, Richard Steketee

Medical Analysis Systems, Inc.

Kirti Davé

global impact of malaria
Global Impact of Malaria
  • One of the most common parasitic infections in the world
  • Causes about 1 million deaths each year

New World species

malaria in the united states
Malaria in the United States
  • Arrived in the U.S. through colonists/slaves
  • 1914 - about 600,000 cases
  • 1934 - decreased to 125,000 cases

Zucker. EID. vol 2, no 1, 1996

malaria in the united states5
Malaria in the United States
  • 1950s - Officially eradicated in the U.S.
  • Since then - about 90 cases of domestically acquired malaria
    • Malaria-infected mosquitoes have been foundin NONE of these cases
    • There has been one other case in Virginia in the past 50 years
  • Greater than 1,000 cases of imported malaria diagnosed in the U.S. each year
  • Transmitted to humans by Anopheline mosquitoes
  • Most common species in the eastern U.S.
    • A quadrimaculatus
    • A. punctipennis
  • Humans are the animal hosts for malaria
anopheles quadrimaculatus
Anopheles quadrimaculatus
  • Found in all 48 contiguous states
  • Larvae grow in:
    • permanent fresh water
    • slow streams, ponds, lakes containing surface vegetation
  • Feed at night
    • after dusk/before dawn
  • Rest in hollow trees, underneath buildings
  • Able to overwinter
  • Flight range less than one mile
  • Lay 9 -12 batches of eggs per lifetime
    • 3000 eggs/batch

Mosquitoes of North America by Stanley Carpenter and Walter LaCasse Virginia Mosquito Control Association

diagnosis and treatment
Diagnosis and Treatment
  • Diagnosis:
    • mosquitoes
      • Vectest™
      • ELISA
      • PCR
    • people
      • blood smear
      • PCR
      • serology
  • Treatment:
    • quinine
    • chloroquine
    • primaquine
disease control
Disease Control
  • Modern decreases in malaria cases are attributed to:
    • Draining of swamps
    • Access to medical care
    • Availability of quinine and other anti-malarial medications
    • Population movements away from rural areas
    • Mosquito spraying


loudoun county
Loudoun County
  • Suburb of Washington, DC
  • Population about 220,000
    • with small but rapidly growing Asian and Hispanic populations
  • Bordered by:
    • North - Potomac River and Maryland
    • East - Fairfax County
    • West - West Virginia and Clarke County
    • South - Fauquier and Prince William Counties
  • Dulles International Airport is located on the eastern border of the county
case 1
Case #1
  • August 23, 2002
    • 19 y.o. female from Cascades presented to Health Clinic A with

4-day history of fatigue, fevers, chills, myalgias, sinus pain

    • Dx: Sinus infection
    • Rx: Azithromycin
  • August 27, 2002
    • Returned to Clinic A with no improvement
    • Fever of 103.5o F (39.7°C)
    • Dizziness and Nausea
    • Tachycardia
    • Anemic, with low white blood cell and platelet counts
    • Rx: Levofloxacin
    • Blood smear positive for Plasmodium vivax
  • Treatment:
    • Started on chloroquine (3 days)
    • Switched to primaquine (14 days)
  • Outcome:
    • Complete recovery
case 2
Case #2
  • August 25, 2002
    • 15 y.o. male from Sugarland Run presented to Hospital A ER with

2 weeks of headaches, 4-day history of fever, nausea, vomiting, malaise, nose bleeds

    • Fever of 105°F (40.6°C)
    • Tachycardia, splenomegaly, jaundice
    • Anemic, with low white blood cell and platelet counts
    • Blood smear positive for Plasmodium vivax
  • Treatment:
    • Admitted to hospital
    • Clindamycin
    • Quinine
      • Discontinued due to tinnitus
    • Switched to chloroquine (3 days)
    • Then primaquine (14 days)
  • Outcome:
    • Complete recovery
case 3
Case #3
  • March 16th,2003
    • 19 y.o. female from South Riding presented to Health Clinic B with a 4 day history of fatigue, fevers, chills, severe headaches, malaise, arthralgias, myalgias, nausea, vomiting, and mild abdominal pain
    • Prescribed an antibiotic for ‘sinus’ infection
  • March 18th, 2003
    • Presented to Hospital C ER - no improvement
    • Fever of 102°F (38.9°C)
    • Anemic, with low white blood cell and platelet counts
    • Blood smear positive for Plasmodium vivax
  • Treatment:
    • Admitted to hospital
    • Doxycycline
    • Quinine sulfate
    • Primaquine (14 days)
  • Outcome:
    • Complete recovery
  • Note:
    • Medical record listed patient’s risk factor for malaria as “lives in Loudoun County”
comparison of symptoms
Textbook Symptoms:

Usually 10 -16 days after infection

Episodic high fever

recurs every 2-3 days

Shaking chills


Headaches, muscle aches, malaise

Nausea, vomiting

Anemia and jaundice

May take up to one year to present

Case Symptoms:

4 to 205 days before presentation


Episodic fever


Headaches, muscle aches, malaise

Nausea, vomiting


Anemia and jaundice

Sinus pain

Comparison of Symptoms
human cases epidemiology
Human Cases – Epidemiology
  • Cases 1 & 2 lived about 1 mile apart in eastern Loudoun County
  • Case 3 lived with a family near case 2 until November 2002
  • Socialized after dusk in the same area with same group of teens
  • Area is about 7 miles north of Dulles International Airport

Montgomery County

Selden Island

  • Several weeks prior to becoming sick:
    • they reported being outsideat night within a block of each other
    • received multiple mosquito bites each night
  • Cases 1 & 2 had no history of foreign travel nor of traveling anywhere else together. Case 3 had a half- day trip to Mexico 2 years prior, and travel to Western Europe 4 years before onset
  • Case 3 also fished along the Potomac west of her residence and reported ‘many’ mosquito bites
sugarland run
Sugarland Run
  • Sugarland Run has a large diverse immigrant population
  • Many of the houses had screens that were not intact
  • The area is close to a regional park, which contains multiple potential mosquito breeding grounds
sugarland run19
Sugarland Run
  • A review of the neighborhood found multiple mosquito breeding sites
sugarland run20
Sugarland Run

Residents were educated about the signs and symptoms of malaria by health department staff…

…through community town hall meetings and house-to-house instructions prior to adult mosquito spraying.

  • Mosquito traps placed in the area before spraying caught up to 22 Anopheline mosquitoes per trap
  • Traps placed after spraying for a 1 mile radius around the suspected infection area found 0 to 3 mosquitoes per trap
  • None of the mosquitoes tested positive for malaria

Clarke Mosquito

human surveillance project 1
Human Surveillance – Project 1
  • No additional cases of malaria were found through:
    • A review of patient records at the two local hospitals and local urgent care centers
    • Requests that symptomatic residents be evaluated for malaria by their doctors and reported immediately
infected mosquitoes
Infected Mosquitoes
  • On September 24, 2002 a mosquito trap was placed in the Lansdowne community in response to complaints of nuisance mosquitoes in an area with a population at high risk for complications from West Nile virus

Selden Island

Montgomery County

Potomac River

Lansdowne is about 6 miles west of Sugarland Run

mosquito testing
Mosquito Testing
  • Four A. quadrimaculatus and one A. punctipennis mosquitoes were trapped
  • The A. quadrimaculatus pool tested positive for Plasmodium vivax by VecTest™
  • There was insufficient substrate left for DCLS to confirm the VecTest results by the more traditional PCR testing.
  • The VecTest malaria assay has been on the market since the beginning of 2002
  • It was designed for the military to be an accurate, rapid test for P. vivax and P. falciparum antigens
  • It uses a rapid wicking assay of monoclonal antibodies to specific peptide circumsporozoites

Medical Analysis Systems, Inc.

mosquito testing27
Mosquito Testing
  • In response to this finding, additional traps were placed in the general area
  • On September 27, a pool of three A. quadrimaculatus mosquitoes tested positive for malaria in Broad Run
broad run
Broad Run

Montgomery County

Selden Island

Potomac River

Both mosquito pools were trapped within ¼ mile of Montgomery County, Maryland.

broad run29
Broad Run
  • In response, Montgomery County enlisted the aide of mosquito surveillance teams from the Uniformed Services University of the Health Sciences (USUHS)
  • USUHS trapped mosquitoes in Montgomery County, MD
    • along the Potomac River on the mainland
    • Selden Island
    • Van Deventer Island
selden and vandeventer islands
Selden and VanDeventer Islands

Montgomery County

Selden Island

Potomac River

Two mosquito pools on Selden Island tested positive for malaria by PCR, as did one pool on VanDeventer Island

selden island
Selden Island
  • Selden Island is part of Montgomery County, MD
  • It lies in the Potomac River and:
    • is less than 40 feet from Virginia
    • is accessible only by a bridge from Loudoun County
    • is a popular fishing and recreational area
    • is privately owned and used as a sod farm.
human surveillance project 2
Human Surveillance – Project 2
  • 31 permanent employees worked on Selden Island over the summer
  • Countries of origin:
    • USA: 13
    • South Africa: 1
    • Mexico: 17
      • Central: 15
      • Hidalgo: 11
      • Guanquatro: 3
      • Distrito Federal: 1
      • Southeast: 1
      • Veracruz: 1
      • South: 1
      • Pachuca: 1
  • Workers reported being on the island before dawn and after dusk, and had multiple mosquito bites
  • All workers were screened for malaria:
    • Management at Company A’s headquarters in southeast Loudoun County
    • Workers in the sod fields near Dulles Airport
human surveillance project 233
Human Surveillance – Project 2
  • No employee reported feeling ill
    • Communicable Disease nurse from Montgomery County served as interpreter & administered questionnaire
  • Blood smears drawn on the employees all negative
  • PCR and serology results all negative
fairfax county
Fairfax County
  • An additional mosquito pool tested positive by VecTest™ for malaria near Herndon in Fairfax County
  • This is the only positive A. punctipennis pool and is over 6 miles away both from the Potomac River and where the adolescents were infected
  • The significance of this finding is unknown
  • August 2002
    • 2 Loudoun County adolescents were symptomatic with P. vivax malaria
  • Between September and October 2002
    • 5 traps along the Potomac River captured mosquitoes positive for P. vivax by VecTest, some confirmed by ELISA, none by PCR
  • The positive mosquito pools were located within 2 miles of each other and at least 4 miles from the infected adolescents
  • February 2003 a ‘malaria summit’ was held with all the main players in attendance to review the findings and discuss testing protocols
  • March 2003 a third domestically-acquired human case was identified in a Loudoun County teenager
  • August 2003 mosquito surveillance along the Potomac found a pool of A. punctipennis positive for P.vivax by VecTest, and confirmed by ELISA and PCR.
what does this mean
What Does This Mean?
  • The most likely explanation is that someone infected

with P. vivax abroad spent sufficient time on or near Selden Island to infect the local mosquito population

  • In all previously reported outbreaks, no further cases were reported in subsequent years
  • The VecTest results in 2002 were likely true positives
  • It is likely that mosquitoes infected with malaria have existed along the Potomac River for some time
    • prior to WNV there was no reason to conduct mosquito surveillance
  • There is likely no ongoing propagation of malaria
  • Each year the local mosquito population likely becomes infected by people who contracted malaria abroad
  • The easier it is for people infected with malaria from their original countries to receive treatment, the less likely they will be able to re-introduce the infection into local mosquito populations
    • Social, immigration, and medical access issues
  • Airports receiving planes from endemic areas need to diligently implement disinsection procedures.
public health implications
Public Health Implications?
  • Strategies to:
    • Quickly detect and treat human cases
    • Remove mosquito breeding grounds
    • Ensure intact window screens
  • Educate people to:
    • Use insect repellent containing DEET
    • Wear light, long, loose clothing