The Great Border Mosquito Massacre (or Dengue and Dengue Hemorrhagic Fever at the TX-MX Border)

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The Great Border Mosquito Massacre (or Dengue and
Dengue Hemorrhagic Fever at the TX-MX Border)

• Mary Hayden
• Research Review
• October 4, 2007

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Presentation Outline

• Recent History of Dengue in Mexico/South Texas
• 2005 Outbreak Investigation
• Methods
• Results
• Current Study

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Dengue Fever (DF) and Dengue Hemorrhagic Fever
(DHF)

• Flavivirus transmitted by Aedes mosquitoes
• Disease characterized by sudden onset of headache
  fever myalgia anorexia - arthralgia
• Endemic in tropics
• Increasing incidence worldwide
• Estimated 50-100 million dengue infections
  annually

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Aedes aegypti and Dengue Fever

• Aedes aegypti is the principal vector of yellow
  fever and the dengue viruses.
• Peri-domestic, day-biting mosquito which breeds
  in and around humans
• Prefers to breed in artificial containers such as
  vases, pet dishes, 55 gallon drums

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Study Region - Matamoros, MX and Brownsville, TX
Matamoros
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Dengue in South Texas

• 4 outbreaks with local transmission

Year Cases Serotype
1980 27 1
1986 9 1
1995 7 2,4
1999 17 3

Hafkin B. Am J Trop Med Hyg 1982 31(6),
1222-8 Gubler D. "Dengue and Dengue Hemorrhagic
Fever." Tropical Infectious Diseases. 2nd
ed. MMWR 199645(39)841-4 MMWR 2000 5057-9
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Cases of Dengue Fever and Dengue Hemorrhagic
Fever (DHF) Reported in Tamaulipas, Mexico from
2000 to 2006
Year No. dengue cases No. DHF cases Total no. of dengue cases Percent DHF
2000 219 5 224 2.2
2001 47 0 47 0
2002 147 5 152 3.3
2003 9 1 10 10.0
2004 99 9 108 8.3
2005 5230 1832 7062 25.9
2006 151 46 197 23.4
Source Boletín Epidemiolgía Spanish. México,
D.F. Dirección General de Epidemiología, 2001
2007. Available at http//www.dgepi.salud.gob/mx/
boletin.
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Methods

• Two stage cluster sample design (WHO) -
  systematically selected census tracts after
  ordering by socioeconomic status (SES) and then
  randomly selected households from within the
  sampled census tract
• Household-level
• Questionnaire with travel history
• Blood samples
• Entomological survey
• Serology testing
• Results were weighted to reflect each
  individuals chance of selection in the sample.

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Seroprevalence of anti-dengue IgM and IgG
Antibodies by City
Matamoros Brownsville
Households participating 111 (78 of total visited) 118 (73 of total visited)
Serum Samples n 132 n 141
Immunoglobulin M (IgM) positive 22.8 (13.3 to 32.3) n 30 2.5 (0 to 5.4) n 4
Immunoglobulin G (IgG) positive 76.6 (64.788.5) n 101 38.2 (26.749.8) n 47
Weighted point estimate and (95 confidence
interval).
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Spatial Distribution of IgM Positive Participants
Brownsville
Matamoros

IgM Positive IgM Negative
Source Rafael Moreno, U. Colorado
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Select Housing Characteristics of Participants
by City

• Characteristic Matamoros Brownsville
• Central A/C 4 46
• Room A/C 27 40
• Intact screens 65 61
• Mean no. occupants/home 5.4 5.0
• Mean distance to neighbors (m) 3.8 10.8
• Mean lot size (m2) 307 1070

Weighted point estimates
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Mosquito Larval Indices by City
Matamoros Matamoros Brownsville Brownsville
Ae. aegypti Ae. aegypti or Ae. albopictus Ae. aegypti Ae. aegypti or Ae. albopictus
Breteau index (containers/100 houses) 27.6 - 10.8 15.8
House index houses infested 17.4 - 8.6 14.4
Container index with water infested 4.7 - 2.4 3.5
Weighted data
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Human-Environmental Interaction and the Effect of
Waste Tire Removal on Risk for Dengue Fever
Infection in Brownsville, TX and Matamoros, MX.
Funded by Pan American Health Organization EPA
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Brownsville, TX and Matamoros, MX

• Assess human health-environmental factors,
  specifically the effect of waste tire proximity
  on human-vector contact through measurement of
  mosquito indices
• Evaluate Ae. aegypti and Ae. albopictus
  resistance to a widely utilized organophosphate
  temephos
• Qualitatively evaluate household level perception
  of risk of dengue transmission from waste tires
  and options for control

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Rio Bravo
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Toxorhynchites
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Tire Interventions
Piles AB Piles CD Piles EF
Brownsville Toxorhynchites Toxorhynchites Mesocyclops longesitus No treatment
Matamoros Altosid (chemical intervention) Mesocyclops longesitus No treatment
Evaluation of intervention will take place the
end of October