the great border mosquito massacre (or dengue and dengue hemorrhagic fever at the tx-mx border) mary...
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The Great Border Mosquito Massacre (or Dengue and Dengue Hemorrhagic
Fever at the TX-MX Border)
Mary HaydenResearch Review
October 4, 2007
Presentation Outline
• Recent History of Dengue in Mexico/South Texas
• 2005 Outbreak Investigation
• Methods
• Results
• Current Study
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
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
Study Region - Matamoros, MX and Brownsville, TX
Matamoros
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 1996;45(39);841-4 MMWR 2000; 50:57-9
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.
Cases of Dengue Fever and Dengue Hemorrhagic Fever (DHF)
Reported in Tamaulipas, Mexico from 2000 to 2006
050
100
150
Num
ber
of c
ases
8 Jan
15 22 29
5 Feb
12 19 265 M
ar
12 19 26
2 Apr
9 16 23 30
7 May
14 21 28
4 Jun11 18
25
2 Jul
9 16 23
30
6 Aug
13 20 27
3 Sep
10 17 24
1 Oct
8 15 22 29
5 Nov
12 19 263 D
ec
10 17 24 31
MatamorosCameron County
Cases of dengue by week of report, Matamoros (Mexico) and Cameron County, TX, 2005
Serosurveys,5-15 Dec
Autochthnous DHF,Cameron County
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 individual’s chance of selection in the sample.
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%
(64.7—88.5)*
n = 101
38.2%
(26.7—49.8)*
n = 47
* Weighted point estimate and (95% confidence interval).
Spatial Distribution of IgM Positive Participants
Brownsville
Matamoros
IgM Positive
IgM Negative
Source: Rafael Moreno, U. Colorado
Select Housing Characteristics* of Participants by City
Characteristic Matamoros BrownsvilleCentral 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
Matamoros Brownsville
Ae. aegypti
Ae. aegypti or
Ae. albopictusAe.
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
Mosquito Larval Indices* by City
* Weighted data
Tires 31.9%Tires 25.8%
Buckets 23.3%Buckets 23.6%
Other 19.1%Other 18.4%
Drums 16.7%
Drums 2.5%
Flower pots 16.3%
Plastic lids 13.3% Plastic lids 6.0%
Cisterns 3.0%
Containers infested with Aedes species mosquito immatures, by weighted proportion of container type, Brownsville and Matamoros—December, 2005
Brownsville Matamoros
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 OrganizationEPA
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
Rio Bravo
Toxorhynchites
Monthly Precipitation for Brownsville, TX for 2005 and 2007
01
23
45
6
1 2 3 4 5 6 7 8 9 10 11 12
Monthly Precipitation
Pre
cipi
tatio
n in
ches
2005
2007
Normal
Tire Interventions
Piles A+B Piles C+D Piles E+F
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