the great border mosquito massacre (or dengue and dengue hemorrhagic fever at the tx-mx border) mary...

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