Presentation on theme: "The Great Border Mosquito Massacre (or Dengue and Dengue Hemorrhagic Fever at the TX-MX Border) Mary Hayden Research Review October 4, 2007."— Presentation transcript:
The Great Border Mosquito Massacre (or Dengue and Dengue Hemorrhagic Fever at the TX-MX Border) Mary Hayden Research 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# CasesSerotype 1980271 198691 199572,4 1999173 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
YearNo. dengue cases No. DHF casesTotal no. of dengue cases Percent DHF 200021952242.2 2001470 0 200214751523.3 2003911010.0 20049991088.3 2005 52301832706225.9 200615146197 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
0 50 100 150 Number of cases 8 Jan152229 5 Feb 1219265 Mar1219262 Apr9162330 7 May 1421284 Jun1118 25 2 Jul91623 30 6 Aug 132027 3 Sep 1017241 Oct81522295 Nov1219263 Dec10172431 Matamoros Cameron 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 MatamorosBrownsville Households participating 111 (78% of total visited) 118 (73% of total visited) Serum Samplesn = 132n = 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 Brownsville Central A/C 4% 46% Room A/C 27% 40% Intact screens65% 61% Mean no. occupants/home5.4 5.0 Mean distance to neighbors (m)3.8 10.8 Mean lot size (m 2 )3071070 * Weighted point estimates
MatamorosBrownsville Ae. aegypti or Ae. albopictus Ae. aegypti or Ae. albopictus Breteau index (containers/100 houses) 27.6 - 10.815.8 House index % houses infested 17.4 - 8.614.4 Container index %with water infested 4.7 - 2.43.5 Mosquito Larval Indices* by City * Weighted data
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
Tire Interventions Piles A+BPiles C+DPiles E+F BrownsvilleToxorhynchitesToxorhynchites + Mesocyclops longesitus No treatment MatamorosAltosid (chemical intervention) Mesocyclops longesitus No treatment Evaluation of intervention will take place the end of October