Common Components of Vector-Borne Infectious Disease Outbreaks. Ned Hayes, M.D. Centers for Disease Control and Prevention

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1 Common Components of Vector-Borne Infectious Disease Outbreaks Ned Hayes, M.D. Centers for Disease Control and Prevention

2 Common Components of Outbreaks Increase in disease incidence compared to background Disease affects a particular sub-population If whole population affected then this is not an outbreak but rather a pandemic Sub-population can be people of a particular age, sex, location, occupation; or participants in some healthcare procedure, recreational activity, group event Increase in disease is caused by a modifiable risk factor, which is defined through epi investigation

3 Common Components of Infectious Disease Outbreaks Etiologic agent is infectious: helminth, arthropod, protozoa, bacteria, virus, rickettsia, prion Route of infection can usually be determined based on epidemiology of outbreak or biology of organism Control and prevention based on eliminating infectious agent, disrupting mechanism of transmission, or provoking host defense (vaccination)

4 Common Components of Vector-Borne Disease Outbreaks Etiologic agent is transmitted to humans by a living vector: in this context, an arthropod Other mechanisms of transmission sometimes operative for the same agent, same outbreak Environmental conditions (temperature, rain, humidity, abundance of zoonotic hosts for vector) often impact intensity of transmission Human behavior (exposure patterns, protective behavior, vector control) impacts intensity of transmission Prevention usually focuses on the vector

5 Principles of Outbreak Investigation Determine that outbreak exists Categorize by TIME, PERSON, PLACE Establish surveillance Collect and test diagnostic samples Formulate hypotheses Test hypotheses with epidemiologic study Implement prevention Communicate results

6 Investigation of Vector-borne Disease Outbreaks Apply basic principles of outbreak investigation Determine presence, abundance, ecology of the vector Determine reservoirs of infection Evaluate modes of transmission Evaluate effects of environmental changes Implement control and prevention

7 Black Death in the Andes

8 An Outbreak of Plague, 1998 March, 1998: 12 sudden deaths reported in small rural town in Chimborazo Province, Ecuador Index case: 13 year-old girl had handled sick guinea pigs (Cavia porcella). Mother, father died several days later then 9 other extended family April: 12 year-old girl died in nearby village, had also handled guinea pigs May: CDC invited to assist Ecuador s Ministry of Health in the investigation

17 Results Poor healthcare access: high mortality Three contacts of index case had antibody to Y. pestis Lung tissue from 2 fatalities positive for Y. pestis antigen 5/14 dogs had antibody to Y. pestis One field mouse (Akodon sp.) had antibody Tiamastus cavicola and Pulex irritans fleas were collected (not from index household)

18 Conclusions: Plague Ecuador Plague outbreak began with exposure to sick guinea pigs then human to human transmission Tiamastus cavicola probably inefficient vector, uncertain role of Pulex irritans? Positive dog, infected Akodon sp. (field mouse) suggests recent rodent epizootic 1997 El Niño, harvesting of Pinus radiata, influence on rodent population dynamics, contact with guinea pigs?

19 Prevention? Educate the people in the villages? Changes in housing? Beds? Food storage practices? Animal pens? Access to healthcare? Flea control?

20 Dengue in Mexico: Cooling the Unpleasant Egyptian Mosquito

21 Does global warming increase the risk of dengue transmission in the United States?

22 Texas Mexico 1999

23 Household Survey 622 household surveys 313 in Nuevo Laredo 309 in Laredo 516 blood samples 288 from Nuevo Laredo residents 228 from Laredo residents

24 Seroprevalence of Antibody Against Dengue Virus in Nuevo Laredo and Laredo, 1999 Antibody Mexico(%) U.S.(%) IgM % CI ( ) (0-2.8) IgG % CI ( ) ( )

25 Mosquito Larvae Results Mexico U.S. House Index 25% 37% Breteau Index 38 91

26 Housing Characteristics Mexico (%) U.S.(%) Central AC * Room AC * Evaporative cooler * Screens * Intact screens * # occupants * *P<0.01 Air conditioning: IgM seropositive O.R ( )

28 Tularemia: Mowing the Vineyard

29 Tularemia: Mode of Transmission Can be transmitted by: Arthropod Direct contact Inhalation Ingestion Animal bite Person-to-person transmission not documented

30 Tularemia Outbreak, Martha s Vineyard, Mass. Summer, adults with pneumonic tularemia All male Median age: 43 yrs (range: yrs) 1 fatality in a 43 yr old previously healthy male; F. tularensis type A isolated; no healthcare insurance Many had mowed lawns or used a brush cutter before illness

31 Properties Where Patients Cut or Mowed Vineyard Haven Oak Bluffs West Tisbury Edgartown Chilmark 1978 Outbreak

32 Properties Where Patients Cut or Mowed Vineyard Haven Oak Bluffs 2000 Outbreak West Tisbury Edgartown Chilmark 1978 Outbreak

34 Mowing and Environmental Samples Cultures were negative for: 3 lawn mower filters 15 grass cutting samples 11 air samples 3 raw water samples 9 soil and mulch samples PCR negative

36 Trapping Results 40 animals trapped 2 seropositive 1 striped skunk (Mephitis mephitis) 1 Norway rat (Rattus norvegicus) All culture negative All DFA negative

37 Logistic Regression Potential Risk Factor AOR 95% CI p-value Used lawnmower or brush-cutter 6.7 (1.1, 39.9) 0.04 Worked with bark 5.1 (0.7, 39.8) 0.12 Average hours outside 1.1 (0.8, 1.4) 0.59 Smoked in last 2 wks 3.0 (0.6,14.7) 0.18 Dog at MV residence 2.4 (0.4, 14.4) 0.33

38 Conclusions: Tularemia 2000 Second U.S. outbreak of pneumonic tularemia First time mowing and brush-cutting found to be risk factors Small mammals presumably contaminated foliage with F. tularensis, then aerosolized Single fatality had limited access to healthcare Ecologic determinants of transmission remain unknown

39 Investigation of Vector-borne Disease Outbreaks Apply basic principles of outbreak investigation Determine presence, abundance, ecology of the vector Determine reservoirs of infection Evaluate modes of transmission Evaluate effects of environmental changes Implement control and prevention

40 Apply Basic Principles of Outbreak Investigation Time, Person, Place Clinical Diagnosis, Collection of Samples Establish Surveillance Laboratory Diagnostics Formulate and Test Hypotheses

50 Determining Vector Ecology and Abundance

56 Determine Reservoirs of Infection

61 Evaluate Modes of Transmission

62 James Carroll, Jesse Lazear, Aristedes Agramonte

64 CUMULATIVE PROBABILITY OF B. burgdorferi TRANSMISSION FOR EACH HOUR ATACHED 1.0 PROBABILITY T = (1 - exp[-λ γ (t - G) γ ] ) k WEIBULL MODEL HOURS ATTACHED From DesVignes et al

65 Evaluate Effects of Environmental Change

66 DRAFT Hybrid Unsupervised Classification with Unsupervised Cluster Busting of the July 2, 2000 image using bands 4,3,2 ERDAS Imagine 8.4

68 15 West Nile Neuroinvasive Disease Cases, Louisiana (Three-Day Moving Average) Number of Cases 10 5 Hurricane Katrina (August 29, 2005) Aug Sep Oct Week of Onset

69 Implement Control and Prevention

73 Common Components of Vector-Borne Disease Outbreaks Etiologic agent is transmitted to humans by a living vector: in this context, an arthropod. Other mechanisms of transmission sometimes operative for the same agent, same outbreak Environmental conditions (temperature, rain, humidity, abundance of zoonotic hosts for vector) often impact intensity of transmission. Human behavior (exposure patterns, protective behavior, vector control) impacts intensity of transmission. Prevention usually focuses on the vector.

74 Acknowledgments Dan O Leary Rusty Enscore Mark Duffy Joe Piesman Barry Miller Ken Gage Kevin Griffith Hannah Gould

Disease Transmission Methods

Disease Transmission Methods In epidemiology, transmission simply means any method by which an infectious agent is spread from one host to another. Knowing the type of pathogen often, but not always, identifies