MODES of TRANSMISSION

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MODES of TRANSMISSION

• Arthropod-borne
• Food-borne
• Air-borne
• Direct contact
• Sexually transmitted
• Blood-borne
• Water-borne
• Animal-borne
• Soil-borne

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AGENT
T R A N S M I S S I O N M O D E
Virus Bacteria Fungus
Protozoa Helminth
Direct Sexual Blood Food Air Water Animal
Soil Arthropod

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AGENT
T R A N S M I S S I O N M O D E
Virus Bacteria Fungus
Protozoa Helminth
Direct Sexual Blood Food Air Water Animal
Soil Arthropod
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WATER-BORNE DISEASES
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Water-borne Transmission

• May be part of food-borne (e.g. hepatitis A)
• May be exclusively water-borne (e.g. Naeglaria)
• May be animal-borne (e.g. tularemia)
• May be parasitic (e.g. schistosomiasis)
• May be sapronotic (e.g. algal blooms )

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Water-borne diseases
T R A N S M I S S I O N M O D E
Virus Bacteria Fungus
Protozoa Helminth
Direct Sexual Blood Food Air Water Animal
Soil Arthropod
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Elishas cruse and curse
II King 219 c. 1350 BCE
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London, 1854
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Chicago 1932
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Leyte, Philippines, 1944
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Formosa, 1950
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Worcester, Massachussetts, 1969
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Dade County, Florida, 1974
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Milwaukie, Wisconsin, 1993
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Selected Recent Waterborne Outbreaks

• Norovirus Vermont 2004
• Hepatitis E Japan 2003
• Campylobacter Ontario, Canada 2000
• E. coli O157 H7 Wyoming 1998
• Tularemia Louisiana 1997
• Shigellosis Idaho 1995
• Toxoplasmosis British Columbia 1995
• Cholera Burundi 1992-93
• Cryptosporidiosis New Mexico 1986

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Giardiasis
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Cryptosporidiosis
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Cyclosporidiosis
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Isosporidiosis
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Naegleriasis, Acanthamoebiasis and
Balmuthiasis (Free Living Ameba)
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Schistosomiasis
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Swimmers Itch
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Case Study Nicaragua 1995
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Background

• October 1995 clinics in Achuapa and El Sauce,
  Nicaragua report an increase in patients with
  febrile illness and headache, musculoskeletal
  pain, hemorrhagic manifestations, and shock WITH
• - 12 deaths due to pulmonary hemorrhage
• Recent heavy rainfall had been noted with an
  increase in mosquito rodent populations

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Questions

• How does one confirm that this is an outbreak?
• What might be the cause(s) be ?
• How extensive is the problem?
• What puts certain individuals at risk?
• Is anything facilitating transmission? (if the
  epidemic was due to an infectious agent(s)
• What prevention/control measures are recommended?

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Objectives

• Identify etiologic agent(s)
• Determine scope of outbreak
• Identify risk factor(s) and develop a case
  definition
• Identify potential vector/reservoir
• Estimate seroprevalence in epidemic area
• Make recommendations

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Objectives

• Identify etiologic agent(s)
• Determine scope of outbreak
• Identify risk factor(s) and develop case
  definition
• Identify potential vector/reservoir
• Estimate seroprevalence in epidemic area
• Make recommendations

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Questions

• What is a good syndrome of signs symptoms?
• Consider possible causes?
• - what is the differential diagnosis
• What should be the initial approach to determine
  cause(s)?

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Differential Diagnosis Considerations

• Dengue, DHF, DSS
• Hantavirus
• New World arenavirus
• LCM virus
• Bunyavirus

• Filovirus
• Togavirus
• Rickettsiae spp.
• Ehrilichia chaffeensis
• Coxiella burnetti

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Identifying the etiologic agent

• 55 case-patients suspected of having dengue
• Serum specimens had been submitted to CDC
• Post-mortem tissue specimen(s) available from
• 4 fatal case-patients for immunohistochemistry
  (IHC) evaluation

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Identifying etiologic agent Results

• Leptospira spp. identified in 3 of 4 specimens
• Serologies in 28/55 (51) had gt 400 titer to
  Leptospira spp.
• 13/14 post-mortem tissue specimens were positive
  for Leptospira spp.)

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Leptospirosis
(Weil disease, Canicola fever, Hemorrhagic
jaundice, Mud fever, Swineherd disease)
AGENT Leptospira interrogans
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Leptospirosis

• History Long identified in certain risk
  groups
• Agent 23 serogroups with gt 200 serovars

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Leptospirosis

• History Long identified in certain risk
  groups
• Agent 23 serogroups with gt 200 serovars
• Reservoir Domestic and wild mammals esp. rats

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Leptospirosis

• History Long identified in certain risk
  groups
• Agent 23 serogroups with gt 200 serovars
• Reservoir Domestic and wild mammals esp. rats
• Host Humans and mammals

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LEPTOSPIROSIS CLINICAL PRESENTATION

• Incubation period 4-49 days
• Sign Symptoms Fever, headache, chills,
  myalgia, rash, conjunctivitis.
• Complications Meningitis, hepatitis, anemia,
  hepatorenal syndrome, cardio- pulmonary
  involvement
• Mortality rate 1-20

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Clinical Presentations of Leptospirosis
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Leptospirosis

• History Long identified in certain risk
  groups
• Agent 23 serogroups with gt 200 serovars
• Reservoir Domestic and wild mammals esp.
  rats
• Host Humans and mammals
• Distribution Worldwide
• Diagnosis ELISA culture serology
• Treatment Penicillins and tetracyclines

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Objectives

• Identify etiologic agent(s)
• Determine scope of outbreak
• Identify risk factor(s) and develop a case
  definition
• Identify potential vector/reservoir
• Estimate seroprevalence in the epidemic area
• Make recommendations

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Questions

• What kind of sampling is appropriate?
• Should clinic records be reviewed?
• What should be the screening criteria?
• What time period should be covered?
• Is mortality data available for deaths in the
  area?
• What regional population data are available?
• What are the demographic characteristics?

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Determine serovar strain case findings

• Active clinic-based surveillance from Achuapa
  El Sauce clinics and the nearby Leon Hospital
• Blood/urine specimens taken from acutely ill
  cases with fever and chills AND 3 of the
  following
• - Headache, musculoskeletal pain, abdominal pain,
  nausea, vomiting, retro-orbital pain, hemorrhagic
  manifestations, dyspnea, respiratory failure,
  thrombocytopenia

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Determine scope of outbreak

• Review of 37,030 clinic records
• 2,259 people presented with a non-malarial
  febrile illness from Oct. 1 Nov. 30
• Cumulative incidence 2,259/37,030 6.1
• Age-specific incidence rates calculated
• Ages 1-14 were most affected (7.8)
• Males and females equally affected

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Non-malarial febrile illnesses
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Age-specific non-malaria febrile illnesses
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Determine scope of outbreak

• Mortality data
• 15/2,259 (0.7) pulmonary hemorrhage deaths from
  the areas of study
• A total of 48 (15 33 from other areas)
  hemorrhagic deaths from nearby towns and
  Managua from Oct. 12 to Nov. 19

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Objectives

• Identify etiologic agent(s)
• Determine scope of outbreak
• Identify risk factor(s) and develop case
  definition
• Identify potential vector/reservoir
• Estimate seroprevalence in the epidemic area
• Make recommendations

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Questions

• What kind of study design is appropriate?
• How do you develop a case definition?
• Should there be a comparison group (controls)?
• How do you collect the relevant data?

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Identify risk factor(s) of illness

• Case-control study was conducted
• - Cases from urban El Sauce Achapua, La Calera
  (rural district with highest incidence), and
  all fatal cases
• - Controls ONE per case patient selected
  randomly from the same town/district matched by
  AGE group

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Epi Case Definition

• In a hospitalized patient, presence of
• 1) fever, headache, and either chills or
  musculoskeletal pain
• AND
• 2) abdominal pain, respiratory distress,
  hemorrhagic manifestations, or hypotension
• AND
• 3) a negative malaria smear

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Symptom or Signs in case patients
(a 11 patients died)
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Lab Case Definitions

• Confirmed
• Isolated Leptospira from blood or urine
• gt 4 fold rise in titer in acute/convalescent
  sera
• Leptospira found in post-mortem tissue by IHC
• Probable
• Titer of gt 400 to one or more serovars
• Negative
• Titer lt400 to all serovars

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Questionnaire

• Questions on travel, daily activities,
  environment exposures, food history, pre-existing
  medical conditions, animal exposures
• The questionnaire was administered to both
  cases/controls

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Risk factors
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Lab Results

• Case patients (n 51)
• Lab specimens from 39 (76) 34 serum specimens
  (17 paired 17 single) and 5 post-mortem tissue
• 14 lab confirmed, 12 probable, 13 negative
• Controls (n 51)
• Lab specimens from 47 (92) 36 (71)
  seronegative and 11 (22) gt 400

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Objectives

• Identify etiologic agent(s)
• Determine scope of outbreak
• Identify risk factor(s) of illness
• Case definition
• Identify potential vector/reservoir
• Estimate seroprevalence (epidemic area)
• Make recommendations

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Questions

• What could be done to identify vector(s)?
• What animals are in the area?
• What is the prevalence of Leptospira spp. among
  local animals?

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Identify potential vector/reservoir

• Mosquitoes
• Entomologic surveys were conducted
• Resting mosquito collections were obtained
• Light and CO2 traps were placed indoors /
  outdoors, and in both rural and urban areas
• NO Aedes aegypti collected

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Lab evidence of leptospirosis
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Objectives

• Identify etiologic agent(s)
• Determine scope of outbreak
• Identify risk factor(s) of illness
• Case definition
• Identify potential vector/reservoir
• Estimate seroprevalence (epidemic area)
• Make recommendations

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Estimate seroprevalence

• 204 serum obtained from household contacts
• 72/204 had titers gt 400 to one or more serovars
  and not more likely than controls to have titers
  gt 400 to Leptospira spp.
• Prevalence of febrile illnesses 14 100 in
  October
• Other survey results pending

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Objectives

• Identify etiologic agent(s)
• Determine scope of outbreak
• Identify risk factor(s) of illness
• Case definition
• Identify potential vector/reservoir
• Estimate seroprevalence (epidemic area)
• Make recommendations

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Questions

• Do findings support identified causes for which
  recommendations are needed?
• How can laboratory components be improved?
• What public education (including healthcare
  workers) measures should be taken?

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Summary of findings

• There was a major outbreak of leptospirosis
  resulting in a pulmonary hemorrhage syndrome
  (associated with deaths)
• Previous heavy rainfall and flooding were
  important contributors
• Potential animal reservoirs (dog urine) can
  become an important source of infection

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Make recommendations

• Increase MD awareness of leptospirosis as part of
  differential diagnosis in areas endemic for
  malaria, dengue and typhoid fever
• Early Rx with penicillin may be curative
• People living in at-risk areas should reduce
  exposure by avoiding contact with potentially
  contaminated water wearing protective
  boots/clothing
• Ensure proper specimen collection, transportation
  and testing at centralized reference laboratory

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Leptospirosis Diagnosis
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Leptospirosis

• History Long identified in certain risk
  groups
• Agent 23 serogroups with gt 200 serovars
• Reservoir Domestic and wild mammals esp. rats
• Host Humans and mammals
• Distribution Worldwide
• Diagnosis ELISA culture serology
• Treatment Penicillins and tetracyclines

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ALMOST THE END
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Water-borne disease Considerations in Virginia

• Flooding
• Well water contamination
• Recreational sports and activities
• Fresh water temperatures gt85
• Wild and domestic animal reservoirs
• Environmental incursions
• Importation of fruits and vegetables