EHRLICHIOSIS

1
EHRLICHIOSIS

• Other names
• Human Monocytic Ehrlichiosis (HME)
• Human Granulocytic Ehrlichiosis (HGE)
• Sennetsu fever (Japan)

2
EHRLICHIOSIS

• Rickettsial-like organisms classified in the
  family Ehrlichae (majority are veterinary
  pathogens
• Ehrlichia chaffeensis (HME)
• E. phagocytophyga (HGE)
• E. sennetsutsii - Sennetsu fever
• all are tick-borne zoonoses

3
EHRLICHIOSIS

• E. chaffeensis in host-cell (macrophages) formed
  vacuoles called morulae

4
EHRLICHIOSIS

• Ehrlichia body (E. chaffeensis) in monocyte

5
EHRLICHIOSIS

• Ehrlichia body (E. chaffeensis) in monocyte

6
EHRLICHIOSIS

• An emerging disease, HME was first recognized in
  US in 1986 (patient in Fort Chaffee, AR) HGE in
  a patient in MN in 1993
• gt 500 confirmed cases since 1986 from 30
  different states, 80 HME and 20 HGE
• Major endemic regions
• HME Southeast and South Central
• HGE Upper midwest, eastern seaboard
• Sennetsu western Japan

7
EHRLICHIOSIS

• Epidemiology
• occurrence
• normally seen in late spring through the summer
  (April to September)
• prevalence unknown, but cases have been reported
  throughout the US

8
EHRLICHIOSIS

• Epidemiology
• reservoir
• certain species of Ixodid ticks through
  transstadial passage
• possibly maintained in white-tailed deer, rodents
  in certain regions
• HGE wild or domestic canines, horses (?)

9
EHRLICHIOSIS

• Epidemiology
• mode of transmission
• bite of tick
• contamination of broken skin by crushed tissues
  also possible

10
EHRLICHIOSIS

• Epidemiology
• vector
• E. chaffeensis
• Amblyomma americanum (Lone Star tick) - southeast
  to southwest US
• Dermacentor variabilis (American dog tick) -
  eastern and southern US
• E. phagocytophila
• Ixodes scapularis (black-legged tick) - eastern
  and southern US

11
EHRLICHIOSIS

• Clinical features - human disease
• similar for HME and HGE
• flu-like symptoms
• fever, chills, malaise, myalgia, headache,
  nausea, vomiting
• unlike Lyme and RMSF--skin lesions are rare

12
EHRLICHIOSIS

• Clinical features - human disease
• ddx
• RMSF
• Lyme disease
• multi-system febrile illness
• case fatality rate low treated, although a small
  proportion (5 for both diseases) of patients
  development kidney failure, respiratory
  impairment, meningitis
• fatalities more likely to occur in older patients
  or in patients with improper treatment

13
EHRLICHIOSIS

• Canine ehrlichiosis
• Agent E. canis
• ubiquitous in dogs throughout US and world
• recognized since 1930s
• increased recognition in military dogs after
  Vietnam war - called tropical canine
  pancytopenia
• profound effect on platelets, RBCs and WBCs
• petechial and ecchymotic hemorrhages
• responds to tetracylines - long term therapy
  critical

14
EHRLICHIOSIS

• Potomac horse fever
• Agent E. risticii
• Clinical signs include fever, lethargy, diarrhea,
  mild to moderate colic
• Many can develop laminitis (founder)
• Aquatic snails appear to be involved in life
  cycle - fluke harbored by the snails may actually
  be the carrier of the organism

15
EHRLICHIOSIS

• Equine granulocytic ehrlichiosis
• Agent E. equi
• Clinical signs similar to Canine ehrlichiosis
• fever, lethargy, icterus, anorexia, ataxia
• anemia, thrombocytopenia, leukopenia as seen in
  Canine ehrlichiosis

16
EHRLICHIOSIS

• Diagnosis
• based on clinical signs supported by serology
• IFA titer gt140 or 164
• note laboratory positive titer just means that
  it is statistically different from the negative
  sample (mean 2 SD) this does not imply
  clinically positive
• usually titers are 1160 or higher, with 4-fold
  increase, therefore paired sera at 4-6 weeks
  apart improves diagnostic efficiency

17
EHRLICHIOSIS

• Exposure
• recreational
• occupational

18
EHRLICHIOSIS

• Prevention
• avoid tick-infested habitats
• personal protection
• periodic total body search for presence of ticks
• early removal of tick
• immunization (??)

19
EHRLICHIOSIS

• Control
• tick control
• active surveillance of ticks and wildlife
• to monitor changes in the distribution
• to provide early detection
• to determine risk indices
• to provide prevalence data to evaluate
  effectiveness of prevention programs