Canine Rickettsial Infections

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Canine Rickettsial Infections

• Ehrlichiosis
• Rocky Mountain Spotted Fever

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RickettsiaObligate intracellular parasite
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Ehrlichiosis

• Gram pleomorphic bacteria
• First reported in Algeria in 1935
• Vietnam War guard dogs acquired canine tropical
  pancytopenia in the late 1960s.
• Several species cause disease in dogs
• E. canis, E. chaffeensis, E. ewingii /- other E.
  species

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E. Canis

• Tracker Dog Disease
• Transmitted by the brown dog tick (Rhipicephalus
  sanguineus)
• Canids, including domestic dogs, coyotes, foxes
  and jackals are considered the reservoir hosts.
• Occurs throughout the year.
• Replicates and spreads in mononuclear cells.

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E. CanisPathogenesis

• 3 phases
• Acute Phase occurs 8-10 days post infection and
  typically lasts 2-4 weeks.
• Symptoms in the acute phase dogs get a fever,
  loose their appetite and become depressed. The
  often get ocular and nasal discharge. They can
  get low platlets(thrombocytopenia) and low WBC
  counts

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E. CanisPathogenesis

• Sub clinical Phase Can last months to years.
  The fever subsides and the dog appears to
  recover. The dogs immune system may clear the
  organism and be free of disease. If the dog is
  unable to clear itself of E. canis the disease
  will enter into a chronic phase.

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E. CanisPathogenesis

• Chronic Phase Dogs generally loose weight and
  have a poor body condition. Marked bone marrow
  suppression can occur with dogs showing chronic
  anemia, leukopenia and thrombocytopenia. Death
  usually occurs due to severe anemia or infections
  secondary to low WBCs.

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E. CanisSymptoms

• Fever
• Sudden, severe bloody nose
• Discharge from the nose and eyes
• Uveititis and Hyphema
• Blood disorders, pancytopenia
• Weight loss
• Enlarged Lymph nodes
• Hyperglobulinemia

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E. CanisDiagnosis

• 1. Clinical Signs
• 2. Fluorescent Antibody Test
• 3. Elisa Test (Idexx labs)
• 4. CBClow rbcs, wbcs, and platlets
• 5. Increased serum total protein, especially the
  gamma globulins
• 6. DNA-PCR tests
• 7. Demonstration of the ehrilichia morulae in
  WBCs.

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Monocytic Ehrlichiosismorula in a monocyte
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Granulocytic Ehrlichiosismorula in a neutrophil
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E. CanisTreatment

• 1. Antibioticsorganism is sensitive to
  tetracyclines, doxacycline
• 2. Blood Transfusionneeded if severe bleeding
  occurs
• 3. Corticosteroidsfor thrombocytopenia

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E. CanisPrognosis

• Good for the acute phase
• Guarded for chronically infected dogs

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Control and Prevention

• No vaccines are available
• Tick control is essential

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E. Canis Control
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Rocky Mountain Spotted Fever

• Rickettsia rickettsii
• Black Measles
• Tick typhus
• First reported in the Snake river valley of Idaho
  in 1896. Bacteria was isolated by Howard Rickets
  in 1906
• Recognized in dogs in 1970s

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Rocky Mountain Spotted Fever
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Rocky Mountain Spotted FeverPathogenesis

• Incubates for 2-14 days within the infected host.
  It then enters the endothelial cells causing
  vasculitis which leads to edema, hemorrhage and
  shock. The organs most often affected are the
  brain, skin, heart and kidneys.

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Rocky Mountain Spotted FeverClinical Signs

• In dogs most cases are reported between March and
  October.
• Most dogs are less than 3 yrs old and have had a
  recent tick exposure.
• Dogs get a red rash around the tick bite.
• Fever
• Hemorrhages on the mucosal surfaces
• Edema with possible necrosis of extremities
• Ocular Lesions, hyphema, uveitis

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Rocky Mountain Spotted FeverSymptoms Canine

• Joint swelling, muscle pain, difficulty breathing
  and in coordination.
• Disease is often self limiting in dogs with
  recovery in 2 weeks.

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Rocky Mountain Spotted FeverDiagnosis

• 1. Thrombocytopenia
• 2. Serologic testing
• 3. Biopsy of skin lesions for fluorescent
  antibodies.

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Rocky Mountain Spotted FeverTreatment

• Clinical signs may be dramatic or very mild.
• Antibiotics Tetracyclines, doxacycline, baytril
• Topical eye medications for hyphema and uveitis

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An infected tick Must attach for 5-20 hrs
for Transmission to Occur.
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Rocky Mountain Spotted FeverTransmission

• American Dog Tick (Dermacentor variabilis)
• Rocky Mountain Wood Tick (Dermacentor andersoni)
• 2002-2004 outbreak in Eastern Arizona
• Disease was traced to the Brown Dog Tick
• (Rhipicephalus sanguineus)
• The tick serves as both the reservoir and vector
  for the disease. Dogs and humans are incidental
  hosts and are the only species to display
  symptoms of the disease.

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Rocky Mountain Spotted FeverHumans

• Most common fatal tick-borne human disease in the
  United States.
• 4 Mortality rate can go as high as 20 in
  untreated individuals

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Rocky Mountain Spotted Fever
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Rocky Mountain Spotted Fever
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Prevention

• Tick control
• Removing ticks within 4 hours of the bite

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Feline HemobartonellosisFeline infectious anemia

• Small epierythrocytic gram-negative organisms
• Now classed as a feline hemotropic mycoplasm
• Species specific and cannot survive outside of
  the host (cat)
• Considered an opportunistic organism
• Natural transmission? /- bloodsucking parasites
• Can be passed with blood transfusions

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Hemobartonellosis
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Feline Infectious Anemia
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Feline Infectious AnemiaSymptoms

• Depression
• In appetite
• Dehydration
• Anemia (regenerative)
• Weight loss
• Enlargement of the spleen

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Feline Infectious AnemiaDiagnosis

• Detection of the organism on RBCs
• PCR
• Unable to culture these organisms

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Feline Infectious AnemiaTreatment

• Tetracycline (doxacycline)
• Corticosteroids (prednisone)
• Blood transfusions

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Prognosis

• Good if caught early and not Felv