Rocky Mountain Spotted Fever (Rickettsiaceae) Flashcards
1
Q
What agent causes RMSF?
A
Gram negative, obligate intracellular bacteria
- Rickettsia rickettsii
2
Q
How is RMSF transmitted?
A
Ticks
- Dermacentor spp./ American Dog Tick
- Rhipicephalus sanguineous/ Brown Dog Tick
- Amblyomma spp./ Lone Star Tick
3
Q
Where (geographically) is RMSF most commonly seen?
A
Everywhere
- North, Central, South America
- Southeast and south central states
- Increased incidence of RMSF in people
4
Q
When is RMSF most commonly seen?
A
April through October
5
Q
What type of cells are affected by RMSF?
A
-
Endothelial cells
- Spread through lymphatics or directly into the bloodstream to small capillaries (> cells pop > DIC)
- Monocytes and smooth muscles
6
Q
What are the clinical signs in a dog with RMSF?
A
Vasculitis (HARD TO TREAT)
- Disordered primary hemostasis
- Edema (ears)
- Hypovolemia and microthrombosis
- Clinical signs in the first 15 days (FAST compared to lyme)
7
Q
What are the physical exam findings in a dog with RMSF?
A
- Fever
- Lymphadenomegaly and splenomegaly
- Ocular and respiratory signs
- Petechiae, ecchymosis, peripheral edema
- Myalgia and arthralgia (painful)
- Neurologic signs
8
Q
What are the laboratory findings in a dog with RMSF?
A
- CBC
- Thrombocytopenia (vasculitis + immuno-mediated destruction)
- Chemistry
- Hypoalbuminemia
- Hyponatremia
- Mild hyperbilirubinemia
- UA
- Proteinuria
- Hematuria
9
Q
How do you diagnose a dog with suspected RMSF?
A
-
PCR
- Low # of ciruclating organism
- Low sensitivity, but specificity 100%
-
Histopathology of cutanous lesions
- Vasculitis causes dermal necrosis of pinna)
- Serology
- IgG/ IgM (4-fold change of titer very sensitive)
- Problem: dog will be dead by that time
10
Q
How do you treat a dog with RMSF?
A
Antibiotics (before diagnostic test confirm infection)
- Doxycycline
- Response 24-48 h or co-infection
Supportive care
- Fluids (careful)
- GI support
- Glucocorticoids? (use when desperate and part of disease is autoimmune; just for 5 days)
