E2 Order Rickettsiales Flashcards
Pathogen Disease Host Mechanism Immunity Culture Notes
???
What tissue are Rickettsiales (order) of bacteria tropic for?
Vascular endothelium or leukocytes
What is unique about Rickettsiales (order) bacteria transmission?
Arthropod vectors
What is the gram reaction & appearance of Rickettsiales (order) bacteria?
Gram-negative
Pleomorphic (variable shape)
What type of disease do Rickettsiales (order) bacteria cause?
Multisystemic disease
What is unique about the Rickettsiales (order) bacteria location in the animal?
Intracellular pathogen (vascular endothelium or leukocytes)
Why is it difficult to culture or treat Rickettsia (genus) bacteria?
They are obligate intracellular pathogens
What cell types do Rickettsia (genus) bacteria target?
Reticuloendothelial system cells
endothelial cells & monocytes
What animals are incidental hosts of Rickettsia rickettsii? Why?
Humans & dogs
They do not have enough parasitemia to infect ticks (dogs may be able to cause infection in ticks)
What animals are normal hosts for Rickettsia rickettsii?
Small mammals
What is the arthropod vector for Rickettsia rickettsii?
Ticks
What disease does Rickettsia rickettsii cause?
Rocky mountain spotted fever (RMSF)
What is rocky mountain spotted fever (RMSF)?
Acute febrile infectious vasculitis
How long do ticks need to feed to transmit Rickettsia rickettsii?
6-24 hrs
What causes the spots in rocky mountain spotted fever?
Endothelial cell damage causes petechia
When do clinical signs appear from Rickettsia rickettsii in dogs?
2-14 days after infection
Do dogs require treatment for Rickettsia rickettsii infection?
Not usually
Most dogs eliminate the infection naturally
What can happen in dogs infected with Rickettsia rickettsii?
Vascular leakage
Edema
Hypotension
Shock
What is the best way to diagnose Rickettsia rickettsii infection in dogs (2 methods)?
- Visualization of the organism on blood smears
- Paired serum samples (antibodies)
= single HIGH IgG titer
What is the most consistent lab finding in Rickettsia rickettsii infection?
- Thrombocytopenia
2. Fever 5 days after infection
How is Rickettsia rickettsii infection usually diagnosed?
Retrospectively
Dogs gets better with antibiotic treatment
Is there a vaccine against Rickettsia rickettsii infection?
No
Is there any evidence of Rickettsia rickettsii transmission from dogs to humans?
No
What is another family in the order Rickettsiales that is of veterinary importance?
Anaplasmataceae
What are some important genera in the family Anaplasmataceae?
- Anaplasma
- Ehrlichia
- Neorickettsia
What is the gram reaction, tropism and transmission of bacteria in the family Anaplasmataceae?
- Gram-negative
- Obligate parasites of erythrocytes (RBCs) & leukocytes
- Arthropod vectors = ticks & biting flies
What is the most pathogenic species of Anaplasma?
Anaplasma marginale
What does Anaplasma marginale infection look like microscopically?
Dense inclusion bodies in RBCs