28 – Rickettsiales Flashcards
Microbiological characteristics
- Obligate intracellular parasites
- ROD shaped
- Rickettsiacea family: Gram-negative
- Anaplasmataceae family; lack cell wall components of other Gram negatives
- Biocontainment levels depends
- Not possible to culture using ‘standard’ lab methods
Natural host or habitat
- Arthropod associated
- Replication of organism inside the TICK
- Sylvatic cycle: back and forth from vector and reservoir
- Tick to tick transmission
o Transstadial
o Verticel
o Horizontal - *ticks tend to be colonized with one species of Rickettsia
Virulence factors
- Not well described
- *more helpful to think about tissue tropisms
o Rickettsia: vascular endothelium
o Anaplasma: erythrocytes, platelets, leukocytes
o Ehrlichia: leukocytes
o Neorickettsia: leukocytes
What is the Rickettsia rickettsii the agent of?
- Rocky Mountain Spotted Fever
o First described in 1890s: ‘trail fever’
o *affects dogs and people
o IDed all over N. and S. America
o Increasing incidence since 1970s
What are the clinical signs of Rocky Mountain Spotted Fever in dogs?
- *fever
- Edema of extremities
- May develop petechial or ecchymotic haemorrhages (spots)
- Joint pain and swellings
- Myalgia
- Neurological signs
- can get necrosis associated with vasculitis
What is the seasonality of Rocky Mountain Spotted Fever?
- March to October
o Maybe different in SK, due to winter
What is the vector of Rocky Mountain Spotted Fever?
- Hard (Ixodidae) ticks
What is are the possible vectors of Rocky Mountain Spotted Fever in western Canada?
- D. andersoni: SK and AB
- D. variabilis: SK, MB, western ON
- *SK is a sympatric zone
What is the clinical significance of Rocky Mountain Spotted Fever in people?
- *RASH
- Fever, headache, nausea, vomiting, injected conjunctiva
- Long term consequences: vascular inflammation and thrombosis
o Hemorrhage or thrombosis of organs or brain - *not a reportable disease in Canada
o In US, it is increasingly common in people (incidence is up, but case fatality rate is DECREASED!)
o *me
Why decrease in Rocky Mountain Spotted Fever case fatality rate?
- Tetracyclines was invented in 1948
- *doxycycline in Rocky Mountain Spotted Fever
o NO tooth staining
What is Rickettsia prowezakii the agent of?
- Epidemic typhus
What is the clinical disease of epidemic typhus from Rickettsia prowezakii?
- Flu like symptoms
- Rash, neurological signs (headache to coma)
- Untreated takes 2-3 months to recover fully
- Mortality rate varies: up to 40%
What is epidemic typhus spread by?
- Pediculus humanus corporis=human body louse
- *human is reservoir
o Infected lice die within weeks - Associated with flying squirrels in southern USA
When does Epidemic typhus usually occur?
- Miserable conditions
o Filthy and HIGH density - Historical outbreaks: WW1 (Anne Frank)
Where does Bovine Anaplasmosis occur from Anaplasma marginale?
- Between 30 degree S and 40 degree N
o Not in SK
Bovine Anaplasmosis (Anaplasma marginale) in different aged animals
- Young animals (less than a year: subclinical
- *disease is more severe the older the animal is
o More than 2 years old=severe disease
What is seen in severely affected animals with Bovine Anaplasmosis (Anaplasma marginale)?
- Icterus, anemia (extravascular hemolysis)
- Fever
- Decreased milk production
- *can be RAPIDLY FATAL
- Bos indicus cattle may be more resistant?
How do you treat Bovine Anaplasmosis (Anaplasma marginale)?
- Tetracyclines!
- Supportive therapy may be necessary
Vaccination for Bovine Anaplasmosis (Anaplasma marginale) is possible
- Exact strategy depends on where you are
- Some regions: Anaplasma centrale
- *killed A. marginale vaccine in some to protect against severe disease
What does Anaplasma phagocytophilum cause in dogs?
- Canine granulocytotropic anaplasmosis
- *also reported in cats, small mammals, horses, mountain lions and coytoes