Tick borne diseases

Question 1

What’s the causative agent of ehrlichiosis?

Answer 1

Ehrlichia canis
- gram (-)
- intracellular bacteria

Question 2

How is Ehrlichiosis transmitted to dogs and cats?

Answer 2

arthropod or trematode vectors

Question 3

What does Ehrlichia canis cause?

Answer 3

canine monocytic ehrlichiosis (CME)
- tick borne disease (Rhipicephalus sanguineus aka brown dog tick)
- infects circulating monocytes – forms morulae

Question 4

What’s the pathogenesis of Ehrlichiosis?

Answer 4

Transmission: hours within attachments
Acute signs: 8-20 days post

Question 5

What are the clinical signs of acute Ehrlichiosis?

Answer 5

• lethargy, inappetence, fever, weight loss
• organism replicates in the reticuloendothelial tissues –> lymphadenopathy, splenomegaly
• neurological signs
• thrombocytopenia
• transient proteinuria

Question 6

What are some clinical signs of chronic Ehrliciosis?

Answer 6

can range from mild to life threatening
- bleeding tendencies
- ocular changes: anterior uveitis, retinal hemorrhage, retinal detachment, PU/PD, edema
- pancytopenia
- hypoalbuminemia, hyperalbuminemia, increase ALT, increased ALP
- immune complex glomerulonephritis, azotemia

Question 7

How is Ehrlichiosis diagnosed?

Answer 7

• morulae within monocytes
• confirmed with serology (IFA, ELISA)
• takes 1-4 weeks for antibody detection post initial diagnosis
• paired testing may be needed
• positive serology doesn’t equate to active infection
• PCR alone is not enough for confirmation

Question 8

How is Ehrlichiosis treated?

Answer 8

doxycycline
- intrinsic resistance to fluoroquinolone

Question 9

What’s the causative agent of granulocytic ehrlichiosis?

Answer 9

Ehrlichia ewingii

Question 10

How is E. ewingii transmitted?

Answer 10

by amyblyomma americanum ticks (lone star tick)
- white tail deer = reservoir

Question 11

What are some clinical signs of E. ewingii infection?

Answer 11

• lethargy, anorexia, vomiting, diarrhea, neurological signs
• fever, neutrophilic polyarthritis

Question 12

What’s the causative agent of anaplasmosis?

Answer 12

Anaplasma phagocytophilum
- causes granulocytic ehrlichiosis, just like E. ewingii

Question 13

What’s the pathogenesis of anaplasmosis?

Answer 13

• transmitted via Ixodes spp
• morulae in neutrophils
• needs 24-48h attachment
• clinical signs in 1-2 weeks

Question 14

What are the clinical signs of anaplasmosis?

Answer 14

• usually subclinical in dogs
• vague signs
• lethargy, fever, inappetance, scleral injection, unwillingness to move, lameness, stiffness
• thrombocytopenia

Question 15

How is anaplasmosis diagnosed? how is it treated?

Answer 15

• serology: may be negative in acute illness, and seropositivity may indicate previous exposure (up to 8m prior)
• treatment = doxycycline

Question 16

What does A. platys cause?

Answer 16

thrombocytic anaplasmosis

Question 17

What causes salmon poisoning disease?

Answer 17

Neorickettsia helminthoeca

Question 18

What’s the vector for salmon poisoning disease?

Answer 18

a fluke called Ananophyetus salmincola

Question 19

How is salmon poisoning disease transmitted?

Answer 19

• the fluke infects snail –> cercariae leave the snail –> penetrates fish –> develops in kidneys, muscles, and other tissues –> ingested by dogs

Question 20

What c/s signs does salmon poisoning cause in cats?

Answer 20

cats are not susceptible to salmon poisoning disease!
- but the fluke does develop in the in the intestinal tract

Question 21

What are the c/s of salmon poisoning disease in dogs?

Answer 21

• the fluke matures in the intestines, then attaches to the GI tract –> N. helminthoeca infects and replicates within cells of the mononuclear-phagocyte system –> LNs, spleen, liver, lungs, and brain
• acute illness = anorexia, high fever
• later on: lethargy, weight loss, lymphadenopathy, v/d
• thrombocytopenia
• electrolyte changes, increased liver enzymes

Question 22

How is salmon poisoning disease diagnosed? How is it treated?

Answer 22

• can see organism in LN!
• ova in feces
• PCR
• doxycycline

Question 23

What’s the causative agent of Potomac horse fever?

Answer 23

Neorickettsia risticii

Question 24

What’s the causative agent of rocky mountain spotted fever?

Answer 24

Rickettsia rickettsii

Question 25

What’s the vector for rocky mountain spotted fever?

Answer 25

Dermacentor ticks (the American dog tick)

Question 26

What’s the pathogenesis of rocky mountain spotted fever?

Answer 26

• need 4-24 hours for reactivation after tick attachment
• incubation period (median 7d)
• fever, lethargy, anorexia, and lymphadenopathy
• people: classic triad of fever, rash, and headache
• ocular signs
• neurological signs
• median time to death after onset of clinical signs = 8d

Question 27

How is rocky mountain spotted fever diagnosed?

Answer 27

• antibody detection
• PCR
• titer needs convalescent phase to confirm, but it would take too long
• direct immunofluorescence or immmunoperoxidase on infected tissuesHo

Question 28

How is rocky mountain spotted fever treated?

Answer 28

doxycycline

Question 29

How do cats do with rickettsia disease?

Answer 29

rarely infected
- similar clinical signs as dogs
- treat with doxycycline