Bacteriology: Infections of the Hemolymphatic and Circulatory System Part I

Describe using the 4 quadrants, what is Canine Ehrlichiosis:

• G-

• Aerobe

What are the species examples of Canine Ehrlichiosis:

• Ehrlichia canis

• Ehrlichia ewingii

• Ehrlichia chaffeensis

What is the pathogenesis of Canine Ehrlichiosis:

Tick bite → bacteria enter bloodstream → infect blood cells → inflammatory responses impacting spleen, vessels, and bone marrow

Which tick species is the brown dog tick (Rhipicephalus sanguineus)

• E. canis

Which tick species is the Lone star tick (Amblyomma americanum);

• E. ewingii

• E. chaffeensis

What are the acute clinical signs for Canine Ehrlichiosis

• Fever and lethargy, generalized pain

• Coagulopathy: Petechia/ecchymosis/melena/epistaxis

• Splenomegaly

• lymphadeonpathy

What are the chronic clinical signs for Canine Ehrlichiosis

• Immune complex-mediated damage: Vasculitis, glomerulonephritis, uveitis, polymyositis/arthropathy (E. ewingii)

What are the lab worm findings for Canine Ehrlichiosis:

•Thrombocytopenia

•Mild, non-regenerative anemia

•Elevated WBCs (Neutrophilia, Lymphocytosis) = possible in chronic

cases

What is the diagnosis of Canine Ehrlichiosis:

• Blood smear = Visualize bacteria in monocytes and/or granulocytes

• Serology with convalescent titers (repeated 2-4 weeks apart)

• PCR (low sensitivity possible!!)

What is the treatment for Canine Ehrlichiosis

• Oral Tetracycline (Doxycycline) for 28 days

• Blood/platelet transfusion

What is the prevention MOA we use for Canine Ehrlichiosis:

• Use tick prevention!

• Fipronil, isoxazoline, pyrethroid, or amitraz preventives

In the 4 quadrants describe Ehrlichia ruminantium:

• G-

• Aerobe

• “Heartwater Disease”

What are the primary victims of Ehrlichia ruminantium and where do you normal find them

Primarily infects ruminants, most common in sub-Saharan Africa and the Caribbean

What is the tick vector for Ehrlichia ruminantium:

Amblyomma spp. (A. variegatum = most important vector)

What is the pathogenesis of Ehrlichia ruminantium:

Tick bite → Bacteria enter bloodstream → infect endothelium

What are the clinical signs for Ehrlichia ruminantium:

Widespread vasculitis, edema, hemorrhage, neurological signs (Peracute development!!)

What is the diagnosis of Ehrlichia ruminantium:

• Clinical signs in endemic area = Increased suspicion

• PCR (blood, tissue, ticks)

What is the treatment for Ehrlichia ruminantium:

• Antimicrobials (at onset of clinical signs); consider treating entire herd; Tetracycline class

• Supportive care: Diazepam (seizures), corticosteroids (vasculitis)

• Vaccination = variable efficacy

• TICK PREVENTION

Describe the 4 quadrant of Hemotropic Mycoplasma spp.:

• cell wall variant

• aerobe

• hemotropic = Infect blood cells

What species are important and can be infected by Hemotropic Mycoplasma spp.:

•Mycoplasma haemofelis = Cats (Healthy cats can get severe disease!!) “Feline Infectious Anemia”

• Others = Typically asymptotic infections or in immune compromised patients (e.g., infections not as clinically significant)

What is the pathogenesis of Hemotropic Mycoplasma spp.:

Pathogenesis: Insect/Arachnid bite or iatrogenic introduction into bloodstream → attach to surface of red blood cells → immune-mediated destruction→ hemolysis (intra - and extravascular)

What is the incubation of Mycoplasma haemofelis:

Incubation period of ~2 to 30 days

What is the acute phase clinicals signs of Mycoplasma haemofelis:

• Fever, lethargy, tachycardia, tachypnea, pale mucus membranes; Occasionally: Icterus and splenomegaly

• Moderate to marked regenerative anemia (Reticulocytosis, nucleated red blood cells, polychromasia)

What are the diagnosis tools to find Mycoplasma haemofelis:

• Cytology (look at blood smear!)

• PCR

• Positive Coomb’s test during acute phase

What is the treatment for Mycoplasma haemofelis:

• Antimicrobials (Tetracycline/ Doxycycline = first choice)

• Doxycycline PO is associated with esophageal strictures in cats; give with water!!!

If its severe hemolytic anemia (w/Mycoplasma haemofelis) what should we do

Consider glucocorticoids and blood transfusion

What is the prevention for Mycoplasma haemofelis:

• Limit iatrogenic spread (Blood donor screening use sterilized supplies for venipuncture/vessel access).

• Use insect protection

In the 4 quadrant what is Neorickettsia helminthoeca:

• G-

• Aerobe

• Salmon poisoning

Where do you normally see Neorickettsia helminthoeca:

• Infects dogs, especially in US Pacific NW

What is the pathogenis of Neorickettsia helminthoeca:

•Pathogenesis: Ingestion of raw/undercooked fish (commonly salmon) infested with trematode Nanophyetus salmincola (carries bacteria Neorickettsia helminthoeca) → infect GI macrophages → granulomatous inflammation

When do the clinical signs appear for Neorickettsia helminthoeca:

• Appear ~7-33 days after ingestion of contaminated fish

What are the actualy clinical signs for Neorickettsia helminthoeca:

• Diarrhea (+/- melena or hematochezia), vomiting, fever, dehydration, generalized lymphadenopathy

• CBC: Thrombocytopenia

What are the diagnosis for Neorickettsia helminthoeca:

• Fecal float + sedimentation (look for Nanophyetus salmincola eggs)

• PCR (blood, LN, spleen samples) → ID N. helminthoeca bacteria

What is the treatment for Neorickettsia helminthoeca:

• Antimicrobial: Doxycycline or Tetracycline PO for 7 days

• Anthelminthic: Praziquantel

• Take home: Treatment = Antibiotic + Antiparasitic

• Supportive care: Antiemetics, fluid resuscitation

What are the preventions for Neorickettsia helminthoeca:

Don’t let dog eat raw/undercooked fish (salmon)

In the 4 quadrants describe Neorickettsia risticii :

• G-

• Aerobe

• “Potomac Horse Fever”

Where do you find Neorickettsia risticii (geographically)

Northeast, Mid-Atlantic, Midwest, pacific northwest, creeks/rivers

What is the pathogenesis of Neorickettsia risticii

Ingest snails or insects carrying trematode → Release Neorickettsia risticii into GI tract → infect GI macrophages → granulomatous inflammation

What are the clinical signs and lab work findings for Neorickettsia risticii

•Depression, anorexia, fever, followed by moderate to severe diarrhea

• Pregnant Mares: Fetus aborted several months post infection, retained placenta

• CBC: Marked leukocytosis several days after onset of clinical signs

What is the diagnosis for Neorickettsia risticii

• PCR of blood + feces

• Cell culture (obligate intracellular pathogen)

What is the treatment for Neorickettsia risticii

• Antimicrobial: 5 days IV Tetracycline

• Supportive care: NSAIDs for inflammation/pain, fluid therapy, watch out for laminitis (can occur secondary to severe colitis!)

What is the prevention for Neorickettsia risticii

• Vaccination

• Reduce insects in stable, evaluate pasture area (e.g. limit exposure

Describe the 4 quadrants of Rickettsia rickettsii:

• G-

• aerobe

• “Rocky Mountain Spotted Fever”

Who are the infectants of Rickettsia rickettsii:

Dogs, people

Where do (geography wise) where do you normally see Rickettsia rickettsii:

Prevalent in Southeast/South central US

What are the vectors for Rickettsia rickettsii:

• Brown dog tick (Rhipicephalus sanguineus)

• American dog tick (Dermacentor variabilis)

• Rocky Mountain wood tick (Dermacentor andersoni)

What is the pathogensis of Rickettsia rickettsii:

Tick bite → bacteria enters circulation → infect endothelial cells → vasculitis

What are the clinical signs or lab work findings of Rickettsia rickettsii:

• Fever, lethargy

• Coagulopathy: Petechiae, ecchymosis, epistaxis, sretinal hemorrhage

• Neurological signs (Ataxia, seizure, etc)

• CBC: Thrombocytopenia

What are the diagnosis for Rickettsia rickettsii:

• Increased suspicion in endemic area + clinical signs = start antibiotics!

• Serologic testing (variable efficacy) → Look for rising titers

• PCR (false negative = common)

What is the Treatment for Rickettsia rickettsii:

• Antimicrobial: Doxycycline

• Supportive care: Fluid therapy, blood products.

• Use tick prevention!!!! (Fipronil, isoxazoline, amitraz, pyrethroids)