Infectious Flashcards
What kind of bacteria is Ehrlichia?
Intracellular
Gram-negative
How is Ehrlichia transmitted in the vector (tick)?
Trans-stadial transmission
Pathogen remains with vector from one life stage to another (but not from parent to eggs).
Who causes canine monocytic ehrlichiosis
E. canis
Which tick carries E. canis?
Rhipicephalus sanguineous (Brown dog tick)
Who causes Canine granulocytic ehrlichiosis?
E. ewingii
What tick carries E. ewingii (Canine granulocytic ehrlichiosis)?
Amblyomma americanum (lone star tick)
Who causes human monocytic ehrlichiosis
E. chaffeensis
True or false: Ehrlichia, Anaplasma and Neorickettsia are in the same family?
True
Rickettsiae is a separate family
What dog breed is more susceptible to E. canis with a worse prognosis?
German Shepherds
What is the pathogenesis of E. canis? (Canine monocytic ehrlichiosis)
- Organism multiplies within vacules in monocytes - lyse cells
- Immune-mediated mechanism
- Presence of spleen contributes to severity of disease
What are the phases of the disease for canine monocytic ehrlichiosis (E. canis)?
- Acute 8-20 days after infection, may resolve spontaneously.
- Subclinical - Organisms sequestered in spleen
- Chronic phase
- Can see pancytopenia from BM involvement
What are some secondary opportunistic infections with E. canis (canine monocytic ehrlichiosis)?
- Viral papillomatosis
- Protozoal infections
- Bacterial UTIs
What is a protein electrophoresis finding of E. canis?
Sometimes can have a monoclonal gammopathy => misdiagnosis of lymphocytic leukemia or multiple myeloma
What type of hypersensitivity reaction can you see with E. canis?
Type III hypersensitivity (Immune complex deposition) and protein losing nephropathy (glomerulonephritis)
What are some clinical signs of E. canis (canine monocytic ehrlichiosis)?
Fever, lethargy, splenomegaly, lymphadenopathy, anterior uveitis, neurologic CS
What are CBC findings of E. canis?
Thrombocytopenia!
Occasional mild leukopenia
Pancytopenia in chronic phase
Morulae in circulating monocytes
What are common chemistry findings of E. canis?
- Hyperglobulinemia (polyclonal most common, but can be monoclonal) with hypoalbuminemia.
- ALT/ALP elevations
- Azotemia if PLN
What is the gold standard diagnostic for Ehrlichia canis?
IFA (there is cross-reactivity)
What is the consensus treatment for E. canis?
Doxycycline 10mg/kg Q24h x 28d
Does Ehrlichia ewingii (Canine granulocytic ehrlichiosis) have a chronic phase?
NO
Only E. canis
What are symptoms for E. ewingii (Canine granulocytic ehrlichiosis)?
Usually NONE
Fever
Anorexia
Neutrophilic Polyarthritis
True or false: Dogs can be reservoir host for E. ewingii (canine granulocytic ehrlichiosis)
TRUE
What is the pathogen for human monocytic ehrlichiosis and what tick carries it?
- Ehrlichia chaffensis
2. Amblyomma americanum (lone star tick)
Diagnosis for E. ewingii is limited to:
ELISA, western blot, PCR
Can do IFA for E. canis only
What organism causes granulocytic anaplasmosis?
Anaplasma phagocytophilum
What tick carries Anaplasma phagocytophilum (granulocytic anaplasmosis)
Ixodes ricinuspersulcatus complex
What cells are affected by Anaplasma phagocytophilum?
Neutrophils and eosinophils
What organism causes THROMBOCYTOTROPIC ANAPLASMOSIS?
Anaplasma platys - Aka….Canine Cyclical Thrombocytopenia
What cells does Anaplasma platys infect?
Platelets
What is A. phagocytophilum effect on neutrophils?
delays neutrophil apoptosis => allows longer survival periods within the neutrophil.
What is the most common symptoms with A. phagocytophilum?
No clinical signs
What is the most common CBC finding with A. phagocytophilum?
Thrombocytopenia in 90% of canine cases (+/- other cytopenias
What tick carries Anaplasma platys
Rhipicephalus sanguineus
What kind of organism is Babesia spp.
Intracellular protozoan
What cells does babesia spp infect?
RBC
What babesia cell stage is observed within RBC?
Merozoites
What type of immune response does babesia cause?
Induces immune-mediated destruction of erythrocytes
Anti-erythrocyte antibodies may develop as well (self-antigen), contributing to IMHA
What kind of organism is Cytauxzoon?
Apicomplexan protozoal
What does Cytauxzoon use to invade cells?
apical complex
What are the vectors for Cytauxzoon?
Lone Star tick (Amblyomma americanum)
American dog tick (Dermacentor variabilis)
How does Cytauxzoon live in the blood?
Monocytes - Schizont
Erythrocytic - Piroplasm
What is the pathogenesis of Cytauxzoon?
Schizogenous phase - FAT monocytes with schizonts > block blood vessels > microvascular hypoxia, SIRS/sepsis, DIC, organ failure
Piroplasm phase - RBC hemolysis
What is the treatment for Cytauxzoon?
Atovaquone and azithromycin
GIVE WITH FOOD - increased oral bioavailability for atovaquone
Is Cytauxzoon zoonotic?
NO - has not been known to infect people
Hepatozoonosis:
Is it zoonotic?
Does it affect the liver?
NO and rarely lol
How is Hepatozoon transmitted to the dog?
Ingestion of an infected tick (not from tick bite)
What is the life cycle of Hepatozoon americanum?
Sporozoites infect monocytes; Then monocytes go to the muscle; pyogranuloma forms in the muscle (Onion-skin cysts). Burst and release gamonts
What is the life cycle of Hepatozoon canis?
Does not invade the muscle like H americanum.
Dog ingests infected tick, micromerozoites invade neutrophils and and monocytes.
Transplacental transmission
Facts about feline Hepatozoonosis (Hepatozoon felis)
- Usually asymptomatic
* Usually cats with FIV/FeLV
What causes salmon poisoning?
Neorickettsia helminthoeca
What kind of microorganism is Neorickettsia helminthoeca?
Gram-negative coccobacillary organism
Describe the life cycle of Neorickettsia helminthoeca (salmon poisoning)
Vector is Nanophyetus salmincola - a trematode that infects snail, fish, then mammal
What is the pathogenesis of Neorickettsia helminthoeca?
- Dog ingests fish with infected trematode
- Adult fluke innoculates dog with Neorickettsia
- Rickettsial organisms replicate initially in the epithelial cells of the intestinal villi or intestinal
lymphoid tissue then enter the blood stream and spread to the lymph nodes, spleen, tonsils, thymus, liver, lungs, and brain
What is the vector of Neorickettsia helminthoeca?
Nanophyetus salmincola - A trematode/fluke
How do you diagnose Neorickettsia helminthoeca?
- Fecal - May see Nanophyetus salmincola eggs.
- Lymph node cytology - reactivity and histiocytic hyperplasia; Intracytoplasmic rickettsial organisms within histiocytes.
- PCR
What is the treatment for Neorickettsia helminthoeca (Salmon poisoning disease)
Doxycycline for Neorickettsia
Praziquantel for Nanophyetus salmincola fluke
What is the geographic distribution of Neorickettsia helminthoeca (salmon poisoning)
Pacific northwest
Where does R. Rickettsii replicate in the host?
Endothelial cells
What is the mechanism for thrombocytopenia in rocky mountain spotted fever? (R. Rickettsii)
- Immune-mediated destruction
2. Coagulatory consumption
Which organism has been known to cause SIADH? What electrolyte disturbance does SIADH cause?
R. Rickettsii
Hyponatremia
What is the broad pathogenesis of RMSF?
- Vasculitis, increased vascular permeability
- Thrombocytopenia, hemorrhage, DIC
- Edema (brain, lung)
How do you confirm a RMSF diagnosis?
Fourfold increase in IgG seroreactivity
or Positive IgM seroreativity.
There is 5-15% seroreactivity in healthy dogs across the Atlantic
What babesia species can cause red biliary syndrome?
B. canis rossi
What is red biliary syndrome regarding B. canis rossi?
Severe intravascular hemolysis AND
hemoconcentration.
Hemoglobinemia, hemoglobinuria (in some combination) and elevated HCT due to fluid shifts into extracellular spaces
How do you treat Babesia spp. (Other than B. gibsoni)?
Imidocarb diproprionate
How do you treat Babesia gibsoni?
Combination with azithromycin and atovaquone
In addition to Doxy, what drug do you ned to treat a patient with Neorickettsia helminthoeca?
Praziquantel for trematode vector (Nanophyetus salmonicola)
Which would be most specific for the diagnosis of toxoplasma in a cats with clinical signs?
a. Oocysts in feces
b. IgM > 1:64 in CSF
c. IgG > 1:64 in serum
d. Blood culture
b. IgM > 1:64 in CSF
What is the most accurate way to diagnose ocular or CNS toxoplasmosis in cats?
The combination of T. gondii–specific antibody
detection in aqueous humor or CSF and organism DNA amplification by PCR
Which one is acid fast and which one isn’t?
a. Nocardia
b. Actinomyces
a. Nocardia - Acid fast
b. Actinomyces - Non-acid fast
What is the most common cause of pyothorax in cats?
Pasteurella
What is the most common cause of diskospondilytis?
Staph aureus
You have a cat with FIV. Four weeks ago, she gave birth to kittens who tested positive for FIV. What should you do with the kittens?
Isolate the kittens and test them again in 6 months.
Horses and dogs are reservoirs for humans for which pathogen?
Staph aureus
Which tick carries anaplasma phagocytophilum?
Ixodes spp. (co-transmitted with borrelia)
Which virus causes myocarditis in dogs, cerebellar hypoplasia in cats and diarrhea in pigs?
Parvovirus
How is rabies diagnosed?
IFA on the brainstem or cerebellum
How is cryptococcus diagnosed?
Latex agglutination test - Detects capsular antigen
How does leptospirosis cause azotemia?
Interstitial nephritis, renal swelling, and vasculitis => decreased renal perfusion
Lepto also invades renal tubular cells
How is the MAT test for lepto performed?
The patient’s serum is incubated with a suspension of live leptospires and evaluated by dark-field microscopy for agglutination
How is Hepatozoon americanum diagnosed?
Muscle biopsy
What percentage of cats with coronavirus develop FIP?
1/10