Infectious Flashcards
1
Q
What larval stage is the infective stage of heartworm disease?
A
L3
2
Q
How long does it take to see microfilaria on testing in heartworm infection?
A
6-8 months because this is how long it takes for adults to mature and reproduce
3
Q
Dogs/cats are more efficient at clearing heartworm larvae in immature stages
A
Cats
4
Q
What is the only FDA approved adulticide for treatment of heartworm disease?
A
Melarsomine
5
Q
Piroplasms/piriform inclusions are seen in RBCs with what disease
A
Babesia
Remember piro means pear
6
Q
Babesia, Cytauxzoon, and Bartonella are ERYTHROCYTIC/LEKOCYTIC/THROMBOCYTIC/EXTRACELLULAR/ENDOTHELIAL
A
Erythrocytic
7
Q
Ehrlichia, Anaplasma, and Hepatazoon are ERYTHROCYTIC/LEKOCYTIC/THROMBOCYTIC/EXTRACELLULAR/ENDOTHELIAL
A
Leukocytic
8
Q
A. platys is ERYTHROCYTIC/LEKOCYTIC/THROMBOCYTIC/EXTRACELLULAR/ENDOTHELIAL
A
Thrombocytic
9
Q
Borrelia is ERYTHROCYTIC/LEKOCYTIC/THROMBOCYTIC/EXTRACELLULAR/ENDOTHELIAL
A
Extracellular
10
Q
Rickettsia is ERYTHROCYTIC/LEKOCYTIC/THROMBOCYTIC/EXTRACELLULAR/ENDOTHELIAL
A
Endothelial
11
Q
Rhipicephalus sanguineus/”Brown dog tick” carries what dieases?
A
Babesia sp.
Ehrlichia canis
Bartonella vinsonii ss berkhoffi
12
Q
Amblyoma ammericanum/”Lone star tick” carries what diseases?
A
Ehrlichia chaffensis
Ehrlichia ewingii
Cytauxzoonosis
13
Q
Ixodes scapularis/”eastern black leg tick” carries what diseases?
A
Babesia sp.
Anaplasma phagocytophilum
Borrelia
14
Q
Dermacentor variabilis/”American dog tick” carries what diseases?
A
Babesia sp.
Rock mountain spotted fever
Cytauxzoonosis
15
Q
Is Babesia zoonotic?
A
NO - species that infect cats and dogs have not been found to infect people
16
Q
What subspecies of Babesia canis are most prevalent in North America?
A
Babesia canis vogeli
Babesia gibsoni
17
Q
What breed of dogs are inherently susceptible to Babesia canis vogeli?
A
Greyhounds
18
Q
What breed of dogs are associated with increased rates of Babesia gibsoni infection?
A
Pitbulls
This is thought to be b/c transmission is more from fighting (and less from ticks)
19
Q
T/F: Babesia felis is common in cats in the US
A
False - rare, most common in cats in South Africa
20
Q
What is the infective form of Babesia canis that is transmitted in tick saliva?
A
Sporozoites - this is the form that penetrates RBCs
21
Q
What is the circulating form of Babesia canis in dogs?
A
Merozoites
Sporozoites will undergo merogony (binary fission) in RBCs then lyse the RBC and be released as merozoites
22
Q
Where does the sexual phase of Babesia canis happen in the tick?
A
Midgut
23
Q
What are clinical signs of Babesia?
A
Lethargy
Anorexia
Weakness
Pyrexia
Weight loss
Less common signs are seizures, paresis, ataxia, masticatory myositis, ascites, edema, hemorrhage, respiratory distress
24
Q
You are examining a greyhound presenting for anorexia, lethargy, and weight loss. You note pyrexia and splenomegaly. What infectious ddx should be on your list?
A
Babesia canis
25
What PE findings might you see with Babesia canis?
SPLENOMEGALY
Pyrexia
+/- pigmenturia (bilirubinuria, hemoglobuinuria)
26
What hematologic changes might you see on CBC in a dog with Babesia?
Thrombocytopenia - most common
Anemia
27
What are the mechanisms of anemia in Babesiosis?
Immune mediated destruction
Osmotically fragile erythrocytes --> hemolysis
Direct injury to RBCs by Babesia
Cyclic nucleotides, oxidative injury - increased urinary methemoglobinuria; inhibition of erythrocytes 5'-nucleosidase leading to cyclic nucleotides; increased production of superoxide; lipid peroxidation
Activation of Kallikrein system --> excess fibrinogen-like proteins develop --> sticky RBCs leading to vascular stasis
28
What are the two mechanisms through which Babesia causes thrombocytopenia?
Immune-mediated destruction
Consumption (coagulation, DIC)
29
What is the cause of most clinical signs of Babesia?
Tissue hypoxia
30
Complicated Babesiosis is mostly associated with what subspecies?
B. canis rossi
31
What is one infectious (tick borne) ddx for acute pancreatitis?
Complicated babesiosis
32
T/F: Serology for Babesia is highly sensitive
False - low sensitivity; has cross reactivity; 36% of PCR positive dogs had negative serology in one study
33
What is the most sensitive and specific diagnostic for diagnosis of Babesia?
PCR - serial sampling 2-4 weeks apart will increase sensitivity, especial in chronically infected dogs
34
How is Babesia canis treated?
Imidocarb diproprionate (MOA unclear) - 2 IM injections 2 weeks apart
35
What are side effects of Imidocarb?
Anticholinergic effects - SLUDDE (salivation, lacrimation, urination, defecation, diarrhea, emesis; also shivering)
36
What can you pre-treat with prior to Imidocarb to prevent anticholinergic effects?
Atropine - can give SC to decrease side effects
37
T/F: Imidocarb clears B. gibsoni
False - doesn't clear B. gibsoni or conrade but decreases morbidity and mortality
38
How is Babesia gibsoni treated?
Atovaquone + Azithromycin
39
What is the MOA of atovaquone?
Inhibits mitochondrial electron transport chain
40
What is the MOA of azithromycin
Binds 50S subunit of ribosomes to block translation of mRNA
41
Why shouldn't you use atovaquone as a single agent?
Can develop resistance
42
What are the major side effects of atovaquone and how can they be minimized?
GI signs
Liquid formulation causes less GI upset
43
If you're unsure what species of Babesia you have, what should you treat with?
Atovaquone + azithromycin
44
Signet ring-shaped piroplasms are seen with what parasite?
Cytauxzoon
45
What is the main species of Cytauxzoon we worry about?
C. felis
46
Where is Cytauxzoon most commonly found
Southeastern US
47
What is the reservoir host for cytauxzoon
Bobcat
48
What are the two main vectors for Cytauxzoon
Amblyomma americanum (Lone star tick)
Dermacenter variabilis
49
Where in the tick does the sexual phase of reproduction happen with Cytauxzoon
Midgut
50
What is the infective form of Cytauxzoon
Sporozoites
51
What cells does Cytauxzoon infect?
Mononuclear cells
52
Once inside mononuclear cells, Cytauxzoon undergoes binary fission to form __ which eventually leads to rupture of the cell.
Schizonts
These distend and eventually occlude vessels
53
What is released from ruptured mononuclear cells in Cytauxzoon that will then invade RBCs?
Merozoites
54
How many days prior to clinical illness do you usually see piroplasms in RBCs with Cytauxzoon?
1-3 days
55
What are the two mechanisms for pathogenesis of Cytauxoon?
1. Asexual schizogenous reproduction within mononuclear phagocytic cells; schizonts distend the mononuclear cells which occludes vessels (most severe in lymphoid tissues, lung, liver, and spleen)
2. Parasitizes erythrocytes --> hemolysis and anemia
56
What clinical signs can you see with Cytauxzoon?
Lethargy
Anorexia
Pyrexia
Within hours to day, progresses to weakness, icterus, resp distress, obtunded mentation, seizures
57
What PE findings might you see with Cytauxzoon?
Pyrexia
Icterus +/- pale MM
Mild to moderate lymphadenomegaly, splenomegaly, hepatomegaly
Hyperesthetic during muscle palpation
+/- pigmenturia (bilirubinuria, hemoglobinuria)
58
What bloodwork changes might you see in cats with Cytauxzoon?
Pancytopenia or bicytopenia, intraerythrocyte signet rings
Hyperbilirubinemia +/- elevated liver enzymes
59
What is the most sensitive and specific test for diagnosis of Cytauxzoon?
PCR
60
How is Cytauxzoon treated?
Atovaquone + azithromycin
Same as Babesia gibsoni
61
Atovoquone must be given with __ to maximize absorption
Fatty meal
62
What percentage of cats survive Cytauxzoon infection?
60%
63
Is Cytauxzoon zoonotic?
NO
64
Infection with Hepatozoon requires what?
INGESTION of tick - not a tick bite
65
What species tick carries Hepatozoon americanum vs. Hepatozoon canis
Hepatozoon americanum - Amblyomma maculatum
Hepatozoon canis - Rhipicephalus sanguineus
66
What develop in tissues with Hepatozoonosis?
Meronts
67
What is the infective stage of Hepatozoon?
Sporozoites
68
What causes release of sporozoites in the GI tract of dogs after they ingest the tick?
Bile
69
Sporozoites travel from the GIT to where in dogs infected with H. americanum?
Muscle
Form meronts in the muscle that will rupture and cause severe pyogranulomatous inflammation
70
Positive serology for H. canis indicates __
Exposure - not presence of organism
71
What is the best diagnostic test for H. americanum infection?
MUSCLE BIOPSY
72
What is treatment for H. americanum?
TMS + clindamycin + pyrimethamine
OR
Ponazuril
**MUST FOLLOW BOTH protocols with decoquinate for 2 years (!!!)
If you don't follow with decoquinate they will relapse after completing treatment due to asexual recycling of the organism
73
What is treatment for H. canis?
Imidocarb +/- doxycycline
Give until you no longer see gamonts in blood smear
74
Is Hepatozoon zoonotic?
NO
75
What are the two main species of Leishmania of concern in veterinary patients and what form of disease does each cause?
Leishmania infantum - visceral
Leishmania braziliensis - cutaneous
76
What is the vector for Leismania?
Female sandfly
Phlebotomus - old world
Lutzomyia - new world
77
Describe the life cycle of Leishmania
Amastigotes released in midgut of sandfly --> transform into promastigotes --> migrate to pharyngeal valve and are transferred during feeding --> invade macrophages, graulocytes, or get phagocytosed in host --> transform into amastigotes which can rupture out of cells and then infect new cells
78
What is the infectious form of Leishmania?
Metacyclic promastigotes
79
Glomerulonephritis and nephrotic syndrome can happen in end stage visceral disease why
Development of autoantibodies and circulating immune complexes
80
Immune complex formation is what type of hypersensitivity?
Type 3
81
What CBC changes might you see with Leishmania?
Mild to moderate normocytic, normochromic, non-regenerative anemia
Mild thrombocytopenia in up to 50% of cases
WBCs variable (pancytopenia to leukocytosis)
82
What chemistry findings might you see with Leishmania?
Hyperglobulinemia with hypoalbuminemia (>75% of dogs) - typically polyclonal
Mild to moderate azotemia (16-38%)
83
How is Leishmania diagnosed?
Typically cytologically, but can do serology or PCR
84
How is Leishmania treated?
Meglumine antimoniate (or miltefosine) + Allopurinol
85
What is the MOA of meglumine
Inhibit protozoal enzymes and damage protozoal DNA
86
What is the MOA of allopurinol?
Interferes with protein synthesis by Leishmania
87
What is the MOA of miltefosine?
Activates proteases in Leishmania spp. and causes apoptotic death of the parasite
88
Trypanosomiasis is also known as
Chagas disease
89
What is the major condition caused by Trypanosoma cruzi
Myocarditis
90
What vector transmits Trypanosoma cruzi
Reduviid aka Kissing BUg
Triatoma spp.
91
What is the infective form in the life cycle of Trypanosoma cruzi?
Trypomastigote
92
What is the vector for Bartonella in cats?
Fleas
93
What species of Bartonella is most common in cats
Bartonella henselae
94
Are cats usually clinical for Bartonella?
No - they're usually subclinical as they are the reservoir host
95
What species of Bartonella is most common in dogs?
B. vinsonii subsp. berkhoffii
96
What is the most common clinical manifestation of Bartonella in dogs?
Endocarditis
Aortic valve >>> mitral valve
97
What is the test of choice for diagnosis of Bartonella?
PCR
Enhanced with BAPGM prior to PCR (medium that enhances organism)
98
T/F: Azithromycin is the treatment of choice for Bartonella
False - no longer recommended due to rapid development of resistance
99
How is Bartonella usually treated
Fluoroquinolone + doxycycline
Rifampin + doxycycline
If endocarditis: treat initially with aminoglycoside
100
Is Bartonella zoonotic?
YES - Cat scratch fever
101
What tick transmits Lyme disease
Ixodies
Ixodies scapularis on the east coast, Ixodies pacificus on the west coast
102
How long does a tick need to be attached to transmit Borrelia?
36-48h
103
Which outer surface protein of Borrelia helps it adhere to the tick midgut?
OspA
104
Which outer surface protein of Borrelia helps with transmission to the tick salivary gland?
OspC
105
Which outer surface protein of Borrelia helps it evade the host immune response?
VisE
106
Which outer surface protein of Borrelia is found in the chronic infection stage?
OspF
107
What are the two most common clinical manifestations of Borrelia in dogs?
Arthropathy
Nephropathy
108
What causes Lyme nephropathy
Deposition of immune mediated complexes
109
UPC with Lyme nephritis is usually
>5
110
Which outer surface protein is typically a marker for Lyme vaccination?
OspA
111
What are the two forms of Anaplasma, what species are associated with each, and what cells do they infect?
Granulocytic - A phagocytophilum - invade granulocytes
Thrombocytic - A platys - invade platelets
112
What tick species transmits A. phagocytophilum
Ixodes scapularis
113
What tick species transmits A. platys
Rhipicephalus sanguineous
114
Anaplasma phagocytophilum binds to what structure on the neutrophil surface?
P-selectin glycoprotein ligand-1 (PSGL-1) --> makes it hard for the neutrophil diapedesis out of the vessel
115
How long is the cycle of cyclical thrombocytopenia with A. platys?
10-14 days
Over time the thrombocytopenia can change to more immune mediated
116
How is Anaplasma diagnosed?
Identification of morula within infected cells
PCR - confirms active infections; healthy animals can be PCR positive
Serology
- Elisa (4dx) - recombinant MSp2/p44 protein; lack of quantification to document seroconversion
- IFA acute and convalescent serology; IgG first detectable ~8d after exposure; cross reactivity between Anaplasma spp.
117
What are the two forms of Ehrlichia infection, what species are associated with each, and what cells do they infect?
Monocytic - E. canis and E. chaffeensis - monocytes
Granulocytic - E. ewingii - granulocytes
118
What tick species carries E. canis and E. chaffeensis?
Rhipicephalus sanguineous (Brown dog tick)
119
What tick species carries E. ewingii?
Ambyloma americanum (Lone star tick)
120
What breed of dog is predisposed to E. canis
German shepherds
121
What is the hallmark change with monocytic ehrlichiosis?
Thrombocytopenia + hyperglobulinemia (which can be polyclonal or monoclonal)
122
What is the gold standard for diagnosis of ehrlichiosis?
IFA
123
What is the causative agent of Rocky Mountain Spotted Fever?
Rickettsia rickettsia
124
What species of tick carries Rickettsia?
Dermacentor
125
How long does a tick have to be attached to transmit RMSF through tick bite?
5-20h
Remember this isn't the only way they can transmit - can be through ingestion of tick, wound contamination with tick feces, or secretion from tick coxial gland
126
What breeds are predisposed to RMSF?
GSD
Springer spaniels - remember though they have phosphofructokinase (PFK) deficiency which causes fragility of RBCs
127
What changes might you see on histopath with RMSF?
Necrotizing vasculitis
Perivascular polymorphonuclear and lymphoretircular cell infiltration
