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ACVIM Generals > Infectious > Flashcards

Infectious Flashcards

1
Q

What larval stage is the infective stage of heartworm disease?

A

L3

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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

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3
Q

Dogs/cats are more efficient at clearing heartworm larvae in immature stages

A

Cats

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4
Q

What is the only FDA approved adulticide for treatment of heartworm disease?

A

Melarsomine

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5
Q

Piroplasms/piriform inclusions are seen in RBCs with what disease

A

Babesia

Remember piro means pear

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6
Q

Babesia, Cytauxzoon, and Bartonella are ERYTHROCYTIC/LEKOCYTIC/THROMBOCYTIC/EXTRACELLULAR/ENDOTHELIAL

A

Erythrocytic

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7
Q

Ehrlichia, Anaplasma, and Hepatazoon are ERYTHROCYTIC/LEKOCYTIC/THROMBOCYTIC/EXTRACELLULAR/ENDOTHELIAL

A

Leukocytic

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8
Q

A. platys is ERYTHROCYTIC/LEKOCYTIC/THROMBOCYTIC/EXTRACELLULAR/ENDOTHELIAL

A

Thrombocytic

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9
Q

Borrelia is ERYTHROCYTIC/LEKOCYTIC/THROMBOCYTIC/EXTRACELLULAR/ENDOTHELIAL

A

Extracellular

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10
Q

Rickettsia is ERYTHROCYTIC/LEKOCYTIC/THROMBOCYTIC/EXTRACELLULAR/ENDOTHELIAL

A

Endothelial

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11
Q

Rhipicephalus sanguineus/”Brown dog tick” carries what dieases?

A

Babesia sp.
Ehrlichia canis
Bartonella vinsonii ss berkhoffi

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12
Q

Amblyoma ammericanum/”Lone star tick” carries what diseases?

A

Ehrlichia chaffensis
Ehrlichia ewingii
Cytauxzoonosis

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13
Q

Ixodes scapularis/”eastern black leg tick” carries what diseases?

A

Babesia sp.
Anaplasma phagocytophilum
Borrelia

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14
Q

Dermacentor variabilis/”American dog tick” carries what diseases?

A

Babesia sp.
Rock mountain spotted fever
Cytauxzoonosis

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15
Q

Is Babesia zoonotic?

A

NO - species that infect cats and dogs have not been found to infect people

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16
Q

What subspecies of Babesia canis are most prevalent in North America?

A

Babesia canis vogeli
Babesia gibsoni

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17
Q

What breed of dogs are inherently susceptible to Babesia canis vogeli?

A

Greyhounds

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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)

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19
Q

T/F: Babesia felis is common in cats in the US

A

False - rare, most common in cats in South Africa

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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

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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

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22
Q

Where does the sexual phase of Babesia canis happen in the tick?

A

Midgut

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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

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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

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25
Q

What PE findings might you see with Babesia canis?

A

SPLENOMEGALY
Pyrexia
+/- pigmenturia (bilirubinuria, hemoglobuinuria)

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26
Q

What hematologic changes might you see on CBC in a dog with Babesia?

A

Thrombocytopenia - most common
Anemia

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27
Q

What are the mechanisms of anemia in Babesiosis?

A

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

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28
Q

What are the two mechanisms through which Babesia causes thrombocytopenia?

A

Immune-mediated destruction

Consumption (coagulation, DIC)

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29
Q

What is the cause of most clinical signs of Babesia?

A

Tissue hypoxia

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30
Q

Complicated Babesiosis is mostly associated with what subspecies?

A

B. canis rossi

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31
Q

What is one infectious (tick borne) ddx for acute pancreatitis?

A

Complicated babesiosis

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32
Q

T/F: Serology for Babesia is highly sensitive

A

False - low sensitivity; has cross reactivity; 36% of PCR positive dogs had negative serology in one study

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33
Q

What is the most sensitive and specific diagnostic for diagnosis of Babesia?

A

PCR - serial sampling 2-4 weeks apart will increase sensitivity, especial in chronically infected dogs

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34
Q

How is Babesia canis treated?

A

Imidocarb diproprionate (MOA unclear) - 2 IM injections 2 weeks apart

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35
Q

What are side effects of Imidocarb?

A

Anticholinergic effects - SLUDDE (salivation, lacrimation, urination, defecation, diarrhea, emesis; also shivering)

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36
Q

What can you pre-treat with prior to Imidocarb to prevent anticholinergic effects?

A

Atropine - can give SC to decrease side effects

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37
Q

T/F: Imidocarb clears B. gibsoni

A

False - doesn’t clear B. gibsoni or conrade but decreases morbidity and mortality

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38
Q

How is Babesia gibsoni treated?

A

Atovaquone + Azithromycin

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39
Q

What is the MOA of atovaquone?

A

Inhibits mitochondrial electron transport chain

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40
Q

What is the MOA of azithromycin

A

Binds 50S subunit of ribosomes to block translation of mRNA

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41
Q

Why shouldn’t you use atovaquone as a single agent?

A

Can develop resistance

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42
Q

What are the major side effects of atovaquone and how can they be minimized?

A

GI signs

Liquid formulation causes less GI upset

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43
Q

If you’re unsure what species of Babesia you have, what should you treat with?

A

Atovaquone + azithromycin

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44
Q

Signet ring-shaped piroplasms are seen with what parasite?

A

Cytauxzoon

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45
Q

What is the main species of Cytauxzoon we worry about?

A

C. felis

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46
Q

Where is Cytauxzoon most commonly found

A

Southeastern US

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47
Q

What is the reservoir host for cytauxzoon

A

Bobcat

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48
Q

What are the two main vectors for Cytauxzoon

A

Amblyomma americanum (Lone star tick)
Dermacenter variabilis

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49
Q

Where in the tick does the sexual phase of reproduction happen with Cytauxzoon

A

Midgut

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50
Q

What is the infective form of Cytauxzoon

A

Sporozoites

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51
Q

What cells does Cytauxzoon infect?

A

Mononuclear cells

52
Q

Once inside mononuclear cells, Cytauxzoon undergoes binary fission to form __ which eventually leads to rupture of the cell.

A

Schizonts

These distend and eventually occlude vessels

53
Q

What is released from ruptured mononuclear cells in Cytauxzoon that will then invade RBCs?

A

Merozoites

54
Q

How many days prior to clinical illness do you usually see piroplasms in RBCs with Cytauxzoon?

A

1-3 days

55
Q

What are the two mechanisms for pathogenesis of Cytauxoon?

A
  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
Q

What clinical signs can you see with Cytauxzoon?

A

Lethargy
Anorexia
Pyrexia
Within hours to day, progresses to weakness, icterus, resp distress, obtunded mentation, seizures

57
Q

What PE findings might you see with Cytauxzoon?

A

Pyrexia
Icterus +/- pale MM
Mild to moderate lymphadenomegaly, splenomegaly, hepatomegaly
Hyperesthetic during muscle palpation
+/- pigmenturia (bilirubinuria, hemoglobinuria)

58
Q

What bloodwork changes might you see in cats with Cytauxzoon?

A

Pancytopenia or bicytopenia, intraerythrocyte signet rings
Hyperbilirubinemia +/- elevated liver enzymes

59
Q

What is the most sensitive and specific test for diagnosis of Cytauxzoon?

A

PCR

60
Q

How is Cytauxzoon treated?

A

Atovaquone + azithromycin

Same as Babesia gibsoni

61
Q

Atovoquone must be given with __ to maximize absorption

A

Fatty meal

62
Q

What percentage of cats survive Cytauxzoon infection?

A

60%

63
Q

Is Cytauxzoon zoonotic?

A

NO

64
Q

Infection with Hepatozoon requires what?

A

INGESTION of tick - not a tick bite

65
Q

What species tick carries Hepatozoon americanum vs. Hepatozoon canis

A

Hepatozoon americanum - Amblyomma maculatum

Hepatozoon canis - Rhipicephalus sanguineus

66
Q

What develop in tissues with Hepatozoonosis?

A

Meronts

67
Q

What is the infective stage of Hepatozoon?

A

Sporozoites

68
Q

What causes release of sporozoites in the GI tract of dogs after they ingest the tick?

A

Bile

69
Q

Sporozoites travel from the GIT to where in dogs infected with H. americanum?

A

Muscle

Form meronts in the muscle that will rupture and cause severe pyogranulomatous inflammation

70
Q

Positive serology for H. canis indicates __

A

Exposure - not presence of organism

71
Q

What is the best diagnostic test for H. americanum infection?

A

MUSCLE BIOPSY

72
Q

What is treatment for H. americanum?

A

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
Q

What is treatment for H. canis?

A

Imidocarb +/- doxycycline

Give until you no longer see gamonts in blood smear

74
Q

Is Hepatozoon zoonotic?

A

NO

75
Q

What are the two main species of Leishmania of concern in veterinary patients and what form of disease does each cause?

A

Leishmania infantum - visceral

Leishmania braziliensis - cutaneous

76
Q

What is the vector for Leismania?

A

Female sandfly

Phlebotomus - old world
Lutzomyia - new world

77
Q

Describe the life cycle of Leishmania

A

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
Q

What is the infectious form of Leishmania?

A

Metacyclic promastigotes

79
Q

Glomerulonephritis and nephrotic syndrome can happen in end stage visceral disease why

A

Development of autoantibodies and circulating immune complexes

80
Q

Immune complex formation is what type of hypersensitivity?

A

Type 3

81
Q

What CBC changes might you see with Leishmania?

A

Mild to moderate normocytic, normochromic, non-regenerative anemia
Mild thrombocytopenia in up to 50% of cases
WBCs variable (pancytopenia to leukocytosis)

82
Q

What chemistry findings might you see with Leishmania?

A

Hyperglobulinemia with hypoalbuminemia (>75% of dogs) - typically polyclonal
Mild to moderate azotemia (16-38%)

83
Q

How is Leishmania diagnosed?

A

Typically cytologically, but can do serology or PCR

84
Q

How is Leishmania treated?

A

Meglumine antimoniate (or miltefosine) + Allopurinol

85
Q

What is the MOA of meglumine

A

Inhibit protozoal enzymes and damage protozoal DNA

86
Q

What is the MOA of allopurinol?

A

Interferes with protein synthesis by Leishmania

87
Q

What is the MOA of miltefosine?

A

Activates proteases in Leishmania spp. and causes apoptotic death of the parasite

88
Q

Trypanosomiasis is also known as

A

Chagas disease

89
Q

What is the major condition caused by Trypanosoma cruzi

A

Myocarditis

90
Q

What vector transmits Trypanosoma cruzi

A

Reduviid aka Kissing BUg

Triatoma spp.

91
Q

What is the infective form in the life cycle of Trypanosoma cruzi?

A

Trypomastigote

92
Q

What is the vector for Bartonella in cats?

A

Fleas

93
Q

What species of Bartonella is most common in cats

A

Bartonella henselae

94
Q

Are cats usually clinical for Bartonella?

A

No - they’re usually subclinical as they are the reservoir host

95
Q

What species of Bartonella is most common in dogs?

A

B. vinsonii subsp. berkhoffii

96
Q

What is the most common clinical manifestation of Bartonella in dogs?

A

Endocarditis

Aortic valve&raquo_space;> mitral valve

97
Q

What is the test of choice for diagnosis of Bartonella?

A

PCR

Enhanced with BAPGM prior to PCR (medium that enhances organism)

98
Q

T/F: Azithromycin is the treatment of choice for Bartonella

A

False - no longer recommended due to rapid development of resistance

99
Q

How is Bartonella usually treated

A

Fluoroquinolone + doxycycline
Rifampin + doxycycline
If endocarditis: treat initially with aminoglycoside

100
Q

Is Bartonella zoonotic?

A

YES - Cat scratch fever

101
Q

What tick transmits Lyme disease

A

Ixodies

Ixodies scapularis on the east coast, Ixodies pacificus on the west coast

102
Q

How long does a tick need to be attached to transmit Borrelia?

A

36-48h

103
Q

Which outer surface protein of Borrelia helps it adhere to the tick midgut?

A

OspA

104
Q

Which outer surface protein of Borrelia helps with transmission to the tick salivary gland?

A

OspC

105
Q

Which outer surface protein of Borrelia helps it evade the host immune response?

A

VisE

106
Q

Which outer surface protein of Borrelia is found in the chronic infection stage?

A

OspF

107
Q

What are the two most common clinical manifestations of Borrelia in dogs?

A

Arthropathy
Nephropathy

108
Q

What causes Lyme nephropathy

A

Deposition of immune mediated complexes

109
Q

UPC with Lyme nephritis is usually

A

> 5

110
Q

Which outer surface protein is typically a marker for Lyme vaccination?

A

OspA

111
Q

What are the two forms of Anaplasma, what species are associated with each, and what cells do they infect?

A

Granulocytic - A phagocytophilum - invade granulocytes

Thrombocytic - A platys - invade platelets

112
Q

What tick species transmits A. phagocytophilum

A

Ixodes scapularis

113
Q

What tick species transmits A. platys

A

Rhipicephalus sanguineous

114
Q

Anaplasma phagocytophilum binds to what structure on the neutrophil surface?

A

P-selectin glycoprotein ligand-1 (PSGL-1) –> makes it hard for the neutrophil diapedesis out of the vessel

115
Q

How long is the cycle of cyclical thrombocytopenia with A. platys?

A

10-14 days

Over time the thrombocytopenia can change to more immune mediated

116
Q

How is Anaplasma diagnosed?

A

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
Q

What are the two forms of Ehrlichia infection, what species are associated with each, and what cells do they infect?

A

Monocytic - E. canis and E. chaffeensis - monocytes

Granulocytic - E. ewingii - granulocytes

118
Q

What tick species carries E. canis and E. chaffeensis?

A

Rhipicephalus sanguineous (Brown dog tick)

119
Q

What tick species carries E. ewingii?

A

Ambyloma americanum (Lone star tick)

120
Q

What breed of dog is predisposed to E. canis

A

German shepherds

121
Q

What is the hallmark change with monocytic ehrlichiosis?

A

Thrombocytopenia + hyperglobulinemia (which can be polyclonal or monoclonal)

122
Q

What is the gold standard for diagnosis of ehrlichiosis?

A

IFA

123
Q

What is the causative agent of Rocky Mountain Spotted Fever?

A

Rickettsia rickettsia

124
Q

What species of tick carries Rickettsia?

A

Dermacentor

125
Q

How long does a tick have to be attached to transmit RMSF through tick bite?

A

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
Q

What breeds are predisposed to RMSF?

A

GSD
Springer spaniels - remember though they have phosphofructokinase (PFK) deficiency which causes fragility of RBCs

127
Q

What changes might you see on histopath with RMSF?

A

Necrotizing vasculitis
Perivascular polymorphonuclear and lymphoretircular cell infiltration

ACVIM Generals (16 decks)

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