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Infectious Agents > Exam 4: Rickettsiae and Ehrlichia > Flashcards

Exam 4: Rickettsiae and Ehrlichia Flashcards

1
Q

Describe characteristics of Rickettsiae

A

Cytoplasmic membrane extremely permeable
Obligate intracellular parasites
Cannot live in artificial nutrient environments
Reside in cytoplasm

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2
Q

How are Rickettsiae species transmitted?

A

By numerous types of arthropod, including chigger, ticks, fleas, and lice

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3
Q

What are Rickettsiae species responsible for?

A 
Rocky Mountain Spotted Fever
Ehrlichiosis and related infections
Murine typhus
Salmon poisoning disease
Elokomin Fluke Fever
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4
Q

What is rocky mountain spotted fever caused by?

A

Rickettsia rickettsii

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5
Q

What serves as an excellent sentinel of risk for R. rickettsii infection in people? Why?

A

Dogs

Because of their susceptibility to R. rickettsii and relatively higher rates of tick exposure

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6
Q

What is rocky mountain spotted fever primarily transmitted through?

A

The bites of infected ticks

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7
Q

In the US what are the primary vectors for R. rickettsii?

A

American dog tick and Rocky Mountain wood tick

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8
Q

How is the RMSF pathogen acquired?

A

By larval and nymph stages of ticks while feeding on infected vertebrae hosts and is also passed from female ticks to progeny through transovarial transmission

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9
Q

How can R. rickettsii be transmitted to human hosts?

A

Through the bite of an infected tick

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10
Q

How do R. rickettsii induce their internalization into host endothelial cells?

A

Via a receptor-mediated invasion mechanism

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11
Q

What does the cytosol of the host endothelial cell contain that are used by R. rickettsii for growth?

A

Nutrients
Adenosine triphosphate
Amino acids
Nucelotides

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12
Q

What are the sites of the characteristic pathologic lesions of RMSF?

A

Small blood vessels (endothelial cells)

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13
Q

What is death from RMSF due to?

A

Damage of endothelial cells

Leakage of plasma decrease in blood volume and shock

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14
Q

What is the difference in the susceptibility of R. rickettsii in dogs and cats?

A

Dogs are highly susceptible, but cats are not

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15
Q

What do early signs of RMSF include in dogs?

A

Fever
Lymphadenopathy
Polyarthritis

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16
Q

What may be seen in severe cases of RMSF?

A

Petechial hemorrhages of the conjunctiva and oral mucosa

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17
Q

What is common with RMSF? What develops during the early stage of infection?

A

Thrombocytopenia

Leukopenia

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18
Q

What happens due to the direct cytopathic effects of the rickettsiae?

A

Vascular endothelial damage

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19
Q

What should the administration of antibiotic treatment based on?

A

Clinical suspicion without waiting for results of serologic tests

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20
Q

What is the treatment of choice for RMSF?

A

Doxycycline

21
Q

What is salmon poisoning disease (SPD) caused by?

A

Neorickettsia helminthoeca

22
Q

When do signs of SPD appear?

A

Suddenly, usually 5-7 days after eating infected fish

23
Q

What can happen if SPD remains untreated?

A

Death in 90% of cases

24
Q

What occurs with SPD?

A

Vomiting in most cases

Diarrhea often contain blood and may be severe

25
Q

What is canine ehrlichiosis primarily caused by?

A

Ehrlichia canis, which causes monocytic form of illness

26
Q

Describe E. chaffeensis

A

Causes monocytic form of illness

The primary species causing human ehrlichiosis infection in the USA

27
Q

What must a tick do in monocytic ehrlichiosis before transmission can occur?

A

It must feed for 48 hours

28
Q

What does E. ewingii primarily infect?

A

The granulocytes of deer and dogs

29
Q

What is Anaplasma phagocytophilum the agent of?

A

Human granulocytic ehrlichiosis

30
Q

What is infection with Anaplasma phagocytophilum referred to as?

A

Anaplasmosis

31
Q

Where is Anaplasma phagocytophilum predominantly found?

A

In granulocytes

32
Q

Describe A. platys

A

Infects platelets

Causes infectious cyclic thrombocytopenia in dogs

33
Q

What is E. canis transmitted by?

A

The brown dog tick

34
Q

Which Ehrlichia spp causes the most potentially sever clinical presentation?

A

E. canis

35
Q

What is present in acute cases of ehrlichiosis?

A 
Reticuloendothelial hyperplasia
Fever
Lymphadenopathy
Splenomegaly
Thrombocytopenia
36
Q

What is common during the acute phase of E. canis infection in dogs?

A

Thrombocytopenia

37
Q

What does vasculitis induce with E. canis?

A

A thrombocytopenia and hemorrhagic tendencies

38
Q

What is a common finding in canine granulocytic ehrlichiosis?

A

Polyarthritis

39
Q

What is important since thrombocytopenia is consistent finding with ehrlichiosis infections?

A

A platelet count screening test

40
Q

How should the treatment of suspected ehrlichiosis cases be handled?

A

They should nerve be delayed or withheld

41
Q

What is the drug of choice for infection with Ehrlichia and Anaplasma spp?

A

Doxycycline

42
Q

What does heartwater/cowdriosis affect?

A

Cattle
Sheep
Goats
Antelope

43
Q

Where is heartwater/cowdriosis found?

A

Throughout sub-Saharan Africa and in parts of the Caribbeam

44
Q

What is heartwater/cowdriosis caused by?

A

Ehrlichia ruminantium

45
Q

What is heartwater/cowdriosis characterized by?

A 
Fever
Nervous signs
Hydropericardium
Hydrothorax
Ascites
Edema of the lungs
High mortality
46
Q

When can clinical signs of heartwater be seen?

A

Within 14 to 28 days after an infected tick feed on a ruminant host

47
Q

What is the reason for concern about heartwater/cowdriosus?

A

Bont Ticks have been identified in the US

48
Q

How can the death rate from heartwater/cowdriosis be reduced?

A

Early treatment with tetracyclines

Infectious Agents (38 decks)

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