Exam 4: Rickettsiae and Ehrlichia

Question 1

Describe characteristics of Rickettsiae

Answer 1

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

Question 2

How are Rickettsiae species transmitted?

Answer 2

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

Question 3

What are Rickettsiae species responsible for?

Answer 3

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

Question 4

What is rocky mountain spotted fever caused by?

Answer 4

Rickettsia rickettsii

Question 5

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

Answer 5

Dogs

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

Question 6

What is rocky mountain spotted fever primarily transmitted through?

Answer 6

The bites of infected ticks

Question 7

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

Answer 7

American dog tick and Rocky Mountain wood tick

Question 8

How is the RMSF pathogen acquired?

Answer 8

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

Question 9

How can R. rickettsii be transmitted to human hosts?

Answer 9

Through the bite of an infected tick

Question 10

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

Answer 10

Via a receptor-mediated invasion mechanism

Question 11

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

Answer 11

Nutrients
Adenosine triphosphate
Amino acids
Nucelotides

Question 12

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

Answer 12

Small blood vessels (endothelial cells)

Question 13

What is death from RMSF due to?

Answer 13

Damage of endothelial cells

Leakage of plasma decrease in blood volume and shock

Question 14

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

Answer 14

Dogs are highly susceptible, but cats are not

Question 15

What do early signs of RMSF include in dogs?

Answer 15

Fever
Lymphadenopathy
Polyarthritis

Question 16

What may be seen in severe cases of RMSF?

Answer 16

Petechial hemorrhages of the conjunctiva and oral mucosa

Question 17

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

Answer 17

Thrombocytopenia

Leukopenia

Question 18

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

Answer 18

Vascular endothelial damage

Question 19

What should the administration of antibiotic treatment based on?

Answer 19

Clinical suspicion without waiting for results of serologic tests

Question 20

What is the treatment of choice for RMSF?

Answer 20

Doxycycline

Question 21

What is salmon poisoning disease (SPD) caused by?

Answer 21

Neorickettsia helminthoeca

Question 22

When do signs of SPD appear?

Answer 22

Suddenly, usually 5-7 days after eating infected fish

Question 23

What can happen if SPD remains untreated?

Answer 23

Death in 90% of cases

Question 24

What occurs with SPD?

Answer 24

Vomiting in most cases

Diarrhea often contain blood and may be severe

Question 25

What is canine ehrlichiosis primarily caused by?

Answer 25

Ehrlichia canis, which causes monocytic form of illness

Question 26

Describe E. chaffeensis

Answer 26

Causes monocytic form of illness | The primary species causing human ehrlichiosis infection in the USA

Question 27

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

Answer 27

It must feed for 48 hours

Question 28

What does E. ewingii primarily infect?

Answer 28

The granulocytes of deer and dogs

Question 29

What is Anaplasma phagocytophilum the agent of?

Answer 29

Human granulocytic ehrlichiosis

Question 30

What is infection with Anaplasma phagocytophilum referred to as?

Answer 30

Anaplasmosis

Question 31

Where is Anaplasma phagocytophilum predominantly found?

Answer 31

In granulocytes

Question 32

Describe A. platys

Answer 32

Infects platelets | Causes infectious cyclic thrombocytopenia in dogs

Question 33

What is E. canis transmitted by?

Answer 33

The brown dog tick

Question 34

Which Ehrlichia spp causes the most potentially sever clinical presentation?

Answer 34

E. canis

Question 35

What is present in acute cases of ehrlichiosis?

Answer 35

``` Reticuloendothelial hyperplasia Fever Lymphadenopathy Splenomegaly Thrombocytopenia ```

Question 36

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

Answer 36

Thrombocytopenia

Question 37

What does vasculitis induce with E. canis?

Answer 37

A thrombocytopenia and hemorrhagic tendencies

Question 38

What is a common finding in canine granulocytic ehrlichiosis?

Answer 38

Polyarthritis

Question 39

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

Answer 39

A platelet count screening test

Question 40

How should the treatment of suspected ehrlichiosis cases be handled?

Answer 40

They should nerve be delayed or withheld

Question 41

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

Answer 41

Doxycycline

Question 42

What does heartwater/cowdriosis affect?

Answer 42

Cattle Sheep Goats Antelope

Question 43

Where is heartwater/cowdriosis found?

Answer 43

Throughout sub-Saharan Africa and in parts of the Caribbeam

Question 44

What is heartwater/cowdriosis caused by?

Answer 44

Ehrlichia ruminantium

Question 45

What is heartwater/cowdriosis characterized by?

Answer 45

``` Fever Nervous signs Hydropericardium Hydrothorax Ascites Edema of the lungs High mortality ```

Question 46

When can clinical signs of heartwater be seen?

Answer 46

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

Question 47

What is the reason for concern about heartwater/cowdriosus?

Answer 47

Bont Ticks have been identified in the US

Question 48

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

Answer 48

Early treatment with tetracyclines