Exam 4: Rickettsiae and Ehrlichia Flashcards
Describe characteristics of Rickettsiae
Cytoplasmic membrane extremely permeable
Obligate intracellular parasites
Cannot live in artificial nutrient environments
Reside in cytoplasm
How are Rickettsiae species transmitted?
By numerous types of arthropod, including chigger, ticks, fleas, and lice
What are Rickettsiae species responsible for?
Rocky Mountain Spotted Fever Ehrlichiosis and related infections Murine typhus Salmon poisoning disease Elokomin Fluke Fever
What is rocky mountain spotted fever caused by?
Rickettsia rickettsii
What serves as an excellent sentinel of risk for R. rickettsii infection in people? Why?
Dogs
Because of their susceptibility to R. rickettsii and relatively higher rates of tick exposure
What is rocky mountain spotted fever primarily transmitted through?
The bites of infected ticks
In the US what are the primary vectors for R. rickettsii?
American dog tick and Rocky Mountain wood tick
How is the RMSF pathogen acquired?
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
How can R. rickettsii be transmitted to human hosts?
Through the bite of an infected tick
How do R. rickettsii induce their internalization into host endothelial cells?
Via a receptor-mediated invasion mechanism
What does the cytosol of the host endothelial cell contain that are used by R. rickettsii for growth?
Nutrients
Adenosine triphosphate
Amino acids
Nucelotides
What are the sites of the characteristic pathologic lesions of RMSF?
Small blood vessels (endothelial cells)
What is death from RMSF due to?
Damage of endothelial cells
Leakage of plasma decrease in blood volume and shock
What is the difference in the susceptibility of R. rickettsii in dogs and cats?
Dogs are highly susceptible, but cats are not
What do early signs of RMSF include in dogs?
Fever
Lymphadenopathy
Polyarthritis
What may be seen in severe cases of RMSF?
Petechial hemorrhages of the conjunctiva and oral mucosa
What is common with RMSF? What develops during the early stage of infection?
Thrombocytopenia
Leukopenia
What happens due to the direct cytopathic effects of the rickettsiae?
Vascular endothelial damage
What should the administration of antibiotic treatment based on?
Clinical suspicion without waiting for results of serologic tests
What is the treatment of choice for RMSF?
Doxycycline
What is salmon poisoning disease (SPD) caused by?
Neorickettsia helminthoeca
When do signs of SPD appear?
Suddenly, usually 5-7 days after eating infected fish
What can happen if SPD remains untreated?
Death in 90% of cases
What occurs with SPD?
Vomiting in most cases
Diarrhea often contain blood and may be severe
What is canine ehrlichiosis primarily caused by?
Ehrlichia canis, which causes monocytic form of illness
Describe E. chaffeensis
Causes monocytic form of illness
The primary species causing human ehrlichiosis infection in the USA
What must a tick do in monocytic ehrlichiosis before transmission can occur?
It must feed for 48 hours
What does E. ewingii primarily infect?
The granulocytes of deer and dogs
What is Anaplasma phagocytophilum the agent of?
Human granulocytic ehrlichiosis
What is infection with Anaplasma phagocytophilum referred to as?
Anaplasmosis
Where is Anaplasma phagocytophilum predominantly found?
In granulocytes
Describe A. platys
Infects platelets
Causes infectious cyclic thrombocytopenia in dogs
What is E. canis transmitted by?
The brown dog tick
Which Ehrlichia spp causes the most potentially sever clinical presentation?
E. canis
What is present in acute cases of ehrlichiosis?
Reticuloendothelial hyperplasia Fever Lymphadenopathy Splenomegaly Thrombocytopenia
What is common during the acute phase of E. canis infection in dogs?
Thrombocytopenia
What does vasculitis induce with E. canis?
A thrombocytopenia and hemorrhagic tendencies
What is a common finding in canine granulocytic ehrlichiosis?
Polyarthritis
What is important since thrombocytopenia is consistent finding with ehrlichiosis infections?
A platelet count screening test
How should the treatment of suspected ehrlichiosis cases be handled?
They should nerve be delayed or withheld
What is the drug of choice for infection with Ehrlichia and Anaplasma spp?
Doxycycline
What does heartwater/cowdriosis affect?
Cattle
Sheep
Goats
Antelope
Where is heartwater/cowdriosis found?
Throughout sub-Saharan Africa and in parts of the Caribbeam
What is heartwater/cowdriosis caused by?
Ehrlichia ruminantium
What is heartwater/cowdriosis characterized by?
Fever Nervous signs Hydropericardium Hydrothorax Ascites Edema of the lungs High mortality
When can clinical signs of heartwater be seen?
Within 14 to 28 days after an infected tick feed on a ruminant host
What is the reason for concern about heartwater/cowdriosus?
Bont Ticks have been identified in the US
How can the death rate from heartwater/cowdriosis be reduced?
Early treatment with tetracyclines
