Lecture 28 - Rickettsiales Flashcards by Raegan Chambers

What type of pathogen is Rickettsiales?

Obiligate intracellular parasites

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What animals do Rickettsiales prefer?

Vertebrates + Arthropods + pretty much all eukaryotes

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What part of the Rickettsiales’ life cycle do ticks blood-feeding arthropod play?

Host
– and –
Vector

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What is one of the most important reservoir host for Rickettsiales?

Ticks

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What kind of host are humans in the Rickettsiales life cyle?

Accidental

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What are the genera of Rickettsiales that we are concerned with?

Rickettsia + Anaplasma + Erlichia

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How does rickettsia differ from anaplasma and erlichia?

Erlichia + Anaplasma are both in the family Anaplsmatacaea

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What are the structural characteristics of Rickettsiaceae?

Gram- negative

Pleomorphic coccobacilli

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How do Rickettsiaceae enter the host cell?

Induces phagocytosis
Escapes phagosome
Grows in cytoplasm and/or nucleus

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What cell type does Rickettsiaceae prefer to invade and grow?

Endothelial cells

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What happens when Rickettsiaceae takes up residence in the endothelial cells?

Necortizing vasculitis

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What are the downstream effects of necrotizing vasculitis?

Increased vascular permeability
– leading to –
Edema + Hemorrhage + Hypovolemia

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What are the major clinical problems seen with a Rickettsiaceae infection?

Encephalitis + Nephritis + Myocarditis

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What disease does Rickettsia rickettsii cause?

Rocky mountain spotted fever

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What ticks commonly carry Rickettsia rickettsii ?

American dog
Brown dog
Rocky mountain wood

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What tick is present in AZ that carries Rickettsia rickettsii ?

Brown dog tick

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When in the US are the most cases in dogs of RMSF seen?

March to October

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How old are most dogs that come down with RMSF?

less than 3 years old

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What parts of the US most commonly have RMSF?

South central + Southeastern

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What are the mammalian reservoirs for Rickettsia rickettsii ?

Wild rodents + other small mammals

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What are the early signs of Rickettsia rickettsii infection in a dog?

Fever + V/D + Achey + Edema + Coughing

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What neurological disturbances are seen in dogs with Rickettsia rickettsii ?

Depression + Stupor + Ataxia + Tremors

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What occurs in severe cases of Rickettsia rickettsii in dogs?

Acral necrosis

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What is the treatment for Rickettsia rickettsii ?

Doxycycline
– or –
Tetracycline

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When should treatment for Rickettsia rickettsii be started?

ASAP, do not wait for diagnostics

What are the structural characteristics of Anaplasmataceae?

Gram-negative | Pleomorphic coccobacilli

What types of cells do Anaplasmataceae bacterias tend to infect?

Ones of hematopoietic origin

What is the most common blood cell type that Anaplasmataceae grow in?

Leukocytes

Where do Anaplasmataceae multiply?

Within membrane-boudn structures called morulae

What are the three Anaplasmas that are important to us?

Marginale Platys Phagocytophilum

What does A. marginale like to infect?

RBC's of ruminants

What does A. Platys like to infect?

Platelets of canids

What is unique about A. Platys?

ONLY PATHOGEN TO INFECT PLATELETS

What does A. Phagocytophilus like to infect?

Granulocytes + Monocytes of mammals

What animals can be infected with A. Marginale?

Domestic + Wild ruminants

What disease does A. Marginale cause in cattle?

Bovine anaplasmosis

Where in the US does A. Marginale tend to infect cattle?

Southeast Midwest Western mountain region CA

What is the presentation of A. Marginale in a cow that is

Subclinical infection

What is the presentation of A. Marginale in a cow that is 6m to 3 years old?

Serious illness possible

What is the presentation of A. Marginale in a cow that is > 3 years old?

30 to 50% mortality rate

What are the two vectors most commonly spreading A. Marginale?

Black horse fly (Blood-feeding flies) -- and -- Tick ( Demacentor spp.)

What type of vector is the black horse fly?

Mechanical

What is seen in cattle that survive a A. Marginale infection?

Chronic, lifelong subclinical infections (carrier state)

What is the clinical presentation of A. Marginale in cattle?

Fever + Anemia + Icterus | Pregnant cows can abort

What is another name for A. Marginale infection in cattle?

Yellow bag -- or -- Yellow fever

What can be seen histologically that will hint at a A. Marginale infection?

Inclusion bodies in RBC's

When is the only time a blood smear is successful at diagnosing a A. Marginale infection?

Early in disease

What is the antibiotic treatment for A. Marginale?

Tetracycline -- or -- Imidocarb

What happens with treatment in severe cases of A. Marginale ?

Blood transfusion

What can be used to prevent A. Marginale infections?

No USDA approved Vxn

What does A. Platys most commonly infect?

Dogs

Where is A. Platys most commonly found?

All over the world

What is main vector for A. Platys?

Brown dog tick

What does A. Platys cause in dogs?

Infectious canine cyclic thrombocytopenia

What is the platelet count in a dog with A. Platys induced ICCT?

How oftens does A. Platys cycle in dogs?

every 1 to 2 weeks

What are the signs a dog is infected with A. Platys?

Fever + Petechiae/Ecchymoses + Epistaxis + Uveitis

What is used to diagnose A. Platys in dogs?

Morulae seen in stained platelets hard to find even in acute disease In-house ELISA test

What is the treatment for A. Platys?

Doxycycline

Where is A. phagocytophilum seen in the US?

Northeastern North central West coast

What does A. phagocytophilum tend to infect?

Mammals, wide range

What are the main mammal reserviors of A. phagocytophilum ?

Wild rodents

What is the vector for A. phagocytophilum?

Blacklegged ticks

What two animals see the most noticable diease with A. phagocytophilum infection?

Dogs -- and -- Horses

What disease is seen in dogs and horses with A. phagocytophilum?

Canine/Equine | Granulocytic anaplasmosis

What are the common signs of Canine Granulocytic anaplasmosis?

Fever + Lethargy + Anorexia + Lameness

What are the common signs of Equine Granulocytic anaplasmosis?

Same as dog | + Limb edema + Petechia + Icterus

What is seen in cats with A. phagocytophilum ?

Asymptomatic

What is ruminants are most affected by A. phagocytophilum ?

Sheep + Cattle

What happens when sheep or cattle are infected with A. phagocytophilum ?

Tick-borne fever

Where is tick-borne fever seen in the world?

Europe + S. Africa + India | NOT US

What is seen in humans with A. phagocytophilum ?

Asymptomatic most of the time

What are some methods to diagnose A. phagocytophilum ?

Morulae in stained neurophils - hard to find | In-house ELISA

What is the treatment for A. phagocytophilum ?

Tetracyclines Oxy - Horse + ruminants Doxy - Dogs

What are the three ehrlichia species that can affect dogs?

Chaggeensis Canis Ewingii

What does E. Canis cause in dogs/

Canine monocytic ehrlichiosis

Where is E. Canis seen?

Worldwide

What mammals are infected by E. Canis ?

Dogs and other Canids

What kind of hosts are Canids to E. Canis ?

Reservior host

What is the main vector for E. Canis ?

Brown dog tick

What animals can have rare infections of E. Canis?

Cats + Ruminants + Humans

What does E. Ewingii cause in dogs?

Canine Granlocytic Ehrlichiosis

Where is E. Ewingii found in the US?

Southeastern + South central

What is the main reservoir host for E. Ewingii?

White-tailed deer

What is the main vector for E. Ewingii?

Lone star tick

What does E. chaffeensis cause in dogs?

Mild, unnamed ehrlichiosis in dogs

Where is E. chaffeensis found in the US?

Southeaster + South central + Mid-Atlantic

What is the main reservoir host for E. chaffeensis?

White-tailed deer

What is the main vector of E. chaffeensis in the US?

Lone star tick

What does E. canis have tropism for?

Monocytes + Macrophages

What does E. Ewingii have tropism for?

Granulocytes

What does E. chaffeensis have tropism for?

Monocytes

What is seen with acute CME?

Fever + Lethargy + Anorexia + V/D | Lameness/Stiffness

What happens if some dogs dont recover from acute CME?

Persistent subclinical infection occurs for months to years

What is seen with persistent subclinical CME infection?

Intermittent fever + Mild thrombocytopenia + Anemia

What happens if a dog doesn't recover from persistent subclinical CME infection?

Chronic CME infection occurs

What breed is most likely to get a Chronic CME infection?

German Shepherd

What is seen in CGE that is different then CME?

Milder form | Stiff gait + Musculoskeletal problems

What is seen with infections caused by E. Chaggeensis?

Mild signs - fever + Thrombocytopenia

What is the problem with using blood smears to diagnosis different Ehrlichias?

hard to find | E. ewingii + A. phagocytophilium cannot be told apart

What does ELISA in-house tests test for?

Ab's to E. Canis + E. ewingii | But E. Chaffeensis may cross react

What is the treatment for ehrlichia?

Tetracycline

What is a Neorickettsia?

Obiligate intracellular symbiont of flukes

What are the two species of Neorickettsia that we are concerned with?

N. Helminthoeca -- and -- N. Risticii

What does N. Helminthoeca cause in dogs

Salmon poisoning disease

What does N. Risticii cause?

Potomac horse fever

What is the reservoir + host of N. Helminthoeca?

Intestinal fluke

What is the name of the intestinal fluke that N. Helminthoeca resides?

Nanophyetus salmincola

What does the adult stage of Nanophyetus salmincola infect?

Fish-eating mammals + birds

What does the larval stage of Nanophyetus salmincola infect?

Fish

Where are N. Helminthoeca infections most commonly seen?

Pacific northwest -- and -- Southern Brazil

What does N. Helminthoeca infect in dogs?

Monocytes + Macrophages Starts in small intestines Spreads to visceral + somatic LN

What are the symptoms of SPD?

Fever + nasal/ocular discharge + Weight loss + Depression

what is the mortality rate of an untreated dog with SPD?

90%

What is the treatment for SPD?

Parenteral oxytetracycline -- or -- Doxycycline

What is the reservoir + vector for N. risticii?

Intestinal flukes of bats | larval stage with in mayflies

Where is N. risticii found?

USA + Canada + S. America + Europe

What does N. Risticii have trophism for?

Monocytes + Intestinal macrophages + Mast cells + Enterocytes

What occurs when a horse is infected with Risticii?

Acute enterocolitis | Abortion

What are the clinical symtoms of PHF?

Fever + Anorexia + Depression + Colic

What happens in severe cases of PHF?

Sepsis + Dehydration

What is the treatment for N. Risticii in horse?

Parenteral oxytetracycline