Flashcards in Exam #8: Zoonotic & Vector Borne Bacterial Infections II Deck (59):
List the characteristics of Borelia.
Neither Gram -/+ (Gram negative like)
What diseases do Borrelia cause?
- Lyme Disease
- Relapsing Fever
What species of Borrelia cause Lyme disease?
What is the leading vector-borne disease in the US?
What is the major vector of Lyme Disease?
Lxodes spp. (hard tick)
*hard ticks transmit Lyme disease
What animals are the reservoirs for Lyme Disease?
When is the early stage of Lyme Disease most frequently seen?
What are the symptoms of early stage 1 Lyme Disease?
- Starts as a macule or papule lesion that enlarges to a bull's-eye rash called "erythema migrans"
*Erythema migrans is pathognomonic for Lyme Disease
What is the name of the bull's eye rash?
What are the symptoms of early stage 2 Lyme Disease?
Disseminated Infection: bacteria disseminate via the bloostream
- Cardiac dysfunction
- Neurologic signs consistent with meningitis and encephalitis
What are the symptoms of late stage Lyme Disease?
- One ore more joints with the knee being the joint most commonly infected
- Skin discoloration (grey & ashy)
- Neurologic complaints (numbness, memory loss)
How is Lyme Disease diagnosed?
- physical findings
- hx of exposure
How is Lyme Disease streated?
Doxycycline & amoxicillin
How is Lyme Disease prevented?
Limit tick exposure
What causes epidemic relapsing fever?
- Louse-borne (lice)
- this is NOT zoonotic
- tranmission is human to human via the louse
What causes endemic relapsing fever?
*This is most common in the US
Describe the pathogenesis of relapsing fever.
- Bite from a louse or tick
- Dissemination via multiple organs through bloodstream
- Evasion of the immune system via antigenic variation
- Infection results in febrile & afebrile cycles, hence "relapsing fever"
What are the symptoms of relapsing fever?
Symptoms last 3-7 days resolve, and then return after 7 days
Outline the antigen/antibody presence in blood smear & symptoms of relapsing fever.
Week 1= Latent period progressing to fever
- Specific antibody produced
- Fever improves
- Antigenic variation
Week 2= progressive bactermia leading to fever again
- Antibody produced
- Fever resides
- Antigenic varation
How is relapsing fever diagnosed?
- Microscopy- Giemsa stained blood smear
- Culture requires special media
- Serological and molecular techniques can be used to confirm diagnosis
How is relapsing fever treated?
Tetracycleine or erythromycin
How is relapsing fever prevented?
Limit exposure to arthropod vectors
List the characteristics of Rickettsia.
- Very small gram (-) coccobacilli
- Obligate intracellular pathogens-- facilitate their own uptake into endothelial cells, escape from phagosome into the cytoplasm-->lead to focal lysis of filopodia
- Transmitted via arthropod bite
Describe the pathogenesis of Rickettsia.
Organisms infect vascular epithelium or small blood vessels
What disease is caused by Rickettsia?
Rocky Mountain Spotted Fever (RMSF)
What is Rocky Mountain Spotted Fever?
- Most important rickettsial disease in the US
- A severe systemic febrile disease
What are the two vectors for RMSF?
Dog tick= NOT in the Rocky Mountains
Wood tick= Rocky Mountian
Where do most of the cases of RMSF occur?
NOT in the Rocky Mountains i.e. most commonly transmitted by the Dog Tick, not in the Rockies
What are the symptoms of RMSF?
- Initially presents with fever & rash over the extremities
- Rash becomes raised and spreads to the torso (centripital spread i.e. outside-->in vs. centrifugal)
- Pulmonary edema
- Renal failure
- GI hemorrhage
How is RMSF diagnosed?
- Epidemiology & clinical signs
- Serology (severe disease may develop before antibody titers are high enough for diagnosis)
- Molecular or immunohistochemical techniques
How is RMSF treated?
How is RMSF prevented?
Limiting exposure to ticks
List the characteristics of Ehrlichia.
Small gram (-) intracellular pathogens
What do Ehrlichia parasatize?
Primarily monocytes & granulocytes
What is a morulae? What are morulaes associated with?
Ehrlichia replicate & form colonies within vacuoles known as morulae
What causes HME? What is HME? What is the principle vector?
HME= Human monocytic ehrlichiosis
- Ehrlichia chaffeensis
Lone star tick
What causes HGE? What is HGE? What is the principle vector?
HGE= Human granulocytic ehrlichiosis
- Anaplasma phagocytophilum
Describe the pathogenesis of Ehrlichia & Anaplasma.
- Intracellular location protects from humoral immune response
- Bacteria derail phagolysozome maturation
- Activating macrophage with INF-gamma appears to resolve infection
What are the symptoms of Ehrlichia & Anapalsma?
- 60 % are asymptomatic
- Remaining 40% are severe enough to require hospitalization
Multi-system zoonosis with malaise, fever, chills, headache, and myalgia
- Petechial rash
- Resp. distress
- CNS dysfunction
How is Ehrlichiosis diagnosed?
- Serological & molecular techniques
- Detection of morulae in blood smear
How is Ehrlichiosis treated?
List the characteristics of Coxiella burnetii.
- Small Gram (-) pleomorphic bacterium
- Obligate intracellular pathogen
- Reside and replicate in fully acidified phagolysosomes i.e. they don't interrupt phagolysosome fusion like some of the others that we have covered
What is the difference between a small cell variant & large cell variant?
Small cell= have some characteristics of spores
- Resistant to high temperature, osmotic pressure, and UV light
- Can survive in the environment for months
*This is the form of C. burnetii that is infective
Large cell= small cell variants that have grown into large cells; these then divide and the cycle repeats
What is the primary reservoir for Coxiella burnetii?
*Note that ticks are an important vector for animals, but NOT man
How is Coxiella burnetii transmitted?
Inhalation of small variants
What are the symptoms of acute Query fever?
- Generalized disease resembling flu
- Followed by fever, chills, malaise, arthralgias, myalgias, severe headache, and photophobia
- Pneumonia may develop
- Abnormal liver function, CNS dysfunction, and vascular inflammation may be present
*Note that infection during pregnancy may lead to premature birth, abortion, or stillbirth
What are the symptoms of chronic Query Fever?
- Mainly endocarditis or hepatitis
- Acute signs of infection absent
How is Query fever diagnosed?
Molecular and serological techniques
How is Query Fever treated?
How is Query Fever prevented?
Inactivated whole cell vaccine
List the characteristics of Bartonella.
Small slight curved Gram (-)
What two human diseases are caused by Bartonella?
Bartonella quintana-->Trench Fever
Bartonella henselae-->Cat Scratch Fever
How is Bartonella transmitted?
Trench fever is transmitted by the human body louse
- It is present in the feces of lice
- As the louse is taking a blood meal, when you scratch & break the skin, you introduce the feces into your wound
*Generally seen in the homeless population
Cat Scratch Fever is transmitted by flea feces that are introduced into the body via a cat scratch or bite
What are the symptoms of Trench Fever?
Relapsing fever, headache, and dizziness that lasts 1-3 days & recurs every 4-6 days
How is Trench Fever diagnosed?
- Isolation of organisms from blood
How is Trench Fever treated?
Aminoglycoside (gentamicin) or macrolide (erythromycin)
What are the symptoms of Cat Scratch Fever?
- Fever and lymphadenopathy in the region of inoculation
- A papule may develop at the site of inoculation
- Symptoms generally resolve without complication
How is Cat Scratch Fever diagnosed?
- Molecular analysis