Arthropod Bites II

Question 1

Colorado Tick Fever Virus Genome and Structure

Answer 1

Non‐enveloped, dsRNA virus

Question 2

Colorado Tick Fever Virus Vector and transmission

Answer 2

• Tick (Dermacentor andersoni)
• Brief tick encounters (unlike Borrelia, Babesia, etc.)
• Focus: mountainous regions of western US
• Seasonal (May‐July)
• Virus replicates in bone marrow stem cells

Question 3

Colorado Tick Fever Virus Clinical

Answer 3

• High fever, chills, arthralgia, myalgia, headache (1‐3 days)
• “Saddleback fever”
• Prolonged recovery: weeks to months

Question 4

Colorado Tick Fever Virus Diagnosis and control

Answer 4

-Travel history, serology, virus isolation from blood -Prevent tick bites

Question 5

Malaria (Plasmodium spp.) Symptoms

Answer 5

-Non‐specific febrile illness, with fever, chills,
headache, body aches, weakness, N/V/D
-Severe: Organ damage secondary to RBC lysis and accumulation, Hemoglobinuria; kidney failure, Acute respiratory distress syndrome

Question 6

Malaria Diagnosis

Answer 6

Visualization of parasites in blood smear

Question 7

Babesia microti General

Answer 7

Protozoan and sporazoan

Question 8

Babesia microti Lifecycle

Answer 8

• Vector: “Deer tick”: Ixodes scapularis

- Reservoir: mice

Question 9

Babesia microti Clinical course

Answer 9

• Replicates in erythrocytes, and RBC lysis (hemolytic anemia)
• 1‐4 week incubation period
• Fever, malaise, headache, chills, fatigue
• A febrile hemolytic anemia
• 2‐4 week recovery

Question 10

Babesia microti Complications

Answer 10

Renal failure

Question 11

Babesia microti Diagnosis

Answer 11

Thin blood smears & parasite visualization

Question 12

Babesia microti Ring forms

Answer 12

-ONLY ring forms are seen in blood smears
-RBCs may contain multiple rings (like P. falciparum)
-Can be vacuolated (white areas within ring, below)
 Often appear in PAIRS OR TETRADS (MALTESE CROSS)
 Also lack pigmentation or stippling
 RBCs are also not enlarged (unlike P. vivax, ovale)

Question 13

Babesia microti control

Answer 13

Avoid tick bites

Question 14

Yersinia pestis General

Answer 14

• Gram (‐) facultative rod

- Closed “safety‐pin” appearance in aspirates of swollen lymph nodes (buboes)

Question 15

Yersinia pestis Pathogenesis

Answer 15

• Purpura, ecchymosis, &/or gangrene
• Bubonic Plague: Buboes painful, tender, enlarged lymph nodes
• Multisystem involvement: Spleen, liver, lungs, CNS

Question 16

Yersinia pestis Lab identification

Answer 16

• Microscope or culture
• Lymph node aspirate or sputum
• Giemsa, fluorescent Ab staining

Question 17

Yersinia pestis Prevention

Answer 17

-Rodent control, vaccine

Question 18

Coxiella burnetii: Q Fever General

Answer 18

• Outbreaks in Europe
• Obligate intracellular pathogen (Formerly Rickettsiae)
• Gram negative pleomorphic coccobacillus
• Does not Gram stain: Gimenez stain used
• 2 forms: Small Cell Variant and LCV

Question 19

Coxiella burnetii: Q Fever Reservoirs/Transmission

Answer 19

• Sheep, goats, cattle, dogs, cats, birds, rodents, ticks, NO ARTHROPOD VECTOR
• Infected animals shed bacteria: in feces, urine, milk
• Contract by aerosols (or ingestion)

Question 20

Coxiella burnetii: Q Fever Pathogenesis

Answer 20

 Alveolar macrophages primary host cell
 Acidic pH (4.5) in phagolysosome SCV LCV
 Slow intracellular growth of LCV to generate LCV and SCV
 SCV released and infect new cells
 Antigenic variation: two phase variants
 Phase I: full LPS; more infectious
 Higher antibody response during chronic infections
 Phase II: short LPS with no O‐antigen
 Higher antibody response during acute infections

Question 21

Coxiella burnetii: Q Fever Clinical Symptoms

Answer 21

• Nationally Reportable
• Asymptomatic
• Incubation period 20 days
• Acute: chest pain, clay‐colored stool, cough, fever, headache, jaundice, muscle pain, rash (not common)
• Chronic: chills, fatigue, night sweats, fever, culture‐negative endocarditis, osteomyelitis

Question 22

Yersinia pestis Virulence factors

Answer 22

-capsule, LPS, adhesins, type III secretion, other protein toxins

Question 23

Yersinia pestis Reservoirs

Answer 23

Reservoir(s): rodents, Xeopsylla cheopsis (rat flea)

-Bacterial replication occurs in flea gut

Question 24

Coxiella burnetii

Answer 24

• SEROLOGY

- Dont culture-highly contagious. Lvl 3 clearance

Question 25

Brucella

Answer 25

• Facultative intracellular pathogens, aerobic, slow growing, Gram‐negative coccobacilli or small rods, Catalase and oxidase positive
• Chronic animal infections?: Sheep, goats, cattle, deer, elk, pigs, dogs, others

Question 26

Brucella Diagnosis

Answer 26

• Blood cultures (gold standard), but bone marrow cultures more sensitive
• Serology

Question 27

Brucella Pathogenesis

Answer 27

• Multiply in phagocytic cells

- Non‐endotoxic LPS blocks innate immune responses

Question 28

Brucella Clinical symptoms

Answer 28

• flu‐like illness
• Severe: CNS involvement, endocarditis
• Chronic form: recurrent fevers, joint pain, and fatigue

Question 29

Leptospirosis General

Answer 29

Tightly coiled spirochetes; flagellated (2 flagella)

Question 30

Leptospirosis Transmission

Answer 30

Ingestion; direct contact

Question 31

Leptospirosis Clinical Manifestations

Answer 31

• Fever, flu‐like illness
• Hepatitis, jaundice & hemorrhage in the liver;
• Uremia & bacteriuria in the kidney
• Aseptic meningitis

Question 32

Leptospirosis Lab identification

Answer 32

• Culture (Blood, CSF & urine) to check for rise in agglutinating Ab

Question 33

Leptospirosis Prevention

Answer 33

-Rodent control, protective clothing, prophylactic penicillin