What are the two tick born diseases?
Rocky Mountain Spotted Fever & Lyme Disease
What are the symptoms of Rocky Mountain Spotted Fever?
• Distinguished by initial rash of faint pink spots
- Appears first on palms, wrists ankles and soles of feet
• Rash eventually spreads to other parts of the body
- Spots become raised bumps and are hemorrhagic
What can occur with Rocky Mountain Spotted Fever when body systems are involved?
Shock or death can occur when certain body systems become involved - Especially the heart and kidney
What is the characteristic of the rash for Rocky Mountain Spotted Fever?
Non Itchy rash
What is the pathogen of Rocky Mountain Spotted Fever?
Obligate, intracellular bacterium - Requires host organism for survival
What is the Pathogenesis for Rocky Mountain Spotted Fever?
• Disease acquired from bite of a tick infected with R. rickettsii
• Bacteria are released into blood and taken up by cells lining vessels (Endothelia Cells)
• Bacteria enter cells through endocytosis - After endocytosis, cell leaves protective phagosome
• Bacterial endotoxin released in bloodstream can cause disseminated intravascular coagulation - This is recognized by shock and generalized bleeding
KNOW THIS PATHWAY!!! ENDOTHELIA CELLS, ENDOCYTOSIS, and ENDOTOXIN
What is the Epidemiology for Rocky Mountain Spotted Fever?
• Zoonotic disease - Spread from animals to humans
• Occurs in areas in the US, Canada and Mexico - Highest incidence in US is in south Atlantic and south/central US
• Maintained in several species in nature - Primarily in ticks and certain mammals
• Main vectors include wood tick, Dermacentor andersoni and the dog tick, Dermacentor variabilis - Tick vectors remain infected for life
What does the endotoxin released by Rickettsia rickettsii cause?
Intravascular coagulation which is a deadly complication
Bleeding from all openings and can go into Hypovolemic shock
What is Hypovolemic shock?
Shock caused by severe blood or fluid loss
How is Rocky Mountain Spotted Fever prevented?
• No vaccine currently available
• Prevention should be directed towards:
- Avoiding tick infested areas
- Use protective clothing
- Use tick repellents containing DEET
- Carefully inspecting body (Especially dark, moist areas)
- Removing attached ticks carefully (Avoid crushing and contaminating bite area)
How is Rocky Mountain Spotted Fever treated?
Blood transfusion, steroids, and drugs
What is the treatment for Rocky Mountain Spotted Fever?
• Antibiotics are highly effective in treatment if given
early - Doxycycline and chloramphenicol used most often
• Without treatment overall mortality reaches approximately 20%
• With early diagnosis and treatment, mortality rates drop to less than 5%
Sooner treated the better
What are the stages of infectious diseases?
Be able to label on a chart
Incubation Period - Organism is replication
When was Lyme Disease discovered?
Disease recognized in mid 1970's in Lyme, Connecticut
• First identified by Dr. Willy Burgdorfer
What is the pathogen of Lyme Disease?
• Borrelia burgdorferi
• Large microaerophilic spirochete
What happens during the first stage of Lyme Disease?
Migrans, Influenze signs, and Bulls Eye Rash
• Characterized by erythema migrans (skin rash) and
enlargement of lymph nodes
• Rash begins as small red spot at the site of a tick bite and slowly enlarges
• Other symptoms influenza like and include malaise, chills, fever, headache, stiff neck, joint and muscle pain and backache
What happens during the second stage of Lyme Disease?
Begin 2 to 8 weeks post rash
Involve heart and nervous system
- Electrical conduction to heart is impaired
- Nervous system involvement leads to paralysis of facial muscles and impaired concentration and emotional instability
What happens during the third stage of Lyme Disease?
Characterized by arthritis - Usually of the large joints such as the knee
Symptoms develop in 60% of untreated cases
- Begin within 6 months after rash
- Slowly disappear over years
Chronic nervous system impairment may occur
How are the stages treated?
Stages 1 and 2 can be treated with antibiotics but not third stage
What is the pathogenesis of Lyme Disease?
Bacteria introduced into skin through bite of infected tick
• Once in skin, bacteria migrate outward in radial fashion
• Causes inflammatory reaction in the skin (Migration and inflammation produces an expanding rash)
Host immunity is initially suppressed
• Allows for continued multiplication of bacteria
Bacteria enter bloodstream and circulate to other parts of the body
• Bacteria do not cross the placenta
What is the Epidemiology for Lyme Disease?
• Disease is zoonotic
• Wide spread in US
• Several tick species implicated as vectors
- Most important is black-legged tick, Ixodes scapularis
How is Lyme Disease prevented?
- No vaccine currently available - Prevention should be directed towards:
• Avoiding tick infested areas
• Use protective clothing
• Use tick repellents containing DEET
• Carefully inspecting body
- Especially dark, moist areas
• Removing attached ticks carefully
- Avoid crushing and contaminating bite area
How is Lyme Disease treated?
- Antibiotics relatively effective in early stage disease
- Less effective in late disease
- Presumably because bacteria are not actively multiplying