Chapter 2: Ecology of tick vectors Flashcards
What is one of the first symptoms of lyme disease?
erythema migrans — a bulls eye rash that appears
(Only occurs in a percentage of cases — still majority about 70%)
What is the “cargo”?
the pathogen or parasite
What is zoonoses?
diseases transmitted by animal(s)
Who is Theobald Smith?
Christian scientists who was the first to prove a vector (tick) with protozoan parasite (Bayesian) (Texas cattle fever - 1889)
What are some common examples of zoonotic diseases?
- lyme disease
- rocky mounted spotted disease
- malaria
- African sleeping sickness
- Chagas’ disease
- yellow fever
- giardiasis
- babeiosis
What disease & its tick causes lyme arthritis?
- borrelia bacteria
- black legged tick —> lxodes scapularis ticks
How long must a tick be attached to transmit bacteria?
4-72 hours (Average=48 hours)
Which ticks cause the majority of lyme disease?
nymphal ticks
When are nymphal ticks most active?
late may-july
What are the stages in the parasites life history? How many legs does it have in each stage?
egg —> larvae (6-legged) —> nymph (8 legs) —> adult (8 legs)
What is transovarialt transmission?
the transmission of an infectious agent from parent to offspring via infection of the developing egg which subsequently results in infectious adult arthropods
Are male or female ticks larger?
Female
What is transstadial transmission?
What is a niche?
an organisms occupation — ticks are recyclers
What is a habitat?
an organisms “address” — high living grass for ticks
What is mutualism?
2 species living together with mutual benefit
what is symbiosis?
living together — either mutualism or parasitism
What are symptoms of alpha gal syndrome? (caused by lone star ticks saliva)
- red meat allergy
- hives abdominal cramping
-life threatening possible
What are treatments/management for alpha gal syndrome?
- diet change
- epinephrine
- antihistamines
What are the vectors (2) of rocky mountain spotted fever?
- wood tick —> dermacentor andersoni
- dog tick —> dermacentor variabilis
- lone star tick —> amblyomma americanum
* tick vectors remain infected for life
Is rocky mountain spotted fever a zoonotic disease?
yes
Where is Rocky Mountain Spotted Fever the highest?
US, Canada, highest incidences in Blue Ridge south-central US
How long does it take for the ticks to transfer bacteria of RMSF?
4-10 hours
Who first discovered & notated RMSF?
Howard Ricketts in 1896
How many cases of RMSF in the US?
until recently, 300-800 cases in US
Which vectors are most common for RMSF?
- most common in US is american dog tick
- most common in Virginia is lone star tick
Rickettsia rickettsii?
What treatments are given for RMSF (antibiotics)
Doxycycline most often given
- w/out treatment mortality reaches 20% (HIGH)
- w treatment mortality rate is less than 5%
What is an amplifying host?
a host in which the level of pathogen can become high enough that a vector such as tick feeds on it and will probably become infectious
What is a reservoir host?
a host that can harbor a pathogen indefinitely with no ill effects
- a single reservoir host usually primary host of a pathogen
What are symptoms of RMSF?
- Early: high fever, headache, myalgia, GI symptoms (quick, acute)
- late: rash (all over), photophobia, confusion, ataxia, seizures, cough, dyspnea, arrhythmias, jaundice, severe abdominal pin
- long term results: CNS deficits, amputations
What symptom does typhus affect?
rectoendothelial symptoms —> severe consequences can lead to death in a few dates
- spreads by macrophages
- similar to RMSF & can look similar
What is lyme disease (bacteria, vector, etc)?
- bacteria: borrelia sp.
- vector: “black legged” (deer or seed tick) —> i ixodes scapularis (or ixodes pacificus in west coast)
- 500,000 people in US annually
When was lyme disease recognized & where? Who identified first?
- Recognized in 1975-76 by Dr. A. Steere
- First identified by Dr. Willy Burgdorfer (1981) and Barbour and Benach
What are the 3 active stages of tick?
- larvae
- nymph
- adult
What are characteristics of the ticks?
does not fly or jump, attatches as host passes by
How long is the life cycle of a deer tick?
2 years — only feeds 3 times though
What are some hosts of the deer tick?
mice, vole, deer, other mammals (needs host at each of the 3 stages)
- white-footed mice are principal resevoir of infection where larval and nymphal ticks feed and become infected with the LD spirochete (lyme)
What is the bacteria of lyme?
Borrelia Burgdorferi
What primarily causes the variation in the bullseye rash (erythema migrants)?
- dosage (amount) of borrelia bacteria
- immune response
- borrelia variant (ID by PCR DNA)
What is the shape of borrelia?
large microaerophilic spirochete
How does the borrelia genome differ from other prokaryotes?
genome is linear, not circular, and has numerous copies rather than just 1 (one of the most complex bacteria)
What are the stages of lyme disease?
- primary (First) stage
What is the primary stage of lyme? (localized stage)
- Characterized by erythema migrants
- rash begins as small red spot @ bite site —> grows
- flu/COVID - like symptoms. (malaise, chills, fever, headache, stiff-neck, aches & pains)
What is the secondary stage of lyme?
- 2-8 weeks post rash
- involve heat & nervous system
- electrical conduction to heart impaired (arrhythmias)
- nervous system —> can lead to paralysis of facial muscles & impaired concentration
How does the Borrelia bacteria get into/move throughout body (pathogenesis)?
- introduced into skin — bite of infected tick
- migrate outward in radial fashion
- causes inflammatory reaction in skin (migration & inflammation — expanding rash)
- Host immunity initially suppressed (mult. of bacteria)
- bacteria enters bloodstream and circulates to other parts of the body
**bacteria does not cross the placenta
What is the tertiary (3rd) stage of lyme?
- within 6 months after rash (slowly disappear over years)
- characterized by arthritis (usually large joints — knee)
- symptoms develop in 60% of untreated cases
- chronic nervous system impairment may occur
How do you prevent and treat lyme disease?
- prevention same as RMSF
- antibiotics relatively effective in early stage disease
- less effective in late disease (bacteria not actively multiplying
What is the life cycle of lyme?
look at slide 37
Which tick only bites as adult?
american dog tick
Which bacteria causes Babesiosis (also deer tick)?
- Babesia
- has double ring
- can co-infect with borrelia to cause infectious malaria-like illness
-Life cycle similar - on the rice in PA and NY
What are the hosts for ticks?
- adult ticks lay eggs on white-tailed deer
- larval tick feeds on white-footed mouse (attracts disease)
- nymphal tick feeds on mouse — then human (bites and transmit disease)
(about 1 year)
What are Ehrlichiosis and anaplasmosis?
two tick-borne diseases
- Ehrlichiosis: common in dogs locally
- Anaplasmosis: second most commonly reported tick born disease after lyme
What is the toothed hypo stone? What does this implicate?
- intakes plant juice
- could have pre-fall implications for originally ingesting plants protein
