Lecture 35 11/18/24 Flashcards
What are the general characteristics of tick-borne diseases?
-ticks are well-known zoonotic pathogen vectors
-tick-borne diseases are threats to both human and animal health
-tick-borne diseases have more than doubled in the US and account for the majority of vector-borne diseases
What are the characteristics of the questing behavior practiced by ticks?
-spend 90% of life off-host
-actively climb onto leaves or other litter
-wait for hosts to pass by so they can attach
-stimulated by CO2 and movement
Which anatomic structure allows for ticks to remain attached to their hosts?
barbed chelicerae
How long do different tick-borne pathogens need to transmit to the host after a tick bites?
Rickettsia and Ehrlichia: 12 to 24 hours
Lyme: greater than 24 hours
What are the characteristics of Dermacentor spp.?
-includes American dog tick and wood tick
-frequently bites
-disease transmission occurs less frequently
-harbors diseases such as Rocky Mountain spotted fever and tularemia
What are the characteristics of Amblyomma spp.?
-includes lone star tick
-mostly in the southern US
-harbors diseases such as human monocytic ehrlichiosis and tularemia
What are the characteristics of Ixodes spp.?
-includes black-legged tick and deer tick
-carries most diseases
-diseases include Lyme disease, human anaplasmosis, babesiosis, Powassan encephalitis, and ehrlichiosis
What are the characteristics of Asian long-horned ticks?
-not normally found in the Western hemisphere; invasive
-found on pets, livestock, wildlife, and people
-female ticks can lay eggs and reproduce without mating
What are the characteristics of Borrelia burgdorferi?
-causes Lyme disease
-gram-neg.
-spirochete bacteria
How is Lyme disease transmitted?
-Ixodes scapularis in upper midwest and New England
-Ixodes pacificus in Western US
-rare occurrence of transplacental/transmammary transmission
What are the characteristics of outer surface proteins on Borrelia spp.?
-tick feeding on a new host triggers change in OSP expression
-OSP-A helps Borrelia spp. adhere to tick’s gut to multiply
What happens once a tick attaches to a host, in terms of Borrelia bergdorferi?
-Borrelia multiply quickly within tick
-decreased expression of OSP-A
-increased expression of OSP-C
-OSP-C helps Borellia move towards salivary glands
-spirochetes enter new host after approx. 48 hrs
What are the characteristics of Lyme disease prevalence and incidence?
-incidence depends entirely on location
-in endemic areas, dogs can have up to 90% seroprevalence
-seasonal dist.; greater onset of illness in June and July
What are the risk factors for Lyme disease?
-living or vacationing in tick-endemic areas
-walking through dense vegetation/along forest edges
-occupational exposure
What is the pathogenesis of Lyme disease?
-spreads by tissue migration
-moves through collagen and connective tissue
-causes classic bullseye rash in people
-targets joints, kidneys, and heart
-changes shape and surface proteins to avoid immune clearance and remain persistent
-incubation in dogs can last 2-5 months
What is the typical human signalment for Lyme disease?
young males 5-19 years old or males older than 30 years old
What is the typical canine signalment for Lyme disease?
-all breeds susceptible
-outdoor dogs exposed to ticks
-usually infected as young adults
What are the clinical signs of early localized Lyme disease?
-erythema migrans/bullseye rash
-flu-like symptoms including fever, headache, muscle pain, and joint pain
What are the clinical signs of Lyme disease in dogs?
-fever
-anorexia
-shifting leg lameness
-lameness that waxes and wanes
-regional lymphadenopathy
-self-limiting infection; resolves in a few weeks
What are the characteristics of canine Lyme nephritis?
-seen in young labradors, goldens, and shelties
-anorexia, vomiting, lethargy, PU/PD, and hypertension occur
-glomerulonephritis, interstitial nephritis, and tubular necrosis possible
-immune-mediated disease
-rapidly progressive and often fatal
