Lecture 19 4/22/24 Flashcards
What are the important characteristics of ticks?
-obligate blood sucking arthropods
-second most important pathogen vector for humans; first for animals
-affect wildlife, livestock, pets, and humans
-world wide distribution
Which features are used to identify ticks?
-basis capitulum
-scutum
-presence/absence of festoons
How can male ticks be distinguished from female ticks?
-females have a partial scutum
-males have a full scutum
What are the characteristics of hard ticks?
-present scutum
-anterior mouth parts that are visible from above
-one nymphal stage
-feeding time of several days
-female takes one blood meal
-female has one egg laying event w/ large quantity
What are the characteristics of soft ticks?
-absent scutum
-ventral mouth parts not visible from above
-several nymphal stages
-feeding time of 30-60 minutes
-female takes several blood meals
-female has several egg laying events w/ smaller egg quantities
What are the characteristics of Otobius megnini?
-soft tick
-often feed at night
-only larvae and nymphs are parasitic
-common on cattle
-can cause ear canal damage
-vector of Borrelia recurrentis
What are the types of hard tick host cycles?
-one host ticks: all three stages feed on same host without detaching; some Rhipicephalus spp.
-two host ticks: not common
-three host ticks: all three stages have separate feeding events; most common
Why is it important that ticks spread disease via their salivary glands?
the salivary glands are in the body, not the mouthparts, so it is okay if the mouthparts are left behind during removal
How can Ixodes spp. be identified?
anterior anal groove on ventral side of all life stages
What are the characteristics of Rhipicephalus sanguineus?
-aka brown dog tick
-mainly feeds on dogs
-hexagonal basis capitulum/Darth Vader helmet
What are the characteristics of Amblyomma americanum?
-aka lone star tick
-female has white spot on sputum
-long mouth parts
-short basis capitulum
What are the characteristics of Dermacentor variabilis?
-aka American dog tick
-ornate scutum
-all three palp segments appear stubby
What are the characteristics of Amblyomma maculatum?
-aka gulf coast tick
-long mouth parts
-short basis capitulum
-ornate scutum
What are the characteristics of Rhipicephalus annulatus?
-one host life cycle
-often seen in cattle
-“eradicated” from US, but occasionally comes into Texas
-“cattle tick” or “cattle fever tick”
-small, stubby palps
What are the characteristics of Rhipicephalus microplus?
-one host life cycle
-wider host range
-“southern cattle tick”
-small, stubby palps
What are the characteristics of Haemaphysalis?
-three host tick
-larvae and nymphs feed on birds and rabbits
-adults feed on larger mammals
-points on palps
Which species of Haemaphysalis are of importance?
-H. leporispalustris: rabbit tick
-H. chordeilis: bird tick
-H. longicornis: invasive tick with many hosts
What are the characteristics of Haemaphysalis longicornis?
-aka long-horned tick
-Asian tick recently introduced to US; started on east coast
-prefers cattle, sheep, and horses, but will feed on many hosts
-populations explode due to ability of female to reproduce without male
How do tick-borne diseases differ between direct and indirect?
-direct: tick causes the disease itself
-indirect: tick transmits an infectious organism
Which ticks are able to cause tick bites reactions?
all ticks, but esp. those with long mouthparts
What is the pathogenesis of tick bites?
-inflammation and blood loss
-deep painful bites are predisposed to bact. infections and myiasis
What are the possible results of tick bites?
-tick worry
-tick anemia
-tick pyemia
-secondary infections
-myiasis
How are tick bites treated and prevented?
-remove ticks and clean wounds
-provide supportive care
-provide topical or systemic parasiticides
Which species are associated with tick paralysis?
-D. andersoni
-D. variabilis
-A. americanum
-A. maculatum
-Ixodes holocyclus
What is the pathogenesis of tick paralysis?
-toxin is present in saliva
-acute ascending flaccid paralysis
How is tick paralysis diagnosed and treated?
-find and remove tick; observe response
-supportive care
-dip animal if possible
-antitoxin available to Ixodes holocyclus
What is transstadial transmission?
-pathogen is maintained within tick as it molts to next stage
-passed between different tick stages when they feed on infected hosts
What is transovarial transmission?
-pathogen maintained through vertical transmission within population
-transmitted to offspring via ova
Which bacterial diseases are spread via ticks?
-Lyme disease
-tularemia
-ehrlichiosis/anaplasmosis
-Rocky Mountain spotted fever
What are the characteristics of Lyme disease?
-caused by Borrelia burgdorferi
-vectors include Ixodes scapularis, pacificus, and ricinus
-maintained transstadially
-infection spread by nymphs and adults
How do rodents and white-tailed deer differ as reservoirs for Lyme disease?
-rodents can actually pass the bacteria to the tick
-white-tailed deer provide blood meals for already infected ticks, but cannot pass the bacteria
How do the clinical signs of Lyme disease differ between the subclinical, acute and chronic forms?
subclinical:
-no signs
-strong antibody titer
acute:
-erythema migrans
-flu-like symptoms
chronic:
-cardiac signs
-neurologic signs
-arthritic signs
What are the characteristics of Lyme disease in dogs and horses?
-serological screening of healthy animals can lead to overdiagnosis and/or overtreatment
-seropositive animals should be evaluated for proteinuria and co-infection; treated only if necessary
Which clinical signs are seen in Lyme disease cases in animals?
acute:
-no signs typically recognized
chronic:
-fever
-anorexia
-depression
-shifting
-leg lameness
-proteinuria
-muscle pain
-joint pain
What are the characteristics of Rickettsiae?
-intracellular gram neg.
-nonspecific clinical signs; flu-like signs, anemia, thrombocytopenia
-transstadial transmission
-treated with tetracyclines
What are the characteristics of Rocky Mountain spotted fever?
-caused by Rickettsia rickettsii
-invades endothelial cells of small vessels
-vectors include D. andersoni, D. variabilis, and R. sanguineus
-transstadial and transovarial transmission
-amplifiers include wild rodents, humans, and dogs
What are the clinical signs of Rocky Mountain spotted fever in humans?
-fever
-headaches
-joint and muscle pain
-generalized rash
-death due to renal failure, shock, and/or encephalitis
What are the clinical signs of Rocky Mountain spotted fever in dogs?
-fever
-anorexia
-lymphadenopathy
-polyarthritis
-coughing/dyspnea
-vomiting and diarrhea
-edema
Why is it important to do serological testing for Rocky Mountain spotted fever instead of PCR?
-pathogen lives inside cells, not in samples that can be run on PCR
-must detect immune response
What are the characteristics of tropical canine pancytopenia?
-caused by Ehrlichia canis
-invades monocytes/macrophages
-replicate in morulae
-infects dogs and wild canids
-vector is R. sanguineus
-predilection for german shepherds
-treated with doxycycline
What are the acute clinical signs of Ehrlichia canis?
-fever
-anorexia
-lethargy
-depression
-dyspnea
-lymphadenopathy
-thrombocytopenia
What are the chronic clinical signs of Ehrlichia canis?
-pancytopenia
-pyrexia
-ocular abnormalities
-scrotal and limb edema
-hemorrhage
-epistaxis
-weight loss
-shock
-death
What are the characteristics of canine granulocytic ehrlichiosis?
-caused by Ehrlichia ewingii
-invades granulocytes
-vector is A. americanum
What are the clinical signs of Ehrlichia ewingii in dogs?
-often asymptomatic
-mild fever
-anorexia
-lethargy
-midl pancytopenia
-polyarthritis (chronic)
What are the characteristics of equine and canine granulocytic ehrlichiosis?
-caused by Anaplasma phagocytophilum
-invades granulocytes
-zoonotic
-vectored by Ixodes spp.
What are the clinical signs of Anaplasma phagocytophilum in dogs and horses?
-usually mild, seasonal disease
-fever
-lethargy
-edema
-pancytopenia
-petechiae
Which tick spreads Cytauxzoon felis?
Amblyomma americanum
Which tick spreads Hepatozoon americanum?
A. maculatum; must eat tick to get disease
What are the potential testing options for tick-borne diseases?
-serological testing
-blood smear for Cytauxzoon and Babesia
-PCR on blood, tissue, or ticks
What are the key points of tick control?
-year-long prevention for pets
-keep cats indoors
-advise clients of potential for TBD
-tick ID
-removing low lying vegetation and leaf litter
-excluding wildlife
-deer pop. control
