Lecture 19 4/22/24 Flashcards by Danika Boltz

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

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Which features are used to identify ticks?

-basis capitulum
-scutum
-presence/absence of festoons

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How can male ticks be distinguished from female ticks?

-females have a partial scutum
-males have a full scutum

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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

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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

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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

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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

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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

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How can Ixodes spp. be identified?

anterior anal groove on ventral side of all life stages

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What are the characteristics of Rhipicephalus sanguineus?

-aka brown dog tick
-mainly feeds on dogs
-hexagonal basis capitulum/Darth Vader helmet

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What are the characteristics of Amblyomma americanum?

-aka lone star tick
-female has white spot on sputum
-long mouth parts
-short basis capitulum

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What are the characteristics of Dermacentor variabilis?

-aka American dog tick
-ornate scutum
-all three palp segments appear stubby

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What are the characteristics of Amblyomma maculatum?

-aka gulf coast tick
-long mouth parts
-short basis capitulum
-ornate scutum

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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

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What are the characteristics of Rhipicephalus microplus?

-one host life cycle
-wider host range
-“southern cattle tick”
-small, stubby palps

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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

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Which species of Haemaphysalis are of importance?

-H. leporispalustris: rabbit tick
-H. chordeilis: bird tick
-H. longicornis: invasive tick with many hosts

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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

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How do tick-borne diseases differ between direct and indirect?

-direct: tick causes the disease itself
-indirect: tick transmits an infectious organism

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Which ticks are able to cause tick bites reactions?

all ticks, but esp. those with long mouthparts

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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