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Questions and Answers
Ticks are closely related to insects.
False
Ixodidae and Argasidae are two families of ticks that are of veterinary importance.
True
Ticks can cause anemia in animals.
True
Francisella tularensis is a protozoal disease transmitted by ticks.
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Ticks can transmit diseases like Hepatozoon canis and Babesia sp.
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The symptoms of a tick bite may include skin rash, but only immediately after the bite.
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Rickettsia rickettsii is a viral disease transmitted by ticks.
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Ticks can transmit diseases like Colorado tick fever and tick-borne encephalitis to humans.
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There are approximately 12 genera of hard ticks.
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The genus Boophilus is a separate genus from Rhipicephalus.
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The life cycle of an Ixodid tick always takes place on three different hosts.
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One-host ticks are more difficult to control than three-host ticks.
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A two-host tick has larvae and nymphs on one host and adults on another host.
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Dipping and chemotherapeutic agents can affect all life stages of a three-host tick.
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Cattle can be a host for a one-host tick.
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Managing a one-host tick is more difficult than managing a three-host tick.
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Ticks can transmit diseases to humans through transovarial transmission.
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Three-host ticks feed on the same host throughout their lives.
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Ixodid ticks found attached to domestic animals can be removed individually by cautious traction with thumb forceps.
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The long hypostomes of Dermacentor, Rhipicephalus, and Haemaphysalis are effective anchors.
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Rhipicephalus annulatus is a one-host tick that can transmit disease organisms via interstadial transmission.
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Babesia bigemina is transmitted from the adult female Rhipicephalus tick to her larvae through interstadial transmission.
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Two-host ticks can transmit disease organisms via transovarial transmission.
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Unless reasonable care is exercised, the mouthparts of the tick may be torn away and remain embedded as a foreign body in the host's skin.
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Ixodes species have eyes, festoons, and scutal ornamentation.
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Ixodes holocyclus is known to cause tick paralysis in North America.
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Amblyomma species have a groove posterior to the anus.
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Hyalomma species have a very short second segment of palps.
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Ixodes scapularis is a two-host tick.
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Ixodes species are the major vectors of bovine piroplasmosis in North America.
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The palpal segments two and three of Amblyomma are approximately the same length.
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Hyalomma species have adanal plates on males that are always large.
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Rhipicephalus annulatus is a two-host tick.
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Ixodes pacificus is known to transmit microtine piroplasmosis.
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Rhipicephalus pulchellus is found in the Horn of Africa and west of the Rift Valley.
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Rhipicephalus pulchellus is a two-host tick.
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Dermacentor nitens has 11 festoons.
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Haemaphysalis ticks resemble Rhipicephalus in having a hexagonal basis capituli.
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Larvae and nymphs of Haemaphysalis leporispalustris feed on small mammals and birds.
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Adults of Haemaphysalis leporispalustris attach to rabbits' ears and sometimes dogs.
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There are 150 species of soft ticks belonging to four genera.
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Argas species are typically found on bats.
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Argas ticks have leathery, smooth, and wrinkled dorsal and ventral surfaces.
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Argas ticks are commonly found on their host.
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Argas species transmit fowl or avian spirochetosis via tick bites.
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Ornithodoros ticks are more elongated than Argas ticks.
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Ornithodoros ticks are found in the same habitats as Argas ticks.
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Ornithodoros ticks are vectors of relapsing fever spirochetes in humans.
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Study Notes
Classification and Characteristics of Ticks
- Ticks belong to the class Arachnida and are closely related to mites
- They are obligate blood-feeding ectoparasites and vectors of disease
Types of Ticks
- Ixodidae: primarily live outdoors, mate on host, require days to complete engorgement
- Argasidae: live in close proximity to host, mate off host, require minutes to hours to feed and feed repeatedly
Tick-Borne Diseases
Viral Diseases
- Colorado tick fever: affects rodents, transmitted by Dermacentor ticks
- Tick-borne encephalitis: affects humans, cattle, horses, dogs
- African swine fever: affects wild suids, transmitted by Ornithodorus ticks
Rickettsial Diseases
- Rickettsia rickettsii
- Anaplasma sp.
- Ehrlichia sp.
Bacterial Diseases
- Borrelia sp.
- Mycoplasma haemocanis
- Francisella tularensis
Protozoal Diseases
- Hepatozoon canis
- Babesia sp.
- Cytauxzoon felis
Symptoms of Tick Bites
- Fever
- Chills
- Muscle pain
- Headaches
- Tiredness
- Itchiness or irritation (not immediate)
- Skin rash
Family Ixodidae: Hard Ticks
- Approximately 700 species of hard ticks are included within a total of 12 genera.
- Currently recognized genera are Amblyomma, Anomalohimalaya, Bothriocroton, Cosmiomma, Dermacentor, Haemaphysalis, Hyalomma, Ixodes, Margaropus, Nosomma, Rhipicentor, and Rhipicephalus.
Life Cycle of Ixodid Ticks
- One-host ticks: entire parasitic development from larvae to adult takes place on one host.
- Two-host ticks: larvae and nymphs occur on one host, adults on another.
- Three-host ticks: each stage of development takes place on different hosts.
- One-host ticks are often easier to control by managing the single host than three-host ticks.
- Three-host ticks may feed on several different hosts during their lives, making them perfect vectors for the transmission of zoonotic agents to humans.
Disease Transmission
- Two- and three-host ticks can transmit disease organisms via interstadial transmission.
- Infection acquired by a larval tick is carried through the molt to the nymphal stage and then is conveyed to the host on which the nymph feeds.
- Infection acquired by a nymph is carried through the molt and is conveyed to the host on which the adult tick feeds.
- Transovarial transmission: the disease organisms are passed from the adult female tick to her larvae through infection of her ovaries.
- Babesia bigemina is transmitted from the adult female Rhipicephalus (formerly Boophilus) tick to her progeny through her ovaries.
Representative Genera of Hard Ticks (Ixodidae)
- Ixodes: no eyes, festoons, or scutal ornamentation; broad palpi; anal groove forms an arch anterior to the anus.
- Hyalomma: resembles Amblyomma in having mouthparts much larger than the basis capituli; eyes and festoons are present; banded legs.
- Rhipicephalus: basis capituli is hexagonal; eyes and festoons are present; scutum is unornamented; males have salient adanal and accessory shields.
- Dermacentor: basis capituli is rectangular; coxae of male's progress in size from the first to the fourth; mostly three-host tick; scutum is ornamented; males lack adanal shields.
- Haemaphysalis: palpi have laterally flared second segments; no eyes nor scutal ornamentation; festoons and posterior anal groove are present.
Family Argasidae: Soft Ticks
- Soft ticks are small, consisting of 140 species belonging to four genera: Argas, Ornithodoros, Otobius, and Carios.
- Soft ticks are rarely found on the host; look in cracks and crevices for these ticks.
Argas Species
- Size 5- to 10-mm, flattened, ovoid, and yellow to reddish-brown ticks with leathery, mammillated, and wrinkled dorsal and ventral surfaces.
- Mouthparts are on the ventral surface and thus are hidden when the tick is viewed from above.
- Argas species transmit fowl or avian spirochetosis (Borrelia anserina) via tick fecal contamination to domestic poultry.
- Ticks may remain infective for 6 months or longer and may transmit the spirochetes to their offspring via the ovaries (transovarial transmission).
Ornithodoros
- Ornithodoros differs from Argas in being more globular, lacking a sharp lateral margin, and not appearing distinctly ovoid when viewed from above.
- The body is flattened in unfed specimens but is strongly convex dorsally when distended with blood.
- Ornithodoros are the most important vectors and reservoirs of relapsing fever spirochetes (Borrelia spp.) in humans.
- Infection may be maintained in tick populations for many years by transovarial transmission of the spirochetes from female ticks to their offspring.
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Description
This lecture covers the basics of ticks, their classification, and their importance in veterinary medicine. It also discusses the different types of ticks, including Ixodidae and Argasidae.
