Lecture 9 & 10: Ticks (516 ZOO) PDF

TICKS “516 ZOO” Lecture 9 &10 Dr. Osama B Mohammed & Dr. Jawahir ALGhamdi 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...

TICKS “516 ZOO” Lecture 9 &10 Dr. Osama B Mohammed & Dr. Jawahir ALGhamdi 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, with the genus Boophilus becoming a subgenus of the genus Rhipicephalus. Dorsal view of a generalized female, ixodid tick.  1. The egg, 2. Sixlegged larva 3. Eight-legged Nymph 4. Eight-legged Adult. Six-legged The life cycle of an Ixodid tick. The life cycle of an Ixodid tick. One-host ticks Where the entire parasitic development from larvae to adult takes place on one host. Two-host ticks where larvae and nymphs occur on one host adults on another. Three-host ticks where each stage of development takes place on different hosts.  What is important relative to these terms is that a one-host tick or a three-host tick?  A tick that feeds on only one host is often easier to control by managing the single host than a three-host tick with different hosts throughout the environment. For example, if cattle are hosts to a one-host tick, dipping and other applications of chemotherapeutic agents or cattle vaccination will affect all tick life stages. If three hosts were involved, the first host might be a rodent, the second a rabbit or a bird, and the third cattle. Thus, it would be more difficult to manage these two- or three-host systems because it would be difficult to manage or treat all three hosts involved. That three-host ticks may feed on several different hosts during their lives, from small rodents to large mammals, makes them perfect vectors for the transmission of zoonotic agents to humans (e.g., the larva feeds on a rodent, the nymph or adult will feed on humans); thus, transmission from rodents to humans becomes a real possibility. This is exactly what occurs in the case of Lyme borreliosis. Two- and three-host ticks can transmit disease organisms via interstadial transmission; that is, 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, or infection acquired by a nymph is carried through the molt and is conveyed to the host on which the adult tick feeds. In 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. Transovarial transmission of disease organisms is the only mechanism that allows one-host ticks, such as Rhipicephalus annulatus, to serve as vectors Babesia bigemina Pear-shaped Rhipicephalus annulatus inside a red blood cell (arrow). ▪ Ixodid ticks found attached to domestic animals may be removed individually by cautious traction with thumb forceps. ▪ The long hypostomes of Ixodes, Amblyomma, and Hyalomma are effective anchors. ▪ Dermacentor, Rhipicephalus, and Haemaphysalis compensate for their shorter hypostomes by secreting cement in which the mouthparts are embedded, which attaches them securely to the skin. ▪ Unless reasonable care is exercised, the capitulum may be torn away and remain embedded as a foreign body in the host's skin.  Ixodes Hyalomma Rhipicephalus Representative genera of hard ticks (Ixodidae) Dermacentor Haemaphysalis Amblyomma Ixodes ▪ The anal groove forms an arch anterior to the anus; this can be seen with oblique illumination of uncleared specimens. Other genera have a groove posterior to the anus or no groove at all. ▪ Ixodes species have no eyes, festoons, or scutal ornamentation; their palpi are broadest at the junction of segments two and three. Disease transmission Ixodes holocyclus of Australia is the most virulent tick paralysis producer known. Ixodes pacificus is known to cause tick paralysis in North America. Species of Ixodes are the major vectors of Lyme disease in North America and in Europe. Nymphs and adults of Ixodes scapularis in the eastern and north-central United States, a three-host tick that normally feeds on mice and voles as larvae and nymphs and on deer as adults, transmit microtine piroplasmosis (Babesia microti), Lyme disease (Borrelia burgdorferi), and human granulocytic anaplasmosis (Anaplasma phagocytophilum) to dogs, humans, and other animals. I n Europe, species of Ixodes are vectors of bovine piroplasmosis, louping ill (ovine encephalomyelitis), and human tick-borne encephalitis virus. Amblyomma Mouthparts are a very long, elongate second segment of palps Conscutum and scutum ornate Eyes present Festoons present Adanal plates on males absent, or when present, very small Banded legs Three-host ticks Hyalomma ▪ Hyalomma resembles Amblyomma in having mouthparts much larger than the basis capituli but differs in that the second and third palpal segments are approximately the same length. ▪ Eyes are present. ▪ Festoons are irregularly ▪ The male has adanal and accessory shields. Inordinate. Coalesced ▪ Banded legs ▪ Capitulum of Hyalomma. Palpal segments two and three of Hyalomma are approximately the same length, whereas the second palpal segment of Amblyomma is about twice as long as the third. Rhipicephalus ▪ The basis capituli is hexagonal. ▪ eyes and festoons are present, but the scutum is unornamented. ▪ males have salient adanal and accessory shields. ▪ Rhipicephalus microplus, also a piroplasmosis vector, has a broader host range that includes horses, goats, sheep, and deer. ▪ Rhipicephalus annulatus have one-host (cattle) nature and it is a vector for bovine piroplasmosis. ▪ Rhipicephalus pulchellus – the zebra tick ▪ It is present in the Horn of Africa and east of the Rift Valley from Eritrea in the north to north-eastern Tanzania in the south. ▪ It is a three-host tick. ▪ The adults appear to be most abundant during the rainy season. Three host tick. ▪ Vector for Nairobi sheep disease virus. Dermacentor ▪ The basis capituli is rectangular, as viewed from above. ▪ Coxae of male's progress in size from the first to the fourth. ▪ Mostly Three-host tick. ▪ Dermacentor resembles Rhipicephalus in having eyes and 11 festoons. ▪ The scutum is ornamented, and the males lack adanal shields. ▪ Dermacentor nitens, the tropical horse tick, has no ornamentation on its scutum and only seven festoons. Haemaphysalis ▪ The palpi have laterally flared second segments. ▪ Avoid confusing these structures with the hexagonal basis capituli of Rhipicephalus. ▪ Like Ixodes, these ticks have neither eyes nor scutal ornamentation, but they differ in having festoons and a posterior anal groove. Larvae and nymphs of Haemaphysalis leporispalustris, the rabbit tick, feed on ground-nesting birds and small mammals, and the adults attach to rabbits' ears and sometimes from cats. Family: Argasidae Soft ticks Soft ticks are small, consisting of 140 species belonging to four genera: Argas Ornithodoros Otobius Cariosare limited to bats. An argasid tick, Argas vespertilonis. (a) Dorsal view of female. (b) Ventral view of female (reproduced from Arthur, 1963). Argas species Size 5- to 10-mm, flattened, ovoid, and yellow to reddish-brown ticks with leathery, mammillated, and wrinkled dorsal and ventral surfaces meeting at a sharp lateral margin. The mouthparts are on the ventral surface and thus are hidden when the tick is viewed from above. Argas is rarely found on the host; look in cracks and crevices in the hen house for these ticks. ▪ DISEASE TRANSMISSION ▪ In South America, Argas species transmit fowl or avian spirochetosis (Borrelia anserina), via tick fecal contamination to domestic poultry, grouse, canaries etc... ▪ Ticks may remain infective for 6 months or longer and may transmit the spirochetes Spirochetes are long and slender bacteria, to their offspring via the ovaries (transovarial transmission). ▪ TICK PARALYSIS. Infestation with larvae of Argas persicus can result in fatal flaccid paralysis of young chickens. Ornithodoros Ornithodoros differs from Argas in: ▪ Being more globular. ▪ Lacking a sharp lateral margin. ▪ Not appearing distinctly ovoid when viewed from above. ▪ The body is flattened in unfed specimens but is strongly convex dorsally when distended with blood. ▪ They are found in cracks and crannies of avian roosts and nests, in rodent burrows, and in the resting places of large mammals. DISEASE TRANSMISSION ▪ 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. ▪ Because the Ornithodoros ticks involved in transmission are nocturnal and surreptitious, relapsing fever victims are frequently unaware of recent tick exposure. Otobius IDENTIFICATION ▪ Larvae and two nymphal stages of Otobius megnini, the spinose ear tick, parasitize the ear canals of cattle, remaining in a particular host for as long as 4 months. ▪ Other domestic animals and humans also sometimes serve as hosts. ▪ As implied by the common name, the cuticle of Otobius is covered by spines. ▪ The second nymphal stage is particularly distinctive. LIFE HISTORY Larvae feed in the ear canal and molt into the first nymphal stage, which in turn feeds in the same host’s ear canal and molts into the second nymphal stage, which again feeds but leaves the ear canal and drops to the ground to molt to the adult stage. Adult Otobius have vestigial hypostomes and do not feed; they copulate within a day or two after emergence, and the females oviposit in the soil. Larvae survive unfed for as long as 2 months. Thus, Otobius differs from Argas and Ornithodorus in being a one host tick and laying only one egg clutch. Family Nuttalliellidae A third family of ticks, the Nuttalliellidae, represented by a single species in the genus, Nuttalliella namaqua, are of real importance only to acarologists. Besides having markedly different morphology, soft and hard ticks vary greatly in their behavior. Thanks....