«Ticks: Tick identification Ticks Tick identification Authors: Prof Maxime Madder, Prof Ivan Horak, Dr Hein Stoltsz Licensed under a Creative Commons ...»
Ticks: Tick identification
Authors: Prof Maxime Madder, Prof Ivan Horak, Dr Hein Stoltsz
Licensed under a Creative Commons Attribution license.
TICKS OF VETERINARY IMPORTANCE / DIFFERENTIAL
Photos, distribution maps, importance and hosts of all ticks described below and of other ticks of veterinary
and human importance can be found online at:
http://www.itg.be/photodatabase/African_ticks_files/index.html or offline in the Tick database.
A holistic approach should be followed in the identification of ticks. Thus besides the morphological features that we make use of to identify ticks to species level, we also make use of their ecological requirements to assist with an accurate diagnosis. Consequently the geographic locality at which they were collected, the hosts from which they were collected, the body site on the host from which they were collected, and the season of the year during which they were collected are all important aids. Ideally anyone who sends in ticks for identification should supply all this information. Perhaps most important of all is that male ticks must be included in any collection sent for identification as they have more distinct taxonomic features that can be recognized than the females. Even more importantly a label containing all the important collection data and written in pencil should be included with the ticks inside the vial or tube or bottle in which the ticks have been placed. If an outside label is pasted onto the container it must be written in pencil, ball point writing dissolves the moment the alcohol used for tick preservation spills onto it.
Besides the ticks whose common names are derived from their colour, farmers and researchers have also named ticks according to the geographic locality in which they are present, or the season during which they occur, or the condition they may cause, or the host on which they may feed or where they attach. Thus we have the Karoo paralysis tick, the winter horse tick, the kennel tick, the brown ear tick, the fowl tampan and the sand tampan. As you can gather from the foregoing these names are very descriptive and immediately give you a clue as to which tick you are dealing with.
The Ixodidae Amblyomma spp.
Amblyomma hebraeum – the South African bont tick Amblyomma hebraeum is a medium-sized to large tick with long mouth-parts and banded legs, its eyes are flat, the conscutum of the male is ornate with two discrete lateral patches of colour, and with the exception of the first festoon on either side the festoons are uniformly yellow in colour. It closely resembles A. gemma, an East African tick, but has the two discrete lateral patches of colour 1|Page Ticks: Tick identification on the conscutum which are joined to the main colour pattern in A. gemma, and the festoons of A.
gemma are variably dark-brown and yellow. Its distribution does not overlap with that of A. gemma (see Tick database for pictures and more information).
2|Page Ticks: Tick identification Adults feed on cattle, sheep, goats and large wild ruminants, particularly giraffes (Giraffa camelopardalis), African buffalo (Syncerus caffer) and eland (Taurotragus oryx), also on warthogs (Phacochoerus africanus) and black (Diceros bicornis) and white (Ceratotherium simum) rhinoceroses. Immatures infest the same hosts as the adults but also small antelopes, scrub hares (Lepus saxatilis), helmeted guineafowls (Numida meleagris), and tortoises (e.g. Chersina angulata, Geochelone pardalis). The immature stages of this tick do not infest rodents (rats, mice, squirrels or gerbils), if they do they seem unable to engorge and usually die. The adults prefer the hairless areas under the tail, in the lower perineal region, on the udder and testes, around the prepuce and in the axilla of cattle, as well as around the feet of sheep and goats. The larvae are found on the feet, legs and on the muzzle, the nymphs attach on the feet, legs, groin, sternum and neck.
Amblyomma hebraeum is a three-host tick, like all other species of this genus. The adults and nymphs are “hunters”, scuttling along the ground when a suitable host is in the vicinity. After detaching the engorged female will lay up to 20 000 eggs. These eggs hatch after two to three weeks depending on the temperature and the larvae wait for hosts on the vegetation, from which very large numbers can be collected by drag-sampling the vegetation with flannel cloths. Once attached the larvae engorge in 7 to 14 days, detach and moult. The nymphs engorge in 7 to 14 days, detach and moult. The adult males attach and start engorging. Only when sexually mature males (i.e. males that have been attached for ± 6 days) are present will the females attach. The pheromones secreted by the mature male ticks also attract more male and female ticks as well as nymphs which all attach to the host, usually in the vicinity of the mature males. The males and females mate and the females engorge in 7 to 9 days and detach. The males may remain on the host animal for 2 to 4 months. The life cycle usually takes 1 year to complete, but may extend for longer.
This tick requires moisture and warmth, brush and bush and does not survive in open grassland. In South Africa it is found along the coastal belt from Port Elizabeth in the Eastern Cape Province, through KwaZulu-Natal and thence across Mpumalanga, Gauteng, Limpopo and North-West Provinces, north of a line running approximately through Pretoria to the Botswana border. It is also present in eastern Swaziland, southern Mozambique, eastern Botswana and in southern and eastern Zimbabwe.
Amblyomma hebraeum transmits Ehrlichia ruminantium (heartwater) to domestic and wild ruminants, and Theileria mutans (benign bovine theilerioses) to cattle and Rickettsia africana, the cause of African tick-bite fever in humans. The larvae of A. hebraeum are probably more responsible than any other tick for tick bites in humans.
Amblyomma variegatum – the tropical bont tick Adults of A. variegatum have long mouthparts and banded legs like A. hebraeum, but have different colour patterns on the conscutum and scutum, the colour pattern on the male conscutum is darkorange. Their eyes are beady, and the males have uniformly dark festoons.
It is widely distributed through West, Central, North-East and East Africa and in southern Africa extends into Zambia, north-eastern Botswana, the Caprivi Strip of Namibia, north-western Zimbabwe 3|Page Ticks: Tick identification and central and northern Mozambique. Its spread southwards appears to be limited by interspecific competition with A. hebraeum with which it shares similar habitats, hosts and sites of attachment and by the drier conditions in the south. It has also been imported onto the Caribbean islands where attempts to eradicate it have cost millions of dollars without success, mainly because of the variety of hosts it infests, particularly the immature stages, and its re-introduction by birds infested with the immature stages flying from one island to the next.
Amblyomma variegatum transmits heartwater (E. ruminantium), benign bovine theilerioses (Theileria mutans, T. velifera), bovine ehrlichiosis (E. bovis), the virus of Nairobi sheep disease and is associated with acute bovine dermatophilosis (Dermatophilus congolensis).
Hyalomma dromedarii – the camel tick Adult H. dromedarii are large yellow-brown to nearly black ticks with long mouthparts. The legs are paler than the scutum and may be ringed by paler bands. The lateral grooves are short and deep and limited to the posterior third of the conscutum, the postero-median groove is deep and narrow, extending from a distinct parma to midlength of the conscutum. This groove is bounded on either side by converging ridges and lateral to these ridges are the deep and wide postero-lateral grooves.
The sub-anal plates on the male are distinctly laterally placed in relation to the adanal plates and may extend beyond the posterior margin of the body in engorged specimens. The genital aperture of the female is narrowly elongate and triangular.
The preferred hosts are camels (Camelus dromedarius), but cattle, sheep, goats and horses may also be infested. The larvae and the nymphs feed on small burrowing animals and on hares, but the nymphs may also infest camels, cattle and horses. Adults attach on the inner thighs, udder and scrotum and in the outer nostrils of camels.
Hyalomma dromedarii has a two or a three-host life cycle. The larvae may feed and moult to nymphs on small mammals or hares and the adults feed on large domestic herbivores. Alternatively the larvae may feed on small mammal hosts, drop off and moult to nymphs, which can then either attach to other small mammal hosts or feed on the same large animals as the adults. The life cycle appears to be continuous throughout the year.
It is present in the arid regions of north Africa from Mauritania in the west to Egypt in the east; it is also present in Sudan, Ethiopia, Somalia and Kenya in North East Africa. It was introduced into Namibia on camels and continues to exist there on these animals in arid regions.
It transmits Theileria annulata the cause of tropical theileriosis, is also a mechanical vector of camel pox and has been incriminated in a case of tick paralysis in children in Egypt.
4|Page Ticks: Tick identification 5|Page Ticks: Tick identification Hyalomma rufipes – large, coarse bont-legged tick Until recently this tick was known as Hyalomma marginatum rufipes, a subspecies of Hyalomma marginatum, but it has now been established as a valid species and given full specific status as Hyalomma rufipes.
Dark-brown to nearly black conscutum of male is is broadly oval and the entire surface is covered with medium-sized, coarse punctations. The brown legs are brightly-banded with ivory-coloured rings. The adanal plates have square ends, and the sub-anal plates are distinct but small and aligned with the adanal plates. The genital apron of the female is convex, the genital aperture is very broadly v-shaped, and there are numerous setae in the circumspiracular area.
With the exception of Lesotho, the eastern Free State, the coastal areas of KwaZulu-Natal and the coastal areas and adjoining inland regions of the Western Cape Province, H. rufipes is present throughout South Africa. It is widespread in Botswana, Zimbabwe and northern Namibia as well as in Kenya, Ethiopia and Somalia and the southern countries of West Africa.
Hyalomma rufipes adults feed on cattle, sheep, goats, horses, and large wild herbivores including rhinoceroses. The immature stages feed on scrub hares and ground-frequenting birds (e.g.
guineafowl). Adults attach in the hairless area of cattle around the anus and on the genitalia and are also found around the hooves of sheep. The immature stages are found on the necks of scrub hares and on the heads and necks of birds.
Hyalomma rufipes is a two-host tick. The adults are “hunters”. The females feed for 7 to 14 days and then detach and lay 2 000 to 10 000 eggs and die. The larvae hatch in 30 to 60 days and infest hares or birds on which they engorge and moult to nymphs. The engorged nymphs detach, drop to the ground and moult to adults. The life cycle takes 1 year to complete. The adults are active mainly during the summer months from October to March. The immature stages feed on hares and birds from autumn to spring.
The long mouthparts cause tissue damage in cattle and sheep and secondary bacterial infections may lead to abscess formation. The tick also causes lameness in lambs. Injuries caused by the long mouthparts are attractive to the blowfly Chrysomya bezziana. It can transmit Anaplasma marginale to cattle causing bovine anaplasmosis or gallsickness and also Babesia occultans causing benign babesiosis in cattle; it can also transmit R. conori to humans. Ticks of the genus Hyalomma can transmit Congo Haemorrhagic fever virus to humans: H. rufipes would appear to be the most efficient vector of the virus.
Hyalomma glabrum – pale-legged bont-legged tick
Until recently this tick was classified as a subspecies of Hyalomma marginatum and was known as H. marginatum turanicum. It has subsequently been reinstated as an old taxon bearing the specific name Hyalomma glabrum. It is fairly similar in appearance to H. rufipes, but the dorsal aspects of its banded legs are ivory-coloured. Its hosts are the same as those of H. rufipes.
6|Page Ticks: Tick identification Hyalomma truncatum – small smooth bont-legged tick Dark-brown conscutum of male is fairly narrow, glossy with few punctations anteriorly, with a semicircular indentation posteriorly that is covered with coarse punctations. The brown legs are brightlybanded with ivory-coloured rings. The adanal plates have square ends, and the sub-anal plates are distinct but small and aligned with the adanal plates. The genital apron of the female is concave, the genital aperture nearly semicircular in shape, and the circumspiracular area is nude.
With the exception of Lesotho, the eastern Cape Province, the eastern half of the Free State, southeastern Gauteng and south-eastern Mpumalanga and southern KwaZulu-Natal, H. truncatum is present throughout South Africa. It is present throughout Zimbabwe and much of Mozambique. It occurs in south-eastern and north-western Botswana, central and northern Namibia, and southern Angola. In Tanzania and in Kenya it is present mainly in the south-west, and with the exception of the eastern and western regions it occurs throughout Ethiopia and from there to the West African coast.
Hyalomma truncatum adults feed on cattle, sheep, goats, horses, large wild herbivores and particularly on giraffes and eland and occasionally on dogs. The immature stages feed on scrub hares and on various species of small rodents (e.g.bushveld gerbils (Gerbilliscus leucogaster), and four-striped mice (Rhabdomys pumilio)). On cattle the adults of H. truncatum attach in the tail switch, around the anus, on the lower perineum and on the legs. They are also found around the hooves of sheep. The immature stages attach on the necks of scrub hares. Hyalomma truncatum is a two-host tick. The adults are “hunters”. The females feed for 7 to 14 days and then detach and lay 2 000 to 10 000 eggs and die. The larvae hatch in 30 to 60 days and infest hares or rodents, on which they engorge and moult to nymphs. The engorged nymphs detach, drop to the ground and moult to adults. The life cycle takes 1 year to complete.