The Ixodidae
Hyalomma spp.
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.
 Hyalomma dromedarii and rufipes |
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.
Hyalomma truncatum – small smooth bont-legged tick
Dark-brown conscutum of male is fairly narrow, glossy with few punctations anteriorly, with a semi-circular indentation posteriorly that is covered with 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 concave, the genital aperture nearly semicircular in shape, and the circumspiracular area is nude.
 Hyalomma truncatum |
With the exception of Lesotho, the eastern Cape Province, the eastern half of the Free State, south-eastern 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.
The adults are active mainly during the summer months from October to March. The immature stages are active and feed on hares and rodents from autumn to spring.
Certain strains of H. truncatum contain a toxin in their saliva that causes sweating sickness, an acute dermatitis in cattle, particularly calves. When the ticks infest dogs they tend to cluster at one site and can cause severe skin necrosis. 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. Ticks of the genus Hyalomma can transmit Congo Haemorrhagic fever virus to humans, and H. truncatum can transmit R. conori to humans.
Hyalomma albiparmatum
All stages of this East African tick are identical in appearance to H. truncatum with the exception of an ivory-coloured central festoon in the male of H. albiparmatum.
