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The Argasidae

Subfamily: Ornithodorinae

Otobius megnini - spinose ear tick

Adult ticks are dark-grey in colour and violin-shaped. Numerous small pits are present on the integument. The lateral margin of the body is thick without a definite suture line. The mouthparts are rudimentary and the capitulum is situated on the antero-ventral surface of the body. The adults do not feed. The tick is eyeless.

The larvae have six fairly long legs and the capitulum is situated anteriorly. As the larvae engorge they become pear-shaped. They are white or pink in colour. There are a number of nymph stages. The earlier ones are diamond-shaped and the later ones assume a violin-shape, similar to that of the adults. The capitulum is situated antero-ventrally under the body. The nymphs are covered with short, rigid spines from which the tick derives its common name.

Otobius megnini infests cattle, sheep, goats, horses, donkeys, mules and cats and occasionally humans.
This tick was introduced from South America in about 1898 after the rinderpest. It is found in the drier areas of the country such as the Karoo, Kalahari and Free State but is still spreading and has been found in the Pretoria district.
The female tick lays 300 to 1500 eggs in batches over a period of months. These eggs are laid in cracks and crevices in kraals, stables and catteries. The eggs hatch in about three weeks giving rise to a six-legged larva, which, after locating a host, attaches in the ear canal. The larval stage lasts 1 to 2 weeks and the larva then moults in the ear and gives rise to the first nymph stage, which is eight-legged and also attaches in the ear. The number of nymph stages is unknown but moulting and attachment of each stage occurs in the ear. The nymphs remain in the ear for 3 to 6 months and the final nymph stage engorges, detaches and drops out in the kraal. These nymphs moult and the resulting adults mate; 18 months may pass before mating takes place. The adults are non-parasitic and remain in cracks and crevices in the kraal. The life cycle may extend for a period of 2 years.

Otobius megnini is essentially a kraal infestation and the ticks are carried to new localities in the ears of infested animals. The ticks feeding in the ear canal and the spines on their bodies result in considerable irritation and infested animals do not feed well.

Ornithodoros moubata/porcinus - eyeless or hut tampan, warthog tampan

The adults are grey-brown in colour with a leathery mammilated integument, the margins of the body are rounded and a supracoxal fold is present. They are similar in appearance to Ornithodoros savignyi but have no eyes.
Hosts are humans, poultry, domestic pigs and warthogs.

The distribution of ticks of the O. moubata complex that parasitize warthog follows that of their warthog hosts, which still occur in large areas of southern Africa. However, as the density of human habitation increases, these areas are decreasing in size and in number and wildlife reserves are becoming the foci of warthog distribution. Locally the ticks are spread via their nymphal stages, which are commonly found on warthog foraging outside their burrows. These tampans are widespread in the more arid western and northern regions of North West, Limpopo and Mpumalanga Provinces, South Africa. They are also present in Botswana, Namibia, Zimbabwe, Tanzania, Kenya, Uganda, Ethiopia, Somalia and Sudan, and in Central and few records are from West Africa.

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Otobius megnini and Ortnithodoros moubata/porcinus

After a blood meal and mating the female produces a batch of approximately 300 eggs, which are well hidden. Six-legged larvae hatch from these eggs, but do not feed and then moult to the first nymph stage after 1 to 2 days. The nymphs seek a host and take a blood meal and then moult to the next nymph stage. This process is repeated for each of the four or five nymph stages. Each of these nymph stages may survive for as long as 2 years without a blood meal. The adults seek a host and take a blood meal that may take 20 to 30 minutes. While they are feeding they void large volumes of coxal fluid through the coxal openings between coxae I and II. Feeding in all stages usually takes place at night. After each blood meal the females lay a batch of eggs. The adults can survive for 4 to 5 years without food. All stages of the hut tampan hide in cracks and crevices in the hut walls during the day. Those of the warthog tampan hide in crevices in the warthog's burrow during the day. Large numbers of nymphs may be present on free-ranging warthogs out of their burrows during the day and infestation is probably spread in this way.

The warthog species, O. porcinus plays a role in the transmission of the virus causing African swine fever. Transovarial and trans-stadial transmission of the virus occur and it may also pass from male to female ticks during mating via the spermatophore. Adult warthogs serve as carriers of African swine fever virus but the viraemia in these animals is usually very low and transmission of the virus from warthogs to domestic pigs is effected by O. porcinus. Infection of warthogs usually occurs in the first 4 – 6 weeks of life via infected ticks in the burrows. Ormithodoros moubata transmits Borrelia duttoni, the causative organism of African relapsing fever in humans. This infection is transmitted to humans by means of the coxal fluid that is produced while the tampan is feeding and thus contaminates the feeding wound. Furthermore the O. moubata complex of ticks transmits Borrelia anserina the causative organism of fowl spirochaetosis and Aegyptianella pullorum to chickens.

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