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The Ixodidae

Ixodes pilosus (group) -  Sourveld tick

There are probably three different tick species within this grouping of which only one has been described. The female is similar in appearance to Ixodes rubicundus, but the auriculae protrude laterally on the ventral aspect of the basis capituli, and there are spurs medio-posteriorly on the first pair of coxae. The alloscutum bears four longitudinal rows of long, stout setae dorsally. The posterior alignment of the anal groove is short and converging. In the male the genital aperture is present in an inverted U-shaped area formed by the ventral shields.

All stages of development of I. pilosus infest cattle, sheep, dogs, grey rhebok (Palea capreolus), bushbuck (Tragelaphus scriptus), caracal (Caracal caracal) and scrub hares. It attaches around the the head.

This tick is present in the southeastern sourveld coastal regions of the Western and Eastern Cape Provinces, and there are foci around Nelspruit and in the Northern Province near Polokwane. It is a three-host tick, with adults present in summer, larvae in autumn and nymphs in spring.  This species is not known to transmit diseases.



Ixodes pilosus and rubicundus

Ixodes rubicundus - Karoo paralysis tick

Ixodes rubicundus is a reddish-brown colour and the mouthparts are long relative to the size of the tick. The palps are club-shaped and denticles are visible on the lateral aspects of the hypostome. Eyes are absent. The legs are long and slender and appear to be grouped anteriorly. A prominent lateral groove is evident on the conscutum of the male and festoons are absent. The anal groove surrounds the anus anteriorly in both sexes. The ventral surface of the male is covered with a number of shields and its genital aperture is present in an inverted V-shaped area formed by these shields. There are no adanal plates.  The auriculae of the female do not protrude prominently laterally on the ventral aspect of the basis capituli, and the medio-posterior aspect of the first pair of coxae is rounded and has no spur.

Adults feed on sheep, goats, dogs, caracals (Caracal caracal), and mountain reedbuck (Redunca fulvorufula). Immatures are found on rock elephant shrews (Elephantulus myurus), red rock rabbits (Pronolagus rupestris) and caracals. Females are present in the wool-line on the limbs and belly of sheep. Males rarely attach to host animals, but are frequently found attached to females. Ixodes rubicundus is a strictly  South African tick. It is present in the Karoo, southern Free State and small foci near the towns of Bronkhorstspruit, Belfast and Heidelberg in Gauteng and Mpumalanga Provinces. The presence of hilly or mountainous veld and of the wild olive tree (Olea africana), the shrub “besembos” (Rhus erosa), and the gras “suurpol” (Merxmeullera disticha) all support the existence of the tick as does the presence of rock elephant shrews (eastern rock sengis) and red rock rabbits. The ticks also prefer the southern slopes of the hills that are cooler than the northern slopes.

This is a three-host tick. The females remain on the host for about 7 days, they then detach and lay 2 000 to 4 000 eggs and die. The eggs "over-summer" and only hatch the following autumn. The larvae feed on red rock rabbits and rock elephant shrews during autumn and winter and the nymphs during winter and spring. The engorged nymphs, which drop from these small mammals, "over-summer" and moult to the adult stage the following autumn. The females remain on the host for about 7 days. The life cycle takes 2 years to complete. Suurpol, besembos and wild olives afford protection for the hares and shrews and the mat of leaves that forms under this vegetation supplies shelter to the ticks and their eggs. This mat also ensures that the relative humidity is high, which is essential for the hatching of the eggs. Adult ticks quest on the grass at a height of about 40 cm within 2 metres of “besembos” or “wild olives”. They react to vibrations, shadows and odours. The questing height of the adults corresponds to the belly height of their preferred hosts, mountain reedbuck and sheep.

Adults are most abundant on sheep and on antelopes during autumn to spring of one year, during the following year larvae are most abundant on rock elephant shrews and on red rock rabbits during late summer to winter and nymphs during winter to spring. Adult ticks appear on the vegetation and on host animals earlier in the year in the south of South Africa than in the north.

The female ticks produce a toxin that causes paralysis, particularly in sheep and goats, but young calves and antelopes may also be affected. Peak numbers of adult ticks are present within 4 weeks of activity having commenced, and the number of female ticks per kg of host mass is important in the causation of paralysis. Initially a paralysis of the legs is noted and this may progress until paralysis of the respiratory system and death supervenes. A few cases of paralysis may be seen in February or March, reaching a peak in April or May, and are associated with a drop in environmental temperature and with moist conditions. If the ticks are removed timeously the clinical signs are reversed within a few hours.

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