Official Common Name: Ixodes rubicundus
Scientific name and classification
Species: Ixodes rubicundus Neumann, 1904;
Description/How to recognise a Karoo paralysis tick
The Karoo paralysis tick is a shiny, eyeless, reddish-brown tick, with legs attached to the far front end of the body (Brites-Neto et al. 2015). It has long mouthparts relative to its size.
Ticks are crawlers, however, their main form of dispersion over long distances is by passive transport through their hosts. Ixodid ticks attach to their hosts to feed and then detach when engorged (Carroll & Schmidtmann 1996). They penetrate the skin with their mouthparts and consume their host’s blood while being carried around (Fourie & Kok 1996).
Generally tick communication is done through sensing of chemical signals, which are classified into two types: the arrestment pheromone (arrestants) and sex pheromones (Sonenshine 2006). Fourie & Kok (1996) furthermore describes the Karoo paralysis tick communication as their reaction to vibrations, shadows and odours. The questing height of adults corresponds to the belly height of their preferred hosts, mountain reedbuck and sheep.
The Karoo paralysis tick is a South African tick. It occurs in the Karoo, southern Free State and small foci near the towns of Bronkhorstspruit and Heidelberg in Gauteng, and Belfast in Mpumalanga. Hilly or mountainous veld with Olea europaea subsp. cuspidata (wild olive tree), Searsia erosa (the besembos shrub) and Tenaxia disticha (the suurpol grass) all support the presence of the tick, as does the presence of eastern rock elephant shrews (eastern rock sengis) and red rock hares.
This tick can be found in hilly or mountainous areas, particularly in South Africa’s Karoo region. Therefore, this tick species’ adults are linked to the majority of ruminants that live in or travel through hilly or rocky terrain. The nymphs and larvae infest eastern rock elephant shrews and red rock hares, and the larvae, nymphs and adults are all linked to caracals (Horak et al. 2015; Ledwaba et al. 2022). Infestation with Ixodes rubicundus is also associated with rocky terrain, a habitat favoured by caracals (Horak et al. 2015; Ledwaba et al. 2022). The ticks prefer the cooler southern slopes of hills (Horak et al. 2015).
Adult Karoo paralysis ticks prey on mountain reedbuck (Redunca fulvorufula), dogs, sheep, goats and caracals (Caracal caracal). Immature ticks are found on eastern rock elephant shrews (Elephantulus myurus), Smith’s red rock hare (Pronolagus rupestris) and caracals. Female ticks infest the wool-line on the limbs and belly of sheep, whereas males rarely attach to hosts, but are frequently found attached to female ticks (Walker 1991; Horak et al. 2015).
Sex and life cycles
This tick has a three-host life cycle. Eggs are laid during summer and hatch the following autumn. Nymphs attach to hosts, engorging themselves over summer and then drop to moult to the adult stage in autumn. Adult female ticks remain on the host for about seven days, after which they detach to lay 2 000–4 000 eggs and then die. The life cycle takes two years to complete (Horak et al. 2015).
THE BIG PICTURE
Friends and foes
Due to the toxicoses they produce, several tick species that infest cattle and other livestock are economically significant to the southern African livestock industry. Ixodes rubicundus and other species, like Rhipicephalus evertsi evertsi and R. warburtoni, are known to cause paralysis in sheep and goats. Paralysis is induced by feeding female Ixodes rubicundus ticks when infestation densities on hosts exceed certain critical levels.
The sites of attachment of female Ixodes rubicundus ticks may differ according to the host species infested. On short-haired cattle, ticks attach to the brisket, belly and flank, while they attach to the forelegs and shoulders of cattle with longer hair (Fourie & Horak 1994).
Stampa & Du Toit (1958) report that adult female ticks attach to the woolled parts of sheep and the remainder to the hairy areas, while they attach to the hindlegs and buttocks of mountain reedbuck. Larvae attach anywhere on the body of elephant shrews except the tail and ears, while on red rock hares they attach to the inner surface of the limbs and the ventral surface of the abdomen (Stampa & Du Toit 1958).
Poorer world without me
Ticks, in general, are an important food source for several species of reptiles, amphibians and birds. Their extinction or disappearance might result in a decrease in numbers of these animals.
People and I
Animals with a single stomach are the preferred hosts for adult Karoo paralysis ticks. Since no southern African ixodid tick uses humans as its primary host, all tick bite incidents should be viewed as accidental or opportunistic. In cases of Karoo paralysis tick bite, the tick specifically cause paralysis of the limbs. In less severe cases the animal is still able to move, although it lacks strength and coordination. In more extreme situations, the paralysis also affects other muscle groups and impairs swallowing.
Rarely is breathing hampered in either animals or humans until the heart is harmed soon before death. Although ruminal motions are typically inhibited, the digestive tract’s peristalsis usually doesn’t seem to be impacted (Stampa & Du Toit 1958).
Conservation status and what the future holds
The Karoo paralysis tick is indigenous to South Africa and currently not listed on the IUCN Red List.
Ixodes is the largest genus in the family Ixodidae. The genus contains approximately 245 species and is highly specialised, both structurally and biologically. In southern Africa, ticks of this genus are probably the most poorly studied.
References and further reading
- Brites-Neto, J., Duarte, K.M.R. & Martins, T.F. 2015. Tick-borne infections in human and animal population worldwide. Veterinary world 8(3): 301.
- Carroll & Schmidtmann. 1996.
- Estrada-Peña, A.G.U.S.T.Í.N. & Mans, B.J. 2013. Tick-induced paralysis and toxicoses. In: D.E. Sonenshine & R.M. Roe, [publication]: 313–332. Oxford University Press, USA.
- Fourie, L.J. & Horak, I.G. 1994. The life cycle of Ixodes rubicundus (Acari: Ixodidae) and its adaptation to a hot, dry environment. Experimental & applied acarology 18(1): 23–35.
- Fourie, L.J. & Kok, D.J. 1996. Seasonal dynamics of the Karoo paralysis tick (Ixodes rubicundus): a comparative study on Merino and Dorper sheep. [publication details]
- Horak, I.G., Jordaan, A.J., Van Dalen, E.M. & Heyne, H. 2015. Distribution of endemic and introduced tick species in Free State Province, South Africa. Journal of the South African Veterinary Association 86(1): 1–9.
- Ledwaba, M.B., Nozipho, K., Tembe, D., Onyiche, T.E. & Chaisi, M.E. 2022. Distribution and prevalence of ticks and tick-borne pathogens of wild animals in South Africa: A systematic review. Current Research in Parasitology & Vector-borne Diseases [journal volume details]: 100088.
- Nicholson, W.L., Sonenshine, D.E., Noden, B.H. & Brown, R.N. 2019. Ticks (Ixodida). In: [author/editor details] Medical and veterinary entomology: 603–672). Academic Press, [place of publication].
- Spickett, A.M. & Heyne, H. 1988. A survey of Karoo tick paralysis in South Africa. [publication details]
- Sonenshine, D.E. 2006. Tick pheromones and their use in tick control. Annual Review of Entomology 51: [page numbers].
- Stampa, S. & Du Toit, R. 1958. Paralysis of stock due to the Karoo paralysis tick (Ixodes rubicundus. Neu.). South African Journal of Science 54(9): 241–246.
- Walker, J.B. 1991. A review of the ixodid ticks (Acari, Ixodidae) occurring in southern Africa. [publication details].
- https://www.afrivip.org/sites/default/files/Ticks-importance/ixodes/# (accessed 12 January 2023).
Author: Veronica K.T. Phetla