Ticks infesting animals in the Sudan and southern Sudan : Past and current status

How to cite this article: ElGhali, A. & Hassan, S.M., 2012, ‘Ticks infesting animals in the Sudan and southern Sudan: Past and current status’, Onderstepoort Journal of Veterinary Research 79(1), Art. #431, 6 pages. http://dx.doi. org/10.4102/ojvr.v79i1.431 In this review, we collate information about ticks identified in different parts of the Sudan and South Sudan since 1956 in order to identify gaps in tick prevalence and create a map of tick distribution. This will avail basic data for further research on ticks and policies for the control of tick-borne diseases. In this review, we discuss the situation in the Republic of South Sudan as well as Sudan. For this purpose we have divided Sudan into four regions, namely northern Sudan (Northern and River Nile states), central Sudan (Khartoum, Gazera, White Nile, Blue Nile and Sennar states), western Sudan (North and South Kordofan and North, South and West Darfour states) and eastern Sudan (Red Sea, Kassala and Gadarif states).


Introduction
Ticks may have both direct and indirect adverse effects on their host animals.They feed on blood, leading to anaemia, and the injuries caused by their attachment damage hides and predispose animals to secondary bacterial infections that may lead to mastitis.These wounds may also be attractive to the myiasis-causing flies.Ticks can cause paralysis and probably transmit a greater variety of organisms that cause diseases than any other arthropod (Hoogstraal 1956).The economically most important tick-borne diseases are theileriosis, babesiosis, ehrlichiosis (heartwater) and anaplasmosis.The study of ticks that parasitise domestic animals is of considerable importance in that it assists in determining their host preference, their seasonality and geographic distribution, the diseases they may transmit and their control (King, Getting & Newson 1988).On-host ticks may be affected by factors such as species, breed and immune status, whilst free-living ticks are affected by climate, geographic region and seasonality.During the late 1940s and early 1950s Hoogstraal (1954Hoogstraal ( , 1956) ) collected ticks from more than 50 localities in Southern Sudan and 15 localities in Northern Sudan.He recorded 38 tick species in the southern Sudan provinces, seven in other provinces and 18 that were found in both Southern Sudan and other provinces.
In this review, we collate the findings on ticks identified in various regions of the Sudan and in South Sudan since Hoogstraal's survey (1956).The information should assist in filling some of the gaps in our knowledge about the ticks of the Sudan and South Sudan in order to compile a map illustrating tick distribution in both countries.The data could also provide a basis for further research on ticks and tick-borne diseases, which would be useful for developing control policies.

Northern Sudan
Central Sudan Hoogstraal (1956) recorded A. exornatum, Amblyomma lepidum, Amblyomma variegatum and R. (B.) decoloratus across central Sudan, except in Khartoum. Hy. scupense, Hy. dromedarii, Hy. excavatum, Hy. impeltatum, Hy. impressum, Hy. marginatum and Hy. rufipes were also recorded in central Sudan, except in the Blue Nile region (Hoogstraal 1956).Other species recorded in all states by Hoogstraal (1956) included R. evertsi evertsi, R. praetextatus and R. sanguineus.Just more than 25 years later the dominant tick species north and south of Wad Medani was Hy. anatolicum and a R. (Boophilus) species, respectively (FAO 1983).Tatchell (1983) stated that Hy. rufipes, R. evertsi evertsi and R. (B.) decoloratus were ubiquitous in their distribution along the Blue Nile, whilst the distribution of Hy. anatolicum was restricted to north of Wad Medani.He further reported that A. lepidum was common only south of a line between Wad Medani and Khartoum, whilst Rhipicephalus (Boophilus) annulatus was restricted to the area south of Wad Medani.Ticks of the Blue Nile and White Nile ecosystems were studied by Jongejan et al. (1987), who found 24 tick species infesting livestock and wildlife in these areas.Amongst these tick species Rhipicephalus (Boophilus) geigyi, Rhipicephalus bergeoni and Rhipicephalus camicasi were recorded for the first time in the Sudan.They also reported that R. (B.) annulatus had extended its distribution further north into the Blue Nile, Gezira and Khartoum regions.During 1979 to 1982, the immature stages of A. lepidum, Hy. anatolicum and R. evertsi evertsi were found feeding on cattle and sheep and immature A. variegatum specimens were collected from cattle (Latif 1985).Latif (1985) also found Hy. impeltatum nymphs on camels and sheep and Hy.dromedarii nymphs on camels for the first time.

Discussion
In the Sudan and South Sudan there are different geographic and climatic situations, ranging from the desert zone in the north (with an annual rainfall of less than 100 mm) to wooded savannahs in the south (with annual rainfall of more than 1000 mm).This extraordinary climatic and ecological diversity, coupled with a wide range of domestic and wildlife hosts, serve to accommodate the biological requirements of a variety of tick species.Hassan and Salih (unpublished data) report that factors such as animal movement, habitat change, drought, desertification and global climatic changes may force ticks to extend their distribution ranges beyond their known geographic regions.They report that A. variegatum has extended its range north of 12° N, whilst Hy. anatolicum has moved south of 14° N and R. (B.) annulatus was found in the semiarid zone.Abdalla and Hassan (2010) have recently reported on the distribution of A. variegatum, Hy. anatolicum and R. (Boophilus) species in various localities of Darfour State.
The distribution of some tick-borne diseases has been altered to some extent because of certain changes in the environment, the movement of animals to new pastures and the spread of certain tick species to new ecological zones.Heartwater, for instance, was originally restricted to the eastern parts of the country where a recognised vector, A. lepidum, was abundant (Abdel Rahim & Shommein 1984;Karrar et al. 1963).According to Osman and Hassan (2003), A. lepidum is restricted to the eastern region, from Torit to Kapoeta in the south to Kassala in the north.Abdalla (2007) reported the presence of antibodies to Ehrlichia ruminantium (Heartwater causative agent) in Umdafug and in Reheid-arbirdi in southern Darfour State, and concluded that these results were due to changes in the geographic distribution of ticks and hence the disease.Furthermore, heartwater has recently become endemic in Kordofan and Darfour (Mohammed, unpublished data).
Tropical theileriosis (Theileria annulata infections) has been detected in new regions, to where the tick vector Hy.anatolicum has extended its distribution range (Abdalla 2007;Gaafar 2008).Salih et al. (2004) collected Hy. anatolicum from cattle at Umbenein, in the southern regions of the Blue Nile State, proving that the species has extended its distribution southwards, which may lead to the emergence of tropical theileriosis in these areas.Adam (2005) detected T. annulata antibodies around Nyala and in Elradom, southern Darfour.In the same state, Abdalla (2007) reported T. annulata antibodies in cattle in Eid-elfirsan and concluded that this finding is linked to geographic changes in the distribution of the vector tick.The recovery of Hy. anatolicum in several localities in Darfour State (Abdalla & Hassan 2010) confirm the observation.
Similarly, East Coast fever (Theileria parva infection) coincides with the distribution of R. appendiculatus in the southern part of South Sudan.The first outbreak of East Coast fever was reported in 1950 in the Kajo Kaji and Yei districts on the western bank of the Nile and extended up to Juba (Julla 1985(Julla , 1994)).The disease was found to be more prevalent in areas that were used for grazing during the dry season, namely Apuk toich, River Lol and the Aweil district (Zessin & Baumann 1982).In the south, scattered tick collections proved that R. appendiculatus has moved northwards up to Bore (Julla 2003) and may lead to the occurrence East Coast fever in the southern regions of the north.

Conclusion
In conclusion, numerous tick species are distributed throughout the Sudan and South Sudan and these include the economically most important vectors of disease.Several of the vector tick species have expanded their distribution beyond their previously recognised geographical zones, which may lead to the expansion of tick-borne diseases to new areas where outbreaks of disease are expected to be drastic.Furthermore, ticks and tick-borne diseases in the Sudan represent one of the most important obstacles to livestock production.Hence it seems that without control of ticks and tick-borne diseases, it would be almost impossible to increase livestock production with foreign-breed animals, selection from indigenous breeds or through cross-breeding (Osman 1976).