Advances in Biological Research 10 (4): 200-212, 2016ISSN 1992-0067© IDOSI Publications, 2016DOI: 10.5829/idosi.abr.2016.10.4.103107

Corresponding Author: Nejash Abdela, School of Veterinary Medicine, College of Agriculture and Veterinary Medicine, JimmaUniversity, P. O. Box 307, Jimma, Ethiopia. Tel: +251924124547.

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Bovine Theileriosis and its Control: A Review

Nejash Abdela and Tilahun Bekele

School of Veterinary Medicine, College of Agriculture and Veterinary Medicine, Jimma University, P.O. Box 307, Jimma, Ethiopia

Abstract: Arthropod transmitted hemoparasitic diseases are economically important vector-borne diseases oftropical and subtropical parts of the world including Ethiopia. Bovine theileriosis is a tick-borne hemoprotozoandisease of cattle caused by several theileria species and among them T. parva, the cause of East Coast feverand T. annulata, the causative agent of tropical theileriosis are the most pathogenic and economicallyimportant. The aim of this manuscript is to review currently available articles on the bovine theileriosis with aspecial attention to its control. Theileria have complex life cycles involving both vertebrate and invertebratehosts. Tropical theileriosis and East Coast Fever are disease transmitted by Ixodid tick of the genusHyalomma and Rhipicephalus, respectively. Furthermore, the sporozoites are transmitted to animals in thesaliva of the feeding tick. Bovine theileriosis is characterized by high fever, weakness, weight loss,inappropriate appetite, conjunctival petechia, enlarged lymph nodes and anemia. PCR is the most beneficialmolecular tool for diagnosis of infection till date than blood and lymph node smear examination and serologicaltests. Bovine theileriosis has global economic significance thus prevention is the best method to control lossesrelated with the disease. Among Several control methods the most practical and widely used method is thechemical control of ticks with acaricides. However, tick control practices are not always fully effective and hencevaccination is the most sustainable option. Since there is difference in breed of cattle to tick resistance theselection of tick resistant cattle breeds is also proposed as a sustainable approach for controlling infection indeveloping world. Currently occurrence of tropical theileriosis is confirmed in Ethiopia thus, more researchshould be conducted to design and implement appropriate controland prevention strategies.

Key words: Hemoprotozoan Theileria Tick Tropical theileriosis East Coast Fever

INTRODUCTION Theileriae are obligate intracellular protozoan

Arthropod transmitted hemoparasitic diseases are throughout much of the world (some species also infecteconomically important vector-borne diseases of tropical small ruminants). They are transmitted by ixodid ticks andand subtropical parts of the world including Ethiopia [1]. have complex life cycles in both vertebrate andThey are of great economic impact on livestock affecting invertebrate hosts [7]. There are a number of species of80% of the world cattle population and causes economic Theileria spp. that infect cattle; the two most pathogenicloss due to morbidity and mortality [2]. Haemoprotozoan and economically important are T. parva and T. annultadiseases are causing devastating losses to the livestock [4, 6- 8]. Theileria parva occurs in 14 countries [9] inindustry and thus pose major constraints to the dairy sub-Saharan Africa causing East Coast fever (ECF) andindustry throughout the world [3,4]. Theilerioses is also still ranks first among the tick-borne diseases of cattle ina tick borne protozoal disease in ruminants caused by sub-Saharan Africa, whilst T. annulta occurs in southernhemoprotozoan parasites belonging to the genus Europe as well as North Africa and Asia [7]. Theileria [5]. The parasites belonging to this genus are Tropical theileriosis, also known as Mediterraneandistinguished on the basis of a distinct group of unique coast fever, is an extremely fatal and debilitatingorganelles called apical complex [6]. tick-transmitted disease infecting cattle [6]. Tropical

parasites that infect both wild and domestic Bovidae

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theileriosis is caused by T. annulata [10] and transmitted Order: Piroplasmida and Family: Theileriidae, Genus:through Ixodid tick of genus Hyalomma. About 250 million Theileria [9, 20]. Theileria are phylogenetically mostcattle are at risk to Tropical theileriosis worldwide [11]. closely related to members of the Babesia genus under theTheileria parva, is also most pathogenic species in Africa phylum Apicomplexa. The Phylum Apicomplexathe cause of another commercially important parasitic comprises a large group of complex eukaryoticdisease called East coast fever [12] which is characterized organisms known to be obligate parasites ofby enlargement of superficial lymph nodes and a vertebrates and invertebrates [21]. The phylum issustainable fever [5]. This infection causes mortality in divided into four principal groups; the Coccidia,about one million cattle annually in central, eastern and Gregarinasina, Haemospororida and the Piroplasmoridasouthern Africa. It threatens almost twenty five million [22]. The Piroplasmorida comprises two main generacattle in Africa and also limits the introduction of (Babesia and Theileria) and responsible for theimproved breeds [6]. Hence the diseases have global economically important diseases of domestic and wildserious economic impact in view of mortality, reduced milk animals [21].yield, weight losses, abortions and control and prevention Globally, Theileria annulata (cause of tropicalcosts [13]. Several methodologies are currently available theileriosis) and Theileria parva (causes of Eastfor the control of bovine theileriosis the most practical Coast fever) are the most economically importantand widely used method is the chemical control of ticks tick-transmitted pathogenic species causing bovinewith acaricides and vaccinations [14]. theileriosis [4, 8]. These Protozoal parasites are round,

There are no clinical or serological reports of the ovoid, rod like or irregular shaped organism foundpresence of East Coast fever (T. parva) and its vector in lymphocytes, histiocytes and erythrocytes [4].R. appendiculatus in Ethiopia. However, there is relatively Theileria mutans, T. orientalis/buffeli, T. velifera anduncontrolled movement of livestock from southern Sudan T. taurotragi can also infect domesticated ruminantsand Kenya, where the disease and vector (the brown ear [7] and they are believed to cause mildertick) are found, suggests that there is high risk to be and/or nonpathogenic theileriosis. However, recently,introduced [15]. Some of the past studies confirmed that T. orientalis complex caused significant morbidity,T. mutans, T. velifera, and T. orientalis infect cattle in economic losses and/or mortality in cattle in thewestern, eastern, and southern Ethiopia [16-18]. Asia-Pacific region [23].Gebrekidan et al. [19] also reported a widespreaddistribution of Theileria spp. among domestic ruminants Life Cycle: The life cycle of Theileria parasite is complex,in northern Ethiopia in which bovine tropical theileriosis involving morphologically distinct phases in two hostsis reported for the first time. [6]. Theileria sporozoites enter their bovine host during

In spite of aforementioned situation of bovine tick feeding and they rapidly invade mononucleartheileriosis and the economic importance of the diseases leukocytes, where they mature into macroschizonts andthroughout the world there is paucity of well documented induce proliferation in host cells [24]. Microschizontsinformation specifically in Ethiopia. Accordingly, gradually develop into macroschizonts and ultimatelythe motivation for this review arises from the recognition into merozoites, which are released from leukocytes.of global economic importance of the disease and These merozoites invade erythrocytes and develop intopossibility of the disease occurrence in Ethiopia. piroplasms [25]. A generalized lifecycle for the genusTherefore, the main objective of this paper is to review Theileria include secretion of infective sporozoites duringcurrently available articles about bovine theileriosis with tick feeding into the feeding site (Figure 1). Sporozoitesa special attention to the control of the disease. then infect leukocytes and multiply by merogony,

Literature Review blood cells thereby establishing the piroplasm stage.Etiologic Agent and Taxonomy: Theileriosis results from During a next feeding cycle, larval or nymphal vector ticksinfection with obligate intracellular protozoa parasites in ingest piroplasms and the released parasites undergothe Kingdom of Protista, Subkingdom: Protozoa, syngamy in the tick gut, forming a zygote, the onlyPhylum: Apicomplexa, Class: Sporozea, Subclass: diploid stage. The zygote divides into motile kinetes thatPiroplasmia (piroform, round, rod-shaped parasites), infect the tick gut epithelial cells and migrate to the

after which merozoites are released, which invade red

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Fig. 1: A generalized life cycle of the Theileria parasiteSource: Mans et al. [21]

haemolymph and subsequently infect the salivary glands. (tropical theileriosis) occurs from southern Europe and theAfter moulting and commencement of feeding by the tick, Mediterranean coast through the Middle East and Northsporogony results in the multiplication of sporozoites in Africa and into parts of Asia [28]. The disease isthe salivary gland acini before injection into the feeding prevalent in the South Eastern Europe, Southern Europesite by nymphs or adult ticks [21]. (Portugal, Spain, Italy, Bulgaria, Greece and Turkey) the

Epidemiology: Theileria epidemiology considers parasite Tropical theileriosis has also been reported in Ethiopianand vectors distribution, mortality and morbidity of cattle by Gebrekidan et al. [19]. It is important todisease outbreaks, risk factors and, host range which emphasize that endemic region of T. annulata andincludes host resistance and susceptibility [12]. T. parva do not overlap [7] however, there were reports of

Geographical Distribution: The geographical distribution Theileria parva (East Coast fever) is found inof tropical theileriosis, is mainly determined by the sub-Saharan Africa (Table 1) and is prevalent in fourteenlocation and biology of its vector, ticks of the genus countries in Southern, Central and Eastern Africa [9].Hyalomma [26]. Therefore, the incidence of the disease The affected countries are Kenya, southern Sudan,has a seasonal occurrence, which is modulated by Burundi, Tanzania, Malawi, Rwanda, Zaire, Mozambique,the ecology of its vectors [27]. Theileria annulata Zambia, Uganda and Zimbabwe [12]. Theileria mutans

near and Middle East, India, China and Central Asia [27].

coexistence in southern Sudan [28].

Table 1: Different species of Theileria affecting domestic animals and their vectors and Distributions

Species Host Vector Disease Distribution

T. parva Cattle and Buffalo R. appendiculatus East Coast Fever East, Central AfricaR. zambezienesis

T. annulata Cattle Hyalomma Tropical theileriosis Southern Europe, North Africa, Middle East, Sudan, central Asia andIndian subcontinent

T. mutans Cattle buffalo A. variegatum Benign bovine theileriosis Sub-Sahara Africa and possibly the Caribbean

T. hirci Sheep and goat Hyalomma Malignant theileriosis of North Africa, South Europe, Middle East. AsiaSheep and goats.

Source: Mohammed, [29]

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has been found in African and on some Caribbean islands breeds, compared with ~ 20 % in indigenous breed [32].and was reported from the U.S. in 1950 and 1975. Age is one risk factor for example in the recent study byTheileria velifera and T. taurotragi occur in Africa [28]. Saeed et al. [10] the prevalence of tropical theileriosis inTheileria orientalis/buffeli is widespread throughout young animals (23.4%) showed a higher prevalence thanthe world. Infection is generally subclinical; however, did adults (15%). Innate immunity in calves is notdisease can occur in cattle depending on a number of developed enough to combat T. annulata. Furthermore,epidemiological factors including previous exposure to in the result of reviewed study prevalence was found totheileriae, stress or health status and variations in the be higher in females (24.6%) than male (13.1%).species pathogenicity [7]. Environmental Factor is also a risk factor for bovine

Host Range: Theileria species infect a wide range of both activity, mainly during summer but a single tick can causedomestic and wild animals [21] Theileria parva can infect fatal infection [33]. The presence of ticks on animals ancattle, African buffalo (Syncerus caffer), water buffalo and important risk factor for the spread of theileriosis [25].waterbucks. Symptomatic infections are common only in Saeed et al. [10] reported as there is higher prevalence ofcattle and water buffalo [28]. Theileria parva is T. annulata in hot dry summer. High ambient temperaturehighly virulent for European dairy cattle, however, in this season provides an environment conducive tothe indigenous cattle breeds and African buffaloes growth and multiplication of ticks and ultimately increasesin endemic areas have a natural resistance to this the transmission of theileriosis. Theileria species [30]. The introduction of T. parvainfection into a previously unexposed cattle population Transmission: Knowledge about tick vectors,results in an epidemic situation with mortality up to 95% their intensity and abundance is crucial studyingin all age categories of cattle [5]. epidemiology of theileriosis [6]. Almost 80% of the cattle

Theileria annulata occurs in cattle (Bos taurus are exposed to tick infestation worldwide [34] and ticks areand Bos indicus), yaks, water buffalo and camels [26]. responsible for severe economic losses both through theMildly pathogenic and nonpathogenic species found direct effects of blood sucking and indirectly as vectorsin cattle include T. mutans, T. buffeli, T. velifera, of pathogens and toxins. Feeding by large numbers ofT. taurotragi and T. sergenti has also been recognized. ticks causes reduction in live weight gain and anaemiaTheileria spp. has also been found in most wild Bovidae among domestic animals [35]. Warm and moist climate isin Africa and reported in wild animals in other continents. conducive for rapid growth and development of ticks [3].T. lestoquardi, T. separata, T. ovis and other species Ticks are mostly found in the inguinal/groin region andoccur in sheep and goats [28]. Theileria annulata external genitals as these body parts are richly suppliedsporozoites can be transmitted to goat and sheep and with blood and the thinner and short hair skin is usuallycause mild febrile response, however limited experimental preferred by tick for infestation because mouth parts canstudies indicate that schizonts and piroplasms are not easily penetrate the vascular region for feeding [6]. produced in these host species [26]. Economically important Theileria species that infect

Risk Factor: The prevalence of theileriosis depends upon of the genera Rhipicephalus, Amblyomma, Hyalomma andgeographical region and several other factors like tick Haemaphysali. Theileria sporozoites are transmitted todensity, climatic conditions, age, gender, management animals in the saliva of the feeding tick [5]. Iatrogenicpractices and immunity [6]. Prevalence is also influenced transmission can also occur via blood (e.g., on re-usedby cattle breed as cattle usually differ in tick needles) [28]. Developmental stages of the parasite occurresistance and innate susceptibility to infection [31]. in the tick and they pass transstadially through the stagesTropical theileriosis is more severe in exotic and of larva, nymph and adult, but there is no transovariancross-bred cattle (Bos taurus) than indigenous animals transmission. Consequently, larvae or nymphs become(e.g., Bos indicus). For example, the disease became infected and transmit infection as nymphs or adults.significant in India when a program was launched to Adults are more efficient vectors than nymphs [30].increase milk production by introducing exotic breeds. Rhipicephalus appendiculatus is the most importantMostly, the disease occurs in its subclinical form, vector for T. parva, but R. zembeziensis and R. duttonileading to significant economic losses; without treatment carry this organism in parts of Africa [28]. These are threeor control, case fatality rates can reach 80 % in exotic host ticks because nymph, larvae and adult may not

theileriosis. The disease occurs when there is much tick

cattle and small ruminants are transmitted by ixodid ticks

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necessarily feed on the same host. The nymph and larval node draining the area of attachment of the tick, usuallyinstars of tick acquire infection through blood meal the parotid node. Infected lymphocytes are transformedand leave the host before molting to the next stage. to lymphoblasts which continue to divide synchronouslyBoth nymph and larvae are responsible for further with the schizonts so that each daughter cell is alsotransmission of infection by attaching to the new host. infected [5]. Eventually, infected lymphoblasts are[6]. Theileria annulata is transmitted by ticks in the disseminated throughout the lymphoid system and in nongenus Hyalomma [10]. These are two host ticks because lymphoid organs where they continue to proliferate. Later,the larva molt to nymph on the same cattle. The nymph some schizonts differentiate into merozoites, are releaseddetaches and drops off of the ground to molt into an adult from the lymphoblasts and invade erythrocytes whichand seeks a new host [6]. Theileria mutans and T. velifera lead to development of anemia [21]. In generalare transmitted by Amblyomma spp. Ticks in the genus pathological damage is induced in cattle by schizont stageRhipicephalus spread T. taurotragi [28]. of T. annulata and T. parva. The cells infected by

Morbidity and Mortality: Morbidity and mortality vary of both specific and nonspecific T lymphocyte resultingwith the host’s susceptibility and the strain and dose of in enlarged lymph nodes [6].the parasite. The case fatality rate for untreated EastCoast fever can be as high as 100% in taurine, zebu or Clinical Sign: The occurrence of the disease variessanga cattle from non-endemic areas. In contrast, depending on the parasite strain, the host’s susceptibilitythe morbidity rate approaches 100% among indigenous furthermore the quantity of sporozoites inoculated andcattle, but the mortality rate is usually low. Similarly, the severity of the disease is directly proportionaltropical theileriosis is more severe in introduced breeds, to the initial inoculum of sporozoites injected [27].with a mortality rate of 40-90%, while the mortality rate in Theileria annulata infection (tropical theileriosis) isindigenous cattle can be as low as 3%. Breeds of cattle characterized by high fever, weakness, weight loss,that are relatively resistant to experimental infection with inappropriate appetite, conjunctival petechia, enlargedT. annulata include the Sahiwal breed of Bos indicus and lymph nodes and anemia. Lateral recumbency, diarrheathe “Kenana” breed of B. taurus. Infections with Theileria and dysentery are also associated with later stages ofspp. other than T. parva and T.annulata are rarely fatal in infection [30, 36]. Unlike T. parva, which causes only acattle [28]. small reduction in circulating erythrocytes, mild to

Pathogenesis: The Theileria spp. can be grouped into although pathology produced by the schizont stage isschizont “transforming” and “non-transforming” species. usually the primary cause of mortality [14].Non-transforming Theileria are regarded as being benign In case of ECF cattle may also develop an extremelybut still able to cause disease as a result of anaemia fatal condition referred to as turning sickness. In thisinduced by the piroplasm stage [21]. Pathogenesis of disease, capillaries of central nervous system are blockedvarious forms of theileriosis is dependent on the by infected cells and leads to neurologic symptoms [6].production of schizonts in lymphocytes and piroplasms The incubation period varies from 4 to 14 days afterin erythrocytes [30]. The severity of infection depends attachment of the infected ticks to the host. The diseaseupon virulence of the causative strain, the quantum of may last as little as three to four days in the acute form orinfection, the susceptibility status, age and health of the may be prolonged for about 20 days [27]. Studies in Japanhost [27]. Thus, T. parva, T. annulata and T. hirci by Chaisi et al. [37] indicate that some T. orientalisproduce numerous schizonts and piroplasms and are very parasites can cause transient anaemia, with clinical signspathogenic; T. mutans, T. buffeli and T. avis rarely in up to 2.5% of animals and occasional mortalitiesproduce schizonts but may cause varying degrees of (<0.1%) The main clinical manifestations are fever,anemia when piroplasms are many in red blood cells; haemolytic anaemia of variable severity and mortality inand with T. velifera and T. separata, no schizonts have some animals; infection is also associated with anbeen described, the parasitemia is usually scanty and the increased incidence of abortion and stillbirths andinfection is mild or subclinical [30]. significant reductions in milk yields in affected herds [14].

Sporozoites of T. parva are injected into the bovine Theileria mutans infection can result in mild clinical signs,host by the tick in its saliva. The sporozoites then enter but pathogenic strains in eastern Africa cause severelymphocytes and develop into schizonts in the lymph anemia, icterus and sometimes death [18]. In general

schizonts induce massive and uncontrolled proliferation

moderate anaemia is observed in tropical theileriosis,

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benign theileriosis is characterized by moderate to severe assay recommended by the OIE for most economicallyanemia in heavily parasitized cattle and moderate important parasites [7]. However, the biggest problemenlargement of lymph nodes [30]. with the IFAT is the significant cross-reactivity observed

Diagnosis: For routine diagnosis of bovine theileriosis, T. parva and T. taurotragi antigen and anti-sera has beenconventional methods are used, whereas serological and observed [21].molecular methods are utilized for research purposes and ELISA can also be used in diagnosis of bovineepidemiological studies. Conventional methods involve theileriosis and the test is easy to perform, can diagnosemicroscopic examination of Giemsa stained thin/thick a large number of samples in a short time and it is lessblood films for detection of piroplasms and lymph node laborious [29]. However, these methods are also notbiopsy smears for detection of schizonts. The mostly reliable due to their limitations. There are chances of crossused serology tests are Indirect Immunofluorescent reactivity and may confront false positive and falseAntibody Test (IFAT) and Enzyme Linked negative results. Theileria piroplasm may occasionally beImmunosorbent Assay (ELISA) [9]. Diagnosis of acute present in the erythrocytes of long-term carriers whereastheileriosis can also be based on clinical signs antibodies have a tendency to disappear. The animals(rise in body temperature, enlarged superficial lymph may still be infected despite of negative serological test.nodes), knowledge of disease and vector distribution as Precise identification of carrier cattle is of crucialwell as examination of Giemsa-stained (either in smears of importance as they are capable of transmitting infection toneedle aspirates from enlarged lymph nodes or blood non-endemic regions [6].smears) [7]. Definitive identification of the Theileriaspecies involved sometimes requires the application of Molecular Tools: Molecular tools can be used tospecies-specific PCR assays [14]. differentiate Theileria specie. The tests have proved to be

Microscopic Examination: Traditional diagnosis of in blood [9]. Polymerase chain reaction (PCR) hasbovine theileriosis is mainly based on the microscopic largely superseded other methods and is widely usedexamination of blood smears for the presence of the specie-specific molecular diagnostic assay in veterinarymerozoites stage of Theileria [38]. This method is parasitology to determine piroplasm carrier animals.frequently used for detection as it is comparatively However, these methods are laborious, expensive;inexpensive. However, the method is insensitive and not require specialized equipment and technical skills [6, 38].suitable for carrier animals because the pathogen level is PCR could detect parasites at 0.000001% parasitaemia,usually low in the blood stream making it an unreliable allows direct, specific and sensitive detection of parasitetechnique for accurate results [6]. Morphological and differentiation of different piroplasms infectingdifferentiation of T. annulata and T. parva is also difficult, animals [29]. Kohli et al. [3] reported 27.2% prevalence ofbut both species are geographically separated [39]. theileriosis by blood smear examination while using PCR,One of important character of theileriosis is that once the prevalence was reported to be 32.5 %. Similarly,animal recovered from the primary infection, the animal most recent research by Saeed et al. [10] used bloodwill become a carrier for a long time. At this stage, smear examination and PCR and Prevalence was 1.9 % andthe animal has very low parasitemia which is difficult to 19.3% respectively indicating that PCR is more sensitivedetect by a microscope [38]. Therefore, high sensitivity than blood smear examination. and specific assays for detection of these pathogens fromthe subclinical animals are needed [6]. Preventions and Controls

Serological Tests: Serological tests are reliable methods the high prevalence of carrier state infection and the highfor detection of low grade or previous infections where costs of treatment, prevention is the best mean to controlmeasurement of antibody levels of a cattle herd is used for Thelerial infection; it consists of two types of action:assessing the response to natural infection and also to (i) control of the vector tick through one or more controlvaccination for the purpose of disease control [9]. options [6] and (ii) vaccination [40]. Animals can beSerological method depends on antigens and antibodies protected from both East Coast fever and tropicalreaction. Antibodies can be detected by different theileriosis by vaccination. Attenuated vaccines are usedserological tests but IFAT remains the gold standard to control tropical theileriosis in some countries.

between closely related species. Cross-reactivity between

highly sensitive and specific for detecting parasite DNA

Preventions: Due to the high costs of theilericidal drugs,

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Vaccination against East Coast fever is done by population is entirely free of the disease or there issimultaneously injecting virulent T. parva and an endemic stability [27]. Newly purchased cattle may first beantibiotic (usually a long-acting tetracycline). properly examined before mixing with the existing stock.Considerations in T. parva vaccination include the If the number of ticks or tick infested cattle is small,possibility of introducing live organisms into areas where manual removal of tick is a common practice. Forefingersthey are not currently endemic [28]. Control of the vector are used to grasp ticks and twisted counter-clock wise.tick is one of the widely used methods to prevent The removed ticks are, then, put on the smoldering dungoutbreaks. The control option for vector and vaccination cake to kill them [43]. will be discussed in detail in the following topics.

Control Methods: Calves infected with several other factors influencing the epidemiology of bovinebovine tick-borne blood pathogens, including theileriosis. It has been achieved mainly by application ofBabesia species and Anaplasma marginale, acaricides [27] and acaricides may be applied to kill ticksshow enhanced resistance to disease in the first six in both free living as well as parasitic stages. Tick free ormonths of life, enabling them to acquire immunity to these acaricide treated cattle have better productivity aspathogens in regions where the infections are endemic. compared to tick infested cattle. Acaricides are applied bySuch age-related resistance is not seen with T. parva or spraying, injections, spot-on or dipping but human safetyT. annulata, There is no any evidence that maternally is of utmost importance in acaricide application.derived antibodies are protective [41]. Because of the Prolonged and repeated contacts with skin should beabsence of such protective mechanisms and the fatal avoided. Hands and face should be properly washednature of the diseases in susceptible stock, control of before eating [43]. disease caused by these highly pathogenic Theileria is Dipping is considered the most effective method forparticularly challenging [14]. So it is important to design acaricide application [27]. Dipping tanks are usuallyand implement control strategies to prevent outbreaks in covered with a roof to avoid dilution by rain orendemic and non-endemic regions on a priority basis [42]. evaporation. It is important to carefully adjust dip

Several methodologies are currently available for the concentration according to the recommendation. Poor orcontrol of bovine theileriosis [27] and various cost incorrect application of even highly effective acaricideeffective prophylactic measures are used to control and gives unsatisfactory results and develops acaricidalminimize economic losses to dairy farms globally, resistance. Dipping of cattle less than 3 months is nothowever, all of these need to be integrated in such a recommended. Wounds of cattle must be thoroughlymanner that they meet the specific requirements of checked before dipping, otherwise, it can causelivestock holders in different situations [6]. The most discomfort and toxicity. The heads of cattle must bepractical and widely used method is the chemical control dipped once or twice in the solution. Cattle that are thirstyof ticks with acaricides. However, tick control practices or fatigued shouldn’t be dipped [43]. Despite itsare not always fully effective for a number of reasons, effectiveness Dipping become very expensive andincluding development of acaricide resistance, the high inconsistent due to lack of facilities such as finances forcost of acaricides, poor management of tick control rehabilitation of dip tanks, provisions of acaricides andand illegal cattle movement in many countries. water [9].Thus, vaccination using attenuated schizont-infected cell Acaricides can also be applied with hand spraylines has been widely used [7]. which is environmental friendly practice, easy to operate

Management: Good management is one control option in only. For effective control, it is important to moisten thecontrolling bovine theileriosis. Management involves hair as well as skin with spray [6]. There are certain bodyrestriction of livestock movement and implementation of parts of cattle that escape treatment by spraying andquarantine measures to keep the tick free and disease dipping. Such predilection sites include inner fringessusceptible cattle apart from the tick-infested and infected of ear, under part of tail and legs and require specialanimals. This is also to ensure that ticks and the attention. Selective application of acaricides to these sitespathogens they transmit are not transported to is called hand dressing and is done as a supplement toecologically suitable but currently uninfected areas. usual dipping [43]. Other options for controlling ticks areThe overall objective is to ensure that the target ecological and biological. Ecological control method is

Vector Control: Tick control is one of the most important

and economical but is suitable for small herds

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used for habitat and host linked treatment. Tick control in Recovered animals demonstrate a robust immunity tothe habitat and vegetation requires modification of the homologous challenge, which usually lasts for the lifetimeplant cover by removal of vegetation that shelters ticks. of an animal [7].Biological control, include predators like rodents, birds, The result of most recent study in Kenya byants [35]. Woolhouse et al. [45] suggested a novel alternative

Selection of Tick Resistant Cattle Breeds: T. mutans or T. velifera, without the need for treatmentDifferent breed of cattle are different in their susceptibility and helping calves to survive their first exposure toto theileriosi for example exotic cattle and their crossbreds T. parva and develop immunity. This Successful ECFare highly susceptible, while indigenous cattle are control would benefit an estimated 30 million cattle inrelatively resistant to tropical theileriosis [10]. sub-Saharan Africa, reducing the costs of treatment asLow prevalence of parasite is reported in Sahiwal cattle well as reducing demand for both antibiotics andthan European breeds suggesting that Sahiwal cattle are acaricides.more resistant to tick infestation and tick borne diseases[44]. It is widely known that Bos indicus cattle are more Chemotherapy: Acording to OIE [7] chemotherapeuticresistant to ectoparasites than are Bos taurus animals. agents such as parvaquone, buparvaquone andThere are great differences between these two breeds of halofuginone are available to treat T. annulata andcattle in regard to their susceptibility to parasitism by T. parva infections. These best Theilericidal drugscattle ticks [35]. In general sense rearing disease-resistant belong to the hydroxynaphtoquinones family [40].breeds play significant role in controlling bovine Naphthoquinone compounds were discovered in 1970theileriosis. Hence selection of cattle breeds with with a wide therapeutic index [12]. These naphthoquinoneenhanced tick resistance is proposed as a sustainable compounds are not only effective for curing theileriosistactic for controlling infection in developing world [6]. but can also be used as a remarkable prophylactic

Immunization: Control of the disease by prevention of OIE [7] treatments with chemotherapeutic agents do nottick infestation requires essentially continuous completely eradicate theilerial infections leading to theapplication of acaricides and is therefore expensive and development of carrier states in their hosts. Parvaquonedifficult to sustain. Furthermore it can result in acaricide (Parvexon ND, Bimeda) is mainly active drug againstresistance. Because of the shortcomings of these control schizontes; it should be injected intramuscularly at themeasures, vaccination is seen as the most sustainable dose of 20 mg/kg. Buparvaquone is active against bothoption for control of the disease [14]. The attempt of schizontes and piroplasmes; it is injected intramuscularlyimmunization in cattle against tropical theileriosis was first at the dose of 2.5 mg/kg. Its efficacy after a singlemade in Algeria in 1930s. Blood with low virulence strain injection was estimated to 92%, which is higher thanwas donated from infected cattle followed by mechanical parvaquone [40]. passage between healthy cattle. This practice resulted in However, these naphthoquinone compounds are notsubsequent loss of parasite’s ability to differentiate into used by cattle breeders due to their high price [12] andmerozoites with one year estimated protection in the drugs infiltrate the muscles and are not easily eliminatedabsence of natural challenge [6]. from the cattle’s body [6]. The meat and milk products

Successful vaccination against T. annulata and may be contaminated with drug residues leading to healthT. parva has only been achieved using live parasites. hazards [46]. Drug resistance is also reported in TunisiaA method of vaccination against T. annulata, based on recently; 4 out of 7 cattle died of acute tropical theileriosisthe use of parasitised cell lines in which the parasite had in spite of buparvaquone injections [47]. Similarly, 7 outbeen attenuated by up to 200 passages in vitro [14]. of 8 cattle died in southern Iran, though buparvaquoneThe vaccination for T. parva control is based on a method treatment was given [48]. Mechanism of buparvaquoneof infection and treatment (ITM) in which cattle are given action has not been fully elucidated. However, productsa subcutaneous dose of tick-derived sporozoites and a belonging to the hydroxynaphtoquinones probably actssimultaneous treatment with a long-acting tetracycline by binding to cytochrome b (cyt b) inhibiting the electronformulation. This treatment results in a mild or inapparent transport chain in the parasite [49]. Theileria annulataEast Coast fever reaction followed by recovery. and T. parva show similar disease symptoms and the

approach, inoculation of young calves with more benign

measure against the disease [6]. However, according to

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symptoms include immune-depression and secondary diseases are of the major constraints to the livestockbacterial infection e.g. pneumonia and enteritis. Antibiotic industry of the country [35]. A number of researchers aretreatment is usually recommended to limit such secondary reporting presence of different Theileria species frominfections [6]. Tetracycline antibiotic was probably the different area of Ethiopia (Table 2). For examplefirst chemotherapeutic compound used against ECF in Gebrekidan et al. [19] reported a widespread distribution1953. This antibiotic is effective only at the early stages of Theileria spp. among domestic ruminants in northernand can’t be used at later stages of infection [12]. Ethiopia. The circulation of Theileria spp. in Ethiopia is

Plant called Calotropis procera locally named as also indicated by Solomon et al. [16], who reported 30.9%Thophiya (Tobia) are reported to have killing or repealing seropositivity to T. mutans in cattle from the Yabeloeffects on tick in North Gondar, Ethiopia [50]. This plant district.is found as wild plant in Asia and Africa and has In previous studies, conducted by Sileshi et al. [53]multipurpose chemotherapeutic activities and can be T. orientalis and T. velifera were reported from Gambellaeffectively used to treat bovine theileriosis [6, 51]. region, western Ethiopia. Theileria mutans has been

EconomicImportance of Bovine Theileriosis:Theileriosis Furthermore, its vectors are commonly found in differentcauses major constraints on livestock development in regions of Ethiopia [54]. The average seropositivity ofAfrica, Asia and Middle East. The disease causes high T. mutans (54.2%) was reported in Ghibe valley by Felekemorbidity and mortality in exotic cattle, thus inhibiting et al. [54] indicating that the population is in the state ofthe introduction of improved cattle into endemic areas. enzootic instability. Gebrekidan et al. [19] reported theThe consequence is that the quality of cattle in endemic presence of three Theileria species in cattle in Addisareas remains low, therefore impeding the development of Zemen, i.e. T. velifera, T. mutans and T. orientalisthe cattle industry and the wellbeing of producers and complex. The previous studies confirmed that T. mutans,their families [5]. Theileria annulata causes severe T. velifera, and T. orientalis infect cattle in western,financial losses due to live weight decrease, a drop of milk eastern, and southern Ethiopia [15-18].yield, abortions and in some cases deaths. Moreover, In addition recent study conducted bythe treatment of this disease is very expensive [40]. Gebrekidan et al. [19] indicated that four species ofMost important loss from T. annulata, representing Theileria including T. velifera, T. mutans, T.between 22% and 38% of the overall losses, is the loss in orientalis complex and T. annulata were found inmilk yield from carriers of the disease [52]. In Eastern, northern part of Ethiopia (Table 3) (Addis Zemen,Central and Southern Africa due to East Coast fever, Humera and Sheraro) with infection rates of 66 %, 8%, 4%,about one million cattle per year die, with a further 28 and 2%, respectively. Furthermore the study reported themillion of the 47 million cattle in the region being at risk of presence T. annulata, the cause of tropical theileriosis, incontracting the disease [9]. Ethiopia (Humera) for the first time. There are no clinical

Status of Bovine Theileriosis in Ethiopia: Similar to other (T. parva) and its vector in Ethiopia. However, there iscountries, there are a considerable number of relatively uncontrolled movement of livestock fromeconomically important livestock diseases occurring southern Sudan and Kenya, where the disease and vectorin Ethiopia. Among others, tick borne haemoparasitic are found ensures that a considerable risk exists.

known for a long time to occur in Ethiopia [15].

or serological reports of the presence of East Coast fever

Table 2: Report of Theileria species from different area of Ethiopia Theileria species Area Samples diagnostic methods test ReferenceT. mutante southern and eastern Ethiopia Blood Microscopic and serology [16, 18] T. annulata Northern Ethiopia blood PCR [19]T. orientalis Northern Ethiopia blood MT- PCR [8]

Table 3: Distribution of Theileria spp. infections in cattle in Northern EthiopiaStudy site No. of animals PCR+ n (%) T. velifera n (%) T. mutans n (%) T. orientalis complex n (%) T. annulata n (%)Addis Zemen 59 48(81.4) 38 (64.4) 6 (10.2) 4 (6.8) –Sheraro 21 18(85.7) 17 (81) 1 (4.8) – –Humera 20 14 (70) 1 (5) – 2 (10)Total 100 80(8) 66 (66) 8 (8) 4 (4) 2 (2)Source: Gebrekidan et al. [19].

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If infected ticks become established on the climatically As the tropical bovine theileriosis is reported infavorable highlands of Ethiopia, close to 100% Ethiopia, research should be conducted to designmortality of improved and indigenous cattle could and implement appropriate disease control andoccur [15]. prevention strategies.

The most recent study in Ethiopia detected and Continuous and reliable sero-surveillance should becharacterized T. orientalis in local cattle and found as performed on the borders to prevent and control themost pathogenic of T. orientalis genotypes is low and introduction of East coast fever to Ethiopia.dominant is non-pathogenic genotype. Therefore, the lowintensity of infection of pathogenic genotypes of REFERENCEST. orientalis may explain why clinical oriental theileriosisis uncommon in Ethiopia [8]. 1. Sitotaw, T., F. Regassa, F. Zeru and A.G. Kahsay,

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