**3.1 Etiology**

Theileriosis is caused by Theileria spp. in cattle, goats, sheep and wild and captive ungulates (Radostits et al., 2000). Theileriosis is a hemoparasitic disease caused by protozoa of the genus Theileria (Apicomplexa). Theileria species affect domestic and wild ruminants, especially in Africa, Europe, Australia, and Asia (Allison and Meinkoth, 2010). The parasites are transmitted by tick. These parasites, undergo repeated merogony in the lymphocytes ultimately releasing small merozoites, which invade the red cells to become piroplasms. Theileriosis, have a variety of tick vectors which cause infections ranged from clinically inapparent to rapidly fatal (Taylor et al., 2007).

The list of theileria species is shown in table 2.

#### **3.2 Epidemiology**

### **3.2.1 Bovine theileriosis**

Bovine theileriosis is caused by at least six Theileria species (Table 2). In bovine, East coast fever caused by T. parva. The tick vector is Rhipicephalus appendiculatus. East coast fever generally ocur in cattle but also buffalo (OIE., 2004), and occurs in East Africa. ECF is prevalent throughout the wetter areas, but is absent from the wet highlands in the horn of

Protozoan Diseases in Farm Ruminants 479

Theileria ovis is benign theileriosis in Africa (Radostits et al., 2008). But in China Theileria ovis is a serious disease (Miling et al., 2009). The incidence and mortality rates of Theileria ovis in adult sheep and goats were have found 17.12% and 65.78%; 8.06% and 73.33% respectively in China (Shuzhen et al., 2002). In Turkey, prevalence of infection of T. ovis in sheep and goats were have been 64.19% and 12.36%, respectively ( Sayn et al., 2009). The tick vectors of disease are Rhipicephalus bursa in the Mediterranean and Rhipicephalus

Pathogenesis of different form of theileriosis is based on the production of schizonts in lymphocytes and piroplasms in erythrocyte. T. parva, T. annulata and T. hicri produce highly schizonts and piroplasma and are very pathogenic; T. mutans, T. buffeli, and T. ovis unusually produce schizonts but may cause varying degree of anemia when piroplasms are

Theileia spp. are classified in to 2 groups. In first group (T. parva and T. annulata), proliferate is seen in lymphocytes but in the second group (T. orientalis) it is seen in

In Theileria parva incubation period is approximately1-3 weeks (Radostits et al., 2008). One or two days later, the first clinical sign is generalised swelling of the superficial lymph nodes, eyes, ears and submandibular regions. After few days there is anorexia, decreased milk production, loses condition, ceases rumination, rapid hearth beat, petechial haemorrhages under the tongue and on the vulva (Taylor et al., 2007). In cerebral theileriosis there are localized nervous signs and convulsions, tremor, salivation and head pressing

In Theileria annulata, pyrexia, anorexia, enlargement of superficial lymph nodes, nasal and ocular discharges and salivation is the most common signs. Constipation is recorded in some cases. Respiratory distress, coughing and pulmonary oedema are seen ( Osman and

In Theileria orientalis clinical signs are associated with anemia, jaundice and

Clinical signs in Theileria velifera is not reported but in Theileria taurotragi mild fever and

In Theileria hicri which is very pathogenic in sheep and goats, in the acute form there is fever, inappetence, ceases rumination, weakness, enlargement of superficial lymph nodes, diarrhoea, jaundice, haemorrhage in submucous may ocur. In chronic form there is fever, inappetence, emaciation, anemia and jaundice (Taylor et al., 2007). Theileria hicri is not

Theileria ovis that is benign theileriosis in sheep and goats, clinically is mild (Taylor et al.,

evertsi in Africa(Taylor et al., 2007).

highly in red blood cells (Radostits et al., 2008).

erythrocytes that causes hemolytic anemia (Magona et al., 2010).

**3.3 Pathogenesis** 

**3.4 Clinical findings** 

(Radostits et al., 2008).

lymphadenopathy (Taylor et al., 2007).

anemia are reported (Taylor et al., 2007).

reported in Turkey (Sayn et al., 2009).

Gaabary, 2007).

2007).

Africa (Norval et al., 1991). In Africa, T. parva is a highly fatal disease in cattle (Lawrence et al., 2004; Carlson, 2009a) and this disease is a great threat on the development of the livestock industry, with losses of about 10,000 cattle per year in Zambia (Nambota et al., 1994).


Table 2. Theileia species (Theileriosis)

In bovine, Tropical Theileriosis (Mediterranean coast fever), occurs in Mediterranean countries, Middle East, Indian and China, and is caused by T. annulata (Radostits et al., 2008). The tick vectors are Hyalomma dentritum in north Africa and in the Mediterranean countries, H. dentritum and H. dromedaii in central Asia, and H. marginatum in India ( Taylor et al., 2007; Radostits et al., 2008). In endemic areas indigenous cattle are relatively resistant while modified cattle, especially European breeds, are highly susceptible (Taylor et al., 2007).

Theileria orientalis complex is a milder disease than East coast fever and Tropical Theileriosis, and called benign theileriosis in cattle (Radostits et al., 2008). The tick vectors are Ambylomma variegatum, A. cohaerens, A. haebraeum, Haemaphysalis bispinosa that these vectors are the probable vectors in Australia (Taylor et al., 2007).

Theileria velifera has been described in cattle and zebu and is very mild theileriosis in Africa (Taylor et al., 2007; Radostits et al., 2008 ). The tick vectors are Ambylomma variegatum, A. lepidu and A. haebraeum (Taylor et al., 2007).

Theileia taurotragi has been described in cattle, antelope and eland. Geographical distribution of this disease is in Africa. The tick vectors are Rhipicephalus appendiculatus and Rhipicephalus pulchellus (Taylor et al., 2007).

Thieleria mutans has been seen in cattle and deer (Carlson, 2009a).

Theileria hicri is malignant theileriosis of small ruminants (Lawrence, 2004; ), and is enzootic in North Africa, Middle East, China and India. The tick vectors are Rhipicephalus bursa and Hyalomma anatolicum (Taylor et al., 2007).

evertsi in Africa(Taylor et al., 2007).

Theileria ovis is benign theileriosis in Africa (Radostits et al., 2008). But in China Theileria ovis is a serious disease (Miling et al., 2009). The incidence and mortality rates of Theileria ovis in adult sheep and goats were have found 17.12% and 65.78%; 8.06% and 73.33% respectively in China (Shuzhen et al., 2002). In Turkey, prevalence of infection of T. ovis in sheep and goats were have been 64.19% and 12.36%, respectively ( Sayn et al., 2009). The

**3.3 Pathogenesis** 

478 A Bird's-Eye View of Veterinary Medicine

Africa (Norval et al., 1991). In Africa, T. parva is a highly fatal disease in cattle (Lawrence et al., 2004; Carlson, 2009a) and this disease is a great threat on the development of the livestock industry, with losses of about 10,000 cattle per year in Zambia (Nambota et al.,

**Organism Livestock affected Geographic distribution**  T. parva Cattle, African buffalo East and central Africa T. annulata Cattle, domestic buffalo Mediterranean countries

T. orientalis complex Cattle Southern Europe, Middle

particularly the eland

T. ovis Sheep and goats Europe, Africa, India

modified cattle, especially European breeds, are highly susceptible (Taylor et al., 2007).

these vectors are the probable vectors in Australia (Taylor et al., 2007).

variegatum, A. lepidu and A. haebraeum (Taylor et al., 2007).

Thieleria mutans has been seen in cattle and deer (Carlson, 2009a).

and Rhipicephalus pulchellus (Taylor et al., 2007).

Hyalomma anatolicum (Taylor et al., 2007).

T. mutans Cattle, deer Africa, Caribbean Islands T. hirci Sheep and goats North and East Africa,

In bovine, Tropical Theileriosis (Mediterranean coast fever), occurs in Mediterranean countries, Middle East, Indian and China, and is caused by T. annulata (Radostits et al., 2008). The tick vectors are Hyalomma dentritum in north Africa and in the Mediterranean countries, H. dentritum and H. dromedaii in central Asia, and H. marginatum in India ( Taylor et al., 2007; Radostits et al., 2008). In endemic areas indigenous cattle are relatively resistant while

Theileria orientalis complex is a milder disease than East coast fever and Tropical Theileriosis, and called benign theileriosis in cattle (Radostits et al., 2008). The tick vectors are Ambylomma variegatum, A. cohaerens, A. haebraeum, Haemaphysalis bispinosa that

Theileria velifera has been described in cattle and zebu and is very mild theileriosis in Africa (Taylor et al., 2007; Radostits et al., 2008 ). The tick vectors are Ambylomma

Theileia taurotragi has been described in cattle, antelope and eland. Geographical distribution of this disease is in Africa. The tick vectors are Rhipicephalus appendiculatus

Theileria hicri is malignant theileriosis of small ruminants (Lawrence, 2004; ), and is enzootic in North Africa, Middle East, China and India. The tick vectors are Rhipicephalus bursa and

T. velifera Cattle, zebu Africa

T. taurotragi Cattle, antelope,

Table 2. Theileia species (Theileriosis)

(Portugal and Spain, the Balkans), Middle East, Indian subcontinent and

East, Asia, Australia

Middle East, India

China

Africa

1994).

Pathogenesis of different form of theileriosis is based on the production of schizonts in lymphocytes and piroplasms in erythrocyte. T. parva, T. annulata and T. hicri produce highly schizonts and piroplasma and are very pathogenic; T. mutans, T. buffeli, and T. ovis unusually produce schizonts but may cause varying degree of anemia when piroplasms are highly in red blood cells (Radostits et al., 2008).

tick vectors of disease are Rhipicephalus bursa in the Mediterranean and Rhipicephalus
