Theileriosis

Theileriosis is a vector borne disease of cattle, sheep and goat characterized by fever and lymphoproliferative disorders, which may be associated with leukopenia and anaemia. It is caused by Theileria sp and transmitted by ixodid ticks.

Theileria Species of Domestic Animals

Morphology

• Piroplasm forms in RBC are highly pleomorphic and most commonly occur as rod, round, oval (signet ring), annular and comma shape.
• Macro and microschizonts (Koch blue bodies) in lymphocytes and endothelial cells of the spleen or lymph node. The macroschizonts divide into microschizonts and produce merozoites.
• The merozoites are released from lymphocyte and invade the RBC.

Tropical Bovine Theileriosis

Tropical Bovine theileriosis is caused by Theileria annulata.

Life cycle

Epidemiology

• In India high incidence of disease mostly occur, during summer and rainy seasons (May – Oct) which is attributable to high incidence of tick vectors.
• In tropical areas, ticks are active throughout the year.
• Exotic and crossbred cattle are highly susceptible than zebu cattle.
• Both young calves (even 2-3 days old) and adults are affected.
• Mortality rate in non endemic area is 10-90%.
• In endemic areas, all animals are virtually infected but the case- fatality is 10 -20% and is confined to calves.
• Transtadial transmission (stage to stage) by Hyalomma spp ticks (Infection from tick larvae to nymph or nymph to adult occurs.
• Congenital transmission occasional in calves.
• Indigenous cattle without clinical signs, buffalo, wild animals and clinically recovered animals are act as a carrier.
• Recovery from infection leads to the development of premunity.
• No cross immunity between theileria species.
• Concurrent infection with Anaplasma and Babesia sp is common.

Pathogenesis

Clinical signs

• Incubation period: 9 to 25 days.
• The disease occur as peracute, acute, subacute, mild and chronic forms.

Peracute form

• Animal may die within 3-4 days of infection with high fever.

Acute form

• Most common and may last for 3-4 days and may be prolonged for  about 20 days.
• Fever (40.5 –41.5°C) is continuous or intermittent and persist for 3- 20 days.
• Inappetence, lacrimation, cessation of rumination, rapid heartbeat, respiratory distress, weakness, reduced milk production.
• Enlargement of superficial lymph nodes and odema of the eyelids.
• Laboured breathing, serous nasal discharge, coughing, restlessness and stary coat.
• Marked anaemia, bilirubinuria and bilirubinaemia, conjunctiva is icteric with petechial haemorrhage, jaundice, prostration and death.
• Haemoglobinuria occur in some cases.
• Diarrhoea with blood and mucus in faeces, the animal is greatly emaciated (RBCs < 1 million/ cmm) and death occur after 15 days of infection.

Subacute form

• Fever is irregularly intermittent for 15 days, and then animal recovers.
• Pregnant animal may abort.

Mild form

• Mild fever, inappetence, listlessness, slight digestive disturbances, lacrimation for few days and moderate anaemia.

Chronic form

• Intermittent fever, inappetence, marked emaciation.
• Ssome degree of anemia and icterus may persist  for 4 weeks or longer.
• In some cases, acute form may supervene depending upon stress factors and  animal may die within  1-2 days.

Cerebral theileriosis

• Nervous signs are predominate and brain impression smears reveal Koch’s Blue bodies.

Cutaneous form

• Small subcutaneous nodules containing schizonts rarely occur.

Clinical pathology

• Haematological changes.
• Haemoglobulin level (< 2 gm/dl).
• Total RBC count (1.5-2 million/ Cmm).
• Decreased PCV.
• Initial leukocytosis is followed by leukopenia in later stage of infection.

Diagnosis

• Based on clinical signs and post mortem lesions.
• Demonstration of erythrocytic forms (piroplasms) in peripheral blood smears.
• Demonstration of Koch’s blue bodies (schizonts) in lymphocytes from lymph nodes biopsy.
• For latent cases, serological tests can be employed CFT, Capillary tube agglutination test, IFA,  IHA, AGID, Dot-ELISA, LMIT, Conglutination Complement Absorption test (CCA), Gel agglutination test, immunoelctrophoresis to identify antibodies.
• Leukocyte migration inhibition test is commonly used to assess the cell mediated immunity.

Differential diagnosis

• Anaplasmosis
• Babesiosis
• Trypanosomosis
• Ehrlichiosis

Treatment

• Naphthaquinone drug –  Inj. Buparvaquone (Butalex) –  drug of choice. 
• Inj. Buparvaquone (Butalex) @ 2.5 mg/kg b.wt, deep I/M, The second should be given within 48 hrs in severe cases.
• Hematinic supportive therapy  can be given to combat anemia along with inj. Buparvaquone.
• Parvaquone – 10 mg/kg, deep I/M, effective against piroplasmic stage.
• Berenil (Diminazene aceturate) – 2.5 to 5 mg /kg, deep I/ M; Doubtful against erythrocytic stage.
• Oxytetracycline – 20 mg /kg for 7 days; I/M; effective against of schizogony.
• Halofuginone (stenorol) –  1 to 2 mg/kg as 2 doses, as tablets, Potent against schizont stage but toxic.
• Others- 3% Tryphan blue solution.

Prevention and control

• Chemoprophylaxis , Immunoprophylaxis  and Tick control.

(1) Chemoprophylaxis

• Long acting tetracycline two doses should be given intramuscularly.

(2) Immunoprophylaxis

• Vaccination of exotic and crossbred cattle with tissue culture vaccine (Rakshavac-T*)).
  • Rakshavac-T
    • It is a live schizont grown in lymphoblast cell culture attenuated by prolonged invitro passage.
    • Age of vaccination: 2 months and above.
    • Dose : 3.0 ml S/C.
    • Revaccination:  every three years.
• Infection and treatment method
  • Inoculation of ground up tick supernates (GUTS) into the disease free animal together with inj.  Oxytetracycline LA or inj. Buparvaquone.
  • It suppresses the development of the parasite and allow the effective CMI response with minimal disease response.
• Subunit vaccine and recombinant vaccine also available for vaccination.

(3) Vector control

• Wide spread and strict application of acaricides on the animal and farm premises.

East Coast Fever

East Coast Fever is caused by Theileria parva parasite.

Morphology

• Piroplasms in RBC mostly rod shaped, however round, oval, comma and ring shaped form may also occur.
• Several parasites may occur in individual RBC, but there is no evidence for multiplication of parasites in erythrocytes.
• The actively multiplying form schizonts (Koch blue bodies) occur in cytoplasm of lymphocytes and occasionally in the endothelial cells of lymph glands and spleen.
• The schizonts are circular or irregularly shaped.

Epidemiology

• The disease is mostly occur in East, Central and Southern Africa.
• ECF outbreaks occur mostly during rainy season (increased tick activity following onset of rainfall).
• ECF affect mainly cattle, but also buffaloe.

Life cycle

• Similar to T. annulata.

Pathogenesis

• similar to T. annulata.
• Note: Immunosuppression is more severe than T. annulata.

Clinical manifestation

• Incubation period- 10-25 days.

Acute form

• Most common.
• Fever (40-41.7⁰ c) depression, anorexia, drop in milk yield.
• Nasal and ocular discharge.
• Swelling of superficial lymph node.
• Swelling of eyelids and ears.
• Rapid heart beat.
• Diarrhoea, sometimes dysentry  may occur.
• Emaciation, weakness and recumbency.
• Pulmonary edema responsible for immediate cause of death.
• Death due to asphyxia.
• Occasionally, involvement of  brain  causes turning sickness, characterized by circling movement and abduction of hind limbs.
• Immunity is solid after recovery.

Sub acute form

• Frequent in calves but symptoms are less pronounced.

Necropsy Finding

• same as that of T. annulata.

Diagnosis

• Demonstration of Schizonts in lymph node biopsy.
• Demonstration of erythrocytic forms are difficult in blood smear.
• Differentiation from the Theileria spp is difficult.
• Serological tests: IHA, IFA, Capillary agglutination test are used to identify antibody.

Treatment

• Same as that of T.annulata.

Theileriosis of Sheep and Goats

• Theileriosis of Sheep and Goats is caused by T. hirci (T.lestoquardi) and T.ovis.
• T. hirci (T.lestoquardi )-highly pathogenic causes Malignant ovine theileriosis.
• T.ovis-mildly pathogenic causes benign ovine theileriosis.
• Morphology: Oval and rod shaped.
• Life cycle: Similar to cattle.
• Pathogenesis- Similar to Bovine Tropical theileriosis.

Clinical manifestation

• Acute: High fever, listlessness, nasal discharge, anaemia, jaundice, atony of rumen, weakness, transitory haemoglobinuria,  lung edema and  enlargement of lymph nodes.
• No cross immunity betweenT. hirci and T. ovis.

Necropsy Finding

• Petechial haemorrhage on abomasal mucosa, edematous lungs, haemorrhage in submucous, subserous and subcutaneous tissue.

Diagnosis

• Examination of stained smear of blood, lymph nodes or spleen.

Treatment

• Single dose of Buparvaquone @ 2.5 mg/ kg b.wt.