Mahatma Jyotiba Fule College of Veterinary And Animal Sciences, Jaipur (Raj)

Topic – Theileria

Presented by :-Dr. Abhinav Meena

2020-2021Assistant Professor

Department of Veterinary ParasitologyCollege of Veterinary and Animal Sciences,

Chomu , Jaipur (Raj)

GENUS - THEILERIA

Brief introduction:-

These are tick - transmitted haemoprotozoan parasites

occurring particularly in the RBC and Iymphocyte.

The disease caused by the protozoa is bovine tropical

theileriosis, east coast fever and corridor disease etc.

Prevalence:-

This protozoa is cosmopolitan in distribution.

Family - Theileriidae

Genus - Theileria

Species:-

T. annulata (causative agent of bovine tropicaltheileriosis) – found in cattle.

T. parva (causative agent of East coast fever) –found in cattle.

T. lawrenci (causative agent of corridor disease) –found in cattle.

T. hirci - found in sheep and goats.

T. ovis - found in sheep and goats.

Salient morphology:-

In RBC

Small dot-like.

Comma –shaped.

Round and ring form.

In lymphocytes

The organisms appear in the Iymphocyte as schizont

form which are called Koch's blue bodies.

In the cytoplasm of the Iymphocyte the organisms

divide. Few or more number of organisms are found in

it. This is the confirmatory diagnostic feature during

examination of blood smear.

Life cycle:-

Developmental stages

• Schizonts in the Iymphocyte (Macroschizonts and

microschizonts).

• Merozoites.

• Round and elongated bodies.

• Ookinete.

Description:-

1. During blood meal, the sporozoites enter the host and reachthe lymph node.

2. In the lymphocytes the organisms multiply and form theschizonts. Two types of schizonts develop like macro andmicroschizonts. In the lymphocytes few or more number oforganisms are produced. These organisms are mainly found inthe cytoplasmic space of the lymphocytes. Since themicroschizonts appear Simultaneously with piroplasms inR.B.C., it is considered that the piroplasmic forms are derivedfrom microschizonts and enlargement of prescapular lymphnode.

3. The organisms are transmitted to the vector larvaeor nymph of 3 host vector when the vectors takeblood meal. It is to be kept in mind that the organismsare transmitted to the vector through R. B. C. and notby the lymphocytes. It means that the organismsfound in the R. B. C. develop to the infective stages inthe vector.

4. In the tick the organisms differentiate into twoforms, round and elongated representing macro andmicrogamonts respectively .

5. Due to union of these two forms, zygote is formedwhich are called as the ookinete. The ookinete reachthe salivary gland and develop to become sporoblastand infective sporozoites are formed when next stageof tick starts feeding.

6. When the tick takes the blood meal, the organismsare transmitted to the hosts.

Note : Transmission is transtadial, not transovarian.

Pathogeneity:-

Pathological features / lesions

Anaemia.

Spleenomegaly.

Hepatomegaly.

Neuropathology.

Description:-

The organisms cause marked pathogenicity which may even

lead to mortality. Acute status of the disease is commonly

occurred.

The phase of the disease may be as prolonged as up to 4 weeks

or more. During this period several characteristic clinical

features occur.

Of these clinical features the most important clinical sign having

Significant diagnostic importance is enlargement of prescapular

lymphnode.

High rise of temperature(40-41. 5°C) is another associated sign.

Necropsy findings depict petecheal haemorrhage in the G. I.

tract which comprises ulceration in the abomasal wall and

intestinal wall. This ulcer is called as punched-out ulcer.

Haemorrhages are also found in other organs like kidney.

Clinical signs:-

1.High rise of temperature and enlargement of prescapular

lymph node.

2. Unwillingness to feed and drink water.

3. Dullness and depression.

4. Lacrimation from the eyes.

5. Haemorrhagic diarrhea.

6.Turning sickness which is characterized by circling

movements due to occurrence of necrosis of brain is a typical

sign found in T. parva and T. mutans infection.

Diagnosis:-

1.Examination of thin and thick blood smear.

2.Examination of wet blood smear - Described earlier In the

Babesia infection.

3. Common immunological tests;

a.LAT(Latex Agglutination Test)

b.FAT(Flurescent Antibody Test)

c.ELISA (Enzyme Linked Immunosorbent Assay)

d.DOT -ELISA

Recent trends:-

Immunodignosis:-

Immunodiagnosis is done by different types of ELISA using;

a. Native purified antigen

b. Recombinant antigen

Molecular diagnosis

Molecular diagnosis is done by PCR, RAPD -PCR, RFLP-PCR

Immunity to Theileria spp:-

1.The animals which suffered from the disease show certain levelof immunity. This immunity does not depend upon the presenceof the organisms.

2.Schizonts stages are found to be mostly immunogenic.Considering this ground schizont culture vaccine was started.

3.Occasionally the immunity occurring in animal does not remainfor long period which wanes after several months.

4. Cytotoxic T cells plays a great role in immunity. These cytotoxicT cells kill the infected lymphoblasts.

Treatment:-

1. Chlortetracycline.

2. Buparvaquone.

3. Halofuginone.

4. Menoctone.

Control:-

1.Chemotherapy -The affected animals are treated

properly.

2.The animals should not be allowed to graze on the

infected pasture.

3.The ticks can be mechanically removed.

4.Vaccination.

Earlier attempts:-

a. Live vaccine - Efforts have been made to immune the animals

by transfer of infected blood.

b. Attenuated vaccine - The most suitable vaccine used so far

against Theileria spp is the macroschizont culture vaccine.

Schizont infected lymphocytes are cultured, attenuated and

used as vaccine. Rakshavac -T is the schizont culture vaccine

used in India.

Recent trends:-

a.Anti-idiotype vaccine (Anti- T. sergenti antibody by

inoculation of murine monoclonal anti - idiotype

vaccine).

b.Recombinant vaccine - The specific

immunodominant protein (Ex NS 1 - P67, 67 kDa

sporozoite surface protein) is expressed in expression

vector and used as vaccine.

c. Antivector vaccine - Recent trend has been pinpointed

towards the production of vaccine against the vector. Bm 86 has

been found to be an immunodominant concealed antigen of

Boophilus microplus which ,is expressed in Escherechia coli and

Pichia pastoris and resulted TickGard and Gavac vaccine. Other

immunodominant antigens are Bm 91 and BMA 7.

d. Nacked DNA vaccine - Significant protection was achieved

against T. annulata by injecting plasmid DNA encoding allergic

forms of T. annulata, Tarns-l and Tarns -2 merozoite surface

antigen and Spag-1 (Sporozoite surface antigen).

Thank You