Ovine haemonchosis

Ovine haemonchosis:

·         Pathogenesis of Haemonchosis is an acute haemorrahgic anemia due to blood sucking habit of       worms.

·         Each worm removes about 0.05ml of blood per day by ingestion and seepage (Leakage) forms the       lesions.

·         A sheep with 5000 H. contortus may lose about 250 ml blood daily.

·         In hyperacute Haemonchosis:

o   In heavier infection (up to 30,000 worms), the ewe will die suddenly from severe hemorrhagic gastritis.

·         In acute Haemonchosis:

o   Anaemia becomes apparent about two weeks of infections and is characterized by progressive and dramatic packed cell volume.

o   Continuous loss of iron and protein into gastrointestinal tract, the marrow eventually becomes exhausted.

o   When ewes are affected, the consequent agalactia may result in the death of the sucking lambs

o   At Necropsy:

§  2000 to 20,000 worms may be present on abomasal mucosa which show numerous small hemorrhagic spots.

§  The abomasal content is fluidy and dark brown due to the present altered blood

§  The carcass is pale and oedematous due to hypoprotenemia

§  The red marrow has expanded form the epiphyses into medullary cavity.

·         Chronic Haemonchosis:

o   Prolong dry season when reinfection is negligible but pasture becomes deficient in nutrient

o   Over such a period, continual loss of blood from intestine by several hundreds of worms

o   Associated with loss of weight, weakness and inappetence rather than marked anemia

Clinical Signs:

·   Hyper acute case:

·   Sheep die suddenly from hemorrhagic gastritis

·   Acute case: Characterized by-

·   Anaemia

·   Variable degree of oedema (Submandibular oedema and ascitis is more common)

·   Lethargy, Falling wool

·   Dark colored feces

·   Diarrhea is not general feature

·   Chronic case:

·   Progressive weight loss and weakness

·   Neither severe anaemia nor gross oedema is found

Diagnosis:

·   Clinical History:

·         Epidemiology:

o      Haemonchus contortus is distributed in tropical, sub tropical or in temperate areas.

o      Haemonchosis occurs optimally at relatively high temperature/ warm climate

o      High humidity is required for larval development in faeces

o      Immuned sheep always contaminate the pasture i.e acts as carried

o      The infective larvae are relatively resistant to desiccation and may survive for 1-3 months on pasture or in feces

o      Hypobiosis occurs in prolong dry period (L₄)

o      Frequent rainfall, no hypobiosis

Clinical Signs: Already mentionded

Coproscopy with fecal egg count:

·         Characteristic egg under microscope

·         High fecal worm egg count (2000-20,000) indicate the acute haemonchosis

Necropsy findings: Already mentioned

Treatment:

·         Benzimidazoles/Levamisole/Avermectin

·         Move to safe pasture

 Control: See GeNeral Control Measures for Nematodes

Note : Caprine or Bovine Haemonchosis: Similar to ovine haemonchosis