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Created page with '=== Haemonchosis === *''Haemonchus contortus'' (abomasum) **2cm long,'''barber's pole''' appearance when fresh **Primarily a tropical/sub-tropical parasite, although may cause pr…'
=== Haemonchosis ===
*''Haemonchus contortus'' (abomasum)
**2cm long,'''barber's pole''' appearance when fresh
**Primarily a tropical/sub-tropical parasite, although may cause problems in the UK (was restricted to SE England but has spread north to Scotland due to warmer, wetter winters in recent years)
**Blood-sucking nematode (piercing "lancet" in buccal capsule of L4 and adult worms)
==== Epidemiology of Haemonchosis ====
*''Haemonchus'' has a high biotic potential, egg to L3 development occurs very fast in hot humid conditions
'''Tropical and Subtropical Areas'''
*Disease outbreaks depend on local rainfall
*Parasite survives prolonged dry periods by arrested development
*Development resumed just prior to rainy season e.g. Australia, Brazil, Middle East and Nigeria
*Arrested development less common in areas with more frequent rainfall e.g. East Africa
*Several cycles of infection annually
'''Temperate Areas''' (less favourable for ''Haemonchus'' L3 survival)
*Ewe is primary source of infection (relatively few L3 overwinter on pasture)
*Eggs hatch and develop to L3
*Most L3 ingested by ewes and lambs in late summer become arrested (EL4, abomasal wall) → resume development following spring → acute haemonchosis (epidemiology equivalent to type 2 ostertagiosis)
*A few L3 ingested by lambs do not become arrested → acute haemonchosis (if sufficient L3 ingested; equivalent to Type 1 ostertagiosis)
*This is most likely to happen in hot thundery summer periods
*Normally, only one cycle of infection annually
==== Pathogenesis of Haemonchosis ====
*Moderate infection (2000 worms) leads to
**Increased red blood cell turnover (from 4 months to 3 weeks)
**Loss of haemoglobin and iron (normally recycled)
**Depleted iron reserves leading to anaemia and death
==== Forms of Haemonchosis ====
*'''Hyperacute''' (0-7 days)
**Sudden death in apparently healthy sheep;
**Severe anaemia (tropics mainly)
*'''Acute''' (1-6 weeks)
**Oedema, loss of condition, lethargy, death
**Anaemia, hypoalbuminaemia
*'''Chronic''' (2+ months)
**Progressive weight loss or reduced weight gain
**Similar appearance to poor nutrition
==== Diagnosis of Haemonchosis ====
*Clinical signs (anaemia)
*Season
*Faecal egg count (may be very high)
*Low blood haemoglobin, PCV and red blood cell count
*Elevated blood pepsinogen
*Post-mortem examination:
**>2000 adult worms
**Numerous haemorrhagic lesions on gastric mucosa
**Brown fluid in abomasum
**Pale oedematous carcass
**Expansion of red marrow from epiphysis into medullary cavity of long bones
[[Category:Sheep_Nematodes]][[Category:Trichostrongyloidea]]
*''Haemonchus contortus'' (abomasum)
**2cm long,'''barber's pole''' appearance when fresh
**Primarily a tropical/sub-tropical parasite, although may cause problems in the UK (was restricted to SE England but has spread north to Scotland due to warmer, wetter winters in recent years)
**Blood-sucking nematode (piercing "lancet" in buccal capsule of L4 and adult worms)
==== Epidemiology of Haemonchosis ====
*''Haemonchus'' has a high biotic potential, egg to L3 development occurs very fast in hot humid conditions
'''Tropical and Subtropical Areas'''
*Disease outbreaks depend on local rainfall
*Parasite survives prolonged dry periods by arrested development
*Development resumed just prior to rainy season e.g. Australia, Brazil, Middle East and Nigeria
*Arrested development less common in areas with more frequent rainfall e.g. East Africa
*Several cycles of infection annually
'''Temperate Areas''' (less favourable for ''Haemonchus'' L3 survival)
*Ewe is primary source of infection (relatively few L3 overwinter on pasture)
*Eggs hatch and develop to L3
*Most L3 ingested by ewes and lambs in late summer become arrested (EL4, abomasal wall) → resume development following spring → acute haemonchosis (epidemiology equivalent to type 2 ostertagiosis)
*A few L3 ingested by lambs do not become arrested → acute haemonchosis (if sufficient L3 ingested; equivalent to Type 1 ostertagiosis)
*This is most likely to happen in hot thundery summer periods
*Normally, only one cycle of infection annually
==== Pathogenesis of Haemonchosis ====
*Moderate infection (2000 worms) leads to
**Increased red blood cell turnover (from 4 months to 3 weeks)
**Loss of haemoglobin and iron (normally recycled)
**Depleted iron reserves leading to anaemia and death
==== Forms of Haemonchosis ====
*'''Hyperacute''' (0-7 days)
**Sudden death in apparently healthy sheep;
**Severe anaemia (tropics mainly)
*'''Acute''' (1-6 weeks)
**Oedema, loss of condition, lethargy, death
**Anaemia, hypoalbuminaemia
*'''Chronic''' (2+ months)
**Progressive weight loss or reduced weight gain
**Similar appearance to poor nutrition
==== Diagnosis of Haemonchosis ====
*Clinical signs (anaemia)
*Season
*Faecal egg count (may be very high)
*Low blood haemoglobin, PCV and red blood cell count
*Elevated blood pepsinogen
*Post-mortem examination:
**>2000 adult worms
**Numerous haemorrhagic lesions on gastric mucosa
**Brown fluid in abomasum
**Pale oedematous carcass
**Expansion of red marrow from epiphysis into medullary cavity of long bones
[[Category:Sheep_Nematodes]][[Category:Trichostrongyloidea]]