Cattle nematode - (Ostertagia ostertagi

• Ostertagia is a parasite (nematode ) that is also causes parasitic gastroenteritis in cattle
• the disease is called Bovine a ostertagiosis/PGE
• PGE-• Disease associated with a number of nematode species (singly or in combination)

  → ROUNDWORMS 

   • Characterised by: 

  • diarrhea / weight loss (clinical disease)

   • poor weight gain (subclinical disease)

   • seasonal appearance 

  • hypoalbuminemia
• PARASITIC GASTRO-ENTERITIS

   Economic importance 

  • Considerable economic importance in grazing livestock 

  • Potential welfare problem (esp. organic farms) 

  • Losses associated with the cost of:

   • replacement stock 

  • disruption of breeding programme 

  • impaired productivity 

  • treatment of clinically affected stock

   • prophylaxis
• what is the primary cause of PGE - ostertagia
• BOVINE OSTERTAGIOSIS

  caused by:  Ostertagia

  • PRIMARY pathogen of cattle (temperate regions) 

  • Adult worms 1cm long, cotton-like, brown (when fresh)

   •found in Abomasum of cattle
• life-cycle of nematode ostergia . adult is found in abomasum of cow both female and male mate > eggs are released via poo> hatch produce larvae L3 and eaten by another cow > into their abomasum and mucosa and infected . 3 weeks prepatent period > time of infection to eggs in theor poo
• 1st stage : typical strongyle egg from ostergia and will have an oval shape and thin shell. 3rd stage : go onto L3 larvae stage more visible to naked eye and lives 9-10months in pasture and larvae live sin water droplets and the gets ingested by another cow and take 2-3weeks to develop in adult in gastric gland
• larva stage 4 : 1mm long in gastric gland and then adult worm 1cm
• risk of disease = rate of infection + host immunity
• 
  

   RATE OF INFECTION depends on:

   • Host appetite - cow that eat

  • NUMBERS OF INFECTIVE LARVAE (L3) ON PASTURE/grass
• times which larvae high in pasture - 1. august to winter and 2. from january until spring

  A) risk to grazing animals outside

  B) Risk to Housed animals for winter

  
• → Disease commonest in calves at

  • grazing permanent pasture

   • kept at high stocking density
• whys we see disease at a particular time of year.L3 causes disease.

  1. permanent pasture grazed by cattle last year
  2. LARVEA ON PASTURE FROM LAST YEAR
  3. overwinter L3 good at surviving winter.dont feed, have food reserve
  4. as weather warms up , slowly decline due to lost of food reserves
  5. then cattle turnout - ( cows leave their houses )
  6. pick up/ eat infected larvae
  7. after 3 weeks eggs appear=in their poo
  8. the time for egg to hatch gets shorter as we reach summer
  9. due to higher temperature
  10. all reach L3 same time and then a sudden increase in larvea on pasture = summer ostertagiasis

  
• WINTER OSTERTAGIA - This is the autumn infection peak. From the previous graph.last part of the grazing season here, September, October, November time.what happens if calves are left to graze heavily contaminated pasture.

  1. instead of developing adult worms in 3 weeks they pop into the gastric glands eat and then go to sleep
  2. This is due to cooler temperatures
  3. they come arrested for months at L4 in abomasal mucosa
  4. cattle accumulates a lot of larvae 500K
  5. no clinical symptoms

  
• Let's see what happens to the parasite if the larvae don't become arrested.

  • If not arrested, larvae would reach the adult worm stage in L3 w
  • Eggs would appear on pasture during cold weather
  • Eggs are less resilient in cold conditions compared to infective larvae
  • Many eggs would die off in cold weather
  • Killing off all the eggs could eliminate larvae on the pasture
• Where larvae become arrested when the L3 are eaten late in the autumn

  • Around end of January, approximately 20% of arrested worms resume development
  • Resumed development leads to the adult stage three weeks later, causing clinical signs
  • Clinical signs appear only when worms reach the adult stage
  • Following this, another 20% of arrested worms resume development a couple of weeks later
  • Strategy of staggered development to avoid putting all eggs in the same basket
  • Aim is to synchronize the waves of infection with periods of favorable weather- for parasite to survive
• what triggers Larvae L4 to stop developing and become arrested .

  1. it's prolonged chilling of the same larvae on the grass late in the autumn causes them to become arrested once they're eaten.
  2. Those same larvae on the grass if they're not eaten by calves
  3. will survive through to the following year when they're eaten by next year's calves after turnout.
  4. Tendency to arrested development induced by chilling is turned off by the following spring
  5. Short chilling induces arrested development, but prolonged chilling turns it off.
•  Immunity to Ostertagia ostertagi

   • SLOW to develop (whole grazing season) 

  • May FALL over winter

   - RE-ESTABLISHED upon turnout (2nd grazing season)

   • ADULT cattle solidly IMMUNE (no significant role in disease epidemiology)
• CONTROL (TYPE 1 DISEASE) we prevent summer or type one 

  Use clean pasture 

  • New leys, pasture not grazed by cattle last year 

  • BUT not always available
• Delay turnout until after spring mortality in L3

  • BUT uneconomical use of pasture, supplementary feeding
• DOSE ‘N’ MOVE - MID-JULY

  • Most overwinter larvae die by early summer
  • Late summer peak of infection
  • late summer august type 1 ostertagiasis
  • Dose and move system involves using a second field for silage production in the first half of the year
  • Cattle are dosed mid july with a wormer and then moved to field B for the rest of the year
  • This system avoids exposing calves to the significant autumn infection peak
  • BUT will not control early season disease 

  • Increased anthelmintic resistance risk?

  → aftermath, that is merely a field that was used that was cut for hay or silage reduction.

  
• IF NO ALTERNATIVE GRAZING AVAILABLE

  Strategic anthelmintic treatment
• Strategic anthelmintic treatment

  1. Traditional treatments every 3-4 weeks didn't reduce grass larvae.
  2. Doramectin, a modern anthelmintic, used for its lasting effects.
  3. Two doses: one at turnout, another 8 weeks later.
  4. First dose protects for 5 weeks,preventing larvae from establishing and transmission
  5. second dose lasts up to 13 weeks.prevents larvae from becoming egg-laying adults at this crucial stage
  6. Prevents contamination of pasture by targeting larvae and overwinter larvae die off.
• • intraruminal anthelmintic devices like Autoworm minimize pasture contamination.
  • Administered using a bolus gun, the device sits in the reticular rumen and slowly releases deworming drug.
  • Provides protection for several months, either intermittently or continuously.
  • Stops pasture contamination with worm eggs and eliminates autoinfection peak.So that will stop any of the overwinter larvae that are ingested here from growing to adult worms.

  → Therefore no contamination and therefore no auto infection peak.
• type two Cattle exposed to MEDIUM / HIGH challenge at pasture in late autumn or cattle of UNKNOWN origin

   • LIKELY to require treatment at housing