integrated parasite management sdl

case 1

It is September and you are preparing a flock health plan for a commercial upland flock of 1200 ewes lambing outside in March-April on an 800 acre farm. The grazing is relatively dry and some of the land is used each year for baled silage.

List the common GI nematodes and trematodes that are potentially important for the lambs in this system and for each one suggest a way to monitor for the parasite

• nematodirus battus→ use parasite forecasts and grazing history of pasture to determine treatment requirements.

• teladorsagia (ostertagi) circumcincta→ carry out WECs and monitor DLWG throughout grazing season.

• trichstrongylus spp. → carry out WECs and monitor DLWG throughout grazing season.

• haemonchus contortus → carry out WECs (speciation is also useful) and monitor for anaemia using FAMACHA scoring.

case 1

Prior to the visit the farmer calls you with some lamb weight data. The mean DLWG for the group was 174g (post-weaning growth rate target >200g/day). What reasons might result in lambs not achieving their target growth rate?

What could you do to investigate this further?

• Poor ewe condition affecting milk production

• Poor forage/nutrition quality

• Parasitism

  
  

• Check ewe body condition score (BCS)

• Assess forage availability and any supplementary nutrition provided

• Ask about worming history and collect faecal samples for a worm egg count

  
  

what can affect pre weaning growth rates

• impacted on by ewe condition affecting milk production

• forage supply

• The stress of weaning may impact on growth rates particularly if lambs have not transitioned well.

case 1

You decide to do a worm egg count (WEC) and the result is 500epg (eggs per gram). The farmer is surprised as the lambs have been wormed recently with a Benzimidazole product (A group 1 / white drench). What questions might you ask the farmer and how would you investigate this?

• when were they put onto the pasture

• has this pasture had flocks which had worms on previously

• has this been an issue previously

• You would want to check previous worming protocols including dose rate, frequency of use, worming gun calibration (is the gun dispensing the correct volume), storage and expiry date of wormer.

• There may be some Benzimidazole resistance, so you could do a Faecal Egg Count Reduction Test (FECRT) to assess this.

case 1

Based on the system, what suggestions could you make to the farmer that may reduce their anthelmintic requirements going forward?

• only worm a selective group of flock

• delay putting out to pasture

• Carry out WECs in lambs every 3 weeks during the grazing period, monitor DLWG and only worm when required.

• Putting lambs on pasture that didn’t have lambs on the previous year (ideally 2 years if possible) can reduce requirements for Nematodirus battus treatments.

• Post-weaning, put lambs on ‘low-risk’ pasture, such as silage aftermath.

  
  

case 2

The following day you are completing a herd and flock heath plan for a lowland sheep and beef farm with 400 ewes and 50 suckler cows & their calves grazing 200 acres of permanent pasture, floodplain meadows and reseeded grass leys. The sheep lamb indoors in February and the cattle calve in the autumn and are housed over winter.

How is this system similar and different to the system in case 1, and what are the implications for parasite control?

• The sheep lamb earlier and inside but are still likely to be at risk of Nematodirus when turned out (depending on hatch times)

• Having cattle on the farm may allow incorporation of co-grazing or ‘lead-follower’ systems to reduce parasite burdens

  • other infectious diseases that can pass from cattle to sheep should be considered here too though

• Floodplain meadows may provide mud snail habitat so liver fluke may be a risk on this farm.

• Reseeded grass leys offer low risk pasture for high-risk animals.

case 2

Suggest a parasite management plan (for nematodes and trematodes) for the cattle and sheep. Consider the likely parasites

sheep

• nematodirus battus

• haemonchus contortus

• teladorsagia

• trichostrongylus

cattle

• ostertagia ostertagi

• cooperia

both

• fasciola hepatica

case 2

how can the parasites be monitored on this farm for sheep

sheep

• nematodirus battus→ Monitor parasite forecast for area and consider pasture grazing history

• haemonchus contortus→ Monitor WECs every 3-4 weeks throughout the grazing season. Monitor DLWG (if data available)

• teladorsagia→ Monitor WECs every 3-4 weeks throughout the grazing season. Monitor DLWG (if data available)

• trichostrongylus → Monitor WECs (including speciation if suspicious of Haemonchus) and use FAMACH scoring for anaemia

• fasciola hepatica → Monitor for exposure using serology or faecal coproantigen.

case 2

how can the parasites be monitored on this farm for cattle

cattle

• ostertagia ostertagi→ Monitor WECs every 3-4 weeks throughout the grazing season. Monitor DLWG (if data available)

• cooperia → Monitor WECs every 3-4 weeks throughout the grazing season. Monitor DLWG (if data available)

• fasciola hepatica → Monitor for exposure using serology or faecal coproantigen.

case 2

how can the parasites be controlled on this farm for sheep

sheep

• nematodirus battus→ At risk groups should be treated with a Benzimidazole product (Group 1 / white drench)

• haemonchus contortus→ Worm as required. Aim to leave at least 10% of the best growing lambs in a group untreated and if moving to clean pasture post-treatment delay by 3-7 days

• teladorsagia→ Worm as required. Aim to leave at least 10% of the best growing lambs in a group untreated and if moving to clean pasture post-treatment delay by 3-7 days

• trichostrongylus → Worm as required. Closantel is narrow spectrum so may be used if just treating Haemonchus

• fasciola hepatica → Avoid high-risk (wet) areas at high-risk times (late summer-early autumn)

case 2

how can the parasites be controlled on this farm for cattle

cattle

• ostertagia ostertagi→ Worm as required. Aim to leave at least 10% of the best growing calves in a group untreated and if moving to clean pasture post-treatment delay by 3-7 days

• cooperia →Worm as required. Aim to leave at least 10% of the best growing calves in a group untreated and if moving to clean pasture post-treatment delay by 3-7 days

• fasciola hepatica → Avoid high-risk (wet) areas at high-risk times (late summer-early autumn)

case 3

It is February and you are called out to new client who has set up a beef rearing unit. The farmer buys weaned beefXdairy calves to rear and sell as store cattle

The farmer reports 5 of a group of 15 yearling animals suddenly developed a profuse diarrhoea, one has died and the other four are rapidly losing weight and appear clinically ill

The heifers were born early in the spring in the previous year and spent the summer grazing, they are currently housed

List your differential diagnoses for diarrhoea in a group of housed yearling cattle. Consider parasitic and non-parasitic causes of diarrhoea.

• Type 2 ostertagiosis

• Salmonellosis

• BVD

• Fascioliasis

• Coccidiosis (eimeria)

• cryptosporidium

• Cereal overeating/carbohydrate overload

• Winter dysentery (Bovine Coronavirus)

case 3

What questions might you ask the farmer to help determine which of these differentials are more likely?

Were they wormed/faecal worm egg counts checked at housing?

Where were the cattle grazed prior to housing

Are there any recent dietary changes/what are the cattle fed

Are there any other signs of disease (pyrexia, bloat, anaemia etc.)

What diagnostic tests could you use to rule in/out type 2 Ostertagiosis? (consider what stage of the lifecycle the parasites will be at)

In type 2 disease, clinical signs are caused by emergence of hypobiosed larvae, so egg counts can be variable or 0.

Elevated pepsinogen and low albumin can be indicative of type 2 ostertagiosis.

You blood sampled the affected cattle and found that they had markedly decreased albumin and elevated blood pepsinogen

You are now strongly suspicious of type 2 ostertagiosis

What treatment do you give the affected cattle?

What is the prognosis?

• Macrocyclic lactones (group 3/clear wormers) are effective against hypobiosed larvae and are appropriate to use for type 2 ostertagiosis → ivermectin.

• Supportive therapy such as antiinflammatories and fluids/electrolytes are also often indicated.

• Prognosis for these cases is guarded.

A further two heifers die despite your treatment with Ivermectin. Develop a parasite control plan to reduce the risk of disease occurring again next year (consider anthelmintic use and management changes)

• Monitor parasitism over the grazing period by doing WECs every 3-4 weeks.

• Dry summers and wet autumns can cause high levels of parasitism at the end of the grazing season and predispose to type 2 disease.

• Use of low-risk pasture later in the grazing period (e.g. hay/silage aftermath) can reduce the risk.

• Worming with a Macrocyclic lactone at housing in high risk years should prevent type 2 ostertagisosis.