Author: sarah.sandhu@airr.com.au

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MONITORING FOR WORMS

The signs of worm infection in sheep often go unnoticed until the problem becomes severe.  As you can see in figure 1, by the time the signs of worms (clinical effects) the producer has experienced significant losses in productivity and breaks in wool.

EWES

Around the time of lambing, ewes lose their acquired resistance to worms.  This occurs from 2-4 weeks before lambing to 4 to 9 weeks after lambing, but may persist up to 14 weeks or more in individual ewes.  This is brought on by the metabolic demands of the foetus and lactation and is not thought to be caused by the priority of the ewe to sustain the pregnancy and produce milk, which calls for preferential partitioning of protein. This phenomenon is called ‘periparturient relaxation of resistance’ or PPRR.

Because of their high egg output, lambing and lactating ewes require special attention given to their worm control.  Many producers drench ewes with a long-acting drench one month before lambing commences. This is a good strategy to prevent pasture larval contamination, particularly when there is already contaminated pasture due to long grass, rain and cool weather. These conditions favour larval survival and will allow a build-up of larval numbers on pasture to dangerous levels.

LAMBS AND WEANERS

Lambs are born without any immunity (resistance) to internal parasites, but begin to develop immunity usually after they are weaned.  When young sheep are exposed to internal parasites for about four months, it leads to ‘acquired resistance’.  Resistance to parasites develops slowly for Black Scour Worm and Small Brown Stomach Worm (8-15 months of age), while resistance to Barber’s Pole Worm may develop at younger ages.

Weaners are the most vulnerable group of animals, as they have the highest susceptibility to internal parasites as:

  • They have not yet developed immunity to parasites.
  • Due to their transition from mothers milk to pasture they may suffer nutritional deficiencies.
  • Many weaners have low weaning weight (e.g. Merino weaners under 25kg) and therefore have few body reserves.  They struggle to mobilise sufficient energy to fight off worm infestations.
  • Worms cause a direct lowering of appetite of infected

he best ways of preparing low contamination pastures are by:

  • Spelling pasture over summer. Removing stock for 3 months over a dry, hot summer removes over 90% of worm larvae.
  • Grazing with cattle, then allowing re-growth of pasture.
  • Grazing with dry adult sheep.  This is especially effective if the sheep are treated with a long-acting injection or a bolus prior to introduction
  • Cutting hay from paddock, then spelling for a few months.  Opening up the sward exposes worm larvae to sunlight, which kills a high percentage of them.
  • Ploughing the paddock and growing a crop
  • Burning the grass and encouraging new growth.
  • Using crop stubble (with supplements).
  • Feedlotting lambs are free from reinfection

Survival of barber’s pole worm infective larvae on pasture at various daily maximum temperatures and 60% relative humidity

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MUD FEVER IN HORSES – THE CAUSE, SYMPTOMS AND MANAGEMENT

WHAT IS MUD FEVER?
Mud fever, also referred to as scratches, greasy heel, or pastern dermatitis, describes an inflammatory and often painful condition that usually affects the lower limb region of horses.

It is likely to develop during particular times of the year or during certain weather events; more commonly seen during periods of wet weather where the horse is exposed to waterlogged soil and muddy surfaces, as well as damp pasture and bedding, for prolonged periods of time.

SIGNS & SYMPTOMS OF MUD FEVER
Equestology Sport Horse Science (2018, para. 2) writes that “clinical signs can range from inflammation, hair loss, scabs, cracked and ulcerated skin, to granulation tissue, discharge and generalised swelling of the lower limbs and associated lameness.”

Visible symptoms of mud fever may be similar to other skin conditions caused by allergies which can result in a misdiagnosis, highlighting the importance of performing a thorough examination of both the horse and the surrounding environment.

Horses with non-pigmented skin, such as those with white ‘socks’ on their legs, and horses that have feathering at the fetlocks, appear to be the most commonly affected when it comes to mud fever (Canberra Equine Hospital 2020).

The long and thick fetlock hair generally seen in heavy breeds can hold moisture and keep the skin damp which reduces skin integrity and provides an opportunity for bacteria and fungi to accumulate and take hold.

The pathogens that are most commonly linked to the development of mud fever in horses include bacteria such as Staphylococcal spp. And Dermatophilus Congolensis, moulds and fungi that produce toxins called Mycotoxins, and organisms such as mites which are more commonly seen in feathered breeds such as Clydesdales and Friesians (Equestology Sport Horse Science 2018).

Mycotoxins are a particularly common cause of mud fever in horses when they are housed in hot, humid, or moist climates; which are the optimal habitat for Mycotoxins to thrive.

Mycotoxins binders (such as those found in CEN XtraBalance) can be extremely useful dietary additives to alleviate the symptoms of Mycotoxicosis. Less common causes of mud fever include fungal infections of the skin such as Dermatophytosis, worm larvae infestations, vasculitis, liver disease, pemphigus foliaceous, and coronary band abnormalities (Equestology Sport Horse Science 2018).