Animal Health May Update 🐄🐏

By Ash Halligan, District Vet

Case History

300 crossbred 12 to 24 month old home-bred wether lambs, were placed into containment lot paddocks with access to sheep pellets across two feeders and roughage in the form of hay. They had been fed this way for approximately 6-7 weeks prior to deaths occurring. They had access to mineral lick blocks for the past 1-2 weeks. There was a new batch of pellets being given approximately 2 weeks prior. The wethers were drenched on entry to the containment lot and were all in good BCS.

On presentation, about 10 wethers had died, with more looking unwell.

Clinical signs, post-mortem and diagnosis

The wethers were examined in yards, and those affected appeared dull (some were head pressing), reluctant to move or walking with a stilted gait, kicking at their abdomen, teeth-grinding, and standing in a stretched-out position. One was observed to have a prolapsed rectum (indicating straining). The majority of those affected had a large bulge on the underside of the abdomen or were distended in the abdomen.

Post-mortem revealed large quantities of fluid in the subcutaneous tissues underlying the lowest area of the abdomen (Image 1) and surrounding the prepuce and penis. The fluid gives this disease its common name of ‘water belly’ and is in fact urine. The bladder in this case was likely ruptured as it was empty, and it was blue-purple on its exterior (Image 2) with extensive haemorrhages on the interior surface (Image 3). There were moderate amounts of sandy/ gritty material sitting in the neck of the bladder. The kidneys also had multiple spots of haemorrhage (Image 4). There were multiple small, hard, discrete stones palpable bilaterally in both ureters just prior to entering the bladder.

Image 1: Tissues under the skin (subcutaneous space) where fluid was present

In this case, the mob of wethers were suffering from an obstruction of the urethra and/ or the ureters by stones called uroliths or calculi, therefore suffering a disease known as urolithiasis. When the bladder becomes so distended from the blockage, it will rupture causing urine to spill into the abdomen and result in the condition commonly known as water belly.

Due to perforation of the urethra, there was significant leakage of urine around the prepuce of many of these wethers, creating a large bulge over the underside of the sheep’s abdomen (Image 5). In some animals this was severe enough to cause pooling of urine down the hindlimbs also (Image 6).

Image 5: Urine pooling of ventral abdomen

Image 6: Swelling and pooling of urine in the hindlimbs

Urolithiasis, or water belly, is primarily a nutritional disease.

There are multiple factors that contribute. These include:

What can be done to prevent this?

Individual assessment of each animal provides the opportunity to identify those animals which have uroperitoneum (urine in the abdominal cavity), those with urethral rupture and those where immediate euthanasia is the best course of treatment. Euthanasia and post-mortem also allow for the collection of calculi for later determination of their chemical content (however not always possible) — information which is helpful in understanding the cause of the outbreak.

In this case, it is likely that the calculi have occurred due to being on cereal pellet diets. Therefore, adding calcium carbonate or legume hay to the diet, changing the diet completely, acidifying the urine or any strategies to increase urine flow may reduce the continuing incidence of obstruction in the flock at risk.

The following are strategies that will generally assist in prevention of water belly in your stock:

Ensure a calcium-to-phosphorus ratio of about 2:1.
Increase water intake by providing clean, good-quality water and good-quality roughage.
Include limestone at 1.5% of the diet in a feedlot. Alternatively, providing a loose lick of 50 per cent salt and 50 per cent lime ad-lib is an easy option. Salt not only acts as an attractant but can increase water consumption, helping to flush the bladder out.
Add ammonium chloride to the diet to act as a urinary pH acidifier, to reduce the conditions favourable for the formation of urinary calculi. As a preventive treatment ammonium chloride should be included in the diet at the rate of 0.5-1.5% of the feed. However, they cannot stay on ammonium chloride supplement for many continuous weeks otherwise they will be predisposed to other conditions.

If the blockage is in the urethral process in sheep and goats, amputation of the blocked tip of the process with scissors may resolve the condition. When dealing with animals of relatively high value, more complex medical or surgical procedures can be considered.

The formation of calculi occurs also in ewes but, because of their short, wide urethra, obstruction rarely occurs.

If you suspect urolithiasis, contact your local district veterinarian and they will be able to discuss treatment further with you.

Additional links
Veterinary Handbook

By Bianca Garnham, District Vet

Current wet autumn conditions have seen numerous calls to District Veterinarians about sheep feet. Some are panicked, some are resigned, some are reluctant – all are concerned that their sheep have lameness, or an abnormal appearance of feet that might signal an outbreak of footrot.

A lot of misconceptions exist about this disease, and the following is intended to serve as an overview of what to look for and give a better idea of the different causes of foot disease. For more detailed information, there are several links provided at the end.

Foot lesions

“I heard the vet talking about a lesion... what exactly does that mean?”

A “lesion” in this instance is simply a disruption to the skin or hoof of the foot that shouldn’t be there. All can cause lameness, not all are virulent footrot. You might also hear about lesion or foot “scores” – this is a method of assessing the likelihood that virulent footrot is present (see links for further description and pictures).

What exactly is “footrot”?

Essentially, it is caused by a bacterial infection (Dichelobacter nodosus) that eats through the tissue that joins the hoof to the foot (known as “underrunning”). This bacteria has multiple different strains – some have potential to cause severe disease and are classed as “virulent”, while others generally cause much milder signs and are classed as “benign.”

These bacteria enter clean flocks on the feet of infected sheep or goats, or on contaminated land that has seen infected animals walk on it within the previous 7 days.

Virulent footrot

Virulent strains have the ability to underrun from the heel, right along the bottom of the foot and make the hoof peel off, leading to crippling lameness. These infections often affect more than one foot per animal, generally aren’t swollen, and generally don’t produce the opaque pus seen in abscesses; rather any discharge is generally slimy and blackish where the skin-horn (hoof) junction has been broken down. Severe lesions do tend to have a typical “smell” some people are familiar with – it is possible however for virulent footrot to be present without a smell, and for a condition that is not footrot, such as abscess, to have a similar bad smell.

Benign footrot

The benign strains generally begin digesting this skin-horn junction, but don’t go as far, and generally resolve with treatment or improved weather. In optimum weather conditions however, they can still cause significant lameness.

Which is it?

The difficulty with both types of footrot, is their dependence on the right environmental conditions to show their virulence capability. There needs to be an average daily temperature of 10°C or higher for 4 –5 days, adequate moisture, and adequate pasture density in order for foot skin to become susceptible and for D. nodosus to invade and multiply; this is known as a “spread period”.

In unfavourable conditions, disease is generally milder, and both virulent and benign footrot can appear the same. In these instances, you and your District Veterinarian will discuss options based on the situation on your property. Generally, sheep are monitored and reassessed after a spread period has provided an opportunity for the bacteria to show its full potential.

Laboratory testing exists and can be used to support diagnosis – in NSW it is never used alone however, as multiple strains are often present on one property, and all may not necessarily be picked up.

What else can cause lameness?

Foot abscess: Numerous bacteriological agents can be responsible, but they’re generally normal organisms found on-farm. There is usually obvious swelling, and the claws may be pushed apart so there is a significant gap. In these instances, wet conditions have usually softened feet, and an opportunity for bacteria to enter has occurred (eg stepping on something sharp, or in drier conditions, grass seeds etc getting embedded). This bacteria is walled off by the sheep’s immune system – the end result is a pocket of pus surrounding the injury, which prevents infection spreading, but also makes it difficult to heal. The resulting pressure of this pocket is very painful, but once it ruptures it often resolves.
Abscess pain generally causes severe “hopping” lameness, but typically only affects one foot of an affected animal, and does not cause the telltale “underrunning” of footrot.

Scald (OID): This is inflammation of the skin between the toes that can be caused by several bacteria, none with the ability to cause underrunning. Severe cases can still cause significant pain, irritation, and lameness.

Scabby mouth: Along with lesions around the muzzle, this viral disease can also cause telltale scabbed lesions on the feet, particularly if they are in grazing conditions that can break the skin of the feet and allow the virus to enter, as with pasture growing thorny weeds.

Strawberry footrot: This is a concurrent infection of scabby mouth and Dermatophilus sp. (the “dermo” or “lumpy wool” bacterium). It causes lumpy, generally raw or bloody-appearing lesions around the feet and sometimes legs – it has nothing to do with actual footrot.

Arthritis: This does not affect feet at all, but rather the joints of the leg. If affecting multiple animals, it is likely to have an infectious origin such as Erysipelas or Chlamydia spp. If isolated to a couple, it is more likely secondary to injury or infection at birth. The lameness can be seen with swollen knees, hocks, and/or pastern joints. Feet can often become overgrown on affected legs, as hoof wear will be abnormal.

It is worthwhile monitoring stock for signs of lameness and contacting your District Veterinarian if you have any concerns. With virulent footrot being notifiable in NSW, there is a legal obligation for anyone dealing with livestock to report suspicion of footrot within 1 working day.

This being the case, District Veterinarians will always be happy to visit a property and assess any animals you’re concerned about, even if you’re not sure. If virulent footrot is present, the District Veterinarian will work with you to explore options and make a plan that suits your enterprise.
Fortunately, most lameness investigations turn out to have other causes, with which your DV can also assist.

If you have a suspicion that your animals are showing signs of an emergency animal disease, call the Emergency Animal Disease Hotline on 1800 675 888 which operates 24hr a day.

Additional links
Footrot in Sheep - DPI
Footrot in Sheep & Goats - DPI

Foot and Mouth Disease Information Session Wagga – Tuesday 16^th May

Local Land Services is teaming up with NSW Farmers to deliver face-to-face foot and mouth disease information sessions in May 2023.
The Riverina session will be held in Wagga Wagga at the RSL Club on Tuesday 16^th May, from 11-1pm.

The forum will cover:

To express your interest in attending visit www.nswfarmers.org.au/fmdinfo

SAVE THE DATE – Biosecurity & NLIS workshops for landholders
Wagga – Tuesday 30^th May, Wagga RSL
Griffith – Wednesday 31^st May, Griffith Southside Leagues Club
Young – 1^st June, Young Services Club

Riverina landholders are invited to attend Local Land Services interactive workshops discussing NLIS database transfers, PIC reconciliations and practical advice on farm biosecurity plans. Mark the date in your calendar and register here.

AWI – SimpliFly Young - 15^th July, Young Services Club
A new AWI one day workshop that:

To find out more, click here.

District Dashboard

What we've seen...

Red Gut

Hypothermia in Autumn Lambs

What we're looking out for...

Worms

Phalaris Staggers

Case Study 1: 'In a wee bit of trouble'

Image 2: Exterior surface of bladder, severely discoloured

Image 3: Interior mucosal surface of bladder, demonstrating severe haemorrhages

Image 4: Exterior capsule of kidney, demonstrating multifocal haemorrhages

What does this mean?

Virulent footrot – what it is and what it’s not.

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