SELLS Animal Health Update December 2020

December 2020

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SOUTH EAST DISEASE SURVEILLANCE RESULTS

Alex Stephens District Veterinarian Yass.

Your local District Vet can help you to investigate, diagnose and manage herd health or mortality issues in your herd or flock. They provide impartial advice and can assist you with the disease management part of your biosecurity plan. Each month we provide this report of diseases and issues detected and managed in the last month by producers, their veterinarians and animal health advisors.

Johne’s disease has been found in sheep flocks and in beef and dairy cattle. These animals became obvious after lambing or calving as they became very poor and obviously ill thrifty in comparison to the rest of the flock/mob. Johne’s is caused by a bacterial infection of the gut wall early in life. The thickening of the gut wall resulting in malabsorption of nutrients and death occurs later in life.

Theileria has been detected in coastal cattle presenting with collapse, lethargy and jaundice. Theileria orientalis is a blood parasite which causes red blood cell destruction and usually mild anaemia in cattle.  It is transmitted by the transfer of blood, usually by ticks or injections needles and occasionally by biting insects. The disease is endemic on the coast, but problems occur when either cattle are brought from the coast inland or inland cattle are taken to the coast. Young calves, cows in late pregnancy or recently calved can be affected with more severe disease, including anaemia, fever, lethargy, jaundice, abortions and deaths.

Footrot, both benign and virulent, has been detected in sheep flocks. Conditions, being warm and wet with a good clover base have been ideal for expression of foot rot for many months. Virulent foot rot is a notifiable disease, meaning that you must call your local District Veterinarian if you notice lame sheep, especially if there is underrunning of the hoof at the heal. The District Vet will look at the proportion of sheep that are affected, and how severely affected they are, to classify the disease. The bacterium Dichelobacter nodosus causes benign and virulent foot rot, there are many different strains with variable amounts of power to underrun the heal.

Take great care when restocking that you don’t buy footrot in, especially if purchasing sheep from interstate. Keep any new sheep that you have purchased isolated from the rest of the flock until you know their disease status. Ensure your boundary fencing is good and that you check all strays. Foot bathing is a very effective management tool. 10% Zinc sulphate is the most frequently used chemical. To use most effectively it requires a contact time of at least 5 minutes - ideally up to 15 followed by at least an hour of drying time. For more information click here.

Mycoplasma ovis has caused deaths of both unweaned and newly weaned lambs on a number of properties. This disease causes anaemia, ill thrift and death. A feature article may be found below.

Selenium deficiency has been diagnosed in sheep and cattle on blood tests. Selenium deficiency is a region and property specific problem made seasonally worse in years where there is profuse clover growth. Deficient properties will need to put measures in place to prevent ill-thrift in weaners. There are a number of prevention options, including using selenium in drenches and vaccines, but excellent long-term protection is achieved by using a long-acting selenium at weaning (lasts 12-18 months).

Calf scours has been causing issues on some properties. When scours are occurring, antibiotics are seldom required but deaths do occur from dehydration. Provide a change of paddock and then more closely monitor mobs for affected calves. Catching calves that are unwell and drenching with electrolyte enriched fluids such as vytrate can be a life saver. If you are getting calf deaths talk to your veterinarian.

Lambs with a bloody scour were diagnosed on post mortem with coccidiosis and responded well to the change of paddock and sulphadimadine drench supplied by their local private practitioner.

Lead poisoning has been seen on three properties. The most usual source is an old (often burnt) lead battery, but licking at any lead items or old paint can cause poisoning.  Lead poisoning is not only a concern because it causes disease in stock, but also because we do not want lead entering the food chain. Stock that have been in contact with a lead source must be blood tested to determine their lead levels and only allowed to be sold for slaughter when levels return to normal. In some cases, this may be years so prevention is always the best.  Disease in stock is see as abdominal pain, depression, bizarre behaviour and/or death.

Pneumonia caused by manheimmia haemolytica has cause intermittent occasional losses in lambs and goats. The rapid weather changes from cold to hot with windy rain events may be contributing. Avoiding dust and indoor housing of sheep is key in preventing outbreaks.

Liver fluke has been detected in both cattle and sheep, on blood tests and faecal tests. Conditions have been very suitable for the snail which hosts part of the life cycle. Cattle and sheep may have come through from last summer/autumn with infestations. If required, a fluke control now will prevent the development of clinical disease in younger stock during the summer.

Campylobacter has been identified through blood tests as the cause of reproductive wastage on sheep properties that were disappointed with their scanning to lambing results in the maidens. They also felt that they had a significant difference between the results in the maidens compared with the more mature ewes. These factors all point towards it being likely that vaccinating with campyvac® will provide benefit to the flocks.

Grass seeds are starting to cause issues in lambs and dogs, getting into eyes and ears, requiring removal and treatment. Pasture preparation is key in preventing grass seed penetration of the skin and body.

Blow fly strike is causing considerable issues and many producers brought weaning forward in order to get fly protective treatments onto lambs to assist in preventing fly strike.  Please see the article below for recent research results.

WORMBOSS REPORT

Rainfall in the last month was >50mm in most areas. Temperatures have been mild with the daily average around 15 degrees, making conditions excellent for foot rot and worms. Nutrition over the last months has been excellent, in excess and high quality. It has not been hard to find clean pastures for stock. The challenge going forward over the next months will be the long grass, i.e. feed quality and knocking growth down enough to be suitable for sheep, especially weaners. Sometimes in these situations sheep may not travel and may intensify their grazing in grazed spots creating an artificially high worm risk environment, especially for barbers pole worm.

Monitoring your own stock with Faecal Egg Counts (FECs) now is very wise as FEC results over the last month across the district have been so variable. In some places counts are climbing (from 500-5000) due to high barber’s pole worm percentages, and on others there is no barber’s pole evident and scour worms may be causing low (28) or high counts (680). Many properties have had low counts due to good nutrition and relatively clean paddocks after the drought, and effective previous drenching.

Monitoring for rising FECs allows you to assess the need to bring the summer drench forward, or delay it.

As temperatures rise the conditions for barber's pole worm become more ideal. It is essential to monitor for this worm now to nip outbreaks in the bud, with an effective drench and movement to clean pastures.

Monitoring for fluke has continued in both cattle and sheep and results showing some occasional positive results. Any positive result indicates that this parasite needs to be managed either by strategic drenching or strategic grazing (keeping cattle and sheep off potentially snail infected flood flats) or both.

MYCOPLASMA OVIS

Mycoplasma ovis (M.ovis), previously known as eperythrozoonosis, is a bacterial infection of sheep and goats. M. ovis infects the red blood cells of the animals, prompting the spleen to attempt to clear the infection by destroying the diseased blood cells. It is this excessive destruction of the blood that leads to anaemia, jaundice and death. Disease outbreaks can last for 14 to 28 days.

Clinical signs include:

• ill-thrift
• anaemia (pale gums)
• jaundice (yellow gums)
• dark red urine
• death (particularly following a stress event such as mustering/yarding).

M. ovis has been seen in sheep of all ages from 4 weeks upwards, while sheep of all ages can be affected it is an important disease of weaner sheep. It is important to note that not all infected sheep will show signs of the disease and that symptoms of anaemia and ill thrift may be caused by other diseases such as worms or fluke. The effect of M. ovis is more severe if sheep are stressed by other conditions such as internal parasites or malnutrition. Deaths may occur in severely affected young sheep, especially if they are stressed by yarding. Losses of up to 30% of the flock have occurred in these circumstances. For this reason, it is important to seek advice from your veterinarian and obtain a diagnosis if you suspect ill-thrift in a mob of lambs or weaners before you yard or handle them.

The immune system of most sheep will effectively fight off the infection if nutrition is adequate. Some animals will not completely rid the infection and stay infected for life. These ‘carrier’ animals are the most likely source of infection for other sheep. A reservoir of infection is probably maintained in breeding ewes. Flock prevalence in Southern Australia is thought to be as high as 90%. Merinos are more commonly affected than other breeds.

M. ovis is spread by the transfer of infected red blood cells from one animal to another. Most commonly outbreaks occur 4–6 weeks after marking, mulesing, crutching or shearing. Insect vectors such as bloodsucking insects (e.g. mosquitoes and midges) and flies on wounds, can also spread the disease. Ensure hygenic practices at lamb marking to minimise transfer of blood from one animal to another, this includes ensuring that mulesing shears and tail marking apparatus are soaked in an effective disinfectant between lambs.  Many contractors use two sets of shears so that one can be soaking while utilising the other, swapping after each lamb.

If your flock or herd is suffering losses with anaemia and you have ruled out worms and fluke by conducting egg counts, seek veterinary advice.

FLYSTRIKE AWARENESS AND INSECTICIDE RESISTANCE

An amplified flystrike season is on us following the wet and warm spring. Applying flystrike prevention products combined with other management such as more frequent crutching or bring shearing forward will be important.  Recent research has demonstrated widespread resistance developing to our mainstream flystrike prevention products. It is urgent that producers strategically manage the use of these products to maximise fly control and minimise the development of resistance.

The latest AWI/DPI funded project on insecticide resistance, completed 30 June 2020 examined maggots from fly strike wounds from across the state. Unfortunately, it showed that as well as resistance to the older products, 100% of those tested (55/55) had resistance identified to dicyclanil and cyromazine. These 2 products are related and form the backbone of current flystrike prevention. Lucilia cuprina the green backed Australian sheep blowfly initiates most cases of fly strike. The fly has demonstrated a capacity over the years to develop resistance to insecticides, reducing their efficacy.

Preventing the development of resistance involves producers applying the following principles:

1. Use an integrated approach to reduce reliance on chemicals
2. Rotate your chemical groups where practical, this involves knowing which chemical group the product you are using fits into.
3. Use a different chemical to treat fly strike to what you use for protection.
4. Minimise the number of insecticide treatments you apply in a season.
5. Apply insecticides carefully and as specified on the label.
6. Monitor for flystrike frequently and follow the guidelines for best management of flystrike
7. Collect and kill all maggots from fly struck sheep   FOR MORE INFORMATION SEE LINK. 190415-SHEEP-BLOWFLY-RESISTANCE-MANAGEMENT-STRATEGY-FINAL-GD3349.pdf (flyboss.com.au)

If you are worried that you may have a product resistance issue in your flock, sheep blowfly resistance testing is still available at EMAI, at a cost of around $350. Kits are available at the LLS offices.

BEST MANAGEMENT OF FLYSTRIKE

For more information and best treatment and prevention options see  FlyBoss.com.au

1. Shear struck wool and a 5 cm barrier of clean wool around the strike close to the skin to remove maggots.

• Unless wool is shorn off it is likely that maggot trails will be missed and sheep will remain struck.
• Machine-shearing is generally better than hand-shearing.

2. Collect the maggot-infested wool into a maggot-proof (plastic) bag and leave the bag in the sun for a couple of days to kill all maggots.

• This breaks the life cycle, which is especially important if the maggots have survived on sheep that have had a preventative product applied previously and these maggots are resistant to the product.
• Don’t rely on registered flystrike dressings to kill maggots—some are incapable of killing large maggots and many maggots escape treatment by dropping from the sheep and burrowing into the soil before the insecticide can be applied. Unless maggot infested wool is collected and bagged, most maggots will survive and pupate and come back as adult flies.

3. Apply a registered flystrike dressing to the shorn area to prevent re-strike.

• If necessary, these treated sheep may be jetted or back lined along with other susceptible sheep to provide long-term flystrike protection. Ensure a product with a suitable withholding period is chosen.
• Note: A product registered as a flystrike "dressing" is different to a preventative. A dressing has two purposes: to kill remaining maggots and to prevent re-strike as the affected area is drying and healing. Where maggots remain, the two common flystrike preventatives, dicyclanil (e.g. CLiK) and cyromazine (e.g. Vetrazin), when applied alone, are not suitable on welfare grounds, as maggots will take up to 4 days to die. Where maggots may remain, a dressing that rapidly kills maggots should be applied; these contain either ivermectin, spinosyn or organosphosphates. There is a high level of resistance to the organophosphate, diazinon, which may reduce its effectiveness in killing larger larvae. One of the dicyclanil or cyromazine preventatives may also be applied if longer ongoing protection is required. Products that contain either spinosyn (Extinsad) or ivermectin will both kill maggots and provide some residual protection.

4. Remove struck sheep from the mob.

• Leaving struck sheep in the mob attracts more blowflies.
• Moving struck sheep to a ‘hospital’ paddock allows closer monitoring of recovery and reduces the risk to the rest of the mob.

5. Cull struck sheep from breeding programs

• Susceptibility to flystrike is heritable and repeatable. Sheep that have been provided suitable management and/or chemical protection but have become struck when most of their flockmates have not are best culled from breeding programs to improve both current and future flock resistance to flystrike. They can be maintained with extra protection as dry sheep.
• Adult sheep that sustain repeated flystrike (crutch or body) are best removed from the property.

GRASS SEEDS IN LIVESTOCK AND PETS

Jordan Ackland Year 5 Veterinary student Charles Sturt University

A common occurrence of every late spring/summer is the infestation of grass seeds that cause problems for animals and producers alike. Although small and seemingly insignificant to many producers, grass seeds can cause very serious disease, loss of production and potentially death if they are not detected and managed effectively.

For both cattle and sheep producers grass seeds can have a significant financial impact on their enterprises, decreasing their overall profitability through reduced growth rates of animals especially younger stock, higher rates of disease within the herd and downgrading of carcass and wool quality at sale.

The way grass seeds cause so much trauma is due to their structure, firstly their long hair like projections allow the seed to find purchase on the animal’s coat or wedge themselves in grooves such as in between toes. Once attached their arrow shaped tip allows them to bury deeper into skin while not moving backwards.

Clinical presentation of the disease is highly varied and is dependent on where the grass seed implants. Potential presentations are abscess formations around the jaw, neck or on the body in addition to weight loss, or ulcerative lesions of the eye that progress to pink eye or complete blindness.

Less noticeably, grass seeds infestation may remain undetected but can cause substantial effects on enterprise productivity. Reports indicate poor growth rates due to a reduced feed intake of up to 1kg/day in grower lambs impacted by heavy grass seed burden (NSW Department of Primary Industry, 2013). Growth rates are further diminished when grass seed wounds result in lameness, weight loss and irritation of the skin (causing animals to rub and damage wool and hides). Additional losses are seen with grass seed contamination of carcasses with price reductions up to $1.5/kg (Meat and Livestock Australia, 2015).

Detection of grass seed lesions can be difficult in animals, however in sheep this can be especially true. For a thorough assessment producers should examine the amount of grass seed contamination present in the wool, specifically looking at the head, neck, shoulder, brisket, underbelly and legs regions of the animal.

In managing grass seeds appropriate identification and awareness of problematic grasses is important, common grasses that are associated with lesions include barley grass, brome grass, Chilean needle grass, erodium, silver grass, spear grass and wire grass. Both long term and short-term strategies can be employed to manage these grasses in addition to salvage strategies which are implemented as a last resort to reduce profit loss associated with grass seeds while a high-risk period is imminent.

Early detection and treatment of grass seeds found in the eye of any animal is recommended, as well as in ears, noses, feet and bodies of dogs and cats. This is because early detection both decreases the risk of further complications and infection associated with migration of the seed, but also increases the vet's ability to identify and remove the seed before it migrates and becomes harder to find.