WA Livestock Disease Outlook - for vets

Livestock disease investigations protect our markets

Australia’s ability to sell livestock and livestock products depends on evidence from our surveillance systems that we are free of particular livestock diseases. The WA livestock disease outlook – for vets summarises recent significant disease investigations by Department of Primary Industries and Regional Development (DPIRD) vets and private vets that contribute to that surveillance evidence.

Recent livestock disease cases in WA  

Several cases of annual ryegrass toxicity (ARGT) cause livestock deaths

  • Since 1 March 2018, DPIRD has investigated 16 cases of ARGT in livestock in Western Australia, including seven cases in cattle, six in sheep, two in horses and one goat.
  • In one case, a herd of 50 two-year-old Jersey cows was affected, with one death and one cow affected by sudden onset of ataxia, inappetence, muscle fasciculations and recumbency. The herd was fed silage and grazing a mixed pasture.
  • Given that the clinical signs and deaths were unusual, DPIRD granted a private vet a subsidy of $330 under the Significant Disease Investigation program.
  • Samples including faeces, blood, pasture, silage, and a range of fresh and fixed tissues were submitted to the DPIRD laboratory with provisional diagnoses including ARGT, listeriosis and thrombotic meningoencephalitis.
  • Both the pasture and faecal samples tested positive for ARGT. Clinical biochemistry indicated a mild increase in hepatobiliary parameters (GGT, GLDH), which is often noted in ARGT. Marked increases in CK and ALT were also present, indicating muscle injury likely due to recumbency and/or misadventure while ataxic. Histopathology did not detect significant lesions.
  • ARGT at this time of year is more likely to be from affected supplementary feed such as hay or silage. ARGT on pasture is most often seen in spring when livestock graze pastures containing infected ryegrass seed heads. Note that drying the grasses for hay does not eliminate the toxin.
  • See DPIRD’s recent media release on ARGT, as well as the DPIRD ARGT webpage for more information.
Map showing location of ARGT cases diagnosed at DPIRD
Figure 1: Map of WA ARGT cases diagnosed at DPIRD for the period 1 March 2018–31 March 2019

Bluetongue and screw-worm fly excluded in sheep at abattoir

  • In the past month, DPIRD has received two submissions to exclude reportable diseases from sheep at abattoir.
  • In the first case, five Merino ewes from a line of 1044 had a nasal discharge, conjunctivitis and corneal opacity. Histopathology and biochemistry at DPIRD showed chronic keratitis and blepharitis, leading to a diagnosis of infectious keratoconjunctivitis. Given that bluetongue virus also causes nasal discharge in sheep, a bluetongue PCR and ELISA were also run at DPIRD, both of which were negative.
  • In the second case, a Merino ewe with a maggot-infested wound was identified at ante-mortem inspection. The ewe was removed from the slaughter line, euthanased and maggots were collected into 70% ethanol and submitted to DPIRD to exclude the exotic screw-worm fly (see Figure 2). The larvae were identified as sheep blowfly, Lucilia cuprina. See the DPIRD flystrike tools webpage.    
  • The results of these cases contribute to demonstrating WA’s and Australia’s freedom from these diseases, which gives us a market advantage and allows us to export livestock products widely.
  • Always report any suspicion of a reportable disease immediately to a DPIRD field vet or the Emergency Animal Disease hotline on 1800 675 888. Early detection = faster eradication.
Screw-worm fly maggots in a wound
Figure 2: Screw-worm fly maggots in a wound (Image: Department of Agriculture and Water Resources)

Infectious laryngotracheitis and chronic respiratory disease in mixed age hens

  • In a flock of 100 mixed-age birds, including turkeys, pheasants and chickens, eight chickens died suddenly over a two-week period. Several birds were affected by ocular swelling and discharge (see Figure 2).
  • Two birds were submitted to the DPIRD laboratory for investigation. On post-mortem examination and histopathology, they had a severe tracheitis with intranuclear inclusions, moderate to severe bronchopneumonia and chronic sinusitis. Virology of tracheal swabs revealed an infection with infectious laryngotracheitis (Gallid herpesvirus 1), and culture for Mycoplasma species (both M. gallisepticum and M. synoviae) was positive for both birds indicating the flock was concurrently affected by chronic respiratory disease (CRD).
  • Reportable diseases including avian influenza and Newcastle disease were ruled out as the cause of the disease.
  • DPIRD has a guide to assist vets in investigating poultry disease, including how to conduct a post-mortem and samples to collect to maximise the likelihood of reaching a diagnosis.
Chicken with ocular swelling and discharge
Figure 3: Chicken with ocular swelling and discharge

In early autumn, watch for these livestock diseases

Disease, typical history and signs Key samples

Grain overload in stock

  • Also known as acidosis or grain poisoning. Consumption of large amounts of grain without gradual introduction can result in acidification of the rumen, gut stasis, dehydration and deaths.
  • Carbohydrates in grain are rapidly fermented by some rumen bacteria to produce increased lactic acid, causing acidosis.
  • Signs include depression, recumbency, diarrhoea, thirst, left abdominal bloating, sawhorse stance and ataxia.
  • Treat supportively. The rumen may take six weeks to repair, and animals may show poor growth rates in this time.
  • Read more on grain overload in stock.

Post-mortem:

  • Field rumen pH test; a pH of <5 is diagnostic for acidosis, <5.5 is suspicious. Test at the time of post-mortem as pH increases with time
  • Rumen tissue (fixed).

Pink eye in cattle and sheep

  • Signs include light sensitivity, excessive blinking, watery eyes, eye ulceration and decreased productivity.
  • Treatment and prevention methods include antibiotics, reducing fly populations and dust/UV exposure, isolating affected/brought-in animals, and eye patches and vaccination in cattle.
  • Read more on pink eye in cattle.

Ante-mortem:

  • Diagnosed on clinical signs and history
  • Conjunctival/ lacrimal swab: (1 in gel, 1 in mycoplasma medium if available): confirm with microbial culture.

Neurologic signs in cattle? Remember Bucks for Brains!

We need your help to meet WA’s surveillance targets for bovine spongiform encephalopathy (BSE) for the 2018/19 financial year. Australia does not have BSE but we need ongoing surveillance to maintain market access.

If you see cattle with gait abnormalities such as wobbling, staggers or goose-stepping, constant trembling or increased sensitivity to sound and touch, consider whether they may be suitable for post-mortem under the TSE program. Under the program, the owner and vet receive a subsidy of $300 per animal for up to two animals and veterinary, sample freight and laboratory costs are normally covered. The DPIRD NTSESP webpage explains the program or you can contact your DPIRD vet.

Register now for your DPIRD regional vet workshop

Don’t miss your chance to attend a livestock disease workshop in your region in May. Topics covered will include African swine fever, current livestock disease projects, antimicrobial resistance and discussion of interesting cases. Contact your local DPIRD field vet to register.

  • Bunbury – Friday 17 May, 5pm
  • Albany – Saturday 18 May, 2:30pm
  • Northam – Friday 24 May, 5pm
  • Dongara – Saturday 25 May, 2:30pm

WA Livestock Disease Outlook highlights benefits of surveillance

Australia’s ability to sell livestock and livestock products depends on evidence from our surveillance systems that we are free of particular livestock diseases. The WA livestock disease outlook – for vets summarises recent significant disease investigations by DPIRD vets and private vets that contribute to that surveillance evidence.

We welcome feedback. To provide comments or to subscribe to the monthly email newsletter, WA livestock disease outlook, email waldo@dpird.wa.gov.au.