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.
Catch up with local private and DPIRD vets at the DPIRD shed at Dowerin Machinery Field Days
Local private vets and the DPIRD Northam and Moora vets will be at the DPIRD shed at Dowerin Machinery Field Days this week to assist with any veterinary and biosecurity queries you may have.
Take the opportunity to drop in and pick up a handy summary factsheet of all the subsidies available for disease investigations that you can hand to clients, and to catch up on with your colleagues. There will also be other resources for your clients including factsheets on common sheep diseases, correct pig feed, pig biosecurity and on emergency diseases including foot-and-mouth disease and African swine fever.
Recent livestock disease cases in WA
Hendra virus excluded in two cases of neurological signs in horses
- In June, there were two separate cases of neurological signs in horses in which Hendra virus was excluded.
- In the first case, a 20-year-old pony had a one-week history of unilateral blindness, ataxia, reduced proprioception and circling. These signs progressively worsened, and the horse became pyrexic, lethargic, depressed and inappetent. The horse was not vaccinated for Hendra virus and there was no history of travel. There was one other horse on the property, as well as some sheep, none of which were displaying any clinical signs.
- In the second case, a single horse agisted with 30 others displayed dullness, ataxia, dyspnoea, nasal discharge and anorexia. The horse also had an extended head and neck and bloody oral discharge. The horse was penned in an area where flying foxes were roosting. No other horses at the property were unwell, and the horse did not have a current Hendra virus vaccination.
- In both cases, a private vet examined the animals and considered the possibility that the clinical signs were due to a reportable disease such as Hendra virus. Given the zoonotic potential of this virus, it was imperative to avoid contact with the horses until exclusion testing was conducted. The private vets contacted DPIRD to arrange for laboratory testing, which was subsidised by DPIRD.
- Fortunately, in both cases the horses tested negative for Hendra virus. Testing for other emergency diseases of horses was also negative, including equine influenza, equine encephalomyelitis, equine herpes viruses 1 and 4, West Nile virus, Murray Valley encephalitis and rabies.
- In the first case, while reportable diseases were ruled out, a definitive diagnosis could not be established, and in the second case, a dental abscess was suspected as the cause of the clinical signs.
- Hendra virus can be transmitted to horses by exposure to secretions from infected flying foxes, including their urine. A case has never been reported in horses in Western Australia, however flying foxes in northern WA have shown evidence of exposure to Hendra virus, presenting a risk to horses in contact.
- The virus can be transmitted from infected horses to people, and it may cause serious, frequently fatal disease in humans. There have been four human deaths in Australia since the virus was first diagnosed in 1994, all occurring in Queensland.
- For further information on Hendra virus, including how to reduce the risk of horses becoming infected, and safety advice for veterinarians, see the Hendra virus webpage.
Private vet helps rule out foot-and-mouth disease (FMD) in calves in the South-West
- In a herd of 150 two-month-old Angus cross calves, one had died and one was unwell showing severe pyrexia, nasal discharge and respiratory distress.
- A private vet performed a post-mortem on the one dead calf, and found froth in the trachea and lungs, and multifocal ulcerations around the larynx.
- A full range of bloods, fresh and fixed tissues was submitted to the DPIRD laboratory, with the private vet suspecting infectious bovine rhinotracheitis or calf diphtheria (necrobacillosis).
- Histopathology identified a severe ulcerative laryngitis with intralesional mixed bacteria, acute hepatocellular necrosis and diffuse pulmonary oedema.
- The reportable diseases foot-and-mouth disease and vesicular stomatitis were excluded through testing on laryngeal tissue and bloods.
- Bacterial culture of the laryngeal tissue isolated Bacteroides pyogenes, which is an opportunistic pathogen. The disease was attributed to a bacterial infection, possibly associated with a failure of passive transfer.
- Reaching a diagnosis allowed the private vet to work with the producer to manage the disease.
- Given that this investigation provided evidence of Australia’s freedom from trade-sensitive diseases, DPIRD paid the laboratory fees.
- Clinical signs consistent with foot-and-mouth disease (such as shown in Figure 1) should always be reported to a DPIRD vet or the Emergency Animal Disease hotline on 1800 675 888. Early detection = faster eradication.
Neurological signs in Merino hoggets in the Wheatbelt
- A DPIRD vet was contacted by a Wheatbelt producer about nervous signs in one-year-old Merino ewe hoggets. Of the flock of 200, one had died and other animals had been found separated from the group, obtunded, staring into space, with some appearing blind.
- The DPIRD vet visited the property and conducted an on-farm investigation and a post-mortem on the dead ewe. It was in good body condition, with no significant gross pathological lesions. Fresh and fixed tissues and ocular fluid were submitted to the DPIRD laboratory with a provisional diagnosis of polioencephalomalacia (PEM).
- Histopathological examination revealed chronic PEM of at least several days’ duration, characterised by extensive lamellar malacic lesions affecting the cerebral cortex. These findings correlated with the clinical history of several days of neurological impairment (see Figure 2).
- The most common cause of PEM in WA is thiamine deficiency, which reduces energy availability to the brain and causes a classic pattern of degeneration. Most outbreaks of PEM are sporadic and affect only a couple of animals in a mob, but death rates of up to 10% have been reported.
- Less common causes of PEM include lead toxicosis, sulphur toxicosis, salt poisoning, or consumption of certain plants including bracken fern, Nardoo fern and horsetail.
- For more information on PEM, including treatment, see our PEM webpage.
In late winter/spring, watch for these livestock diseases
Disease, typical history and signs
Selenium deficiency in lambs and calves