WA Livestock Disease Outlook - for vets

Reporting livestock disease protects our ability to trade

Australia’s ability to sell livestock and livestock products depends on evidence from our surveillance systems that we are free of livestock diseases that are reportable or affect trade. To gather this proof of freedom, the Department of Agriculture and Food, Western Australia (DAFWA) investigates cases where livestock show signs of disease similar to reportable or trade diseases.

The WA livestock disease outlook – for vets (WALDO) is collated from information collected by DAFWA and private veterinarians as part of proving Australia’s freedom from those diseases. In 2015/16, data from our surveillance systems allowed WA to access markets valued at $2 billion.

Recent significant cases submitted to DAFWA Diagnostic Laboratory Services (DDLS)

Case data from January 2017 to February 2017

Sudden death in Angus steers and heifers in the Goldfields-Esperance region

• Twenty young, recently introduced steers and heifers died in a herd of 400 cattle.
• Some animals showed signs of gait abnormalities and lethargy while others died without any clinical signs.
• The cattle were weaned on hay and then turned out onto barley and oat stubble. Ryegrass and ergot were known to be present in the paddocks.
• Based on the clinical signs, the appearance of ruminal and abomasal inflammation on postmortem and the nutritional history, the main differential diagnoses were acidosis, annual ryegrass toxicity (ARGT), ergotism and bovine viral diarrhoea virus (BVDV).
• Testing for plant toxins excluded the involvement of ergot, ARGT and fluoroacetate-containing plants.
• Samples submitted to DDLS showed severe, necrotising myocarditis with similarly affected areas of skeletal muscle and a mild, necrotising encephalitis and meningitis.
• The acute and severe necrosis and inflammation of the heart were attributed to the bacterium Histophilus somni, which was cultured from the heart sample. Low vitamin E in a liver sample coupled with changes to the muscle groups suggested that nutritional myopathy was contributing to disease in the herd.
• Systemic H. somni can occur in young cattle with the stress of transport, mixing and new management systems and affected stock may need to be treated with antibiotics.
• Testing was negative for BVDV Type1 (BVDV-1) and the reportable disease bovine viral diarrhoea virus Type 2 (BVDV-2) was ruled out with PCR testing. BVDV-1 is present in Australia, but the more severe Type 2 found in North America and Europe has not been detected in Australia.

Exclusion testing for reportable diseases such as bovine viral diarrhoea virus Type 2 supports Western Australia’s proof of freedom for export to BVDV-2-sensitive markets.

Annual ryegrass toxicity in a 14-year-old pony in Perth

• A private vet examined a 14-year-old pony that started showing signs of muscle fasciculation, facial twitching, wide base stance, hypermetric hind limb gait and ataxia.
• The pony was being fed meadow hay sourced from a local supplier.
• It was unknown if the meadow hay had been tested for annual ryegrass toxicity (ARGT).
• All grazing animals are susceptible to the toxin, including horses and pigs.
• A faecal sample and hay sample were submitted for testing. The results were ARGT positive in the faeces and high risk in two out of three of the hay samples.
• ARGT may be difficult to diagnose if hay is sampled incorrectly or insufficient samples are provided.

Go to DAFWA’s webpage on testing hay for annual ryegrass risk for more information and sampling instructions.

Collapse and anaemia in dairy cow in the South-West

• A private vet was called to investigate a five-year-old cow, 120 days in milk, which collapsed when coming in for evening milking.
• She was found moderately bloated with a fever and increased heart and respiration rate.
• Samples sent to the lab confirmed a non-regenerative anaemia and thrombocytopaenia with hypocalcaemia, hypermagnesaemia and hyperphosphataemia.
• Hypocalcaemia (milk fever) occurs mainly around calving and early signs include agitation or excitement, muscle fasciculations and ataxia. This can lead to collapse and in some cases death.
• Nutritional management of pregnant and lactating cows is important in preventing hypocalcaemia.
• Given the signs and presence of anaemia, the cow was tested for Theileria orientalis group by a PCR test and the results were negative.

Bovine anaemia due to Theileria orientalis group (BATOG) causes a severe regenerative anaemia in an infected animal and signs can include jaundice, pallor and red urine. The main vector is the bush tick (Haemaphysalis longicornis), which occurs in WA south western coastal areas. Veterinary sampling kits are available if Theileria is suspected. Samples can be submitted to DDLS for testing for BATOG and other diseases that may cause similar signs. Contact your DAFWA field veterinary officer to obtain a testing kit.

In March, due to high summer rainfall and flooding, be on the lookout for:

Include base samples and any clinical or gross lesions in submissions. For advice on sample submission, contact your DAFWA field veterinary officer, see the DAFWA sampling and postmortem resources webpage or phone the DDLS duty pathologist on +61 (0)8 9368 3351.