Recent livestock disease cases

[1]

Nervous signs in sheep could be signs of the reportable disease scrapie. 

Listeriosis diagnosed in ewe

• A ewe was noticed circling in the paddock, and was unresponsive to sound or movement.  A DPIRD field vet visited the property and conducted a disease investigation, which included noting nervous system clinical signs  (abnormal eye movement and circling) and a post mortem.
• Nervous signs in sheep could be signs of the reportable disease scrapie [2]. Producers who have a vet investigate and carry out a post-mortem on suitable cattle or sheep with nervous disease signs are eligible for TSE subsidies [3] to cover all laboratory costs and most post-mortem and travel costs.
• The vet submitted a range of post-mortem samples to the DPIRD laboratory, and testing of brain samples led to a diagnosis of listeriosis, an infection caused by the bacterium Listeria monocytogenes. Additional testing of lung tissue led to a secondary diagnosis of pneumonia.
• Listeria organisms can travel to the brain from the mouth after they are ingested from the environment, or sometimes when they are inhaled.
• Spoiled silage is a common source of Listeria in livestock. In this case the sheep were not being fed silage, but it is suspected that decaying vegetation in the paddock was contaminated with Listeria. 
• Listeriosis in ruminants can also cause abortions or septicaemia (blood poisoning).
• Listeriosis can also be a serious disease in humans. Pregnant and immune-compromised people in particular should avoid contact with potentially infected animals and aborted materials.

[4]

It is important to investigate nervous signs or sudden deaths in livestock, to ensure they are not due to an exotic disease with similar signs such as Bovine Spongiform Encephalopathy.

Sudden deaths and nervous signs in feedlot cattle

• 6 out of 120 weaner cattle died suddenly in a feedlot, with a further 5 affected with nervous signs (unable to get up, lying on side, abnormal head and eye position).
• A private vet attended the property and accessed a significant disease investigation subsidy [5] to reduce costs of the investigation to the producer.
• The vet examined two animals, which were both lying on their sides and unable to rise. The vet conducted a post-mortem, and submitted samples to the DPIRD laboratory for testing.
• It is important to investigate nervous signs or sudden deaths in livestock, to ensure they are not due to an exotic disease with similar signs such as Bovine Spongiform Encephalopathy. Testing for exotic diseases helps to support market access by demonstrating Australia is free from these diseases.
• Lab testing showed that the disease was histophilosis, an infectious condition caused by the bacterium Histophilus somni.
• Histophilus somni can often be found in the respiratory tract of healthy cattle. However, in certain circumstances the bacteria can multiply in the respiratory tract and spread through the bloodstream, most commonly to the brain and heart. This frequently occurs in feedlot situations when environmental stressors and virulent strains of the bacteria combine.
• This diagnosis helped the vet and the producer to manage the disease and prevent further losses.    
• Lab testing also ruled out lead toxicity [6], which could cause similar nervous signs and death in cattle, and is a risk to human food safety and access to export markets.

In early winter, watch for these livestock diseases:

Pregnancy toxaemia in ewes

• Occurs when pregnant ewes do not receive enough nutrition.
• Drastically low levels of glucose in the blood damage the brain and lead to dehydration, kidney failure and potentially death. Usually occurs in ewes with twin lambs and in the last weeks of pregnancy.
• Signs in affected ewes can include depression, not eating, weakness, nervous signs and death.
• All pregnant ewes should be carefully managed. Adequate nutrition should be provided and stress events minimised. It is recommended to identify twin mothers using pregnancy scanning and then separate and preferentially feed them to minimise the risk of pregnancy toxaemia.
• A vet can advise on treatment, which usually involves giving a drench containing glucose. 
• Read more on pregnancy toxaemia in sheep [7].

Hypocalcaemia in sheep

• Condition in sheep that can have similar signs to pregnancy toxaemia.
• Caused by a deficiency of calcium in the blood stream, which impairs normal muscle function. 
• Ewes in their last six weeks of pregnancy and in the first month of lactation are most at risk, but unlike pregnancy toxaemia, hypocalcaemia is not confined to pregnant ewes. Lambs or other sheep in good condition are susceptible to hypocalcaemia after a stressful event such as moving, trucking or yarding. Other stressful events that cause sheep to go off feed such as extreme weather events can also predispose sheep to hypocalcaemia.
• Treatment involves an injectable product containing calcium borogluconate. It is always worth phoning a vet for advice because some reportable diseases can look similar to hypocalcaemia, such as the exotic disease scrapie.
• Read more information on hypocalcaemia [7].

You should phone a vet if you see nervous signs in your livestock. Some exotic diseases such as transmissible spongiform encephalopathies [3] also cause nervous signs in livestock. Testing helps to prove that WA is free from such diseases and this in turn supports the industry.   

Calf scours

• Usually occurs in young calves in late autumn and early winter.
• Signs in affected calves include depressed appearance, diarrhoea, dehydration and death.
• Calf scours are caused by a combination of environmental factors and infectious organisms. Certain types of bacteria, viruses and protozoa can all cause calf scours.
• Your vet can submit a sample of scours to the laboratory for testing to determine the cause to help select the most effective treatment.
• Prevention should focus on ensuring that cows are in good condition, with optimum nutrition and in a low-stress environment so they can produce good quality colostrum for their calf. Colostrum is important to protect the calf against disease. Calves born easily in a sheltered environment will be best able to consume enough colostrum to protect them from disease.
• Some calf scour organisms can infect humans so it is advisable to wear rubber gloves and to wash hands and skin thoroughly after treating scouring calves. 
• Read more about treatment and prevention of calf scours [8].