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Learn about the symptoms and treatment for nervous signs which are conditions that cause staggers, blindness, convulsions, or unusual behaviour.

Nervous signs

Conditions that cause staggers, blindness, convulsions or unusual behaviour. What class of stock is affected?

Adult cattle

Young stock

  • Annual ryegrass toxicity

    Annual ryegrass toxicity

    Occurs in annual ryegrass pastures in South Australia and Western Australia.

    What to look for

    Ranges from mild to severe nervous signs, ie staggering, convulsions, death can occur in severe cases.

    Cause

    A bacterial toxin spread by a pasture nematode (worm). A tiny nematode invades the developing seed head in annual rye grass and turns it into an abnormal growth called a gall. The nematode carries bacteria that multiply rapidly in the gall and produce a powerful toxin that looks like yellow slime. The toxin in the gall is very persistent, so infected pastures will remain toxic until the affected plant material is removed or dies down. Hay made from toxic pastures may also cause ARGT.

    Animals likely to be affected

    All age groups of cattle are susceptible.

    Other diseases with similar clinical signs

    Lead poisoning, phalaris staggers or perennial rye grass staggers that occurs on perennial rye grass pastures.

    Confirming the diagnosis

    Finding of galls and yellow slime on annual rye grass plants. Note that rain can wash the slime off the plants.

    Spread of the disease

    The disease can be spread beyond the affected region via toxic hay, although it is not clear whether this can lead to establishment of ARGT in new regions.

    Treatment

    Any stock movement should be done carefully to avoid injuries and worsening of the clinical signs. Affected mobs should be moved quietly to a non-toxic area and supported with free access to water and high quality feed. Animals may continue to show clinical signs of ARGT for up to 10 days after being removed from the toxic pasture.

    Prevention

    If paddocks are suspected of being infected they can be sprayed out and replaced, or prevent the pasture developing seed heads by topping or hard, persistent grazing. A biological control agent called twist fungus is available commercially, which appears to be effective in reducing toxicity when it becomes established in pastures.

    More information

    Department of Agirculture WA - Annual ryegrass toxicity in livestock

  • Grass tetany

    Grass tetany

    What to look for:

    • Can range from mild signs to a rapidly fatal illness:
    • Sudden death
    • Strange behaviour or aggression
    • Convulsions and muscle spasms
    • Over reaction to sounds or movement
    • Collapse
    • Milder cases show poor appetite, slight agitation and reduced milk production

    Cause - low magnesium intake

    Cattle cannot store magnesium so require a daily intake to maintain adequate blood levels. Symptoms occur when the cow'™s magnesium levels drop below a threshold level. Animals are most at risk when grazing lush pasture especially if it has been fertilized with nitrogen or potash. Outbreaks of grass tetany may be set off by a sudden change of pasture or by bad weather that reduces grazing time.

    Animals likely to be affected

    Dairy cattle within the first 6 weeks after calving. Susceptibility increases with age. Grass tetany is generally a herd problem.

    Other diseases with similar signs

    Other causes of sudden death:

    • Milk fever
    • Anthrax
    • Nitrate poisoning
    • Clostridial diseases

    Diseases causing nervous signs:

    • Nervous
    • ketosis
    • Lead poisoning
    • Urea poisoning
    • Listeriosis (usually a single animal)
    • Polioencephalomalacia (usually young animals)

    Confirming the diagnosis

    Blood magnesium levels are not a reliable diagnostic test in dead animals, so your vet may take a fluid sample from the back chamber of the eye.

    Treatment

    The aim is to increase blood levels of magnesium as quickly as possible without damaging the heart. Intravenous administration of a magnesium solution is difficult in an animal with convulsions and is best done by your vet. Additional treatment involves injecting magnesium solution under the skin and allowing the animal to recover in a quiet environment.

    Risk factors

    • Grazing on lush pasture, especially if it has been fertilized with nitrogen or potash
    • Cows in early lactation
    • Bad weather or sudden change in pasture

    Prevention

    Magnesium compounds are effective but require daily administration e.g. daily drenching, adding the treatment to feed in the bail, spraying it on to hay, adding it to water or using magnesium blocks.

  • Polioencepholomalacia

    Polioencepholomalacia

      

    What to look for

    • Depression
    • A range of nervous signs - blindness, wandering aimlessly, excessive salivation and head pressing
    • A fine tremor of muscles may progress to convulsions
    • Death

    Cause - Thiamine deficiency

    Thiamine (vitamin B1) is usually produced in the rumen, but sometimes chemicals (known as thiaminases) break down the thiamine in the rumen. Thiaminases can arise from microorganisms that live in the rumen and it is also believed that ingestion of some plants may contribute to the problem. In some cases it is thought that an excessive amount of sulphur in the diet can cause changes in the rumen that limit thiamine production or availability.

    Animals likely to be affected

    Young animals between 6 - 18 months of age. Most cases involve recently weaned calves during the early summer months. Occasionally, adult animals are affected.

    Other diseases with similar signs

    Other diseases that cause nervous signs in animals include lead poisoning, salt poisoning, grass tetany, vitamin A deficiency and infection of the brain by microorganisms such as listeria.

    Confirming the diagnosis

    Diagnosis is made on the history of the outbreak, the clinical signs in affected animals and their response to thiamine. There are no routine laboratory tests for use in live animals but, if an animal dies, a post-mortem examination will reveal distinctive changes in the brain.

    Treatment

    Animals suspected of having PEM should be promptly treated by thiamine injections into the vein. The effect of this treatment is relatively short-lived and it needs to be repeated every few hours and followed up by treatment over the next few days. Animals treated early in the course of the disease have a reasonable chance of recovery but treatment of seriously affected animals is unlikely to be successful.

    Prevention

    PEM is not often seen and there is little that can be done to anticipate or prevent cases. If your farm is in an area where PEM occurs more often there may be some local information on plants that could be sources of thiaminases. If so, it may be worthwhile restricting access of susceptible animals to these plants.

  • Ketosis

    Ketosis

    What to look for - can cause a range of signs

    Wasting form:

    • Rapid loss of condition 2 -8 weeks after calving
    • Drop in milk yield
    • Poor appetite
    • Breath smells strange (like acetone) due to the presence of ketones

    Nervous form:

    • Incoordination
    • Strange behaviour e.g. sucking items in the environment, wandering aimlessly
    • May become aggressive

    Cause

    Ketosis usually occurs in early lactation when there is a huge increase in energy requirements for milk production and animals are unable to produce enough glucose. It can also be triggered at any time by another problem that causes inadequate feeding and/or a disturbance in metabolism, a condition known as secondary ketosis.

    Animals likely to be affected

    Cows in early lactation (from 2 to 8 weeks after calving). Occurs most often in cows in their 3rd to 6th lactations, but can occur in animals of any age if their diet is inappropriate or they are suffering from another serious illness.

    Other diseases with similar signs

    Any diseases that cause sudden weight loss and/or nervous signs e.g. grass tetany, lead poisoning, displaced abomasum or infections in internal organs.

    Confirming the diagnosis

    A simple urine or milk test can detect ketones but will not determine if the ketosis is secondary to another disease. Diagnosis of any underlying condition is important in these cases. Consult your vet to undertake an assessment of the animal and recommend appropriate action.

    Treatment

    Treatment of any underlying condition is important. To correct the energy imbalance, the aim is to increase blood glucose levels and provide nursing support for the animal over the next few days. Drenching with propylene glycol or glycerine may be useful, but drugs generally need to be injected into the vein so consult your vet as soon as ketosis is suspected.

    Risk factors

    • Inadequate feed supply in early lactation
    • Poor appetite caused by lameness, mastitis or other conditions
    • Unpalatable feed or poor quality silage
    • Left displaced abomasum

    Prevention

    Ensure that animals are well fed especially during the latter part of the dry period and in the early stages of lactation. Good feed management during the transition period will also reduce the risk of other diseases such as milk fever and grass tetany and improve production during the entire lactation.

    More information

    Transition feeding with limited effective fibre (PDF, 281KB)

    Around calving, the dairy cow undergoes a dramatic transition from dry and heavily pregnant to fully lactating. This is a stressful period for the cow and she is vulnerable to many problems and disorders that can affect her health and productivity. Feeding during the last 2-3 weeks before calving not only determines what happens to body condition at this time, but also provides an opportunity to prepare the cow for the coming lactation. Find out what you can do, including management tips and pre-calving diets with low DCAD.

  • Lead poisoning

    Lead poisoning

    What to look for

    Ranges from sudden death to nervous signs, weight loss and weakness.

    Signs depend on the amount and form of lead eaten by the animal In the more acute form:

    • Staggering
    • Depression
    • Blindness
    • Failure to eat
    • Changed behaviour and convulsions

    In the more chronic form:

    • Weight loss
    • poor appetite
    • Depression and a range of nervous signs

    Cause

    Ingestion of toxic amounts of lead

    Animals likely to be affected

    Most often seen in younger animals. Calves tend to be more curious and are more susceptible to poisoning, especially when on milk based diets.

    Other diseases with similar signs

    Can be confused with other causes of sudden death and also diseases that cause nervous signs such as grass tetany, listeriosis, polioencephalomalacia or ketosis.

    Confirming the diagnosis

    Lead poisoning may be confirmed by blood tests but these are not very reliable. In dead animals the lead levels in tissues can be determined and, in some cases, it may be possible to find lead particles in the rumen or reticulum.

    Risks to people

    People are also vulnerable to lead poisoning and care always needs to taken in handling lead sources especially in old buildings where lead-based paints may have been used.

    Treatment

    Animals may recover from lead poisoning if they receive veterinary treatment at an early stage. Young animals are less likely to respond to treatment.

    Risk factors

    • Animals have access to sources of lead e.g. discarded car batteries, lead flashing or pipes      
    • Housing calves in buildings with walls or woodwork painted with old lead-based paints

  • Tetanus

    Tetanus

      

    What to look for

    • Stiff movement
    • Over-reaction to sudden sounds or movements
    • Muscle spasms
    • Sudden death

    Cause - a bacterial infection (Clostridium tetani )

    This organism is widespread in the environment but only rarely causes disease in cattle. Tetanus usually occurs when an animal has had a penetrating wound, has been castrated or tail docked, or had a difficult calving. It can take days to weeks from receiving the original wound until the appearance of tetanus. The tetanus organism must enter the wound and be sealed off from the air before it can multiply. It then produces a powerful toxin that targets the nerves responsible for muscle movements.

    Animals likely to be affected

    Cattle of any age.

    Other diseases with similar signs

    Other diseases that cause sudden death. Young animals seen in the early stages of the disease might show similar signs to animals with polioencephalomalacia.

    Confirming the diagnosis

    The tetanic muscle spasms are usually characteristic enough to diagnose tetanus especially if there is a history of a deep wound in the last few weeks.

    Spread of the disease

    The disease does not spread from animal to animal but sometimes a number of animals may develop tetanus at the same time. This is usually because the animals have become infected at the same time following a procedure such as castration.

    Risks to people

    Take care when handling animals that are experiencing muscle spasms. People cannot get tetanus from direct contact with cattle, but are susceptible to infection with the tetanus organism through a penetrating wound. It is also important for all people that handle livestock to make sure that their tetanus vaccinations are up to date.

    Treatment

    If animals are seen early in the course of the disease and are particularly valuable, your vet may administer an antitoxin and recommend other measures that will save some animals. Treatment is not effective if animals are in an advanced stage of the disease.

    Prevention

    Ensure that all calves are protected against tetanus with a clostridial vaccine (5 in 1, 7 in 1 or 8 in 1). Use high levels of hygiene when performing procedures such as castration and dehorning.  

  • Listeria

    Listeria

      

    Listeria and Humans

    Listeria is common in the environment and poses a particular risk to vulnerable groups of consumers e.g. the elderly, the very young, pregnant women and those with compromised immune systems), so very strict control measures are followed to ensure Listeria species do not contaminate dairy products.

    Listeria and livestock

    What to look for 

    • Nervous signs - paralysis of muscles, restlessness and/or walking in circles
    • Fever
    • Pregnant cows may abort
    • Death may occur within 2-3 days

    Cause -“ a bacterial infection (Listeria monocytogenes)

    Listeria can cause serious disease in a wide range of animal species and in humans, but rarely causes illness in cattle. This bacteria is widespread in the dairy environment (in soil, water, feed) and survives in a wide range of conditions including poorly made or spoiled silage. There are no simple tests to identify feed that is contaminated by Listeria.

    Animals likely to be affected

    Listeriosis can infect cattle of any age but is most often seen in young adult cattle. It rarely infects animals under six months of age. If several animals have access to the same contaminated feed source there may be an outbreak of Listeria, but the disease does not generally spread from animal to animal.

    Other diseases with similar signs

    Other causes of abortion or nervous signs.

    Confirming the diagnosis

    A post-mortem examination will allow your vet to collect brain samples that can be examined at a laboratory for the characteristic changes caused by Listeria.

    Risks to people

    Most Listeria infections in humans result from eating contaminated food, but it is very important that people practice good personal hygiene when handling sick or dead animals.

    Treatment

    Antibiotics and other supportive therapies can be useful if Listeria is detected early.

    Risk factors

    • feeding poorly made or spoiled silage 

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