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Diseases that
affect Rams


Preventable Diseases

Rams can be overlooked when it comes to disease prevention. They are the most expensive individual animal on the farm and their loss due to death or illness is not profitable. The ram is under high stress throughout joining and loses several condition scores. A compromised immune system is more likely to fail under disease pressure. Rams can be afflicted by the following diseases; Brucellosis, Clostridial Diseases, CLA, Erysipelas arthritis, Scabby Mouth, OJD and Internal Parasites.


Brucellosis, also known as ‘bruce-o’ is a bacterial disease that permanently infects the testes and epididymis of rams, rendering them infertile. It also temporarily infects the reproductive tracts of ewes, meaning that ewes can potentially spread the infection to uninfected rams. Rams also pick up infection from each other in the ram paddock.

Sheep brucellosis is practically incurable, so control of the disease relies on sound biosecurity and testing to eliminate infected animals.


Only purchase rams from vendors that are currently accredited free of brucellosis. Ask for copy of certificate.
Maintain sound fences that will prevent entry of stray rams or ewes that could spread the disease to your flock.
Have rams checked by an accredited veterinarian each year to ensure they have not become infected (3 months prior to mating).

Brucellosis accreditation program

Each state Dept of Primary Industries oversees a scheme to provide ram producers with accreditation to show that the farm is free from brucellosis. This involves inspection and blood tests carried out by a private veterinarian. Every ram is manually palpated and blood tested twice. All rams must pass with negative blood and physical tests before accreditation is given, then re-accreditation testing takes place after 12 months then biannually.


Corynebacterium pseudotuberculosis

This is a chronic disease characterised by the formation of abscesses in the lymph nodes. Infection enters the flock by a carrier animal with shearing being the primary risk factor. Control relies on the elimination of the source of infection by culling all sheep with enlarged lymph nodes, preferably at shearing when palpation is easier. Using a 3in1 or 6in1 vaccine will reduce the number of sheep that develop abscesses.

Highly contagious bacteria that is spread via respiratory exhalation or transmission of ruptured fluids

CLA is a hidden disease affecting the major internal body organs and both the internal and external lymph nodes in sheep

The bacteria release a toxin, which damages the lymph node/organ and causes an abscess to form

Over time, the pus-filled abscess reorganises to form the characteristic Caseous abscess or “Cheesy Gland” 

Cheesy Gland

CLA Stat 1

CLA Stat 2


Erysipelas rhusiopathiae

Erysipelas arthritis is the inflammation of one or more joints which causes lameness and visible swelling of joints in the legs. Lambs will most likely become infected at mulesing when the lamb’s mother licks the wounds, at shearing via cuts, soon after birth or at marking. As an animal welfare consideration, animals that remain chronically lame should be humanely destroyed. The condition can be prevented by vaccinating ewes before lambing and avoiding shearing or mulesing lambs in wet and muddy conditions.


Erysipelas spp. soil borne bacteria enters via the umbilical cord or wounds then localises in leg joints causing inflammation and lameness

Results in death of young lambs through ill thrift and lame lambs

Increased tail in the flock, unsaleable or untransportable animals and general animal welfare concerns

Causes carcass trimming and full condemnations at the abattoir

Economic impact of lower lamb numbers, chronic arthritis in ewes/rams, and lost meat yield

Arthritis Stat 1

Arthritis Stat 2

Ovine Johne's Disease

Mycobacterium avium subsp. paratuberculosis

OJD is an incurable bacterial disease that infects intestines of sheep and goats, causing the intestinal walls to slowly thicken reducing absorption of nutrients

There is a production loss and reduced feed conversion efficiency from the initial infection leading to severe weight loss and death

OJD is widespread and expanding endemic disease

Lambs can contract OJD from when they start grazing and risk increases over time

The annual ewe death rate can be 2% on low prevalence farms and up to 30% on heavily infected farms5


OJD Stat

Scabby mouth


This is a highly contagious viral disease that infects sheep through abrasions in the skin. This condition is particularly problematic in live export sheep where close confinement of animals and feeding of hard pellets and/or hay causes minor abrasions along the mouth and lips. The recommended program is to vaccinate each year’s drop of lambs. This can be done at marking and will provide protection for 12 months.

Scabby Mouth

Scabby mouth is highly contagious

Scabs from infected sheep are major source of virus. Infection from environment/contact with infected sheep

Most commonly affects lambs in first year of life but also can occur in older sheep

Grazing of thistles, coarse pastures or stubbles may predispose to infection with Scabby Mouth as oral abrasions increase the potential for the virus to gain entry

Severely affected lambs unable to feed with loss of condition and depressed growth rates and market challenges

Selenium Deficiency

Selenium deficiency can be severe, resulting in white muscle disease or sub clinical symptoms, causing reduced productivity and low conception rates

Selenium deficient areas are found Australia wide

Selenium deficiency will be more pronounced as a result of rapidly growing, clover based pastures in high rainfall areas


Cobalt Deficiency


Vital for energy production and body and wool growth

Rapidly-growing sheep have the highest demands
    • pregnant ewes
    • lactating ewes
    • lambs
    • weaners
Levels of Vitamin B12 in sheep are dependent on ingestion of cobalt

Cobalt deficiency depends on soil type, but can also occur in rapidly growing pastures

Pulpy Kidney Stat


Clostridium perfringens type D

High levels of starchy foods or anything that causes gut movements to slow will predispose sheep to this condition. Death can occur within 2-3 hours. Exercise and additional roughage can help to prevent the disease.

Pulpy Kidney Disease is a naturally occurring bacteria that is found in the gut of healthy animals as well as in the soil and faeces Australia wide

Pulpy Kidney Disease is caused by a modification in the rumen conditions due to a sudden feed change, resulting in a rapid multiplication of these bacteria and production of the Epsilon toxin that is absorbed into the blood

Multiplication results in an overwhelming toxin level

Sudden death is the result

Pulpy Kidney


Clostridium tetani

Predisposing factors to tetanus include: use of rubber rings for marking and shearing wounds. Signs appear 3-10 days after injury in lambs and present as body stiffness, muscular spasms, and protrusion of the third eyelid. Special attention needs to be given to hygiene at marking as well as pre-lambing boosters of clostridial vaccine.


Tetanus is a naturally occurring bacteria that is found in the soil, Australia wide

Tetanus spores enter the body via a wound due to husbandry procedures and accidental wounds

Tetanus bacteria produces a neurotoxin that causes prolonged muscle spasms, resulting in death due to the paralysis of the breathing muscles

Sudden death is the usual result

Black Disease

Clostridium novyi type B

Black disease is a naturally occurring bacteria that is found in soil and gastrointestinal system, found Australia wide

Black Disease spores enter the body after ingestion, pass through gastrointestinal wall and deposits in liver and other tissues

Black disease occurs when the liver is damaged, which provides ideal conditions for the spores to germinate, multiply, secrete toxin and produce signs of the disease

Liver fluke larvae are a common cause for the liver damage

Sudden death is the result

Black Disease


Clostridium chauvoei


Black Leg Disease is a naturally occurring bacteria that is found in soil Australia wide

The spore is ingested by animals whilst grazing, can live in the GIT or can enter the bloodstream then lie dormant in the muscle 

Bruising, trauma or wounds triggers the spores to germinate, multiply, secrete toxin and produce signs of the disease

The toxins affect local tissues with death of tissue with gaseous, gangrenous presentation and toxic death of organ tissue

Sudden death is the usual result

Malignant Oedema

Clostridium septicum

Malignant Oedema is a naturally occurring bacteria that is found in soil Australia wide

Malignant Oedema spores enter the body from soil contamination of open wounds

These wounds can be caused by husbandry procedures and accidental wounds include the navel of lambs, head of fighting rams and marking wounds 

The spores germinates in the wounds, multiply, secrete toxins and produces signs of the disease

Sudden death is the result


Internal parasites

Rams spend large periods of the year in paddocks with high stocking density that have high levels of parasite larval contamination. This leads to damaging worm burdens, typically double those seen in the rest of the flock.

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Worm egg counts

Fresh faecal samples can be taken off the ground from a representative number of rams (preferably 15 head) and submitted for faecal worm egg counts.

Drench tests

By doing faecal egg counts before and at day 14 after treatment with a drench, the efficacy of the treatment can be calculated (i.e. the percent of worms killed by the drench). Only drenches with high efficacy (>95%) should be used.

Internal parasites Statistic


Avoid disturbing rams 6 weeks prior to joining during the critical spermatogenesis period
Do drench tests to check which drenches are effective against the target worms on your property
Conduct worm egg counts 6-12 weeks prior to joining and drench rams to ensure they are not affected by worms

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Sheep Internal Parasites & Best Practice Worm Monitoring


  1. Paton MW, et al. Prevalence of Caseous lymphadenitis and usage of Caseous lymphadenitis vaccine in sheep flocks. AVJ 2003; 81(1&2): 91–95.
  2. Meat and Livestock Australia. Priority list of endemic diseases for the red meat industries. Published March 2015. Project code B.AHE.0010.
  3. Meat & Livestock Australia Limited, National Trade Lamb Indicator at $5.75 per kg ctw, May 2015
  4. Pattinson, R; Wilcox, C; Williams, S; Curtis, K. NSW Wool Industry & Future Opportunities 2015
  5. Evers J, Watt B (2007) High OJD mortality in the unvaccinated portion of a merino flock. Flock & Herd
  6. Pattinson, R; Wilcox, C; Williams, S; Curtis, K. NSW Wool Industry & Future Opportunities 2015

Further Reading

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