Signs of Worms in Sheep and Goats

All of the signs below can be associated with diseases other than from worms. If animals with any of the signs below are treated with a known effective drench and do not improve in 5–7 days, seek veterinary advice, as the signs may be due to another cause. Animals with a very severe worm infection may not recover, despite receiving an effective drench, if the infection is too far advanced.

Death

The dotted line shows the jawline, below that is swelling.

Bottle jaw (sub-mandibular oedema)

Swelling under the jaw results from both severe barber’s pole worm and liver fluke infections. The loss of blood results in anaemia and less protein in the blood. This imbalance in the normal body fluids results in fluid accumulating under the jaw in some, but not all, affected animals. It does not always occur during an outbreak of barber’s pole worm disease, and can also be caused by other factors (e.g. a severe lack of protein in under-nourished sheep).

Ascites (accumulation of fluid in the abdomen)

Abdominal swelling due to fluid occurs as a result of liver damage associated with liver fluke. Like bottle-jaw, it is the result of low protein in the blood causing body fluids to be out of balance and fluid builds up in the abdominal cavity.

Humped back from abdominal pain

Animals experiencing abdominal pain may stand with the back humped up. This occurs with acute liver fluke infection, associated with young fluke migrating through and damaging the liver. It is also frequent with nodule worm and can also be observed in conjunction with foul-smelling scours and weight loss as a result of coccidiosis. This should not be mistaken for a scour worm infection.

Coughing and pneumonia

The large lungworm infects the airways of sheep and goats and causes the production of a frothy mucus that will cause the animal to cough; there may also be a nasal discharge. In heavy infections pneumonia (inflammation and infection in the lung tissue) may be evident, accompanied by rapid breathing. Infection with the small lung worm rarely produces clinical evidence of disease in affected animals.

Anaemia

Barber’s pole worm is the only roundworm to cause anaemia (blood loss) as it sucks blood from the lining of the fourth stomach (abomasum). Feeding by fourth stage larvae and adults may remove 0.05mL of blood per worm. A burden of 1000 worms (seen as a worm egg count of about 5000 epg) may remove 50mL of blood per day from the sheep or goat.

Liver fluke also cause anaemia. The adult flukes localise in the bile ducts and damage blood vessels so they can feed on the blood.

Severe acute or ongoing (chronic) blood loss from either barber’s pole worm or liver fluke leads to obvious signs of anaemia. These are: pale gums and conjunctiva (inside the eyelids); lack of stamina causing lagging or collapse when mustered; and (ultimately) death from lack of red blood cells needed to carry oxygen around the body.

Lethargy and collapse

Lethargy or weakness can result from a severe infection of many worms. With scour worm infections it is associated with lack of energy and exhaustion, secondary to weight loss and decreased appetite. With barber’s pole worm infections, it is due to anaemia and the lack of red blood cells to carry oxygen required for muscle function. In either case, lethargy is most apparent when sheep or goats are being mustered, when individuals or a bigger group (‘a tail in the mob’) will fall behind the main mob. They may collapse and there is a risk of death if they continue to be pushed along and otherwise stressed.

NOTE: Where possible, the mob should be slowed down to allow weaker ones to keep up. Noise and pressure from bikes and dogs should be minimised. Transportable yards can be set up in the paddock for treatment of affected mobs. Animals that collapse are best treated on the spot with a drench and left to rest (you can carry a small bottle of drench and a syringe when mustering for such eventualities. Some drenches, especially those containing organophosphate [e.g. naphthalophos] are contraindicated for giving to unwell/ debilitated animals – always check the label.).

Weight loss from decreased appetite

An infection with scour worms results in a marked decrease in appetite and reduced metabolic efficiency. As a result, affected animals lose weight and with severe infections can become emaciated and ultimately die. Smaller worm burdens result in less wool and fibre grown, less muscle (meat) growth, and less milk produced by lactating ewes or does.

Liver fluke infection can also cause loss of appetite, especially with sub-acute infections.

Weight loss itself is not a consistent feature of a barber’s pole worm infections, however, animals may fail to gain weight.

Damage and inflammation of the gut resulting in diarrhoea (scouring)

The presence of scour worms initiates a strong immune response (stronger in sheep than in goats) from the host animal that damages the lining of the gut resulting in diarrhoea (scouring). The scouring results in a loss of protein from the gut and lowered absorption of nutrients, in turn this adds to weight loss and less wool or fibre growth (and milk production in ewes or does). With severe infections animals can become emaciated and die.

With severe brown stomach worm infections the lining of the abomasum becomes thickened and red.

Severe cases of black scour worms (in the small intestine) cause swelling of the intestinal walls with blood spots and excess mucus; nearby lymph nodes will also be enlarged. As the name suggests, the scours with these worms are a very dark colour.

This sign is typical for large burdens of scour worms (and coccidia, a protozoan organism), but does not occur with barber’s pole worm, flukes or tapeworms.

Hypersensitivity of the gut resulting in diarrhoea (scouring)

This is an allergic reaction of the gut to incoming scour worm larvae resulting in diarrhoea, even with relatively low levels of larvae. This differs from the gross damage to the lining of the gut due to a heavy burden of adult worms. Hypersensitivity typically occurs in the winter and spring months, in animals that have developed their adult worm immunity, and is most evident in mature animals.

In sheep in south-east Australia, scouring occurs in a large proportion of some flocks (30–40 per cent) every year, and may last for 3–4 months. In Mediterranean climatic zones, hypersensitivity scouring usually occurs after the relatively worm-free period of summer and autumn, after sheep are re-exposed to worm larvae. The occurrence between flocks and years varies considerably, and it generally lasts for only 4–6 weeks in a particular flock. There are marked differences between sheep, with some scouring badly and others very little; this is largely controlled by genetics and so selection against dag can reduce the problem.

The course of disease in goats follows that which is seen in sheep.

As with scouring due to large burdens of worms, this results in the wool or hair near the breech becoming coated with lumps of faeces (dags), which in sheep increases their susceptibility to flystrike.

This sign is typical for scour worms, but does not occur with barber’s pole worm, flukes or tapeworms.

Nodular lesions

Nodule worm: The larvae of nodule worms migrate through the walls of both the small and large intestines causing small gritty lesions in the wall of the small intestine or larger lesions with soft centres in the wall of the large intestine. These lesions render the small intestines unsuitable to be used for sausage casings. The larvae can migrate to other tissues, including the lung, liver and lymph nodes, causing nodules in these.

Brown stomach worm: Swellings are also evident in the fourth stomach (abomasum) of sheep or goats severely affected by brown stomach worm.

Small lungworm: Nodules form in lung tissue when sheep or goats are infected with small lungworm.

Jaundice

This is a yellow colour of the mucous membranes (gums, vulva and conjunctiva) and the skin resulting from damage to the liver and/ or excessive breakdown of red blood cells. Higher than normal levels of bilirubin (a waste product from the liver) accumulate in the blood stream. The yellow colouring is directly caused by bilirubin.

Jaundice occurs with liver fluke, due to increased red blood cell breakdown and damage to the bile ducts by the fluke. It can also be caused by other parasites and conditions, such as Eperythrozoon (Mycoplasma ovis).