is of considerable economic importance to the sheep industry
causing septicaemia in young lambs, pneumonia in older sheep, and
mastitis in ewes.
Clinical signs in adult sheep
The clinical signs
include acute onset depression, lethargy and inappetance. Affected
sheep typically become separated from the remainder of the group.
They show an increased respiratory rate with an abdominal component
and a fever (>40.5°C). In some
situations, the animal is found dead.
Fig 1: Sheep
with pasteurellosis are typically separated from the remainder of
the group, and do not eat and appear very dull with ears
Figs 2 and 3 The clinical signs of acute
pasteurellosis in adult sheep include sudden onset depression and
The lungs are heavy, swollen
and purple-red in sudden cases, and the airways contain
Fig 4: The lungs
are heavy, swollen and purple-red in sudden death cases caused by
Diagnosis of respiratory
disease caused by M. haemolytica is based upon clinical
signs but there is no confirmatory test in the living sheep.
Confirmation of diagnosis is made at necropsy with
histopathological examination of lung lesions and
A good treatment response to
antibiotic therapy necessitates rapid detection of sick sheep by
shepherds. Oxytetracycline is the antibiotic of choice for
pasteurellosis as there are few antibiotic resistant strains in
Prevention is best attempted
using vaccines incorporating iron-regulated proteins. Breeding ewes
require a primary course of two injections four to six weeks apart
followed by an annual booster four to six weeks before lambing.
However, this vaccination regimen only provides passive immunity to
the lambs for up to five weeks. Lambs can be protected by two doses
of vaccine administered from 10 days-old as colostral antibody does
not interfere with the development of active immunity.
Prevention is best attempted using vaccines incorporating
The low cost of vaccine (ca.
25 pence per dose) should permit vaccination of all susceptible
A non-progressive chronic
pneumonia of housed sheep under a year-old caused by Mycoplasma
ovipneumoniae, and possibly other organisms (Parainfluenza 3
virus and Chlamydia psittaci). The true prevalence of this
disease is unknown because the clinical signs are mild and do not
generally warrant veterinary investigation.
The significant clinical
finding is one of slightly reduced growth rate despite an
appropriate ration. A chronic soft cough and nasal discharge
spreads slowly through the group most noticeable when the sheep are
Lung changes are usually only
detected at the abattoir and consist of red-brown or grey collapsed
areas in the apical and cardiac lobes.
Fig 6: Lung
changes are usually only detected at the
Treatment is generally not
necessary because clinical signs are mild. Oxytetracycline should
be given to sick lambs which are not eating.
Control can be attempted by
improving ventilation and reducing the stocking density. The
airspace should not be shared with older sheep. Purchased lambs
should be housed separately from homebred stock.
Fig 7: Control
of enzootic pneumonia can be attempted by improving ventilation,
and reducing the stocking density.
Lungworm may cause coughing
and weight loss in heavy infestations but this is very uncommon.
Relative to parasitic gastroenteritis, lungworm infestation is of
no economic significance to sheep farmers.
Treatment for lungworm is not
necessary as their control can effectively be achieved by regular
anthelmintic treatments used in the management of parasitic
gastro-enteritis. Severe lungworm infestations are often seen in
sheep with paratuberculosis (Johne's disease) due to compromise of
the immune system.
Fig 8: Severe
lungworm infestation in sheep with paratuberculosis (Johne's
Chronic suppurative pneumonia/lung
Lung abscesses are very
common in mature rams but are difficult to identify by inspection
alone and veterinary investigation is essential to establish an
accurate diagnosis. Chronic respiratory disease is a very important
disease in breeding rams which is all too frequently overlooked or
Fig 9: Lung
abscesses are very common in mature rams but are difficult to
Sheep with significant
chronic lung lesions present with a history of weight loss although
appetite may appear normal. The rectal temperature is often
slightly elevated (up to 40.0°). At rest,
affected sheep have a higher respiratory rate compared to normal
sheep in the group, and cough occasionally. There may be an
occasional purulent nasal discharge.
Veterinary examination is very important to diagnose lung
Veterinary examination is
very important, not least because the patient is likely to be a
valuable breeding ram. Penicillin is the antibiotic of choice for
chronic respiratory disease. A three to four week treatment regimen
for treating valuable breeding stock with multiple pleural and
superficial lung abscesses identified by ultrasonographic
examination has produced encouraging results. A single long-acting
injection of oxytetracycline will not work.
The common finding of lung
abscesses in mature rams is probably related to long periods of
housing after birth and during their first winter. Viral infections
(see enzootic pneumonia above) are common during such times, and
such lesions may become infected with bacteria causing abscesses.
Failure to recognise and treat early lesions allows these abscesses
to grow into significant structures. Weight loss during the mating
period causing debility may render rams more prone to infection or
exacerbate existing pathology.
Fig 11: Weight
loss during the mating period causing debility may render rams more
prone to infection
Fig 12: Adequate supplementary feeding is essential
during the mating period to maintain health.