PATHOLOGY - Ovine Respiratory Disease Flashcards
What are the differential diagnoses for ill thrift in sheep?
Poor nutrition
Parasitism
Respiratory disease
Dental disease
Gastrointestinal disease
Lameness
Skin disease
What are the main respiratory diseases in sheep?
Chronic ‘cuffing’ pneumonia
Chronic suppurative pneumonia
Ovine pulmonary adenocarcinoma (OPA)
Maedi-visna
Laryngeal chondritis
Pneumonia pasteurelloisis
Which primary pathogens cause chronic ‘cuffing’ pnuemonia in sheep?
Mycoplasma, which is a commensal bacteria in the upper respiratory tract in sheep but can infect the lower respiratory treact and cause chronic ‘cuffing’ pneumonia
What are the clinical signs of the mild form of chronic ‘cuffing’ pneumonia?
Occasional cough
Tachypnoea
Decreased growth rate
How do you treat chronic ‘cuffing’ pneumonia in sheep?
Generally chronic ‘cuffing’ pnuemonia is self limiting however it can be treated with antibiotics, but be aware that the lesions are chronic so it will take a long time to reverse these lesions and clinical signs
What is the prognosis for chronic ‘cuffing’ pnuemonia?
Chronic ‘cuffing’ pnuemonia causes progressive, chronic disease and thus poor growth rates and decreased productivity, and can predispose to secondary infection
How do you prevent chronic ‘cuffing’ pnuemonia in sheep?
Good ventilation
Lower stocking density
Reduce stressors
Keep sheep healthy
What is chronic suppurative pneumonia in sheep?
Chronic suppurative pneumonia is abscessation of the lungs
What causes chronic suppurative pneumonia in sheep?
Chronic suppurative pneumonia has an unknown aetiology but it often the endpoint of ovine respiratory diseases in combination with secondary bacterial infection
Which bacteria are typically found if you culture ovine lungs with chronic suppurative pneumonia?
Fusobacterium necrophorum
Trueperella pyogenes
These bacteria species are found in the environement, indicating secondary infection rather than primary aetiology
What are the clinical signs of chronic suppurative pneumonia?
Weight loss
Repeated episodes of acute pneumonia
How can you diagnose chronic suppurative pneumonia in sheep?
Ultrasound (however this is very challenging)
Post mortem (PM)
How do you treat chronic suppurative pneumonia in sheep?
Culling
How can you prevent chronic suppurative pneumonia in sheep?
Good ventilation
Lower stocking density
Reduce stressors
Keep sheep healthy
Which pathogen causes ovine pulmonary adenocarcinoma (OPA)?
Jaaksiekte sheep retrovirus
Which breed of sheep is prone to ovine pulmonary adenocarcinoma (OPA)?
Scottish blackface sheep
What are the clinical signs of Jaaksiekte and ovine pulmonary adenocarcinoma (OPA)?
Weight loss
Progressive tachypnoea
Crackles on thoracic auscultation
Clinical signs of secondary bacterial infection
How can you diagnose ovine pulmonary adenocarcinoma (OPA)?
Wheelbarrow test
Ultrasound
Post mortem (PM)
What are the limitations of ultrasound for diagnosing ovine pulmonary adenocarcinoma (OPA)?
Ultrasound is not a very reliable diagnostic test for ovine pulmonary adenocarcinoma (OPA) as it can result in false negatives. Just because you don’t visualise a mass on ultrasound, doesn’t mean there definitely isn’t a tumour present or that the sheep hasn’t been infected by Jaaksiekte retrovirus, as this is a progressive disease
How do you treat ovine pulmonary adenocarcinoma (OPA)?
Cull affected sheep and offspring
Why should you cull the offspring of sheep affected by ovine pulmonary adenocarcinoma (OPA)?
You should cull the offspring of sheep affected by ovine pulmonary adenocarcinoma (OPA) as Jaaksiete virus is transmitted through close contact, especially to susceptible lambs. So, it is guaranteed that the virus has spread from mother to lamb and you need to prevent further disease spread within the flock
How do you control ovine pulmonary adenocarcinoma (OPA)?
Ovine pulmonary adenocarcinoma (OPA) is very challenging to control
What is Maedi-visna?
Maedi-visna is a viral infection which results in progressive, chronic disease, resulting in lymphatic infiltration of the tissues such as the lungs, udder, joints and nervous system
Which pathogen causes Maedi-visna?
Lentivirus
How is Maedi-visna transmitted?
Maedi-visna is transmitted orally, usually by ingestion of colostrum or milk containing lentivirus particles
What are the clinical signs of Maedi-visna?
Weight loss
Exercise intolerance
Progressive tachypnoea
Progressive dyspnoea
Mastitis
Arthritis
Neurological signs
How do you diagnose Maedi-visna?
ELISA
Post mortem (PM)
What is one of the limitations of the ELISA test for Maedi-visna?
There is a risk of false negative results if the animal has been recently infected as it can take up to 6 months for the antibodies to develop against lentivirus
How do you treat Maedi-visna?
Culling
How do you control Maedi-visna?
Regular ELISA testing of the flock and culling any ELISA positive animals and their offspring
Purchase replacement stock from accredited Maedi-visna free flocks
What is laryngeal chondritis in sheep?
Laryngeal chondritis is the abscessation of the arytenoid cartilages in sheep cause by bacterial infection
Which sheep are predisposed to laryngeal chondritis?
Terminal sire breeds, which at the moment are most commonly Texels
What are the clinical signs of laryngeal chondritis in sheep?
Inspiratory dyspnoea
Open mouth breathing
Cyanosis
How do you treat laryngeal chondritis in sheep?
High dose broad spectrum antibiotics and corticosteroids for 3 to 4 weeks
Emergency tracheotomy may be indicated
What are some of the less common causes of respiratory signs in sheep?
Dictyocaulus viviparus
Oestrus ovis
Tuberculosis
How does dictyocaulus viviparus infection differ in sheep compared to cattle?
Dictyocaulus viviparus is less pathogenic in sheep compared to cattle
