3.1: Respiratory disease in cattle Flashcards
Taken from BRD lectures and workshop (10/10/2022)
Bovine respiratory disease
general term for respiratory disease in cattle, covering various pathogens/environmental/management factors.
Main BRD pathogens: viruses
- IBR
- RSV
- PI3
Main BRD pathogens: bacteria
- Mycoplasma bovis
- Mannheimia haemolytica
- Pasteurella multocida
- Mycobacterium tuberculosis
- Histophilus somni (more common in N. America
Causative agent of IBR
Bovine herpesvirus 1 (BHV-1)
* An alpha herpesvirus of which there are several strains
Epidemiology of IBR
- Highly infectious and contagious
- Endemic in the UK; approx. 40% of cattle have been exposed
- Latency is possible with recrudescence and shedding around periods of stress e.g. calving, movement, illness, corticosteroid use
Incubation period of IBR
2-20 days
Transmission of IBR
- Highly infectious and contagious
- Spread by aerosol - shared air space for a sustained period required
- Spread by direct contact including nose-to-nose contact over fences
- Present in resp tract secretions, bull semen, aborted foetuses
- Can be transmitted by sheep and goats
Clinical signs of IBR
- Resp signs: tracheitis, harsh URT signs
- Nasal discharge
- Ocular signs: epiphora, conjunctivitis
- Pyrexia (40+)
- Can cause abortion (up to 100 days) and genital lesions
IBR typically causes respiratory signs in which groups of cattle?
- Typically affects cattle >6 months of age but can be younger
- Often worse in growing age groups (6-24 months)
Describe signs of subacute IBR
Signs are vague and non-specific
* Milk drop sometimes at herd level
* Pyrexic (40=/+)
* Nasal discharge
* Hyperpnoea
Describe signs of acute IBR
- Seen in growing cattle
- Marked pyrexia ± secondary infection
- Purulent nasal discharge
- Marked conjunctivitis
- Large submandibular LNs
- Tracheitis (audible as rattling over the trachea)
True/false: IBR and IPV are caused by the same pathogen.
True.
Both Infectious Bovine Rhinotracheitis and Infectious Pustulo Vulvovaginitis are caused by BHV-1
Signs of peracute IBR
- Very high fever and death in 24hrs
- Secondary bronchopneumonia
Black tarry lining of trachea - very indicative of IBR
Mortality in IBR
Up to 10% in younger animals; rare in adults
Diagnosis of IBR
History, clinical signs, and swabs/antibody test
* History: new animals/grous into herd
* Clinical signs: in several animals
* Nasal and conjunctival swabs -> Virus on PCR
* Paired blood samples from acute cases -> rising titres on ELISA antibody test
* Bulk milk anitbody test to monitor exposure of herd
Control options for IBR
- Do nothing - if a few mild cases expected to be self-limiting
- Vaccination: different protocols available
- Biosecurity: prevent nose-to-nose contact, double fence at boundaries
- Buying in stock: avoid if you can, use CHeCS accreditation schemes, quarantine and test new animals
What are the different levels of CHeCS IBR accreditation?
Which level is it advisable to buy at?
- Accredited free - safest
- Vaccinated/monitored free
- Eradication programme
You should buy at the same level as your current herd.
If good -> bring in only IBR free animals.
If not so good -> don’t want to bring in naïve animals
What are the different types of IBR vaccine? Which would you use in the face of an outbreak?
- 2 types: live vs inactivated
- Live vaccines are used in the face of an outbreak. Some evidence that they are more effective overall.
True/false: most vaccines for IBR are marker vaccines.
True
This allows differentiation between vaccinated and naturally exposed/infected animals.
Useful when attempting to eradicate disease.
Both live and inactivated vaccines can be marker vaccines
Which IBR vaccine type is most appropriate for a herd where disease is endemic?
Inactivated - it is better at reducing shedding than a live vaccine.
True/false: some IBR vaccine protocols combine live and inactivated forms of the vaccine.
True
Many start with the live vaccine, then move on to the inactivated form.
Provide some examples of IBR vaccines (trade names)
- Bovilis IBR (MSD)
- Rispoval IBR (Zoetis)
- Hiprabovis (Hipra)
What is the causative agent of Malignant Catarrhal Fever?
- OvHV-2
- This is carried by sheep without causing them to show clinical signs
Describe the epidemiology of MCF in cattle
- Disease is usually sporadic, affecting a small number of animals rather than an entire herd
- Outbreaks have been recorded but are rare
Transmission of MCF
- Methods of transmission: by aerosol, direct contact, contaminated feed/water/bedding
- Cattle cannot pass MCF to other cattle. They have to get it from a sheep
- Stress may increase shedding by sheep e.g. shearing, lambing
What important piece of information from the history can tell you if cattle may be at risk for MCF?
Any history of exposure to sheep
True/false: deer and bison can carry MCF asymptomatically
False
MCF kills deer and bison and is a major problem for these industries.
Clinical signs of MCF
- Pyrexia
- Enlarged LNs
- Mucopurulent nasal and ocular discharge
- Corneal opacity
- Sloughing of oral and nasal mucosa
Treatment and control of MCF
- Testing is available: antibodies/virus PCR
- Almost always fatal: no licensed treatment or vaccines
- Euthanasia is usually best option
Malignant catarrhal fever (MCF)
* Can see corneal opacity and mucopurulent nasal discharge
Malignant catarrhal fever (MCF)
* Image shows severe sloughing of nasal mucosa
Malignant catarrhal fever (MCF)
What is the incubation period for Respiratory Synctial Virus?
- Incubation: 2-5 days
What is the incubation period for Respiratory Syncytial Virus?
Incubation: 2-5 days
Describe the pathology caused by RSV
- Necrotising bronchiolitis
- Diffuse interstitial pneumonia
- Severe bullous emphysema
- Emphysematous lesions typically in the caudo-dorsal lung lobes
Clinical signs of BRSV
BRSV = RSV (there is a human version which is different)
* Pyrexia
* Depression
* Decreased feed intake
* Increased RR
* Cough
* Nasal and lacrimal discharge
* Dyspnoea and potentially open-mouthed breathing in later stages
Diagnosis of RSV
- Hard to isolate - may manage to get PCR
- Paired serology demonstrating a rising titre
Treatment of RSV
- Centres on antimicrobial therapy to control secondary bacterial infections
- No specific treatment for viral interstitial pneumonia: supportive therapy
Which animals are typically affected by RSV?
- Young naïve animals
- Can affect cattle, sheep and goats
True/false: this calf is happy :)
False!!!
* Outstretched neck, open-mouthed breathing and froth around mouth = severe respiratory distress
* This calf had RSV
Severe bullous emphysema from a calf with RSV
* There is oedema in the cranial lobes, bullae in the right caudal lung lobe, and interlobular emphysema
Describe the clinical features of PI3
Parainfluenza 3
* RNA virus
* Virus has similar features to influenza in humans
* Highly contagious
* More likely in stressed animals
* Key role as an initial that leads to the development of secondary bacterial pneumonia
Clinical signs of PI3 infection
- Pyrexia
- Cough
- Serous nasal and lacrimal discharge
- Increased RR
- Increased breath sounds
- Severity of signs worsen with the onset of secondary bacterial pneumonia
Treatment and control of PI3
- Antimicrobial therapy for any secondary bacterial pneumonia
- NSAIDs and supportive care
- Vaccines available: often combined in IBR vaccine
Describe the epidemiology of bTB
- 25 year eradication strategy with 3 management zones (High, edge, low risk)
- Reservoirs of infection: badgers, deer, ferrets, infected cattle
- Infection is often latent for a variable time period
- Mycobacteria can be killed by sunlight but otherwise quite resilient to desiccation, acids and alkalis.
- Can survive for 6-8 weeks on pasture
Routes of infection for bTB
- Ingestion (e.g. on pasture where wildlife reservoir present)
- Inhalation (when housed)
- Excreted in urine, sputum, faeces, milk, exhaled air, vaginal and uterine discharge
Major routes of transmission for bTB
- Cattle to cattle spread: mainly through inhalation when housed (aerosol infectious dose = low). Sometimes to calves through infected milk. False -ves at SICCT allow infected cattle to slip through.
- From infected badgers: e.g. through mineral licks. Can use genetic fingerprinting (spoligotypes) to identify if badgers and cattle infected with same strain.
Clinical signs of bTB
- Testing is such that clinical disease hardly ever seen; disruption of testing (FMD) may lead to this
- Soft, product cough -> worse at exercise/if pharynx palpated
- Weight loss
- (sometimes) LN enlargement
- Sometimes mastitis with udder induration
- Some forms are generalised/affect GIT specifically
Pathology of bTB
Rarely seen in UK
* Emaciation
* Chronic cough
* Dyspnoea
* Swelling of submaxillary, retropharyngeal, prescapular, supramammary, mastitis
True/false: bTB is zoonotic and notifiable.
True.
Acute bronchointerstitial pneumonia in a calf infected with PI3
Granulomatous inflammation associated with bTB
Methods of testing for bTB
- SICCT
- Blood testing: antibody, IFN gamma
- PM inspection
When might an IFN gamma test be commissioned?
- When a herd is having continuous TB breakdowns on SICCT
- SICCT may be missing positive animals -> never quite get on top of it
- IFN gamma is more sensitive than SICCT -> can cause false positives, but hopefully allows proper clearout of missed cases
Treatment and control measures for bTB
- BCG vaccine currently licensed for use in badgers; won’t cure, but will reduce shedding
- BCG cattle vaccine and DIVA test currently undergoing UK market authorisation
- Biosecurity: wildlife proof fencing, secure feed storage, raised feed troughs and mineral licks
- Store slurry for long periods before use and at least 2 months before grazing; do not spread anyone else’s slurry/share equipment
- Risk based trading: pre and post movement testing
Causative agent of Contagious Bovine Pleuropneumonia
Mycoplasma mycoides
True/false: Contagious Bovine Pleuropneumonia (CPBB) is endemic in the UK.
False.
It has been eradicated from the UK and is notifiable.
It is theoretically on the ddx list if you see pyrexia and respiratory dz.
True/false: Mycoplasma bovis is commonly seen as a sole pathogen in a cow with pneumonia.
False
* Mycoplasma bovis can be a sole pathogen but is more commonly seen in combination with other pathogenic respiratory bacteria, viruses or parasites
Describe the pathology seen in Mycoplasma bovis infection
- Caseonecrotic pneumonia (see image)
- Classic sign in calves: otitis media producing a head tilt
- Polyarthritis
- Contagious mastitis that is very hard to get rid of
How does Mycoplasma bovis spread through and persist in the animal?
- Haematogenous spread within the animal -> it does not just stay in the respiratory tract
- It is an intracellular pathogen so immune system/drugs may struggle to reach it
- The bacterium produces a biofilm which aids survival in the environment and within the host
What type of bacteria is Mycoplasma bovis?
Gram positive with no cell wall
How is Mycoplasma bovis transmitted?
- Direct contact: it is shed in respiratory tract secretions
- Close contact via a fomite e.g. teat feeders
- Aerosols
- Can be shed in milk, possibly transmitted in utero
Clinical signs of Mycoplasma bovis infection
- Chronic pneumonia (may also present acutely) with a hacking cough
- Conjunctivitis
- Head tilt
- Ear droop
- Head shake
- Arthritis
- Mastitis
- Abortion
Diagnosis of Mycoplasma bovis infection
- Serology from joint tap/milk
- PM
Treatment and prevention of Mycoplasma bovis infection
- Emerging resistance to tetracyclines and macrolides (remember - no cell wall so amoxicillins ineffective)
- No commercially available vaccine in the UK
These images show clinical signs associated with…
Mycoplasma bovis infection
What type of bacteria are Mannheimia haemolytica and Pasteurella multocida? Are they pathogenic/commensal?
- Gram negative aerobic bacteria
- Both can be commensals of the URT
True/false: Pasteurella multocida is more likely to be a secondary invader than a primary cause of disease.
True
It is most likely to be a secondary invader.
True/false: disease caused by Mannheimia haemolytica tends to be more severe than that caused by Pasteurella multocida
True.
True/false: in any cattle farming operation, identifying the primary cause of respiratory disease is highly important and must be prioritised.
False
Sometimes finding the primary causative agent is desired, BUT:
* Pathogen hunts are not guaranteed to provide results or be the best use of money and time
* Respiratory disease often involves multi-pathogen infections
* Many treatment and control measures will be similar across different pathogens
* Consider management/environmental factors that need addressing
True/false: Mannheimia haemolytica can be a primary cause of respiratory disease or a secondary invader.
True.
Fog fever
Acute bovine pulmonary oedema and emphysema
Pathogenesis of fog fever
- Fog fever = nutritional resp disease caused by ingestion of L-tryptophan
- (L-tryptophan is found in lush grass/mouldy sweet potatoes)
- L-tryptophan is ingested and metabolised to 3-methylindole by rumen bacteria
- 3-methylindole is pneumotoxic, damaging Type 1 ciliated cells and Clara cells
- There is pulmonary oedema and epithelial hyperplasia
Clinical signs of fog fever
- High mortality rate (up to 30%)
- Animals often found dead
- Severe respiratory distress without coughing or pyrexia
Differential diagnoses that might also be on your list if you suspect fog fever
- Lungworm
- RSV
Diagnosis of fog fever
- Based on history of movement of cattle from dry, sparse pasture to lush pasture
- Definitive diagnosis on pathology
Treatment and prognosis for fog fever
- No specific treatment
- Palliative therapy, minimise stress
- Prognosis is guarded with up to 30% mortality
Prevention of fog fever
- Introduce cattle to lush pastures slowly
- Feed palatable hay/silage prior to turnout to allow gradual diet change
- Graze youngstock rather than adults on lush pastures as they seem to less susceptible
Post mortem findings: fog fever
- Pulmonary oedema, alveolar epithelial hyperplasia, emphysema
- Ecchymotic/petechial haemorrhage in larynx, trachea, bronchi
- Frothy fluid in airways
- Congestion/oedema in the lungs: lungs appear wet/shiny due to oedema, and fail to collapse when the thorax is opened
