Case Study - Bovine Medicine

Phil Scott DVM&S CertCHP DSHP FRCVS
Phil Scott has 33 years’ experience of farm animal practice and is an European specialist in both small ruminant (DipECSRHM) and cattle health and production (DipECBHM). He was awarded an FRCVS in 1994 for studies on Bovine Spongiform Encephalopathy (BSE) and a doctorate for studies on perinatal lamb mortality from the University of Edinburgh in 1993. He is the author of over 150 peer-reviewed articles and three veterinary textbooks. He regularly contributes to regional and national farming magazines via articles franchised through the national animal disease information service (NADIS).

What conditions cause poor milk production several weeks after calving in a Holstein heifer, and what investigations could you undertake on farm, and later in the practice laboratory?

Case history
During September a home-bred Holstein heifer presents with a five days' history of poor appetite and is yielding only 16 litres of milk per day. The heifer produced a live calf following traction using a calving aid two weeks previously and the foetal membranes were retained for three days. The in-calf heifers had been at pasture until calving and are housed after calving with the main herd and fed a TMR.
The bulk milk tank figure has not fallen significantly during the past two weeks. The herd is closed and no lungworm vaccine is used. The in-calf heifers were grazed on rented pasture (grazing history of the rented pasture is unknown). No other heifers in the group are affected.

Clinical examination
The heifer is dull and depressed with a slightly arched back, and is slow to move (video recording). The rectal temperature is 39.2⁰C. There is an occasional slight purulent nasal discharge (Fig 1). The heart rate is 60 beats per minute. The respiratory rate is 32 breaths per minute. Auscultation of the chest reveals wheezes in the ventral half of the lung field.

The heifer is dull and depressed with a slightly arched back, and is slow to move.

Video recording 1

Audio recordings

The heifer has a soft productive cough. The ruminal contractions are normal occurring once per minute. The vulva is swollen and odematous and there are two 3-4 cm diameter diphtheritic plaques visible just inside the vagina which bleed readily when touched. There is scant muco-purulent vaginal discharge. Rectal examination reveals the uterus extending over the pelvic brim. There is no evidence of mastitis and the heifer is not lame.

Fig 1 There is an occasional slight purulent nasal discharge

The farm has a history of respiratory disease in calves due to overcrowding of old buildings and reluctance by the farmer to use respiratory vaccines. The approach to suspected respiratory disease has been to treat all calves in the group with a single long-acting antibiotic injection when several are coughing and not eating their concentrates. No monitoring of antibiotic therapy is undertaken and further treatments are considered by the farmer to be unnecessary because all the calves have been treated.

What is the most likely cause of the heifer's condition:
Feedback:
CSPD is the most likely diagnosis (fever, nasal discharge, cough, reduced appetite and milk yield, possible thoracic pain) but parasitic bronchitis (cough, poor production, possible exposure at grazing, time of year) cannot be excluded on clinical examination and further laboratory testing is necessary even though only one heifer is affected at present. Auscultation of the chest is unreliable to diagnose the nature and extent of CSPD.

While the herd is closed, the heifers are not vaccinated against lungworm and were grazed on rented pasture with an unknown history.

IBR can result when susceptible animals are introduced into the herd but more than one heifer is likely to be affected, higher rectal temperature, often have ocular discharges.

Fig 2 Cattle with IBR often have ocular discharge and inflamed conjunctivae.

Pleural abscess(es) is a possible diagnosis but would expect corresponding area(s) of much reduced/absent lung sounds on auscultation.

Other diseases that could be considered include:
- Metritis
- Liver abscessation/hepatocaval thrombosis
- Traumatic reticulitis
- Endocarditis
- Subacute ruminal acidosis
- Bluetongue
but these conditions would be largely excluded during the clinical examination.

It may be prudent to check the BVD status of the heifer depending upon the herd history, vaccine usage, and effectiveness of the biosecurity measures.

Fig 3 Hepatocaval thrombosis affecting a Holstein heifer. It is unusual to see evidence of frank arterial blood at the nostrils except when there is significant (often fatal) haemorrhage.

Fig 4 Hepatocaval thrombosis affecting a Holstein heifer (see above) showing frequent coughing.
- Chronic suppurative pulmonary disease (CSPD)
- Parasitic bronchitis
- Pleural abscesses
1. Infectious bovine rhinotracheitis
Clinical Examination
Which of the following samples would you collect to assist you in your clinical examination?

Feedback:
Faecal samples for worm egg counts (McMaster technique) would be undertaken at this time of year to help diagnose type I ostertagiosis infestation. Clinical signs include rapid onset profuse diarrhoea not respiratory disease signs. Lungworm infestation is based upon the presence of L1 larvae and not eggs.

The Baermann test can be set-up overnight in the practice (Fig 5) to check for the presence of L1 larvae of Dictyocaulus viviparus (Fig 6). While only one heifer is affected from the group: it is the correct time of year for lungworm, the heifers are not vaccinated, and there is the unknown risk from the rented pasture.

Fig 5 The improvised Baermann test set-up overnight in the practice to check for the presence of L1 larvae of Dictyocaulus viviparus.

Fig 6 L1 larvae of Dictyocaulus viviparus (see above).

Nasal swabs are likely to grow the usual respiratory tract commensal organisms and this information is rarely of any clinical assistance.

Routine haematological examination in this heifer revealed a total red blood cell count of 4.1 x1012/l, (normal range 5-9 x1012/l), leucocytes 12.4 x109/l (normal range 4-10 x109/l) with 65% neutrophils. Serum albumin and globulin concentrations were 24.8 g/l (normal range 30-40 g/l) and 61.3 g/l (normal range 35-45 g/l) respectively. These results reveal a mild anaemia consistent with chronic inflammatory focus. There is a slight leucocytosis resulting from a marginal neutrophilia. The changes in the serum albumin and globulin concentrations are consistent with chronic severe antigenic stimulation (e.g. bacterial infection) somewhere in the body but do not localize the infection.
- Faecal sample for worm egg count (McMaster technique)
- Faecal sample for L1 larvae (Baermann test)
- Nasal swab for bacteriology
- Blood sample for routine haematology
Diagnostic Tests
What further cost-effective tests could be undertaken on farm?

Feedback:
Auscultation of the chest is unreliable and diagnosis of CSPD necessitates real-time B-mode ultrasonographic examination of the chest with a 5 MHz sector scanner although linear array scanners can be used.

Diagnostic radiographs of the antero-ventral area of the chest are difficult to achieve in adult cattle. There are health and safety issues to be considered, as well as cost.
- Chest radiography
- Broncho-alveolar lavage and bacteriology
- Chest ultrasonography
- Fine needle aspirate of area(s) of increased lung sounds
Interpret the sonographic findings taken at the fifth and sixth intercostal spaces (Figs 7-9). The sonographic findings shown in Figs 8-9 are typical of which of the following diseases?

Fig 7 Sonographic findings dorsally at the sixth intercostal space. The probe head is at the top of the image, dorsal to the left.

Fig 8 Sonographic findings 5 cm above the point of the right elbow at the sixth intercostal space. The probe head is at the top of the image, dorsal to the left.

Fig 9 Sonographic findings taken 10 cm below the point of the right elbow at the sixth intercostal space. The probe head is at the top of the image, dorsal to the left.

Feedback: The bright linear echo formed by normal visceral pleura at a depth of 2.5 to 3 cm from the probe head is present in the dorsal lung field (Fig 7) but is replaced ventrally by columnar hypoechoic areas extending up to 4-8 cm into the lung parenchyma consistent with localized (lobular) consolidation/cellular infiltration/abscess formation (Figs 8-9).
- Pleural abscesses
- CSPD
- Parasitic bronchitis
- Bullae formation following acute BRSV infection
Diagnosis

What is the likely causal organism?

Feedback: Arcanobacterium pyogenes is the most common bacterium isolated from such cases of CSPD. While the initiating cause of the respiratory disease during early calfhood may have been either Mannheimia haemolyica, Pasteurella multocida or Haemophilus somni, such primary infections are subsequently secondarily infected with A. pyogenes. Stresses associated with dystocia/onset of lactation cause recrudescence of infection and the appearance of clinical signs. Recrudescence of latent infection is also typical of Salmonella dublin infection. Exacerbation of clinical signs of paratuberculosis may also occur after calving.
- Mannheimia haemolyica
- Pasteurella multocida
- Haemophilus somni
- Arcanobacterium pyogenes
Treatment

What is the likely best antibiotic treatment

Feedback:
The most effective treatment is 22,000 IU/kg procaine penicillin administered intramuscularly daily for 4-6 weeks. Procaine penicillin is inexpensive and the treatment course costs no more than £40-£50.

The response rate for CSPD disease is about 50% depending upon severity (extent of pathology determined ultrasonographically). This heifer is shown 5 days after penicillin treatment commenced (Fig 10).

Fig 10 Heifer five days after start of penicillin therapy.

In more severe cases the animal fails to respond to treatment and is euthanased for welfare reasons. A severe necrotising pneumonia and associated pleurisy predominantly involving the right lung was evident at post mortem in the cow shown in Figs 11-13. The infection in some areas was considered to be anaerobic in nature brought about by the local hypoxaemia caused by the underlying chronic pneumonia. It is estimated that anaerobic infections may be present in up to 40 per cent of chronic pneumonia cases; in some equine respiratory diseases metronidazole is commonly used although this drug is now longer licensed for use in food-producing animals in many countries.

Fig 11 Dairy cow with severe necrotising pneumonia.

Fig 12 Severe necrotising pneumonia and pleurisy revealed at necropsy.

Fig 13 Suspected anaerobic infection in the cow featured above (Figs 11-12) with severe necrotising pneumonia and pleurisy.

Control and Prevention

Prevention and control of CSPD must review those factors leading to the initial episodes of respiratory disease during the rearing phase.

Determine the likely viral and/or bacterial causes
Review prevention treatment strategies
Investigate, where relevant, the role of BVD.
Review the calf rearing facilities

Determine the likely viral and/or bacterial causes

Bronchoalveolar (or trans-tracheal) lavage to obtain virus identified by FAT is the most useful test in acute respiratory disease for BRSV. FAT on frozen lung sections requires a dead animal in the acute phase of the disease process. Paired serology from 4 to 6 calves, 2-3 weeks apart, is costly and of little use in tackling the problem at the start of an outbreak. A four-fold increase in titre in 25% of sample population is considered indicative of BRSV involvement. Maternally-derived antibody present in the acute phase samples in calves less than 4 months-old renders interpretation meaningless. IBR virus is best detected by FAT in ocular swabs from febrile animals.

Review treatment and prevention strategies

Vaccination is widely used to control BRSV-induced respiratory disease. IBR vaccination is inexpensive either by single intranasal or intramuscular injection, and is included in the multivalent respiratory vaccines.

There should be prompt veterinary treatment of pneumonia cases. Remember that up to 20 per cent of calves may have a second episode of respiratory disease due to re-infection of the compromised physical defence mechanisms such as the muco-ciliary escalator.

There must be close monitoring of antibiotic treatments especially those administered by farmer.

Avoid using antibiotic/cortisone combinations for routine pneumonia cases.

While many veterinary practitioners elect to inject all cattle in a group when 10 to 33 per cent of animals show clinical signs of respiratory, there is no evidence to support such a practice in the UK. Metaphylactic antibiotic injection is expensive and is not consistent with Good Clinical Practice and the BVA stated policy on responsible antibiotic usage.

Review of the calf rearing facilities.

Reduce stocking density and improve ventilation/reducing humidity of the calf rearing accommodation (Figs 14-15). It has been estimated that 70 per cent of buildings used for rearing cattle have inadequate ventilation. Smoke bombs can be used to investigate air flow through buildings. Do not mix different age groups especially the practice of holding back recovering animals into the next batch of younger calves (Fig 16) .

Fig 14 This photograph shows the poorly ventilated calf house where the floor is always wet by over-use of a water hose (instead of a brush).

Fig 15 The calf house is also used for storing grain and the Yorkshire boarding has been blocked to keep out rain and snow preventing the natural stack effect of the building when used for calf rearing.

Fig 16 This farmer often mixed different age groups. It was standard practice to hold back recovering animals into the next batch of younger calves.

Holstein heifer calved two months with a history of poor milk yield (12 litres per day) occasional coughing and mucopurulent nasal discharge. Respiratory rate 56 breaths per minute with marked abdominal component. Normal rectal temperature. A 5MHz sector scanner reveals normal lung dorsally (bright white hyperechoic line moving in time with respiration) suddenly replaced by large hypoechoic (consolidated) areas at a level on the chest wall around 10 cms above the point of the elbow. This is the typical sonographic appearance of chronic suppurative pulmonary disease.

The heifer featured in the above video after 10 days' treatment with procaine penicillin. The appetite and rumen fill is much improved. The heifer is much brighter (and cleaner). Treatment was continued for a further 30 days - procaine penicillin is time-dependent hence the long course of therapy. Note that procaine penicillin does not give any injection site reaction and such prolonged therapy is well tolerated by the animal which can be fed at the same time as treatment to facilitate handling. Long-acting penicillin preparations do NOT work This heifer made a good recovery but was culled when fat because the condition will relapse after next calving or other significant stress.

Holstein cow showing severe respiratory signs with the neck extended and the head held lowered. There is copious purulent nasal discharge. There is a marked inspiratory effort and increased respiratory rate. The rectal temperature is normal. A 5MHz sector scanner reveals normal lung dorsally (bright white hyperechoic line) suddenly replaced by large hypoechoic (consolidated) areas at a level on the chest wall around 20 cms above the point of the elbow. The cow was euthanased because the pathology was too extensive and too long-standing to treat. Necropsy reveals the extensive consolidation of the ventral portions of the apical and cardiac lung lobes. There are widespread fibrous adhesions between the lungs and the pericardium. There are large amounts of pus within the bronchioles and on the cut surface after squeezing the affected lung areas. There is severe emphysema of the dorsal regions of the diaphragmatic lung lobes caused by hyperventilation compensating for greatly reduced functional lung capacity.
- Single injection of taluthromycin
- Single injection of a fluoroquinolone antibiotic
- Procaine penicillin administered intramuscularly daily for 4-6 weeks
- Amoxycillin plus clavulanic acid administered intramuscularly daily