Interesting cases in April

Cattle
Abortions and mastitis

• A Holstein calf foetus aborted in the fourth to fifth month of gestation tested positive for BVD virus in the antigen ELISA on foetal (peritoneal) fluid.
• BVD virus was detected by PCR in foetal tissues from a bovine abortion.
• Listeria monocytogenes was isolated from the foetal stomach contents of a dairy cow, which aborted around the time of drying-off.
• Neospora caninum was detected by PCR in foetal tissues from two aborted calves.
• Trueperella pyogenes was isolated in cultures from a foetus, which was aborted in the last month of gestation.
• Exposure to Schmallenberg virus was identified by serology of foetal fluids from a bovine abortion, providing evidence of in utero infection with SBV.
• Mastitis pathogens cultured from milk this month included Escherichia coli, Streptococcus uberis, Streptococcus dysgalactiae and Serratia species.
• Staphylococcus aureus was isolated from several milk samples. In one case of S. aureus mastitis, the cow, which had calved five days previously, was down, hypothermic, dehydrated and very sick.
• A more unusual isolate from milk this month was Pseudomonas libanensis. As it was isolated in heavy and pure growth, it was considered that this could be a cause of environmental mastitis although it is not commonly recognised as a cause of mastitis in comparison to Pseudomonas aeruginosa.

Respiratory disease

• IBR was detected by PCR in at least four submissions this month. On one farm, the affected animals had arrived on the holding four to six weeks previously. Typical clinical signs of pyrexia, bilateral ocular and nasal discharge and upper respiratory tract noise and distress were seen.
• RSV was detected in at least 19 submissions and PI3 virus in at least three, either as the sole pathogen detected or in combination with other viral or bacterial pathogens.
• One RSV case involved a batch of dairy heifers, which were part way through calving. The heifers showed signs of pyrexia, hunched up appearance, milk drop and sunken eyes. Lung consolidation was observed on ultrasound.
• Another case of RSV, where bovine coronavirus was also detected by PCR of nasopharyngeal swabs, was in nine-month-old unvaccinated calves, which were purchased through a market one week prior to developing signs of nasal discharge and pyrexia.
• Bovine coronavirus was also detected by PCR as the only respiratory pathogen in seven respiratory cases this month and in a further 11 cases it was detected along with IBR, RSV and PI3 and/ or the bacterial pathogens, Mycoplasma bovis, Mannheimia haemolytica, Pasteurella multocida or Histophilus somni.
• Mycoplasma bovis was detected by PCR in several cases of respiratory disease, often along with viral pathogens or bacterial pathogens particularly Mannheimia haemolytica and/or Pasteurella multocida.
• Histophilus somni and Pasteurella multocida were detected by PCR of lung tissue from a recently turned out December born beef suckler calf. The calf had appeared well at turnout four days previously but was found dead in the field. There was marked pathology of the cranioventral lung lobes at post mortem examination suggestive of a pneumonia with bacterial involvement.
• Serology testing revealed evidence of exposure to lungworm (Dictyocaulus viviparus) in cattle this month. Following challenge naïve animals sero-convert after approximately 4-6 weeks, antibody levels generally peak after 12 weeks, but remain elevated for 4-5 months post infection. Therefore, positive results usually indicate exposure to the parasite in the current grazing season, but occasionally animals will remain positive throughout the housing period.
• Aspiration pneumonia was identified by histopathology of lung tissue samples from a three-day-old calf. The farmer had reported issues with pneumonia in young calves but was now seeing problems in neonatal calves. Two young calves had died following signs of respiratory distress. Microscopic examination revealed severe bronchopneumonia associated with aspirated material and bacterial infection, consistent with the appearance of
  an aspiration pneumonia. There was evidence of milk-like fluid within alveolar spaces as well as abundant bacterial contamination and other debris. In light of these findings, it was suggested that management of calves in the perinatal and early post-natal period should be reviewed.
• Lung tissue from a cow, which had died suddenly at grass, was submitted for histopathology. It was noted that the parenchyma was unremarkable but in the large arterial structures accumulations of necrotic amphophilic (definition: stains readily with both acidic and basic dyes) material admixed with poorly preserved neutrophils were present within the vascular lumen. This appearance was considered consistent with a case of pulmonary thromboembolism.

Gastrointestinal disease

• A total of 504 submissions for Johne’s disease serology and faecal PCR testing from cattle were received this month, with 163 submissions, including a total of 253 individual samples, testing positive.
• Raised pepsinogen levels indicative of significant abomasal damage due to parasitism were seen on a number of submissions this month. In one case a yearling Hereford heifer was found down and unable to rise with a poor body condition score of 1.5 and watery scour. There was no history of recent worming treatments and it was noted that a larger proportion of the cattle were in thin condition with evidence of loose faeces in other youngstock. Pepsinogen in the single animal tested was 3.6 iu/l (Ref 0.0-1.5iu/l) suggesting that abomasal parasitism was a significant factor in the clinical presentation.
• There was a heavy growth of Clostridium perfringens in anaerobic cultures of the abomasal wall from a three-week-old suckler calf, which had died suddenly and had a ruptured abomasum on post mortem examination. The isolate in this case was considered likely to be significant. C. perfringens is a recognised cause of abomasitis and abomasal ulceration in calves.
• Bovine coronavirus, the cause of winter dysentery, was detected by PCR in faeces in one submission. All ages of dairy stock were reported to be affected.
• Salmonella Dublin was isolated in cultures on six submissions. On one farm, there had been a spike in scour, pyrexia and inappetance in freshly calved and dry dairy cows with some abortions and at least two cows had died or had to be euthanased. In another submission, a calf had died at seven days old and at PME, there was evidence of acute peritonitis and abomasitis. Both Salmonella Dublin and Listeria monocytogenes were isolated in that case. The listeria isolate was considered to be of potential significance, though septicaemia due to L. monocytogenes is more commonly recognised in sheep.
• Salmonella Typhimurium was grown in cultures of faeces in four submissions. Of two cases where history was provided both described cows with scour and pyrexia shortly after calving and the animals appeared very sick and depressed. A third case was in calves in which both submitted samples were positive for Cryptosporidium and monophasic S. Typhimurium was isolated from one of the two samples.
• Salmonella Mbandaka was isolated from faeces in two cases. 
• Salmonella sp. were detected by PCR in one case. Again, there was a history of diarrhoea in freshly calved cows. In this case, the isolate failed to grow in selective cultures, so serotyping could not be performed.
• Post mortem tissues were received from adult Holstein dairy cows of which five out of 100 had died in the last 10 days. PME was suggestive of possible salmonellosis or haemorrhagic bowel syndrome (a.k.a jejunal haemorrhage syndrome, bloody gut). Histopathology revealed a severe necrotising enteritis with abundant rod-shaped bacteria suggestive of a clostridial enteritis. Gram staining of the intralesional bacteria was further supportive of this diagnosis. However, in this case other bacterial causes of enteritis and jejunal haemorrhage syndrome could not be completely excluded from the differentials. Necrotising clostridial enteritis is rare in adult cattle and usually secondary to an underlying cause. Outbreaks of clostridial enteritis can be seen occasionally which are thought to be associated with a change in diet / poor quality diet.

Skin and eye disease

• Trueperella pyogenes was isolated from a sample of malodorous fluid aspirated from a facial swelling on an Aberdeen Angus cross cow. The animal was reported to be bright with a normal appetite but was rapidly losing weight and the swelling appeared to be spreading to the brisket area and abdomen with antimicrobial treatment proving ineffective.
• Proteus mirabilis was isolated in cultures of ear swabs from three calves on the same farm but in different groups that were showing signs of purulent ear infections. The finding was considered significant in this case of otitis and it was likely that the P. mirabilis was acting as an opportunistic pathogen.
• Cutaneous actinobacillosis (caused by Actinobacillus lignierissi) was diagnosed by histopathology of skin biopsies of masses on the leg and jaw area of a bovine. Histopathologically a granulomatous to pyogranulomatous dermatitis associated with bacterial infection was observed. Gram staining confirmed the presence of small gram-negative rods at the centre of some club colonies, consistent with the appearance of cutaneous actinobacillosis.

Small clusters of bacteria (*) with bright eosinophilic club colonies (Splendore–Hoeppli material; arrows), surrounded by neutrophils and macrophages

Systemic and miscellaneous disease

• A total of 436 submissions were received for BVD antigen testing in cattle in February, with 36 submissions, including a total of 70 individual samples, testing positive. On one farm, a purchased in-calf cow produced a calf, which was small and blind. The calf tested positive for BVD in the antigen ELISA test indicating it was likely to be a PI (follow up testing to confirm this was recommended). The dam was negative for BVD antigen in the ELISA test. In another submission, a two-year-old heifer, which was poorly grown for its age, gave birth to a poor looking calf, which later died. The heifer tested positive for BVD antigen in the ELISA indicating it was likely to be a BVD PI animal.
• There were seven positive MCF PCR results this month, with detection of the Ov-HV2 virus primarily in whole blood samples, blood being the preferred sample, although in one case on a plain nasal swab. This was consistent with a diagnosis of Malignant Catarrhal Fever. Where a history was given, the clinical signs were typical with severe pyrexia, nasal and ocular discharge and/or oedematous eye lesions.
• Babesiosis was diagnosed by PCR in two cases, both in Devon, which presented with typical signs of ‘redwater’.
• Three mid-lactation dairy cows presented with pyrexia (>40.5oC) and severe milk drop. They had been turned out to pasture three weeks previously. Several nine-month-old calves on the same holding presented with
  significant fevers and ticks were present on them. All three of the cows tested positive on PCR of blood samples for Anaplasma phagocytophilum, the cause of tick-borne fever (TBF).
• Blood samples were submitted from a cow, which was suspected to have secondary photosensitisation. The cow presented with symmetrical swelling of the head with crusting and sloughing of the skin on nose, around eyes, perineum and udder. Severe hepatocellular injury and hepatic cholestasis were confirmed with a GLDH level of 1316U/L (Ref. range 0-25 U/L) and GGT of 235 U/L (Ref. range 0-50).
• Hypogammaglobulinaemia was reported in a neonatal calf with a history of scour and doubtful colostrum intake and in a four-day -old calf which had no obvious signs of joint/navel infection or septicaemia but was reported to be dull and ‘never got going’ despite having been seen suckling shortly after birth.
• A one-month-old Hereford heifer calf, which was found down with neurological signs and an expected poor prognosis, was euthanased for post mortem examination. The kidneys were abnormal on gross examination with evidence of renal inflammation and an enlarged ureter. Sections of the affected lower urinary tract/genital tract and kidney tissue were submitted for histopathology. Microscopically there was evidence of omphalitis leading to a fibrinopurulent arteritis of the umbilical artery. Examination of the kidney revealed a severe tubulointerstitial nephritis likely to be compromising renal function. Tubulointerstitial nephritis may be secondary to ascending infection or haematogenous insults. Given the evidence of navel infection and the relative sparing of medullary and pelvic areas a haematogenous insult was considered most likely in this case.