Interesting cases for July and August

Cattle
Abortions/mastitis

• Fixed tissues were received from a six-month gestation aborted male shorthorn foetus. Autolysis hampered much of the histopathological examination but within the lung and liver small numbers of neutrophils were observed which could be suggestive of bacterial infection. Within the foetal liver there was evidence of biliary stasis. In the foetus the placenta assists with bile excretion and so biliary stasis can be seen with placental insufficiency. Possible causes of placental insufficiency can include placentitis (e.g. due to an infectious cause), poor uterine perfusion or systemic illness in the dam, multiple foetuses, poor maternal nutrition, torsion or compression of the umbilical cord, toxins such as mycotoxins, and heat stress. Light, pure growths of Aeromonas spp. were isolated in culture of the foetal stomach contents and this finding along with the presence of inflammatory cells and biliary stasis on histopathology was considered of potential significance as a cause of this sporadic abortion.
• Profuse growths of Lelliottia spp. were cultured from the stomach contents of a seventh month gestation dairy calf foetus. Lelliottia spp. is a member of the Enterobacteriacae and could be a potential cause of abortion due to opportunistic invasion of the gravid uterus.
• Pasteurella multocida was isolated in cultures of foetal stomach content in one case of abortion in a beef cow. multocida is a cause of sporadic abortions in cattle typically occurring by haematogenous spread e.g from the respiratory tract or septicaemia.
• There were at least eight cases over July and August in which Salmonella was isolated from foetal stomach contents, in which the isolates were identified as Salmonella Dublin.
• A profuse and pure growth of Helcococcus ovis was isolated from a mastitic milk sample from a dairy cow. This isolate is rarely reported as a cause of bovine mastitis but has also been found in other sites in farm animals e.g abscesses, metritis, endometritis and bronchopneumonia.
• Klebsiella pneumoniae was isolated from milk samples from two cows on a dairy unit which was experiencing an increase in mastitis cases after drying-off. Outbreaks of Klebsiella mastitis have been associated with sawdust bedding. Klebsiella can produce a severe toxic mastitis.
• Cytology of material expressed from the teat of a two-month-old male calf identified marked neutrophilic inflammation, consistent with bacterial mastitis. No bacterial culture of the material was carried out. ‘Summer mastitis’ typically involving pyogenes is one of the most common forms of mastitis in male animals outdoors. Cross-suckling can also occur in male calves housed in groups and this can predispose them to mastitis by introducing bacteria directly into the teat canal.
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Respiratory disease

• IBR virus was detected by PCR in a pool of three ocular swabs from seven-month-old mixed breed calves which were showing signs of pyrexia, coughing oculonasal discharge, chemosis and On another farm IBR was also diagnosed by PCR on a nasopharyngeal swab in an adult cow with respiratory signs and pyrexia. IBR was detected by PCR in at least eleven other cases in July and August.
• Fixed samples of lung tissue from a five-month-old calf were submitted to investigate the cause of respiratory signs and increased mortality. Unfortunately, marked to extreme autolysis and postmortem bacterial contamination hampered histopathological examination, though in some better-preserved areas there was evidence of moderate fibrinosuppurative bronchopneumonia and nematode larvae were Parasitic pneumonia due to Dictyocaulus viviparus with secondary bacterial infection was considered the most likely cause of the lung lesions in this case. There were multiple other cases of lungworm diagnosed through July and August. In one case half of the cows in a small dairy herd of twenty animals were affected with coughing and showed some degree of milk drop with two animals appearing clinically sick.
• Mannheimia haemolytica was detected by PCR of a lung swab from an Aberdeen Angus cross calf with evidence of severe pleuropneumonia on postmortem examination.
• A postmortem was carried out on farm of a ten-week-old calf which had appeared to have died suddenly. The animal had been out at pasture with its dam since the age of two Extensive consolidation of lung tissue with abscesses throughout was observed. Trueperella pyogenes, a common secondary pathogen found in abscessated lungs was cultured from a lung swab and PCR testing detected Mycoplasma bovis, Histophilus somni and Pasteurella multocida, all of which could be considered of significance, usually acting as secondary pathogens.
• A five-month-old calf presented with signs of coughing and respiratory distress. There was little response to treatment with long acting oxytetracycline and flunixin and the animal died within three days of the onset of clinical signs. Samples of fresh and fixed lung tissue were received. Pasteurella multocida was detected by PCR testing of the fresh tissue. Histopathology revealed that there were severe, chronic and ongoing changes in the lung consistent with a case of enzootic calf pneumonia/ bovine respiratory disease. Bronchiolitis fibrosa obliterans pointed to a severe necrotising bronchiolitis suggestive of a previous pneumotropic viral infection such as RSV, PI or IBR. However, PCR testing was unrewarding which may have been due to the chronic nature of the lesions. Evidence of alveolar septal necrosis with hyaline membrane formation raised the possibility of this being a case of BIP (bronchopneumonia with interstitial pneumonia). BIP is considered a distinct condition where chronic cranioventral bronchopneumonia and inflammation increases sensitivity to 3-methylindole (or another pneumotoxin), leading to acute caudal interstitial lung disease. However, to make this diagnosis correlation with gross pathology would be required, which was not possible in this case.
• Diffuse Alveolar Damage (DAD), also known as interstitial pneumonia was the likely cause of peracute illness and death in a pre-weaned Limousin cross DAD represents a non-specific histopathological pattern of acute lung injury resulting from primary insult to the alveolar epithelium and/or vascular endothelium. As such, it is associated with a wide range of aetiologies in cattle, which can broadly be divided into toxic, infectious, and systemic causes. In cattle, one of the most recognised causes is exposure to pneumotoxic compounds, particularly 3 methylindole (fog fever) however, this is less common in pre-weaned animals. Other toxic insults include plant-associated pneumotoxins (e.g. perilla mint) and dietary or environmental toxins. Infectious agents may also result in DAD, either through direct injury to alveolar structures or indirectly via inflammation (cytokine storms); these include respiratory viruses (notably bovine respiratory syncytial virus), parasitic infections such as lungworm, and septicaemic processes. Given this broad range of potential causes, interpretation of DAD requires integration with clinical history, management factors, and ancillary testing, as the lesion itself is not pathognomonic for a specific aetiology. There was a similar case on another farm where a heifer presented with pyrexia, cyanosis and acute respiratory distress. Six other animals in the group were also affected. PCR testing of lung tissue did not detect any infectious agent but there was evidence of DAD/ interstitial pneumonia on histopathology. In this case the animals had been recently moved during hot weather, and it was considered that heat stress may have predisposed the animals to respiratory disease.

Gastrointestinal disease

• There were numerous cases of coccidiosis and suspected coccidiosis in calves in July and August. Eimeria zuernii, one of the two main pathogenic species of coccidia in cattle, was found to make up 88% of the oocysts present in a pooled faecal sample with a coccidial oocyst count of 20,500opg from a group of three to four-month-old scouring calves, confirming a diagnosis of coccidiosis in that case. Coccidiosis was suspected to be the cause of severe haemorrhagic scour in a group of Aberdeen Angus calves. The coccidial oocyst count was >50,000opg. Eimeria species identification was not carried out, though very high counts such as this are usually significant in cattle. Salmonella cultures were negative. In another case fixed tissues including sections of small intestine were received from a post weaned Holstein-Friesian dairy calf. Examination of the gut tissue revealed a chronic eosinophilic and granulomatous enteritis with intralesional coccidial structures suggestive of mucosal damage due to coccidiosis, though no further details regarding the clinical signs were given.
• Coronavirus was detected in at least four cases of neonatal calf diarrhoea and in two of these Cryptosporidium antigen was also detected.
• E.coli F5 (K99) antigen was detected in the intestinal contents of a calf which had appeared healthy at birth but became ill and died at less than twenty-four hours of age. Yellow fibrin strands were observed in the peritoneal cavity at postmortem examination. Antigen testing for rotavirus was also positive in this case, though clinical signs attributed to rotavirus do not usually occur in calves before around five days of age. Therefore, the enterotoxigenic E.coli was the most significant finding in this case. There were at least five other cases of E.coli F5 (K99) associated enteritis in neonatal calves in July and August.
• There were multiple cases of gastrointestinal disease in adults and youngstock related to Salmonella In one submission Salmonella Typhimurium was isolated in a sample from one of two pyrexic dairy cows. There was a history of sick calves and recent abortions on farm.
• A high strongyle egg count of 700epg was recorded in a faecal sample taken from one of three collapsed calves in a group of 75 three to four-month-old Holstein-Friesian heifers on Watery, dark scour was observed in the affected animals and this along with the high faecal worm egg count was indicative of parasitic gastroenteritis. No coccidial oocysts were observed in the sample and Salmonella cultures were negative making these differential diagnoses less likely, though it should be considered that disease due to coccidiosis can occur in the prepatent stages and that shedding of Salmonella can be intermittent.
• Pepsinogen levels were significantly raised in two Wagyu fattening animals which were not thriving and were found to have each lost 30kg at weighing. One of the two was also scouring. The anthelmintic treatment history was not given but no eggs were observed on individual faecal egg Pepsinogen levels were raised at 4.83iu/l and 3.97iu/l (RI = 0.00-1.50). These levels are considered indicative of significant abomasal damage due to parasitism which was likely to be associated with the reported clinical signs.
• Mycobacterium avium paratuberculosis (MAP) was detected in the faeces of an adult cow at a low Ct value of 24, indicative of heavy shedding of the bacterium and consistent with a diagnosis of Johne’s disease. In addition to the positive Johnes’ PCR result, Bovine coronavirus (BCov) was detected using the bovine coronavirus antigen test on faeces and this result would be considered diagnostic of winter dysentery. The coronavirus lateral immunochromatography antigen test is not usually recommended for detection of winter dysentery as it is thought to be of insufficient sensitivity to detect the disease in adult cattle. PCR testing or paired serology are the preferred diagnostic tests for this condition. There were numerous other cases of Johne’s disease diagnosed including a twenty-month -old British Blue cross animal which had been losing condition and scouring over the previous two months and an Aberdeen Angus bull which had signs of severe wasting and scour for one month.

Skin and eye disease

• Ringworm (Dermatophytosis) was diagnosed by PCR on a hair pluck from one of five dairy heifers with skin The infection had spread through the herd and most had recovered but these animals remained affected.
• Corynebacterium pseudotuberculosis, the causative agent of caseous lymphadenitis was isolated from a swab from an unknown site on an adult No other history was available but CLA is occasionally known to occur in cattle.
• There were at least nine submissions in which Moraxella bovoculi was isolated in cultures from cattle showing signs of infectious bovine keratoconjunctivitis (IBK), also known as New Forest eye or pinkeye. In several of these cases the bacterium was isolated from more than one animal in the same Staphylococcus aureus was isolated in addition to M.bovoculi on one sample and this was a possible significant pathogen acting as an opportunist and contributing to the eye lesions in that animal. M. bovoculi is commonly isolated in cases of IBK in cattle but can also be found in healthy animals. In another case of suspected IBK three eye swabs from affected animals were cultured and Pantoea spp. were isolated from all three. Pantoea spp. are commonly found in the environment but could be acting as opportunists in this case e.g following irritation from dust or flies. In a third case of IBK, Rothia nasimurium was isolated from an eye swab. It was noted that in one study by Gafen et al (2023) Rothia nasimurium was significantly more abundant in IBK eyes than in normal eyes so it could be an opportunistic pathogen in this case.
• Penile fibropapilloma was diagnosed by histopathology of a tissue biopsy from a Beef Shorthorn bull. Fibropapillomas are hyperplastic lesions caused by papillomavirus infection. Penile fibropapillomas in bulls are most often diagnosed at one to two years of age. They can spontaneously resolve, but this occurs after a variable time period, and recurrence can often be a problem.

Systemic and miscellaneous disease

• Notable cases of BVD viraemia included a two-day-old bull calf which was dull, had reduced mentation and failed to rise after The calf tested positive for BVD by PCR on a blood sample. In another case a poorly thriven twenty-month-old Aberdeen Angus cross bullock tested positive in the BVD antigen ELISA raising a strong suspicion that it was a BVD persistently infected animal. In a third submission a bought-in yearling heifer showed signs of poor appetite and was failing to thrive. It had a high positive result for BVD antigen in the ELISA and it was suspected that this animal was also likely to be a BVD PI.
• Blood parasites associated with erythrocytes and with an appearance consistent with Babesia sp. were seen in one out of three blood smears submitted from adult dairy cattle in south west Scotland with signs of milk drop, haematuria and anaemia. Babesiosis was also diagnosed on examination of blood smears from two dairy heifers in North Somerset showing signs of red urine, but which were otherwise well in themselves. In another submission from a farm in Cornwall an adult dairy cow with milk drop, blood in the urine and pyrexia tested positive for Babesia sp. by PCR testing of an EDTA blood sample. Babesia sp. were detected by PCR testing of a blood sample from a six-year-old Dexter cow in Gloucestershire which became jaundiced, anaemic and pyrexic around one month after calving. In a fifth case in mid-Wales a yearling heifer with respiratory signs and jaundice had both evidence of Anaplasma phagocytophilum inclusions in the neutrophils on the blood smear, confirming Tick borne fever and parasites consistent with Babesia sp. within the erythrocytes indicating concurrent
• Renal carcinoma was diagnosed in a 16-year-old, male, castrated miniature Zebu which was found dead At postmortem examination the right kidney appeared misshapen and around 75% of the tissue was very firm and partially adhered to the peritoneum. Purulent material was observed on incision into the renal pelvis. Histopathology of a section of the kidney revealed that around 60% of the section consisted of an unencapsulated, poorly differentiated collection of neoplastic cells. Similar cells were observed in a section of nearby lymph node. Taking into account the gross description of the kidney and the histopathological appearance, it was considered that this tumour was most likely a malignant renal carcinoma with spread into the local lymph node.

Figure 1: Clusters of neoplastic epithelial cells in the kidney of a zebu with suspected renal carcinoma. Arrow indicates an atypical cell with karyomegaly (large nucleus).

• Fixed tissue samples consisting of sections of oesophagus and lung were submitted from one animal from a group of Jersey cross calves with signs of malaise and poor performance associated with some mortality. Histopathological examination revealed marked lesions with evidence of severe ulcerative oesophagitis and bacterial bronchopneumonia. There was evidence of bacterial colonisation of the lesions in the Such lesions are often associated with mucosal trauma, including injury secondary to coarse or abrasive forage, foreign material, or iatrogenic damage (e.g. administration of oral medications or dosing equipment), although other causes of mucosal injury could also be considered (e.g uraemic syndrome). It was commented that summer scour syndrome (SSS) of dairy calves cases can sometimes have oesophagitis. SSS usually occurs within a few weeks of turnout and is believed to be due to rumen dysbiosis due to too rapid a change in ration. It can be more common on lush grass and it is also possible that the high oil levels in the grass contribute.
• Pre and postmortem samples were received from a four-month-old Holstein dairy heifer calf that showed signs of acute haemorrhage with multiple small wounds on the skin and torso which failed to clot (Figure 2). A prolonged clotting time was recorded during the clinical Petechial haemorrhages were visible on the hairless skin, vulval membranes, in the conjunctiva/sclera and on the internal organs at postmortem. Unclotted blood was present in the abdominal cavity. Haematology revealed severe anaemia with a PCV of 9% (RI=24-40%) and the platelet count was 16 x 10^⁹/L (RI= 200-800 x10^⁹) indicating marked thrombocytopaenia, which could explain the spontaneous haemorrhages and petechiae of mucous membranes. On histopathology there was evidence of bacterial bronchopneumonia and interstitial nephritis, most likely indicative of a past bacteraemia (e.g colisepticaemia). The findings considered most significant were seen in bone marrow tissue. There was a marked hyperplasia in the bone marrow suggesting the haemorrhage had been occurring for longer than previously assumed (at least 24 hours) (Figure 3). The cause of the bleeding / lack of clotting was not possible to determine from histopathology. Initial differentials which were considered included DIC, anticoagulant rodenticide toxicity, inherited deficiency of coagulation factors and ingestion of mouldy sweet clover. A similar case of anaemia (PCV 15%) with thrombocytopaenia (Platelets 10×10^9/l ) with haemorrhage from multiple sites was seen later in August and in that case, the heifer, which was the only animal affected died soon a short time after examination (Figure 1). The unusual nature of these cases triggered further discussion and a possible increase in submissions involving thrombocytopaenia in farm animalsover previous weeks had been observed. There is a possible link of thrombocytopaenia with BTV infection, and this is being further investigated in collaboration with APHA. Thrombocytopaenia, along with other haematological abnormalities, has been documented in previous Bluetongue cases. Van den Brink KMJA, Santman-Berends IMGA, Harkema L, Scherpenzeel CGM, Dijkstra E, Bisschop PIH et al. Bluetongue virus serotype 3 in ruminants in the Netherlands: Clinical signs,seroprevalence and pathological findings. Vet Rec. 2024;e4533. Three cases of bleeding calves with haemorrhaging from the skin linked to BTV8 and a single case with BTV3 in calves aged 1-2 weeks old have been reported in France.

Figure 2 : Down heifer with signs of haemorrhage from multiple sites with failure to clot. (Photo Sophie Goodings, Axe Valley Large Animal Vets)

Figure 3: Bone marrow from a bleeding calf showing near 100% cellularity, with hyperplasia of the erythroid cell line.

• Clostridium botulinum C/D toxin was detected by ELISA testing of small intestinal contents taken at postmortem examination of a yearling heifer which died after a short duration of The finding was suggestive of a diagnosis of death due to botulism, though in autolytic carcases there can be a risk of postmortem formation of botulinum toxin. It was advised to consider any known risk factors and clinical signs and to contact APHA for advice relating to potential food safety concerns.
• A two-day-old heifer calf which was a twin to a bull calf was tested in the freemartin genetic test on an EDTA blood sample and male DNA was detected, confirming the animal was a freemartin. This condition affects about 90% of female calves born with a male twin, due to the fusing of the two placentas and sharing of blood supply and hormones in utero.