Interesting cases in February

Cattle
Abortions/mastitis

• Necrotising encephalitis and hepatic necrosis were observed on histopathology of brain and liver tissue of an aborted calf foetus. The 500-cow dairy farm from which the foetus was submitted had recorded five abortions in late 2025. At that time samples from two aborted calves did not identify any causal pathogen. A further four abortions occurred over ten days in February. Changes on histopathology were suggestive of ongoing hypoxia of the foetus, most likely caused by placental insufficiency. Placental insufficiency is the result of inadequate perfusion of the placenta, leading to suboptimal oxygen and nutrient delivery to the foetus. Possible causes could include nutritional stress or deficiencies, infectious agents (no inflammation seen and no evidence of bacterial or fungal organisms with special stains), toxicoses, or other insults.
• Salmonella Anatum was isolated from one case of bovine abortion this month. This serotype is usually associated with contaminated feedstuffs. Wild birds and badgers have both been implicated in the carriage of this serotype.
• Actinobacillus seminis was isolated from foetal stomach contents in one case of bovine abortion. Actinobacillus seminis is reported as a cause of epididymitis in sheep and has also been associated with bovine abortion and was considered a relevant finding in this case.

Respiratory disease

• An adult dairy cow presented in late gestation with a clear nasal discharge, pyrexia of 410C and was anorectic. Approximately six cows and one bull were similarly affected in the herd of around 80 animals. IBR infection was suspected and confirmed by PCR testing of a nasal swab from the sick cow.
• Postmortem tissues were submitted from two one-month old Holstein- Friesian bull calves which were seen with signs of respiratory distress in the evening but died overnight despite treatment for pneumonia. The submitting vet noted that there was a suspicion that both calves had suffered from failure of colostral absorption. Mannheimia haemolytica and Pasteurellla multocida were detected by PCR in lung tissue of both calves. Histopathology identified a severe fulminating bacterial pneumonia consistent with the PCR results.
• More than fifteen cows in a 500-cow dairy herd were affected with respiratory symptoms which had started one week before. Samples were submitted from the first cow to die in the outbreak. Mannheimia haemolytica was detected in lung tissue by PCR testing and the finding was of likely significance in the outbreak.
• Respiratory signs were seen in a group of approximately twenty suckler calves running in a cow and calf group. A few of the calves had already been treated for presumed pneumonia by the owner. Rectal temperatures were taken from all the calves on the day of examination and the majority had pyrexia over 39.20C. Untreated calves with temperatures >400C were selected for sampling and a pool of four swabs tested in the respiratory pathogen PCR package was positive for RSV, indicating that this pathogen was likely responsible for the respiratory disease outbreak.
• Postmortem tissues were received from a post-weaned suckler calf from a group in which respiratory signs had been seen. This was the second calf to die within a 48-hour period. RSV along with Pasteurella multocida and Mannheimia haemolytica were detected by PCR of a plain lung swab. Marked, extensive, subacute, necrotising and suppurative bronchointerstitial pneumonia with interstitial emphysema was seen on histopathology. These changes supported a diagnosis of RSV infection and a secondary bacterial component, consistent with the PCR results.
• RSV was detected by PCR testing of lung tissue from a seven-month-old limousin cross suckler calf. Consolidation of the lung had been observed at postmortem examination. Histopathologically, airways contained small numbers of neutrophils with admixed cell debris. Airway epithelium had been lost and replaced by fibrin. Alveoli were variably collapsed, diffusely congested, and contained rich proteinaceous fibrin material with few red blood cells and scattered macrophages and neutrophils. Alveolar septa were extensively necrotic, replaced or lined by thick layers of fibrin (hyaline membranes). Multifocal Type II pneumocyte hyperplasia was present. Small numbers of mixed inflammatory cells surrounded blood vessels. Interlobular septa were markedly expanded by dilated lymphatics, clear space and eosinophilic proteinaceous fluid. Overall, these changes were considered severe and typical of RSV infection as per the PCR result.
• Approximately ten of a group of forty British Blue cross heifer calves were affected by severe pneumonia which showed little improvement with tulathromycin treatment. Lung tissue from a calf which died was tested by PCR for respiratory pathogens and was positive for Mycoplasmopsis (formerly Mycoplasma) bovis, Mannheimia haemolytica and Pasteurella multocida. Lung tissue was evaluated by histopathology. Changes to the lung were severe and strongly suggestive of virulent Mycoplasmopsis bovis infection with extensive eosinophilic coagula occluding airways and associated plasmalymphocytic peri-airway infiltrate (Figure 1). Considering the PCR results, it was suggested that this case could be a combined Mannheimia haemolytica and Mycoplasmopsis bovis infection. It was noted that Mannheimia haemolytica infection can worsen the pneumonia caused by M.bovis.

Figure 1: Lung tissue is near completely effaced by bright pink eosinophilic coagula (caseonecrotic material) in a calf with virulent Mycoplasmopsis bovis pneumonia.

Gastrointestinal disease

• Post-mortem tissues were received from a two-week-old, Holstein steer calf. It was one of 120 calves which had arrived one week previously at the calf rearing unit. Calves were divided into four groups with automatic feeders in straw pens. There was access to eight litres of milk per day along with calf grower pellets. There has been a recent rise in the incidence of bloat, with at least ten calves affected and this animal being the fourth to die. At postmortem examination the abomasal mucosa appeared inflamed but no obvious haemorrhage or ulceration was seen. Histopathology identified a moderate, extensive, suppurative abomasitis with submucosal emphysema and intralesional bacterial with appearance typical of Sarcina sp. Sarcina bacteria are often found associated with abomasal bloat and abomasitis in young calves, and the aetiology is still not fully understood. Several predisposing factors are thought to be involved including compromised immunity from failure of passive transfer, bacterial infection of the abomasal wall, and vitamin and mineral deficiencies. The role of bacteria, such as Clostridium perfringens, Clostridium fallax, Clostridium sordellii and Sarcinia spp., in these cases is unclear, but mixed infections have been associated with disease. Entry and proliferation of the bacteria are likely associated with damage to the abomasal mucosa. In artificial milk fed calves this is most often caused by poor milk hygiene, poor quality milk, large volumes of milk fed or milk fed at the wrong temperature.
• Postmortem tissues were received from a 7-10 day old calf which had died suddenly. An abomasal ulcer was found on post mortem examination, and fungal hyphae were found within the associated inflammation on histopathology (Figure 2). Abomasal ulceration in young dairy calves are thought to develop secondary to stress, poor milk feeding practices, or because of coarse feed or grain overload.

Figure 2 : Fungal hyphae found in the wall of the abomasum of a calf with abomasal ulceration (PAS stain)

• Enterotoxigenic Escherichia coli (ETEC) infection was diagnosed by detection of E.coli F5 (K99) antigen in faecal samples from two diarrhoeic calves from the same farm. Several calves had been affected by scour with deaths occurring at 24-48hours of life. E.coli was cultured from the samples and in both cases the isolates showed evidence of invitro resistance to multiple antibiotics.
• An untypable Salmonella species with the antigenic formula 6,7,:z:10:- was isolated from faeces of an adult dairy cow showing signs of acute milk drop and green water scour. Twenty-five of 350 cows were reported to be showing similar signs. Occasionally Salmonella isolates can be difficult to serotype and this may occur if the isolate is unusual, damaged or doesn’t behave in the expected manner under test conditions. Further testing was advised if the problem was ongoing or recurred.

Skin and eye disease

• A pedunculated mass which had appeared over an estimated two weeks on the prepuce of a two-year old Aberdeen Angus bull, was excised and sent for histopathological examination. The mass was identified as a fibropapilloma. (Figure 3) 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 and recurrence can be a problem.

Figure 3: A cross-section of a penile fibropapilloma from a bull showing a proliferation of loosely packed mesenchymal cells, covered by a hyperplastic epithelium.

• Soft tissue sarcoma of the penis was identified on examination of tissues received from a twelve-month-old crossbreed finishing bullock. The submitting vet noted that there appeared to be multiple masses present which were dark red in colour and inflamed. Histopathology confirmed the mass as a spindle cell tumour and nuclear atypia, karyomegaly, necrosis, and frequent bizarre mitoses suggested malignancy. The most likely diagnosis was fibrosarcoma, but other soft tissue tumours were also possible (e.g. peripheral nerve sheath tumour, haemangiopericytoma, myxosarcoma, leiomyoma/-sarcoma, undifferentiated sarcomas). Cases of penile fibrosarcoma are rare but have been previously reported in cattle. Treatment involves prompt, complete surgical removal, but these tumours have a high rate of recurrence due to their aggressive, infiltrative nature.

Systemic and miscellaneous disease

• One of two Aberdeen angus cross calves which were bought in at two weeks of age and had been on farm a further fortnight tested positive on serum in the BVD antigen ELISA indicating BVD viraemia. The result was a low positive with an optical density of 0.9 OD. (Positive: >0.3OD). In this test positive results close to the positive/negative cut off are more likely to be consistent with transient infections. However, persistent infection cannot be ruled out as high levels of maternally derived antibody could potential mask viraemia to some degree. A second BVD antigen test must be carried out after at least three weeks and if antigen positive at that time BVD PI status of the animal is confirmed. On this farm it was observed that two or three from each group of bought in calves would show signs of illness and there was a higher than target mortality. It was unknown how much BVD could be contributing to the problem in this case as there was a complex history of issues with calfhood illnesses including cryptosporidium and coccidiosis.
• Malignant catarrhal fever (MCF) was confirmed by PCR testing of a blood sample from a six-month-old Jersey bull. The animal showed signs of acute pyrexia, bilateral corneal oedema and copious fetid nasal discharge, all typical clinical signs of MCF due to OvHV-2 infection in cattle.