Interesting cases for September

Cattle
Abortions/mastitis

• There were at least three bovine abortion cases this month where foetal fluids tested positive for BVD antigen in the ELISA on foetal fluids (fluids within thoracic /abdominal cavity). In all these cases, abortion occurred in late pregnancy. There was one foetus in which the fluid also tested positive for antibodies to Neospora caninum in the Indirect Fluorescent Antibody Test (IFAT), indicating both BVD viraemia and seroconversion to Neospora in-utero in that foetus.
• There were several cases in which foetal tissues tested positive for Neospora caninum by PCR testing. The preferred samples for this test are foetal brain or placenta (with cotyledon).
• One farm was experiencing an abortion storm with twelve cows aborting over three weeks in late gestation. Ten aborted cows were tested for antibodies to Neospora caninum and all were positive, raising the suspicion of point source (exogenous) neosporosis.
• Coxiella burnetii was detected by pooled PCR testing of a vaginal swab and placental cotyledon from an aborted cow using the abortion PCR package screen. Detection of Coxiella burnetii may be an incidental finding and additional evidence of foetal infection, for example demonstration of placentitis by histopathology, is required to make a diagnosis of abortion due to Q fever.
• There were several cases of abortion due to Salmonella Dublin this month. One affected dam passed black tarry dung before aborting at two months gestation.
• Staphylococcus aureus was implicated in one case of bovine abortion in the seventh month of gestation. Cultures of the placenta yielded profuse growth of Staphylococcus aureus raising the possibility of aureus associated placentitis. Staphylococcus aureus is recognised as a sporadic cause of abortion in cattle and is most likely to be due to haematogenous spread following infection in the dam.
• There were several cases of mastitis due to Trueperella pyogenes diagnosed in September. Trueperella (formerly Arcanobacterium) pyogenes can cause an acute purulent form of mastitis. Infections occur most frequently in dry cows or heifers before calving. Infections may occur in lactating cows after a teat injury. pyogenes is commonly involved in the aetiology of ‘summer mastitis’.
• Pasteurella multocida was isolated from one of a number of mastitic milk samples from a farm with persistent high cell counts and mastitis Pasteurella species infections are a rare cause of clinical mastitis. The organisms are usually commensals in the oral cavity and upper respiratory tract. Haematogenous or spread via the lymphatics may be the route of spread to the udder under certain conditions. Suckling calves may also be a source of infection. Cow to cow spread is suspected to occur so it is advised that affected cows are removed from the herd as there is usually a poor response to treatment. Cows can become systemically ill and die due to the production of endotoxins by the organisms. Affected cows should be milked last or with a separate cluster until they can be removed from the herd. Cows with teat injuries appear to be at higher risk of infection so maintenance of good teat condition is advised in the prevention.
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Respiratory disease

• IBR virus was detected by PCR testing of nasopharyngeal swabs from an adult Holstein-Friesian cow which was recumbent, open-mouth breathing and drooling. In another case of IBR in adult dairy cattle the virus was detected by PCR of two separate pools of nasopharyngeal swabs, one from recently bought-in cattle and another from homebred animals. Respiratory signs, milk drop and scour had been observed and two abortions had occurred in affected animals. There were at least four other cases of IBR diagnosed by PCR testing in September, one was on a beef unit, and four animals there had died with severe respiratory illness. In that case IBR virus was detected by PCR of pooled lung and tracheal tissue sampled during on farm postmortem.
• On one dairy unit, the farmer had observed that young calves appeared to go through a period of nasal discharge and coughing. A nasopharyngeal swab was taken from an acute, typical case and PI3 virus was detected by PCR testing indicating evidence of active virus Although PI3 is recognised as a cause of respiratory disease in young cattle, some animals may show few or no clinical signs.
• RSV was detected in a pool of three nasopharyngeal swabs from twelve-week-old calves with clinical signs of pneumonia, indicating active RSV infection. RSV is probably the most significant viral cause of respiratory disease in young cattle.
• A three-day-old dairy heifer calf showed signs of respiratory distress and died a short time after. The owner was concerned that there may have been incorrect placement of a stomach feeding tube. On histopathology of lung tissue bronchioles were observed to contain a mix of mucoid material, neutrophils, pigmented material, squames and some macrophages, with some fluid like material also present consistent with meconium aspiration and bronchopneumonia. Whilst aspiration of meconium in calves is not believed to have primary clinical significance, in this case there were significant quantities of material with a neutrophilic response suggesting clinical significance and associated bronchopneumonia. The small amounts of fluid material may have been indicative of aspiration of milk, but overall, this was considered a minor feature and may have been secondary to respiratory embarrassment associated with the pneumonia. If it was assumed that the findings were representative of all affected calves, then it was suggested that attention should be addressed to managing dystocia/difficult calvings.
• A Holstein- Friesian dairy cow was one of several in the herd which showed respiratory signs and mild drop. This cow also developed a swelling in one of the hock joints. Initial testing for antibodies to Mycoplasma bovis during the acute phase gave a high negative result of 57% (>/=60% is a positive result). Resampling after three weeks found a high positive result of 214% in the Mycoplasma bovis ELISA indicating seroconversion consistent with recent exposure. This was a flying herd and it was considered that bovis may have been introduced recently. Further testing to identify underlying factors which could contribute to disease due to Mycoplasma bovis in the adult herd, such as energy, protein or Vitamin A deficiencies, was discussed with the submitting vet.
• Fixed lung tissue was received from a month-old-calf which had been treated multiple times for pneumonia and scour but had failed to respond and was euthanased for Consolidation of the right cranial lung tissue and purulent material within the airways was observed. Histopathology identified necrosuppurative, bronchointerstitial pneumonia with features strongly suggestive of a Mycoplasma bovis-associated pulmonary insult.
• Pasteurella multocida was detected on PCR testing of lung tissue from a six-month-old Limousin cross calf, which had shown signs of respiratory distress at grass and had collapsed and died as the farmer attempted to herd it back to the farmyard for A significant amount of fibrin was seen on the pleural space at postmortem examination. The findings were suggestive of a primary pasteurellosis though no obvious stress factors (e.g travel or extreme weather conditions) were identified. A liver sample was tested to assess trace element status, and the selenium level was found to be below the reference interval at 7.33µmol/kg DM (RI = 11-22.6µmol/kg DM). It was considered that selenium deficiency may have been a contributory factor in the case.
• Trueperella pyogenes was isolated in cultures of swabs from abscesses seen in the lungs of a five-year-old bison which died suddenly at pasture. Ulceration of the soft palate, liver abscessation, collapse of the cranial lung lobes and a small amount of purulent discharge in the airways were observed at postmortem examation. pyogenes is most usually a secondary opportunistic pathogen in lungs, so its isolation did not identify it as a likely cause of sudden death. Histopathology of lung tissue revealed marked diffuse lung oedema with extensive fibrin exudation. While pulmonary congestion and oedema are often considered non-specific changes and may represent agonal phenomena, the presence of fibrinous exudation suggested a peracute pathological process and in conjunction with intralesional bacteria, raised the possibility of a septicaemic event. Examination of further tissues particularly of kidney and brain was recommended but unfortunately these were not available in this case. Evaluation of the brain is especially relevant in cases of sudden death, as significant lesions may be present despite limited findings in other organs and may provide important clues regarding the underlying cause of death. Similarly, renal lesions may help support or refute the possibility of a systemic infectious process.

Gastrointestinal disease

• A six-month-old Aberdeen Angus cross calf presented with mild pyrexia and blood The coccidial oocyst count in a faecal sample was >50,000opg of which 87% were identified as the pathogenic species Eimeria zuernii, confirming coccidiosis in this calf.
• A faecal sample were received from animals on a calf rearing unit in which calves of one to two weeks of age were developing profuse water diarrhoea and three had died. The sample tested positive for Cryptosporidium antigen and Salmonella Coeln was isolated in cultures. S. Coeln is a rarely identified serotype in cattle, which has been associated with contaminated feedstuffs.
• Salmonella Dublin was isolated in multiple cases of gastrointestinal disease in cattle in September including in an eleven-day-old calf with pyrexia, severe scour and dehydration and in a four-year-old Charolais bull which had shown signs of diarrhoea and weight loss in the previous two weeks.
• coli F5 (K99) antigen was detected in at least three cases of diarrhoea in neonatal calves.
• Liver fluke eggs were seen on microscopic examination of two samples from yearling cattle which were not thriving.
• Johne’s disease was diagnosed on serology testing of a twelve-year-old Limousin bull which was losing condition, in an eighteen-month-old Holstein cross bullock which had weight loss, watery diarrhoea and bottle jaw and in a fifteen-month-old Limousin cross bullock with signs of ill-thrift and scour. There were many more cases in the typical age range of three to five years old.
• A two-year old British Blue cross cow showed signs of mild pyrexia and tenesmus with blood and mucous present in the dung. In house parasitology had found no evidence of gastrointestinal parasitism or The animal had a strong positive result for BVD antigen on ELISA, confirming BVD viraemia and likely mucosal disease. It also tested positive for antibodies to Johne’s disease on serology.

Skin and eye disease

• Cutaneous actinobacillosis was the suspected cause of a skin lump on the flank of a three-year-old Highland cow. The animal had been previously showing signs of a laryngeal problem suspected to be due to actinobacillosis. Histopathology of a section of the skin mass identified a focally extensive, chronic, marked pyogranulomatous and lymphoplasmacytic dermatitis/cellulitis with intralesional bacteria and Splendore-Hoeppli reaction (bright pink-staining eosinophilic material surrounding infectious agents or foreign bodies). The changes on histopathology were considered highly suggestive of Actinobacillus lignieresii infection, which may be confirmed by cultures of fresh tissue, though bacteriology was not carried out in this case. Actinobacillus lignieresii can cause ‘wooden tongue’ in the mouth, as well as cutaneous actinobacillosis in the skin. Trauma usually allows its entry.
• Moraxella bovoculi was isolated in aerobic cultures of an eye swab from a dairy calf of less than one week of age which was one of several calves affected in the The finding on culture was considered significant and indicative of Infectious Bovine Keratoconjunctivitis (New Forest eye), though this condition is unusual in such young calves. M. bovoculi was isolated in one other submission, in this case the problem was being seen year-round in cattle from weaning age to adults.
• Biopsy samples from three Holstein-Friesian dairy cattle from a herd which was experiencing an outbreak of suspected teat papillomas were submitted for The histopathological appearance of all the samples confirmed changes typical of teat papillomas of epithelial hyperplasia, hyperkeratosis, acanthosis, and koilocytes (abnormal squamous epithelial cells) (Figure 1). In most cases teat papillomas are caused by bovine papillomavirus infection (including BPV-6, 7, 9 and 10), and the appearance in all three samples in this case support a viral aetiology.

Figure 1: A papilloma on the teat of a cow showing marked epidermal hyperplasia and hyperkeratosis.

Systemic and miscellaneous disease

• There were several diagnoses of babesiosis in cattle this month, including cases from Devon and Dorset.
• BVD viraemia was detected in three animals on pooled BVD PCR testing followed by BVD antigen ELISA testing of individuals from each of the three positive A PI hunt had been initiated in this herd following observation of rising BVD antibody results on bulk milk tank serology. This was one of a number of herds where likely PI animals were identified following pooled PCR testing.
• Chronic pyelonephritis was identified on histopathological examination of renal tissue from an in-calf adult Limousin cow which had shown signs of abdominal pain. Biochemistry had previously identified significant azotaemia suggestive of renal dysfunction, raised globulins consistent with chronic inflammation and hypoalbuminemia which may have been the result of protein losing nephropathy. Gross pathology of the kidney was consistent with pyelonephritis and this was confirmed by histopathology which found evidence of chronic, ongoing extensive changes in the kidney tissue. Pyelonephritis may be caused by ascending urinary infections or by haematogenous spread. The distribution of the lesions in this case was suggestive that it was the result of previous/ongoing bacteraemia with embolic spread to the kidneys. The original focus of inflammation elsewhere in the body (e.g. mastitis, metritis, foot abscess, tooth abscess etc.) may no longer have been present at the time of death.
• Trueperella pyogenes was isolated from a joint fluid sample in a pre-weaned Holstein The farm was experiencing an outbreak of joint ill cases, with no evidence of navel infections observed.
• There were at least four cases of malignant catarrhal fever recorded in September, all of which had some typical clinical signs such as pyrexia, corneal opacity and crusting of the nasal planum and one included a history of co-grazing with sheep. Close contact with sheep is the main risk factor for MCF as sheep can carry and shed the OvHV-2 virus, the cause of MCF, without showing any clinical signs themselves. However, close contact is not always required for transmission as airborne spread can occur.
• An on-farm postmortem revealed large multiple masses in the chest, lungs, kidney, prescapular lymph nodes and abomasum of an adult Shorthorn beef suckler Histopathological evaluation of the submitted tissues revealed an unusual and apparently disseminated neoplastic process. All the organs examined (kidney, thymus, lymph nodes) were markedly to completely effaced by a relatively well-differentiated mesenchymal proliferation. Collectively, the findings were considered highly suggestive of a multifocal metastatic sarcoma. Metastatic sarcomas are considered uncommon in cattle, particularly when presenting with such widespread multi-organ involvement and such a case had not been previously encountered by the farm animal histopathology team at Axiom. Although the histomorphological features clearly supported a mesenchymal neoplasm, the degree of differentiation and relatively low proliferative activity made further subclassification challenging on routine histology alone. Only very limited reports of similarly disseminated sarcomatous processes in cattle were identified in the veterinary literature, including a case of metastatic fibrosarcoma in a Holstein-Friesian cow. In general, bovine sarcomas tend to be reported as locally invasive masses, with distant metastasis occurring less frequently than in many epithelial malignancies. The extensive multi-organ distribution observed in this case therefore represents unusual biological behaviour and may reflect a prolonged disease course, allowing gradual dissemination despite the relatively bland cytological appearance of the neoplastic cells.
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