Interesting cases in April

Cattle
Abortions/mastitis

• BVD viraemia was detected by antigen ELISA testing of foetal fluids in several cases this month, of which one farm had evidence of an active BVD outbreak, and a further had had six late term abortions in the previous three months.
• Coxiella burnetii, the causative pathogen in Q fever, was detected by PCR testing of a placental sample from an aborted foetus. Detection of Coxiella burnetii in placental tissue may be an incidental finding and does not necessarily indicate that Q fever was the cause of abortion. In this case the foetus was available but was severely autolysed so only the placenta was available to test. It was suggested that a fresh foetus was examined if further abortions occurred and to consider histopathology in addition to Q fever PCR to reach a definitive diagnosis if tissues were suitable.
• There were several cases of abortion in which foetal tissues tested positive for Neospora caninum by PCR. In these cases, it was advised that further investigation could be carried out by histopathology to determine if neosporosis was the cause of the abortion.
• In one case of late term abortion both Coxiella burnetii and Neospora caninum were detected by PCR testing of foetal tissues, these results highlighting the risk associated with making a definitive diagnosis based on PCR tests alone.
• Salmonella Typhimurium was isolated from foetal stomach contents in a case where the dam had aborted, was scouring and sick and had rapidly lost
• Salmonella Dublin was isolated from placenta of one abortion case, which was the fourth to occur recently on that farm.
• A Salmonella was detected by PCR testing of placental tissue in one case of abortion in the seventh month of gestation. The finding may have been significant. However, attempts at culture were unsuccessful so no serotype could be established for the Salmonella species present.
• Campylobacter fetus was cultured from foetal stomach contents in an abortion at seven months
• Trueperella pyogenes was cultured from foetal stomach contents in one case of abortion in the seven month of pregnancy. pyogenes is usually a sporadic cause of abortion in cattle. On this farm this was the third recent abortion, though this was the first to be examined.
• Bacillus licheniformis was isolated from a case of clinical Bacillus licheniformis is an environmental organism that can be a sporadic cause of mastitis. The organism is prevalent in
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Respiratory disease

• Bovine coronavirus, Pasteurella multocida and Mannheimia haemolytica were detected by PCR of a swab taken from the bronchial bifurcation at postmortem in a recently bought-in Aberdeen angus cross yearling. There had been three deaths since arriving on the farm five days previously. Severe, acute bacterial bronchopneumonia triggered by the recent stress of transportation was the likely cause of death. The significance of the coronavirus was uncertain though it may have been contributing to the respiratory disease complex.
• A severe and fulminating bacterial pneumonia was identified by histopathology of lung tissue from a cow. Bacterial pneumonia was suspected at postmortem examination and PCR testing of the lung tissue detected Mannheimia haemolytica as the only respiratory pathogen present in the respiratory multiplex PCR panel. The herd had a recent history of issues with acidosis in cows, and this stressor could be considered a possible trigger for the pneumonia.

Gastrointestinal disease

• Multiple diagnoses of Johne’s disease were made. In one case two two-year old steers were seen in poor condition with bottle -jaw and pale mucous membranes and one of the two had watery Both were highly positive for antibody to Johne’s disease on serology and a pooled PCR test on faeces was positive for Mycobacterium avium paratuberculosis (MAP) with a low Ct value of 21 indicating heavy shedding of MAP.
• There were numerous cases of suspected coccidiosis in calves this month. One case which was confirmed by coccidial identification was the second calf on farm to be affected with The first had been treated based on clinical signs and had improved. The coccidial oocyst count in the faecal sample submitted was very high at >50,000opg, with 98% of the oocysts present being of the pathogenic species Eimeria bovis (60%) and Eimeria zuernii (38%).
• Pepsinogen was above the reference interval (RI = 0.00-1.50iu/l) in eleven out of twelve six- to eight-month-old dairy cross calves which were scouring and rapidly losing weight. Of the eleven with raised pepsinogen nine of these were above 5iu/l when the severity of abomasal damage due to parasitism would be apparent clinically.

• Bovine coronavirus was detected in scour samples from young On one farm coronavirus and cryptosporidium antigen were detected in a faecal sample. The same farm had also reported recent cases of rotavirus. As with rotavirus, concurrent infection with coronavirus and cryptosporidiosis can exacerbate clinical signs leading to significantly increased morbidity/ mortality.
• On one farm five out of the last six calves born had died within 24-48 hours of A faecal sample taken from one of the calves which died tested positive for E.coli F5 (K99) confirming a diagnosis of enterotoxigenic E.coli (ETEC) infection. The Escherichia coli isolate cultured from the sample showed in-vitro resistance to multiple antimicrobials on antimicrobial sensitivity testing by disc diffusion.
• Salmonella Barranquilla was isolated from faecal samples from a six-day-old dairy bull calf with Barranquilla is a rarely isolated serovar of Salmonella enterica which is not host adapted. There is little evidence of pathogenicity in cattle and therefore it can be considered a sporadic/incidental finding. It may originate from poultry, environmental or other sources.
• On one farm several calves were pyrexic at less than two weeks of age. Some but not all also developed scour. Salmonella Dublin was isolated in faecal cultures from one of the affected

Skin and eye disease

• Trueperella pyogenes and Pseudomonas aeruginosa were isolated on aerobic culture, and Bacteroides pyogenes on anaerobic culture, from a cow with a severe, non-resolving foot All three isolates were considered potentially significant. Bacteriodes species are commonly isolated in cases of infectious foot disease in cattle, including interdigital necrobacillosis (footrot) and digital dermatitis where they act as secondary invaders in damaged tissue. Trueperella pyogenes readily colonises damaged and necrotic tissues, inciting further inflammation and production of pus. Pseudomonas aeruginosa can act as an opportunistic pathogen in existing foot lesions contributing to tissue necrosis and complicating treatment and healing due to production of a slimy biofilm which tends to make it resistant to topical antibiotics and antiseptics.
• Cutaneous actinobacillosis was suspected to be the underlying cause of a lump which had been surgically removed from the face of a Charolais cross cow. Histopathology identified focally extensive, chronic, marked pyogranulomatous and lymphoplasmacytic dermatitis/cellulitis with intralesional bacteria and Splendore-Hoeppli material (an intensely pink/red (eosinophilic) cuff or star-like material that forms around microorganisms or inert substances in tissue. It appears as radiating clubs, spikes, or granular arrays.) Gram staining identified gram-negative coccobacilli consistent with Actinobacillus lignieresii. (Figure 1&2) Actinobacillus lignieresii can cause ‘wooden tongue’ in the mouth, as well as cutaneous actinobacillosis in the skin.

Figure 1&2: HE (top) and Gram stain (bottom). Clusters of bacteria (gram negative on gram stain) surrounded by Splendore-Hoeppli material in a lump removed from the face of a cow with suspected Actinobacillus lignieresii infection.

• Skin biopsies were received from a five-day-old calf showing signs of flaking/scaly skin. Histopathology identified a hyperplastic and perivascular dermatitis. This is a relatively common cutaneous reaction to a wide range of insults and is not aetiologically specific. However, other changes seen included compact orthokeratotic hyperkeratosis forming mats overlying the epidermal surface and a suspicion of disorderly or abnormal hair follicle growth, which could be considered compatible with a mild form of congenital icthyosis. Typical parakeratotic hyperkeratosis as seen in zinc deficiency was not seen and therefore considered less likely in this case. Congenital icthyosis is a rare, inherited genetic disorder in cattle and can occur in severe, lethal forms or milder cases such as this.

Systemic and miscellaneous disease

• There were several cases of suspected mucosal disease this month. On one farm a six-month-old calf was off feed, had mucosal erosions in the oral cavity and abnormal ‘gloopy’ faeces. The animal tested positive for BVD antigen with a high ‘OD’ (Optical Density) in the ELISA test confirming BVD viraemia. In another case a four-year-old Highland cow, which was showing signs suspicious of reticuloperitonitis, was found to be BVD viraemic in the antigen ELISA test and was seronegative for BVD antibody. The cow had produced a confirmed BVD PI calf the previous year but was reported to have had a previous negative result for BVD virus by tissue tag testing. Given the history and clinical signs, it was thought likely that this was a PI animal which had either a false negative result on tissue testing or had been missed out of the PI hunt in error.
• Postmortem tissues were received from a 20-month-old bullock which had presented with neurological There was a reduced palpebral reflex, and no menace response was present. When walking the animal was unsteady, ataxic and was circling and head pressing. Diarrhoea was also observed. Grossly the liver appearance was reported as ‘very abnormal’. Histopathology identified severe, ongoing and chronic necrosuppurative hepatitis with chronic portal-bridging fibrosis and biliary hyperplasia, which would account for signs of hepatic encephalopathy. It was suggested that the biliary hyperplasia could be the result of an ongoing inflammatory process, possibly due to ascending inflammation extending up from the bile duct, or the result of abscessation in the liver. A toxicity (e.g. ragwort, chronic copper toxicity, mycotoxicosis) could also be possible. Biliary obstruction caused by liver fluke was also considered, though no fluke were seen in the tissue sections examined. The more acute necrotising hepatitis may have been part of an ongoing inflammatory process or due to secondary bacterial infection.
• Lung tissue was submitted from a 51-day-old pre-weaned Holstein heifer The farmer reported that six calves of the same age had died over a 10-day period. Calves presented initially with signs of pneumonia but responded poorly to treatment with tulathromycin. PCR testing of lung tissue detected Mannheimia haemolytica. Changes in lung on histopathology were consistent with a septicaemia, of which M.haemolytica may have been the cause. However, salmonellosis was considered as a further possible differential and ancillary testing for this was suggested.
• Mycoplasmopsis bovis (formerly Mycoplasma bovis) was detected in two samples of joint fluids from calves on the same farm. The vet reported that there had been multiple cases of joint effusion and lameness in calves of six to eight weeks of age. There was no evidence of navel infection but postmortem inspection of the lungs of an affected calf identified purulent material in the cranial middle and accessory lung lobes, suggestive of bacterial involvement. Changes seen in the lung tissue on histopathology included a prominent lymphoplasmacytic peri-airway infiltrate with follicle formation, areas of atelectasis, some bronchiolitis fibrosa obliterans and fibrosis of airways, frequent large multinucleated cells, and a lesser suppurative bronchopneumonia. The lymphoplasmacytic infiltrate was considered strongly suggestive of a Mycoplasmopsis spp infection, in this case most likely Mycoplasmopsis
• Streptococcus dysgalactiae was isolated from a sample of joint fluid from a calf with signs of umbilical vein abscessation and septic arthritis
• Mycoplasmopsis bovis was detected by PCR testing of a swab from the right ear of a six-week-old Limousin calf with mild pyrexia and head tilt of 48hrs Thick purulent material was observed in the ear canal when swabbing. Otitis rarely occurs in isolation in cases of M.bovis infection but often because of spread from the respiratory tract via the eustachian tubes to the middle and inner ear.
• A yearling heifer showed signs of pitting brisket and ventral Mucous membranes were noted as pale on clinical examination and there was pyrexia (39.9⁰C). Blood was taken for further investigation and haematology testing revealed a significant lymphocytosis of 20.2×10^9/l (RI = 2.5-7.5×10^9/l). A Pathologists Haematology Review (PHR) was requested to investigate the abnormal findings. Blood film examination confirmed moderate lymphocytosis with a predominance of small to medium lymphocytes. Lymphocytosis may be due to chronic inflammation or lymphoproliferative neoplasia (for example chronic lymphocytic leukaemia or leukaemic lymphoma).
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