Interesting cases in March

Cattle
Abortions and mastitis

• BVD virus was detected by the BVD antigen ELISA in foetal fluids in three abortion cases.
•  Salmonella Dublin was cultured from an abortion case from a farm that had had four recent abortions and there were issues with diarrhoea in the calves.
•  Trueperella pyogenes was cultured from foetal stomach contents of an aborted foetus that was the third abortion to occur recently on that farm.
•  Lactococcus sp. was isolated in heavy, pure growth from foetal stomach contents of a calf that was aborted at 120 days gestation. The dam was reported to be well in herself. Lactococcus sp. have been associated with foetal and neonatal infection in cattle and could be the cause of sporadic abortions. The finding was thought to be of significance in this case.
• Foetal fluid from an aborted calf tested positive for antibodies to Neospora caninum indicating in utero Neospora infection.
• Neospora caninum was detected by PCR in tissues from a calf aborted at 4-5 months gestation.
• Mastitic milk samples from a pregnant beef heifer tested positive for Mycoplasma bovis by PCR and Trueperella pyogenes was isolated in bacterial cultures. Mycoplasma bovis is a known cause of intractable mastitis in cattle. Trueperella (formerly Arcanobacterium) pyogenes can cause an acute purulent form of mastitis and may have been acting as an opportunistic secondary invader in this case or may have been the primary pathogen. Infections occur most frequently in dry cows or heifers before calving. Infections may occur in lactating cows after a teat injury. T. pyogenes is commonly involved in the aetiology of ‘summer mastitis’.

Respiratory disease

• Widespread lung abscesses were observed at PME of an eight-month-old Aberdeen Angus bull calf that had been ill thrifty prior to death and was the second to die in the group. Pasteurella multocida was isolated in aerobic cultures and Mycoplasma bovis, Pasteurella multocida and Mannheimia haemolytica were detected by PCR. Severe and chronic changes in the lungs were present which were consistent with virulent Mycoplasma bovis infection and secondary bacterial infection.
• Mannheimia haemolytica was isolated in cultures and was detected along with Pasteurella multocida in the respiratory pathogen PCR testing of lung tissue received from a yearling beef bull that had died suddenly.
• Mycoplasma bovis was suspected to be the cause of pneumonia following histopathological examination of lung tissue from a four-month-old bucket reared Wagyu calf. Severe lung changes with eosinophilic coagula, typical of M. bovis infection and evidence of secondary bacterial pneumonia was present.
• Fibrinous bronchopneumonia and pleurisy was identified on examination of tissues from a six-month old Wagyu cross calf. Mycoplasma bovis, Histophilus somni and Pasteurella multocida were detected by PCR testing of lung tissue.
• RSV was detected in post mortem tissues from a six-month-old Belgian blue cross male calf. There was severe coughing in the group and three calves died overnight. In addition to RSV, Histophilus somni, Mycoplasma bovis and Pasteurella multocida were also detected by PCR testing of lung tissue. Histopathology identified chronic, ongoing changes consistent with enzootic calf pneumonia/bovine respiratory disease complex (BRD). There was a severe and ongoing necrotising bronchiolitis that in calves is normally associated with a pneumotropic viral infection. Syncytial cells were observed supporting the positive RSV PCR result. Secondary bacterial infection was present consistent with the bacterial pathogens detected by PCR. In addition, plasmalymphocytic peri-airway infiltrate consistent with the Mycoplasma bovis PCR result was seen, but it was noted that Mycoplasma dispar, canis, canadensis and/or alkalescens could also be involved.

Gastrointestinal disease

• A total of 464 submissions for Johne’s disease serology and faecal PCR testing from cattle were received this month, with 146 submissions, including a total of 284 individual samples, testing positive. Johne’s disease was diagnosed by serology in a yearling bullock that was underweight and scouring and had not responded to anthelmintic treatment. A cow that had twins and then rapidly lost condition and started scouring was euthanased and tissue sent for histopathology. There were gross lesions in the intestine that were identified as multifocal mucosal ulceration and diffuse granulomatous enteritis, the appearance being consistent with a case of Johne’s disease. Special staining identified abundant acid-fast bacteria within macrophages expanding the intestinal submucosa supporting the diagnosis.
• A strongyle egg count of 600epg was recorded in a group of nine-month-old calves that had received no worming treatment, indicating the likely cause of the reported ill thrift was parasitic gastroenteritis.
• F5 (K99) E.coli antigen was detected in scour samples from calves less than five days of age which were falling ill and rapidly deteriorating and dying.
• Yersinia enterocolitica was isolated from a faecal sample from a cow that had calved two weeks previously, had retained placenta and was now scouring. It was thought that the isolate could be of significance in this case of scour. Yersiniosis most often occurs in animals with concurrent disease or those that are immunosuppressed.
• Salmonella Mbandaka was isolated from faecal samples from Holstein cows with milk drop and rumination drop, pyrexia and scour of five days duration.
• Salmonella Montevideo was isolated in a case where 60-70 cows in a Holstein herd had blood in their faeces.

Skin and eye disease

• Listeria monocytogenes was isolated from eye swabs from cattle with conjunctivitis in two submissions.
• A mass removed from the distal third of a tail of a bovine was identified as a vascular harmartoma by histopathology. It was noted that the method of removal (rubber ring) had resulted in suboptimal tissue preservation in this case, though neoplasia and fibropapilloma could still be ruled out.

Systemic and miscellaneous disease

• A total of 366 submissions were received for BVD antigen testing in cattle in February, with 29 submissions, including a total of 48 individual samples, testing positive.
• Babesia sp. were detected by PCR on a blood sample from a cow that had red urine that became port coloured after two days. The mucous membranes were seen to be pale but there was no pyrexia and the PCV was within reference range. Otherwise, the clinical examination was unremarkable. The cow had been housed since November shortly after it calved.
• Clostridium chauvoei, the cause of clostridial myositis (Blackleg), was detected by FAT testing of smears of affected muscle tissue in a stirk. There had been two sudden deaths in the group of six to seven-month-old unvaccinated stirks.
• Malignant Catarrhal Fever was diagnosed by PCR testing in six animals from five separate submissions.
• Tissues and a faecal sample were received from a one-week-old Jersey cross dairy heifer calf that had been sick and scouring for two to three days prior to death. The lungs and liver were grossly abnormal at post mortem examination and a large cystic structure was present close to the gall bladder. The faecal sample tested positive for Cryptosporidium. On histopathology there was an extensive necrosuppurative bronchopneumonia with intralesional bacteria and foreign material in the airways suggestive of aspiration pneumonia. There was also some meconium present indicating a degree distress at calving. In the liver there was minimal multifocal and random suppurative necrosis indicating likely terminal bacteraemia. The cystic structure in the liver was identified as a serous cyst. These are occasionally found attached to the liver capsule in calves, lambs and foals. The origin of these is not known; they may be congenital biliary anomalies or of endoderm origin. These are rarely seen in older animals, which suggests a large proportion of them involute in the early postnatal period.
• A 13-year-old Belted Galloway cow died and underwent PME. It was noted that the peritoneum was significantly thickened on the hepatic surface and fibrin tags were present around the liver. Although autolysis hampered the examination of tissues, the overall appearance was suggestive of a metastatic neoplasm of uncertain histogenesis, though biliary or intestinal carcinoma were thought to be possible.
• Hypogammaglobulinaemia was identified in a one-week-old male calf with joint ill and scour. The ZST result was 2 units indicating complete failure of colostral absorption.
• A gram-negative bacteraemia/septicaemia was found to be the cause of death on histopathology of tissues from a Holstein calf. The calf had had scour at five weeks of age and initially improved but relapsed and died two weeks later. PME identified multiple punctate ulcers in the abomasum, hepatomegaly and severe peritonitis. Microscopically, multifocal mucosal infarction with bacterial emboli and thrombosis were identified in the abomasal tissue. Infarcts at this site can be caused by gram-negative septicaemias and there was evidence of bacterial embolisation associated with the lesions. Vasculopathy was also observed in small intestinal samples that could be linked to the same pathogenesis. However, as vasculopathy may also be caused by BVD virus infection it was suggested that this should be excluded as a possible underlying cause in this case.