Interesting cases in February

Cattle
Abortions and mastitis

• Bacillus licheniformis was cultured from two bovine abortion submissions this month, both of which occurred in late gestation.
• Two Hereford cows in a 40-cow herd both aborted on the same day around the eighth month of pregnancy. Listeria monocytogenes was cultured from one of the two foetuses. In another Listeria abortion, case a Friesian cow aborted at eight months gestation and was the fifth in the herd to abort recently. Listeria monocytogenes was identified by both culture and PCR testing in that case.
• Salmonella Mbandaka was identified as the isolate in a case of abortion at six months gestation.
• Staphylococcus vitulinis was isolated in moderate growths from an eight months gestation aborted foetus out of a Charolais heifer. The isolate in this case was considered an unlikely pathogen but it couldn’t be ruled out as a possible cause of sporadic abortion.
• Neospora caninum was detected by PCR in foetal tissues of a cow that aborted in the sixth month of pregnancy and was otherwise clinically well.
• Antibodies to Neospora caninum were detected in the foetal fluids of stillborn calves in two submissions. In one case, the dam was reported to have aborted the previous year.
• Leptospira sp. was detected by PCR of foetal kidney in one case of bovine abortion this month.
• Pasteurella multocida was isolated from a milk sample from a two-year-old lactating heifer with chronic recurring mastitis that had been treated with multiple antibiotics. P. multocida is an uncommon cause of mastitis in cows and in some case can be fatal due to the presence of endotoxins.
• Candida sp. mastitis was identified in two cows on the same farm with clinical mastitis and the presence of clots.

Respiratory disease

• IBR virus was detected in several respiratory cases this month. In one case, an animal with purulent nasal discharge died and purulent material was observed in the trachea at PME. PCR testing of lung tissue detected IBR along with Mycoplasma bovis, Histophilus somni and Pasteurella multocida. Lung histopathology was supportive of the involvement of all these respiratory pathogens (although the bacteria are likely to be opportunistic invaders).
• RSV was detected as the primary respiratory pathogen by PCR testing in at least 36 submissions, in combination with PI3 in at least four submissions, in combination with Bovine Coronavirus in at least 16 submissions and with both PI3 and Coronavirus in at least one case. In a number of cases, bacterial respiratory pathogens were also detected and where these were detected in lung tissue or the lower airways these were considered significant (at least as opportunistic pathogens). RSV was detected in lung tissue from a three-month-old calf that was the only mortality in a group of 50 that had sudden onset coughing and pyrexia. Abscessation was observed in the lung tissue at PME and histopathology confirmed chronic-active, plasmalymphocytic and suppurative bronchointerstitial pneumonia with bronchiolitis fibrosa obliterans consistent with viral infection and secondary bacterial infection. Histopathology remains the best single method of characterising the complexity of bovine respiratory disease, when a carcase is available.
• PI3 was detected by PCR in at least five further cases of bovine respiratory disease this month and in combination with coronavirus in at least three cases.
• Mannheimia haemolytica was isolated in cultures of lung tissue from an eight-week-old weaned Holstein-Friesian dairy calf that died after a short bout of respiratory illness. A marked fibrinous reaction was observed at PME throughout the thorax and abdomen. Histopathology identified a fibrinosuppurative pleuritis consistent with Mannheimia infection and the presence of fibrin in the abdominal cavity (polyserositis) suggested that the lung changes were part of a septicaemic process rather than primary pneumonia. Underlying risk factors can include failure of passive transfer, underlying disease (e.g. BVD), trace element deficiencies, and stress due to moving, mixing or adverse weather.
• Pasteurella multocida was identified by PCR testing of lung tissue from youngstock with respiratory disease. In one case, histopathology identified a likely primary viral insult with evidence of secondary infection.
• A seven month-old heifer recently purchased from market along with four others from a different farm was found down in the shed in respiratory distress and unable to rise. It had been noted by the farmer that there had been some coughing in the group. PCR’s of affected lung tissue detected Mycoplasma bovis, Pasteurella multocida and Mannheimia haemolytica. There were severe lung changes seen on histopathology. A severe, extensive, chronic-active, necrosuppurative and fibrinohaemorrhagic bronchointerstitial pneumonia with intralesional bacteria was confirmed .The predominant lesions were an acute alveolar necrosis (which can be caused by either Mycoplasma bovis or Mannheimia haemolytica), acute suppurative infiltrate (associated with M. haemolytica) and caseonecrotic airways (caused by M. bovis). Co-infections with M. bovis and M. haemolytica are common, and recent studies suggest M. haemolytica results in worsening of the respiratory disease caused by M. bovis.
• Mycoplasma bovis, Pasteurella multocida and Histophilus somni were detected by PCR of lung tissue from a four-month-old Aberdeen Angus cross calf. Without histopathology, it is difficult to establish the relative roles of these potential pathogens, and whether they are superimposed on older airway damage, the cause of which is no longer present.
• Trueperella pyogenes and Histophilus somni were isolated in cultures of lung tissue and Mycoplasma bovis was detected by PCR of lung tissue in a case of chronic pneumonia in an 11-month-old steer.
• Convalescent samples were taken for paired serology from a group of yearling beef finishers. All five sampled animals had significant rising titres to Mycoplasma bovis confirming recent exposure to this pathogen, three of the five had evidence of recent exposure to PI3 and two had rising titres to bovine coronavirus.

Gastrointestinal disease

• A total of 525 submissions for Johne’s disease serology and faecal PCR testing from cattle were received in February, with 176 submissions, including a total of 286 individual samples, testing positive. In one submission, a fattening bullock showed signs of being thinner than the rest of the group and was scouring. It was a homebred animal and there was no known history of Johne’s disease on the farm, but no testing had been carried out. The animal tested positive for antibodies to Johne’s disease on serology. On another farm an 18-month-old Limousin heifer was in very poor body condition despite being given good silage and having a good appetite. This animal was also seropositive for Johne’s disease. In a faecal sample from a 14-month-old steer that was scouring and losing condition acid-fast bacteria typical of MAP were seen in clumps in a ZN smear, consistent with a diagnosis of Johne’s disease.
• Parasitic gastroenteritis was suspected to be the cause of fetid haemorrhagic scour in a heifer with a faecal egg count of 900 strongyle epg.
• Evidence of abomasal disease due to parasitism was identified in a three-year-old Hereford bull that had been losing condition over winter and had watery diarrhoea. The animal was found to be hypoalbuminaemic and had a suboptimal urea level. The pepsinogen level was high at 5.45 iu/l (ref <1.5 iu/l) indicating the likely cause of the signs as parasitic gastritis. Sometimes in these cases, worm egg counts can underestimate the total worm burden, as many of the worms are not laying eggs (but still causing damage).
• Liver fluke eggs were observed in a faecal sample from an eight-year-old Highland cow that was losing condition and scouring, confirming patent fascioliasis.
• Fixed samples of abomasum were examined from a calf that was the second to die per acutely on the farm. Histopathology identified a multifocal erosive/ulcerative abomasitis and gram staining revealed the presence of gram-positive rods in the abomasal wall consistent with a diagnosis of clostridial abomasitis. C. perfringens is implicated in the aetiology of abomasal bloat/ulceration, and improvements in environmental hygiene were advised. High milk osmolality and poor quality milk powder may reduce abomasal emptying and as such can also act as risk factors.
• Abomasitis was also identified in an eight-day-old calf that had shown signs of scour shortly before death and abomasitis and peritonitis were observed grossly at post mortem examination. Examination of the abomasal wall by histopathology was hindered by marked autolysis, but clusters of bacteria resembling Sarcina sp. were seen within the serositis on the liver surface. Sarcina sp. are often associated with dysbiosis and the finding was considered supportive of this being a case of abomasitis.
• Abomasal ulceration was confirmed by histopathology as the cause of death in a yearling dairy heifer that had been switched to a TMR three weeks before death. The main finding at PME was a severe melaena that originated from the abomasum.
• Salmonella Dublin and rotavirus were detected in faecal samples from calves with haemorrhagic scour at four days of age. The dams had received a rotavirus/coronavirus scour vaccine.
• Salmonella Dublin and Cryptosporidium were diagnosed in a four-day-old Holstein calf with scour.
• Salmonella Typhimurium was diagnosed in adult Holstein cows that showed some response to treatment. In total, salmonellosis was identified as the cause of scour in adult dairy cattle in at least five submissions this month.
• F5 (K99) antigen was detected in a scour sample from a neonatal calf and when cultured the Escherichia coli isolate was shown to have in-vitro resistance to multiple antibiotics.
• Yersinia pseudotuberculosis was cultured from a faecal sample submitted from a group of six-month-old dairy heifers that were scouring and losing weight and had mild pyrexia. Investigation for gastrointestinal parasites and liver fluke had been negative.
• 10-15% of a dairy herd, mainly first calvers, were affected with sudden onset milk drop and diarrhoea with mucus and tenesmus. Three samples from affected cows were tested in the PCR for bovine coronavirus in faeces and all three were positive confirming a diagnosis of Winter Dysentery.

Skin and eye disease

• Moraxella bovis and Moraxella bovoculi were isolated from swabs from calves where there were widespread eye issues in calves that responded poorly to treatment. In another case of problem eyes, Moraxella bovoculi and Streptococcus dysgalactiae were isolated in bacterial cultures.
• Bought-in calves on one farm had flaking skin and bald patches on the head and face. The farm had had issues with ringworm in the past. A dermatophyte sp. was detected by PCR of hair plucks/skin scrape confirming dermatophytosis (ringworm) as the cause of the skin lesions.
• Fibropapilloma was strongly suspected to be the cause of extensive growths on the teats and inguinal area of a 20-month-old British Blue cross heifer. Necrosis and devitalisation of the submitted tissue prevented definitive diagnosis by histopathological examination.

Systemic and miscellaneous disease

• A total of 372 submissions were received for BVD antigen testing in cattle in February, with 37 submissions, including a total of 69 individual samples, testing positive. BVD viraemia was identified in two animals that were considered to be very likely to be BVD persistently infected. One was a sickly calf that required euthanasia and the other was a poorly thriven sixteen-month steer that hadn’t improved with anthelmintic treatment. On one farm two calves born to bought-in in-calf, heifers had congenital cataracts and tremors. One of the heifers and her calf were tested and the calf was found to be BVD viraemic in the PCR test and the cow was seropositive for BVD virus. BVD virus was detected by antigen ELISA testing of foetal fluids from an aborted calf found in the field on another farm.
• Ovine herpes virus-2 was detected in a blood sample from a bovine with a temperature of 41.2C, purulent nasal discharge and crusting of the nasal planum as well as eye abnormalities and seizures. The finding of OvHV-2 confirmed a diagnosis of Malignant Catarrhal Fever (MCF) in this animal.
• There was evidence of exposure to Mycoplasma bovis in three Holstein-Friesian cows from one herd that had a history of swollen joints and poor response to treatment. High antibody levels to M. bovis in two of the three cows suggested recent exposure to this pathogen.

Nephritis was suspected to be the cause of death in a calf that was the second to die suddenly at around two months of age. The calves were noted to be dehydrated prior to death but otherwise there were no premonitory signs. Histopathology identified large areas of significantly compromised renal cortical tissue likely to be associated with renal failure. Although some inflammation was noted, the most striking change observed was the small size and rudimentary nature of the tubules, suggesting a primary dysplasia. Underlying teratogenic (viral or toxic exposure) or perhaps genetic cause(s) were considered. In this case, raised muscle enzymes CK and AST and a low GSH-Px level of 18U/ml RBC was suggestive of possible White Muscle Disease (WMD) in addition to the renal abnormalities. Muscle histopathology is very useful in confirming a diagnosis of WMD; degeneration is usually polyphasic.

• Failure of passive transfer of immunity was identified in a group of calves of which several had died at around a week of age following scouring and respiratory signs. PME had revealed evidence of septicaemia. A recent change in management that involved leaving the calves with the mothers for up to 48 hours was suspected to be the root cause of the problem.
• Seven adult suckler cows tested positive for antibodies to tick borne fever with high titres indicating recent exposure to Anaplasma phagocytophilum. The reason for testing was not provided in this case.
• A Proteus sp. was cultured in moderate growth from a urine sample from a dairy cow with cystitis and suspected pyelonephritis that had a poor response to treatment with penicillin/streptomycin antibiotic.