Interesting cases in May

Cattle
Abortions and mastitis

• BVD viraemia was suspected on BVD antigen ELISA testing of foetal fluid in a calf aborted at five months gestation.
• Salmonella Dublin was isolated from the stomach contents of a calf aborted at four to five months gestation in a dairy herd that had been intermittently positive on S. Dublin bulk milk serology. The cow had been pyrexic (39.6oC) prior to aborting. S. Dublin was also isolated from two vaginal swabs from maiden heifers that were aborting in a Holstein-Friesian herd where there had been a history of Salmonella infection in the same field following turnout the previous year.
• Trueperella pyogenes was isolated from the stomach contents of a foetus aborted at seven months gestation. T. pyogenes associated abortion often follows development of a septic focus or systemic illness in the dam.
• Several cases of Neospora associated abortion were suspected with the detection of Neospora on PCR in foetal tissues and seroconversion of aborting cows. Confirmation of neosporosis requires histopathology of foetal heart and ideally foetal brain.

Respiratory disease

• Cases of IBR diagnosed on PCR testing included on pooled nasal swabs from two dairy heifers with milk drop, pyrexia, nasal discharge and increased lung and tracheal sounds on auscultation. Active seroconversion to IBR was also reported in one herd.
• Cases of PI3 infection diagnosed on PCR testing included in mixed batches of calves in one herd, all of which were sick and exhibiting respiratory signs, nasal and ocular discharge, as well as scour.
• Cases of RSV infection diagnosed on PCR testing included a bought in calf that developed acute pneumonia and died after five days despite antibiotic treatment. On PME, there was widespread fibrinopurulent pleurisy and, in addition to RSV being detected, Mannheimia haemolytica and Pasteurella multocida were also detected, consistent with secondary bacterial infection.
• Coronavirus was detected by PCR on several occasions, either as the sole viral agent or in mixed infections with other viruses. The role of coronavirus in bovine pneumonia is not clear. It may be significant as part of a mixed infection but may also be found in the respiratory tract of healthy animals.
• A heifer bought in to a herd lost weight rapidly over the first two weeks. Heart sounds were muffled on auscultation due to increased respiratory rate and effort and the animal was pyrexic (40.1oC). The heifer was treated symptomatically and concerns over lungworm were confirmed with a positive Baermann’s test.
• One of a number of dopey calves born in a herd died at 36 hours of age. Calving had been going very well until recently when there had been several losses. On PME, the urachus appeared congested and petechiae and oedema were present throughout the tissues. Histopathology detected a severe, fulminating bacterial pneumonia, the most likely cause of which was Mannheimia haemolytica. There was some proteinaceous material seen, raising the possibility of milk aspiration, but it was not possible to determine if this predisposed to the bacterial pneumonia or was a result of the pneumonia. Minimal meconium was also seen in the lung, which could suggest a degree of distress at calving, and this also may have predisposed to a bacterial infection. Other risk factors for bacterial pneumonia include failure of passive transfer, underlying disease, mineral deficiencies and stress.

Abundant degenerate neutrophils (often with streaming nuclei; oat cells) (arrows) and fibrin (*) in a calf with fulminating bacterial pneumonia likely caused by Mannheimia haemolytica

Gastrointestinal disease

• A five-week-old calf died relatively suddenly and, on PME, the abomasum was necrotic and haemorrhagic. Histopathology was consistent with a marked acute abomasitis. No fungal organisms were seen and this was likely to be a bacterial abomasitis, however the exact cause was not determined on histological examination. Potential underlying factors can include inadequate milk administration, large milk feedings, cold milk, carbohydrate-rich lacto replacer, oesophageal tube feeding or inadequate equipment hygiene. Potential bacterial pathogens include Clostridium perfringens type A, Sarcina species, E. coli, Lactobacillus species and Campylobacter species.
• A group of two-month-old calves at pasture were ill thrifty and had loose faeces. A faeces sample detected > 50,000 epg of Toxocara vitulorum. This ascarid nematode undergoes a period of arrested development in the somatic tissues of adult cattle and is transmitted to suckling calves via the milk. It may cause ill thrift and scour and sometimes slight abdominal distension in calves up to six months old.
• Elevated pepsinogen levels consistent with significant abomasal parasitism were reported in several animals, with ill thrift being the most commonly reported clinical sign.
• Several cases of fasciolosis were diagnosed on coproantigen ELISA and faecal microscopy. Clinical signs included ill thrift and bottle jaw. An inappetant, thin Longhorn heifer with decreased rumen activity was strongly seropositive for liver fluke, suggesting current infection, and the animals also had evidence of vitamin A deficiency.
• Salmonella Typhimurium was isolated on at least four occasions this month. Three cases occurred in cows that had recently calved; a Hereford cross suckler cow and two Holstein-Friesian dairy cows in different herds. All three had watery scour, two were reported to be dull and one was reported to be pyrexic (40.3oC).
• At least two cases of Salmonella Dublin associated scour were reported this month.
• Salmonella Enteriditis was isolated from a faeces sample from a dairy herd where presumably animals were scouring. This serotype is rarely reported in cattle and is more commonly reported in chickens.
• A total of 518 submissions for Johne’s disease serology and faecal PCR testing from cattle were received this month, with 164 submissions, including a total of 295 individual samples, testing positive. The youngest animal reported this month was 17 months old.

Skin and eye disease

• A suckler cow developed abscesses primarily over the throat and neck with some extending over the remainder of the body. Streptococcus dysgalactiae was isolated in pure heavy growth from a sample of pus and, although mainly associated with mastitis, this can act as an opportunistic pathogen in other infections e.g. secondary to skin trauma.
• Tissues were received from a fourth lactation British Friesian cow which, over the course of a few days following turn out, developed hardened, thickened skin over one side, similar to photosensitisation although the cow was black in colour. There was no known history of toxin ingestion or chemical treatments. Histopathology was consistent with a severe necrotising dermatitis and changes suggested an outside-in process. Possible differentials included a radiation burn, thermal burn or chemical burn. We understand that subsequently all the affected skin sloughed and was left to heal by second intention, and that the cow’s condition is improving.

Severe necrotising dermatitis in a British Friesian cow (photo: Eleanor Stafford, Axe Valley Large Animal Vets)

Systemic and miscellaneous disease

• A total of 449 submissions were received for BVD antigen testing in cattle this month, with 41 submissions, including a total of 63 individual samples, testing positive. In one case, an 18-month-old heifer had dramatic weight loss over the three weeks following turnout and developed haemorrhagic diarrhoea, consistent with a diagnosis of mucosal disease. The animal was the only one affected in the group.
• At least seven animals were diagnosed with MCF on PCR testing of heparin blood samples. Presenting signs reported included pyrexia, uveitis, corneal oedema, nasal discharge and encrusted nares. One infected Limousin cow was reported to be improving seven days after developing clinical signs. MCF is only very rarely non-fatal. If they do survive, they tend to fail to thrive or relapse.
• Babesiosis was confirmed on blood film examination in two Limousin heifers, that calved six weeks earlier and then developed haematuria, pyrexia and anaemia. Both had been bought in to a herd in North Wales from a non-tick infested lowland farm.
• Tick borne fever was diagnosed in a four-month-old suckler calf in Devon that was pyrexic, ataxic and tachypnoeic. Ticks were seen on the calf and Anaplasma phagocytophilum was detected by PCR in an EDTA blood sample. In a suckler herd in the Scottish Borders, a two-year-old heifer that had calved one month previously was pyrexic (40.2oC), depressed and had a stiff gait. The heifer was grazing a hill covered in ticks and seroconverted strongly to A. phagocytophilum on IFAT, suggesting that this was also a case of Tick Borne Fever.
• Brain was received for histopathology from the fourth 14-month-old fattening heifer to die acutely after developing signs suggestive of meningitis. This revealed a severe, acute, necrohemorrhagic and suppurative meningoencephalitis with vasculitis and intralesional bacterial emboli, typical of that seen with thrombotic meningoencephalitis associated with Histophilus somni infection. This is commonly seen in post-weaned cattle up to 18-months of age with animals presenting with sudden onset neurological signs, recumbency and depression prior to death.

Vasculitis and thromboembolism of a vessel in the brain of a fattening heifer with histophilosis

• One eight-month-old dairy heifer was found with a swelling over its back. It became recumbent, went into shock, and was therefore euthanased. PME detected black, emphysematous muscle over the lumbar spine and blackleg was confirmed with the detection of Clostridium chauvoei on IFAT of a muscle impressions smear. In a second animal, a 16-month-old Holstein-Friesian heifer that died acutely at grass, IFAT testing for C. chauvoei and C. septicum was negative but histopathology detected a necrohaemorrhagic myositis with emphysema and intralesional bacteria, consistent with clostridial myositis. ‘Pseudoblackleg’ can also be caused by Clostridium novyi type A, C. perfringens type A and C. sordellii.
• In one suckler herd, multiple suckler calves were becoming sick and depressed, and developing signs of pneumonia from four days old up to a few months of age. Calves were improving with antibiotics and NSAIDs but there were several poor doing calves. Two calves died suddenly and Salmonella Dublin was isolated from the spleen of one of the calves. S. Dublin septicaemia was also confirmed in an Aberdeen Angus calf on histopathology and tissue culture in a second herd.
• A large slow growing mass over the left shoulder of a four-year-old South Devon cow was determined to be a mass of dense collagenous tissue on histopathology containing a sparse to moderately cellular population of spindle shaped cells. This was consistent with low-grade spindle cell proliferation, potentially part of a fibroma or fibropapilloma.