Interesting cases in July

Cattle
Abortions and mastitis

• BVD virus was detected in foetal fluids of at least six abortion cases this month in the BVD antigen ELISA.
• Neospora caninum was detected by PCR in at least four abortions including one of which was also positive for BVD antigen in foetal fluids and another from which Aerococcus sp. was cultured from foetal stomach contents. Aerococcus sp. is a common environmental bacterium but can act as an opportunistic pathogen causing sporadic abortions in cattle.
• Coxiella burnetii (Q fever) was detected in placental tissue from at least three bovine abortions this month. In one of these cases the cow was reported to have aborted at seven months’ gestation and had retained placenta.
• Salmonella species were detected by PCR in two cases of abortion this month. In one case culture was not possible and in the other the serotype was confirmed as Salmonella Dublin following culture. Salmonella sp. was isolated in selective cultures from the foetal stomach contents of an abortion which was the third to occur in a
  250-cow autumn block calving dairy herd. The herd had previously vaccinated but had stopped around two years previously. The serotype in this case was also confirmed as Salmonella Dublin.
• Bacillus licheniformis was isolated from a five-month-gestation aborted bovine foetus. It was the third abortion to occur recently in the herd. All three aborted cows were well in themselves. Bacillus licheniformis is a known cause of abortion in cattle and may be associated with the ingestion of spoiled bedding or feed, or silage effluent.
• Escherichia coli was isolated in pure growth from the stomach content of aborted foetus of a pedigree Hereford cow. Histopathology of liver tissue identified a multifocal subacute hepatitis consistent with systemic bacterial infection.
• Trueperella pyogenes was isolated in two cases of abortion this month, one which was at five months’ gestation, the other at seven months.
• Evidence of placentitis with elements of vasculitis and a corresponding bronchopneumonia suggestive of an infectious cause of abortion, most likely bacterial, was seen on histopathology of tissues from a seven-month gestation aborted foetus.
• Of the less common pathogens isolated from milk samples this month, Pasteurella multocida was cultured from the milk of a three-year-old Holstein cow with episodes of mastitis recurring 5-10 days after a course of treatment producing very watery milk with large clots present. Nocardia sp. was also isolated from one sample.

Respiratory disease

• Coronavirus was detected by PCR testing on nasal swabs in at least six submissions this month. In one case bought-in housed calves of around three months of age were showing signs of pyrexia and mortality in greater than two percent of the batch of 160. In another case there was evidence of clinical pneumonia in a group of 20 Wagyu calves which ranged from three to 12 weeks old. Coronavirus may be detected in nasal swabs from healthy animals as well as those showing signs of respiratory disease. All of the submissions which were positive on PCR for bovine coronavirus were also positive for one or more of the bacterial pathogens; Mycoplasma bovis, Pasteurella multocida, Mannheimia haemolytica or Histophilus somni. The finding of M. bovis, H. somni, P. multocida and M. haemolytica from nasal/NP swabs are of uncertain significance as they can be carried in the URT of healthy cattle. However, a study by Doyle (2017) found there was very good correlation between nasal or NP swabs or BAL samples and trans-tracheal washes with regards to M. haemolytica, Pasteurella multocida and Mycoplasma bovis. (They did not include H.somni in their study). (Doyle et al (2017) Agreement Among 4 Sampling Methods to Identify Respiratory Pathogens in Dairy Calves with Acute Bovine Respiratory Disease. J Vet Intern Med. 2017 May; 31(3):954-959).
• PI3 and coronavirus were detected in one of three samples submitted from calves which were described as poor and scouring.
• RSV was detected by PCR testing in at least two submissions. One case involved first season grazing heifers. Coughing and serous nasal discharge were seen in a significant proportion of the group of 200. The second case was in a ten-week-old calf purchased from market which had fever and open mouth breathing and later died. Consolidation and congestion were observed throughout the lung tissue at PME.
• IBR was detected in a group of 12 to 16-month-old fattening bullocks in which six of the group of 20 had signs of pneumonia.
• A fibrinous bronchopneumonia with pleurisy with appearance consistent with a case of ‘shipping fever’, caused by Mannheimia haemolytica was identified as the likely cause of death of an adult Holstein cow on histopathology. PCR testing of lung tissue was positive for both M. haemolytica and Pasteurella multocida. M. haemolytica was detected by PCR testing in lung tissue in at least two further cases of respiratory disease in adult dairy cattle. One of these was reported to have extensive lung consolidation at PME.
• Pasteurella multocida, Mannheimia haemolytica and Histophilus somni were all detected by PCR in lung tissue from a Wagyu calf which was one of two to die from a recently purchased group of 40. A further 11 were affected with respiratory signs.
• There were at least two submissions in which active seroconversion to Mycoplasma bovis was identified on paired serology following a respiratory disease outbreak in calves.
• Bacterial bronchopneumonia consistent with descending infection with likely involvement of Pasteurellaceae was diagnosed by histopathology of lung tissue from a six-month-old dairy cross calf which was one of two to die in the group of 50 with a further four showing signs of weakness and scour.
• Bronchointerstitial pneumonia was diagnosed as the likely cause of death in a four-month-old Limousin bull calf. The animal was found off-colour but deteriorated and died only 15 minutes later. Histopathology of lung tissue
  identified marked subacute broncho-interstitial pneumonia with hyaline membrane formation and early type II pneumocyte hyperplasia. A wide range of insults can result in interstitial pneumonia with hyaline membrane formation /alveolar epithelialisation in cattle including mouldy feedstuffs, pneumotropic viral infections and possibly idiosyncratic responses to 3methylindole (fog-fever like).
• A one-day-old dairy heifer calf was euthanised on welfare grounds after showing signs of acute respiratory distress. Aspiration pneumonia was suspected to have occurred and this was supported by histopathology which identified severe inflammation and large amounts of protein rich fluid within the airways, consistent with milk/colostrum, likely administered inadvertently into the trachea by stomach tube.

• Postmortem tissues were received from an adult Brown Swiss cow which was in a group of milking cows kept outdoors. Three cows had died. Ten percent were reported to have severe respiratory disease and a further 20 percent were coughing. Half the cows in the group had milk drop. IBR and RSV had been previously identified on the farm and this group had recently received an IBR vaccine. On histopathology there was a moderate-marked, multifocal-coalescing, subacute, eosinophilic and suppurative bronchointerstitial pneumonia with bronchiolitis fibrosa obliterans, intralesional nematode larvae and interlobular emphysema. The overall appearance with the presence of migrating larvae suggested a diagnosis of lungworm though it was not possible to rule out concurrent/previous viral insult/ inhaled pneumotoxin and/or secondary bacterial invasion. Lungworm was diagnosed by PCR testing of faeces in three cases and by Baermann’s examination in at least a further two cases this month. One case was in a group of four-month-old cross Jersey calves which had received ivermectin two weeks previous to sampling. Seroconversion to lungworm was seen in two cross Hereford female cattle with pyrexia and respiratory stertor.

Gastrointestinal disease

• A total of 432 submissions for Johne’s disease serology and faecal PCR testing from cattle were received this month, with 132 submissions, including a total of 89 individual samples, testing positive. Blood and faecal samples were received from a cow which had a history of recent severe illness. It was the only animal in the group affected. Sudden weight loss and scour with haematochezia followed by dehydration and firm dung had been observed. Biochemistry revealed raised urea (43.7mmol/l: Reference interval 2.0-6.6mmol/l) and creatinine (448umol/l: Reference interval 40-170umol/l) indicating possible renal impairment. The animal tested strongly seropositive to Johne’s disease. Oak toxicity was considered a possible explanation for the azotaemia and acute signs of illness in this case. Johne’s disease was also diagnosed by serology in a two-year-old cow which had calved for the first time just five days previously but shown rapid loss in condition since. Another case was diagnosed on serology in a 12-month-old heifer, which was bought in four months previously and had been out at grass since, but was scouring and losing condition.
• Coccidiosis was suspected following high counts in faecal samples along with consistent clinical history in numerous submissions this month. One case was in an 18-month-old heifer which had suddenly lost weight and had bloody diarrhoea. There was a coccidial oocyst of 18,300opg. On another holding a four-month-old Aberdeen Angus cross was found dehydrated with profuse bloody scour and had a coccidial oocyst count of >50,000opg, strongly suspicious of coccidiosis, though speciation was not carried out in that case. In a further submission Eimeria species identification was carried out on a faecal sample from a calf with acute illness and suspected coccidiosis despite a low coccidial oocyst count in a faecal egg count performed at the practice. 86% of the coccidial oocysts present were of the pathogenic species Eimeria bovis. In cases of coccidiosis, disease can precede patency so coccidiosis cannot be ruled out even with oocyst counts of <1000 opg.
• Numerous cases of scour in calves due to Cryptosporidium were recorded. In two of these cases, hypogammaglobulinaemia was also identified indicating insufficient transfer of antibodies from colostrum. On one farm, calves which were reported to have inappetence and slight scour at 10-14 days of age tested positive for both Cryptosporidium and coronavirus on faecal sample testing. Diarrhoea caused by bovine coronavirus typically affects calves from three days to three weeks of age. Outbreaks may be similar or more severe than those caused by rotavirus. Affected calves will have liquid yellow diarrhoea which may contain mucus and blood. As with rotavirus infections, the clinical signs can be exacerbated by concurrent cryptosporidiosis.
• Death due to E. coli F5 (K99) enteritis was suspected in at least two cases in neonatal calves this month.
• There were at least six cases of disease associated with Salmonella Typhimurium, four of which were reported in freshly calved adult dairy cattle, one in young calves and there was one where no age was given. Salmonella Mbandaka was isolated from a four-year old, scouring, Holstein-Friesian cow on a farm where this serotype had been identified in the past. This serotype was also isolated from the faeces of a recently calved pyrexic dairy cow. Salmonella Dublin was isolated from two cases of scouring calves and another case where the age of animals was not stated. 
• Yersinia enterocolitica and Yersinia pseudotuberculosis were isolated in faecal cultures from three to four-month-old calves which had been outdoors for one month and had watery/bloody diarrhoea and were rapidly losing condition. In-house coccidial oocyst counts had been very low. Subclinical carriage of Yersinia species is very common in young healthy ruminants. However, yersiniosis due to Yersinia pseudotuberculosis is a recognised cause of diarrhoea in calves often around four to ten months in age resulting in marked enteritis and formation of microabscesses within the intestinal mucosa. Conditions which may precipitate an overgrowth in the gut are trace element deficiency, parasitism, BVD infection, long transportation and malnutrition.
• Raised pepsinogen indicating abomasal parasitism was recorded in numerous submissions this month. One case was a two-year-old Aberdeen Angus heifer which had deteriorated following calving and had a brown staring coat. The pepsinogen level was high at 5.79iu/l (RI <1.5iu/L). A poor doing diarrhoeic Holstein-Friesian heifer had a very high pepsinogen level of 7.25iu/L and was hypoalbuminaemic. Ostertagiosis was considered the likely cause of illness.

Skin and eye disease

• Punch biopsies from masses on the skin of the flank of a Blonde d’Aquitaine cow were received for histopathology. The samples all comprised areas of ulcerated granulation tissue with prominent fibroblast proliferation, perivascular infiltrates of plasma cells and lymphocytes and multifocally accumulations of neutrophils surrounding collections of eosinophilic Splendore-Hoeppli material and accompanying epithelioid macrophages. The appearance was considered consistent with cutaneous bacterial infection with granulation, likely cutaneous actinobacillosis. This was further supported by gram staining which identified indistinct gram-negative rods associated with the centre of club colonies.
• Histopathology of a biopsy from a mass on the penis of a 14-month-old Limousin bull identified the growth as a fibropapilloma. Fibropapillomas are hyperplastic lesions caused by papillomavirus infection. Penile fibropapillomas in bulls are most often diagnosed at 1-2 years of age. They can spontaneously resolve, but this occurs after a variable time period and recurrence can often be a problem. Rare cases can be persistent.
• Moraxella bovoculi was isolated from two of four swabs submitted from a group of cattle in which an outbreak of conjunctivitis was spreading and which was poorly responsive to treatment.

Systemic and miscellaneous disease

• A total of 378 submissions were received for BVD antigen testing in cattle in July, with 37 submissions, including a total of 50 individual samples, testing positive.
• On one farm a seven-week-old calf with neurological signs was suspected to be a PI and was found to be BVD viraemic. The vet reported that there was no BVD control measures in place on the farm. On another farm a ‘bulldog’ calf tested positive for BVD virus in the antigen ELISA. On another holding a calf which was a suspected PI and had an irregular heart rhythm was confirmed as BVD viraemic in the antigen ELISA. A 10-month-old Belgian blue cross bullock which died after an acute illness tested positive for BVD virus by PCR on bloods with a low Ct value suggesting that the animal was likely to be a PI and the cause of death was suspected to be mucosal disease.
• Antibodies to Border disease were detected in a bovine animal by SNT antibody testing to differentiate Border disease antibody from BVD antibody. The animal had repeatedly tested as suspect in the youngstock BVD antibody check test despite there being no evidence of a BVD breakdown in the herd. There were sheep present on the farm, but Border disease had not been previously identified in the flock.
• Blood parasites consistent with Babesia spp. were seen on blood films from a cow in Devon with severe anaemia (PCV 12%) and jaundice. Biochemistry showed evidence of azotaemia most likely due to dehydration. The animal also had a high antibody titre to Anaplasma phagocytophilum (Tick borne fever) indicating recent exposure to this pathogen. Liver samples from a second cow from the same farm which had died showed peri-acinar hepatocellular necrosis and fatty change likely to be related to hypoxaemia associated with anaemia. On a farm in Cornwall, babesiosis was suspected and blood samples were submitted from the second cow to show clinical signs. Babesia sp. was detected by PCR in that case.
• A 12-month-old bullock was found dead. The neck muscles were found to be oedematous, puffy and ‘crackly’ at PME. Acute necrotising and haemorrhagic myositis was identified on histopathology in the affected skeletal muscle and also in cardiac muscle. Gram-stained sections showed isolated slender gram-positive rod-shaped bacteria seen in association with areas of necrosis and haemorrhage consistent with a diagnosis of clostridial myositis (blackleg).
• Two housed finishing heifers which died suddenly were found to have emphysematous lesions in the neck and shoulder muscles at PME. FAT testing of affected tissues from both animals was positive for Clostridium chauvoei and Clostridium septicum indicating evidence of both blackleg and pseudoblackleg in this case.
• Two spring born dairy calves from a group of 300 were found dead. The herd had a history of deaths due to Histophilus somni and so the group had received an H. somni vaccine in March, though there was concern that immunological cover from this dose could now be waning. PME identified lesions suspicious of areas of necrosis in the heart but no significant findings in other major organ systems. Bacterial cultures of heart and lung tissue proved negative for significant pathogens, though Histophilus species are known to be fragile and may not survive long post-mortem. PCR testing was recommended and Histophilus somni was detected in heart muscle indicating this was the likely cause of the lesions and death in this case.
• Nine cases of Malignant Catarrhal Fever were diagnosed by PCR testing. A PME was carried out on one of the cases and microscopic lesions consistent with MCF were seen (moderate, subacute, peri-portal lymphocytic and necrotising hepatitis with fibrinonecrotising vasculitis and mild to moderate peri-arteriolar lymphoid hyperplasia of the spleen).
• Three male Aberdeen Angus cross cattle died with signs of uroabdomen and crystals around the preputial hairs following an issue with water availability which had occurred some weeks previously. Microscopy identified the crystals as struvite/ triple phosphate. Histopathology of kidney tissue identified severe chronic pyelonephritis with papillary necrosis. Water deprivation and reduced urinary flow resulting in ascending bacterial infection was considered to be the likely underlying pathogenesis in this case.
• Severe fibrinous pleuritis and pericarditis with haemorrhage and acute interstitial pneumonia appeared to be the cause of death in a one-month-old Holstein-Friesian calf. The calf had been treated sporadically for pneumonia signs throughout its lifetime. Failure of transfer of passive immunity was suspected. Severe and locally extensive pleurisy with adhesions and haemorrhage were obvious at PME. On histopathology, the findings reflected acute fibrinous polyserositis with interstitial changes in the lung supporting a systemic inflammatory process/septicaemia. No evidence of primary bronchopneumonia was identified in this case.