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BOVINEApproximately 174 bovine carcasses were submitted to the RVLs in September 2017. Similar to previous months, the respiratory (32.7%) and gastrointestinal (32.1%) tracts were the most commonly affected organ systems.

Table 1: Ten of the most common diagnoses in September 2017.

RESPIRATORY TRACTCALF DIPHTHERIA

A four-month-old weanling was presented to Kilkenny RVL

with a history of poor thrive and poor appetite. Grossly, there was a chronic bronchopneumonia with adhesions affecting approximately 20% of the lungs. Moreover, there were approximately 2cm-diameter ulcers with thick surface exudate affecting the mucosal surface of the cranial larynx (see Figure 1). There was no gross evidence of extension of the process into the underlying arytenoid cartilages. Histopathology of the larynx revealed focally extensive, full-thickness ulceration and severe coagulative necrosis of the submucosa with exudation of fibrin, neutrophils and macrophages. The necrotic area contained numerous colonies of filamentous bacteria. The diagnosis of necrosuppurative laryngitis with intralesional bacteria was reached, and although the causative pathogen was not identified, Fusobacterium necrophorum is likely to have been involved. It is likely that calf diphtheria extended into the larynx and oesophagus and contributed to the inappetence and chronic ill-thrift.

PNEUMONIA IN CALVESTwo five-month-old calves were presented to Kilkenny RVL for post-mortem examination. There had been a history of respiratory disease with mortality in cohort animals, which were purchased Friesian calves. Both carcasses were in very poor body condition. Nearly 100% of the left and right lungs of both calves were pneumonic with extensive consolidation most pronounced cranially. In addition, one of the calves had extensive severe multifocal to coalescing areas of abscessation and multiple fibrous pleural adhesions. There was also a fibrous pericarditis (see Figure 2). There was no adipose cover over the internal organs. Pasteurella multocida and Trueperella pyogenes were cultured from the lung tissue. Moreover, Mycoplasma bovis, Haemophilus somnus and parainfluenza 3 virus (PI3) were detected by polymerase chain reaction (PCR). The range of isolates from these cases of chronic pneumonia illustrates the need to prevent and manage multifactorial respiratory disease by ensuring the calf receives adequate colostrum (amount and quality) to achieve good immunity and by controlling the environment in relation to biosecurity, hygiene (including the atmosphere) and stocking density to reduce pathogen challenge.

Figure 2: Chronic suppurative pneumonia showing multiple adhesions, consolidation and abscessation. Photo: Maresa Sheehan.

PARASITIC BRONCHITISA four-month-old calf was submitted to Limerick RVL with a history of respiratory signs which rapidly deteriorated. Eight further calves died with similar symptoms over a two-week period. Necropsy revealed bilateral consolidation of the cranioventral lobes of the lungs with dark-purple discolouration. The remaining lungs were heavy and fluid-filled. There was noticeable emphysema (‘ground-glass’ appearance evident in pleurae) present with numerous Dictyocaulus vivparus adults in the airways. There was marked tracheitis present, characterised by congestion and oedema of the tracheal mucosa. A moderate trichostrongyle burden was detected in the intestinal contents. Histopathology of the lungs disclosed widespread areas of atelectasis with congestion within the alveolar walls, many of which contained neutrophil and eosinophil-rich proteinaceous exudate. Parasitic bronchitis with likely secondary bacterial bronchopneumonia was diagnosed as the cause of death.

GASTROINTESTINAL TRACTTRAUMATIC RETICULOPERITONITIS (HARDWARE DISEASE)

Limerick RVL examined a three-year-old lactating Friesian cow which had presented with diarrhoea and a noticeable milk drop. The animal deteriorated despite treatment and died within two days. The cow originated from a 115-animal dairy herd at pasture. On necropsy, an abscess was detected which was attached to the liver and reticulum and associated with a 4.5cm sharp wire. There were localised areas of fibrinous peritonitis on the liver. The wire had more than likely passed through the reticular wall, though the mucosa of the reticulum looked normal. The abscess had extended into the hepatic parenchyma and there were localised lesions of peritonitis. Bacterial culture was unrewarding. No lesions of pericarditis were seen in this case but are a very common feature in cases of hardware disease.

TRAUMATIC PHARYNGITIS (DOSING GUN INJURY)Dosing-gun injuries are most commonly seen in sheep, but

a case with a fatal outcome was diagnosed in a nine-month-old bovine weanling by Cork RVL. The animal was observed by the farmer with a swollen head and protruding tongue, and died quickly without receiving any veterinary treatment. Blackleg was firstly suspected by the farmer but gross examination displayed extensive malodorous subcutaneous swelling (cellulitis) affecting the neck and head. Deep dissection of the affected area also revealed severe-tissue necrosis involving the pharyngeal region and the surrounded soft tissue. T pyogenes was isolated from routine cultures. Lesions resulting from a dosing gun injury can potentially progress to asphyxiation, continuous blood loss or septicaemia, as in this case. Though unusual in cattle, this case highlights the potential risk of injury to cattle when drenching technique or equipment is suboptimal.

SALMONELLOSISA three-week-old calf was submitted to Sligo RVL, having being found dead without any prior signs of illness. The carcass appeared very dehydrated and presented with diffuse-acute ulcerative, necrohaemorrhagic, oedematous abomasitis. There was an accompanying fibrinous peritonitis. Salmonella and Pasteurella spp were isolated from the lesions. The Salmonella isolate was typed as Group D (Salmonella Dublin is in this group). Further serotyping was not possible in this case as no H-antigen was detected. In some serotypes, their expression varies or may even be absent.

Salmonella is a gram-negative bacteria belonging to the family of enterobacteriacae. The Salmonella isolates we deal with may be either full species or species-linked serovars of Salmonella enterica, eg. Salmonella enterica serovar Typhi (S Typhi) and S Paratyphi are common in humans; S Gallinarum causes disease in poultry, S Dublin in cattle. The lack of italics and capital in the second part of the isolate’s name indicates it is a serovar, not a species (S enterica being the species in each case for these serovars).Salmonella has a serovar-host specifity, meaning each serovar has a narrow range of host species. Accordingly, some of the Salmonella isolates are full species, eg. S abortus ovis in sheep, and S choleraesuis in pigs. Serotyping is of the greatest importance in Salmonella outbreaks to trace the likely source and to gauge the zoonotic risk of the involved serotype. Salmonella serotyping involves detection of the expressed O-antigen (on the surface of the bacterial-cell wall) and H-antigen (flagellar protein). According to these unique proteins, Salmonella serotypes and species are divided into groups. In general, young individuals develop enteritis or a septicaemic form, whereas adults are affected by enteritis and/or abortions. Salmonella is known to cause ‘abortion storms’ when outbreaks occur in cattle. The dams usually appear clinically sick and produce emphysematous and autolysed foetuses. Diagnosis is reached by culture of foetal abomasal

Regional veterinary laboratories (RVLs) carried out necropsy examinations on 388 carcasses and 73 foetuses during September 2017. Additionally, 2,368 diagnostic samples were tested to assist private veterinary practitioners (PVPs) with the diagnosis and control of disease in food-producing animals. This report describes a selection of cases investigated by the Department of Agriculture, Food and the Marine’s (DAFM) regional veterinary laboratories in September 2017. The RVLs are

located in Athlone, Cork, Kilkenny Limerick, Sligo and Dublin and provide a network of specialist knowledge and diagnostic capabilities to maintain animal-disease surveillance, with the objective of protecting and improving the health of Irish livestock and the international status of related industries. This report aims to inform and assist PVPs engaged in the diagnosis of common and uncommon diseases in livestock in Ireland.

REGIONAL VETERINARY LABORATORIES REPORT SEPTEMBER 2017

Pneumonia

Parasitic gastroenteritis

Blackleg

Enteritis

Parasitic bronchitis

Bacteraemia/septicaemia

Abomasal ulcer/perf peritonitis

Autolysis

Intestinal torsion

Mesenteric torsion 3

3

3

4

6

8

12

12

19

44

Figure 1: Ulceration and coagulative necrosis of the larynx likely to be associated with Fusobacterium necrophorum. Photo: Maresa Sheehan.

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that foetal malformations may occur at calving next spring. There are indications based on clinical evidence and ELISA results that Schmallenberg virus has been active in the summer/autumn just past.

ABORTIONBacillus licheniformis and Staphylococcus aureus were isolated from abortions in Limerick RVL during September; however the majority of foetal submissions did not result in the culture of significant pathogens.

CARDIOVASCULAR SYSTEMBABESIOSIS (REDWATER)

A four-year-old Friesian cow was submitted for post-mortem examination to Limerick RVL. The herd presented with high temperatures and a drop in milk yield a few weeks previously; tick-borne fever was suspected, the animals responded to treatment and had been moved to fresh pasture since. In the few days prior to submission, some cows appeared sick again and the submitted animal passed red urine and died. On post-mortem examination the carcass appeared pale and jaundiced with an enlarged spleen. Ecchymotic haemorrhages were observed on the epicardium and endocardium. Kidneys were dark and the urine in the bladder was port wine in colour. The gross findings and history were highly suggestive of a diagnosis of babesiosis in this case. Subsequent blood sampling of three cows (two sick and one healthy) lead to the discovery of inclusions (piroplasms) in the red blood cells of one cow, consistent with babesiosis.

Figure 6: Babesia-infected erythrocytes in a blood smear stained with Differential Quik from a deceased animal. Photo: Colm Ó Muireagáin.

MUSCULOSKELETALCLOSTRIDIAL INFECTIONS

A five-month-old suckler calf was submitted to Athlone RVL. The calf was depressed when found and reluctant to stand. He died about an hour later. At post-mortem examination the muscles of the right shoulder girdle were very dark with a dry consistency. There were also fibrin strands in the pericardial sac. Clostridium novyi was cultured from muscle, heart and lung. A diagnosis of clostridial myositis due to C novyi was given.

There were several cases of blackleg submitted to the RVLs in September 2017. In one case, a six-month-old calf with history of rapid onset dullness, anorexia and death was submitted to Limerick RVL. Post-mortem examination disclosed a necrotic lesion in the subcutaneous muscle of the abdomen, confirmed as blackleg by positive fluorescent antibody test (FAT) for Clostridium chauvoei. Fibrinous pleuropneumonia and pericarditis, and severely inflamed intestinal mucosa with liquid small intestinal contents, were also observed. Histopathology disclosed enteritis with helminths visible in cross section in the mucosa; pulmonary congestion and moderate interstitial pneumonia. Multiple disease processes have been diagnosed in this animal; despite the unusual location of the lesion, blackleg was deemed the most likely cause of death. In another case, three out of six weanlings, which had died within a short period, were submitted to Cork RVL. They had appeared lethargic and became recumbent before dying within a few hours. The animals were from the same herd but housed in two different locations at the time of disease onset. The carcasses were in good body condition and gross examination revealed dark, red-black areas of haemorrhagic necrosis, oedema and crepitus in the neck and gluteus muscles (haemorrhagic necrotising myositis; see Figures 7 and 8), and also fibrinous pericarditis, lesions characteristic of clostridial myositis (blackleg). C chauvoei was confirmed later by isolation in anaerobic culture and FAT visualisation in the impression smears of the muscles. These animals were indoors, however, and clostridial spores can lie dormant in the muscle. Accidental muscular trauma in a crowded feedlot can result in localised tissue hypoxia in damaged tissue and the ideal anaerobic conditions that facilitate the proliferation of the bacteria and the development of blackleg.

Figure 7: Photograph demonstrating necrotising myositis in the biceps femoris of a weanling as a result of C chauvoei (blackleg). Photo: Cosme Sánchez-Miguel.

contents, uterine fluids or the dam’s faeces. The clinically normal carrier animal is a serious problem in all host species. Drain swabs or milk filters can be used to establish the Salmonella status of a herd. Salmonella vaccines are available for cattle. Salmonella poses an important zoonotic risk and a serious public health concern. In the Republic of Ireland cases of salmonellosis caused by or involving Salmonella enteriditis or Salmonella typhimurium are notifiable.

PARASITIC GASTROENTERITISLimerick RVL received a higher number of cases of parasitic gastro-enteritis in September compared to other months. A four-month-old calf was submitted to Limerick RVL with a history of weight loss. On necropsy, the intestinal contents were watery, the abomasal lining appeared thickened and reddened with some degree of nodular hyperplasia around the glands (see Figure 3). A high trichostrongyle egg count was detected, as well as a Nematodirus burden. Parasitic gastroenteritis was suspected.

Figure 3: ‘Moroccan-leather’ appearance of the abomasal mucosa in a cases of parasitic gastroenteritis. Photo: Colm Ó Muireagáin.

ABOMASAL ULCERATIONLimerick RVL examined a bullock which was found dying without having shown any signs of illness previously. The carcass appeared anaemic and jaundiced at necropsy. There were multiple ulcers in the abomasal mucosa, some with evidence of haemorrhage. The abomasal and intestinal contents were reddish, suggesting chronic haemorrhage from one or more abomasal ulcers over a long period of time. Histopathology of the liver found an acute, severe periacinar degeneration and necrosis. Bile ducts were multifocally ectatic and multifocally lined by attenuated epithelium and were filled with degenerate neutrophils and bile; multifocally, there was biliary hyperplasia within portal triads. The morphological diagnosis was acute periacinar necrosis (consistent with anaemia due to haemorrhaging abomasal ulcers) and acute suppurative cholangitis. It was most likely due to an ascending opportunistic bacterial infection. The cause of death was considered to be related to the abomasal ulceration and haemorrhage.

URINARY/REPRODUCTIVE TRACTPYELONEPHRITIS

A three-and-a-half-year-old cow with little clinical history was submitted to Kilkenny RVL. On necropsy, the kidneys were bilaterally extremely enlarged with petechial to ecchymotic haemorrhages throughout. On incision the pelvic areas of both kidneys were dilated and filled with copious amounts of pus (see Figure 4); the ureters were similarly filled with purulent material. These gross findings are consistent with chronic, severe pyelonephritis. The bladder mucosa was hyperaemic. On histopathological examination, there was severe diffuse chronic lymphohistiocytic tubulointerstitial nephritis with fibrosis and tubular casts which was consistent with chronic pyelonephritis. Within the bladder there was diffuse mucosal erosion and ulceration with marked diffuse lymphoplasmacytic and histiocytic submucosal infiltration, often forming lymphoid follicles (chronic active cystitis). Pyelonephritis usually results from ascending infection from the lower urinary tract. Corynebacterium renale was isolated – the role of this bacteria in bovine pyelonephritis is well established. Aqueous humour magnesium concentrations of 5.2mmol/L were detected, these are below the normal range. A diagnosis of severe bilateral pyelonephritis and cystitis with concurrent hypomagnesaemia was reached; the lack of clinical signs is consistent with hypomagnesaemia (grass tetany). The pyelonephritis may have predisposed to inappetence and increased the risk of grass tetany.

Figure 4: Severe, chronic suppurative pyelonephritis in a cow, from which Corynebacterium renale was isolated. Photo: Maresa Sheehan.

SCHMALLENBERG VIRUSA dairy herd which had milk drop, pyrexia and severely reduced fertility was investigated by Athlone RVL. The milk drop and raised temperatures had been occurring for a number of weeks. Cows showed depression, and there was a drop in their milk yield for four or five days before returning to normal without any treatment. Schmallenberg virus infection was suspected and confirmed by positive ELISA assay results in serum taken from affected cows. The farmer estimated that 25% of his cows previously confirmed as pregnant by scan had lost their calves. It is anticipated

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Figure 9: Bolus encapsulated in necrotic-purulent tissue, embedded in pharyngeal soft tissue Photo: Colm Ó Muireagáin.

LARYNGEAL CHONDRITISA 10-month-old purebred Beltex ram was submitted to Athlone RVL for post-mortem examination. The ram was bought three weeks previously and was found dead, having shown no signs of illness when seen the day before. On post-mortem examination, the left side of the larynx was swollen (see Figure 10) and oedematous. Incision of the laryngeal cartilage revealed an abscess which cultured positive for Enterococcus faecalis. No other findings of note were observed. A diagnosis of laryngeal chondritis was given (see Figure 11).

Figure 10: Larynx of a 10-month-old Beltex sheep, left arytenoid cartilage significantly swollen (arrow). Photo: Séamus Fagan.

Figure 11: Abscess apparent on opening of arytenoid cartilage. Photo: Séamus Fagan.

OVINE PULMONARY ADENOCARCINOMA (JAAGSIEKTE)

Sligo diagnosed ovine pulmonary adenocarcinoma (jaagsiekte) in an eight-month-old pedigree Texel ram with a history of chronic respiratory signs and chronic rhinorrhoea especially when the head was lowered (wheelbarrow test). At post-mortem examination the lungs

were bilaterally indurated and grey with a rubbery texture. The disease was confirmed on histopathology and RNA specific to jaagsiekte sheep retrovirus was detected by PCR technique.

URINARY/REPRODUCTIVE TRACTSligo RVL received a five-year-old horned ewe which had been found dead. On post-mortem examination a severe peritonitis and a ruptured uterus with exuding purulent material were apparent. T pyogenes was isolated from the purulent material.

Figure 12: Purulent peritonitis caused by ruptured uterus. Photo: Colm Ó Muireagáin.

OTHER SPECIESLAGOMORPHSFour hares submitted for necropsy in Limerick RVL had soft intestinal contents and inflamed intestinal mucosa. Histopathology of all four hares disclosed severe enteritis. Coccidia were detected in the intestines of one hare and were suspected of involvement in the others. Histopathology of the liver of one hare disclosed a severe multifocal, random hepatitis, similar to paratyphoid nodules. These are most likely due to a septicaemia involving gram-negative bacteria; this may be a sequel to enteritis, although salmonellosis cannot be ruled out.

EQUIDSIn rare and exceptional cases, DAFM’s regional veterinary laboratories can take in equids for post-mortem examination.A seven-year-old thoroughbred mare was submitted to Sligo RVL after collapsing during hacking and showing nervous signs of thrashing and head banging. The animal had to be sedated to control the ‘fitting’ and died shortly after. It was reported that the animal had a fall the week previously with some mild abrasions on the head and had shown no further symptoms since. On necropsy, a severe haemorrhage over the right hemisphere of the cerebrum was discovered. On histopathology, there were multifocally-variably sized areas of perivascular and meningeal haemorrhages and rarefaction of adjacent neuropil indicating recent haemorrhage. Multifocallly, there were infiltrates of moderate numbers of gitter cells. A cerebral haemorrhage and subsequent neurological damage, possibly caused by a previous reported accident, were considered the most likely cause of death.

Figure 8: Photograph demonstrating necrotising myositis in the skeletal muscle of a weanling as a result of C chauvoei (blackleg). Photo: Cosme Sánchez-Miguel.

OVINEThe gastrointestinal tract was the most commonly affected organ system in the month of September in sheep.

Parasitic gastroenteritis

Intestinal strangulation

Haemorrhagic enteritis

Enteritis-haemorrhagic 7.7%

7.7%

7.7%

76.9%

Table 2: Most common diagnosis in the ovine gastrointestinal tract in September 2017.

GASTROINTESTINAL TRACTPARASITIC GASTROENTERITIS

Two lambs approximately six months old were submitted to Athlone RVL from a flock with 150 ewes. Both lambs were in moderate body condition and had perineal faecal staining. The intestinal contents were excessively fluid. In one lamb there was evidence of parasitic tracts in the liver and some adult worms were found in the small intestines of the other. The lambs had been dosed a couple of days previously. Faecal egg counts showed moderate levels of trichostrongyle eggs. No liver or rumen fluke eggs were present. Liver cobalt levels in both lambs were low. A diagnosis of parasitic gastroenteritis, with subacute fasciolosis was given and further investigation of flock for anthelmintic resistance and cobalt status advised.

Anthelmintic resistance is a dynamic process, despite not being reversible. The ability to detect resistance depends on the species present, the season and also the specificity and sensitivity of the employed test. Therefore, it is recommended to repeat tests as part of ongoing health monitoring in a herd health plan. For cases in which anthelmintic resistance is suspected a number of tests are available differing in complexity, robustness and also cost. One of the easiest tests is the ’drench test’, in which a small part of the flock is divided in three groups, each drenched with a wormer from a different worming group. Seven days after treatment with group 2 wormer (levamisole), 10-14 days after treatment with group 1 (benzimidazoles) or 14-16 days for group 3 (macrocyclic lactones), faecal samples are collected and examined. This test can give an indication of anthelmintic efficacy.

Robustness and results of this method can be improved by using the more structured faecal egg count reduction tests (FECRT). A representative group of sheep is divided into groups of which, one serves as control, and the others are drenched, each with a wormer from the groups to be tested. Faecal samples are taken from all animals on day 0 (= pre-treatment) to establish a baseline. Similar to the simple drench test, seven days after treatment, faecal samples are collected from the animals drenched with the group 2 wormer and from the control group. Faecal samples are collated 14 days after treatment form the groups drenched with group 1 or group 3 as well as the control group again. In cases of a reduction of less than 95% we can suspect anthelmintic resistance. In vitro tests have also been developed to test for resistance to benzimidazoles (egg-hatch assays, larval development test) and levamisole (larval development test). These can help to identify resistance while the expression of resistance alleles is still low.

COPPER TOXICITYSligo diagnosed copper toxicity in an 18-month-old Texel ewe with a history of dullness, pyrexia and colic. At post-mortem examination, the only significant findings were icterus and gun-metal-coloured kidneys. Toxic concentrations of copper were detected in the kidneys by biochemistry and liver values were well above the normal range for sheep.

Although acute copper poisoning in sheep is possible, the majority of cases seen in the laboratories are really chronic copper toxicity with an acute presentation. The Texel, Charolais and Suffolk breeds seem to be more susceptible than others. The ovine liver is very effective at storing copper and sheep can survive for up to half a year on copper deficient diets using their hepatic reserves alone. However, there is a limit to this storage capacity. Further copper intake, once the threshold is reached, results in red-cell haemolysis and a haemolytic crisis. Copper release into the bloodstream can also be precipitated by any kind of stress, or the ingestion of plants containing hepatotoxins. Most cases seen have a history of concentrate intake and sheep of these breeds on prolonged intakes can easily become susceptible to toxicity even when the concentrates contain ‘normal’ dietary levels of copper.

RESPIRATORY TRACTTRAUMATIC PHARYNGITIS (DOSING GUN INJURIES)

Sligo is starting to see a pattern of drenching-gun injuries where boluses are pushed through the back wall of the pharynx and left in the soft tissues. Abscessation and haemorrhage are common and death is due to secondary starvation or dehydration (see Figure 9).