SAC C VS Monthly Report for March 2015

Transcription

1 SAC C VS Monthly Report for March 2015 OVERVIEW Skin lesions in a heifer with malignant catarrhal fever Unusual neurological condition in Charolais calves Pregnancy toxaemia in ewes Erysipelothrix rhusiopathiae endocarditis in sows Gastric ulceration in a Huacaya alpaca GENERAL INTRODUCTION March began cold, very windy and unsettled with snow across high ground. A succession of active depressions brought rain and strong winds, but the weather settled down by the middle of the month and it was milder with sunshine at times. The mean temperature for the month was 0.2 C above the 1981 to 2010 average. Rainfall overall was 122 per cent of average and sunshine amounts were 119 per cent of average overall. DISEASE ALERTS The following conditions were reported by SAC C VS disease surveillance centres in July Given similar climatic and production conditions, they could also be important this year. CATTLE Babesiosis in cattle Delayed swayback in lambs Teladorsagiosis in lambs Border disease in lambs Spironucleosis (hexamitiasis) in pheasants Generalised and systemic conditions SAC C VS considered that hypogammaglobulinaemia again contributed to neonatal calf mortality across Scotland. Ayr advised a review of calf husbandry on a dairy farm that experienced high mortality in neonatal calves, with six calf deaths from a group of 24 in a one month period. At postmortem examination a five-day-old Holstein heifer calf was not dehydrated, but yellow diarrhoea was evident along with navel and joint ill. Cryptosporidial oocysts were detected on intestinal smears. Zinc sulphate turbidity (ZST) testing indicated an absolute failure of colostrum absorption with a value of 2 units (greater than 19 indicates adequate colostrum absorption). Serum samples from a further five calves, aged less than one week, had ZST values ranging from 2 to 16 units, consistent with failure of colostrum absorption. Dumfries diagnosed concurrent hypogammaglobulinaemia and colisepticaemia in two, two-day-old calves from different farms. One calf was the fourth to die with similar clinical history. Both affected calves were lethargic prior to death and one had diarrhoea. In both cases the ZST value was 1 unit. At postmortem examination one calf had brick red mucous membranes, splenomegaly and diarrhoea, while the other showed no significant findings. A pure and systemic growth of Escherichia coli was detected in both cases. Aberdeen investigated an unusual disease outbreak in a 180 cow spring-calving, organic suckler herd. Calves from a group of heifers that calved before the main cow group presented at four to seven days of age with ataxia, lethargy and increased thirst (constantly drinking from water troughs). The first four calves born were affected. They all slowly recovered from ataxia, though remained with an increased thirst. Initial clinical findings indicated pallor, low PCVs and very dilute urine but no consistent biochemical abnormalities. As cows started calving it was noted that almost all of their calves were lethargic and had increased thirst, though no more ataxia was observed. Subsequent investigation indicated that adult cows and older calves housed in the same shed also had abnormally dilute urine, but again no marked or consistent haematological or biochemical abnormalities. Dietary assessment of the cows diet indicated multiple macro- and micro-mineral deficits including phosphorous, magnesium, copper, manganese, zinc, cobalt, iodine and selenium. Ad lib salt blocks were available and average salt intake in the adult herd was estimated at two to three times recommended requirements. Despite extensive investigation a definitive explanation for clinical signs in the calves however was not determined. Ayr diagnosed malignant catarrhal fever (MCF) in a homebred, one-year-old Belgian blue-cross heifer that presented clinically with severe dermatitis and weight loss. The animal also had lymphomegaly and oral ulceration and was only one affected from a group of 25, one of which was bought in. There was an initial, temporary improvement to treatment with non-steroidal anti-inflammatories and antibiotics. At postmortem examination extensive exudative skin lesions were present; these were particularly prominent in the axilla, inguinal region and udder (Fig 1). All carcase lymph nodes were enlarged (Fig 2) and ulceration of the gingiva (Fig 3), tongue and oesophagus was evident. There were focal areas of consolidation in the lungs and the surface of the spleen appeared mottled. No lice or mites were detected on microscopy of skin scrapings. Bibersteinia trehalosi was recovered from lung lesions, but no significant bacteria were recovered from skin lesions. On histopathological examination a massive necrosis of the epidermis, upper and mid dermis of the skin was evident with a marked perivascular infiltrate in the deep dermis dominated by neutrophils and lymphocytes. A mild 1

2 lymphocytic infiltrate was present in the kidney and in the heart tracts of fibrosis were present centred on blood vessels and containing lymphocytes, plasma cells and very occasional polymorphs. BVDV (bovine viral diarrhoea virus) 1, BVDV2 and border disease virus RNA were not detected by real time RT-PCR, but ovine herpes virus 2 (OvHV-2) DNA was detected confirming a diagnosis of malignant catarrhal fever to be. St. Boswells also diagnosed MCF in a shorthorn cow that had more classic clinical signs of lethargy, pyrexia and corneal oedema. Fig 1 fever Exudative skin lesions in malignant catarrhal Fig 3 Ulceration of the gingiva in malignant catarrhal fever Dumfries diagnosed salmonellosis as the cause of death in a 12-year-old cow, the third to die within five days of calving. Affected animals had very little milk at calving, developed diarrhoea and lost weight rapidly before death. One of their calves was stillborn, while the other two calves were lethargic at birth. At postmortem examination there was evidence of dehydration, the liver was orange in colour, the spleen enlarged and a severe haemorrhagic, fibrinous typhlocolitis was present. Salmonella Typhimurium PT 104 was recovered in systemic distribution. Reproductive tract conditions BVDV was detected in either foetal fluid or tissue from aborted foetuses from two farms. As the national eradication programme progresses, examination of aborted or stillborn foetuses will become an increasingly important for BVDV surveillance. Fig 2 Enlarged prescapular lymph node in malignant catarrhal fever Edinburgh diagnosed abortions due to Neospora caninum at different stages of gestation in a 150-cow dairy herd. The submitted foetuses were estimated at five, six and eight months gestation. Nine abortions had occurred over a period of eight days and three foetuses were submitted for postmortem examination. Histological examination of the brain and heart revealed changes highly suggestive of neosporosis in all three foetuses and this was confirmed by PCR testing in two cases. No other abortifacient agents were identified. Nervous system disorders In the September 2014 surveillance report SAC C VS described suspected cases of progressive Charolais ataxia. Three spring-born calves, from a group of 14 pure-bred Charolais cows with calves at foot, were affected. Neurological signs included a wide base stance, mild stiffness, muscular twitching, an exaggerated 2

3 stepping gait and ataxia of the fore and hind limbs. The affected calves were sired by one bull, while the remaining unaffected calves in the group were conceived through artificial insemination. The first affected calf was euthanased following rapid deterioration, but further examination was not possible. In December 2014 another of the affected calves was euthanased and histological examination of the cerebellum revealed degenerative changes, with a loss of Purkinje cells and an increased number of glial cells. These findings were not consistent with progressive Charolais ataxia. There was no evidence of a transmissible spongiform encephalopathy on immunohistochemistry. Other differentials considered included cerebellar cortical atrophy (Cho and Leipold, 1978), which is also thought to be hereditary in origin. The possibility of mercury poisoning is also being investigated. Interestingly the third affected animal, which was the least severely affected, made a full clinical recovery. SMALL RUMINANTS Nutritional and metabolic disorders Pregnancy toxaemia was diagnosed on 12 occasions during March. Aberdeen diagnosed the condition in a three-year-old mule ewe in late gestation that showed intermittent neurological signs including tremor and facial twitching. The serum beta-hydroxybutyrate result was 7.5 mmol/l (reference range less than 1 mmol/l). Dietary energy sufficiency can be checked by blood sampling twin and triplet bearing ewes four weeks pre-lambing. Toxic conditions Ayr diagnosed Pieris species poisoning in sheep from three different flocks. All cases were accompanied by a history of straying or access to hedge clippings, with typical leaves being found in the rumen. In one confirmed case, where 20 sheep strayed into a garden, two animals showed signs of bruxism, abdominal pain and groaning. Parasitic diseases Thurso diagnosed chronic fasciolosis in a seven-year-old north country Cheviot ewe that was treated with a flukicide three weeks previously. The ewe was one of four found dead around a ring feeder two weeks prior to lambing. At postmortem examination the carcase was emaciated and oedematous. The liver serosa was scarred and the fibrosed bile ducts contained adult Fasciola hepatica. Welfare considerations, based on impending lambing and the poor body condition of the group, meant that it was more appropriate to treat with a different flukicide and postpone screening for resistance until a later date. Ideally monitoring for flukicide resistance should be carried out when ewes are healthy and mature infection is present, such as in late winter or early spring. Generalised and systemic conditions St. Boswells suspected tetanus caused two deaths in a group of 270 easy care hoggs from an unvaccinated organic flock that were fed on turnips and whole crop silage. Clinical examination of one hogg strongly suggested a diagnosis of tetanus as the findings included extensor muscle rigidity and hyperaesthesia. Serum magnesium and calcium were within the normal reference range. There were no significant gross postmortem findings and no evidence of cerebrocortical necrosis and focal symmetrical encephalomalacia on neurohistopathology. In the absence of a confirmatory test for tetanus, diagnosis is based on clinical signs plus exclusion of other neurological diseases. Cases of idiopathic tetanus have been described where, as in this case, there were no obvious wounds to explain the introduction of infection. It is assumed that either the toxin is ingested pre-formed or Clostridium tetani contaminates the food and toxin is produced in the rumen. Alternatively the spores may be introduced via a wound and lie dormant until conditions favour their multiplication. Rough, fibrous feeds have also been implicated as a predisposing factor possibly allowing bacterial entry via wounds in the mouth. As a precaution it was recommended to remove the hoggs from the turnips. Ayr diagnosed pulpy kidney disease in two one-day-old lambs that died suddenly. One lamb had absorbed sufficient colostral antibodies (ZST, 33 units; reference range greater than 14 units) and the other lamb had complete failure of passive transfer (ZST, 1 unit). Both lambs had a hydropericardium with fibrin clot (Fig 4) and one lamb had two small areas of necrotic small intestine. Clostridial epsilon toxin was detected from small intestinal content in both lambs. This toxin is associated with Clostridium perfringens type D, the cause of pulpy kidney disease. The farm had not vaccinated the ewes against clostridial disease for many years. 3

4 Fig 4 Pulpy kidney disease. Fibrin clot in pericardium Nervous system disorders Dumfries examined a three-year-old Lleyn ewe, one of three from a group of 190 three weeks pre-lambing that were found dead. Postmortem examination revealed pulmonary oedema and myocardial haemorrhages but no bacteria were recovered. Histopathology revealed a generalised lymphocytic meningoencephalitis consistent with an infectious cause that was most likely to be viral. Ticks were not seen and serology for louping-ill was negative. Immunohistochemistry is being carried out to further investigate the problem. Listeriosis was diagnosed on 12 occasions during March with Inverness confirming the condition on five occasions. This total is in excess of the previous four years, when in the same period between two and five diagnoses were recorded. PIGS Generalised and systemic conditions The cause of increased sow mortality on a 700 sow breeding unit was investigated. Sows were vaccinated against porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza, Erysipelothrix rhusiopathiae, E. coli and Clostridia perfringens. Four sows died over a weekend and the attending veterinary surgeon noted that 30 to 40 per cent of sows had blue or red discolouration of their ears. At an on-farm postmortem examination endocarditis was present in two sows. Heart tissue culture revealed a moderate growth of predominantly E. rhusiopathiae. Blood tests were negative for PRRS viral RNA. Further investigation is underway to investigate whether the cause of infection was due to vaccine failure or inappropriate administration. Mulberry heart disease was diagnosed in a seven-weekold male Hampshire pig, from a breeding to finishing unit, where several sudden deaths recently occurred. Postmortem findings suspicious of Glasser's disease (Haemophilus parasuis) were seen in a previous submission, although the no bacteria of note were isolated. At postmortem examination the carcase was congested throughout and there were mild excesses of fluid in the abdomen, thoracic cavity and pericardial sac. There was foam distally in the trachea and the lungs were congested with some mild interlobular oedema. No significant bacteria were isolated. Histopathology revealed acute degenerative cardiomyopathy, consistent with a diagnosis of mulberry heart disease. There were no significant inflammatory changes in any tissues to indicate a bacteraemia or septicaemia. Advice was given regarding adequate vitamin E in the diet. Respiratory tract conditions Pasteurellosis was diagnosed as the cause of death in a pet miniature pig that was purchased three weeks previously from a breeder. The pig was housed in garden shed over night with access to a wood-chip pen during the day. The pig was in good health the previous night, but was found recumbent and foaming at mouth the following morning and subsequently euthanased on humane grounds. At postmortem examination there was foam in the trachea, which contained small flecks of purulent material. Diffuse pulmonary congestion and interstitial oedema were present and there was salmonpink coloured consolidation of the cranial lobes. A pure and profuse growth of Pasteurella multocida was isolated from lung tissue. Alimentary tract conditions An outbreak of diarrhoea in five-week-old piglets with 3 per cent mortality was attributed to a F18 strain of E. coli. At postmortem examination four freshly euthansed, diarrhoeic piglets had full stomachs, watery-grey intestinal contents and congested small intestines. There was no evidence of oedema disease. Histopathological examination of intestinal tissues showed attaching coliforms particularly affecting the ileum. Beta-haemolytic E. coli, positive for the F18 fimbrial adhesin target, was isolated from the ileum of all four piglets, but there was no indication that they were Shiga toxin producers. The isolates showed in vitro resistance to tetracycline, but were sensitive to all other antimicrobial agents in the test panels. BIRDS Poultry Ayr examined a bantam hen from a backyard flock that was lame and had lost condition over a two week period before death. At postmortem examination, muscle 4

5 wastage was evident and the sciatic nerves were enlarged. Histopathological examination of both nerves revealed lymphocytic infiltrations. These nerve lesions were consistent with Marek's disease. Dumfries examined a seven-month-old layer hen, from a backyard flock of 15 birds, that was found unable to support its weight or use its wings despite being apparently normal the previous day. The bird deteriorated quickly and was reported to convulse prior to death. Small numbers of lice were found on the carcase, the gizzard was empty and there was green staining around the vent and a small amount on green liquid within the crop. There was pericardial effusion and a small amount of straw coloured ascitic fluid. The liver and spleen were massively enlarged and indistinct white spots less than 1 mm were seen on the spleen. Histopathology confirmed a diagnosis of erythroblastosis with suspected concurrent myeloblastosis. This condition is due to infection with avian leucosis virus, which is most often transmitted vertically through the egg. Five other birds in the flock were purchased from the same source and could be potentially infected. Perth isolated Aspergillus versicolor from lung tissue submitted to investigate the cause of respiratory signs and increased mortality in a shed of 35-day-old broilers. Postmortem examinations by the practice veterinarian showed granulomatous type masses in the lungs. Birds come into contact with Aspergillus species through contaminated feed, litter or premises. Most healthy birds can withstand repeated exposure to these organisms, but inhalation of large amounts of the organism, or reduced resistance in birds due to stress, or an underlying disease may result in infection. Raptors Thurso examined an adult short-eared owl that was found dead beside a wind turbine. On gross examination there was a compound fracture of the right humerus, a fracture of the right side of the pelvis and contusions to the right lung, kidney and right lobe of the liver. The injuries were consistent with collision with a wind turbine blade. MISCELLANEOUS Camelids St Boswells examined an eight-month-old male Huacaya alpaca (Vicugna pacos) that was found dead. The animal was kept with another three alpacas and seven llamas and fed hay, barley straw and commercially available camelid feed. At postmortem examination one ulcer was present on the oesophageal sphincter and two others on the horizontal pillar of C1 (first chamber). All ulcers were approximately 2 cm in diameter with overlying cream caseous material. Histopathology confirmed extensive and deep ulceration of C1, with heavy bacterial colonisation of the ulcer bed. There was also gross evidence of peritonitis and this was supported by vast numbers of bacteria and some inflammatory cells on cytology. There was an incidental finding of Trichuris species worms in the colon and faecal worm egg examination revealed 300 Trichuris species eggs per gram. SAC C VS speculated that the ulceration in C1 may have been a portal of entry for bacteria that in turn spread systemically to cause peritonitis. Pestivirus and BVDV were not detected by PCR and the cause of the ulceration was unclear. Ulceration is a common finding in South American camelids, although it is more commonly seen in the acid-secreting distal portion of C3 (third chamber). The aetiology of gastric ulceration in camelids is poorly understood. Factors such as stress, or dietary imbalances which predispose to acidosis, are considered to be possible contributors in cases with an absence of physical irritants such as foreign bodies, hairballs or gastroliths (Vencanto and others, 2012) Exotic animals Perth diagnosed myocardial fibrosis of unknown aetiology in an adult male nilgai (Boselaphus tragocamelus) that had shown poor body condition before recumbency and euthanasia on welfare grounds. At postmortem examination the skin was alopecic, thickened and lichenified, due to a dermatophyte infection. Some grossly fibrous areas were noted in the myocardium and the intestinal contents were fluid to soft. Histopathology revealed the myocardium to be replaced in some areas by multiple anastomosing bands of fibrous connective tissue which consisted largely of mature collagen with scattered fibrocytes and fibroblasts. Fibrosed areas contained negligible inflammatory cells. Remaining fibres often had granular sarcoplasm and were somewhat poorly defined, merging into neighbouring fibres. Pulmonary oedema and congestion was present that thought to be secondary to the myocardial changes, as there were increased numbers of alveolar macrophages in response to chronic oedema, with haemosiderophages ( heart failure cells ). A moderate lymphoplasmacytic and eosinophilic enteritis was also seen, which was suspected to be related to parasitism. References: CHO, D. Y.& LEIPOLD, H. W. (1978) Cerebellar Cortical Atrophy in a Charolais Calf. Veterinary Pathology 15, VENCANTO, J., FIORE, E., MORGANTE, M. and STELLETA, C. (2012) Gastric ulcers in South American Camelids. Large Animal Review 18:

6 Feature: Clostridial disease in cattle in 2014 Clostridial spores are widespread in the environment, particularly in soil and decomposing organic material. Latent spores can become activated within an animal leading to toxin production and rapid death. Most recorded deaths from clostridial disease were due to blackleg (gangrenous myositis) caused by Clostridium chauvoei (Fig (a)). Young stock, aged six to 24 months, were most commonly affected. At postmortem examination affected muscle masses are emphysematous and a gelatinous exudate may be present. Lesions are commonly seen in the large foreleg and hindquarter muscles, but also in the heart/pericardium and other muscle groups. Gas gangrene (false blackleg or malignant oedema) can be caused by several different clostridia, but usually Clostridium septicum, and has been reported following intramuscular injection where there is localised tissue necrosis. Black disease caused by Clostridium novyi results from liver damage caused by migrating immature fluke. An appropriate fluke control programme will aid in prevention. Clostridial enterotoxaemias are recorded as causing sudden deaths in cattle, but are not as easily recognised as in sheep. Clostridium perfringens type D is the most common cause of enterotoxaemia. Clostridial toxin may be detected in gut contents and on neuropathology focal symmetrical encephalomalacia (FSE) may be present. SAC C VS recorded small numbers of tetanus and botulism cases in Both diseases are sporadic and may affect cattle of all ages. Tetanus can have an incubation period of several weeks and may be associated with contaminated wounds or damaged tissue. Botulinum toxin proliferates in decaying carcases and vegetable matter and in bovine botulism is often associated with broiler litter. Clostridium sordellii abomasitis in calves is also occasionally diagnosed. Prevention of clostridial disease is by the use of single or multivalent vaccines Clostridial Diseases in Cattle 2014 No of diagnoses Fig. (a) 6