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Download SAC C VS Monthly Report for November 2014
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SAC C VS Monthly Report for November 2014 OVERVIEW Leptospiral milk drop in dairy cows Pseudomonas aeruginosa mastitis in a cow Systemic pasteurellosis in lambs Encephalopathy due to water deprivation/salt poisoning suspected in weaned lambs Biliary cystadenoma in a red deer hind GENERAL INTRODUCTION The month was generally unsettled but mild with fewer frosts than average. Rainfall overall was 79 per cent of average, with the north-west receiving less than half the normal rainfall amount. Sunshine amounts were 94 per cent of average overall. Eastern areas were dull; whereas, the west received above average sunshine. Scottish poultry producers were advised to stay vigilant following an outbreak of avian influenza on a duck breeding farm in East Yorkshire. DISEASE ALERTS The following conditions were reported by SAC C VS disease surveillance centres in March 2014. Given similar climatic and production conditions, they could also be important this year. Iodine deficiency in aborted calves Diarrhoea in neonatal calves associated with low zinc sulphate turbidity levels Sheep abortions due to Chlamydophila, Toxoplasma and Campylobacter Hypocalcaemia in ewes Listeriosis in sheep CATTLE Generalised and systemic conditions Ayr diagnosed milk drop due to leptospirosis in a dairy herd. Twelve cows from a herd of 160 experienced a sudden onset drop in milk production, with no other clinical signs observed. Acute and convalescent blood samples from two affected cows showed seroconversion to Leptospira Hardjo on ELISA testing. In addition, quarterly bulk milk testing demonstrated recent elevation in antibodies to L. Hardjo. The affected animals had access to a stream shortly before the first case of milk drop was observed. SAC C VS considered that this natural water course may have been the source of infection. Respiratory tract diseases There was an increase in the number of carcases and samples submitted to investigate outbreaks of pneumonia since housing. Lungworm infection continued to be diagnosed this month. Aberdeen diagnosed parasitic pneumonia in a group of 30 recently-housed, weaned calves. Six calves had signs of respiratory disease and one of these died. At postmortem examination large numbers of lungworms were seen in the airways, the cranioventral lung lobes were consolidated and the caudal lobes emphysematous. Mannheimia haemolytica was recovered from lung lesions. Outbreaks of viral pneumonia were commonly diagnosed. Bovine herpes virus 1 (BHV-1) was most frequently identified, diagnoses being made by PCR testing of swabs (ocular, nasal or nasopharyngeal) or by postmortem examination, where typical findings were marked tracheitis with a necrotic diphtheritic membrane and secondary lung consolidation. Ayr diagnosed acute pneumonia in a five-month-old Aberdeen Angus-cross bull calf that died within an hour of antibacterial and anti-inflammatory treatment. At postmortem examination red consolidation of the cranial lung lobes, interstitial emphysema and emphysematous bullae of the caudal lung lobes were present. Bibersteinia trehalosi and Histophilus somni were recovered from lung lesions, but screening for respiratory viruses (BHV-!, parainfluenza virus 3 (PI3V) and respiratory syncytial virus (RSV)) by PCR was negative. Histological examination of the lungs identified acute suppurative pneumonia and pleurisy of bacterial aetiology, consistent with infection by the isolated organisms. Acute bronchointerstitial pneumonia was also present. SAC C VS commented that while this is not a specific change, viral infection is considered the most likely cause. Although RSV and PI3V were excluded by PCR testing another virus (e.g. bovine coronavirus) could be involved. Other possible causes include toxicity and acute systemic disease. Acute interstitial pneumonia is a well recognised condition in feed-lot cattle in the USA, where it is thought to be associated with 3-methylindole and is most common in calves with previously damaged lungs (Loneragan and others, 2001). In this case there was evidence of chronic lung damage in the form of airway fibrosis. Reproductive tract conditions Aberdeen diagnosed Campylobacter fetus abortion in a four-month-old foetus from a beef suckler cow, the first to abort from a group of one hundred. The farmer reported Part-funded by the Scottish Government as part of its Public Good Veterinary Advice Services 1 a high proportion of barren cows at scanning. The foetus was autolytic and partially predated with the stomach and intestinal tract missing. A pure growth of C. fetus was recovered from lung tissue. SAC C VS advised that when C. fetus is isolated from an aborted calf and there is evidence of infertility in the herd, the possibility of venereal campylobacteriosis should be considered. Musculo-skeletal conditions Perth diagnosed ulcerative, necrotising dermatitis and cellulitis in a recently purchased three-year-old HolsteinFriesian heifer, from a group of 60 with milk drop and condition loss after calving. Two animals died and others had swollen limbs. The heifers were fed a total mixed ration, which on analysis was deficient in protein. Recent blood testing of the cohort revealed consistent hypoalbuminaemia and urea values below reference range. At postmortem examination, body condition was poor and a soft swelling was seen around the right hock. An abscess discharging thick yellow pus was present in one quarter of the udder. Severe erosive lesions were found in the interdigital skin of all four feet with complete loss of the interdigital skin in some areas (Fig 1). energy balance, was identified. SAC C VS considered that this would likely have resulted in compromised immune defences and a review of nutrition was advised. Mammary diseases Dumfries diagnosed Pseudomonas aeruginosa mastitis in a cow that died suddenly. This was the third cow in two weeks to die within five days of drying off. On the affected farm, cows were routinely treated with dry cow antibiotic tubes and teat sealant at dry off. At postmortem examination the eyes were sunken, there was a blue tinge around all teats and teat sealant was present in the teat canals. Three of the quarters had fibrinous and fibrinopurulent material present within the gland and there was extensive consolidation and inflammation in one quarter (Fig 2). Fig 2. Pseudomonas aeruginosa mastitis in a cow Fig 1. Erosion of interdigital skin in a cow Three of the limbs had purulent cellulitis and there were areas of significant under-running of the skin with purulent tracts. Trueperella pyogenes was recovered from lesions. Screening for bovine viral diarhoea virus by PCR proved negative. Histopathology revealed extensive necrosis and ulceration of the interdigital skin associated with mixed bacterial colonisation and active cellulitis. SAC C VS commented that, at this chronic stage, the original insult causing the breach of epidermal integrity could no longer be determined. Fusobacterium necrophorum infection or treponemes (associated with digital dermatitis) were possible differential diagnoses and examination of the feet of all heifers in the group was advised. In addition fatty liver, indicative of negative A pure, heavy growth of P. aeruginosa was recovered from all quarters. SAC C VS advised that this organism is usually associated with contaminated water. Cases postdrying off have been associated with hygiene issues such as pre-warming syringes in water, hosing dirty udders prior to dry cow tube infusion and in cows lying in wet conditions in the days immediately following drying off. P. aeruginosa was not isolated from samples of udder cloths, hoses, hose water or teat dips. SMALL RUMINANTS Nutritional and metabolic disorders Edinburgh diagnosed ruminal acidosis in a six-month-old Scottish blackface tup from a hill-grazing group of 150. Six were found dead since the introduction of barley three days earlier. At postmortem examination the rumen contained wet fibre and grain and had a pH of 3.5. Thurso and St. Boswells also reported sudden deaths of lambs due to ruminal acidosis following the recent introduction of barley and Inverness reported similar Part-funded by the Scottish Government as part of its Public Good Veterinary Advice Services 2 losses after lambs were moved to a stubble field. SAC C VS recommended introducing high carbohydrate feeds slowly over a few weeks and, when not feeding ad lib, ensuring sufficient trough space for all animals to access the feed at the same time. Parasitic diseases Parasitic gastroenteritis was diagnosed on 26 occasions during November 2014 compared to 19 occasions during the same period in both 2012 and 2013. The increase may reflect the mild weather that continued throughout most of November and allowed continued hatching of eggs and development of larvae to the infectious L3 stage. Generalised and systemic conditions November saw the expected peak of sudden deaths in lambs due to systemic pasteurellosis with a total of 13 diagnoses. St. Boswells diagnosed the condition on four farms and in all cases B. trehalosi was cultured from both lung and liver (Table 1). Two flocks had used pasteurella vaccine, one involved purchased animals of unknown vaccine status and one flock had not vaccinated. B. trehalosi can be found as a commensal organism in the nasopharynx and tonsils of healthy sheep. Changes in diet and weather are thought to be predisposing factors in multiplication of the organism and spread of bacterial emboli into the circulation (Donachie, 2007). Aberdeen also isolated B. trehalosi from viscera of a yearling goat. The cranial lung lobes showed severe bilateral consolidation and the liver contained numerous pale foci, less than 1 mm diameter, on the surface and throughout the parenchyma. These lesions are secondary to occlusion of blood vessels by bacterial emboli and, particularly if found together with oesophageal ulceration, suggest B. trehalosi infection. Alimentary tract disorders Perth diagnosed intestinal adenocarcinoma in a ewe that had shown wasting, wool loss and malaise for six weeks before death. At postmortem examination a large volume of orange peritoneal fluid with fibrinous peritonitis and serositis was seen. The jejunum was thickened, with an area of stricture. Histopathology revealed extensive deposits of fairly well-differentiated, mucoid, columnar epithelial cells infiltrating the submucosa of the small intestine. These changes were consistent with invasive scirrhous intestinal adenocarcinoma. The primary tumour site was not represented in the fixed tissue examined, but tumour cells were clearly infiltrating via the lymphatics. SAC C VS commented that intestinal adenocarcinoma is a well-described, debilitating condition in sheep, which is sometimes misdiagnosed as chronic peritonitis, as invading neoplastic cells evoke a marked fibrous reaction and adhesions. Hereditary factors, environmental carcinogens such as contained in bracken, or exposure to herbicides have been suggested as possible predisposing causes (Løken and others, 2012). Table 1: Significant history and necropsy findings in lambs diagnosed with systemic pasteurellosis Age Breed 6 months 8 months 8 months Highlander Number of deaths 4/400 Number of animals examined Texel 1/18 1 Suffolk X Texel 14/400 2 7 months Scottish blackface 6/275 1 4 Nervous system disorders Aberdeen diagnosed encephalopathy in a group of 100 weaned lambs that were gathered and separated according to body condition. Approximately 50 poorer lambs were given a trace element drench and housed, the remainder returning to grass. Forty-eight hours later many of the lambs appeared lethargic and the concentrate feed had not been eaten. Fifteen-to-twenty Significant postmortem findings Pulmonary congestion and interstitial oedema, oesophageal ulceration Multiple adhesions between lung and parietal pleura, lung consolidation, restrictive pericarditis Pleural, pericardial and peritoneal effusions (one animal only), lung congestion and interstitial oedema, congested liver Subcutaneous, pleural and pericardial haemorrhage, congested lungs, mottled liver showed signs of head-pressing and apparent blindness. One lamb was submitted live was in lateral recumbency showing signs of opisthotonus. The pupils were dilated and there was no menace response. There was evidence of parasitic gastroenteritis with a strongyle egg count of 12,400 eggs per gram, but diarrhoea was not present. There were no significant findings on gross postmortem examination. Part-funded by the Scottish Government as part of its Public Good Veterinary Advice Services 3 Neuropathology revealed severe, acute to sub-acute, generalised vacuolar leuko-encephalopathy and focal lesions of cerebrocortical necrosis, which were probably secondary to generalised brain swelling. Histopathology of liver and kidney did not reveal any changes to explain spongiform changes in the brain. Water deprivation/salt poisoning was considered a differential diagnosis and has been previously suspected in cases of encephalopathy in weaned lambs (Scholes and others, 2005). PIGS Generalised and systemic conditions Aberdeen diagnosed bacterial endocarditis in a group of seven-week-old cross-breed pigs that developed acute onset dyspnoea and cyanotic extremities, dying one to two days after showing clinical signs. At postmortem examination of one animal there was an excess of fluid in the thoracic cavity, interlobular oedema and patchy, dark-red pulmonary congestion. The heart appeared dilated and globular and there was an endocarditis with numerous small abscesses along the edge of the left atrio-ventricular valve. Streptococcus suis serotype 2 was isolated from the lung, liver and heart in mixed bacterial growths and almost pure growth from the heart valve. Alimentary tract disorders Aberdeen examined six pigs that were submitted live from a holding, in which about five per cent of the animals had ill-thrift. There were 3000 animals on the unit and batches were of 300 to 400 animals. At postmortem examination of three eight-week-old and three 11-week-old piglets, five animals had enteric changes with prominence of the lymphoid tissue of the ileum and thickening of the terminal ileum. There were raised white discs of lymphoid tissue over the serosa of the colon and the colon content was pasty. Findings were more pronounced in the older two animals; the spiral colon having copious liquid content. Laboratory testing and histopathology confirmed proliferative enteropathy in the ileum due to Lawsonia intracellularis infection. In the older pigs proliferative enteropathy affected both ileum and colon, with spirochaetal colitis due to Brachyspira pilosicoli also affecting the large intestine. BIRDS Poultry Inverness suspected infectious laryngotracheitis (ILT) was the cause of respiratory disease in a flock of 60 layer hens. The outbreak started in a show bird, which recovered after treatment with enrofloxacin. Thirty birds were subsequently purchased and several of these developed respiratory disease. Eighteen birds died and 12 birds showed clinical signs of respiratory disease. At postmortem examination an 18-week-old layer was lean and had an extensive biting louse infestation. Pathological lesions were confined to the upper respiratory tract and included a reddened infraorbital sinus containing sanguineous mucous and an inflamed tracheal mucosa that was covered by serosanguineous mucus and tissue debris. Histological examination of the infra-orbital sinus showed chronic, active inflammatory changes, with significant numbers of mononuclear cell infiltrates in addition to exudative processes. The trachea showed evidence of a chronic granulomatous tracheitis with a largely intact epithelium. Viral inclusions were not apparent, but the gross and histological changes in the respiratory tract were suggestive of ILT, which was complicated by bacterial infection of the sinuses. ILT is caused by Gallid herpesvirus 1, a pathogen that remains infectious for several weeks outside its host and causes latent infections. All ages of fowl are susceptible. SAC C VS advised vaccination to avoid further losses. Ayr examined three ten-day-old birds from a broiler unit. At postmortem examination one bird had an enlarged spleen and all three birds had enlarged bursae of Fabricius. Enterococcus hirae was isolated from all three birds. Enterococcus species are a normal part of the microflora in the intestinal tract of poultry but can cause disease, usually secondary to another infection. E. hirae is most commonly seen in either septicaemia/bacteraemia with focal symmetrical encephalomalacia in chicks (broilers and layers) between three- to eight-days-old or vegetative endocarditis with right-sided heart failure in slightly older broilers/broiler breeders, most commonly around 16-20 days old. Cage and Aviary Birds Perth found multiple foreign bodies in a three-year-old Humboldt penguin (Spheniscus humboldti). The bird was lethargic, in poor condition and regularly regurgitated its food. On radiography a mass was seen in the proventriculus and gizzard. At postmortem examination there was a large bundle of straight twigs, about 22 cm long and 7 cm in diameter, obstructing the proventriculus and gizzard. Just below the oesophageal opening, two small fish were seen on the twigs. There were erosions, covered with thick mucus, on the mucosa of the proventriculus and gizzard and the intestines were empty. Ingestion of foreign bodies is not uncommon in penguins and this penguin had a persistent habit of pica, having previously ingested many foreign bodies. Part-funded by the Scottish Government as part of its Public Good Veterinary Advice Services 4 MISCELLANEOUS Dogs St Boswells identified an intestinal torsion affecting a 65 cm section of the jejunum in an eight-week-old West Highland white terrier. The puppy had been found dead at 06-00, despite showing no obvious clinical signs three hours previously. The affected section of gut was clearly demarcated and deeply congested (Fig 3). The lumen contained bloody material and there was a moderate volume of strawcoloured peritoneal effusion. Torsion of the long axis of the mesentery is considered rare in dogs and cats (Brown and others, 2007). increasing number of deaths. Terminal convulsions had been seen. The carcase was in good condition and the stomach well filled. Multiple necrotic lesions of les or equal to 1 mm were found throughout the liver parenchyma. Liver tissue tested positive for RHDV-2 by PCR. RHDV is endemic and can cause high mortality, but the circulation of non-virulent strains in some rabbit populations is protective (Forrester and others, 2009). Local veterinary practices were alerted to the possible risk to pet rabbits. Perth diagnosed coccidiosis in a male hare, the sixth to be found dead on a farm since the previous May. The farmer had noticed an increase in the local hare population and several carcases were seen throughout the summer and autumn. At postmortem examination the anus and genital openings were blocked by a thick, sticky plug of faeces. Extrusion of the penis revealed faecal material in the urethral opening. The large intestine contained thick fluid material and the bladder was dilated with a large amount of brown urine, which could not be expressed. One of the renal pelvices appeared slightly dilated. Coccidial oocysts were not seen in a sample of intestinal content. However, histopathology revealed that many intestinal crypts were almost obliterated by large numbers of developing coccidia, with segmental areas of complete mucosal collapse (Fig 4). Fig 3. Intestinal torsion in a West Highland white terrier. Deer Inverness examined a liver from a shot red deer hind (Cervus elaphus). Vesicular liver lesions were seen at evisceration, and incisions into two lesions released over four litres of either brown-coloured or bloody fluid. The liver contained cysts of differing wall thickness with cyst diameters from under 1 cm to over 10 cm, with larger cysts having a cavernous lumen. Histopathology revealed extensive fibrosis which replaced most of the parenchyma, and contained scattered bile ducts and islands of hepatocytes. Multiple cyst-like spaces were lined by a single layer of cuboidal to flattened epithelial cells resembling biliary epithelium. The histological appearance resembled biliary cystadenoma, a benign biliary neoplasm. There was no evidence of Echinococcus tapeworm cysts. Wild animals Dumfries diagnosed Rabbit Haemorrhagic Disease Virus type 2 (RHDV-2) in a young wild rabbit, submitted by a member of the public who noticed an Fig 4. Coccidiosis in a hare Part-funded by the Scottish Government as part of its Public Good Veterinary Advice Services 5 Feature – Tickborne Diseases Reports of increased tick numbers and geographical spread over the past decade have led to concerns that tickborne disease is more common. The sheep tick Ixodes ricinus is the only species native to Britain associated with transmission of disease. Disease is associated with peaks of tick activity, which are temperature- and humidity-dependent. Warmer, wetter conditions can allow ticks to be active in most months of the year. The tickborne pathogens of most concern are Louping-ill virus, Babesia divergens, Anaplasma phagocytophilium and Borrelia burgdorferi. Louping-ill virus causes neurological signs and death in a wide range of species including sheep, cattle, red grouse and people. High mortality may occur when immunologically naïve animals are introduced to a tickinfested area. Losses can be minimised by the use of louping-ill vaccine in sheep. A. phagocytophilium causes tickborne fever of sheep and cattle. Infection causes immunosuppression and an increased susceptibility to secondary infections, including tick pyaemia. Naïve sheep and cattle may abort when exposed to infected ticks. The main methods of disease prevention are avoiding exposure of pregnant animals and tick control by the use of ectoparasiticides. Tickborne fever may be underdiagnosed due to the lack of a commercially available serological test. Babesiosis (‘redwater’) is a disease of cattle caused by the protozoan parasite B. divergens. The disease rarely occurs in herds originating from infected areas. Susceptible older cattle may become ill, or even die due to a haemolytic crisis, when exposed to infection. Lyme disease, caused by B. burgdorferi bacteria, can cause serious disease in humans, particularly if not identified early. It may also affect companion animals including dogs, cats and horses. Wild rodents are important for the transmission of the disease. There were 173 diagnoses of tickborne disease by SACCVS from 2009 to October 2014. Louping-ill was the most common diagnosis at 69 per cent, babesiosis at 12 per cent and tickborne fever at 10 per cent. Tick pyaemia accounted for the remaining diagnoses. Lyme disease cases were not included as they rarely affect farmed species. Continued surveillance is necessary to determine if climate change and rising tick numbers lead to an increase in reports of tickborne disease in farm animals, domestic pets and humans. Part-funded by the Scottish Government as part of its Public Good Veterinary Advice Services 6