Lamb dysentery causes losses in Scottish sheep flocks
2021; Wiley; Volume: 188; Issue: 12 Linguagem: Inglês
10.1002/vetr.657
ISSN2042-7670
Tópico(s)Agricultural and Financial Auditing
ResumoVeterinary RecordVolume 188, Issue 12 p. 462-465 SurveillanceFree Access Lamb dysentery causes losses in Scottish sheep flocks First published: 18 June 2021 https://doi.org/10.1002/vetr.657AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat THE mean temperature in Scotland in April was 1.5°C below the long-term average, with overnight temperatures being lowest relative to average. Scotland overall had 39 per cent of average rainfall, though parts of northern Scotland received relatively close to their average rainfall totals. Sunshine totals were 160 per cent of average, making it the sunniest April since 1919. Cattle Nutritional and metabolic disorders Hypomagnesaemia was diagnosed in a 170-cow spring-calving herd that had been outwintered on grass, straw and Himalayan salt licks. These licks consist largely of sodium chloride, but no magnesium supplementation was provided. One cow was found dead, a second was recumbent and others appeared lethargic. Four animals were blood sampled and magnesium results between 0.5 and 0.59 mmol/l (reference range >0.8 mmol/l) confirmed the diagnosis. Musculoskeletal disorders Ten per cent of a group of 40 to 50 10-month-old Holstein cross finishing cattle became lame involving multiple limbs. The animals had been purchased at three to four months of age and were initially fed a proprietary starter pellet before transitioning onto a home mix of 80 per cent barley, 5 per cent soya and 15 per cent sugar beet pulp. Salt licks were available but there was no additional mineral supplementation. Hay and straw were provided initially and replaced with silage from eight months of age. ABOUT THIS REPORT This monthly summary is produced for Vet Record by Scotland's Rural College Veterinary Services (SRUC VS) and is based on reports from its surveillance centres in Edinburgh, Perth, St Boswells, Ayr (Auchincruive), Dumfries, Aberdeen, Inverness and Thurso and in collaboration with the Moredun Research Institute and the University of Glasgow School of Veterinary Medicine. SRUC VS monthly reports are available online at www.sruc.ac.uk/downloads/120613/monthly_reports from the first of every month. SRUC VS DISEASE SURVEILLANCE HEADLINES, APRIL 2021 Hypomagnesaemia in cattle and sheep Congenital intestinal atresia in beef calves Abortion associated with Anaplasma phagocytophilum in sheep Malignant catarrhal fever in farmed red deer One animal with bilateral swelling of its stifle and elbow joints was euthanased for investigation of the problem. Postmortem examination detected excess yellow synovial fluid and extensive defects of the articular cartilage affecting the distal humeri and femurs (Fig 1). Histopathology confirmed severe osteochondrosis lesions of the femur and humerus, and microscopic lesions in the rib. Fig 1Open in figure viewerPowerPoint Osteochondrosis lesion on the articular surface of the distal humerus of a 10-month-old Holstein cross stirk SRUC VS commented that osteochondritis dissecans lesions in the rib are unusual and were likely to reflect the severity of the condition. No significant abnormality was detected on biochemical analysis of bone. The primary lesion in osteochondrosis is considered to be focal failure of blood supply to the growing cartilage. The development of osteochondrosis in cattle is likely to be similar to pigs and horses, in which multiple factors are involved, including conformation and trauma associated with exercise in predisposed very rapidly growing animals. Diets based on barley and soya are low in calcium and advice on mineral supplementation was provided. Generalised and systemic conditions An on-farm postmortem examination was carried out following euthanasia of a three-week-old Limousin calf that had failed to respond to treatment for lameness. The left fore and right hind fetlocks were reported to be swollen and there was a clear demarcation between normal tissue and the distal limbs, which had a necrotic appearance and were cold and insensitive to touch. Histopathology revealed nephritis consistent with a sequel to bacteraemic localisation and chronic fibrosing pneumonia and abscessation consistent with descending bacterial infection, with the characteristics of the collagen indicating a duration of at least three weeks. The limb lesions were confirmed to be a result of distal limb ischaemia, most likely associated with disseminated intravascular coagulation, for which the commonest underlying cause is bacterial septicaemia. The overall findings suggested that the lung lesions had occurred in utero, most probably secondary to bacterial placentitis; however, it was unclear if the limb lesions related to the in-utero infection or were associated with postnatal septicaemia. Tissues from a two-month-old Limousin cross calf were submitted for investigation of diarrhoea and pneumonia. A bacterial pneumonia was identified, and Mannheimia haemolytica was isolated. Histopathology of intestinal tissue detected widespread mucosal damage focused on the crypts and glands with collapse into the Peyer's patches of the ileum. This was considered to be consistent with transient bovine viral diarrhoea virus (BVDV) infection although no BVDV was detected in this case. However, the herd had recently shown evidence of BVDV infection. Alimentary tract disorders Three cases of congenital intestinal atresia were diagnosed in beef suckler calves during April. Two had atresia jejuni (Fig 2) which caused abdominal distension due to accumulation of fluid and gas within the stomachs and proximal small intestines. One calf was delivered by caesarean as a result. Fig 2Open in figure viewerPowerPoint Jejunal atresia in a Simmental calf The third calf died at two days of age and in this case the small intestine and particularly the caecum were distended by fluid and gas, and there was no connection to the colon, which was empty of content. Possible explanations for congenital intestinal atresia include failure of blood supply leading to localised ischaemia and abnormal intestinal development; or more plausibly, failure of the gut lumen to recanalise in early development, possibly due to aberrant genetic regulation of molecular pathways. Skin diseases A 1.2 kg cutaneous mass was removed from the neck of a one-week-old suckled calf and histopathology confirmed bovine dermal melanoma (Fig 3). Fig 3Open in figure viewerPowerPoint Congenital bovine dermal melanocytoma in a suckled calf Douglas Swaffield, Conanvet Congenital melanomas similar to this case have been recorded.1 It has been reported that melanocytic tumours account for 5 to 6 per cent of bovine neoplasms. Most bovine dermal melanocytic neoplasms with benign cytological characteristics do not metastasise, but a few have been reported to do so. Small ruminants Nutritional and metabolic disorders Hypomagnesaemia was confirmed as the cause of death in lambed ewes from three flocks during April. Three or more sudden deaths involving ewes at grass rearing one- to two-week-old twin lambs were reported in each case. Vitreous humour magnesium results ranged from 0.31 mmol/l to 0.56 mmol/l (reference range >0.65 mmol/l). Withdrawal of concentrate feed two days earlier was considered to have predisposed to the losses in one flock. Generalised and systemic conditions Multiple sudden deaths of lambs aged less than one week were reported from three flocks. Six carcases were submitted and postmortem findings, including haemorrhagic small intestinal content, mucosal reddening and haemorrhage and mural emphysema within the jejunal wall (Fig 4), suggested the possibility of enteritis associated with Clostridium perfringens type B. Fig 4Open in figure viewerPowerPoint Mural emphysema within the jejunum in a case of lamb dysentery C perfringens beta toxin was detected in the small intestinal contents in all cases consistent with a diagnosis of lamb dysentery. All of the affected flocks were lambing outdoors, and ewes had received a multivalent clostridial vaccine before lambing. No evidence of inadequate transfer of maternal colostral antibodies was found with all zinc sulfate turbidity results above the reference range of >14 units. Advice was given to check how the vaccine was stored, the timing of the primary course and the timing of boosters relative to lambing date. Reproductive tract conditions A newly established flock of 160 mixed breed gimmers purchased from multiple sources submitted two fetuses for postmortem examination after seven ewes aborted. Lambing was due to start in 10 days and ticks had been noted on the ewes. The group had been grazed on hill ground since tupping and had been moved closer to home one week previously. Diffuse subcutaneous oedema together with pleural and peritoneal effusions were found in both fetuses. Neuropathology detected multifocal necrosis of cerebral white matter and Anaplasma phagocytophilum DNA was detected in fetal spleen Transplacental transmission of A phagocytophilum has been recorded in sheep, and abortion linked to A phagocytophilum has been recorded in association with exposure of naive ewes in late pregnancy to high tick burdens.2, 3 Periventricular leucomalacia has been described in previous cases of tickborne fever abortion.4 Nervous system disorders A flock reported the birth of 10 shaky highlander lambs and submitted two for investigation of the issue which had recurred annually since 2018. Congenital brain malformations were confirmed, including microencephaly, cerebral gyral abnormalities, hydrocephalus and brainstem dysplasia. A genetically determined defect was considered to be the most likely explanation. Other breeds on the holding were not affected, and a single tup was thought to have sired all the affected lambs. The tup had died and was not available for further investigation. Pigs Generalised systemic diseases Clinical signs of enteritis, ataxia and sudden death were seen in recently weaned piglets in a high-health unit. The carcases of two five-week-old pigs were examined and profuse watery scour with admixed yellow fibrinous strands was the main finding. Escherichia coli was isolated from the intestines and detection of virulence factors F18, heat-stable toxin type 1 and heat-stable toxin type 2 confirmed a diagnosis of enteric colibacillosis. Histopathology revealed a large number of attaching coliforms coating the villi and colonising the crypts. SRUC VS OVINE ABORTION DIAGNOSES 2021 This spring SRUC VS received 326 submissions of ovine fetal material from 289 Scottish flocks to investigate the cause of abortion. A further 202 submissions were received from 190 farms outwith Scotland. A diagnosis was reached in 48 per cent of the submissions from Scottish flocks and in 41 per cent of the non-Scottish submissions in which the submission of postal samples was overrepresented. For 145 of 272 submissions (53 percent) examined in SRUC VS postmortem examination centres a diagnosis was reached, whereas the diagnostic rate for specimens taken on farm and sent to the central laboratory for specific screening was 37 per cent. Within these data there are submissions and farms with more than one diagnosed cause of abortion. The relative frequency of diagnoses is detailed in Table 1. As in previous years enzootic abortion of ewes (EAE) caused by Chlamydia abortus and Toxoplasma gondii were the most frequently made diagnoses in both sets of submissions, making up over 50 percent in the cases where a diagnosis was reached. Table 1. Causes of ovine abortion diagnosed in submissions made to SRUC VS between November 2020 and May 2021** 528 submissions of fetal material were received and 256 diagnoses were reached; up to two diagnoses can be made per submission Fetal material submitted to SRUC VS centres Fetal material collected on farm Overal Cause Count % Count % Count % Chlamydia abortus 50 32 37 37 87 34 Toxoplasma gondii 42 27 31 31 73 29 Diagnosis not listed 23 15 7 7 30 12 Listeria species 11 7 6 6 17 7 Campylobacter 11 7 4 4 15 6 Salmonella Montevideo 4 3 7 7 11 4 Dystocia 8 5 0 0 8 3 Other Salmonella species 2 13 5 5 7 3 Trueperella pyogenes 3 1.9 2 2 5 2 Border disease 0 0 1 1 1 0.4 Fungi 1 0.6 0 0 1 0.4 Yersinia species 1 0.6 0 0 1 0.4 Total 156 100 256 * 528 submissions of fetal material were received and 256 diagnoses were reached; up to two diagnoses can be made per submission Abortion due to Listeria species was diagnosed marginally more frequently (3 percent of this year's submissions) than in previous years. This may reflect the cold spring and slow grass growth increasing soil ingestion and prolonging feeding of supplementary forage. The ‘diagnosis not listed’ category consists predominantly of bacterial species isolated in pure growth from the fetal stomach contents and considered to be sporadic causes of abortion (eg, Mannheimia haemolytica, Staphylococcus aureus, Streptococcus dysgalactiae). There was no evidence of Schmallenberg virus contributing to ovine fetal loss in these submissions. Screening for border disease virus (BDV) infection is not part of the routine abortion investigation and testing is only carried out when indicated by the case history or a failure to reach an initial diagnosis on the standard examinations. Losses due to BDV in lambs up to one week of age were diagnosed in 12 flocks, only one of which was Scottish. A detailed case history was provided for 11 flocks and Fig A summarises this information, illustrating the range of issues that BDV can cause, with multiple problems reported in some flocks. Fig AOpen in figure viewerPowerPoint Reported presenting signs in cases of border disease virus infection The presence of bought-in sheep was specifically mentioned in three cases. PCR testing confirmed that all the outbreaks were due to BDV with no evidence of infection with bovine viral diarrhoea virus detected. Miscellaneous species Deer Three farmed red deer aged between nine and 12 months died unexpectedly, or following a short illness, on one holding over three weeks. The group of 60 had been housed on hay and concentrate feed throughout the winter. Two carcases were submitted for postmortem examinations. The main findings were haemorrhagic content and dark-red mucosa in the large intestines of both deer together with haemorrhages in the caecal mucosa in one animal. Postmortem change hampered histopathological examination of the intestines; however, multisystemic angiocentric lymphocytic inflammation was detected in several organs, including brain, kidney and lungs. Ovine herpesvirus type 2 DNA was detected in both animals which, together with the histological findings, was consistent with a diagnosis of malignant catarrhal fever (MCF). DISEASE ALERTS The following conditions were reported by SRUC VS disease surveillance centres in July 2020. Given similar climatic and production conditions, they could also be important this year. Lead poisoning in cattle Diagnoses of lead poisoning peak during the grazing season and youngstock aged under two years account for the majority of cases. Discarded lead batteries are a common source of exposure and farmers should be encouraged to inspect fields before they are grazed. Pulpy kidney in lambs Any passive immunity acquired by lambs from colostrum as a result of prelambing clostridial vaccination of ewes will have waned by July. Lambs are not fully protected until two weeks after their second vaccination. An ‘immunity gap’ leading to losses can occur unless lamb vaccination is initiated when they are aged six weeks or younger. Sudden unexpected death or haemorrhagic enterocolitis are the most common presenting signs of MCF in deer, similar to the peracute or alimentary presentation in cattle in which vasculitis is an uncommon feature. References 1Miller MA, Weaver AD, Stogsdill PL, et al. Cutaneous melanocytomas in 10 young cattle. Vet Pathol 1995: 32: 479– 84CrossrefCASPubMedWeb of Science®Google Scholar 2Stuen S, Okstad W, Sagen AM. Intrauterine transmission of Anaplasma phagocytophilum in persistently infected lambs. Vet Sci 2018; 5: 25CrossrefGoogle Scholar 3Jones GL, Davies IH. An ovine abortion storm caused by infection with Cytoecetes phagocytophila. Vet Rec 1995; 136: 127CrossrefCASPubMedWeb of Science®Google Scholar 4Chianini F, Buxton D, Adams C. Neuropathological changes in ovine fetuses caused by tickborne fever. Vet Rec 2004; 155: 805– 6Wiley Online LibraryCASPubMedWeb of Science®Google Scholar CONTACTING SRUC VS SRUC Veterinary Services can be contacted by telephone on 0131 535 3130 or by email: vcedinburgh@sac.co.uk Contact details for local SRUC VS disease surveillance centres are available at www.sruc.ac.uk/contactvetservices Volume188, Issue1219 June–3 July 2021Pages 462-465 FiguresReferencesRelatedInformation
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