GB surveillance Safeguarding public and animal health cattle diseases Quarterly Report: FIRST QUARTER Date: Jan March 2010 The VIDA diagnoses are recorded on the VLA FarmFile database and SAC LIMS database and comply with agreed diagnostic criteria against which regular validations and audits are undertaken. The investigational expertise and comprehensive diagnostic laboratory facilities of both VLA and SAC are widely acknowledged, and unusual disease problems tend to be referred to either. However recognised conditions where there is either no diagnostic test, or a clinical diagnosis offers sufficient specificity to negate the need for laboratory investigation, are unlikely to be represented. The report may therefore be biased in favour of unusual incidents or those diseases that require laboratory investigation for confirmation. VLA RLs have UKAS Accreditation and comply with ISO 17025 standard. SAC Veterinary Services have UKAS accreditation at their central diagnostic laboratory and at their Edinburgh and St Boswells Disease Surveillance Centres which comply with ISO 17025 standard. Contents page Introduction to GB report 2 Overview Factors influencing disease and submission rates 2-4 Notifications of suspected notifiable disease 4-5 Brucella surveillance 5-6 Investigatory and advisory farm visits 6 Chemical food safety incidents 6-7 Endemic disease surveillance 7-9 Unusual and new diseases 9-10 Scanning surveillance for new and emerging diseases 10-11 Horizon scanning 12 Highlights Further increase in scanning surveillance submissions of both samples and carcases for necropsy, and from both dairy and beef cattle. Two further cases of psoroptic mange diagnosed in southern Wales but further spread to the rest of GB not identified. Continued high rate of fasciolosis in cattle in GB. Several possible cases of notifiable diseases were reported and investigated, with Animal Health. Notifiable disease was negated in all cases. Further cases of Bovine Neonatal Pancytopenia were diagnosed.
INTRODUCTION The aims of this report, and the means by which it is produced, are available at: http://www.defra.gov.uk/vla/reports/docs/rep_survrep_qtlyc_intro.pdf OVERVIEW Factors influencing disease and submission rates Many factors combine to influence the patterns of disease in cattle, and the ability to detect changes to these patterns through scanning and active surveillance. They include: Cattle Demographics The UK cattle population is the third largest in the EU and comprises 8.6 million animals on 77,736 premises (July 2008, RADAR, Defra). The map below shows the density of cattle and the location of the diagnostic laboratories that contribute data to this report. Figure 1 Distribution of cattle and location of diagnostic centres in Great Britain (2007) 2
Weather and climate January was a particularly cold and dry month. February was also drier than usual in most of GB except southern England, which experienced about 130% of mean monthly rainfall. There is anecdotal evidence that the cold dry weather had minimal effect on the condition and health of cattle in GB most of which are housed over the winter and almost all of which are fed conserved forage in the winter months. It is likely that the cold weather would have reduced the survival of overwintering, free-living parasitic larvae and cysts, so there could be reduced risk of diseases such as fasciolosis in future quarters. Economics of the cattle industries In general when profit margins of the industries are acceptable there is a greater tendency to use disease diagnosis in the health management of the individual herd. The effectiveness of the scanning surveillance carried out by SAC and VLA is therefore related directly to the financial health of the industry. The current economic climate is likely to promote scanning surveillance submissions. Dairy sector: The weak pound has encouraged export and made import of agricultural produce less attractive. Hence prices of dairy cows and calves have remained firm and the milk price is largely unchanged compared with last quarter (average 24 pence per litre). Beef sector: Beef prices remained high at 280 285 pence/kg dead weight although slightly less compared to this time last year when it was over 290 pence/kg. The price and an increased consumer demand for beef during the cold spell in January helped to boost beef sales in this quarter. Submission numbers In the first quarter of 2010, there were 11,482 bovine diagnostic submissions and 1,126 carcases for necropsy. Both were the largest number for this quarter in recent years (Table 1); probably due, at least in part, to the relatively good economic performance of the cattle sector. The increase was for both dairy and beef farms and occurred in all regions of GB, particularly in Scotland but less so in Wales (see figure 2). Table 1 Cattle diagnostic submissions in England and Wales and Scotland First Quarter Total Submissions Number of Carcases E&W Scotland Total E&W Scotland Total 2010 8,503 2,979 11,482 850 276 1,126 2009 8,202 2,388 10,590 826 222 1,048 2008 7,578 2,509 10,087 614 234 848 2007 7,047 2,197 9,244 605 223 828 2006 7,639 2,474 10,113 653 236 889 3
Figure 2 Bovine diagnostic submissions to the VLA and SAC, in the first quarter of 2010 and 2009, for comparison. (E=East; N=North; W=West; Unk = not recorded) 4,000 3,500 3,000 2,500 2,000 1,500 1,000 500 0 2009 E Eng 2010 E Eng 2009 N Eng 2010 N Eng 2009 2010 Scotland Scotland 2009 Wales 2010 Wales 2009 W Eng 2010 W Eng 2009 Unk 2010 Unk Beef Dairy Unknown/Other Notifications of suspected notifiable disease The following notifications of suspected notifiable disease, which were all confirmed as negative by subsequent investigation, were made this quarter: Enzootic bovine leukosis (EBL): A single, 10cm diameter mass, close to the cervical oesophagus in an adult cow was reported to Animal Health as a possible tumour. Subsequent serological examination was negative for EBL antibody. The mass was of unknown aetiology but was probably a granuloma. Severe enlargement with necrosis of the lymph nodes of the neck and the thymus of a yearling bull was reported as both possible EBL and possible tuberculosis. The former was ruled out by serology and the latter by histopathology. Sporadic lymphoma was the cause of these lesions. EBL was ruled out by PCR in a nine year old suckler cow with multifocal lymphoma of muscle, lung lymph nodes and epidural space of the spine. Foot and mouth disease (FMD): Animal Health was consulted about suspicion of possible FMD in a 6 week old calf, the second to die at about this age in a 270 cow mixed dairy and suckler farm. The calf had lesions of intense erythema of the coronary band and varying degrees of ulceration in the interdigital cleft of all four feet; shallow ulcers on the pasterns and fetlocks; small (approximately 1 mm diameter) vesicles and ulcers on the cranial border of the tongue; two shallow ulcers on the dental palate and two coalescing ulcers on the left side of the inner lower lip. FMD was ruled out when a Veterinary Officer visited the farm and did not find suspicious lesions of FMD in the other cattle. The cause of the lesions was not determined, despite extensive laboratory and histopathological investigation, but they may have been associated with sequelae of omphalitis (navel ill). Animal Health was also consulted when well-demarcated, ulcerated lesions were found in the interdigital cleft of both forelimbs and one hind foot of a one week old calf. Tags of skin resembling ruptured vesicles overlaid some of these lesions and the underlying ulcerated area was reddened. There was also generalised petechial haemorrhage and focal pneumonia. FMD 4
was ruled out on epidemiological and gross pathological grounds and a diagnosis of Salmonella Dublin infection was subsequently made. Congenital Bluetongue: Mild hydrocephalus, which could not easily be distinguished from the hydrancephaly associated with some cases of in utero BTV infection was reported to Animal Health. Brain was submitted for BTV PCR examination and a negative result obtained. The diagnosis was sporadic idiopathic hydrocephalus. Exotic pox virus infection: Very unusual, discrete, miliary, raised, plaque-like lesions about 1 cm diameter were found all over the body, particularly the head, neck and perineal areas, of a seven month old suckler calf. Histological examination showed focal epidermal necrosis with neutrophil infiltration but the aetiology was inconclusive and widespread consultation on possible aetiology could not rule out the possibility of an exotic, notifiable pox virus infection such as lumpy skin disease. Samples were submitted for detection of pox and other viruses. Despite a suspicion of the presence of pox DNA in an initial PCR (which was notified to DEFRA), no viruses were detected in the skin lesions. The cause remained unknown but the calf had listeria lesions in the brain and possibly the liver so an aberrant hypersensitivity response to bacterial infection is possible. Brucella surveillance Figure 3 The number of bovine submissions tested for brucellosis in GB: BS7, other Brucella and Total cattle submissions Quarter 1 2006 to 2010 2000 1750 Variable Other subs (cows) BS7 subs (cows) Total Submissions 1500 1250 1000 750 500 2006 2007 2008 2009 2010 BS7= statutory brucellosis testing; Other = samples from cows that had aborted, submitted for diagnostic testing, that were also tested for brucellosis This quarter has seen a small rise in BS7 submissions (955) compared with the first quarter of 2009 (912) after a continual fall since 2006. Four isolations of bacteria resembling Brucella were made from samples from aborting cows in Regional Laboratories this quarter. Examination of these at the VLA Weybridge Reference Laboratory revealed that none were brucellae. 5
The number of samples from aborted cows submitted for diagnostic testing that were also tested for brucellosis continues to rise, probably a reflection of the overall increase in cattle diagnostic submissions. Recently, a pamphlet has been produced by the VLA (in conjunction with Defra and Animal Health) and distributed to farmers, with the aim of encouraging the reporting of abortions in cattle (a statutory requirement) and the small rise in BS7 submissions this quarter may in part be attributed to this pamphlet. Investigatory and advisory farm visits VLA and SAC veterinarians visit farms at the request of private veterinary surgeons, to assist with the investigation of unusual, severe or difficult disease incidents. VLA veterinarians also visit for statutory purposes (for example under the Zoonoses Order to investigate outbreaks of salmonellosis) which are also included under the totals for England and Wales. From 2007, the VLA and SAC harmonised the way in which these more detailed investigations involving visits to farms are recorded. This is why comparable data is not available for previous years. Table 2 Farm investigation and advisory visits 1st Quarter Total Visits Dairy Beef Dairy and Beef Calf Rearer and Other E&W S E&W S E&W S E&W S E&W S 2010 28 5 6 1 11 4 2 0 9 0 2009 27 9 16 8 6 1 3 0 2 0 2008 47 9 30 5 12 4 3 0 2 0 2007 73 NA 47 NA 18 NA 6 NA 2 NA 2006 63 NA 28 NA 21 NA 10 NA 4 NA Chemical food safety incidents Table 3 Chemical food safety incidents 1st Quarter Total Incidents Botulism Lead Copper Metaldehyde Other E&W S E&W S E&W S E&W S E&W S E&W S 2010 8 0 0 0 7 0 1 0 0 0 0 0 2009 7 1 1 0 5 1 0 0 0 0 1 0 2008 16 1 4 0 10 1 0 0 0 0 2 0 2007 6 0 3 0 2 0 1 0 0 0 0 0 2006 9 3 2 0 3 2 2 0 0 0 2 1 Details of incidents investigated by the VLA are published in a quarterly newsletter which is available at: http://www.defra.gov.uk/vla/reports/rep_food.htm. The VLA has issued guidance to farmers in parts of the United Kingdom where soils contain large amounts of lead and provided specific actions to reduce the risk of lead toxicity to livestock (see the quarter 1 Chemical Food Safety Newsletter in the link above). 6
Lead poisoning incidents associated with feeding of silage contaminated with soil containing a high concentration of lead occurred on three occasions this quarter. The VLA advises farmers to be wary of purchasing cheap silage as it may be of poor quality, unsafe, or both. In one incident this quarter, fatal lead toxicity was diagnosed in two of a group of 36 suckler cows. Another group of 12 store cattle and a bull had nervous signs and some died or had to be euthanised and in total, 20 cattle died during this incident. A visit to the farm confirmed that the source of lead was soil-contaminated silage. Analysis of a silage sample containing soil was 30,537 ppm lead. Nine silage-exposed cattle were sampled at the visit and blood lead concentrations found to range from 1.5 to 3.4 µmol/l. The silage had been harvested by the farmer from land adjacent to old mines. The contaminated silage was removed from all groups of cattle and disposed of in accordance with the Local Authority guidance. The lead-exposed cattle have been placed under a 16 week voluntary restriction and will be re-sampled at the end of this period to check that blood lead concentrations have reduced satisfactorily. ENDEMIC DISEASE SURVEILLANCE A note about the disease trends charts. This section of the report gives information on occurrence of selected diseases. The data originate from submissions and are summarised and presented according to the diagnosis reached and assigned as a VIDA code. Our charts show the number of diagnoses (numerator) as a proportion of the number of submissions in which that diagnosis was possible (denominator), for all of GB, England & Wales and for Scotland. The bars indicate the 95% confidence limits. Note that the y-axis scale of the charts varies and therefore care must be taken when comparing individual charts. Fasciolosis Figure 4 There was an increase in the percentage diagnosis of fasciolosis in England and Wales for this quarter from 2007 to 2009, and the level has remained high for 2010. The percentage diagnosis has also remained high in Scotland from 2008 to 2010. The continued high rate of diagnosis of bovine fasciolosis is due to the effect of wet summers and mild winters, experienced in the years 2007 to 2009. The Meat Hygiene Service reported that 20% of cattle sent for slaughter had their liver condemned because of liver fluke damage during this quarter. Condemnation levels were over 20% for Wales and Scotland and nearly 18% for England. Despite increased awareness and publicity of the risk of infection, this indicates that more needs to be done to control infection through herd health planning. 7
Salmonellosis S. Dublin remains the most frequently isolated serovar of salmonella from cattle, contributing between two thirds to three quarters of the total. In this quarter, there was an increase in the number of isolations from Scotland, but the proportion of diagnoses is within the quite wide range seen in recent years (figure 5). Figure 5 This quarter saw a reversal in the decline in the number and proportion of GB diagnoses of S. Typhimurium that has occurred since 2006. However, the number and proportion of diagnoses of this serovar remain historically low (figure 6). Figure 6 8
The number and proportion of isolations of other salmonella serovars continues to increase, although not statistically significantly. Close monitoring of these other salmonellae is undertaken in order to detect possible newly emergent serovars (figure 7). Figure 7 There has been a small increase, from 10 to 12.5% of total bovine salmonella isolations, over the last two years, in this quarter, of S. Mbandaka. This feed-related strain is associated with animal feeds of vegetable origin, such as soya and rapeseed meal. Respiratory disease The first two months of the quarter were particularly cold and dry (see above). Despite this, there were no marked changes in the diagnoses of respiratory disease compared to previous first quarters. There was a non significant rise in IBR diagnoses but this was from a particularly low level in quarter 1 2009. RSV diagnoses continued at a low level in calves particularly in Scotland. Unusually, an outbreak of RSV was seen in first calf dairy heifers. The group showed an increased respiratory rate, pyrexia and emphysema was suspected. One died and post mortem examination showed emphysema in the caudal lobes and extensive consolidation in the cranio-ventral lung lobes. FAT and histopathology confirmed RSV and Mannheimia haemolytica was isolated from lung. It appeared that first calf heifers were being exposed to RSV on joining the milking herd. This is unusual as most cattle are exposed to RSV during the rearing period. During February, patent lungworm infestation was confirmed in a group of 16 housed yearling cattle that were coughing. Lungworm in youngstock in February is a rare diagnosis and is most likely to be a reflection of infection during the autumn when the weather was mild. UNUSUAL AND NEW DISEASES Bacillus pumilus mastitis Six milk samples were submitted for bacteriological culture as part of an investigation into high cell counts and some cases of clinical mastitis in a 100 cow Holstein Friesian dairy herd. One sample yielded a pure growth of Bacillus pumilus. The affected cow showed signs of systemic illness, had a high somatic cell count and two previous bouts of clinical mastitis that had appeared to respond to antibiotic treatment. Bacillus pumilus is a recognised cause of human food poisoning; it survives pasteurisation 9
and other heat treatments as spores. Evaluation of the toxigenic properties of Bacillus pumilus from mastitic milk were discussed by Nieminen et al (Toxigenic Bacillus pumilus and Bacillus licheniformis from mastitic milk, Veterinary Microbiology 124, 329-339). Bacillus sp. other than B. cereus and B. licheniformis are generally considered uncommon causes of bovine intramammary infection in GB. Unusual teat lesions in heifers associated with an automatic milking system Three heifers in a 230 cow dairy herd developed oval skin defects on the lateral aspect of two or more teats within 6 weeks of calving. Four milking robots had been installed 12 months previously. Udders had been singed 1 week before calving (which is later than usual practice) and it was thought that the recent singeing, combined with the roller brush action used in pre milking teat preparation had caused the lesions; severe self trauma, by persistent licking, may have aggravated the lesions further and prevented healing. Update on bovine neonatal pancytopenia (BNP) Between 01/01/10 and 12/5/10, there were 51 confirmed cases of BNP in GB. A further 26 cases are awaiting histological confirmation. A Defra-funded research project into the aetiology of this new disease is ongoing. One component of this study is a case-control study which will commence in the second quarter of 2010. Results of the Defra-funded investigations into BNP were presented at the AVTRW annual conference in April 2010 with 6 presentations, 5 of which were from the VLA. Update on bovine psoroptic mange Two further incidents of bovine psoroptic mange were identified in southern Wales in this quarter, bringing the total to 19 affected herds identified since incursion into GB, very probably in 2007. All affected herds identified by scanning surveillance are in southern Wales. As the disease is largely subclinical in the summer months, fewer diagnoses are expected in the second and third quarters of 2010, in which, however, there is a higher risk of silent spread. SCANNING SURVEILLANCE FOR NEW AND EMERGING DISEASES IN CATTLE Monitoring the trends in diagnoses of known diseases cannot, by definition, detect either new diseases or changes in endemic diseases that would prevent a diagnosis from being reached (for example a change in the pathogen that compromised the usual diagnostic test). Such new or emerging diseases are most likely to be detected by observation of increased numbers of clinical and/or pathological syndromes for which a diagnosis could not be reached in the normal way. Such submissions are regularly analysed to look for changes that could indicate the presence of a new or emerging disease, which may be reflected by an increase in undiagnosed disease. Undiagnosed disease submissions are summarised broadly by the clinical presentation of disease and, once determined by further investigation, the body system affected. Both groups are investigated and trends in the rates are compared over time. Summary In the first quarter of 2010, 24% of cattle submissions remained undiagnosed compared to 25% in the previous quarter (Q4 2009) and in the equivalent quarter of 2009. In Scotland, there was a statistically significant increase in undiagnosed bovine abortion. There was minimal indication of any new and emerging disease in the first quarter of 2010 from the review of undiagnosed submissions. 10
There was a decrease in undiagnosed cattle disease in the first quarter of 2010 when compared to the previous year s first quarter and in comparison with the final quarter of 2009. Disease patterns tend to be seasonal so comparison of equivalent time patterns is important. A summary of the changes, by body system, are shown in Table 4. Table 4 Percentage of undiagnosed bovine submissions in the first quarter of 2010, with comparisons with the first and fourth quarters of 2009. Body System Q1,2009 (%) Q1,2009 Q1,2010 Q1,2010 (%) Q4,2009 - Q1,2010 Q4,2009 (%) Circulatory 11 7 17 Enteric 22 = 22 24 Musculoskeletal 17 27 49 Nervous 20 7 22 Reproductive 48 53 48 Respiratory 12 10 21 Skin 22 16 19 Systemic and Miscellaneous 11 = 11 12 Urinary 7 = 7 6 Overall 25 24 25 = significant decrease; = significant increase; = non-significant decrease; = non-significant increase Reproductive disease: An increase in reproductive disease in GB was seen this quarter, from 48% to 53%. This increase was due to an increase in undiagnosed abortion in SAC cases, from 44% to 59%. There was a decrease in undiagnosed abortion from VLA cases. Abortion is the predominant clinical sign within reproductive disease accounting for 92% of SAC cases. Spring calving suckler abortions account for three quarters of the submissions, but the increase in undiagnosed submissions within this category was only 1%. There was an increase in undiagnosed dairy abortions and in the category unknown. The increase in abortion was predominantly from two SAC centres, Auchincruive and Thurso, which are geographically unrelated. The causes of abortion in cattle are diverse, many non infectious. This body system will be monitored closely in future quarters. Figure 8 Undiagnosed abortions in GB cattle in 2010 compared to previous years Solid line is the % of DNR in 2010; dotted line is the % of DNR in previous years. 11
HORIZON SCANNING Bovine besnoitiosis has been classified as an emerging disease within the European Union. Besnoitiosis is a protozoal disease of cattle which presents in a severe acute systemic form associated with proliferation of endozoites in blood vessels and a chronic form associated with cyst formation. It tends to be seasonal, with highest prevalence in the summer, probably related to arthropod vector activity. No treatment is available at the present time. An information document is being produced by VLA to raise awareness, which is required for prompt diagnosis, should the disease spread to GB. An increase in prevalence and severity of paramphistomiasis (rumen fluke) has been reported both in GB and in Eire. Outbreaks in Ireland have been in both cattle and sheep, with the latter more severely affected. The intermediate host is a water snail and the increase in cases is very probably associated with recent wet summers. This condition is currently being recorded within the diagnoses not listed group for enteric disease. For VLA submissions, it accounted for 11% (7/61) of these diagnoses in this quarter. The emergence and changing trends in parasitic disease give some forewarning of the potential problems to the environment and to animal health and welfare caused by a changing climate. A negative economic effect on the livestock industry is a possible consequence. Bluetongue is considered a continuing risk to GB in 2010, including the risk of new incursions from wind-borne infected midges. Livestock holders should not be complacent and should be encouraged to remain vigilant for disease and to continue vaccinating their livestock. 12