The prevalence and distribution of sheep scab in Wales

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1 The prevalence and distribution of sheep scab in Wales Richard Wall 1, Charlotte Chivers 1, Eric Morgan 2 & Hannah Rose 2 1 School of Biological Sciences and 2 School of Veterinary Science, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol, BS8 1TQ 1. Introduction The management of psoroptic mange (scab) in sheep over the last forty years has proved to be a particularly intractable problem in the UK. Even when compulsory plunge dipping was imposed, scab could not be eradicated (French et al., 1999). Deregulation of scab in 1992 was then followed by an almost exponential increase in disease incidence, with the number of outbreaks increasing from less than 100 per year to an estimated 7000 outbreaks per year in 2003/04 (Bisdorff & Wall, 2008). In a retrospective questionnaire survey of 1067 farmers in the UK in 2003/2004, overall 9% (± 1.72) of farmers reported at least one outbreak of scab between March 2003 and February 2004, but there was strong regional variation in this prevalence. The proportion of farms with at least one outbreak of scab was highest in Wales (17%), followed by Scotland (14%) and Northern England (11%). The percentage of farms affected in England was substantially lower and similar in all four regions, at between 3 per cent and 6 per cent (Bisdorff, Milnes & Wall, 2006). Further questionnaire surveys have supported this strongly regional pattern with a particularly high prevalence of scab in Wales; a prevalence of 8.6% was reported by Rose et al., (2009) for Great Britain, with a prevalence in Wales of 24.2%. A study by Cross et al. (2010) reported that 36.5% of sheep farmers in Wales had had at least one outbreak of scab over a 5 year period. Scab was estimated to cost the UK sheep industry between 8 and 14 million per year in 2005, with the costs of insecticide applications far exceeding the economic losses associated with mortality and reduced weight gain (Nieuwhof & Bishop, 2005), although this study is now somewhat dated. Scab is of course at least equally important as a major animal welfare issue, causing pruritus, excoriation and selftrauma. Scab control is now largely dependent on macrocyclic lactones (MLs), the overuse of which is likely to contribute to the development of ML resistance in a wide range of sheep parasites. Despite a number of recent education campaigns, little apparent progress has been made towards identifying the best approach to scab management or implementation. Nevertheless, the appropriate management of scab is essential on both welfare and economic grounds. Identifying the most appropriate manner in which future efforts should be focussed, however, is difficult. Scab has been shown to be highly localised on some farms, which are likely to report persistent outbreaks over several years; 85% of farms reporting a scab outbreak in 2007/08 also reported having one or more outbreaks each year in the previous ten years. In contrast, 76% of farms that had no scab in 2007/08 had not had scab in the previous ten years (Rose et al., 2009). This suggests that there are likely to be specific management or environmental risk factors which distinguish the farms on which persistent scab is reported. Poor fencing and bought in sheep were identified as important risk factors for scab in Ireland by O Brien (1992), who suggested that upland and mountain sheep, remained the primary focus of infection. This was confirmed by Rose & Wall (2012) who showed that farms using 1

2 common grazing were at significantly higher risk of infestation than farms not using common grazing, as were farms that had direct contact with neighbours sheep and that had neighbours with scab. The aim of the current study was to provide up to date information about the prevalence and distribution of scab in Wales as a preparatory step towards undertaking a regional scab management programme. 2. Methods A retrospective questionnaire was prepared in both English and Welsh (appended). A printed questionnaire was circulated to approximately 7500 members of the Welsh Lamb and Beef Producers Association. Online versions of the questionnaire were advertised via a number of sources. Respondents were initially asked if they had experienced a scab outbreak in Those that said that they had had an outbreak in 2015 continued to questions 2-5 for elaboration. Those that did not report having an outbreak in 2015 were directed onto question 6. All respondents were then asked about bought-in sheep, scab preventative methods, scab prevalence in the last 10 years, and for the type(s) of land/grazing they use on their farms. Farm postcodes were used to map the distribution of scab outbreaks. Data from returned surveys were entered into a Microsoft Excel spreadsheet. Chi-squared analysis was used to compare subsets of respondents, and Q-GIS was used to map the distribution of scab outbreaks. Note, denominators are not always the same for each question, because not every respondent completed every question. 2

3 3. Results A total of 982 questionnaires were received by the deadline of 1 st April Almost all of these came from the membership of WLBP. Very few farmers responded as a result of the online information or online surveys and most of these were received after the cut-off date and so were not included in the analysis. Ten of the returned questionnaires were blank or incomplete and so were excluded. Hence, 972 informative completed surveys remained, giving a response rate of approximately 14% (correcting for around 600 WLBP members which were dairy-only). Question 1 (Scab prevalence 1 since January 2015) 16% (n=154) of respondents reported having at least one scab outbreak since January There were 180 outbreaks in total, as 26 farms reported more than one outbreak of scab during this period. Respondents were well distributed geographically, (Figures 1A,and 1B). However, further spatial statistical analysis would be required to identify areas of high regional prevalence, taking into account the underlying distribution of farms. A B Figure 1: The distribution of farms that reported that they (A; left) had, or (B; right) did not have, an outbreak of scab between since January 2015 and February Prevalence is defined as the proportion of the population with disease at a given time, in this case the proportion of respondents that had scab at any point in

4 Number of scab outbreaks Feb 2017 Question 2 (Monthly incidence 2 ) Respondents reported the highest incidence of sheep scab outbreaks in 2015 in November and January (Figure 2), with the majority of cases falling between September and January (83%, n=150). The average duration of scab outbreaks reported in 2015 was 2 months Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Month (2015) Figure 2: Reported scab outbreaks in 2015 by month (n=181). If farms reported more than one month where scab was first detected, both months are included Question 3 (Product used to treat scab in 2015/number of doses) On average, a mean of 1.63 (± 1.36 SD) doses of treatment were used to treat scab outbreaks. Dectomax was used by 38% (n=52) of the 137 farms that provided information on the treatment used; 28% used Cydectin (n=38) (Table 1). Multiple treatments were used by 15% (n=20) of farms with scab infestations and two individuals reported using 6 and 10 doses to treat and outbreak. Some of these multiple doses can be attributed in part to the subset of respondents that use ivermectin, who reported using a mean of 2.06 (± 1.38 SD) doses to treat an outbreak. Two doses of ivermectin are required for the treatment of sheep scab and therefore these data suggest that overall the farmers are using products in accordance with manufacturer s guidelines. 2 Incidence is defined as the proportion of the population with new cases of disease within a given time period. In this case this is the number of cases reported by respondents in each month, divided by the total respondents reporting scab in Note that some farms reported more than one case in

5 Number of farms Feb Number of doses Figure 3: The number of doses of treatment that respondents reported using to treat scab outbreaks (n=68). Table 1: Scab treatments, trade name and acaricidal compound, used by farms that treated a scab outbreak in Product name Active ingredient % (n) of farms Dips (various) Diazinon (OP) 13.3% (21) Dectomax Doramectin 32.9% (52) Cydectin/Zermex Moxidectin 32.3% (51) Ivermectin, Ivomec, Paramectin, Premadex, Ivermectin 20.3% (32) Noramectin, Bimectin 1, Qualimec Crovect 1 Cypermethrin (SP) 0.6% (1) Other (spot-on or herbal) 1 0.6% (1) Total N = 158 Note: 1 no label claim for scab (Summary of Product Characteristics obtained from the Veterinary Medicines Directorate Product Information Database). For products containing ivermectin, doramectin and moxidectin, it was assumed that the farmer used the injectable formulation. Question 4 (Effectiveness of scab treatment) Only, 9.3% (n=14) of farmers reported that the treatments they used were ineffective. Question 5 (Scab confirmed) Confirmation of the diagnosis of psoroptic mange by a veterinarian was obtained by 27% (n=41) of farms that reported having scab in 2015, and 4% (n=6) had it confirmed by an alternative health professional. The diagnosis of scab was not confirmed by an independent expert by 69% (n=106) of farmers who had an outbreak in

6 Question 6 (Quarantine bought in sheep and product(s) used) Of the 906 respondents who said that they bought in sheep 29% (n=262) said that they did not quarantine the introduced animals. Furthermore, 58% (n=526) did not use any preventative treatments on bought in sheep. Just 347 of the farms reported the type of treatment they use to treat bought in animals; the most widely used product was Doramectin, followed by Cydectin (Table 2). 13% said that they used various OP dips, 32 farmers said that they used Crovect, which has no label claim for the prevention of scab. Many farmers claimed to use multiple products, indicating that, although the questionnaire was specifically about scab, the responses relating to treatment for bought in animals was broadly interpreted to cover all parasite treatments. Table 2: The products used on bought in sheep. 347 farms provided treatments they use, with 368 treatments due to farms using multiple treatments. Product name Active ingredient % (n) of farms Dips (various) Diazinon (OP) 12.2% (45) Dectomax Doramectin 32.1% (118) Cydectin/Zermex Moxidectin 21.7% (80) Ivermectin, Ivomec, Paramectin, Ivermectin 10.9% (40) Noromectin, Qualimec, Premadex Bimectin 1 Ivermectin 3.5% (13) Crovect 1 /Vectocert 1 Cypermethrin 8.9% (33) Clik 1 Dicyclanil 0.8% (3) Dysect 1 /Ectofly 1 /Zermasect 1 Alphacypermethrin 1.9% (7) Combinex 1 /Nilverm LA 1 Levamisole 0.5% (2) Covexin 8 1 Clostridial Vaccination 0.3% (1) Closamectin 2 Ivermectin and closantel 0.3% (1) Closantel 1 Closantel (anthelmintic) 0.3% (1) Injection (unknown)? 2.2% (8) Spot on (unknown)? 1.4% (5) Pour on (unknown)? 0.3% (1) Spray (unknown)? 0.5% (2) Other (unknown)? 2.2% (8) Total N=368 Note: 1 no label claim for scab (Summary of Product Characteristics obtained from the Veterinary Medicines Directorate Product Information Database). For products containing ivermectin, doramectin and moxidectin, it was assumed that the farmer used the injectable formulation. 2 Closamectin can be used for the treatment of scab if followed by a second dose of ivermectin 7 days later. However it is unclear if this was the case and therefore Closamectin is considered unsuitable in this instance. Question 7 (Scab prevention) 47% (n=453) of farms said they currently use at least one type of scab preventative treatment. Dipping was the most popular method of prevention (44%, n=199), followed by Dectomax (20%, n=92) (Table 3). Farms that use preventative measures treat their flock on average once a year (mean =1.34± 0.61). 6

7 Table 3: The treatments used by farms which used preventative treatments against scab. 432 farms provided information on the treatments they use, with 31 farms reporting the use of multiple treatments. Scab preventative treatment Active ingredient % (n) of farms Dips (various) Diazinon (OP) 40.8% (189) Dectomax Doramectin 20.3% (94) Cydectin/Zermex Moxidectin 17.3% (80) Ivermectin, Paramectin, Bimectin 1, Qualimec, Ivomec, Premadex Ivermectin 11.7% (52) Closamectin 2 Ivermectin, closantel 0.4%(2) Crovect 1 SP 4.5% (21) Ectofly 1 Cypermethrin 0.2% (1) Spot on 1 Deltamethrin 0.6% (3) Clik Dicyclanil 0.6% (3) Vetrazin 1 Cyromazine 0.2% (1) Scabivax 1 Vaccine 0.2% (1) Pour on (unknown)? 0.4% (2) Contractor (unknown)? 0.2% (1) Injection (unknown)? 1.5% (7) Other unknown? 1.3% (6) Total N=463 Notes: 1 no label claim for scab (Summary of Product Characteristics obtained from the Veterinary Medicines Directorate Product Information Database). For products containing ivermectin, doramectin and moxidectin, it was assumed that the farmer used the injectable formulation. 2 Closamectin can be used for the treatment of scab if followed by a second dose of ivermectin 7 days later. However it is unclear if this was the case and therefore Closamectin is considered unsuitable in this instance. Question 8 (Scab in the last 10 years) 690 farmers reported that they had not had a scab outbreak over the last 10 years (Figure 4). 29% (n=282) had had at least one outbreak, with affected farms suffering on average two outbreaks in the last decade. Notably 23 farmers had experienced between 6 and 10 outbreaks. Of the 154 farms that reported scab in 2015, 70% (n=108) also had scab in the last 10 years. Farms with scab in 2015 were significantly more likely to have had an outbreak in the previous 10 years than farms that did not have scab in 2015 (χ 2 = 106.6, n = 972 P = <0.01). 93% (n=944) of farms that didn't have scab in 2015 said that they had had no outbreaks in the last 10 years. 7

8 Number of farms Feb Number of years with outbreaks Figure 4. Number of farmers reporting outbreaks over the last 10 years. A B Figure 5: The distribution of farms that reported that they (A) had, or (B) did not have, an outbreak of scab in the previous 10 years. Farmers who said that that they used scab prevention were significantly more likely to have suffered from a scab outbreak in 2015 (20%, n=91) than farms not using prevention (12%, n=63) (χ 2 =6.12, n= 972, 8

9 Number of farms Feb 2017 P=0.0134) (Figure 4). However, farmers who said that they used scab prevention in 2015 were less likely to have had an outbreak in the last 10 years (χ 2 = 8.75, n = 972, P=0.003). Question 9 (Lice) 53.3% of farms reported that they had seen lice in their flock on at least one occasion in the past 10 years (Figure 6) Number of years with lice Figure 6: Number of farms with lice presence in the last 10 years (n=469). Question 10 (Flock size) 942 farms provided their flock sizes. The average total flock size (including ewes, rams, lambs, and 'other') was 1105, with an average ewe flock size of 483 (Figure 7). 9

10 Number of farms Feb Flock size Figure 7: Reported sheep flock sizes (n=942) Large flocks had significantly more reported scab outbreaks in 2015 than smaller flocks (χ 2 =41.91, n=942, P = <0.001; Table 4), with just 8% (n=26) of flocks of sheep experiencing an outbreak. Similarly, larger flocks were significantly more likely to have had scab in the last 10 years (χ 2 =52.5, n=942, P=<0.001; Table 4). Furthermore, farms that had scab every year for the last 10 years were significantly more likely to be larger flocks than smaller flocks (χ 2 =71.5, n=942, P=<0.001). Table 4: Flock size compared with reported scab prevalence. Flock size (n) % (n) with scab in 2015 % (n) with scab in the last 10 years (312) 8.3% (26) 15.4% (48) 0% (0) (221) 17% (37) 30.3% (67) 1.4% (3) (371) 19.1% (71) 39% (144) 2.4% (9) (30) 30% (9) 43.3% (13) 3.3% (1) (8) 75% (6) 63% (5) 38% (3) % (n) with scab every year Question 11/12 (Type of land/postcode) 907 of the respondent farms answered this question: 66.3% indicated that they were hill or upland farms, 29% said that they were lowland and 5.2% of farms said they used both types of grazing. 771 respondents provided their post codes, allowing the mapping in figures 1 and 5 to be carried out. Question 13 (Common Grazing) Common grazing was used by 17% (n=170) of the farms that responded to the questionnaire. 10

11 Farms that used common grazing were significantly more likely to have had scab in 2015 (χ 2 =10.01, n = 972, P=0.002); 27% (n=42) of the farms that used common grazing had scab in 2015 whereas just 14% (n=114) of farms without common grazing have had scab (Fig. 11). Farmers who used common grazing were also more likely to have had scab in the past 10 years than farmers who did not common graze (χ 2 =35.3, n = 972, P=0.02). 35.3% of farmers who common grazed had 1-5 outbreaks in the last 10 years, whereas 7.1% of farmers who common grazed had 6-10 outbreaks in the last 10 years. Telephone follow up The question of whether telephone follow-up should be undertaken has been raised a number of times. Telephone surveys are problematic and it is very difficult to get meaningful data from them; telephone surveys need to be very well designed, usually as part of case control studies, to avoid just picking up random anecdote and need to be carried out on an appropriately large and statistically meaningful scale. It is not something that can be readily or meaningfully included as part of this study. 4. Conclusions This survey was completed by 14% of the potential participants who received the questionnaire by post. Previous studies have achieved higher response rates (Bisdorff et al 2006; Bisdorff and Wall 2008; Rose et al 2009). The relatively low response rate in the present study could relate to its timing; the survey was distributed during the spring lambing season. 16% (n=154) of respondents reported having at least one scab outbreak since January This prevalence figure is almost identical to previous questionnaire studies in Wales, for example by Bisdorff, Milnes & Wall (2006), but is lower than that found by Rose et al. (2009) and considerably lower than that reported by Cross et al. (2010). The current prevalence estimate is likely to be conservative as most of the sample population (WLBP members) are members of Farm Assurance schemes and, on the whole, are likely to manage their flock to a higher standard than farmers who are not members. At the very least, the study suggests that although the prevalence of scab in Wales is higher than the UK national average, but it does not appear to be continuing to increase. The majority of outbreaks occurred between September and January, which is what would be expected (French et al., 1999; Rose et al., 2009). Various reasons have been suggested to explain the high winter prevalence of scab, including poorer body condition associated with more limited feed and gestation, concentrations of overwintering sheep, effects of fleece length on the growth of mite populations and autumn sheep sales (French et al., 1999; van den Broek and Huntley, 2003). The distribution map shows that outbreaks of scab in 2015 were widely dispersed. The distribution map for scab outbreaks in the last 10 years suggests that Powys and coastal areas of northern Ceredigion and southern Gwynedd have been worst affected by scab in the last decade, although the pattern is still relatively well dispersed and further spatial statistical analysis is required to identify localised hotspots of persistent scab. Many of the regions affected by scab are in upland areas. Farmers who used common grazing were more likely to experience scab in 2015; a similar result was reported by Rose and Wall (2012), who showed that common grazing was a critical risk factor, with farms that used commons almost twice as likely to have scab as farms that did not. 11

12 It is of interest that 69% of farms did not have their scab outbreaks confirmed. Infestation by lice may cause similar clinical signs to scab, and confusion may not be uncommon. Bisdorff and Wall (2008), found that 44% of farmers treated to prevent scab; the current study found a similar percentage using preventative treatment (47%). Notably, 58% of farmers said that they did not use a preventative treatment on their introduced sheep. Most used only one dose to treat established scab outbreaks and most said that the treatment was effective. However, a key finding from this study is the apparent confusion among a relatively large group of farmers about which products are suitable for the prevention or treatment of scab. This highlights the need for clearer education and training, particularly since the participants, who were members of the Welsh Livestock Beef Producers Association, might be expected to be a group who were particularly well informed and committed to good husbandry. Critically, the data show that there is that a cohort of farmers who experience repeat outbreaks year after year, whereas the majority of sheep farmers (71%) had not had scab in the last 10 years. A similar finding was reported by Rose and Wall (2012) for Great Britain. This is an important point because it highlights the fact that control and management efforts can be focussed on a relatively small group of farms and farming systems to maximise its cost-effectiveness. Further work should be undertaken to refine our understanding of scab hotspots and help in identifying areas for localised scab interventions. Acknowledgements The authors would like to thank WLBP for their valuable contribution to helping to distribute the survey and its members for responding. References Bisdorff, B., Milnes, A., Wall, R., (2006). Prevalence and regional distribution of scab, lice and strike in Great Britain. Veterinary Record. 158, blowfly Bisdorff, B., Wall, R., (2008). Control and management of sheep mange and pediculosis in Great Britain. Veterinary Parasitology. 155, Cross, P., Edwards-Jiones, G., Omed, H. & Prysor-Williams, A. (2010) Use of a randomised response technique to obtain sensitive information on animal disease prevalence. Preventative Veterinary Medicine, 96, French, N.P., Berriatua, E., Wall, R., Smith, K., Morgan, K.L., (1999). Sheep scab outbreaks in Great Britain between 1973 and 1992: spatial and temporal patterns. Veterinary Parasitology. 83, O'Brien, D.J., (1992). Studies on the epidemiology of psoroptic mange of sheep in Ireland. University College Dublin. Rose, H., Learmount, J., Taylor, M., Wall, R., (2009). Mapping risk foci for endemic sheep scab. Veterinary Parasitology. 165, Rose, H., Wall, R., (2012). Endemic sheep scab: Risk factors and the behaviour of upland sheep flocks. Preventative veterinary medicine. 104, Van Den Broek, A.H., Huntley, J.F., (2003). Sheep scab: the disease, pathogenesis, and control. J. Comp. Path. 128,

13 2016 Wales Sheep Scab Survey This survey will be used only to help inform scab control policy in Wales; all information will be treated as strictly confidential and will not be used for any other purpose; this research is not funded by any pharmaceutical company. 1. Have you had an outbreak of sheep scab since 1 January 2015? (please circle your answer) If YES go to question 2, If NO go to question 6 2. Please circle all months when you saw signs of scab in your flock 2015 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec 3. What product(s) did you use to treat the scab outbreaks, and how many doses were given? 4. Were the treatments effective (Please tick) YES NO 5. Were any of the outbreaks since 1 January 2015 confirmed as scab by a vet or Veterinary Lab? YES, Vet/veterinary laboratory YES (other) NO 6. Do you quarantine bought-in sheep in case they have scab? YES NO Do you apply any product to bought in sheep? YES NO If Yes, which? 7. Do you routinely treat your animals to prevent scab? YES (which product do you use? & how many times a year? ) NO 8. Have you had scab in the previous 10 years? (please circle) Have your sheep ever had lice? YES If yes when (give years) NO 10. How many sheep did you have on your farm in June 2015? Ewes Lambs Rams Other 11. Are you a hill / upland / lowland farm (please circle as appropriate); what is your postcode 13

14 12. Do you use common grazing? YES NO 13. Would you be willing to allow us to contact you or visit to ask further questions about scab? If YES please include your phone number or address Thank you very much for participating. Please return this in the pre-paid envelope. 14

15 Supplementary spatial analysis of the 2015 survey data Key results Two areas of high regional prevalence were identified: o Powys, centred around Brecon o North Gwynedd, centred around Bangor Respondents of the 2015 Welsh Government/University of Bristol sheep scab survey were asked to report the presence or absence of sheep scab outbreaks on their holding during 2015 and in the previous 10 years. The distribution of respondents was not homogenous. Respondent density was highest in the central Powys region bordering England (Figure 1). Further analysis using the G statistic confirmed significant clustering of respondents and departure from complete spatial randomness (Figure 2). Therefore, the presence of regions of high prevalence that could be targeted in the early stages of scab control initiatives required further spatial analysis. Figure 1. The density of respondents to the 2015 sheep scab survey determined using kernel density estimation. Warmer colours (yellow) indicates a higher density and cooler colours (blue) indicates a lower density. 15

16 Figure 2. The expected G function for respondents assuming complete spatial randomness (mean red line, confidence envelope grey area). The observed distribution (black line) is significantly higher than expected, confirming significant spatial clustering of respondents. A kernel density method using a quartic kernel and adaptive bandwidth was used to estimate the spatial density of respondents reporting sheep scab in 2015 and respondents reporting no outbreak in The distribution of respondents reporting no outbreak was similar to the overall distribution of respondents. However, the distribution of respondents reporting at least one outbreak in 2015 appeared to differ significantly. The ratio of the two density estimates (the odds ratio) was then used to estimate the probability distribution of sheep scab in Wales in 2015 (Figure 3). Significant clusters centred near Bangor and Brecon were apparent. These clusters, as well as two other minor clusters, were confirmed using a SatScan Bernoulli model, which identifies regions where the number of reported outbreaks is higher than expected. 16

17 Figure 3. The probability distribution of reporting a scab outbreak in 2015, estimated from the odds ratio of kernel density estimates for reported cases and controls in the 2015 sheep scab survey. Warmer colours (yellow) indicate a higher probability, cooler colours (blue) indicate a lower probability. Black circles indicate clusters identified using SatScan software, where the number of reported cases was higher than expected. The above analysis was repeated using the respondents reports of scab outbreaks in 2015 and the preceding 10 years. In this analysis the number of years that respondents reported outbreaks during this 11-year period was taken into account to estimate weighted probability distribution and SatScan clusters. Therefore the following results integrate both the spatial distribution and frequency of sheep scab outbreaks. These analyses identified similar areas of high risk to the analysis based on 2015 data only (Figure 4). Based on the probability distribution, the same high risk regions around Brecon and Bangor were apparent. SatScan clusters identified wider areas of high risk than those based on the 2015 data alone. However, Powys and north Gwynedd were consistently high risk. 17

18 Figure 4. The probability distribution of reporting a scab outbreak between 2005 and 2015, weighted for the reported frequency of outbreaks, estimated from the odds ratio of kernel density estimates for reported cases and controls in the 2015 sheep scab survey. Warmer colours (yellow) indicate a higher probability, cooler colours (blue) indicate a lower probability. Black circles indicate clusters identified using SatScan software, where the number of reported cases was higher than expected. 18