Downloaded from veterinaryrecord.bmj.com on June 27, 2014 - Published by group.bmj.com
Paper
Paper Angiostrongylus vasorum in UK mainland: a nationwide postal questionnaire survey of veterinary practices L. Kirk, G. Limon, F. J. Guitian, C. Hermosilla, M. T. Fox The lungworm, Angiostrongylus vasorum, was first reported in indigenous dogs in southwestern England in 1980 and has since been recorded in Wales, southeastern England and, more recently, in the West Midlands, northern England and Scotland. The nationwide distribution of the parasite was evaluated using a postal questionnaire sent to 3950 small animal practices during 2009. Information was sought on the location of each practice, awareness of the parasite locally, number of cases diagnosed over the past year and whether diagnosis was based on clinical signs alone or supported by additional tests. 1419 practices returned a usable response, the majority being located in a city/town. Nearly one-third of responding practices were aware of the parasite locally, 20.7 per cent had seen at least one confirmed case and 0.3 per cent >20 confirmed cases over the past year. The most widely used tests were faecal examination and any type of imaging. Existing clusters of infection were detected in southeastern England and south Wales; infection was also found to be widespread in central England, though patchy in northern England and Scotland. Using distribution of clinical cases as an indicator of parasite distribution, this study confirmed that A. vasorum has spread beyond traditional UK endemic foci.
Introduction
Infection with the metastrongyloid nematode, Angiostrongylus vasorum, may be associated with one of a number of clinical syndromes that include cardiorespiratory signs, coagulopathies and neurological dysfunction (Morgan and others 2005). The parasite was first reported in the UK in an imported greyhound in Hertfordshire in 1975 (Jacobs and Prole 1975) and then in breeding kennels in Cornwall in southwestern England five years later (Simpson and Neal 1982). Over the following two decades, many more cases were recorded in Wales (Patteson and others 1987, Trees 1987) and southeastern England (Chapman and others 2004). A survey of nematode parasites of wild foxes in England later and more recently in Scotland suggested that the parasite may be spreading further north (Morgan and others 2008, Philbey and Delgado, 2013), and this was supported by a report of five fatal cases of A. vasorum infection in dogs from northern England and the West Midlands (Yamakawa and others 2009), a case in Glasgow (Helm and others 2009) and a laboratory study using serum samples from dogs with a range of conditions across the UK (Schnyder and others 2013a). Yet despite the increasing number of reports of canine Veterinary Record (2014) L. Kirk, BVetMed MRCVS, G. Limon, MVZ MSc, F. J. Guitian, LV PhD FHEA DiplECVPH, M. T. Fox, BVetMed PhD DiplEVPC FHEA MRCVS, The Royal Veterinary College, University of London, Hawkshead Lane, North Mymms, Hertfordshire AL9 7TA, UK C. Hermosilla, DVM Dr.med.vet. Dr.habil. DipEVPC, The Institute of Parasitology, Justus
doi: 10.1136/vr.102196 Liebig University Giessen, Giessen 35392, Germany; E-mail for correspondence: [email protected] Provenance: not commissioned; externally peer reviewed Accepted May 1, 2014; A scientific paper for submission to The Veterinary Record
angiostrongylosis at a regional level, there has as yet been no attempt to establish the distribution of infection in dogs on a nationwide scale and formally assess potential clustering of cases. The present study was therefore designed to establish both the geographical distribution and the frequency of clinically infected dogs seen nationwide by means of a postal questionnaire survey of small animal veterinary practices. Alternative approaches to generating such data were considered, such as faecal examination and serological screening, though discounted on grounds of the number of individual animals that would have to be sampled to obtain a representative picture, coupled with the time, technical staff support, cost and regulatory requirements in the latter case.
Materials and methods Postal questionnaire
A letter was published in the Veterinary Record describing the aims and methodology of the forthcoming survey and soliciting the support of colleagues in small animal practices registered with the Royal College of Veterinary Surgeons (Ashley and others 2009). Questionnaires were then posted to individual practices and accompanied by an addressed, prepaid reply envelope. The questionnaires sought information on (i) the practice location (urban, suburban, rural); (ii) whether cases of infection with A. vasorum in dogs had been seen by the practice over the previous 12 months; (iii) whether diagnosis had been made on clinical grounds alone or confirmed by additional test(s) and, if the latter, what tests had been employed; (iv) whether the practice was aware of A. vasorum occurring locally, that is, within a 5-mile (8 km) radius; (v) how many confirmed cases of canine angiostrongylosis had been seen by the practice over the previous 12 months and (vi) at what time of year most cases had been seen by the practice. Practices were given one month within which to reply to the questionnaire. Nonresponding practices, which had e-mail addresses, were then sent three e-mail reminders at weekly intervals, and persistent non-responders, 10.1136/vr.102196 | Veterinary Record | 1 of 6
Downloaded from veterinaryrecord.bmj.com on June 27, 2014 - Published by group.bmj.com
Paper coupled with those practices without an e-mail address, were sent a second postal questionnaire one month later.
TABLE 1: Number and percentage of practices responding per region compared with those sent the questionnaire
Data analysis
Region
Descriptive statistics were obtained for variables representing the location of the practice (urban v suburban v rural), awareness of the presence of A. vasorum in the area, the number of cases diagnosed (clinically or with an additional test) and the type of diagnostic test employed. To visualise the geographical distribution of practices that had seen cases of A. vasorum infection in dogs, confirmed by additional diagnostic test(s) during the 12 months prior to the date of the survey, choropleth maps were created using Arc GIS 9.2 (ESRI 2006). The maps represented, for practices located in the same county, (i) the risk of seeing at least one confirmed case and (ii) the risk of seeing more than five confirmed cases. Smoothed maps representing Bayes standardised risk were obtained in GeoDa 0.9.5-i5 (https://geodacenter.asu. edu/software), a weight matrix based on queen continuity; first-order adjacency was defined. The spatial scan statistic was used to identify significant clusters of practices with a high probability of (i) seeing at least one confirmed case of A. vasorum infection in the previous 12 months and (ii) seeing at least six confirmed cases of A. vasorum infection in the previous 12 months. It was implemented in SaTScan V.8.1.1 (www.satscan. org) using a Bernoulli probability model, a circular window set to contain a maximum of 50 per cent of the population at risk, and Monte Carlo randomisation with 999 permutations, clusters for which P
Paper
Paper Angiostrongylus vasorum in UK mainland: a nationwide postal questionnaire survey of veterinary practices L. Kirk, G. Limon, F. J. Guitian, C. Hermosilla, M. T. Fox The lungworm, Angiostrongylus vasorum, was first reported in indigenous dogs in southwestern England in 1980 and has since been recorded in Wales, southeastern England and, more recently, in the West Midlands, northern England and Scotland. The nationwide distribution of the parasite was evaluated using a postal questionnaire sent to 3950 small animal practices during 2009. Information was sought on the location of each practice, awareness of the parasite locally, number of cases diagnosed over the past year and whether diagnosis was based on clinical signs alone or supported by additional tests. 1419 practices returned a usable response, the majority being located in a city/town. Nearly one-third of responding practices were aware of the parasite locally, 20.7 per cent had seen at least one confirmed case and 0.3 per cent >20 confirmed cases over the past year. The most widely used tests were faecal examination and any type of imaging. Existing clusters of infection were detected in southeastern England and south Wales; infection was also found to be widespread in central England, though patchy in northern England and Scotland. Using distribution of clinical cases as an indicator of parasite distribution, this study confirmed that A. vasorum has spread beyond traditional UK endemic foci.
Introduction
Infection with the metastrongyloid nematode, Angiostrongylus vasorum, may be associated with one of a number of clinical syndromes that include cardiorespiratory signs, coagulopathies and neurological dysfunction (Morgan and others 2005). The parasite was first reported in the UK in an imported greyhound in Hertfordshire in 1975 (Jacobs and Prole 1975) and then in breeding kennels in Cornwall in southwestern England five years later (Simpson and Neal 1982). Over the following two decades, many more cases were recorded in Wales (Patteson and others 1987, Trees 1987) and southeastern England (Chapman and others 2004). A survey of nematode parasites of wild foxes in England later and more recently in Scotland suggested that the parasite may be spreading further north (Morgan and others 2008, Philbey and Delgado, 2013), and this was supported by a report of five fatal cases of A. vasorum infection in dogs from northern England and the West Midlands (Yamakawa and others 2009), a case in Glasgow (Helm and others 2009) and a laboratory study using serum samples from dogs with a range of conditions across the UK (Schnyder and others 2013a). Yet despite the increasing number of reports of canine Veterinary Record (2014) L. Kirk, BVetMed MRCVS, G. Limon, MVZ MSc, F. J. Guitian, LV PhD FHEA DiplECVPH, M. T. Fox, BVetMed PhD DiplEVPC FHEA MRCVS, The Royal Veterinary College, University of London, Hawkshead Lane, North Mymms, Hertfordshire AL9 7TA, UK C. Hermosilla, DVM Dr.med.vet. Dr.habil. DipEVPC, The Institute of Parasitology, Justus
doi: 10.1136/vr.102196 Liebig University Giessen, Giessen 35392, Germany; E-mail for correspondence: [email protected] Provenance: not commissioned; externally peer reviewed Accepted May 1, 2014; A scientific paper for submission to The Veterinary Record
angiostrongylosis at a regional level, there has as yet been no attempt to establish the distribution of infection in dogs on a nationwide scale and formally assess potential clustering of cases. The present study was therefore designed to establish both the geographical distribution and the frequency of clinically infected dogs seen nationwide by means of a postal questionnaire survey of small animal veterinary practices. Alternative approaches to generating such data were considered, such as faecal examination and serological screening, though discounted on grounds of the number of individual animals that would have to be sampled to obtain a representative picture, coupled with the time, technical staff support, cost and regulatory requirements in the latter case.
Materials and methods Postal questionnaire
A letter was published in the Veterinary Record describing the aims and methodology of the forthcoming survey and soliciting the support of colleagues in small animal practices registered with the Royal College of Veterinary Surgeons (Ashley and others 2009). Questionnaires were then posted to individual practices and accompanied by an addressed, prepaid reply envelope. The questionnaires sought information on (i) the practice location (urban, suburban, rural); (ii) whether cases of infection with A. vasorum in dogs had been seen by the practice over the previous 12 months; (iii) whether diagnosis had been made on clinical grounds alone or confirmed by additional test(s) and, if the latter, what tests had been employed; (iv) whether the practice was aware of A. vasorum occurring locally, that is, within a 5-mile (8 km) radius; (v) how many confirmed cases of canine angiostrongylosis had been seen by the practice over the previous 12 months and (vi) at what time of year most cases had been seen by the practice. Practices were given one month within which to reply to the questionnaire. Nonresponding practices, which had e-mail addresses, were then sent three e-mail reminders at weekly intervals, and persistent non-responders, 10.1136/vr.102196 | Veterinary Record | 1 of 6
Downloaded from veterinaryrecord.bmj.com on June 27, 2014 - Published by group.bmj.com
Paper coupled with those practices without an e-mail address, were sent a second postal questionnaire one month later.
TABLE 1: Number and percentage of practices responding per region compared with those sent the questionnaire
Data analysis
Region
Descriptive statistics were obtained for variables representing the location of the practice (urban v suburban v rural), awareness of the presence of A. vasorum in the area, the number of cases diagnosed (clinically or with an additional test) and the type of diagnostic test employed. To visualise the geographical distribution of practices that had seen cases of A. vasorum infection in dogs, confirmed by additional diagnostic test(s) during the 12 months prior to the date of the survey, choropleth maps were created using Arc GIS 9.2 (ESRI 2006). The maps represented, for practices located in the same county, (i) the risk of seeing at least one confirmed case and (ii) the risk of seeing more than five confirmed cases. Smoothed maps representing Bayes standardised risk were obtained in GeoDa 0.9.5-i5 (https://geodacenter.asu. edu/software), a weight matrix based on queen continuity; first-order adjacency was defined. The spatial scan statistic was used to identify significant clusters of practices with a high probability of (i) seeing at least one confirmed case of A. vasorum infection in the previous 12 months and (ii) seeing at least six confirmed cases of A. vasorum infection in the previous 12 months. It was implemented in SaTScan V.8.1.1 (www.satscan. org) using a Bernoulli probability model, a circular window set to contain a maximum of 50 per cent of the population at risk, and Monte Carlo randomisation with 999 permutations, clusters for which P
