Progress report on the evaluation of the prevalence of anti-neutrophilic cytoplasmic auto-antibodies (pANCA) in the population of Soft-Coated Wheaten Terriers in the United Kingdom

 Over the last few years the number of reported cases of protein-losing enteropathies and/or protein-losing nephropathies PLE/PLN in Soft Coated Wheaten Terriers (SCWT) has increased in the UK. It has been suggested that a familial link is involved in the predisposition for the disease and given the close links of the UK breed with US breed, concerns were raised that PLE could also be an emerging problem in UK SCWT population. In the USA it has been estimated that 10%-15% of the SCWT population develop either PLE and/or PLN at an average age of 4-6 years. 

Karin Allenspach and colleagues have shown recently that the presence of perinuclear anti-neutrophilic cytoplasmic auto-antibodies  (pANCA) is linked to later onset of PLE/PLN. This test has been evaluated in a group of 22 SCWT in the USA which were tested for pANCA every 6 months of their lives. The interesting fact is that a positive pANCA test developed in all dogs on average 2-3 years before showing any signs of illness. This indicates that the pANCA serum test could be used as an early marker for PLE/PLN in this breed. Positive dogs could then receive appropriate treatment to reduce the risk of developing severe clinical signs and if a familial pattern is identified, their participation in a breeding program could be reviewed early in their life, ensuring the continuation of a healthy breed.

In 2007 we carried out a base line study to estimate the number of SCWT in the UK which are pANCA positive. We were able to collect and test blood samples from 189 dogs, and complete records were available of 188 dogs. The samples were collected either during sampling sessions organised by the SCWT Club GB and the WHI or directly at the Royal Veterinary College (RVC) in Hatfield.  Of the 188 dogs, 39 tested pANCA positive (20.7%). This prevalence is much higher than what we expected. If it turns out that the pANCA test is indeed a good predictor for PLE/PLN, then these dogs might be at higher risk to develop protein losing diseaes later in their life. But by no means are we certain that the a positive test means that the dogs will develop the disease later in life. To be able to assess how much more likely pANCA positive dogs are to develop the disease compared to pANCA negative dogs, we started a follow-up study in summer 2008.  With this study we hope to re-test 80 pANCA negative and as many positive dogs as possible in intervals  of six months over the next 2-3 years. In June and July of this year, we were able to take blood samples from 82 dogs in two sampling sessions in Weedon Bec, Northhampton and St. Leonard’s Hall, Oxon. Moreover, eight samples were taken by private veterinarians and sent to the RVC by post (Table 1), which sums up to a total of 90 samples. Out of the 90 dogs tested, 77 had been classified as negative and 12 as positive in the initial sample. One dog joined the study only this summer and therefore did not have a test result from the baseline study.

Table 1: Number of dogs sampled and tested for the first round of the longitudinal pANCA study in 2008

Date	Location	Nr. of dogs tested
21/06/2008	Weedon Bec, Northhampton	43
13/07/2008	St. Leonard’s Church Hall, Oxon	39
Diverse	Sent to Royal Veterinary College post	08
Total		90

All samples collected were tested for pANCA using immunofluorescence, a method that allows labelling of antibodies with fluorescent dyes. Conversion in the pANCA test result from either negative to positive or from positive to negative was observed in five dogs. Such fluctuations in antibody concentrations seem to be a physiological phenomenon and have already been observed in the pANCA study in the US. The regular testing over a prolonged time period will provide conclusive evidence about the definite pANCA status of a dog. This is another reason why it is worthwhile to re-test positive and negative dogs.

In all collected samples we also measured the albumin and total protein concentration. This allows to detect occult protein-losing disease, as a decreased serum albumin concentration is a sensitive indicator of possible PLE/PLN.

The reference range for albumin concentration in dogs in our laboratory is 28-39g/l. Among the tested 90 dogs, 33 (36.7%) had normal, 1 (1.1%) had decreased and 55 (61.1%) had increased albumin levels. Serum albumin is produced in the liver and has important biological functions, such as blood volume regulation or transport of certain substances (e.g. fatty acids or hormones) in the blood. However, serum albumin concentrations above the reference range occur frequently in healthy dogs and could just be related to dehydration on the day of serum sampling.

The pANCA results as well as the albumin levels have been communicated to the owners either by mail or email. If you have not received your result, please contact the Clinical Investigations Center (01707 666 605 or 01707 666 223, cic@rvc.ac.uk) at the RVC. If you have questions regarding the interpretation of your results or if your dogs develops any clinical signs indicative of possible protein-losing diseases, please contact Karin Allenspach (kallenspach@rvc.ac.uk or 01707 666 366).

Another aim of our study is to find out if familial patterns of PLE/PLN in the breed are present. In the UK, only a limited number of SCWT with definitive evidence of protein losing disease are known and therefore we used the pANCA status to explore the available pedigree dataset. Preliminary results indicate that a dog is more likely to be pANCA positive if a sibling also tested positive, which would indeed suggest a familial pattern. Further analysis will reveal if the presence of certain common male ancestors or high in-breeding coefficients are associated with the pANCA status. 

Last but not least, we would like to encourage all dog owners that have participated in the first session in 2007 to re-test their dog in the following sessions. This is also possible if you have missed the first follow-up testing session. Most of all it would be interesting to re-test pANCA positive dogs as this will allow us to truly assess the performance of the test in a representative dog population.

We would like to thank all participating owners and their dogs for their willingness to help us with our research. We are convinced that thanks to the efforts of all of you we will substantially contribute to tackle PLE/PLN-related-problems in the UK Soft Coated Wheaten Terrier breed. Together we set an example on how responsible breeders can make a difference and ensure the sustainable good health of the breed.

Best wishes,

The RVC team 

Royal Veterinary College, October 2008