Sunday, 26 October 2014

HWSD testing Statistics

The Veterinary Genetics Laboratory (VGL) from UC Davis which is conducting all of the HWSD testing worldwide, has provided the Connemara Pony Research Group with a report on the numbers of ponies that have been tested for the HWSD mutation to date.

The reason for doing this is to help the CPRG to continue to help educate and disseminate up-to-date information to breeders.

The information from VGL is raw data only.  As with any statistics it is the analysis performed on the numbers which begins to paint the bigger picture.

The first message to understand is how the numbers are initially collected and how the table is constructed.    Also it must be noted that the ponies being sampled and tested are not 'random' samples which skews the results.
VGL states the following:
 "Attached are the summary stats by country of HWSD tests since we started offering the test at the end of August 2014. Percentage of carriers and affected were calculated only if more than 10 horses were tested per country. The carrier frequency in the VGL’s data is coming out higher than the value found in Dr. Bannasch’s research. However, keep in mind that we are using raw data from testing, which includes related individuals. Our estimates are not based on a random sample of unrelated horses and obviously overestimate the frequency of carriers and affected. With time, you’ll notice that the values will settle around the actual frequencies."

The full table from VGL is listed at the end of this page.  
This raw data  has to be adjusted and analysed in order to gain a truer picture of the situation in each country. 
VGL does not have any background information on the make up of individual populations of ponies in various parts of the world.  Country of residence does not always equate to country of origin. Using a combination of information of country of origin combined with country of residence a different picture emerges.

For example:

New Zealand is listed as having tested 21 ponies with 16 N/N and 5 N/HWSD.  However what is not obvious from the table below is that all five of the N/HWSD ponies are ponies imported from Australia. However another seven N/N ponies listed under NZ are also recent Australia imports. Another mare was imported to NZ from the UK; bred in Ireland by a French stallion, her imported in-utero colt is also in the NZ tested list.

Thus if the numbers are adjusted to acknowledge this, then the Australian/New Zealand  figures will look like this:

                            N/N    N/HWSD   HWSD/HWSD   Grand total    %age Carriers
Australia                  69           14                  1                          84                 17.9%
New Zealand          4             0                  0                            4                    0%

Similarly Australia has an N/N  colt  and an N/N filly listed which are both bred in Germany (these have been extracted from the numbers in the table above).

Canada lists four non Canadian bred stallions: one N/N from Germany, one N/N from USA, one N/N from Ireland and one N/HWSD from Ireland.

France has one N/N stallion from Great Britain.

Germany has one N/N stallion from Sweden, one N/N stallion from Ireland.

Six stallions bred and resident in Northern Ireland are listed under Great Britain.

New Zealand has listed one N/N colt of  German, Irish and French breeding but bred by a UK breeder.

USA has three Irish imports listed.

This breakdown is to demonstrate just how closely interlinked individual populations of  Connemara ponies are, across the world.  This becomes even more apparent when considering mares and fillies.

Looking purely at the country statistics from what is known from the results sent to  CPRG for positing on the HWSD tested ponies results page distribution of  ponies outside their listed country:

Australia and New Zealand tabled above.

Canada - stallions 3 imports as mentioned  above.  Mares 4/11 imported: 3 Great Britain, 1 Ireland

Switzerland - no notifications made to CPRG

Germany - 2/12 stallions as above; mares 0/11 imported

Denmark - stallions 0/6; mares 0/15 imported

France - both ponies are British bred, French residents.

Great Britain - one N/HWSD stallion from Ireland and one N/N bred in GB + the six stallions from Northern Ireland plus three mares also.
Thus GB when adjusted ONLY for the Northern Ireland situation, would look like: 53 - 9 from Northern Ireland + 2 from France = 46

          N/N     N/HWSD   N/HWSD  Total  %age Carrier
GB      40             5                  1         46              13.0%

Ireland:    8/10 of the ponies on the VGL table come from two owner/breeders.  These are on the CPRG page.  3/8 recorded are mares.  1/3 mares is N/HWSD; 1/5 stallions is N/HWSD.

Sweden: 25 ponies are on the blog list of which five are N/HWSD or HWSD/HWSD.  Even with the restricted numbers of notifications made to CPRG the %age carrier rate is still 20%.  

USA has the highest number of tested ponies to date.  Of those listed on the CPRG list, 19 are mares, 7 of which are direct imports (4 ex Ireland) or born to imported ponies in the USA (3).  3/19 mares are N/HWSD and 0/19 HWSD/HWSD.   Stallions 3/11 are imported.  1/11 is N/HWSD

Conclusion:  The uptake of the HWSD test by Irish owners and breeders based purely on population levels of the Connemara pony in each country, is very worrying.  The assumption is that this poor response is due to a very low awareness of the HWSD issue among the wider population.  The same situation is assumed for France and Great Britain.

France, which is the second largest producer of Connemara ponies in the world demonstrates an even lower uptake than Ireland - as the two ponies tested and listed are of  British breeding.

Great Britain is the third largest producer of Connemara ponies in the world; it too has significantly low uptake of the HWSD test.

Indeed Australia and the USA each have both tested more ponies than Ireland, France and Great Britain COMBINED!

For the most part the people who read this blog are already the more educated about HWSD among the breeders of Connemara ponies worldwide.  What each and everyone of you should consider doing, is to spread the message to those less well aware of the HWSD problem - and the solution afforded to breeders - by the availability of the  VGL test.

HWSD DNA Testing Statistics -September/October 2014

Country N/N N/HWSD HWSD/HWSD Grand Total % of Carriers % of Affected
Australia 64 9 1 74 12.2 1.4
Canada 15 6 1 22 27.3 4.5
Switzerland 3


Germany 25 7 0 32 21.9 0.0
Denmark 25 18 0 43 41.9 0.0
France 2


Great Britain 45 7 1 53 13.2 1.9
Ireland 10 2 1 13 15.4 7.7
The Netherlands

New Zealand 16 5
21 23.8 0.0
Sweden 27 9 2 38 23.7 5.3
United States 77 18 3 98 18.4 3.1
Grand Total 309 82 9 400 20.5 2.25

Test Result Disease Status

N/N Normal

N/HWSD Carrier

HWSD/HWSD Affected