Monday, 11 May 2015

Analysis of the latest HWSD test results from VGL Davis

The Veterinary Genetics Laboratory of  UC Davis has forwarded the HWSD test results covering 23 October 2014 to 4 March 2015.

Using the raw data supplied by VGL the CPRG makes the following report.

Sadly the momentum of the first 6 weeks of testing has not been maintained. In the first flush of the test being available, 400 ponies were tested. In the six months following, the number has dropped to 264 ponies tested.

It is now quite obvious and incontrovertible that the countries producing the largest number of ponies are the poorest performers with regards to HWSD testing of ponies.

The fall off in testing is demonstrated by the following chart:

The two comparative charts demonstrates the country variables.

Please note that changes in scale occur relative to the data range in each individual chart.

This means that one cannot just compare the 'visual pattern' between one chart and the next.

A secondary issue requiring clarification is the reporting rate of test results. This varies from country to country

It is quite obvious that there are more ponies being tested than for which any information is being publicly listed by the owners. Of course there is a fundamental right of privacy for pony owners.

Below is a an overall view of reporting rates. The reporting rate is established by comparing the number of ponies listed on the CPRG tested ponies page, to the number of ponies tested at VGL. 
So the total number ponies tested is over six hundred.  Across all the countries the reporting level is 53%  of ponies tested with the median slightly higher.

Each country is then charted and shows the testing statistics for the period September 2014 to 4 March 2015 as two separate cohorts. Status notification equates to reporting rates as previously explained.

With only three ponies tested in France it is very easy to get 100% reporting!!

One of the issues facing all responsible breeders is the carrier rate WITHIN discrete populations. As stated from the beginning of  HWSD research, the carrier rate is reflective of the original ponies imported into any particular country and any subsequent importations.


What this data illustrates is that the uptake of HWSD testing of breeding stock is far lower than what is required for the ongoing safety of the breed.  Some countries have been much more proactive in testing for HWSD.  These countries are also the ones which, on a numerical basis have to be considered to be 'minority' populations.

The 'big three', Ireland, France and the UK have really abysmal testing rates; both individual breeders and the breed societies in these countries, really need to have a good hard look at themselves and their motivations as to why they are not testing.

Until there is a larger population of ponies tested, the carrier population does remain 'biased'. However even with the limited information already available, between the two tested cohorts for which there is information, the drop in the carrier level is only minimal.  
This is a concern.

The majority of the test results being reported are for N/N ponies.  Only one country, New Zealand, has reported all of the tested carrier ponies.  

It is very obvious that the reporting of carrier or affected status ponies is at a rate very much lower than the actual number being tested.  

The raw data is as follows:

HWSD DNA Testing Statistics - 10/23/2014 - 03/04/2015

By Country N/N N/HWSD HWSD/HWSD Grand Total
Australia 29 4
Canada 7 2
Germany 14 4
Denmark 8 2
Finland 12 7
France 1

Great Britain 21 10 1 32
Ireland 25 5
The Netherlands 15 5 1 21
New Zealand 2

Sweden 25 14 1 40
United States 39 9 1 49
Grand Total 198 62 4 264