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Email from Dr Roger Breeze to on the subject of African Horse Sickness

Received July 1 2009

Hi Mary

So here we are again with AHS!

I assume everyone is familiar with the African website on this at

When I was at Plum Island I started a research program on AHS that was developed by Will Laegreid. This was very productive and he showed that a pox virus-based vaccine would work and also worked out the molecular diagnostics and the reasons that some strains are highly lethal and others not. This research was never very popular in USDA amongst my bosses because "the horse is not an agricultural commodity". I am sure you hear the same story in UK. Yet horses are responsible for an enormous amount of economic activity in the US and everywhere else in the developed world. It seemed to me that there would be a national hue and cry if AHS led to people's horses being seized and killed and to widespread aerial spraying of insecticides in urban areas.

I am not sure what I could do to help the discussions in UK but if there is something I am willing to help.

A few random thoughts to start.:


1. There is an old saying that it is better to have a vaccine and no epidemic than an epidemic and no vaccine.

2. We can't solve the problem of exotic animal disease threats to the US and Europe by building defenses and walls in the US and Europe - we have to intervene to help other countries remove the threat at the source.

3. The countries that are the sources do not have the scientific capability to invent and produce the solutions, but they can apply these solutions if others make them available.

4. The real story is not about the threat to horses in Europe - which may or may not become real at this time (probably will eventually) - it is about the tens of thousands of horses and donkeys that die and will die of this disease in Africa over the next 10 years alone. In Gambia, a rich farmer uses N'Dama cattle to pull his cart because these animals are genetically resistant to trypanosmiasis (sleeping sickness), a modest farmer uses a horse or donkey (which will die of AHS eventually), and a poor farmer carries his own burden. Actually, I should not use the word "his" because it is really "her" that is doing all the farm work. AHS is one of the livestock diseases that keeps people in poverty in Africa.


Will Laegreid looked up the history of AHS. There is a famous woodcut of Henry Morton Stanley greeting David Livingstone on the edge of Lake Tanganyika.

You will see that Stanley (and Livingstone) are on foot and porters carry bundles on their heads. When Stanley arrived in Zanzibar he bought horses to carry his loads  - the locals told him the horses would die of fever a couple of weeks after he got them to the mainland. And so it proved. (I forgot the names of the horses.)

The first animal or human virus discovered was FMD. Most do not know that the second was AHS, discovered by John McFadyean at the Royal Vet College London in blood samples brought back from Africa. He injected horses and gave them AHS in central London! There is a very interesting but densely written book called "Science and Empire: East Coast Fever in Rhodesia and the Transvaal (Cambridge Studies in the History of Medicine) (Paperback) by Paul F. Cranefield. that describes how UK Imperial policy in the late 1800s was to establish a science base in the UK to exploit the Empire (that is where Kew Gardens came from) and dealing with these dangerous livestock diseases was one element..

It seems to me that there are 4 main issues:

1. Can an AHS vaccine that protects against the various different strains be developed in a format that allows vaccinated horses and donkeys to be distinguished reliably from previously infected horses and donkeys that might be carriers of infection? The answer is clearly yes. The solution might be different for Europe which seeks to protect against a periodic incursion from one strain and Africa which is faced with multiple strains and reservoir hosts in zebras.


2. Can that vaccine or vaccines be manufactured to a quality standard and at a price to permit its use in 1. Europe, and 2. Africa (I am implying that the quality standards and prices will be different). The answer is yes.


3. Will regulatory authorities in UK and the EU approve the use of an AHS vaccine?

a. Will they define the characteristics of an approvable vaccine - such as allows vaccinated animals to be distinguished from infected or previously infected animals? What efficacy criteria will there be and will there be restrictions based on the potential for carrier animals?

b. When will vaccination be allowed? Before confirmation of AHS presence in a country or only afterwards?

c. How does vaccination fit into the National Emergency Response Plan for AHS?

d. What criteria will be used to be sure vaccinated horses can move freely across international boundaries?

I don't know enough about the levels of concern and of AHS threat in Europe to answer any of these but it seems to me that a potential market in Europe (vaccine only used once in a blue moon when AHS is found) is very much less attractive than a small but regular market where owners can choose to vaccinate as they wish.


4. Who is going to pay to make sure this happens?

One can agitate to have DEFRA fund this but I would not waste my time trying. The solution must lie elsewhere. The critical role DEFRA and the EU play is to answer question #3 above about how a usable vaccine is defined so one knows whether there will or will not be a regular European market.

There are 3 main cost elements:

a. Proving that a candidate vaccine works and meets the DEFRA/EU criteria for use in Europe (and probably concurrently answering African issues).

b. Taking this candidate vaccine and making it into a commercial product.

c. Sustaining the availability of this commercial product to an agreed minimum return on investment.

Many people are writing about the challenge of getting vaccines to the developing world (for human health) but there is much less talk about the livestock vaccines, but see and


I have not read up on all the latest results but I think some candidate vaccines are available that immunize and yet allow infected animals to be identified. These are based on pox viruses that cause no disease in horses but promote immunity to AHS. The first of these pox viruses was vaccinia and now canarypox is at the forefront because there has been reluctance to use vaccinia in circumstances where people who are immunosuppressed for some reason might get infected and catch severe disease. Merial has put a lot of effort into proving its canarypox vector is safe.

I expect that Merial's financial requirements for a viable AHS vaccine would be very much greater than a small company located outside the US or Europe. I don't know the patent basis for canarypox vectors or even if there is one. But I would not limit the possible manufacturing sources of a canarypox or acceptable pox vectored AHS vaccine to the US and Europe - maybe the Chinese could do this. The Harbin Veterinary Reseach Institute is well respected -

I would be looking for a non-governmental solution (except for the DEFRA/EU decisions above). If one could determine the rough costs and set out an end-to-end solution (from new discovery through manufacture through regulatory approvale to field markets) I think the funds might be pieced together from various sources. I find the real situation in Africa and the impact on poverty to be persuasive and an entree into other funding streams. All this would take leadership of course. But The Donkey Trust has done splendid work on animal welfare in developing countries and might contribute.

Anyway, hope some of this helps!

All the best