Scientists and international organisations are well placed to eliminate another deadly animal disease, says Michael Baron.
The eradication of the long-feared cattle disease rinderpest, announced by OIE and FAO in June 2011, is a momentous achievement. John Anderson has already written on this blog about the lessons learned during the rinderpest eradication programme, which I’ve also described on video.
If we can do it once, we can do it again; the only question is: what should be the next target?
For better or worse, many people in developing countries are dependent on livestock (sheep, goats and cattle) for their food, or for trade. Sheep and goats (or ‘shoats’ for short), in particular, form the mainstay of 100s of small-scale livestock keepers in rural communities, both for the milk they give and the meat they provide. Anything that improves the health of shoats reduces poverty and improves local health and welfare, which improves education levels, which again improves general welfare in a virtuous cycle.
The next target
One of the common diseases of shoats in developing countries is peste des petits ruminants (PPR), sometimes known as goat plague or kata. The disease was first described in West Africa, which explains the French name. PPR is now found in almost every country in Africa north of Mozambique, as well as the Middle East, the Indian subcontinent and through into China. It can cause high mortality – up to 90% – and its relentless spread seems unaffected by the current individual national attempts at mass vaccination which are not well integrated.
PPR is caused by a virus of the same group that causes rinderpest, and which shares many of the same characteristics: the virus spreads by close contact between animals (no insect or tick vector), it has only one serotype (so a single vaccine protects against all known forms of the virus), and an effective vaccine and equally good diagnostic tests exist.
The basic tools that were used in the eradication of rinderpest are therefore in place to do the same job on PPR, and there is growing acceptance in international bodies such as the FAO that PPR eradication is possible and should seriously be considered. I discuss this in this short video too.
That’s not to say we couldn’t make some improvements. There was never a DIVA vaccine (which allows one to Distinguish Infected from Vaccinated Animals) for rinderpest, and it meant it was never possible to keep scanning for disease while vaccination was going on. Several labs, including my own, are trying to make DIVA vaccines for PPR and I am sure one will soon exist which will help in the overall programme.
The experience of rinderpest eradication was that getting good local involvement in tracing disease was critically important, and kits are being developed that will allow sick animals to be tested for PPR in the field, allowing much more rapid disease identification and therefore more rapid responses. We also need to fill in the gaps in our knowledge of the distribution of PPR in both domestic livestock and wildlife because various species of wild goats and gazelles are susceptible.
None of these are insurmountable problems. There are a large number of livestock diseases for which we have no vaccine, like African swine fever, or which are too varied to be tackled with a single vaccine, such as Bluetongue, for which you need 25 different vaccines.
In contrast, ridding the world of PPR lacks only the willingness of the richer countries to fund the work and of the countries where it exists to work together to get the job done.
Perhaps the most important lesson that we learned in getting rid of rinderpest is that we can aspire to not just control and continuously try to manage a veterinary disease, but to remove it permanently on a global scale, thereby eliminating the threat as well as the cost of control from all future generations.
About Michael Baron
Michael Baron has worked on the basic biology of rinderpest and PPR at the Institute for Animal Health for the last 20 years. He is a self-confessed lab rat who would like to think that he can help the people who do the real work on controlling these diseases, out in the field, by providing some of the tools they need.