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Establishment of a PPR Global Research and Expertise Network (PPR-GREN)

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From:
rabindra singh <[log in to unmask]>
Reply To:
rabindra singh <[log in to unmask]>
Date:
Wed, 5 Feb 2014 13:35:18 -0500
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Dear all,
To support what Michael said
1. Some times we as a researcher are very enthusiastic to report a disease outbreak in a new species. To me it is like reporting a new disease. What I feel PPR is not a virus which will remain hidden in buffalo and will not cause more and more outbreak, in an intenssive bufflo rearing system like India. There is only one outbreak in 1997 or so.
2. Even though I am involved in developing a DIVA stategy for PPR, I believe the fact that by the time we apply DIVA, we will develop a confidence of PPR Eradication using vaccines available. It is also a fact that avilable vaccine will have better efficacy and also economy than a marker vaccine. At the same time I belive that DIVA based diagnostics can be developed or already available and it needs to be appliied.
3. Cost of vaccination is definately more than the cost of vaccine, therefore use of multiple vaccines/combined vaccines i.e. PPR with sheeppox and PPR with goatpox may lead to control of three small ruminant disease by sinle Immunization.

kind regards,

Dr. R.P.Singh, 
Principal Scientist, Division of Biological Products,
Indian Veterinary Research Institute, Izatnagar, 
Bareilly-243 122 (Uttar Pradesh),
India

Alternate email: [log in to unmask]
Mobile:+91-9412360917
----- Original Message -----
From: michael baron
Sent: 02/05/14 06:42 PM
To: [log in to unmask]
Subject: PPRV range and control

Dear all,
It is brilliant that there is this solid interest in this topic, and a great willingness to engage with the challenges. Greetings to those of you whom I have met before. My name is Michael Baron and I have worked on the biology of rinderpest and PPRV for >20 years.
I would like to raise a couple of points based on what I have read so far.
PPR ‘prevalence’ does need careful handling in our understanding of it. There is a great tendency to accept serum antibody as an indicator of PPRV prevalence. The problem with that simple definition is that antibody means an animal has seen the virus, not that it has had the disease and/or spread the virus. It is a common assumption to jump from (for example) ‘cattle have antibodies to PPRV’ to ‘cattle can get PPR’, when actually all you can say is that the cattle have been in the presence of the virus; I probably have anti rinderpest antibodies after working with the virus for 20 years! Hence it has become extremely important that we establish to what extent cattle, buffalo and camels (to name the obvious examples) can pass on PPRV if they are infected with the virus, or if they only seroconvert as their immune system deals with what is to them a non-pathogenic virus. These are probably not difficult experiments to do, especially in countries with endemic PPR.
This is especially true given the existence of reports suggesting that camels and Indian buffalo can get PPR disease, based on virus isolation or identification in diseased animals. I know of two groups who have attempted to infect camels with isolated PPRV, without success. This needs to be done, and the same with buffalo. We need to establish whether the virus can cause disease in these animals under controlled conditions, and if it is excreted from infected animals. We need to know the virus in buffalo and camels is different, or if the disease only arose because of a combination of PPRV with another pathogen or an environmental factor. I believe that we should respect Koch’s rules on this. I know live virus isolation can be tricky, but this is what the FAO and OIE reference labs are for (well, we have to be useful for something!).
Thirdly, a comment on DIVA vaccines. Rinderpest was controlled and then eradicated without a DIVA vaccine. Careful use of the existing vaccines, with parallel serum surveillance to check how well the vaccination is being done, can achieve a lot. I say this as someone who is developing a DIVA vaccine; it is coming along nicely, but I know that it is likely to be used only in the final stages of control. I do not think there will ever be a DIVA test to distinguish the existing vaccines from natural infection, so we should just deal with that and focus on the best use of the vaccines we have. These do work, after all, which is more than can be said for some diseases.
Lastly, I am encouraged by the vaccination against multiple pathogens during PPRV control. It seems to me that the expensive bit of vaccination is putting people in the field, and the associated vaccine delivery chain (along with the surveillance afterwards). I think that we should not only think about PPR, but about small ruminant disease in general, and try to use this process to put in place a sound veterinary laboratory and field network covering multiple diseases.
best regards,
Michael

Michael D Baron PhD
Group Leader, Paramyxo&Bunyaviruses
t +44 (0) 1483 231024/1072/1145
email [log in to unmask] 
http://www.pirbright.ac.uk/research/Paramyxo/Default.aspx http://www.iah.ac.uk/research/Paramyxo/Default.aspx 

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