molecular tools: needs post-eradication

Maintaining Global Freedom from Rinderpest International Meeting • 20-22 January 2016 • Rome, Italy

Molecular tools: needs post-eradicationMolecular tools: needs post-eradicationMichael D BaronMichael D BaronScientific ConsultantScientific ConsultantFAO/AGAHFAO/AGAH


AbstractIn 2011, ten years after the last reported outbreak, the eradication of rinderpest was declared. However, as rinderpest virus stocks still exist, there remains a risk of rinderpest re-introduction.A semi-quantitative risk assessment was conducted to assess this risk, which was defined as the probability of at least one host becoming infected and infectious outside a laboratory anywhere in the world within a one-year period. Pathways leading to rinderpest re-introduction were: deliberate or accidental use of virus in laboratories, deliberate or accidental use of vaccines, host exposure to an environmental source of virus, and use of virus for anti-animal biological warfare. The probability of each pathway step occurring was estimated through expert opinion elicitation.The risk estimate was associated with a high degree of uncertainty. It was estimated to range from negligible to high, with the median being very low. The accidental use of laboratory virus stocks was the highest risk pathway. Reducing the number of virus stocks and restricting their use, as well as upgrading the laboratories to a higher biosafety level, would effectively decrease the maximum and median risks. Likewise, ensuring that remaining vaccine stocks are not used and are instead destroyed or relocated to a limited number of regional repositories would also have a major effect on these estimates. However, these measures are unlikely to eliminate the risk of rinderpest re-introduction so that maintaining response preparedness is essential.

The accidental use of laboratory virus stocks was the highest risk pathway.

…as rinderpest virus stocks still exist, there remains a risk of rinderpest re-introduction.


Keeping a watch for rinderpestActive surveillance:

not warranted for v rare disease

Passive/clinical surveillance:Low cost Low sensitivity

Differential diagnosis not perfect:e.g. mild rinderpest vs MCF, IBR or mucosal disease

Syndromic surveillance should be identifying suspect cases


Threats to rinderpest detection

1 Loss of skills/knowledgeHow many vets still know what rinderpest looks like?

2 Political sensitivityNo one wants to be the first to even suspect rinderpest

3 Rinderpest eradication!No-one is testing for rinderpest, even if syndromic positive


Threats to diagnosis

1 Loss of skills/techniquesPartially replaced by PPRV diagnostic skills

2 Absence of reagentsNo one re-ordering PCR primers, etc., ELISA kit reagents out of date

3 Restrictions on materialsRPV-containing materials restricted and kits no longer available


Available tests

• Test for virus – RT-PCR (primers available)• Test for virus – RT-qPCR (primers/probe available)• Test for virus – immunocapture ELISA• Test for virus – pen-side test (no longer made)

• Test for virus/antibody – AGID (serum available)

• Test for antibody – cELISA (not allowed to send out kit)


New reagents/tests required• Non-virus control for RT-PCR/RT-qPCR

– E.g. armoured RNA

PCR target

RPV targetPCR target

Transcribed RNA




• Non-virus control for antigen for ELISA/AGID– E.g. pseudotyped virus, bacterially expressed antigen, helper-

dependent virus, inactivated vaccine virus






• Sequence database– Full genome sequencing now relatively easy






• Sequence database– Full genome sequencing now relatively easy– Any virus can be remade (if required) from the genome


Production of recombinant RP viruses

Live virus

Initiator plasmids

Copy of any

genome in a plasmid

N

L P


Need for sequence database• Identification of outbreak virus

a) Where did it come from? b) Is it a release or an escape?

• Preparing for the futurea) How did RPV spread through Africa?b) Are we ready for the next bovine morbillivirus?


Appearance of novel paramyxoviruses


Alternative vaccines• Recombinant vaccinia?• Recombinant Lumpy Skin Disease virus?

• Effective, but not widely acceptable (GMOs)

• Expressed RPV protein?• Does not work

• Other morbillivirus, e.g. PPRV• Had not been tested, but RPV protects against PPR in goats


PPRV as a vaccine against RP

RPV vaccine No vaccine

PPRV Sungri/96 vaccine

PPRV Ivory Coast/89(wild type)

PPRV Nigeria/75/1 vaccine

Challenge with RPV Saudi/81

4 Weeks


Summary• There is a low but not negligible risk of RPV reappearance• This virus may come from laboratory escape or deliberate

release• Passive surveillance/awareness should be turning up

occasional suspect cases• Diagnostic laboratories should maintain capability (or good

links to lab with capability)• We need to develop alternate (nonviral) controls for diagnosis• We need to be prepared for the next bovine morbillivirus


Questions ?

molecular tools: needs post-eradication

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