Dear all,
As everybody introduces him or herself, I would like to mention that I have work for 8 years in the PARC project in Ethiopia, and after that in GREP and the AU-IBAR PACE programme as sub-regional epidemiologist and I am currently working as Livestock Team Leader at FAO Ethiopia.
I am sorry that the message has become a bit lengthy and also my excuses for coming in quite late.
It is good to see the massive interest from various parts of the world for PPR.
I would mainly like to contribute to the vaccination, and sero-monitoring discussion.
Vaccination:
The estimated livestock population of Ethiopia includes 25.50 million sheep of which about 75% are in the highlands of Ethiopia, while of the 22.78 million goats of which 75% are located in the pastoral lowland areas. The large size of the small ruminant population in Ethiopia and the rates at which these populations replace themselves place would place very high demands on annual vaccination programs. As about 50% of a small ruminant population is new born each year, flock immunity levels rapidly decline after an annual vaccination programme, and therefore a strategy of repeated annual vaccination campaigns is not likely to eradicate PPR from the small ruminant population. Large numbers of vaccinations will still be required in targeted programs and these vaccinations will need to be delivered in a concise time span to achieve high flock immunity.
One of the lessons from the rinderpest campaign in Ethiopia is that if in a particular ecosystem a very high immunity level was achieved, rinderpest disease quickly disappeared. The virus quickly runs out of susceptible hosts... Of course one had to be alert for reintroduction, especially after the calf crop became susceptible again.
To achieve high immunity levels the following are crucial issues:
1. Identifications of the various small ruminant ecosystems in the country, although in the end most of them will be somehow connected, but mostly trade movements are in a particular direction and movements within pastoral system are quite predictable.
2. Using participatory epidemiology, we assessed the PPR disease status of a sub-population. In the case of rinderpest, participatory disease searching was used to detect disease as well as information about when the last outbreak was observed in that particular area. In case no clinical rinderpest was found and the livestock keepers mentioned that the last rinderpest outbreak was observed over three years prior to the date of the PDS in that particular ecosystem, serology was used in carefully aged young stock to proof absence of virus circulation. Again in the case of rinderpest, if we could not detect rinderpest disease and the serum samples of young unvaccinated stock were negative, we excluded the area from vaccination (this reduced the area to be covered substantially and consequently the veterinary service could focus resources on the areas where rinderpest was circulating).
In Ethiopia we are trying to apply the same strategy for PPR, but one difficulty observed already is that pastoralists in contrast to rinderpest (where we even they even had different names for endemic rinderpest and rinderpest outbreaks) do not have a specific name for PPR. The local name often reflects a respiratory complex and thus includes CCPP and pasteurellosis. The pen side test currently tested helps in identifying whether the disease is PPR or not. In case disease is detected in the area, a focussed well managed vaccination programme should be conducted with the following important steps:
a. As already clearly stated by Dr. Karim, the use of certified vaccine is the very first step.
b. Monitoring of the cold chain is very important in case of thermo-labiel PPR vaccine and monitoring the time between the thermostable vaccine leave the cold chain and use in the field is another important factor. None of the thermostable vaccine that has left the cold chain should ever be returned!
c. Monitor the time between dilution of the vaccine and its use as well as the way it was kept during that time. (during the rinderpest campaign we instructed that this time should not exceed 30 minutes).
d. Marking of vaccinated small ruminants and while conducting the vaccination programme check for any unvaccinated flocks. Although not yet tested Ethiopia will use paint to mark vaccinated animals. This will facilitate detecting of unvaccinated flocks for three weeks to a month, which is sufficient to achieve very high vaccination levels, especially if the community assist in identifying these flocks.
e. Focussing vaccination on areas with on-going disease transmission and areas harbouring infection. It is a well-established principle that infection with wild virus combined with vaccine-induced immunity gives very high flock immunity levels. The highest level of immunity can be achieved when livestock owners are suffering losses from the disease.
f. Ideally pulsed vaccinations should take place at the time that the young stock become susceptible, otherwise revaccination of these populations should take place with a short time interval to ensure high vaccination coverage
g. An added advantage is that such a strategy will stimulate veterinarians to become disease strategist, it will enhance information collection and a steadily build-up of knowledge rather than veterinarians becoming institutionalised vaccinators.
3. Sero-surveillance and Sero-monitoring.
a. Sero-monitoring, mainly needed to satisfy donors, will only be helpful to prove that the vaccination programme has achieved the required immunity level, if we are convinced that all steps described under point 2 are well monitored. If not, it will raise more questions than it answers. In my experience it is better to use the limited manpower and transport to perform the monitoring as described under point 2 and to detect unvaccinated flocks, than to spend it on a random sample survey.
b. Even at the time that vaccination is on-going in some parts of the country sero-surveillance will assist in identifying areas that do not require vaccination. And as stated by some of the colleagues, it is good that the routines are established in at least the national reference laboratory.
c. Of course in the end, serosurveillance will be required to proof absence of circulating virus.
Best regards
Gijs
Gijs van 't Klooster
FAO Ethiopia, Livestock Team Leader
P.O. Box 5536
Addis Ababa
Ethiopia
Mobile: +251 (921) 329756
Office: +251 (11) 647 8888 ext 107
Fax: +251 (11) 647 8800
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