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Peste des petits ruminants

FAO mission to follow up outbreaks of peste des petits ruminants (PPR)

Background: outbreaks reported in the Thrace region of Turkey

Turkey first reported outbreaks of peste des petits ruminants (PPR) in 1999. On 12 October 2004 , the General Directorate of Protection and Control (GDPC) of the Ministry for Agriculture and Rural Affairs (MARA) of Turkey reported to the World Organisation for Animal Health (OIE) that six outbreaks of PPR had occurred in September, two of which were in the province of Edirne . This was the first occasion that PPR had been reported in the Thrace region of Turkey , and because the province of Edirne borders Greece and Bulgaria , FAO considered the event of significance for the regional animal health situation.

Turkey has reported that there were six outbreaks of PPR in the Thrace region in September 2004

As incursions of any exotic disease into the Thrace region may indicate a risk of foot-and-mouth disease (FMD) incursion, GDPC provided further information to the European Commission for the Control of Foot-and-Mouth Disease (EUFMD) Secretariat on the outbreak locations and on the control measures being applied in the region. Training and diagnostic support for early detection of PPR in Thrace region was provided by FAO through the ongoing Technical Cooperation Programme project TCP/RER/2903, “Strengthening active surveillance for FMD and other exotic diseases in the Thrace region”, and the EUFMD Secretariat offered expert help to assess what further action could be undertaken to ensure the control of PPR in this region.

Findings of the follow-up mission

Incursions of any exotic diseases into the Thrace region may indicate a risk of FMD incursion

Under project TCP/RER/2903, an expert team led by Dr John Anderson (Head, FAO World Reference Laboratory for Morbilliviruses, Institute for Animal Health, Pirbright , United Kingdom ) was assembled in the Edirne province from 24 to 29 October 2004 . The team, which included Drs Mustafa Tufan (GDPC), S irin Gulsum Cizmeci (Central Veterinary Control and Research Institute, Etlik, Ankara [the “Etlik Institute”]) and Dónal Sammin (EUFMD Secretariat; Animal Health Service, FAO), met with local veterinary authorities to discuss disease control measures that had been undertaken since the outbreak was reported, to plan further surveillance activities and to visit the outbreak locations.

A serosurvey for FMD, bluetongue (BT) and PPR had been conducted in the Thrace region in June 2004 with FAO support under TCP/RER/2903. Two to three months before the first reporting of PPR, sera had been collected from 100 villages in the Thrace region, including 17 villages in Edirne province. Twenty-four small ruminants and twenty-four cattle had been sampled in each village, and sera had been divided between the S ap (FMD) Institute, Ankara , and the Etlik Institute to be tested for antibodies to the FMD, BT and PPR viruses.

Serological testing for antibodies to PPR virus had only recently been completed when the FAO follow-up mission was conducted. An initial interpretation of these serosurvey results was attempted to provide a “snapshot” of the regional disease situation. In Edirne province, 5.4 percent of cattle and 15.7 percent of small ruminants were seropositive for PPR virus. Significant clusters of seropositive animals were identified in three villages in the Enez district (near the border of Greece ), and a further cluster was identified in a nearby village in the neighbouring Ke s an district.

Although most of the seropositive cattle were more than two years old, and many were old enough to have been vaccinated with rinderpest vaccine before its use was discontinued in 1998, the majority of the seropositive small ruminants in these villages were less than one year old.

The chronology of events surrounding the PPR outbreaks in the Thrace region suggests that clinical PPR was most probably present in the first affected village from mid- to late August 2004 and was probably at first misdiagnosed by a veterinary practitioner as clostridial enterotoxaemia. The source of infection was not identified. The disease spread to a second affected village, and transmission may have been associated with the movement of veterinary technicians between the villages (clinically affected animals were vaccinated against clostridial diseases in the first village, and two days later, two flocks of sheep in the second village were vaccinated by the same personnel using the same equipment). Control measures, e.g. killing affected animals, vaccination of infected flocks and emergency ring vaccination of all small ruminants in neighbouring at-risk villages with a homologous PPR virus vaccine produced at the Etlik Institute, were undertaken. No further evidence of disease was reported in affected or vaccinated villages.

Conclusions and recommendations

Epidemiology of PPR in the Thrace region

FAO provided training workshops for laboratory personnel and commercial testing kits, which greatly assisted laboratory diagnosis of PPR during the outbreak

Although flock sizes are generally small, the common practice of communal grazing greatly increases group size (to more than 1000 animals in the present case). However, even this population size is unlikely to be sufficient to maintain circulation of PPR virus for long periods. Clustering of PPR-seropositive animals in many of the villages sampled during the 2004 Thrace serosurvey and the relatively small size of groups of susceptible animals in each village (in the absence of significant animal movement between villages) would suggest that the virus is being reintroduced constantly by sheep brought in from areas of eastern Turkey where PPR is endemic.

Post-vaccination PPR surveillance

PPR vaccine is extremely thermolabile and requires careful handling in the field to ensure that it retains its potency. Therefore, follow-up serosurveillance was recommended to ensure both the efficacy of emergency vaccination in vaccinated villages and the absence of virus circulation in villages adjacent to the vaccination zone.

A trial run was undertaken by the expert team and local veterinarians in which two villages were visited, one within and the other immediately outside the vaccinated zone. In each village, a random sample of 60 small ruminants was selected; the animals were examined for clinical signs of PPR (Photo, page 14); and serum was collected to test for antibodies to PPR virus.

Excellent detective work was done at the district level

It is important to note that serological tests that are currently in use do not allow for discrimination between vaccinated and infected animals. Therefore, it was suggested that, within villages where PPR vaccination has been applied in small ruminants, cattle in close contact with sheep/goats could be considered sentinel animals and could be sampled for evidence of seroconversion. Furthermore, as vaccination interferes with the interpretation of all PPR serosurveillance data, every effort should be made to introduce some form of permanent marking for vaccinated sheep and goats.

Raising awareness of the disease

Awareness of the clinical signs of PPR is essential for rapid diagnosis and early warning. An excellent manual on the clinical diagnosis of PPR, with photographic illustrations and text in Turkish, was published by GDPC in 2001. If redistributed to practising veterinarians throughout the region it would greatly help to raise awareness of the disease.

Continuation of multinational surveillance activities in the Thrace region

The FAO-funded project (TCP/RER/2903) for active surveillance of foot-and-mouth disease, bluetongue, PPR and sheep and goat pox in the Thrace region will end in early 2005. This project provided training workshops for laboratory personnel and commercial testing kits, which greatly assisted laboratory diagnosis of PPR during this outbreak. As it is unreasonable to expect Turkey to bear the brunt of funding animal disease control measures from which all neighbouring countries benefit, the expert group believes that support should be given to continue transboundary animal disease surveillance in the Thrace region. At the time of writing, FAO is negotiating an agreement with the European Commission to support continued serosurveillance in 2005.

Recognition of the role played by the local veterinary services

The local veterinary authorities in Edirne province deserve recognition for the excellent job they have done in rapidly controlling the PPR outbreaks. In particular, excellent detective work was done at the district level, which highlighted the possible role of veterinary technicians in transmitting the disease from the primary outbreak location and led to the identification of another “infected” village. Neighbouring countries should be reassured by their prompt, efficient action.

The authors also wish to acknowledge MARA staff in Edirne province and Uzunkopru district for their friendly cooperation, assistance and hospitality.

John Anderson, Institute for Animal Health, Pirbright , United Kingdom , and Dónal Sammin, EUFMD Secretariat, FAO

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