HELLENIC REPUBLIC MINISTRY OF AGRICULTURE D.G.OF VETERINARY SERVICES ANIMAL HEALTH DIRECTORATE DEPT. OF INFECTIOUS DISEASES, EPIDEMIOLOGY & DOCUMENTATION 5 October 2001 FOLLOW-UP REPORT No.1 ON THE EVOLUTION OF BLUE TONGUE ( BT ) IN GREECE AUTUMN 2001 1. Introduction A Preliminary Report on the recurrence of BT in Greece was released on 17/09/2001 and it was duly notified to the European Commission, the OIE and neighboring countries (Albania and FYROM). The Preliminary Report was further disseminated in the OIE Bulletin Vol.14 / No.38 of 21/09/2001 and is available on the web at : minagric.gr/greek/2.3.1.html The purpose of the Follow-up Report No.1 is to : Provide an up date on the features and the evolution of BT inside Greece, Explain the current control and safeguard measures in place, Review the epidemiological situation of BT in a Balkan context. 2. Evolution of BT inside Greece 2.1 Clinical aspects Up to date (05/10/2001) a total of 19 outbreaks (= infected flocks) have been confirmed in 3 Prefectures, namely in Grevena, Ioannina and Kastoria, on the basis of clinical symptoms suggestive of BT and subsequent laboratory (serology) confirmation. An account of clinical outbreaks is given in Table 1 and their exact location is indicated in Map 1 attached to this Report. * NOTE : Map 2 also includes parts of the Prefecture of Kozani, where no clinical outbreaks have been recorded, but is located within the 20 km-radius zones of Grevena and Kastoria. No. of Prefecture Village Date of Date of Animals Animals Affected Outbreak Susp. Conf. present Schick Dead Killed ( S / G ) & Dest. 2001/01 Grevena Smixi 30.08 13.09 800 90 30 90 2001/02 Ioannina Karyes 29.08 13.09 100/10 11 1 0 2001/03 " Miliotades 07.09 13.09 32 / 7 3 0 0 2001/04 " Miliotades 07.09 13.09 100/20 7 1 0 2001/05 " Dilifo 05.09 13.09 60 3 0 0 2001/06 " Kefalovriso 06.09 13.09 70 13 3 0 2001/07 " Vissani 06.09 13.09 280/40 17 2 0 2001/08 " K.Meropi 06.09 13.09 130 7 0 0 2001/09 " Faraggi 06.09 13.09 220/20 14 0 0 2001/16 " M.Gotista 17.09 24.09 240 6 0 0 2001/17 " K.Lavdani 14.09 24.09 45/5 3 0 0 2001/18 " Oreokastro 18.09 24.09 600/200 7 1 0 2001/19 " K.Lavdani 14.09 24.09 305 8 1 0 2001/10 Kastoria Dipotamia 18.09 24.09 135/25 5 0 0 2001/11 " Chrysi 18.09 24.09 227 6 5 0 2001/12 " Spilaio 25.09 01.10 100/17 5 0 0 2001/13 " Spilaio 25.09 01.10 170/30 4 0 0 2001/14 " Gavros 25.09 01.10 320/40 3 0 0 2001/15 " Ag.Kiriaki 25.09 01.10 155/115 6 0 0 Table 1 : Summary account of clinical outbreaks of BT / Greece / 2001 On the basis of clinical data presented in Table 1 the following comments can be made : a) With the notable exception of outbreak 2001/01, The average morbidity in sheep is 3,9%, and The average mortality in sheep is 0,55%. b) In most cases clinical symptoms are mild and transitory lasting 3 - 4 days and the affected animals appear to recover fully. For this reason laboratory confirmation is sought for in most cases and by the time serological results become available it is possible to identify the affected animals only by the ear tag number. This explains why no clinically affected animals have been killed and destroyed. c) In the case of outbreak 2001/01, the morbidity and mortality are significantly higher (11,25% and 3,75% respectively).In order to investigate the reasons for this deviation from the general pattern, the following scenarios may be of relevance : Involvement of different BTV type. This hypothesis is not valid because provisional typing made by SNT (serum neuteralisation test) has indicated the presence of the same BTV type 2001/01 as well as in other outbreaks in Ioannina and Kastoria. Involvement of different BTV vector or varying competence of the same vector. This hypothesis is being currently investigated by setting up light traps and collecting insects from all affected areas. In this respect, however, it appears more likely that the same low-competence vector is involved in all outbreaks because of common climatic and terrain conditions in North - Western Greece, but in the case of 2001/01 its efficiency is increased due to large size of local vector population Different epizootiological profile of the particular flock. Increased morbidity and mortality is probably due to underlying poor conditions (husbandry,feeding,pathological) complicated by BTV infection (see also 2.2 c). 2.2 Laboratory aspects Following confirmation of BT in Greece priority in the laboratory has been given to the following tasks, in order of importance : a) Virus isolation and typing. Field isolates have been cultivated through repeated passages in BHK-21 cells and in 10-12-day-old embryonated chicken eggs so as to obtain sufficient and pure BT virus to proceed to typing by VNT. This process is still in progress. Meanwhile, provisional typing has been attempted by SNT against anti-sera to various types known or likely to occur in the region, although the process is not totally reliable. So far there are indications of types 4 and 9, in single-type or mixed infections and in all affected areas, while preliminary tests for type 2 were inconclusive. b) Serology for diagnostic purposes For reasons explained in paragraph 2.1, most clinical suspicions have to be confirmed by serological tests, especially where cases are reported for the first time in previously unaffected areas. On the other hand, at this point in time and at the face of an active epizootic, a large scale serological surveillance was deemed inappropriate. For the same reasons, no attempt will be made to establish sentinel bovines in the affected areas until the situation in the field has stabilized. c) Targeted serology In Grevena selective targeted sero-surveillance has been undertaken in flocks contiguous to outbreak 2001/01 with a view to shed some light in questions discussed in paragraph 2.1 (c). For this purpose a total of 449 samples were collected from 14 sheep flocks in the vicinity and 13 samples tested positive (sero-prevalence = 2,9%). This is an extremely low percentage of sero-prevalence lending support to the explanation put forward in paragraph 2.1 (c), third intent. In Ioannina a preliminary serological screening was undertaken in sheep flocks and bovine herds contiguous to outbreaks. A total of 224 samples were collected from 22 sheep flocks in 14 villages, out of which 6 samples tested positive (sero-prevalence = 2,7%). In addition, 29 samples were collected from 3 bovine herds in 3 villages, out of which 1 sample tested positive (sero-prevalence = 3,4%). In both cases sero-prevalence is quite low and may be attributed either to early stage of the epizootic or to absence of competent vectors in sufficient numbers. d) Vector identification - surveillance The North-Western part of Greece had never been affected, or threatened,by BT and consequently no previous records exist concerning the presence, geographical distribution and seasonal variation of potential BT vectors. This task has been urgently undertaken in the present circumstances and at least 1 light trap has been set up in the affected areas. Insect collections are being currently sorted out and classified and definitive results will become available in the next few days. Provisional results available to date, however, indicate absence of C.imicola. 2.3 Epidemiological aspects In the Preliminary Report several questions were raised and recent evidence which have become available since then may answer some of them. Specifically : a) With regard to the source of the infection, it is worth noting that soon after Greece declared a recurrence of BT, Bulgaria also confirmed the disease on its territory and Map 3 indicates the affected areas therein. Furthermore, looking at Maps 2 and 3, it may be safely assumed that BT also occurs in Albania, F.Y.R.O.M, F.R. of Yugoslavia and, probably, Romania, where it is either not detected or not reported yet. In this Balkan context, it appears likely that the affected areas in Greece are situated along the extreme South-Western limits of the affected region. Furthemore, the Pref.of Ioannina and Kastoria, which are situated right on the the border line appear to be more heavily affected than the Pref. of Grevena, which is situated further inland. This pattern of spreading indicates that the disease advances in a South - South Western axis along the route of rivers, canyons etc., which is perfectly consisted with the prevailing winds and indicates that Greece is currently experiencing a re-incursion rather than a recurrence of BT. b) With regard to the means of infection, investigation is focusing on imports of live susceptible animals from affected countries in the recent past ( since the beginning of August). The success of this investigation, however, will depend on the availability of accurate information on the temporal and spatial occurrence of BT in the wider region. Naturally, it is always possible and indeed probable that BT spread to Greece by infective wind-borne vectors carried from the North. c) With regard to estimated time of primary infection, incursion into Greece is placed with reasonable confidence on 20 August plus/minus 2 days.