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How Vaccination was used for Foot and Mouth Disease in Uruguay in April 2001 and subsequently
Dr James Irvine, FRSE DSc FRCPEd FRCPath FInstBiol
During the last ten years vaccines have been successfully used for the control of outbreaks in Bulgaria (1994), Thrace province of Turkey (1995, 1996), Macedonia (1996), Yugoslavia (1996), South-Africa (2000, 2001), The Netherlands (2001), Argentina (2001) and Uruguay (2001). In 2001 Uruguay enjoyed FMD disease free OIE status without vaccination. On 23rd April 2001 FMD was clinically suspected and confirmed on 24th April. It was caused by type A. It was thought that the virus entered Uruguay from neighbouring Argentina by the movement of trucks, machinery and people. This is supported by the fact that a particularly intense sero-epidemiological surveillance had been carried out in the area along the Rmo Uruguay immediately prior to the outbreak (March and April) and had shown no evidence of FMD viral activity. The outbreak in Uruguay lasted from 24th April until the 26th August, 2001. The incidence rates were comparable with those of the UK in 2001 and were about 50 per day one month after the outbreak (Figures 1 & 2, Table 1).
Figure 1: Uruguay FMD Outbreak as of May 11, 2001. 348 Confirmed Outbreaks. Source: United States Department of Agriculture.
Figure 2: Weekly FMD Foci in Uruguay from 23 April 2001 - 22 October 2001. Source: Uruguay Embassy, 22 March 2002.
Table 1: Outbreak Evolution in Uruguay, 24th April 2001 - 6th February 2002. Source: Uruguay Embassy, 22 March 2002.
Slaughter of all sick and in contact animals was started immediately, together with movement restrictions (initially locally and export) and extended nationally on 27th April, enforced by the police and the army.
Ring vaccination and anticipated mandatory slaughter of all vaccinated animals was started on 27th April in accord with their contingency planning. In view of the further spread of the disease this was quickly superseded by massive vaccination of all cattle in the country and discontinuation of stamping out (no more slaughter whether the animals were diseased or not). Neither sheep nor goats were vaccinated as they were thought to have only a minor role.
Thus the first massive emergency vaccination, including all the cattle population on a national scale, began on 5th May 2001, at the border with Brazil, and proceeded from North to South and from East to West and was completed by 7th June, 2001. Almost 11 million cattle were vaccinated, whilst the 12 million sheep grazing beside them were not. The pigs were not vaccinated as it was considered that the particular vaccine used was not effective in pigs. The vaccine was provided to the farmers free by the authorities. It was oil-based. There was no shortage. Vaccination was carried out by the farmers themselves following a clear geographical pattern and had to be done within defined dates for each region. Checks were carried out by government officials using serological tests and a 99% compliance demonstrated.
The second round of massive emergency vaccination (booster or re-vaccination) was started on 15th June 2001 and was completed on 22nd July 2001 providing, due to its booster effect, an expected 99 to 100% effective protection. The rate of new cases quickly dropped to a few incidences per day (see Figure 4). Movement restrictions were discontinued on the 6th of June, 2001. Instead of slaughter animals were quarantined and there was a stand still of animal movement. The only slaughter that took place occurred during the first few days of the outbreak and was confined to April only.
A European Commission mission to Uruguay took place between the 25th and the 29th June 2001 in order to examine the epidemiological situation regarding FMD and the control measures in place (1). On the 26th of August Uruguay had their last case. A European Commission mission to Uruguay took place between the 1st and 4th October, 2001 in order to evaluate the controls in place over foot and mouth disease (2).
During November 2001, all calves born during the year 2001 were vaccinated or re-vaccinated. This vaccination period finished on 30th November, 2001. The vaccination of all cattle was carried out in February 2002 and again in May 2002, involving Uruguay’s whole cattle stock. In November 2002 it is planned that all bovine animals born during the year, until August, shall be vaccinated. Meetings with other countries within the region are planned in order to establish future eradication programmes. In the months of February, April, September and October 2002, serological surveys were and will be carried out in cattle and sheep.
There are no documented cases in this outbreak of vaccinated animals causing new outbreaks. There have been no new cases of FMD in Uruguay up to the time of writing, June 2002: i.e. 10 months since their last case. There is therefore no evidence that “carrier” animals could transmit disease to other animals in this context: i.e. a vaccinated population of cattle mixed with an unvaccinated population of sheep and goats, nor in unvaccinated pigs. On 1st November 2001 the European Commission granted permission for Uruguay to export de-boned meat into Europe (3).
Teviot Scientific Consultancy © 2002 Teviot Scientific & www.land-care.org.uk
References1. Final report of a mission carried out in Uruguay from 25 to 29 June 2001 in order to evaluate the situation with regard to outbreaks of foot and mouth disease. European Commission Health & Consumer Protection Directorate - General. Food and Veterinary Office. (Download report [pdf]). 2. Final report of a mission carried out in Uruguay from 1 to 4 October 2001 in order to evaluate the controls in place over foot and mouth disease. European Commission Health & Consumer Protection Directorate - General. Food and Veterinary Office. (Download report [pdf]). 3. Commission Decision of 31 October 2001 amending Decision 93/402/EEC concerning animal health conditions and veterinary certification for imports of fresh meat from South American countries to take account of the animal health situation in Uruguay. (Download [pdf]). |
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