Chapter 1

Contents - Previous - Next

1. Geographical distribution

1. Geographical distribution

1.1 United kingdom
1.2 Other countries

1.1 United kingdom

BSE was first recognized in the United Kingdom and it is only there that a larges-cale epidemic has occurred. By the end of 1990 well over 20 000 cases of BSE had been confirmed in England Scotland and Wales. The incidence of herds with at least one confirmed case was about 10 percent and the incidence within affected herds was approximately two cases per 100 adults per annum. The overall annual incidence was four cases per 1 000 adults. In Northern Ireland, the total number of BSE cases was around 150. Table 2 gives figures up to the middle of June 1991.

The epidemic started simultaneously in several parts of the country (see Fig. 1) and cases have been distributed over a wide area and in every county ever since (Wilesmith, 1991). The disease occurs predominantly in dairy herds (see The vehicle of infect ion p. 20).

TABLE 2. Cumulative total number of histologically confirmed cases of BSE in various countries up to 14 June 1991

United Kingdom 29 907
Northern Ireland 203
Republic of Ireland 39
Switzerland 5
France 4
Oman 2*
Falkland Islands 1*

*All cases in Oman and the Falkland Islands occurred in cattle imported from the United Kingdom Source: MAFF. UK.

However, there is marked regional variation in the occurrence of BSE, with a preponderance of cases in the south and east. At the end of 1989 about half of all cases had occurred in just seven counties in the southwest.

FIGURE 1 Geographical distribution of the first suspected cases of BSE (April 1985 to December 1986)

This pattern is simply a reflection of the number of dairy herds at risk (Matthews 1 990).

The proportion of dairy herds with BSE also shows marked regional variation. In the period from November 1986 (when BSE was first recognized) to July 1989 the percentage of dairy herds with at least one confirmed case of BSE was 12.6 percent in the south, 3.9 percent in the Midlands, 2.8 percent in the north of England and 1.8 percent in Scotland (Wilesmith. Ryan and Atkinson, 1991). Figure 2 gives a more up-to-date pattern which indicates a geographical variation in the exposure of cattle to infection. Epidemiological studies have provided explanations for this variation (see The north-south gradient, p. 24).

FIGURE 2 Cumulative proportion of dairy herds with BSE in home-bred cattle (November 1986 to August 1990)

1.2 Other countries

Table 2 shows that several cases of BSE have occurred in the Republic of Ireland (Basset and Sheridan, 1989). Some of these were associated with the importation of live animals or meat and bone meal from the United Kingdom. Although scrapie is also present in the Republic, and large amounts of meat and bone meal are produced there, not much is fed to Irish cattle. It is unclear whether any cases of BSE in the country are due to locally produced meat and bone meal.

Two cases of BSE have occurred in Jersey cows in Oman (Carolan, Wells and Wilesmith, 1990). These animals were part of a consignment of 14 pregnant heifers imported from England in 1985. The heifers were born on the same farm in 1983 and investigations into their feeding history suggest exposure to infection during calfhood, before export. The herd of origin has also experienced cases of BSE (Wilesmith personal communication). Likewise BSE has occurred in the Falkland Islands in an animal imported from the United Kingdom.

The first case of BSE in continental Europe was reported in November 1990 in a six-year-old Holstein cross that was born and reared in Switzerland (Anon. 1 990a). There have subsequently been other Swiss cases (see Table 2). Meat and bone meal had been fed to these animals but its origin is not known. Switzerland has small populations of sheep and goats. Scrapie has been recorded in a goat but not in sheep.

A case of BSE in Brittany was announced by the French authorities in February 1991 (Anon. 1991a) followed by several other cases (see Table 2). A teed source of infection is suspected. The infection may have been imported or it could have originated in France, a country with a large sheep population and endemic scrapie in several regions.

Contents - Previous - Next