Clavelee Ovine


Also known as ovine smallpox, sheep pox, Viruela ovine (in Spanish), Variolo ovino (in Italian) and Jedri (in arabeجذري الأغنام), clavelee is a highly contagious, virulent, inoculable and specific viral disease of sheep. It is due to a virus of the Poxviridae family.

Legally, the ovine clavelee is considered contagious by virtue of the Dahir law no. 1-75-292 of 19 September 1977 and the decree of the Minister of Agriculture, Rural Development and Water and Forests no. 2019-01 of 19 chaabane 1422 (5 November 2001) on additional and special measures for the control of ovine clavelea.

It is of economic importance especially in Africa and in the countries of the Middle East and the Maghreb in view of the losses it may cause in the form of:

  • Direct losses characterized by abortion, relatively high mortality among young people and depreciation of the economic value of hides and wool;
  • Indirect losses related to the cost of prophylaxis, reduced production capacity and barriers to the marketing and export of animals.

National health situation and control programme

In Morocco, clavele has been rampant in enzootic form for decades. At present, and thanks to the regular control programmes undertaken by the national veterinary services, the incidence of the disease has clearly decreased and the disease is generally under control.

Indeed, during the years 1970-80, ovine clavelee was present in almost the entire national territory and the number of cases reported annually was in the thousands of sheep affected. During this period, the control strategy was based on anti-washer vaccination (with an average vaccination rate of 50% of the national sheep population) and aimed in particular at controlling the disease in a first phase. The second phase, undertaken in the early 1990s, aimed at the eradication of ovine clavelea on the national territory by mass vaccination (using a vaccine developed in Morocco by the Société d’Etat Biopharma)Annual, generalized to the national sheep population with satisfactory vaccination coverage (at least 80% of the population of vaccination age). As a result, the number of cases and outbreaks declined significantly from year to year, attributed to satisfactory vaccination coverage, particularly in 1995, 1996 and 1997.

From 1999 onwards, the change in the epidemiological situation of the disease, characterized by a significant decrease in the number of recorded keyhole outbreaks and the number of cases per outbreak, led to the adoption of regionalised vaccination in high-risk (eastern) areas. The other provinces, which were not affected by this vaccination, thus constituted health surveillance zones vis-à-vis the clavelee.

However, from 2001 onwards, a resurgence of keyhole outbreaks was recorded, which again forced a return to widespread vaccination of the sheep herd from 2002.

Since 2004, and after the reappearance of a few scattered outbreaks of the disease, the vaccination against the clavelee became biennial and generalized to the entire sheep herd (the vaccine used confers immunity that can reach more than 24 months in vaccinated animals). The authorized veterinary health officers are involved in this campaign.

In 2007 the widespread vaccination campaign of sheep against the clavelee was coupled with that of the Blue Tongue at the risk zones using a bivalent vaccine.

Since 2008 and following the outbreak of small ruminant plague for the first time in Morocco, the fight against the disease has focused on the management of declared outbreaks of the disease through vaccination around outbreaks, restrictions on the movement of animals, the slaughter of the affected animals, the disinfection of the affected farms and the compensation of the farmers concerned, in addition to continuous surveillance of the disease at national level.

In 2011, the generalization of vaccination against clavelee was continued and had as objective to strengthen the acquired immunity in sheep. In 2013, a widespread vaccination campaign was launched again with the same objectives as in 2011. The authorized veterinary health officers are involved