Blue Tongue (BT) or Bluetongue is a noncommunicable disease caused by a virus of the Reoviridae family, of the genus Orbivirus. It is spread under 24 viral serotypes. It is a disease that affects sheep, cattle, goats, dromedaries and wild ruminants. But, in general, it is only expressed clinically in sheep. It is a vector-borne disease transmitted by a mosquito Culicoides spp (in Morocco, it is C. imicola). Clinically BT is expressed by hyperthermia, inflammation, ulceration, erosion and necrosis of the oral mucosa, edema and sometimes cyanosis of the tongue, lameness due to inflammation of the podal bulge or pododermatitis and myositis. It can cause abortion and can end in death in 8 to 10 days, otherwise a slow cure with alopecia, sterility and stunting.
Legal and regulatory framework in Morocco
BT is a disease deemed legally contagious in Morocco by virtue of dahir Law no. 1-75-292 of 19/09/1977 and the decree of the Minister of Agriculture, Rural Development and Water and Forests no. 2018-01 of 19 chaabane 1422 (5 November 2001) on supplementary and special measures for the control of bluetongue.
National epidemiological situation
The disease first appeared in Morocco in September 2004 in the Gharb region. The virus responsible was serotype 4. The disease subsequently spread to other parts of the country and, in two months, the outcome of this episode was 230 outbreaks spread over 14 provinces (with 1,876 cases and an average mortality rate that did not exceed 1.3%). In September 2006, the Blue tongue reappeared in the East of the country. Laboratory investigations revealed a new serotype (serotype 1). A total of 500 households (2028 cases with an average mortality rate of 0.75%) were reported in 19 provinces. In 2007, the national epidemiological situation regarding this disease was characterized by favourable climatic conditions for the multiplication and the proliferation of insect vectors, These have encouraged the emergence of BT outbreaks over a large area of the national territory. Thus, during this year, 1076 outbreaks of this disease were reported in 43 provinces.
The BT strategy has three key components:
- Mass vaccination of sheep against serotypes circulating in the country (1 and 4);
- Sanitary management of reported BT outbreaks;
- Vector control in mosquito lodges;
monitoring of clinical signs of the disease.
Indeed, following the appearance of BT for the first time in 2004, vaccination campaigns for sheep were carried out against this disease (serotype 4 in 2004 and then Type 1 and 4 since 2006) at the level of risk zones (limited mainly to the northern part of the country). In 2008, the vaccination campaign was widespread throughout the Kingdom. The health veterinarians mandated were associated with this campaign. In addition, the management of reported BT outbreaks is based on the following health and medical measures:
- Sequestration of animals on affected farms;
- Isolation of sick animals;
- Prohibition of movement of animals to and from affected holdings.
- Demoustication and disinfection of affected farms. In this context, the establishment of an integrated approach to vector management is one of the prerogatives of the National Integrated Vector Control Management Committee, which brings together all the State departments involved.
- Vaccination of sheep in sensitive and epidemiologically linked flocks.
- Partial slaughter of affected animals.