Molecular detection of Culicoides spp. and Culicoides imicola, the principal vector of bluetongue (BT) and African horse sickness (AHS) in Africa and Europe.

This research focuses on developing a rapid identification test for Culicoides imicola, a biting insect responsible for spreading African Horse Sickness and Bluetongue diseases in livestock, using a DNA-based technique, which is vital in controlling and preventing outbreaks of these diseases particularly in susceptible regions.

Background

• Bluetongue (BT) and African Horse Sickness (AHS) are infectious diseases that impact ruminants and horses respectively. Both are transmitted by Culicoides imicola, a biting midge prevalent in Africa and Europe.
• Recent re-emergence of Bluetongue in the Mediterranean Basin has had significant effects on the sheep industry. However, the disease has not spread to mainland France and Spain.
• Efforts to monitor the presence of the biting midge have included creating a light-trap network in southern mainland France in 2002. As traditional methods of identifying Culicoides, based on their morphology, are time-consuming and complex, this research sets out to devise a more efficient identification technique.

The Research

• The research focuses on the development of an ITS1 rDNA polymerase chain reaction (PCR)-based diagnostic assay to accurately identify Culicoides imicola among the collected insects. This technique is based on the greater similarity of nuclear ribosomal DNA (rDNA) within species than between species, which makes it a useful tool for species diagnostic tests.
• Data from Genbank and EMBL databases were used to identify regions in the rDNA that are highly conserved, and PCR primers were designed accordingly to isolate genus-specific fragments. In order to specifically identify C. imicola, additional forward primer was designed and used in combination with a prior designed reverse primer.

Results and Implication

• The primers designed in the study have proven to be both highly specific and sensitive. They allowed for a rapid diagnostic separation of C. imicola from other Culicoides species.
• The development of this rapid identification method is an important step forward in controlling and preventing the spread of BT and AHS by assisting quick identification and control of the vector Culicoides imicola, especially in areas considered at high risk.