Polymerase chain reaction-identification of Dirofilaria repens and Dirofilaria immitis.

On the basis of known DNA sequences of Dirofilaria repens and D. immitis we designed specific primers for the amplification by Polymerase Chain Reaction (PCR) of the DNA from the two species. The PCR-based identification was found to be unambiguous and allowed specific diagnosis of microfilariae in blood samples, of developing larvae in the mosquito vector and of immature adults in bioptic material, overcoming the serious constraints of the morphological separation of these filarial parasites at the pre-adult stages. The technique was found to be very sensitive and applicable to samples stored either dry or in various preservation media, with the exception of formalin. The reliable identification of D. repens and D. immitis from bioptic material is expected to greatly enhance the chances of detecting human infections and to further clarify the role of the two parasites as pathogens of man. The possibility of routine identification of developing larvae in the vector will substantially improve the perspectives for epidemiological investigations, particularly in Southern European regions, such as Italy, where the two nematode species are largely sympatric.