Dirofilaria immitis: Genotyping random European sample and USA laboratory isolates at SNP markers associated with ML-susceptibility and resistance

Recent evidence has confirmed the development of ML-resistant isolates in the US which are genetically distinct from wild-type populations. Previous research clinically validated 10 single nucleotide polymorphism (SNP) molecular markers associated with these ML-resistant phenotypes isolated from the USA. In this study, three D. immitis US laboratory-maintained isolates: Berkeley, Georgia II, and WildCat; and seven randomly selected European D. immitis clinical samples, from Italy, Spain, and Hungary were analyzed. The samples tested were fresh microfilaria (mf) in blood or adult female worms preserved in ethanol. After DNA extraction, each sample underwent MiSeq sequencing of regions encompassing the top 9 of 10 SNP sites previously associated with ML susceptibility and resistance.