由线虫引起的丝虫病是狗最重要的寄生虫之一。感染的治疗时间很长,复杂,风险和昂贵。相反,预防很容易,安全,和有效的,它是通过大环内酯(MLs)的给药。近年来,在美国南部已经描述了对MLs具有抗性的D.immitis菌株,引起人们对可能出现的担忧,或在世界其他地区传播。本研究描述了欧洲一只狗的首例ML抗性D.immitis。狗来到罗马,意大利,2023年来自美国。抵达意大利后不到6个月,这只狗的D.immitis循环抗原和微丝虫检测呈阳性,尽管它在到达后每月接受ML米尔贝霉素肟(加异恶唑啉)。微丝菌抑制试验提示为耐药菌株。通过基于液滴数字PCR的双链体测定法检查了微丝菌DNA,该双重测定法针对单核苷酸多态性(SNP1,SNP2,SNP3,SNP7)的四个标记位置,这些标记位置将抗性与易感分离株区分开。遗传分析表明,微丝虫在SNP1和SNP7位置具有ML抗性基因型,与抗性菌株兼容。这只狗到达欧洲后不太可能感染,虽然从生物学和流行病学上讲,这只狗从美国进口到欧洲时已经被感染了。本报告强调了ML抗性D.immitis菌株进口并可能在欧洲和世界其他地区传播的现实风险。监视从一个地区到另一个地区的狗,特别是如果它们来自ML抗性有据可查的地区,势在必行。科学家,从业者,宠物主人应该意识到这种风险,并对ML抵抗保持警惕,以监测和减少抗药性D.immitis的传播。
Heartworm disease caused by the nematode Dirofilaria immitis is one of the most important parasitoses of dogs. The treatment of the infection is long, complicated, risky and expensive. Conversely, prevention is easy, safe, and effective and it is achieved by the administration of macrocyclic lactones (MLs). In recent years, D. immitis strains resistant to MLs have been described in Southern USA, raising concerns for possible emergence, or spreading in other areas of the world. The present study describes the first
case of ML-resistant D. immitis in a dog in Europe. The dog arrived in Rome, Italy, from USA in 2023. Less than 6 months after its arrival in Italy, the dog tested positive for D. immitis circulating antigen and
microfilariae, despite it having received monthly the ML milbemycin oxime (plus an isoxazoline) after arrival. The
microfilariae suppression test suggested a resistant strain.
Microfilariae DNA was examined by droplet digital PCR-based duplex assays targeting four marker positions at single nucleotide polymorphisms (SNP1, SNP2, SNP3, SNP7) which differentiate resistant from susceptible isolates. The genetic analysis showed that
microfilariae had a ML-resistant genotype at SNP1 and SNP7 positions, compatible with a resistant strain. It is unlikely that the dog acquired the infection after its arrival in Europe, while it is biologically and epidemiologically plausible that the dog was already infected when imported from USA to Europe. The present report highlights the realistic risk of ML-resistant D. immitis strains being imported and possibly transmitted in Europe and other areas of the world. Monitoring dogs travelling from one area to another, especially if they originate from regions where ML-resistance is well-documented, is imperative. Scientists, practitioners, and pet owners should be aware of the risk and remain vigilant against ML-resistance, in order to monitor and reduce the spreading of resistant D. immitis.