Chu Yi, Campbell Elyssa, Dzimianski Michael, Evans Christopher C, Pulaski Cassan, Sakamoto Kaori, Moorhead Andrew R
Department of Infectious Disease, College of Veterinary Medicine, University of Georgia, Athens, GA, USA.
Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA.
Parasitol Res. 2025 Jun 3;124(6):59. doi: 10.1007/s00436-025-08506-z.
Dirofilaria immitis, also known as canine heartworm, contains an endosymbiont, Wolbachia, in all life stages. The antibiotic, doxycycline, has been incorporated into heartworm treatment protocols to eliminate Wolbachia. Previous studies indicate that subsequent infection cannot be established using viable third-stage larvae (L3) developed from doxycycline-treated microfilariae (mf). The stages in which the development of larvae is impacted by doxycycline remain unknown. We examined the impact of doxycycline on the third-stage to fourth-stage larval molt, as it is the first molt of D. immitis after it invades the vertebrate host. Microfilaremic blood was collected weekly from D. immitis-infected dogs with or without doxycycline treatment at 10 mg/kg as recommended by the American Heartworm Society. Blood was collected weekly until the end of doxycycline treatment. The blood was used for L3 production and mf isolation. Wolbachia levels in mf and L3 were measured using real-time quantitative PCR. L3 were cultured in vitro for 9 days to assess whether molting occurred. The Fisher's exact test and Bonferroni correction were used for statistical analysis. The molting of L3 from the doxycycline-treated groups did not show a significant difference compared to the L3 from the control group at weeks 0, 1, 2, 3, and 4. The Wolbachia levels in mf and L3 decreased starting from 7 days post-treatment and remained less than five percent of controls throughout the treatment. Doxycycline treatment can eliminate Wolbachia in both mf and subsequently developed L3. The molts of the mf to L3 in the mosquito and the L3 to L4 molt in vitro do not appear to be impacted by the reduction or elimination of Wolbachia.
犬恶丝虫，也被称为犬心丝虫，在其所有生命阶段都含有一种内共生菌——沃尔巴克氏体。抗生素强力霉素已被纳入心丝虫治疗方案以消除沃尔巴克氏体。先前的研究表明，使用由强力霉素处理过的微丝蚴（mf）发育而来的活的第三期幼虫（L3）无法建立后续感染。强力霉素影响幼虫发育的阶段仍不清楚。我们研究了强力霉素对第三期到第四期幼虫蜕皮的影响，因为这是犬恶丝虫侵入脊椎动物宿主后的首次蜕皮。按照美国心丝虫协会的建议，每周从感染犬恶丝虫且接受或未接受10mg/kg强力霉素治疗的犬只身上采集微丝蚴血症血液。每周采集血液，直至强力霉素治疗结束。这些血液用于生产L3和分离mf。使用实时定量PCR测量mf和L3中的沃尔巴克氏体水平。将L3在体外培养9天以评估是否发生蜕皮。采用Fisher精确检验和Bonferroni校正进行统计分析。在第0、第1、第2、第3和第4周，与对照组的L3相比，强力霉素处理组的L3蜕皮没有显著差异。mf和L3中的沃尔巴克氏体水平从治疗后7天开始下降，在整个治疗过程中一直低于对照组的5%。强力霉素治疗可以消除mf和随后发育的L3中的沃尔巴克氏体。mf在蚊子体内发育为L3以及L3在体外发育为L4的蜕皮似乎不受沃尔巴克氏体减少或消除的影响。
