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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Food Animal Metabolism Research » Research » Publications at this Location » Publication #426041
Research Project: Detection and Fate of Environmental Chemical and Biological Residues and their Impact on the Food Supply

Location: Food Animal Metabolism Research

Title: Efficacy of injectable versus topical formulation of ivermectin against Anopheles stephensi mosquitoes feeding on different body locations of treated Holstein calves

Author
item DREYER, STACI - Valley City State University
item MOLDEN, TODD - North Dakota State University
item BAUER, M - North Dakota State University
item Smith, David
item Pfaff, Colleen
item VAUGHAN, JEFFERSON - University Of North Dakota

Submitted to: Parasites & Vectors
Publication Type: Pre-print Publication
Publication Acceptance Date: 12/20/2025
Publication Date: 1/31/2026
Citation: Dreyer, S.M., Molden, T., Bauer, M., Smith, D.J., Pfaff, C.M., Vaughan, J.A. 2026. Efficacy of injectable versus topical formulation of ivermectin against Anopheles stephensi mosquitoes feeding on different body locations of treated Holstein calves. Parasites & Vectors. 19:62-73. https://doi.org/10.1186/s13071-025-07225-9.
DOI: https://doi.org/10.1186/s13071-025-07225-9

Interpretive Summary: In many tropical areas, cattle indirectly contribute to the maintenance of malaria even though they are not directly involved in the transmission cycle. Rather, cattle often serve as important blood sources for the Anopheles mosquito vector and thus may contribute to high vector populations. In such cases, protection of cattle against Anopheles mosquitoes may represent a form of malaria vector control and help lower the risk of malaria transmission to humans. This study was designed to test the effectiveness of pour-on or subcutaneous ivermectin treatment of calves on the survival and fertility of Anopheles mosquitoes which had access to treated animals. Either treatment on calves effectively killed mosquitoes for up to 9 days, but ease with which the pour-on formulation is applied and its effectiveness for up to 23 days after application makes it an attractive option for livestock producers. Refinement of topical ivermectin application (most effective anatomical locations) may allow for further optimization of treatment. Such optimization will factor into zoophagic vector management strategies.

Technical Abstract: Both topical and injectable formulations of ivermectin significantly reduced An. stephensi survival for up to 9 days after treatment of calves. Topical formulation of ivermectin applied to the back of the calves significantly reduced the survival of An. stephensi that fed on the back for up to 23 days after treatment, but not for mosquitoes that fed concurrently on the belly or the leg of topically treated calves. This suggests that a portion of topically applied ivermectin may be sequestered at the site of application in the surrounding skin or adipose and exert a localized mosquitocidal effect even after plasma levels of ivermectin have diminished. Calves treated with both formulations produced sublethal effects on surviving mosquitoes, significantly inhibiting normal blood digestion and ovarian development for up to 14 days after treatment.Mosquitoes were less likely to feed on topically treated calves, implying that topical application may confer some mild repellency.