Selamectin for the prevention of canine Dirofilaria immitis infection: field efficacy in client-owned dogs in a high risk area.

Maria De Fátima Chicarino Varajão Moraes-Da-Silva,Livia Abdalla,Flavya Mendes-De-Almeida,Alexandre Merlo,Norma Vollmer Labarthe,Jonimar Pereira Paiva

doi:10.1186/s13071-016-1697-9

Maria De Fátima Chicarino Varajão Moraes-Da-Silva, Livia Abdalla + Show 4 more

Open Access

https://doi.org/10.1186/s13071-016-1697-9

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Abstract

BackgroundDog owners and veterinarians in small animal practices began to waive prevention of canine heartworm disease after heartworm infections seemed to have disappeared in Brazil. After 2013, infection rates rebounded, and an evaluation of the efficacy of chemoprophylactic drugs became necessary. Included in this re-evaluation was the efficacy of selamectin in client-owned dogs residing in a high infection-risk area.MethodsThe preventive efficacy of selamectin was evaluated by the topical application of selamectin to 24 client-owned dogs at the recommended rate (minimum of 6 mg/kg) by a veterinarian monthly for 36 months. Blood samples were collected before the first treatment and at the end of the study for testing to detect microfilariae by the modified Knott’s test and Dirofilaria immitis antigens using a commercial antigen test. Exposure to risk of heartworm infection was confirmed by the presence of infection in dogs living in low-income communities within a 2 km radius from the homes of dogs in the study. The dogs were managed according to routine practice by the owners within each household throughout the study.ResultsAll dogs tested negative by both tests after receiving topical treatment with selamectin monthly for 36 months. Testing of 204 dogs from the communities confirmed the presence of heartworm in the area by detection of microfilariae or D. immitis antigen in 44 dogs (21.6 %).ConclusionsTopical selamectin was 100 % effective for D. immitis prevention in 24 dogs that received monthly treatments by a veterinarian. Detection of heartworm infections in untreated dogs in the area suggests that clients need to be better informed regarding the prevalence of D. immitis and the importance of maintaining regular preventive treatments.

Highlights

IntroductionAfter 2013, infection rates rebounded, and an evaluation of the efficacy of chemoprophylactic drugs became necessary
Dog owners and veterinarians in small animal practices began to waive prevention of canine heartworm disease after heartworm infections seemed to have disappeared in Brazil
During the following years (2013–2014), the prevalence of canine heartworm infection spread to other areas where high infection rates had once been dramatically reduced with widespread use of preventive measures [8]

Summary

Introduction

After 2013, infection rates rebounded, and an evaluation of the efficacy of chemoprophylactic drugs became necessary. Included in this re-evaluation was the efficacy of selamectin in client-owned dogs residing in a high infection-risk area. Moraes-da-Silva et al Parasites & Vectors (2016) 9:407 had been previously present at an alarming rate before the regular use of macrocyclic lactones for heartworm prevention [7]. During the following years (2013–2014), the prevalence of canine heartworm infection spread to other areas where high infection rates had once been dramatically reduced with widespread use of preventive measures [8]. Several hypotheses were presented to account for the resurgence of heartworm infections, including owner’s noncompliance with chemoprophylaxis protocols or heartworm resistance to macrocyclic lactones [9, 10]

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