Abstract
BackgroundLeishmania infantum and Dirofilaria immitis are among the most important canine vector-borne pathogens (CVBPs) of zoonotic concern in Europe. In endemic areas for both of these CVBPs, the use of systemic ectoparasiticides, such as afoxolaner (NexGard®; Boehringer Ingelheim Animal Health), may have the potential for controlling these infections. The aim of this study was to assess, for the first time, the insecticidal efficacy of NexGard® in decreasing the transmission of D. immitis and L. infantum to sheltered dogs living in a hyperendemic area, compared to the year before treatment, as well as its impact on the abundance of mosquito and sand fly populations.MethodsAll dogs (n = 179) enrolled in the study were divided into two groups based on their infection status at enrollment: a non-infected group (G1) and an infected group (G2; infected with D. immitis, L. infantum or both). The study was conducted from March 2020 to March 2021. In order to exclude all animals infected with L. infantum and D. immitis before March 2020 (sampling time: T0), dogs in G1 were sampled in June (T1; i.e. T0 + 90 days) and in October 2020 (T2; i.e. T0 + 210 days). From March to September 2020, all animals (G1 and G2) were weighed and treated monthly with NexGard®. Animals in G1 were tested for the last time in March 2021 (T3; i.e. T0 + 330 days) for assessing post-treatment incidence rate of infection and prevention efficacy.ResultsThe post-treatment incidence of D. immitis was 3.7% (1/27; 95% confidence interval [CI]: 0.2–18.1) and that of L. infantum was 3.6% (3/83; 95% CI: 1.0–10.1). Considering the annual incidence in 2019 and 2020, the protective efficacy against D. immitis and L. infantum infections was 94.2 and 64%, respectively. Of the female mosquitoes collected (n = 146), only one pool out of 50 tested positive for D. immitis DNA, whereas out of 1252 female Sergentomya minuta specimens collected, only four tested positive for L. infantum (0.3%).ConclusionsAfoxolaner is efficacious in decreasing the rate of transmission of both D. immitis and L. infantum; however, comparison of the pre- and post-treatment period demonstrated that there was a significant difference only in the seasonal incidences of D. immitis infection. Preventive measures are recommended throughout the year in endemic areas to reduce the risk of pathogen transmission to animals and humans.Graphical abstract
Highlights
Leishmania infantum and Dirofilaria immitis are among the most important canine vector-borne path‐ ogens (CVBPs) of zoonotic concern in Europe
According to their infection status at T1, group 1 (G1) dogs were considered to be uninfected for Dirofilaria (G1-D) and/ or Leishmania (G1-L), and group 2 (G2) dogs were considered to be infected by D. immitis and/or L. infantum (G2-D and G2-L, respectively) (Table 1)
The dogs in G1 which subsequently tested positive for L. infantum at T1 (n = 10) were considered to be infected before the sand fly season; the number of L. infantum-negative dogs (G1-L) in G1 was 83 (Table 1)
Summary
Leishmania infantum and Dirofilaria immitis are among the most important canine vector-borne path‐ ogens (CVBPs) of zoonotic concern in Europe. Leishmania infantum and Dirofilaria spp. are among the most important canine vector-borne pathogens (CVBPs) in Europe [1]. Dirofilaria immitis infective stage larvae are transmitted by mosquito species of several genera (including Aedes, Anopheles and Culex) [5], whereas L. infantum infective promastigotes are vectored by phlebotomine sand fly species of the genus Phlebotomus in the Old World [3, 6]. Dogs living in areas of D. immitis and L. infantum endemicity are more susceptible to the infection during the activity season of their vectors, which is mostly related to the average seasonal temperature [7, 8]
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