Efficacy of a spot-on combination containing 10% w/v imidacloprid and 1% w/v moxidectin for the treatment of troglostrongylosis in experimentally infected cats

Abstract

Background Parasitic bronchopneumonia in domestic cats in Europe, which can manifest with moderate to severe clinical signs, is frequently caused by Troglostrongylus brevior. Data on epizootiological and clinical relevance of cat troglostrongylosis have been published in the last decade but treatment options are still limited. Promising effectiveness data have been generated from clinical cases and field trials for a spot-on formulation containing 1% w/v moxidectin and 10% w/v imidacloprid (Advocate®, Elanco Animal Health). Therefore, two studies have been conducted to confirm under experimental conditions the efficacy of moxidectin 1% contained in Advocate® for the treatment of cat troglostrongylosis. Methods Sixteen and 20 cats experimentally infected with T. brevior were included in two separate studies, i.e., Study 1 and 2, respectively. Cats were infected with T. brevior third-stage larvae via gastric tube. In both studies cats were randomized to untreated (control, Group 1) and treatment (Group 2) groups. In Study 1 and Study 2, the two groups comprised eight and 10 cats each. Treated cats received Advocate® spot-on twice at a 4-week interval. The primary efficacy criterion was the number of viable adult T. brevior counted at necropsy. Throughout the trial, the fecal shedding of first-stage larvae (L1) was assessed in treated and untreated control cats. Results The experimental model was successful in both studies, as all cats started shedding T. brevior L1 within 25 days post-infection. At necropsy, T. brevior adults were found in 4/8 and 4/10 cats of the control groups in Study 1 and 2, respectively, while none of the treated cats harbored adult worms. The necropsy worm counts in controls did not meet relevant guideline requirements for adequacy of infection, with fewer than six infected cats in the control groups, thus limiting conclusions on treatment efficacy. The fact that 6/8 and 8/10 control cats in Study 1 and 2, respectively, shed L1 up to necropsy while larval shedding ceased in all treated animals after the first treatment provides supporting evidence on the level of efficacy. No remarkable adverse events were recorded in the two studies. Conclusion These results indicate that Advocate® spot-on is a safe and effective option for treating cats infected by T. brevior. Graphical Abstract

Efficacy of two topical combinations containing emodepside plus praziquantel, and emodepside plus praziquantel plus tigolaner, for the treatment of troglostrongylosis in experimentally infected cats

“…Some cats of Group 2 and Group 3 presented respiratory signs after treatment ( Table 1 ). This feature is consistent with previous data registered in experimental ( Traversa et al., 2022 ) and natural ( Traversa et al., 2019b ) studies, in which study animals showed a temporary worsening of their clinical conditions and respiratory distress, likely due to an inflammatory response to the death of adult T. brevior caused by the treatment. Moreover, a few treated cats occasionally presented mild respiratory signs, i.e.…”

“…Other parasiticides showed their efficacy in terms of larval shedding and remission of clinical signs in cats infected with T. brevior either in monospecific or in mixed infection with the closely related cat lungworm Aelurostrongylus abstrusus . This applies to the macrocyclic lactones milbemycin oxime in single clinical cases ( Crisi et al., 2017 ) or moxidectin in clinical reports and studies ( Crisi et al., 2015 , 2017 ) and in large trials with naturally and experimentally infected cats ( Diakou et al., 2019 ; Traversa et al., 2022 ). Although the efficacy of oral fenbendazole against T. brevior is suggested in some guidelines ( Pennisi et al., 2015 ), this has been not factually evaluated nor demonstrated ( Morelli et al., 2021 ).…”

“…The number of shed L1 was very low ( Table 2 , Table 3 , Table 4 ), thus it can be argued that these were larval stages which hatched from eggs released prior to the second treatment or by deceasing worms. Accordingly, it has been shown that cats infected with T. brevior may shed larvae up to 10 days post-treatment with macrocyclic lactones ( Cavalera et al., 2019 ; Traversa et al., 2022 ). As adult worms reside in the deep airways, clearance of the lungs from eggs or larvae requires some time.…”

“…Infective L3 were obtained on Day 0 and processed as follows. Snails were artificially digested as described ( Morelli et al., 2020 ; Traversa et al., 2022 ). The digested material was then filtered using a 200 μm sieve and centrifuged at 300× g for 10 min.…”