Abstract
BackgroundParasitic 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.MethodsSixteen 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.ResultsThe 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.ConclusionThese results indicate that Advocate® spot-on is a safe and effective option for treating cats infected by T. brevior.Graphical
Highlights
Parasitic bronchopneumonia in domestic cats in Europe, which can manifest with moderate to severe clinical signs, is frequently caused by Troglostrongylus brevior
6/8 and 8/10 control cats in Study 1 and 2, respectively, shed L1 up to necropsy, while at the first post-treatment parasitological examination performed on study day (SD) 35 (Study 1) and SD 48 (Study 2) the larval shedding ceased in all Group 2 (G2) cats
In the group of treated cats (G2), marbled and inhomogeneous pulmonary tissue was observed in one cat and the presence of a 0.2 × 0.2 mm small, rough nodule was observed in another cat, while the remaining eight cats did not show any pulmonary lesions
Summary
Parasitic bronchopneumonia in domestic cats in Europe, which can manifest with moderate to severe clinical signs, is frequently caused by Troglostrongylus brevior. In the last decade the closely related crenosomatid Troglostrongylus brevior, previously related only to wild felids, has been regarded as a primary cause of verminous bronchopneumonia in cat populations of Europe, mainly in countries of the Mediterranean basin [1, 2]. In many regions of Europe, T. brevior is recognized as a major respiratory parasite of both domestic cats and wildcats, existing in sympatry with A. abstrusus, and in some territories troglostrongylosis is more prevalent than aelurostrongylosis in domestic cats [5,6,7,8,9,10,11,12]
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