Efficacy of Bravecto® Plus spot-on solution for cats (280 mg/ml fluralaner and 14 mg/ml moxidectin) for the prevention of aelurostrongylosis in experimentally infected cats

Abstract

Background The feline lungworm Aelurostrongylus abstrusus affects the lower respiratory tract in cats worldwide. As infections may lead to chronic respiratory changes or even death, preventive treatment in cats with outdoor access is warranted. Methods The preventive efficacy of a spot-on solution (Bravecto® Plus spot-on solution for cats, MSD) against cat aelurostrongylosis was evaluated using three different preventive treatment regimes in a negative controlled, randomized and partially blinded laboratory efficacy study with 31 purposed-bred cats. The minimum recommended dose of 2.0 mg moxidectin + 40 mg fluralaner/kg bodyweight was applied once 12 (Group [G]1), 8 (G2) or 4 (G3) weeks before experimental infection with 300 third-stage larvae (L3) of A. abstrusus. Another group served as untreated control (G4). Individual faecal samples were analysed as of day 30 post infection (pi) to monitor larvae excretion. Necropsy was performed at days 47–50 pi. The lungs were examined macroscopically for pathological findings and (pre-)adult worms were counted to assess preventive efficacy. Results Beginning at day 32–40 pi, all cats of the control group were constantly shedding larvae of A. abstrusus, whereas only one animal of G1 excreted larvae at several consecutive days. In addition, two cats of G1 and G3 and three of G2 were positive on a single occasion. The geometric mean (GM) of the maximum number of excreted larvae was 7574.29 in the control group compared to 1.10 (G1), 1.19 (G2) and 0.53 (G3), resulting in a GM reduction of > 99.9% in all treatment groups. All lungs of the control animals showed severe or very severe alterations at necropsy, while in 94.44% of the treated cats lung pathology was rated as absent or mild. The GM number of (pre-)adult A. abstrusus retrieved from the lungs was 26.57 in the control group, 0.09 in G1 and 0.00 in G2 and G3. Thus, GM worm count reduction was 99.66% in G1 and 100% in G2 and G3. Conclusions A single application of Bravecto® Plus spot-on solution at a dose of 2.0 mg moxidectin + 40 mg fluralaner/kg bodyweight reliably prevents cat aelurostrongylosis for at least 12 weeks.

Do All Roads Lead to Rome? The Potential of Different Approaches to Diagnose Aelurostrongylus abstrusus Infection in Cats

“…The observed prepatency period of 33–47 days was similar to those observed in other experimental A. abstrusus studies ranging between 31 and 41 [ 13 , 16 ], or 40 and 50 [ 36 ] days, respectively. However, in the latter study, individual faecal samples were collected only from day 40 pi onwards.…”

“…In addition, the respiratory frequencies may be skewed to a certain extent, as the cats became excited or started purring when they became aware of the examiner. Nevertheless, previous studies did not find statistically significant differences as well, though reporting a trend to an increased respiratory frequency in A. abstrusus infected cats [ 13 , 16 ]. Distinct clinical signs such as coughing were observed only in three of the cats, and only on single occasions.…”

“…However, in the latter study, individual faecal samples were collected only from day 40 pi onwards. In comparison to an anthelmintic efficacy study using the same A. abstrusus isolate and the same inoculation dose of 300 L3 [ 16 ], the maximum LpG values detected in the present study were considerably lower than those of the untreated control animals in the efficacy study, which ranged between 10.8 and 9180.0 LpG with a mean value of 1514.9 LpG. One reason might be that the cats in the efficacy study were about nine months of age upon infection, whereas here, the age of the cats extends from 13 to 105 months.…”

“…This setup was chosen to assess whether this has a comparable infective potential to L3 used immediately after digestion. If so, this additional migration step would help to remove snail tissue residues in the inoculum, which may be the reason for the frequently reported vomiting of cats after inoculation [ 13 , 16 , 36 , 37 , 38 ]. Here, vomiting after inoculation was not observed in any of the cats.…”

“…Feline aelurostrongylosis can clinically manifest as granulomatous pneumonia with clinical signs such as coughing, sneezing and nasal discharge, or, in more severe cases, tachypnea or dyspnea and apathy, stunting or even death [ 11 , 12 , 13 , 14 ]. However, infections may also remain without noticeable respiratory signs despite the presence of lung pathology [ 15 , 16 , 17 ]. Lungworm infections are probably underdiagnosed or misdiagnosed in both subclinically infected and cats with clinical signs, as similar respiratory signs have been associated with feline asthma or other bronchial infectious diseases, and because treatment for feline asthma often eases the clinical appearance of aelurostrongylosis [ 18 ].…”