Efficacy of imidacloprid 10%/moxidectin 1% spot-on formulation (Advocate®) in the prevention and treatment of feline aelurostrongylosis

Efficacy of Bravecto® Plus spot-on solution for cats (280 mg/ml fluralaner and 14 mg/ml moxidectin) in the prevention of feline Aelurostrongylus abstrusus infection evaluated in a multi-diagnostic approach

BACKGROUND

Aelurostrongylus abstrusus is one of the most important respiratory nematodes of felines. Infections may lead to respiratory clinical signs with varying severity or even death, emphasizing the need for preventive treatment of cats with outdoor access to circumvent patent infections.

METHODS

Therefore, the preventive efficacy of a spot-on formulation of 280 mg/ml fluralaner and 14 mg/ml moxidectin (Bravecto® Plus spot-on solution for cats, MSD) against A. abstrusus was evaluated in a negative controlled, randomized and partially blinded efficacy study with 28 purpose-bred cats in a non-terminal design. In three different treatment regimes, the minimum recommended dose of 40 mg fluralaner and 2.0 mg moxidectin/kg bodyweight (BW) was administered once at 12, 8 or 4 weeks (study group G1, G2 and G3, respectively) prior to experimental infection with 300 third-stage A. abstrusus larvae, while G4 served as placebo-treated control.

RESULTS

From 30 to 46 days post infection (dpi; SD 114 to 130), faeces were sampled to monitor first-stage larvae (L1) excretion for efficacy determination. Secondary efficacy criteria, including respiratory parameters, serological antibody levels and computed tomography (CT) findings, were assessed once before enrolment (SD -7 to -1) and before infection (SD 75 to 83). After infection, CT evaluation was performed once at 47-50 dpi (SD 131 to 134), and respiratory parameters and antibody levels were regularly assessed twice or once a week, respectively (1 up to 78 dpi, SD 85 up to 162). All animals in the control group excreted L1 by 33-37 dpi and remained positive throughout the study period from 41 to 46 dpi (SD 125 to 130). In the treatment groups, only one animal each of G1 and G2 excreted L1 at two consecutive days, and four cats of G1, two of G2 and three of G3 were positive on single occasions. While the geometric mean (GM) of the maximum number of excreted L1 per 5 g of faeces was 7380.89 in the control group (G4), GMs were significantly lower in the treatment groups with 1.63 in G1, 1.37 in G2 and 0.79 in G3. Thus, based on GMs, the reduction in excreted L1 exceeded 99.9% in all three treatment groups. Based on CT severity scores, all lungs of the animals of the control group showed severe pulmonary changes post infection, whereas lungs of the cats of the treatment groups were either unaltered (4 animals), mildly (11 animals), or moderately altered (5 animals). Moreover, seroconversion was observed in all cats of the control group, but not in those of the treatment groups.

CONCLUSIONS

The combination of diagnostic methods used in this non-terminal study yielded coherent and reliable results. A single administration of Bravecto® Plus spot-on solution for cats was well tolerated and effective in the prevention of aelurostrongylosis for at least 12 weeks.

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

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

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

An infection with the cat lungworm, Aelurostrongylus abstrusus, can be subclinical, but it can also cause severe respiratory clinical signs. Larvae excretion, antibody levels, clinical assessment findings of the respiratory system and diagnostic imaging findings were recorded and compared for six cats with experimental aelurostrongylosis. In five cats, patency started 33-47 days post infection (pi), but two cats excreted larvae only in long intervals and low numbers. Positive ELISA results were observed in four cats with patent aelurostrongylosis, starting between five days before and 85 days after onset of patency. One seropositive cat remained copromicroscopically negative. Mild respiratory signs were observed in all cats examined. A computed tomographic (CT) examination of the lungs displayed distinct alterations, even in absence of evident clinical signs or when larvae excretion was low or negative. The thoracic radiograph evaluation correlated with the CT results, but CT was more distinctive. After anthelmintic treatment in the 25th week post infection, pulmonary imaging findings improved back to normal within 6-24 weeks. This study shows that a multifaceted approach, including diagnostic imaging, can provide a clearer diagnosis and monitoring of disease progression. Furthermore, a CT examination provides an alternative to post mortem examination and worm counts in anthelmintic efficacy studies.

Cat Respiratory Nematodes: Current Knowledge, Novel Data and Warranted Studies on Clinical Features, Treatment and Control

The nematodes Aelurostrongylus abstrusus, Troglostrongylus brevior and Capillaria aerophila are the most important parasites inhabiting the airways of cats. They are receiving growing attention from academia, pharmaceutical companies and veterinarians, and are now considered a primary cause of respiratory diseases in feline clinical practice and parasitology. In the past few years, several studies have been conducted in both natural and experimental settings to increase knowledge, provide new insights and fill gaps on respiratory parasitoses of cats. Awareness and knowledge of clinical scenarios towards appropriate and timely diagnosis and prompt and efficacious treatment options have become a priority to investigate. At the same time, chemopreventative approaches have been evaluated to assess the geographical spreading of these parasites and the rise in the number of clinical cases in cat populations of different countries. Given the intense accumulation of novel data, this review presents and discusses the state of the art and the latest updates on the clinical features, treatment, and control of major respiratory parasitoses of cats. Moreover, food for thought is also provided with the aim of spurring on new studies in the near future.

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

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.