Treatment of lungworm infections in cats
Treatment of A abstrusus infection with off-label parasiticides has been described in research papers and textbooks. For example, the use of ivermectin for treating aelurostrongylosis is reported in single animals and limited case series, but this macrolactone has inconsistent activity. Two doses are described for off-label ivermectin, but care is required in kittens. Two doses of off-label abamectin, 300 µg/kg subcutaneously (SC), 2 weeks apart, have also been used for treating A abstrusus.
Several studies have evaluated the efficacy and safety of feline parasiticides against A abstrusus.
An oral paste containing 18.75% fenbendazole (Panacur; MSD Animal Health) is licensed in some countries (eg, UK) for the treatment of A abstrusus at a dosage of 50 mg/kg PO for 3 consecutive days, and this treatment regimen has an efficacy of 99.29%.
Two spot-on parasiticides, one containing imidacloprid 10% and moxidectin 1% (Advocate; Bayer Animal Health), and the other containing emodepside 2.1% and praziquantel 8.6% (Profender; Bayer Animal Health), were compared with the formulation containing oral fenbendazole in treating feline aelurostrongylosis. The emodepside 2.1%/praziquantel 8.6% spot-on (Profender) and the fenbendazole paste showed similar therapeutic performances (99.38% vs 99.29%), while the imidacloprid 10%/moxidectin 1% spot-on (Advocate) was 100% effective in stopping larval shedding and in curing clinical signs. This formulation (Advocate) is licensed in some markets (eg, Australia) for the treatment of cat aelurostrongylosis. Additionally, the adulticidal efficacy of emo depside has been demonstrated in two randomised, placebo-controlled experimental trials to be up to 99.2%. These studies showed that two spot-on administrations of emodepside 2 weeks apart are safe and efficacious against cat aelurostrongylosis.
Another macrocyclic lactone, selamectin (Stronghold; Zoetis), used topically at 18 mg/kg, reduced clinical signs after a single spot-on administration, while a second dose after 1 month ensured improvement in respiratory function and radiographic bronchial lesions. Selamectin at a topical dose of 6 mg/kg was effective in eliminating larvae from the faeces of a cat after 30 days; the same drug was effective in producing a clinical recovery and stopping larval shedding in 9/10 cats infected with A abstrusus.
Milbemycin oxime 4 mg/kg (plus praziquantel 10 mg/kg) (Milbemax; Novartis Animal Health) PO at 2 week intervals was also effective in stopping L1 elimination and resulted in resolution of clinical signs over a period of 6 weeks in a cat with clinical aelurostrongylosis.
A novel topical formulation containing fipronil 8.3% w/v, (S)-methoprene 10% w/v, eprinomectin 0.4% w/v and praziquantel 8.3% w/v (Broadline; Merial) was evaluated for efficacy against larval and adult A abstrusus in experimentally infected cats. This formulation is licensed in some countries for the treatment of A abstrusus. Using treatment time points based on the life cycle of A abstrusus in the cat (ie, from inoculated L3s to adult stages), the study demonstrated that eprinomectin has high efficacy against all A abstrusus stages; for example, 99.6% efficacy against adult stages in the feline definitive host. In cats naturally infected with A abstrusus, this formulation showed 90.5% efficacy based on larval counts.
Information on control options for troglostrongylosis in domestic cats is incomplete. The adminis - tration of imidacloprid 10%/moxidectin 1% (Advocate) in a cat appeared unsuccessful, but this may have been due to the severe clinical signs and extensive lung lesions already present at the point of referral. A kitten infected with T brevior returned negative scores upon both copromicroscopic and biomolecular examinations for 3 months after a single administration of Advocate and showed a corresponding improvement in severe cardiorespiratory signs.
A single administration of milbemycin oxime 2 mg/kg (Milbemax) was efficacious in stopping larval shedding in one cat with a subclinical mixed infection of A abstrusus and T brevior, but the same drug was effective only against A abstrusus in another cat from the same litter, which died due to infection with T brevior despite the treatment.
The topical formulation containing emodepside 2.1%/praziquantel 8.6% (Profender) recently showed promise in the treatment of two kittens with mixed lungworm infections (T brevior and either A abstrusus or C aerophila). Respiratory signs resolved after one or two administrations of the spot-on solution, and larval (T brevior and A abstrusus) and egg (C aerophila) shedding was also eliminated 2–4 weeks after treatment.
The spot-on containing eprinomectin (Broadline) proved 100% efficacious in stopping larval shedding in a few cats with natural T brevior infection. It recently showed 100% efficacy against developing larvae and adults of T brevior under experimental conditions.
Available data on the treatment of C aerophila infection in cats include reports on the efficacy of repeated administrations of a variety of dosages of injectable or oral levamisole and off-label abamectin.
Importantly, the spot-on formulation containing moxidectin 1% (Advocate), which was efficacious against aelurostrongylosis, demonstrated ~99.8% efficacy in stopping egg shedding and eliminating clinical signs in cats with lung capillariosis.
The safety and efficacy of the topical combination containing eprinomectin (Broadline) was evaluated against helminths, including Capillaria species, in domestic cats. An efficacy of 99.6% in reducing counts of Capillaria eggs was reported after treatment. Although no morphological identification of the eggs was performed, it was assumed that the vast majority were C aerophila. A very recent study has demonstrated that a single treatment with Broadline in naturally infected cats is able to reduce the C aerophila parasite burden and to lower or eliminate faecal egg shedding. Continued from page 14 Any respiratory sign in an at-risk cat (eg, free-roaming or kitten) should ring an alarm bell for clinicians working in lungwormendemic areas or with travelling pets.
In general, easy-to-apply topical parasiticides are a suitable choice for treating cat lungworms, because of safety and ease of administration, especially when multiple dosing is required.