Safety of imidacloprid plus moxidectin topical solution applied to cats heavily infected with adult heartworms (Dirofilaria immitis)

Feline asthma and heartworm disease: Clinical features, diagnostics and therapeutics

PRACTICAL RELEVANCE

For feline practitioners, the cat with a cough or respiratory distress and thoracic radiographs with a bronchial or bronchointerstitial pattern suggests lower airway disease. Two important differentials, allergic asthma and heartworm disease (HWD), have many overlapping clinicopathologic features, but also clear and important differences in terms of cause and disease progression, treatment and prognosis. Notably, asthma is readily treatable and HWD is preventable.

CLINICAL SIGNIFICANCE

Feline HWD comprises two clinical syndromes: the comparatively recently described heartworm-associated respiratory disease (HARD) and adult HWD. The former is much more common; very few cats with HARD develop adult HWD. In HARD, following death of immature worms, pulmonary lesions may improve over time ('self-cure'). Lesions of adult HWD also improve over time as long as reinfection does not occur; however, with death of adult heartworms, mortality is high, and the prognosis is guarded. In asthma, morbidity is relatively high, but mortality is low, with an overall good to excellent prognosis.

DISEASE RECOGNITION

Feline asthma is encountered worldwide. In the authors' impression, feline HWD is often under-recognized.

AIMS

The aim of this review is to assist clinicians in differentiating feline asthma from feline HWD; as such, the emphasis is on distinguishing clinical features, as well as on diagnostics, therapy and prognosis. In differentiating these conditions, clinicians can attempt the goal of properly managing these diseases and can best educate owners on prognosis.

EVIDENCE BASE

For both feline asthma and feline HWD, the authors have drawn on the available peer-reviewed literature studies involving experimental models as well as spontaneous disease.

Efficacy and safety of imidacloprid 10%/moxidectin 1% spot-on formulation in the treatment of feline infection by Capillaria aerophila

The nematode Capillaria aerophila (Trichuroidea, Trichuridae) affects the respiratory system of cats and other animals and occasionally of human beings. Infected cats may show bronchovesicular sounds, inflammation, sneezing, wheezing and, chronic cough and, sometimes, bronchopneumonia and respiratory failure. The present study evaluated the efficacy and safety of the antiparasitic spot-on formulation containing imidacloprid 10 %/moxidectin 1 % (Advocate®, Bayer Animal Health) in the treatment of natural feline infection with the lungworm C. aerophila. The efficacy of Advocate® administered once was tested on days 7 ± 1 and 11 ± 1 following treatment at day 0 and compared to faecal egg counts on days −6 ± 1 and −2 ± 1. Overall, 36 cats treated either with Advocate® (treatment group, n = 17 cats) or left untreated (control group, n = 19 cats) were included in the study. Geometric means of faecal egg counts values in eggs per gram of faeces were 124.03 prior to treatment and 0.26 posttreatment in treatment group, while 107.03 and 123.94 pre- and posttreatment in the untreated cats. Post-baseline egg counts showed a 99.79 % reduction in Advocate®-treated animals in comparison with cats which were left untreated. Also, treated cats showed no adverse events. This trial demonstrated that Advocate® spot-on formulation is safe and effective in the treatment of feline lung capillariosis caused by C. aerophila.

Elimination of Dirofilaria (syn. Nochtiella) repens microfilariae in dogs with monthly treatments of moxidectin 2.5%/imidacloprid 10% (Advocate, Bayer) spot-on

Elimination of microfilaria in dogs infected with zoonotic Dirofilaria repens would be desirable to reduce further spread. Moxidectin has demonstrated efficacy against microfilariae and safety in dogs infected with Dirofilaria immitis and could be an option for controlling D. repens microfilariae. A field study with 64 dogs previously confirmed positive for D. repens microfilaria was conducted in Hungary, in which a spot-on product (Advocate, Bayer) was tested. Treatments were applied to 44 dogs once a month for 3 months (five dogs) or 6 months (22 dogs), alternatively every 2 weeks for 6 months (17 dogs). Twenty dogs remained untreated. Microfilaria counts were performed once a month and for a further 6 months following the last treatment. Two weeks after the first treatment, 38 of 44 dogs were microfilaria negative. Four weeks after the initial treatment, one dog still showed a low microfilaria count. Following the second treatment, all treated dogs were negative. This status was maintained during the 6-month observation period after the last treatment. These data demonstrate the successful long-lasting elimination of microfilariae. Moreover, it may be supposed that adult D. repens were killed based on the observation that no further microfilariae were seen up to 6 months after the end of the treatment period.

Field efficacy and safety of a combination of moxidectin and imidacloprid for the prevention of feline heartworm (Dirofilaria immitis) infection

Throughout the end of March to beginning of May 2006, 212 owned cats and 608 owned dogs from a heavy endemic area for canine heartworm (HW) disease in northern Italy have been examined to assess HW infection prevalence. Both cats and dogs were clinically examined and blood samples were taken from each animal to be examined for HW antibody (Ab). Ab-positive cats were further examined for circulating microfilariae, HW antigens (Ag) and by echocardiography (ECHO) to assess the presence of adult worms. Dogs were clinically examined and blood samples taken from each animal were examined for circulating microfilariae and for HW Ag. Ten cats (4.7%) were found Ab positive. Of these, 6 cats were Ag positive (2.6%) and in 4 (1.8%) the worms were visualized by ECHO. HW prevalence in dogs was 36% (221/608). One hundred and seventy-six (29%) were both microfilaraemic and Ag positive, 40 (7%) had occult infections (no circulating microfilariae) and 7 (1%) were microfilaraemic but Ag negative. Upon owners' consent, 132 cats (including cats Ab and/or Ag and ECHO positive) were prophylactically treated against HW disease with an imidacloprid/moxidectin spot-on combination (10% imidacloprid/1% moxidectin) monthly administered for 6 months. Cats were re-examined for HW infection in November, 1 month after the last drug administration, and in May-June 2007, 7-8 months after the last treatment. All 122 cats found HW negative before treatment, were found negative at the two examinations at the end of study. The 4 cats Ab positive, 2 cats Ab and Ag positive and 1 Ab, Ag and ECHO positive at the beginning of treatment were found negative. Throughout the treatment, transitory hypersalivation and generic signs of annoyance were reported by owners in 6 cats (4.5%). All signs regressed spontaneously.