Evaluation of the therapeutic and preventive efficacy of 2.5 % moxidectin / 10 % imidacloprid (Advocate(®), Bayer animal health) in dogs naturally infected or at risk of natural infection by Dirofilaria repens

Usual or unusual presentations of Dirofilaria repens in two sibling dogs: a case report

This study describes two different manifestations of Dirofilaria repens infection in sibling dogs with microfilaremia. Dog 1, asymptomatic, harbored a gravid female of D. repens on the parietal layer of tunica vaginalis of one testicle and showed a marked circulating eosinophilia (3.3·103/μL). Both testicles were normal in shape and size without any gross lesions. Dog 2 had a pyotraumatic dermatitis. The cases were confirmed by PCR and sequencing. The sequences obtained showed 100% identity with those of D. repens isolated from human scrotum in Croatia. The treatment with moxidectin 2.5% and imidacloprid 10%/kg was effective in eliminating microfilariae after just one application, as demonstrated by negative modified Knott's tests and PCR analyses of blood samples. This status was maintained during the post-treatment observation period. The classical localization of D. repens in dogs is in subcutaneous tissues, within nodules or free; however, it can also occur with some frequency in testicles, as described in humans. The infection can be associated with circulating eosinophilia or pyotraumatic dermatitis, as reported in this study. Thus, in endemic areas, it is advisable to carefully inspect the removed testicles at neutering since parasite localization can take place without any macroscopic changes. Moreover, in the case of circulating eosinophilia or pyotraumatic dermatitis, investigations should include modified Knott's test and PCR to ensure that D. repens is not the cause of these alterations. Rapid and sensitive tests for the early detection of infected animals would help to prevent or limit the spread of this zoonosis.

Recent advances on Dirofilaria repens in dogs and humans in Europe

Dirofilaria repens is a nematode affecting domestic and wild canids, transmitted by several species of mosquitoes. It usually causes a non-pathogenic subcutaneous infection in dogs and is the principal agent of human dirofilariosis in the Old World. In the last decades, D. repens has increased in prevalence in areas where it has already been reported and its distribution range has expanded into new areas of Europe, representing a paradigmatic example of an emergent pathogen. Despite its emergence and zoonotic impact, D. repens has received less attention by scientists compared to Dirofilaria immitis. In this review we report the recent advances of D. repens infection in dogs and humans, and transmission by vectors, and discuss possible factors that influence the spread and increase of this zoonotic parasite in Europe. There is evidence that D. repens has spread faster than D. immitis from the endemic areas of southern Europe to northern Europe. Climate change affecting mosquito vectors and the facilitation of pet travel seem to have contributed to this expansion; however, in the authors' opinion, the major factor is likely the rate of undiagnosed dogs continuing to perpetuate the life-cycle of D. repens. Many infected dogs remain undetected due to the subclinical nature of the disease, the lack of rapid and reliable diagnostic tools and the poor knowledge and still low awareness of D. repens in non-endemic areas. Improved diagnostic tools are warranted to bring D. repens diagnosis to the state of D. immitis diagnosis, as well as improved screening of imported dogs and promotion of preventative measures among veterinarians and dog owners. For vector-borne diseases involving pets, veterinarians play a significant role in prevention and should be more aware of their responsibility in reducing the impact of the zoonotic agents. In addition, they should enhance multisectorial collaboration with medical entomologists and the public health experts, under the concept and the actions of One Health-One Medicine.

Marked subcutaneous mast cell and eosinophilic infiltration associated with the presence of multiple Dirofilaria repens microfilariae in 4 dogs

Dirofilaria repens is a parasitic nematode in the subcutaneous tissue of carnivores, including dogs and cats, transmitted by mosquitoes. Human beings may be accidental hosts. Infection of a dog with D repens was first reported in Palestine in 1934, and 2 additional cases were reported in dogs in Israel to date. This report describes D repens infection in 4 dogs in Israel that presented with subcutaneous masses, which were cytologically characterized by marked mast cell and eosinophil infiltration. In 3 cases, multiple microfilariae were present in the lesions; rare microfilariae were present in the 4^th case. In all 4 dogs, PCR of fine-needle aspirates from the lesions were positive for D repens. The mast cells observed in all lesions were uniform and highly granulated, and with the presence of the microfilariae, a mast cell tumor was considered less likely. This report suggests that D repens infection-associated subcutaneous lesions, characterized cytologically by massive mast cell and eosinophil infiltration, should be considered a differential diagnosis for mast cell tumor, especially in geographic locations endemic for this nematode. Notably, all 4 dogs were infected with D repens despite a routine prophylactic doramectin therapy administered every 3 months, probably due to the relatively long time interval between treatments.

Microfilaricidal efficacy of a single administration of Advocate(®) (Bayer Animal Health) in dogs naturally infected with Dirofilaria immitis or Dirofilaria repens

The present study evaluated the microfilaricidal efficacy of a single application of the spot-on containing imidacloprid 10%/moxidectin 2.5% (Advocate(®), Bayer Animal Health) in dogs naturally infected either by Dirofilaria immitis or Dirofilaria repens. Dogs living in north-eastern and central-southern Italy, endemic for D. immitis and D. repens respectively, were randomly screened. Sixteen animals, eight infected with D. immitis and eight with D. repens, and fulfilling inclusion criteria were enrolled. Dogs infected with D. immitis received an adulticide treatment prior to the study and Advocate(®) 3 weeks after. The animals were divided in blocks of two (1:1, T1:T2) animals each, where Day 0 (D0) had an interval of 15days to compare T2 vs. T1 dogs during the first fortnight of examination (i.e. T2 dogs acted as control animals at each examination). At baseline (Days -15 and 0 for T2 and T1 dogs, respectively) the animals had a range of microfilaraemia of 180-99.700mff/ml (D. immitis) and 60-750 mff/ml (D. repens). All animals received a topical administration of Advocate(®) at D0 and were examined for microfilariae with microscopic and molecular tests at D15, D30, D60 and D90. All animals scored negative for mff at the first control post-treatment and throughout the study, with the exception of two D. immitis- infected animals that had a 2 mff/ml count at D15, and then become negative from Day 30 onwards. No adverse events were observed. The present study demonstrates the safety and the high microfilaricidal efficacy (99.97% and 100% for D. immitis and D. repens, respectively) of a single dose of moxidectin contained in Advocate(®) in naturally infected dogs.

Chemical Compatibility and Safety of Imidacloprid/Flumethrin Collar (Seresto®) Concomitantly Used with Imidacloprid/Moxidectin (Advocate®, Advantage® Multi) and Emodepside/Praziquantel (Profender®) Spot-on Formulations

Safety of concomitant use of veterinary products is of clinical interest. A series of studies was performed to evaluate the chemical compatibility and short term dermal and systemic safety of an imidacloprid/flumethrin collar (Seresto(®)/ Foresto(®), Bayer) used concomitantly with spot-on or tablet formulations.Chemical compatibility was evaluated in-vitro (study reference A) on collar pieces, followed by two small, non-controlled clinical studies (study reference B) in both, cats and dogs. The studies showed, that certain solvents affected the collar in-vitro, but not in their marketed formulations.Dermal and systemic safety of different spot-on or tablet formulations was first evaluated in a small, non-controlled clinical study (study reference C) in cats and dogs, via clinical observations only, followed by controlled clinical safety studies of concomitant use with imidacloprid/ moxidectin (Advocate(®)/ Advantage(®) Multi, Bayer) in dogs and cats (study reference D) and emodepside/ praziquantel (Profender(®), Bayer) in cats (study reference E), assessing safety aspects by clinical observations and statistical analyses of hematology and clinical chemistry parameters compared to baseline values and between treated and control groups.Dermal safety findings over all clinical studies (study references B to E) matched those already described for the respective products and included transient cosmetic changes (oily hair and crystal formation) at the site of spot-on application and broken hair, transient alopecia and skin alterations at the site of collar application. There were no indications of these findings aggravating under the conditions of concurrent use. There were no systemic safety findings of clinical significance in any of the clinical safety studies (study reference C to E). Assessment of blood parameters revealed some deviations from baseline levels and from the reference range in dogs as well as in cats, but no clinical relevance could be deduced. Hematology and clinical chemistry results confirmed the safety of the concomitant treatment. It is concluded that Seresto(®) is chemically compatible with solvents used in major spot-on formulations on the market and is dermally and systemically safe for adult dogs and cats when used concomitantly with Advocate(®) and Profender(®) spot-on formulations.

Laboratory Evaluation of the Efficacy of 10 % Imidacloprid + 2.5 % Moxidectin Topical Solution (Advantage® Multi, Advocate®) for the Treatment of Dirofilaria immitis Circulating Microfilariae in Dogs

This study examined the efficacy of 10 % imidacloprid + 2.5 % moxidectin topical solution (Advantage ® Multi, Advocate®, Bayer) for the treatment of circulating microfilariae from dogs naturally infected with Dirofilaria immitis. The study included two groups of 11 dogs each that consisted of two replicates. Replicate 1 contained 12 dogs (6 treated and 6 controls) and replicate 2 contained 10 dogs (5 treated and 5 controls). Six of the 10 dogs in replicate 2 were the controls from replicate 1. All dogs entering the study completed a physical examination including chest radiographs, blood collections for examination of Dirofilaria immitis circulating microfilariae, serum chemistry, complete blood counts and urinalysis. To qualify for the study each dog was required to have a geometric mean ≥ 300 microfilariae per ml of blood from 3 consecutive samples collected during the 8 day acclimation period and a heartworm disease classification of 1 or 2. Dogs were treated on study days 0 and 28. Post-treatment microfilarial counts were performed on study days 1, 2, 3, 7, 14, 21, 28, 29, 35, and 42. Percent microfilarial reduction was determined by comparing the geometric mean number of circulating microfilaria remaining in treated dogs with those remaining in the control dogs post-treatment. Seven days after the first treatment, the geometric mean microfilarial counts in treated dogs were reduced by > 99 % compared to the control dogs. Reduction remained at > 99 % through the end of the study at 42 days after the first treatment (14 days after the second treatment). The results of this study demonstrated that Advantage® Multi for dogs is efficacious for treatment of circulating D. immitis microfilariae in naturally infected heartworm-positive dogs with no treatment-related adverse events observed.

The main factors influencing canine demodicosis treatment outcome and determination of optimal therapy

The main idea of this research was to evaluate the efficacy of canine demodicosis conventional treatments using mathematical analyses. All available papers published between 1980 and 2014 were used in this study. One hundred six clinical trials enrolling 3414 cases of generalized demodicosis in dogs are studied. Dogs entered in the analysis were only the ones in which the disease occurred naturally, excluding the studies in which transplantation of Demodex canis mites was done from other animals. In conventional acaricide treatments, sorted according to active substances (moxidectin, amitraz, doramectin, ivermectin, and milbemycin oxime), the way of application (spot-on, dips, orally, or subcutaneous), concentration, and interval of application were used as input parameters in mathematical modeling. Data of interest were the treatment outcome, the number of dogs that went into remission, the number of animals not responding to treatment microscopically, the average duration of therapy, the follow-up period, the number of patients with disease recurrence, the number of adverse effects, and the number of animals with side effects. Dogs lost to follow-up or when the treatment was discontinued, due to various reasons not in connection with the therapy protocol, were not considered. Statistical and mathematical analyses were applied for prediction of the drugs' effectiveness. Developed mathematical models showed satisfactorily r (2), higher than 0.87. Good evidence for recommending the use of milbemycin oxime PO (0.5 mg/kg, daily) and moxidectin spot-on (Advocate®, Bayer) weekly is found. A bit less effective therapies were based on ivermectin PO (0.5 mg/kg, daily), moxidectin PO (0.35 mg/kg, daily), and amitraz dips (0.05 % solution, weekly), respectively. It is important to keep in mind that Advocate® is recommended by the manufacturer for use in milder cases.

Efficacy of fipronil combined with permethrin commercial spot on (Effitix) preventing Culex pipiens from feeding on dogs

A controlled clinical trial was carried out to assess the adulticidal and anti-feeding effectiveness of a spot-on combining fipronil and permethrin (Effitix, Virbac, Carros, France) in preventing Culex pipiens from feeding on dogs. Twelve dogs with equal sensitivity to mosquitoes were included in the study and divided into two groups of six dogs: an untreated control group and a group treated with Effitix. All dogs were challenged with 80 females C. pipiens for 90 ± 5 min on days -7, 1, 7, 14, 21, and 28 (day 0 being treatment day). The number of engorged, dead, and live mosquitoes was determined after each exposure to treated and untreated dogs. Dead mosquitoes were also counted 24 h after exposure. The anti-feeding effect of the spot-on formulation was 100, 99.5, 97.7, 98.3, and 96.7% on days 1, 7, 14, 21, and 28, respectively. The mortality effect was 66.6, 55.9, 38, 17.2, and 12.3% on days 1, 7, 14, 21, and 28, respectively. At each challenge point, the mortality and anti-feeding effects on mosquitoes were significantly different between the control and treated group (p < 0.05). The results indicate that a combination of permethrin and fipronil could be used as an effective mosquito control strategy in dogs and is therefore recommended for use in a dirofilariasis prevention program.

Dirofilaria repens infection in a dog imported to Norway

Dirofilaria repens infection was diagnosed in a dog that had been imported to Norway from Hungary three years previously. The dog was a four-year-old castrated male mixed-breed dog and presented for examination of two masses on the right thoracic wall. Fine needle sampling from the subcutaneous nodules and subsequent cytological examination revealed a high number of microfilariae and a pyogranulomatous inflammation. At re-examination approximately 3 weeks later, both masses had apparently disappeared spontaneously, based on both inspection and palpation. However, examination of peripheral blood by a modified Knott's test revealed a high number of unsheathed microfilariae with mean length of 360 μm and mean width of 6-7 μm, often with the classic umbrella handle appearance of D. repens. Polymerase chain reaction and sequencing confirmed the D. repens diagnosis. Subcutaneous dirofilariosis caused by D. repens is probably the most common cause of human zoonotic dirofilariosis in Europe, but currently is rarely encountered in northern countries such as Norway. However, travelling, import and relocation of dogs have increased, and thus the geographical range of these parasites is likely to increase from traditionally endemic southern regions. Increasing numbers of autochthonous cases of D. repens infections in dogs have been reported in eastern and central Europe. Although infection with D. repens often induces only mild signs or subclinical infections in dogs, they nevertheless represent a reservoir for zoonotic transmission and thus a public health concern, and, in addition, due to the long prepatent period and the high frequency of subclinical infections or infections with unspecific clinical signs, could easily be missed. Lack of experience and expectation of these parasites may mean that infection is underdiagnosed in veterinary clinics in northern countries. Also, predicted climate changes suggest that conditions in some countries where this infection is currently not endemic are likely to become more suitable for development in the intermediate host, and thus the establishment of the infection in new areas.

Potential efficacy of monthly administrations of spot-on moxidectin 2.5%/imidacloprid 10% in the simultaneous prevention of major canine filarioses

Dirofilaria immitis, Dirofilaria repens, and Acanthocheilonema reconditum are the most important canine filariae. These species are expanding their distribution in both endemic regions and in previously free areas, thus enhancing the risk for single and mixed infestations in both dogs and humans. The present study evaluated the potential use of moxidectin in a spot-on formulation in preventing these dog filarioses in a confined area where the three major canine filariae live in sympatry. The trial was performed in a private shelter with a history of mixed infestations. Twenty-nine negative dogs were monthly treated with a spot-on formulation containing moxidectin 2.5%/imidacloprid 10% in spring and summer of 2010. The blood of the dogs was examined monthly with classical and molecular assays until December 2011. Twenty-six dogs completed the study, and they scored constantly negative to all diagnostic assays. Three further dogs completed the study in February 2011 until when they were filariae-negative. These results show that monthly treatment with moxidectin may potentially contribute in reducing the spreading of canine filarial diseases. The permanent negativity of treated dogs for the study period is discussed in relation to the potential use of this spot-on formulation in the prevention of single and mixed infestations of major vector-borne canine filariae.

Treatment of Dirofilaria repens microfilariaemia with a combination of doxycycline hyclate and ivermectin

Dirofilaria repens is one of the most widespread mosquito-borne filarioid responsible for infestations in dogs, usually characterized by nodules and other skin lesions. Additionally, the zoonotic potential of this nematode is of public health concern, given that D. repens has been often associated to human dirofilariosis in the Old World. In the present study, the therapeutic efficacy against D. repens microfilariae of a protocol based on doxycycline hyclate (Ronaxan(®), Merial), 10mg/kg every day for 30 days, and ivermectin (Cardotek 30(®), Merial), 6 μg/kg every 15 days for 6 months, was preliminarily investigated in two naturally infested dogs. Blood samples were collected every 30 days during 6 months of treatment and examined by a Knott's modified test and a duplex real-time PCR. The results here presented indicate that this therapeutic protocol, applied monthly, could be effective for treating microfilariaemia in dogs affected by subcutaneous dirofilariosis.

Vector-borne helminths of dogs and humans in Europe

Presently, 45% of the total human population of Europe, as well as their domestic and companion animals, are exposed to the risk of vector-borne helminths (VBH) causing diseases. A plethora of intrinsic biological and extrinsic factors affect the relationship among helminths, vectors and animal hosts, in a constantly changing environment. Although canine dirofilarioses by Dirofilaria immitis and Dirofilaria repens are key examples of the success of VBH spreading into non-endemic areas, another example is represented by Thelazia callipaeda eyeworm, an emergent pathogen of dogs, cats and humans in several regions of Europe. The recent finding of Onchocerca lupi causing canine and human infestation in Europe and overseas renders the picture of VBH even more complicated. Similarly, tick-transmitted filarioids of the genus Cercopithifilaria infesting the skin of dogs were recently shown to be widespread in Europe. Although for most of the VBH above there is an increasing accumulation of research data on their distribution at national level, the overall impact of the diseases they cause in dogs and humans is not fully recognised in many aspects. This review investigates the reasons underlying the increasing trend in distribution of VBH in Europe and discusses the diagnostic and control strategies currently available. In addition, this article provides the authors' opinion on some topics related to VBH that would deserve further scientific investigation.

Allergic dermatitis by Dirofilaria repens in a dog: clinical picture and treatment

Adult stages of Dirofilaria repens (Nematoda, Filarioidea) reside in the subcutaneous tissues of the definitive or occasional host as dogs, other animals, and humans, and it is transmitted by mosquitoes. Canine infections with adults and circulating larvae of D. repens are often considered asymptomatic, although in some cases, the parasite causes subcutaneous nodules, diffused dermatitis, skin lesions, and itching. This report provides a complete clinical description of an unusual case of allergic diffused dermatitis caused by D. repens in a naturally infected dog and its successful treatment with the use of a spot-on solution containing imidacloprid 10%/moxidectin 2.5%. The dog presented multiple pustules and alopecic areas with lichenification, hyperpigmentation, and erythematous scaling margins without pruritus. Histological examination was compatible with allergic dermatitis. After being unsuccessfully managed for suspected food hypersensitivity, with a significantly worsening of the lesions, a Knott’s analysis detected nematode larvae in the blood. Morphological and molecular identification showed them to be D. repens. The dog was then treated with a single administration of a spot-on formulation containing imidacloprid 10%/moxidectin 2.5%, and the dermatological signs completely resolved within 2 months after treatment. The dog showed no recurrence of the lesions, and no circulating microfilariae were found upon microscopic and molecular examination for six consecutive months after treatment. This report indicates the apparent primary role of D. repens in causing hypersensitivity-like skin disease without pruritus in a dog. It also confirms, as recently shown elsewhere, the efficacy of imidacloprid 10%/moxidectin 2.5% in the treatment of dermatitis caused by D. repens.