Nodular presentation of Dirofilaria repens infection in a cat mimicking a fibrosarcoma

A cat with multiple subcutaneous nodules suggesting a soft tissue sarcoma by physical and computed tomographic examination was diagnosed as being affected by subcutaneous filariosis based on cytologic and ultrasonographic assessments. Nodules were surgically removed and extracted nematodes were identified by PCR as Dirofilaria repens. Furthermore, DNA of Dipetalonema dracunculoides (syn. Acantocheilonema dracunculoides) was detected by PCR, with no evidence of circulating microfilariae. To the best of the authors' knowledge, this represents the first report describing adults of D repens in multiple subcutaneous nodules in a cat. Cytopathologic examination allowed characterization of the parasitic nature of the nodules. Veterinary practitioners should be aware of the possible nodular presentation of D repens in cats and should include D repens in the differential diagnosis of subcutaneous neoformations in the cat.     

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.     

Subconjunctival Dirofilaria repens infection in a dog resident in the UK

Dirofilaria repens infection was diagnosed in a 5‐year‐old female German shepherd crossbreed, originally from Romania but brought into the UK in February 2014. The dog presented with conjunctivitis in March 2014 and then again 2 months later with additional ocular and nasal mucopurulent discharge. Bacterial cultures from the nasolacrimal duct were negative for bacterial growth. The case was referred in August 2014 for ophthalmic examination, which revealed abnormalities in both eyes, especially the left. They included mild palpebral conjunctival hyperaemia and marked follicular conjunctivitis, as well as a dorsonasal bulbar conjunctival mass. Serum biochemistry was unremarkable and a conjunctival biopsy taken from the dorsonasal bulbar conjunctival mass revealed eosinophilic/lymphoplasmacytic conjunctivitis. At re‐examination, nematodes were found in the area of the previous biopsy site and in the ventral palpebral conjunctival fornix. Polymerase chain reaction and sequencing confirmed these to be D. repens. Treatment with 10% imidacloprid and 2·5% moxidectin (Advocate Spot‐On) was successful, and clinical signs resolved over a 6‐week period. This case report indicates that D. repens infection should be considered as a possible aetiological cause of ocular lesions in dogs in the UK, especially those with a history of foreign travel. Implications for establishment and spread of D. repens in the UK are discussed.     

Dirofilaria repens infection in a dog: diagnosis and treatment with melarsomine and doramectin

Therapy of canine dirofilariois due to Dirofilaria repens is indicated for dogs suffering from clinical signs of this disease, such as dermal swelling, sub-cutaneous nodules and pruritus. It is also important in order to decrease the risk of infection to other dogs and humans in the vicinity of the infected animal when suitable mosquito vectors are present. Combined therapy with the arsenic adulticide melarsomine and the avermectin microfilaricidal doramectin was effective in clearing infection with D. repens in a dog. The number of microfilariae dropped from 17 microl(-1) blood pre-treatment to 7 microl(-1) following the first adulticide injection and reached 0 a day after the microfilaricidal administration. The dog remained negative for D. repens microfilaremia during a follow-up period of 90 days. Euthanasia and necropsy performed 3 months after the initiation of therapy due to a progressive neoplastic disease revealed no evidence of filariae.     

Dermatitis associated with Dirofilaria repens microfilariae in three dogs in Saudi Arabia

The presence of microfilariae of the zoonotic nematode Dirofilaria repens is reported in three dogs from Saudi Arabia, manifesting as pruritic dermatitis with signs including erythema, alopecia, papules, crusting and hyperkeratosis. All dogs were found to have concurrent babesiosis. Specific treatments against the two conditions led to complete clinical recovery and disappearance of microfilariae from the blood one month later.     

Autochthonous canine Dirofilaria repens in the vicinity of Warsaw

In 2009 microfilaremia was recognized in ten dogs living in five distinct districts located near Warsaw, the capital of Poland. Based on PCR results, all the animals were found to be infected with Dirofilaria repens. Nine of the infected dogs have never travelled outside the country and it was assumed that the cases were native. Monitoring the infection in the European countries should be introduced to establish the actual geographic range of dirofilariosis.     

Adult Dirofilaria repens in a subcutaneous granuloma on the chest of a dog

A 10-year-old, 9 kg, intact male crossbred dog was treated for nasal mites with milbemycin oxime using a dose of 1 mg/kg bodyweight orally, three times at 10-day intervals. One month after the initiation of this treatment a subcutaneous nodule developed on the sternum of the dog. The nodule was removed and found to contain a single, 82 mm long, thread-like nematode. Several exotic parasites were suspected as possibilities because the dog had been imported to Norway from South Africa. Microfilariae were not detected in the blood and heartworm antigen tests were negative. The worm was identified morphologically as an adult, female Dirofilaria repens. This is the first report of D repens from Norway. The case is of interest because of the differential diagnostic problem it posed and because infestation was recognised following treatment of another parasitic condition with a broad-spectrum, antiparasitic drug. In addition, the case provides a reminder of the necessity to be aware of geographical differences in disease occurrence which can produce unexpected disease in non-endemic areas as a consequence of increased international travel with pets.     

Retrospective study on the presence and pathogenicity of Dirofilaria repens in 5 dogs and 1 cat from Aosta Vally

Aosta Valley is the only region of Italy free of reported human cases of dirofilariosis due to Dirofilaria repens. Nonetheless, the retrospective analysis of five locally acquired D. repens infections in dogs, seems to indicate that an animal reservoir exist in the area. A feline case imported from Camargue, France, is also described. The most common dermatological signs were erythema, alopecia, crusting, papulae and nodules. All patients had lesional pruritus and dogs were affected by concurrent babesiosis. Eradication of the underlying condition, followed by a therapy with the specific adulticide and microfilaricide drugs led to a complete recovery of microfilaraemia. Increased pet travel and ecological changes are extending the ranges of vector borne, parasitic and zoonotic diseases. This fact pose a unique diagnostic challenge for the veterinarian, since the index of suspicion may be absent outside endemic areas.     

Histochemical differentiation of Dirofilaria immitis, Dirofilaria repens and Acanthocheilonema dracunculoides microfilariae by staining with a commercial kit, Leucognost-SP.

The diagnosis of canine heartworm infection is based upon the presence of circulating Dirofilaria immitis microfilariae or on techniques for the detection of serum antibodies or antigens. In the first of these, discrimination between D. immitis, D. repens and Acanthocheilonema dracunculoides microfilariae is based upon the acid phosphatase histochemical stain. In this paper, we propose an alternative technique for histochemical staining using a commercial kit test of naphthol-AS-OL (Leucognost-SP). This offers the advantages of speed and simplicity as compared to the standard Barka procedure.     

Autochthonous Dirofilaria (Nochtiella) repens infection in dogs in Kuwait

Human dirofilariasis caused by Dirofilaria repens is a rare but increasingly reported zoonosis in the Middle East. However, eligible animal reservoirs seldom have been investigated in the area until now. Seven (1.8 percent) out of 381 dogs examined in Kuwait carried D. repens microfilariae showing compatible cutaneous clinical signs and positive response to the adulticide and microfilaricide therapies. This study indicates that dogs from Kuwait are natural hosts of D. repens and therefore act as an animal reservoir for the zoonotic condition.     

Diurnal variation in microfilaremia in a cat experimentally infected with larvae of Dirofilaria immitis

In five healthy mongrel female cats used, four cats (Cats 1-4) were experimentally inoculated with 100-123 larvae (L(3)) of Dirofilaria immitis. Cat 5 was an uninfected control. Only Cat 1 became microfilaremic on Day 201 after inoculation and the diurnal changes in the microfilaria population were monitored every 2 h for 24 h on Day 237 when a sufficient number of microfilaria were detected in the circulation. The maximum number of microfilaria in the blood (1,350/ml) occurred at 9:00 p.m. and then gradually decreased to the minimum of 300/ml at 7:00 a.m., indicating that the number of microfilaria shows a nocturnal sub-periodic pattern of diurnal rhythm even in peripheral blood of cats as an abnormal host. On postmortem examination, 10 live adult worms (three males and seven females) in Cat 1 and one live adult worm (one male) in Cat 2 were detected.     

Dermatitis associated with Dirofilaria (Nochtiella) repens microfilariae in dogs from central Italy

Pruritic dermatitis associated with Dirofilaria (Nochtiella) repens microfilariae in the blood was diagnosed in 22 dogs from Fermo (Central Italy). According to the history, previous unsuccessful treatments with corticosteroids, antibiotics, restricted diet, flea control, levamisole and ivermectin were recorded in 17 dogs (77.3%). The combined filtration tests and antigen tests, performed during the study, were negative for Dirofilaria immitis and Acanthocheilonema reconditum in each case. Dermatological lesions included erythema, papules, single or multifocal alopecia, eczema, lichenification, crusting and nodules. All dogs had pruritus. Concurrent babesiosis was diagnosed in the blood smears of each case (100%), and 60% of the dogs were found to be carriers of canine granulocytic ehrlichiosis (CGE). Three dogs (13.6%) were positive for leishmaniosis. Eradication of the concurrent infections followed by specific macro- and microfilaricide treatment led to complete recovery from the dermatological syndrome. The main conclusion of the study is that D. repens infection can be more pathogenic than is currently considered, and it is apparently an opportunistic disease with serious dermatological consequences.     

Eosinophilia in a cat with acute leukemia

A 4-year-old castrated male domestic shorthaired cat with a history of vomiting and anorexia was diagnosed with leukemia with marked hepatic and splenic infiltration and concurrent eosinophilia with marked tissue infiltration. Despite thorough immunocytochemical and immunohistochemical immunophenotyping, the cell lineage of the leukemia was not identified.     

Cutaneous lesions in dogs with Dirofilaria (Nochtiella) repens infestation and concurrent tick-borne transmitted diseases

A pruritic dermatitis characterized by the presence of erythema, papules, focal or multifocal alopecia, crusting and nodules was seen in 28 dogs with Dirofilaria repens microfilariae infestation in an endemic area in north-west Italy. Previous unsuccessful nonspecific antipruritic treatments, flea control and restricted diet were recorded in 53.6% of the patients. Both the Knott and the antigen tests were negative for Dirofilaria immitis and Acanthocheilonema reconditum. Concurrent babesiosis and/or canine granulocytic ehrlichiosis was also diagnosed in many affected dogs. Preliminary treatment of the concurrent diseases was followed by specific filaricide treatment. The cutaneous lesions, although slightly improved with the initial treatment, resolved completely with macro- and microfilaricide treatment. Although D. repens may be an opportunistic pathogen, this parasite should not be considered as harmless as previously thought and its potential pathogenic role in causing cutaneous lesions in dogs should be considered. Furthermore, it has a zoonotic importance as human cases have been reported worldwide.