Dirofilaria immitis in cats from inner Sydney

Two hundred feral cats from the inner suburbs of Sydney were examined post mortem for adult Dirofilaria immitis and circulating microfilariae, and 101 of these cats were tested for heartworm antigens by an ELISA. Only 2 cats (1%) had adult heartworms, the blood sample from another cat contained a single microfilaria. The blood of a further three cats contained small amounts of D immitis antigen. Although D immitis occurs in cats in Sydney, the prevalence is not high enough to warrant prophylactic treatment.     

Intraarticular Dirofilaria immitis microfilariae in two dogs

Medicinal plants have been investigated for their anthelmintic properties and shown to be effective against eggs and larvae of gastrointestinal nematodes. The aim of this study was to evaluate the efficacy of the Lippia sidoides essential oil (LsEO) on sheep gastrointestinal nematodes. Initially, 44 naturally infected sheep were divided and treated with 200 μg kg⁻¹ ivermectin and 230 and 283 mg kg⁻¹ LsEO, respectively, plus the control. Fecal samples were collected from each animal to determine epg at 7, 14 and 21 days after treatment. In another test, 21 sheep were distributed and treated with 200 μg kg⁻¹ ivermectin, 283 mg kg⁻¹ LsEO and the control, respectively. Seven days after treatment, they were euthanized and necropsied to count and identify the nematodes from the abomasum, small and large intestines. In the first test, the efficacy of 230 and 283 mg kg⁻¹ LsEO and ivermectin was 38%, 45.9% and 40.2%, respectively, 7 days after treatment, and 30%, 54% and 39.6%, respectively, 14 days after treatment. In the second experiment, the respective efficacy of 283 mg kg⁻¹ LsEO and ivermectin was 56.9% and 34.4% against Haemonchus spp., and 39.3% and 63.6% against Trichostrongylus spp.     

The occurrence of Dirofilaria immitis in dogs in South Australia

Heart, lung and samples of blood from 230 dogs were examined for infections of filarial parasites. Dirofilaria immitis worms and microfilariae were detected in one dog. Blood samples from a further 1428 dogs were examined for microfilariae and 22 were found to be infected. Eighteen dogs were infected with D immitis microfilariae and four with Dipetolonema reconditum microfilariae. The histories were available for 18 of the dogs infected with heartworm and only seven dogs had not travelled outside South Australia. It was concluded that heartworm infection was endemic in South Australia but the apparent prevalence was only about 1%.     

The humoral response in natural Dirofilaria immitis infections in dogs

Plasma samples from dogs with infections of Dirofilaria immitis were assessed using ELISA and Western blotting techniques. These results were then assessed in relation to age and sex of the host, and to the numbers of microfilariae and adult filariae. Dogs with microfilariae tended to have lower levels of infection. In infected dogs, mean ELISA titres increased directly with the degree of infection. Dogs that were either young or mildly infected, showed a preferential antibody reactivity to antigens in the high molecular weight regions of the immunoblots. With increasing age and/or the extent of infection, an antibody response to antigens in the low molecular weight regions was apparent.     

Influence of immunosuppressants against Dirofilaria immitis infection in dogs

Two immunosuppressive drugs, azathiopurine (AZP) and prednisolone (PDS), were examined on dogs experimentally infected with Dirofilaria immitis in order to estimate the involvement of immunological assail in rejecting the parasite by the host. AZP was orally administered to 3 dogs daily at a dosage of 1-10 mg/kg for a period from 3 days before infection until the end of the experiment. The dose was then varied and transiently ceased according to the severity of the side effects. PDS was subcutaneously administered daily to 2 dogs. They were administered 10 mg/kg of PDS from 3 days before infection to day 15 and 5.0-8.5 mg/kg from day 60 after infection to day 70. The serum D. immitis-specific antibody level assessed by an indirect hemagglutination test was steadily decreased in the AZP-medicated dogs. However, in the PDS-medicated dogs, the antibody titer was decreased until day 32 and, thereafter, was recovered. When all dogs were sacrificed between days 145-148, an average recovery rate of worms in both the AZP- and PDS-medicated dogs was 52.5% and 49.6%, respectively, while the controls showed 42.5%. The statistical analysis revealed no significant difference among the groups, indicating that the administration of AZP and PDS was not effective in protecting the larvae from the host's immune attack.     

Dirofilaria immitis infection in dogs: cardiopulmonary biomarker levels

Cardiopulmonary biomarkers are biological parameters that can be objectively measured and quantified as indicators of pathogenic processes (heartworm disease) or as indicators of response to therapeutic intervention. To determine levels of cardiopulmonary biomarkers in canine dirofilariasis, measurements of cardiac troponin T, cardiac troponin I, myoglobin, and D-dimer concentrations were performed for dogs with and without evidence of adult heartworm infection. The results showed that levels of cardiac troponin T were undetectable in all dogs studied while levels of cardiac troponin I were higher in dogs infected with Dirofilaria immitis. In healthy dogs, levels of myoglobin and D-dimer were below detection limits of the instrument and were significantly higher in heartworm-infected dogs, notably in microfilaremic dogs. The results suggest the possibility of using troponin I and myoglobin as markers for cardiac damage and the D-dimer as a supportive tool for a diagnosis of pulmonary thromboembolism in dogs with cardiopulmonary dirofilariasis.     

The incidence and pathology of Dirofilaria immitis infection in dogs in Nairobi

Six cases of canine dirofilariasis in Nairobi are reported. Adult parasites inhabited mainly the right ventricle and pulmonary arteries, but in one case they were also in the right atrium, the anterior and posterior vena cavae. In one dog there occurred typical pulmonary lesions. The lungs were oedematous, congested, slightly consolidated and had chronic interstitial pneumonia. Pulmonary arteries exhibited endarteritis, occasional thrombosis, thickened vessel wall due to medial fibrosis and perivascular granulo-matous reaction. There was endocarditis, dilatation and hypertrophy of the right heart. Résumé. On rapporte 6 cas de dirofilariase observés à Nairobi. Les parasites adultes habitent surtout le ventricule droit et l'appareil pulmonaire, mais dam un cas, on en a également trouvé dans I'oreillette droite, et les veines caves antérieure et postérieure. Un des chiens a présenté des lesions pulmonaires typiques: les poumons étaient oedématiés, congestionnés, Iégèrement compacts et montraient des lésions de pneumonie interstitielle. Les artères pulmonaires étaient atteintes d'endoartérite, présentaient parfois des thromboses, et un épaississement de la paroi par fibrose de la tunique médiane et granulomatose périvasculaire. On a également noté une en-docardite et une dilatation et une hypertrophie du coeul droit. Zusammenfassung. Es wird über sechs Fälle von Dirofilariasis bei Hunden in Nairobi berichtet. Erwachsene Parasiten waren vor allem im rechten Ventrikel und in Pulmonalgefässen, aber in einem Fall auch im rechten Vorhof und in der vorderen und hinteren Vena cava angesiedelt. Bei einem Hund traten typische Pulmonalläsionen auf. Die Lungen waren ödematös, gestaut, leicht verfestigt und wiesen chronische interstitielle Pneumonie auf. Die Pulmonalarterien zeigten Endarteriitis, gelegentlich Thrombose, verdickte Gefässwand infolge medialer Fibrosis und peiivasculäre Granulomatose. Es bestand Endocarditis, Dilation und Hypertrophie des rechten Herzens.     

Membranous glomerulonephritis in dogs infected with Dirofilaria immitis.

Membranous glomerulonephritis was diagnosed in five dogs with patent Dirofilaria immitis infections. Electron-dense deposits were present on the epithelial side of the glomerular basement membrane. An immunofluorescent study demonstrated immunoglobulins in the capillary wall and mesangium of the glomeruli. The glomerular lesions were considered to represent an immune complex form of glomerulonephritis induced by the D. immitis infection.     

No evidence of endemic infection with Dirofilaria immitis in dogs

Extract

Dirofilaria immitis is periodically recorded in dogs imported from Australia into New Zealand. In this country, environmental conditions are marginal for the transmission of this species, but potential mosquito intermediate hosts are known to be present⁽¹⁾. Development in the intermediate host is temperature dependent, with most reports indicating that a mean temperature of at least 18 °C is required^(2)(3)(4). Therefore, the most likely locations in New Zealand for D. immitis to establish are the Auckland region and areas north of this.     

The enzyme-linked immunosorbent assay for detecting antibodies against Dirofilaria immitis in dogs

Antisera prepared in mice by injection of antigens from Dirofilaria immitis, Toxocara canis, Dipylidium canium and Fasciola hepatica and sera from Dirofilaria-infected and non-infected dogs were tested at different dilutions using an enzyme-linked immunosorbent assay (ELISA). For this ELISA, adult D. immitis antigen was fractionated by gel filtration methods and then absorbed with immunoadsorbent-fixed IgG fractions from mouse sera immunized with various parasites. The results indicated satisfactory discrimination between antisera to D. immitis and those to other parasites. A significant ELISA O.D. value was considered to be greater than or equal to 0.30 with a 1 : 250 dilution of the dog sera. However, the lack of significant differences between the O.D. value of microfilaraemic and amicrofilaraemic infections was observed. These facts suggest that the use of immunoadsorbent chromatography for canine dirofilariasis is especially useful for purifying antigens and eliminating cross-reactions against other parasitic infections, when immunological methods are used for serodiagnosis.     

Influence of immune treatments against Dirofilaria immitis infection in dogs

Mongrel dogs were inoculated with two kinds of antigenic substances. The first was a phosphate buffered saline extract of whole Dirofilaria immitis mixed with aluminum hydroxide gel (group 1), and the second was an orally administered live Metastrongylus apri infective larvae (L3) (group 2). Both groups were then infected with D. immitis L3. Indirect hemagglutination (IHA) tests showed that the antibody was produced by these inoculations before the infection was introduced, even in dogs inoculated with M. apri. This suggests a cross-reactivity between D. immitis and M. apri. The initial passive cutaneous anaphylaxis (PCA) antibody production was markedly delayed by about 70 days in group 2 compared with the production in the infected control dogs (group 3). The appearance of microfilaremia was also delayed by about one month in group 2 compared with that in the above control group. All dogs were sacrificed after the termination of the observation and worms recovered from the right ventricle and pulmonary arteries were counted and measured. The results indicated that immunization resulting from the homologous worm-somatic antigen might accelerate the growth of the infected larvae, whereas immunization resulting from the heterologous worm antigen, but cross-reactive to D. immitis, might disadvantageously affect the growth.     

Effects of doxycycline on early infections of Dirofilaria immitis in dogs

The antifilarial effects of tetracycline drugs were first demonstrated when they were found to be highly effective against L(3) and L(4) of Brugia pahangi and Litomosoides sigmodontis in rodent models. Tetracyclines are also now known to have activity against microfilariae and adult Dirofilaria immitis, but assessment of their activity against larval and juvenile heartworms has not been reported previously. This study assessed the effects of doxycycline administered orally at 10mg/kg twice daily for 30-day periods at selected times during the early part of the life cycle of D. immitis in dogs with dual infections of D. immitis and B. pahangi. Twenty beagles were randomly allocated by weight to four groups of five dogs each. On Day 0, each dog was given 50 D. immitis L(3) and 200 B. pahangi L(3) by SC injection. Dogs received doxycycline on Days 0-29 (Group 1); Days 40-69 (Group 2); or Days 65-94 (Group 3). Group 4 served as untreated controls. Blood samples were collected for microfilariae counting and antigen testing. Necropsy for collection of adult heartworms and selected tissues were performed Days 218-222. Heartworms recovered were examined by immunohistology, conventional microscopy/transmission electron microscopy, and molecular biology techniques. No live heartworms were recovered from dogs in Group 1; dogs in Group 2 had 0 to 2 live worms (98.4% efficacy), and dogs in Group 3 had 0-36 live worms (69.6% efficacy). All control dogs had live adult heartworms (25-41). The live worms recovered from dogs in Groups 2 and 3 were less developed and smaller that worms from control dogs. Microfilariae were not detected in any dogs in Groups 1 and 2; one dog in Group 3 had 1 microfilariae/ml at necropsy. All control dogs had microfilariae at necropsy. One dog in Group 1 was antigen positive at one sampling (Day 166). One dog in Group 2 was antigen positive Days 196 and 218-222 and three dogs in Group 3 were antigen positive at one or more samplings All five control dogs were antigen positive at all three sampling times. These findings suggest that doxycycline at 10mg/kg orally twice daily for 30 days has efficacy against migrating tissue-phase larvae and juvenile worms and will delay or restrict microfilarial production.     

Activity of flubendazole against developing stages of Dirofilaria immitis in dogs

A formulation of flubendazole was studied to determine the activity against developing stages of Dirofilaria immitis in artificially infected pups. Flubendazole suspension was administered subcutaneously at a dose rate of 50 mg/kg of body weight once a day for 1, 3, or 5 consecutive days at various times during the experimental period. The pups were necropsied 6 months after the experimental infection, and the heart and pulmonary arteries were examined for adult worms. Optimal activity was obtained when flubendazole suspension was administered subcutaneously for 5 consecutive days, either 1 or 2 months after infection. The formation of encapsulated deposits, containing white viscous fluid, was observed at the injection sites of all treated pups.     

Prevalence of Dirofilaria immitis infection in dogs from Dandong, China

The aim of the present study was to estimate the prevalence and risk factors of Dirofilaria immitis infection in dogs from Dandong, China. A total of 886 dogs were examined for D. immitis infection by microscopic examination and PCR, indicating that the prevalence was 16.6% (213/886) and 24.0% (147/886), respectively. The odds of infection were significantly higher in older dogs and dogs sheltered in outdoor, compared to the younger ones and ones sheltered in indoor. No significant difference of infection was observed in different genders, and between pure breed and cross-breed dogs in the same rearing conditions. These results indicated that the risk of exposure to D. immitis in dogs is high in Dandong, China, and prophylaxis against the parasite is advisable to decrease the incidence of canine dirofilariosis.     

Current prevalence of Dirofilaria immitis in dogs, cats and humans from the island of Gran Canaria, Spain

The island of Gran Canaria is a hyperendemic area for canine dirofilariasis. The aim of the present study was to provide data on Dirofilaria immitis in dogs, cats, and humans on this island in 2010. The data confirms the prevalence in the overall canine population (19%), with a considerably higher prevalence (43%) in the autochthonous breed of Canarian Warren hound. The prevalence in the feline population (33%) is higher than that of the canine population, and the existence of specific D. immitis antibodies in the inhabitants of the island of Gran Canaria (12%) is confirmed. In both cats and humans, the prevalence, according to the different climate areas on the island, is related to the prevalence of D. immitis in dogs in the same area, which shows the key epidemiological role played by the canine host with regard to the transmission to other hosts of D. immitis.