Dirofilaria Immitis Infection In Dogs Research Articles

Clinical application of milbemycin D as a prophylactic agent against Dirofilaria immitis infection in dogs: pathological findings following administration.

Pathological findings following milbemycin D (Milbe) administration were examined in 54 dogs. No significant changes were seen in the uninfected group (9 dogs). In microfilaria (mf)-positive group (22 dogs), yellowish-brown spots in the liver, splenomegaly, and reddish-brown spots in the lungs were seen on macroscopic examination, and inflammatory reactions phagocytizing the microfilariae by macrophage were noted in the liver, lungs, spleen and heart on the microscopie examination. These lesions were observed with almost the same frequcncy and severity in the shock-like (7 dogs) and caval syndrome (22 dogs) groups. Howcver, they showed a lower rate and slighter degree in the mf-negative group (11 dogs). To examine the correlation of hepatic lesions and microfilariae, hepatic biopsics and calculations of circulating microfilariae were performed with time in 3 dogs. The number of circulating microfilariae was markedly reduced by 6 hr after administration. Microfilariae in the sinusoid increased in number at 3 hr after administration, neutrophils adhered to microfilariae at 6 hr, macrophages infiltrated around microfilariae and focal necroses containing microfilariae were observed in parenchyma at 9 hr, and macrophage masses were formed at 12 hr.

Prophylactic activity of ivermectin against Dirofilaria immitis infection in dogs: larvicidal activity of ivermectin against D. immitis larvae 30 days after infection.

Larvicidal activity of ivermectin against Dirofilaria immitis larvae of 30 days old was evaluated. A single oral dose of ivermectin to demonstrate complete larvicidal activity was 3μg/kg of body weight or more. Administrations of ivermectin at 0.5, 1 and 2μg/kg dose-relatedly showed incomplete antilarval activities. Administration of ivermectin at 0.5, 1 and 2μg/kg 30 days after infection caused lower levels of the sex ratios (female/male) than that of the control showing definite decrease in numbers of female worms. The average body lengths of both female and male worms recovered from dogs receiving ivermectin at 0.5, 1 and 2μg/kg, except for that of female worms at 1μg/kg, were significantly shorter than that of the worms recovered from the control dogs.

Prophylactic activity of ivermectin against Dirofilaria immitis infection in dogs: establishment of effective dose and administration schedule.

To establish a recommended dose and prophylactic program of ivermectin for preventing D. immitis infection, antilarval activity of ivermectin at 3 or 6μg/kg against one day, 30 and 60 days old larvae was evaluated. The worms were recovered from all dogs given ivermectin at 3μg/kg one day after inoculation with an average infection ratio of 21.9%. One male worm was recovered from one of 6 dogs given ivermectin at 3μg/kg 30 days after inoculation with an extremely low average infection ratio of 0.1%. Out of 6 dogs given ivermectin at 3μg/kg 60 days after inoculation, 3 animals yielded worms with a low infection ratio of 4.0%. The results suggest that ivermectin at 3μg/kg demonstrates incomplete antilarval activity against D. immitis larvae of one day, 30 and 60 days old and is not suitable to monthly or bimonthly interval mdication for preventing D. immitis infection. Small numbers of the worms were recovered from 5 of 6 dogs given ivermectin at 6μg/kg one day after inoculation with an average infection ratio of 5.7%. No worms were recovered from all dogs given ivermectin at 6μg/kg 30 and 60 days after inoculation. The results show that a single oral dose of ivermectin at 6μg/kg, though the dose demonstrates incomplete antilarval activity against one day old larvae, would be a recommended dose which can completely kill the larvae which are naturally infected at any time when the dose is given once a month at one month interval during the period from one month after the first infection to one month after the last infection of D. immitis.

Clinical application of milbemycin D as a prophylactic agent against Dirofilaria immitis infection in dogs: reactions in uninfected and infected dogs.

A dose of 1mg/kg or 5mg/kg of milbemycin D, a new prophylactic agent for Dirofilaria immitis (heartworm), was given to 201 dogs orally and the reaction was investigated by symptomatic, hematological and biochemical examinations. Dogs were divided into 3 groups: uninfected by heartworm (uninfected group), infected without circulating microfilaria (mf negative group), and infected with circulating mf (mf positive group). The incidence and degree of clinical signs were not clearly different with either dose. Vomiting and arrhythmia, which were noted to show about the same incidence in 3 groups, were seen in a total of 5 (2%) and 22 (11%) dogs, respectively. Body temperature and blood pressure fell slightly, and RBC count, serum total protein concentration, osmolality and sodium concentration were also slightly decreased 3 and/or 6 hr after administration in the uninfected and mf negative groups. Almost all of these changes remained within the normal ranges, and tended to recover 24 hr after administration. No other reactions were seen in the uninfected group. Loss of appetite, pale visible mucous membranes, shock-like reaction and dirofilarial hemoglobinuria (caval syndrome) were noted in a total of 5 (2%), 9 (5%), 9 (5%) and 8 (4%) dogs, respectively, which were seen mainly in the mf positive group. A significant decrease of circulating mf count, rise in body temperature, serum GOT, GPT and ALP activities were also observed 24 hr after administration in the mf positive group. Shock-like reaction was seen in a dog of the mf negative group, but in this case a small number of microfilariae were detected in the liver and lungs on histopathological examination. The effects of dead mf might be involved in the reaction of the mf positive group. From these results, it is considered that clinical application of milbemycin D for uninfected and mf negative dogs presents no risks, but adverse reactions may occur in dogs with microfilaremia.

Clinical application of milbemycin D as a prophylactic agent against Dirofilaria immitis infection in dogs: sensitivity for the drug in rough-coated collies.

To evaluate sensitivity owing to breed idiosyncrasy for milbemycin D (Milbe), 5 rough-coated collies and 7 Shiba dogs were treated with Milbe at a dose of 1.0mg/kg, 2.5mg/kg and 5.0mg/kg orally for 10 consecutive days. In the 5.0mg/kg dose of the collie group, neurologic signs such as arrhythmia, salivation, mydoriasis, staggering, recumbency, lethargy and so on occurred in 4 of 5 dogs after the 1st administration, and showed intermittently or continuously during the trial. The intensity of the neurologic signs was different in the individual dog and with the day of administration. The affected dogs recovered without treatment within 24 hr after the administration and no dog died.

塩酸レバミゾールの間欠投与による野外での犬糸状虫の予防効果

塩酸レバミゾールの間欠投与による野外での犬糸状虫の予防効果

塩酸レバミゾールの間欠投与による犬糸状虫の予防試験

塩酸レバミゾールの間欠投与による犬糸状虫の予防試験

Prophylactic efficacy of milbemycin D against Dirofilaria immitis infection in dogs.

To examine the prophylactic efficacy of milbemycin D against Dirofilaria immitis infection, 59 filaria-free beagles were inoculated with 50 to 100 infective larvae of the parasite. Milbemycin D was administered orally at ranges from 0.05 to 3.2 mg/kg of body weight one month after inoculation or at the rate of 1 mg/kg of body weight one to 90 days after inoculation. All dogs were sacrificed for autopsy 6 months after inoculation to confirm the establishment of D.immtis infection. Complete protection from the infection was observed by treating with a dose of 1 mg/kg or more of milbemycin D one or two months after infection.

Evaluation of protective immunity against experimental Dirofilaria immitis infection in Beagle dogs

Prevention of heartworm is a key goal of pet wellness. An experimental trial was carried out to induce the immunologic protection against Dirofilaria immitis infection in dogs during the period from July 2005 to November 2006. Â To evaluate the three protocols of immunization, dogs were separately immunized with gamma-irradiated infective larvae; with chemical abbreviation of infection; with chemical abbreviation plus Freund's complete adjuvant respectively. Each trial consisted of immunized and control groups and each group composed of two dogs. All dogs used for this study were subcutaneously challenged with 100 intact third-stage larvae at designated times after the last immunization following the above three protocols. The dogs were euthanized and necropsized between 120 to 175 days after challenge infection for the worms in the right ventricle of the heart and pulmonary arteries. Number of worms and sexes were determined. A mean of 36 worms from the immunized groups with irradiated L3; 33 worms from the chemically-abbreviated group whereas 13 worms from the chemical abbreviation plus Freund's complete adjuvant group were recovered. The percentages of the average protection in three groups were 45.80%, 55.05% and 77.90% respectively. The adjuvant enhanced the protective immunity against L3 challenge infection. The ELISA values do not explain the intensity of the protection, but shown adequately the immunized dogs responding to the immunization performed in this experiment. Key words: Heartworm, protective immunity, chemical-abbreviation, gamma-irradiated larvae DOI = 10.3329/bjvm.v5i1.1323 Bangl. J. Vet. Med. (2007). 5 (1 & 2): 93-98