Morphologic Changes in the Lungs of Cats Experimentally Infected With Dirofilaria immitis

The morphologic response of the pulmonary arteries and lungs in cats was studied after a five month heartworm infection produced by transplantation of four adult heartworms/cat. One group of seven heartworm infected cats was not treated, another group of seven cats was treated with 97.5 mg of aspirin given twice a week, and the third group of six cats was given aspirin at a sufficient dosage to block in vitro platelet aggregation throughout the study. A fourth group of eight noninfected cats served as controls. Five months after heartworm infection, the cats were euthanized and the lungs perfusion fixed for light microscopy and scanning electron microscopy of the pulmonary arterial surfaces. All cats in the three heartworm-infected groups had live heartworms and the typical pulmonary arterial changes of heartworm disease at necropsy. The arterial surfaces, as viewed with scanning electron microscopy, had villus proliferations that were more numerous and exuberant than similar infections in dogs. Mean percentage of arterial surface involvement with villus proliferation of the nontreated heartworm infected cats was 67.3%; the aspirin treated cats, 73.8%; and the adjusted aspirin treated cats, 75.9%. The villi were myointimal proliferations in the small and medium-sized arteries. The more elastic arteries had a predominance of fibromuscular proliferation. All heartworm infected cats had arterial muscular hypertrophy of the small arteries, in contrast to only three of eight of the nonheartworm infected cats. The caudal lobar arteries were frequently obstructed with either villus proliferation, thrombi, and/or dead heartworms. The muscular arteries had branches with marked dilation, a condition associated with pulmonary hypertension in man. However, only three cats, one in each group, had pulmonary hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genetic polymorphism in Dirofilaria immitis

Dirofilaria immitis is the causative agent of heartworm disease. Reports of macrocyclic lactone inefficacy prompted an investigation of genetic polymorphism in D. immitis. Currently, there is a lack of genetic information for this parasite. Information on baseline levels of genetic heterogeneity in the dog heartworm would have important implications for the possible development of macrocyclic lactone resistance in D. immitis. Genetic variability was investigated to assess the extent of genetic polymorphism in D. immitis populations from the USA (field and laboratory samples) and Japan (field samples). Single nucleotide polymorphisms (SNPs) were investigated in a full-length β-tubulin gene and segments of genes encoding heat shock protein 60 (Hsp60), a P-glycoprotein (Pgp), sarco-endoplasmic reticulum Ca(2+)ATPase (Serca) and phosphofructokinase (PFK). Significant differences in SNP frequencies were found in all genes except PFK. A combined genotype built from two SNPs from β-tubulin, Hsp60, Pgp and Serca was analyzed in the US lab, US field and Japan field samples. Some combined genotypes were unique to each sample group while others were shared between groups. F coefficients calculated for 15 SNPs from β-tubulin, Hsp60, Pgp and Serca were not in equilibrium. Differences in F coefficients were observed between the groups. D. immitis was found to be genetically heterogeneous. This genetic heterogeneity has implication for the development of genetically selected strains of the parasite.     

犬实验感染CDV的病理学研究

对实验感染犬瘟热病毒的病犬进行了系统的病理学观察,并用酶标ＳＰＡ法对病犬脏器组织中ＣＤＶ抗原进行了定位检查。结果表明,淋巴系统各器官组织是ＣＤＶ急性感染早期首先侵犯的靶器官。脏器组织的病理改变与ＣＤＶ抗原检出呈正相关。脏器组织中包涵体的检出与形态结构具有一定的特征性和示病意义,但采用免疫组化方法检查ＣＤＶ抗原,更具优越性。作者认为,ＣＤＶ９３０３９株和ＣＤＶ９３０４１株是致病力很强的泛嗜性ＣＤＶ。     

Macrocyclic lactone resistance in Dirofilaria immitis

Microfilariae were isolated from a Katrina rescue dog that remained microfilariaemic despite successful adulticidal treatments and repeated treatment with high doses of macrocyclic lactones (MLs). The microfilariae were genotyped at two P-glycoprotein single nucleotide polymorphic sites which had been found to correlate with reduced sensitivity to MLs. The genetic polymorphism (GG-GG), previously found to be associated with insensitivity to MLs in vitro, was present at a frequency of 45.3% in microfilariae that survived repeated treatments with high doses of ML anthelmintics. The data show phenotypic and genotypic evidence of ML resistance in Dirofilaria immitis.     

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.     

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.     

Immunological analysis of agglutination in Dirofilaria immitis microfllariae

The mechanism of agglutination phenomenon of Dirofilaria immitis microfilariae was analyzed. Circulating microfilariae were collected from a D. immitis-infected microfilaremic dog and cultured in the several kinds of sera from dogs and animals. The agglutination of D. immitis microfilariae is a specific phenomenon due to some immune complexes formed with the anti-microfilarial antibody, heat-instable factor(s) and excretory-secretory products of microfilariae. Only live microfilariae were agglutinated and the agglutinated microfilariae remained alive as long as 27 days in culture in vitro.     

Contractile activity of cultured adult Dirofilaria immitis

A method for long-term maintenance of adult heartworms (HW) in culture for use in contractile activity studies was developed. Culture conditions included Eagle's minimum essential medium (MEM) containing Earle's balanced salt solution and MEM vitamins and supplemented with 10% horse serum, pH 7.6, 37 degrees C, and humidified 5% CO2:95% room air atmosphere. Motility was observed for up to 91 days. Reducing the culture atmosphere from 20% oxygen to 5% oxygen reduced acid production and survival to 28 days or less. Spontaneous contractile activity of adult HW coils (1 cm diameter) was measured using an isometric force displacement transducer system. Activity had an arrhythmic pattern of good magnitude that could be recorded after up to 50 days in culture for male HW and after up to 40 days in culture for female HW. Analyses of contractile activity included determination of its amplitude, frequency, contraction index, and basal tension. Amplitude for males (3.4 +/- 1.2 g) (mean +/- S.D.) was significantly greater (P < 0.02) than that for females (3.0 +/- 1.1 g), whereas frequency for females (8.2 +/- 2.3 min) was significantly greater (P < 0.03) than that for males (7.5 +/- 2.3 min). The contraction index for females was 16.7 +/- 13.7 mm/min and for males, 14.4 +/- 9.0 mm/min. The difference was not significant. The contraction index was based on line integration of the record of contractile activity. Amplitude and frequency of contractile activity for anterior segments (2.5 cm), suspended lengthwise, from cultured adult female HW, were not significantly different from results for coils, but the contraction index (34.5 +/- 33.8) was significantly higher (P < 0.01) indicating that the pattern of activity was more uniform in the segments. An applied basal tension of about 4 g was suitable for the coils, while a suitable basal tension for segments was about 1.5 g. For coils, amplitude, frequency, and contraction index increased significantly (P < 0.02) with increase in basal tension. Coils were not sensitive to changes in ionic, glucose, oxygen, and osmol concentrations, and pH (6.8-7.6) of the bathing solution. A pH of 8.0 markedly increased basal tension and contractile activity. At 20 degrees C contractile activity stopped. These effects of pH and temperature were reversible. The HW appeared resistant to changes in their environment. This is probably related to an efficient cuticular barrier. The culture and recording methods used in this study open improved opportunities for quantitative evaluation of responsiveness of HW to a variety of physiological and pharmacological factors.     

The prevalence of Dirofilaria immitis in dogs in Sydney

Four hundred and four dogs from 9 pounds in Sydney were examined for circulating microfilariae and antigens of Dirofilaria immitis. One hundred of these were also examined post mortem for adult heartworms. The prevalence of infection in the 404 dogs as shown by serology was 11.4%, and 5.9% had circulating microfilariae of D immitis. Adult heartworms were present in 15 of 100 dogs. Dipetalonema reconditum microfilariae were present in 3.7% of dogs. Dirofilariosis is still a common and important parasite of dogs in the Sydney region and chemoprophylaxis is recommended.     

Surgical Extraction of Transplanted Adult Dirofilaria immitis in Cats

A jugular venotomy technique was developed to attempt extraction of Dirofilaria immitis in cats. Seven cats were first examined by cardiac ultrasound to establish the location of adult D. immitis that had been inserted by jugular venotomy. The efficiency of an extractor catheter in surgically removing filariae similarly inserted into 13 experimental cats was then assessed. A mean extraction success rate of 96% was achieved. This technique would seem to be worthy of clinical use provided the filariae are in the right atrial area.     

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.     

Vascular lesions of Dirofilaria immitis in the red fox

Dirofilaria immitis was found in the right ventricle, pulmonary artery, and lungs of 2 red foxes (Vulpes fulva) in Connecticut. The most significant lesions occurred in the pulmonary artery and consisted of focal atheromatous-like intimal plaques, diffuse subintimal accumulations of inflammatory cells, and marked villose endarteritis in the elastic portion of the pulmonary artery. Medial hyperplasia of the muscular branches, along with periarteritis, was found in 1 fox. These 2 cases may be a further indication of the increased incidence of this disease in Carnivora in the State of Connecticut.