Laboratory assays reveal diverse phenotypes among microfilariae of Dirofilaria immitis isolates with known macrocyclic lactone susceptibility status

Prevention of canine heartworm disease caused by Dirofilaria immitis relies on chemoprophylaxis with macrocyclic lactone anthelmintics. Alarmingly, there are increased reports of D. immitis isolates with resistance to macrocyclic lactones and the ability to break through prophylaxis. Yet, there is not a well-established laboratory assay that can utilize biochemical phenotypes of microfilariae to predict drug resistance status. In this study we evaluated laboratory assays measuring cell permeability, metabolism, and P-glycoprotein-mediated efflux. Our assays revealed that trypan blue, propidium iodide staining, and resazurin metabolism could detect differences among D. immitis isolates but none of these approaches could accurately predict drug susceptibility status for all resistant isolates tested. P-glycoprotein assays suggested that the repertoire of P-gp expression is likely to vary among isolates, and investigation of pharmacological differences among different P-gp genes is warranted. Further research is needed to investigate and optimize laboratory assays for D. immitis microfilariae, and caution should be applied when adapting cell death assays to drug screening studies for nematode parasites.

Seroprevalence of viral and vector-borne bacterial pathogens in domestic dogs (Canis familiaris) in northern Botswana

BACKGROUND

Domestic dogs (Canis familiaris) have the potential to act as disease reservoirs for wildlife and are important sentinels for common circulating pathogens. Therefore, the infectious disease seroprevalence among domestic dogs in northern Botswana may be indicative of pathogen exposure of various wildlife species. The objective of this study was to assess the seroprevalence of Ehrlichia spp., Borrelia burgdorferi, Anaplasma spp., Dirofilaria immitis, canine adenovirus, canine parvovirus, and canine distemper virus in domestic dogs as proxies of disease prevalence in the local wildlife in the Okavango Delta region of Botswana. Statistical analysis assessed crude and factor-specific seroprevalence proportions in relation to age, sex, and geographical location as predictors of seropositivity. Logistic regression was used to identify adjusted predictors of seropositivity for each of the pathogens of interest.

RESULTS

Samples from 233 dogs in a total of seven locations in Maun, Botswana, and surrounding villages were collected and serologically analyzed. No dogs were seropositive for B. burgdorferi, while low seroprevalence proportions were observed for Anaplasma spp. (2.2%) and D. immitis (0.9%). Higher seroprevalence proportions were observed for the tick-borne pathogen Ehrlichia spp. (21.0%), and 19.7% were seropositive for canine adenovirus (hepatitis). The highest seroprevalence proportions were for canine parvovirus (70.0%) and canine distemper virus (44.8%). The predictors of seropositivity revealed that adults were more likely to be seropositive for canine adenovirus, canine distemper virus, and canine parvovirus than juveniles, and location was a risk factor for canine adenovirus, canine distemper virus, canine parvovirus, and Ehrlichia spp.

CONCLUSIONS

Results indicate that increasing tick control and vaccination campaigns for domestic dogs may improve the health of domestic animals, and potentially wildlife and humans in the Okavango Delta since viral and vector-borne bacterial pathogens can be transmitted between them.

Variation in Tolerance to Parasites Affects Vectorial Capacity of Natural Asian Tiger Mosquito Populations

Globally, diseases transmitted by arthropod vectors, such as mosquitoes, remain a major cause of morbidity and mortality [1]. The defense responses of mosquito and other arthropod vectors against parasites are important for understanding disease transmission dynamics and for the development of novel disease-control strategies. Consequently, the mechanisms by which mosquitoes resist parasitic infection (e.g., immune-mediated killing) have long been studied [2, 3]. However, the ability of mosquitoes to ameliorate the negative fitness consequences of infection through tolerance mechanisms (e.g., tissue repair) has been virtually ignored (but see [4, 5]). Ignoring parasite tolerance is especially taxing in vector biology because unlike resistance, which typically reduces vectorial capacity, tolerance is expected to increase vectorial capacity by reducing parasite-mediated mortality without killing parasites [6], contributing to the recurrent emergence of vector-borne diseases and its stabilization and exacerbation. Despite its importance, there is currently no evidence for the evolution of tolerance in natural mosquito populations. Here, we use a common-garden experimental framework to measure variation in resistance and tolerance to dog heartworm (Dirofilaria immitis) between eight natural Aedes albopictus mosquito populations representing areas of low and high transmission intensity. We find significant inter-population variation in tolerance and elevated tolerance where transmission intensity is high. Additionally, as expected, we find that increased tolerance is associated with higher vectorial capacity. Consequently, our results indicate that high transmission intensity can lead to the evolution of more competent disease vectors, which can feed back to impact disease risk.

Effects of milbemycin oxime, combined with spinosad, when administered orally to microfilaremic dogs infected with adult heartworms (Dirofilaria immitis)

OBJECTIVE To evaluate the safety of PO administration of a milbemycin oxime (MBO) and spinosad product to heartworm (Dirofilaria immitis)-positive microfilaremic dogs. DESIGN Randomized, blinded, complete block trial. ANIMALS 32 purebred Beagles with a patent heartworm infection. PROCEDURES Dogs ranked by sex and microfilaria counts (range, 398 to 1,980 microfilaria/mL) were assigned to 4 groups of 8 to receive 3 treatments PO at 28-day intervals beginning on day 0: placebo (control group) or spinosad-MBO tablets containing MBO at the upper end of the label dose range (0.75 to 1 mg/kg [0.34 to 0.45 mg/lb]; 1× group) or 3 (3× group) or 5 (5× group) times that dose. Blood samples were collected at various points for adult heartworm antigen and Knott tests. Necropsies were performed on day 65, and recovered adult heartworms were counted. RESULTS 1 control dog died from heartworm-associated complications. Other adverse events included mild, transient emesis (1 dog in each of the 1× and 5× groups and 3 dogs in the 3× group). Similar adult heartworm counts (range, 13 to 41) were obtained for all 4 groups. Results of blood antigen and microfilaria tests were positive throughout the study, with 1 exception in each of the 3× and 5× groups. Mean microfilaria counts increased with time in the control group, whereas reductions from baseline in treated groups ranged from 61.5% to 96.4%. CONCLUSIONS AND CLINICAL RELEVANCE The evaluated MBO-spinosad formulation caused no severe adverse events when administered PO to microfilaremic dogs. Although microfilaria counts decreased following treatment, repeated monthly MBO treatments were incompletely microfilaricidal, suggesting MBO should not be used as a microfilaricide.

[(HUMAN DIROFILARIASIS: CLINICAL DIAGNOSTIC FEATURES ASSOCIATED WITH DIFFERENT DEVELOPMENTAL STAGES OF THE PATHOGEN)]

To seek medical advice is due to the time when a person has become infected during the infection transmission season (July-August) and the duration of development of the pathogen Dirofilaria (N.) repens in his/her body Clinical manifes- tations occurred in 61% of the patients 6-10 months after infection, as confirmed by the maximum body sizes (125-160 mm) of removed females which have reached puberty. PCR-based diagnosis in conjunction with microscopic studies improves the efficiency of identifying the patients and the species of the pathogens D.repens and D.immitis. The use of these methods for the first time in 2016 could confirm D.immitis infestation in a 14-month-old infant living in the Solnechnogorsk District, Moscow Region.

[(THE FAUNA OF BLOODSUCKING MOSQUITOES IN THE NIZHNY NOVGOROD REGION, THEIR INFECTION WITH DIROFILARIA AND ENDOSYMBIOTIC BACTERIA)]

The fauna of bloodsucking mosquitoes in the Nizhny Novgorod Region is represented by 11 species from 5 genera of the family Culicidae. During 2014-2015, the predominant species were Ochlerotatus cantans and Aedes cinereus mosqui- toes in both a population aggregate and woodland. The infected mosquitoes accounted for 1.3% of their total number and were registered only in the village of Fokino. The investigators identified two human pathogenic nematode species: Diro- filaria immits and Dirofilaria repens (0.9% and 0.4% respectively). The effective carriers of Dirofilaria in the examined area can be Ae.cinereus and Och.cantans as only these species were found to have an invasive stage of the parasite. The symbiotic bacterium Wolbachia was detected in the mosquitoes that were not infected with dirofilariasis. This is the first study in Russia to investigate the effects of Wolbachia on the susceptibility of dirofilariasis vectors to infection.

Dirofilaria in Humans, Dogs, and Vectors in Austria (1978-2014)-From Imported Pathogens to the Endemicity of Dirofilaria repens

Background

Dirofilaria repens and D. immitis are filarioid helminths with domestic and wild canids as main hosts and mosquitoes as vectors. Both species are known to cause zoonotic diseases, primarily pulmonary (D. immitis), ocular (D. repens), and subcutaneous (D. repens) dirofilariosis. Both D. immitis and D. repens are known as invasive species, and their distribution seems associated with climate change. Until very recently, both species were known to be nonendemic in Austria.

Methodology and Principal Findings

Metadata on introduced and possibly autochthonous cases of infection with Dirofilaria sp. in dogs and humans in Austria are analysed, together with analyses of mosquito populations from Austria in ongoing studies.

In Austria, most cases of Dirofilaria sp. in humans (30 cases of D. repens—six ocular and 24 subcutaneous) and dogs (approximately 50 cases—both D. immitis and D. repens) were most likely imported. However, occasionally infections with D. repens were discussed to be autochthonous (one human case and seven in dogs). The introduction of D. repens to Austria was confirmed very recently, as the parasite was detected in Burgenland (eastern Austria) for the first time in mosquito vectors during a surveillance program. For D. immitis, this could not be confirmed yet, but data from Germany suggest that the successful establishment of this nematode species in Austria is a credible scenario for the near future.

Conclusions

The first findings of D. repens in mosquito vectors indicate that D. repens presumably invaded in eastern Austria. Climate analyses from central Europe indicate that D. immitis also has the capacity to establish itself in the lowland regions of Austria, given that both canid and culicid hosts are present.

[INFECTION OF BLOOD-SUCKING MOSQUITOES (DIPTERA: CULICIDAE) WITH DIROFILARIAE (SPIRURIDA, ONCHOCERCIDAE) IN THE TULA REGION]

Blood-sucking mosquitoes (n = 2277) collected in Tula and its Region in 2013-2014 were examined using a PCR assay for dirofilariae. A total of 12 species from 4 genera (Culiseta, Aedes, Ochlerotatus [foreign character] Culex) out of 18 found mosquito species were infected with Dirofilaria immitis and D. repens. The proportion of the infected mosquitoes was 2.5% (D. immitis, 1.5%; D.repens, 1%). According to preliminary data, the most efficient Dirofilaria vectors, in the Tula Region may be Ae. vexans, Ae. geniculatus, Och. cantans, and Cx. pipiens.

Fibrinolysis and proliferative endarteritis: two related processes in chronic infections? The model of the blood-borne pathogen Dirofilaria immitis

The interaction between blood-borne pathogens and fibrinolysis is one of the most important mechanisms that mediate invasion and the establishment of infectious agents in their hosts. However, overproduction of plasmin (final product of the route) has been related in other contexts to proliferation and migration of the arterial wall cells and degradation of the extracellular matrix. We have recently identified fibrinolysis-activating antigens from Dirofilaria immitis, a blood-borne parasite whose key pathological event (proliferative endarteritis) is produced by similar mechanisms to those indicated above. The objective of this work is to study how two of this antigens [actin (ACT) and fructose-bisphosphate aldolase (FBAL)] highly conserved in pathogens, activate fibrinolysis and to establish a relationship between this activation and the development of proliferative endarteritis during cardiopulmonary dirofilariasis. We demonstrate that both proteins bind plasminogen, enhance plasmin generation, stimulate the expression of the fibrinolytic activators tPA and uPA in endothelial cell cultures and are located on the surface of the worm in contact with the host’s blood. ELISA, western blot and immunofluorescence techniques were employed for this purpose. Additionally, the implication of lysine residues in this interaction was analyzed by bioinformatics. The involvement of plasmin generated by the ACT/FBAL and plasminogen binding in cell proliferation and migration, and degradation of the extracellular matrix were shown in an “in vitro” model of endothelial and smooth muscle cells in culture. The obtained results indicate that ACT and FBAL from D. immitis activate fibrinolysis, which could be used by the parasite like a survival mechanism to avoid the clot formation. However, long-term overproduction of plasmin can trigger pathological events similar to those described in the emergence of proliferative endarteritis. Due to the high degree of evolutionary conservation of these antigens, similar processes may occur in other blood-borne pathogens.

Human and animal dirofilariasis: the emergence of a zoonotic mosaic

Dirofilariasis represents a zoonotic mosaic, which includes two main filarial species (Dirofilaria immitis and D. repens) that have adapted to canine, feline, and human hosts with distinct biological and clinical implications. At the same time, both D. immitis and D. repens are themselves hosts to symbiotic bacteria of the genus Wolbachia, the study of which has resulted in a profound shift in the understanding of filarial biology, the mechanisms of the pathologies that they produce in their hosts, and issues related to dirofilariasis treatment. Moreover, because dirofilariasis is a vector-borne transmitted disease, their distribution and infection rates have undergone significant modifications influenced by global climate change. Despite advances in our knowledge of D. immitis and D. repens and the pathologies that they inflict on different hosts, there are still many unknown aspects of dirofilariasis. This review is focused on human and animal dirofilariasis, including the basic morphology, biology, protein composition, and metabolism of Dirofilaria species; the climate and human behavioral factors that influence distribution dynamics; the disease pathology; the host-parasite relationship; the mechanisms involved in parasite survival; the immune response and pathogenesis; and the clinical management of human and animal infections.

Dirofilaria immitis in cats: diagnosis and management

Imaging and laboratory studies can help with the diagnosis of heartworm disease in cats, but no test is definitive. Furthermore, even when the diagnosis can be reliably established, therapy directed at the heartworms does little to help the cat. Rather, management is directed at alleviating clinical signs, with an emphasis on prevention for all.

Dirofilaria immitis in cats: anatomy of a disease

It is now understood that wherever heartworm infection exists in the local canine population, it will also be found in the feline population. However, this does not mean that the parasite and resulting disease behave the same way in both species. For example, heartworms rarely reach the adult stage in cats, but they can cause respiratory sequelae nonetheless.

Vascular endothelial cell activation by adult Dirofilaria immitis antigens

Dirofilaria immitis is the causal agent of cardiopulmonary dirofilariosis (heartworm disease). Adult worms lodge in the pulmonary arteries and right ventricle, thus vascular endothelium is exposed to high concentrations of Dirofilaria antigenic products. Heartworm disease habitually develops as a chronic foreseeable pathology. Moreover, the simultaneous death of many adult worms, naturally or induced by a filaricide treatment, can cause acute thromboembolisms and endarteritis. To better understand the effects of the massive death of D. immitis adult worms on the blood vessel endothelium, we cultured vascular endothelial cells in the presence or absence of an antigenic extract of D. immitis adult worms (DiSA). The parasite products increased the expression of enzymes and the synthesis of eicosanoids related to inflammation, such as COX-2, 5-LO, PGE(2) and LTB(4). The expression of ICAM-1 and PECAM-1 adhesion molecules and endothelial and inducible Nitric Oxide Synthases (eNOS and iNOS) was also increased in cultures treated with DiSA. Nevertheless, DiSA decreased endothelial permeability and does not alter both proliferation and apoptosis. These results suggest that the somatic extract of D. immitis adult worms stimulate inflammatory mechanisms in endothelial cells, without altering their basic physiologic processes.

Canine and feline dirofilariasis: life cycle, pathophysiology, and diagnosis

Infection with the intravascular parasite Dirofilaria immitis is an increasingly recognized problem in domestic dogs and cats. Heartworm infection is preventable; however, once an animal is infected, heartworm disease and potentially life-threatening complications can develop. An understanding of the heartworm life cycle and transmission season, the limitations of testing methods, and the clinical signs of heartworm disease is necessary to provide clients with appropriate information regarding prevention and treatment of heartworm infection in their pets.

Endogenous Lipid Pneumonia in a Dog

Endogenous lipid pneumonia has previously been diagnosed in dogs only once. This report describes a case in a dog with a persistent cough, in which the histological diagnosis was based on the presence of numerous foamy macrophages that filled the alveoli and contained small sudanophilic vacuoles. The appearance of endogenous lipid pneumonia in this animal was accompanied by Dirofilaria immitis infection and chronic bronchitis.

A preliminary study on in vitro transmission of Dirofilaria immitis infective stage larvae by Aedes aegypti (L.) (Diptera: Culicidae)

This study was performed to study an in vitro transmission of infective stage larvae from the mosquito proboscis. There were five experiments with 949 mosquitoes. Liverpool strain of Aedes aegypti (L.) were used in this study. They were allowed to feed on D. immitis infected dogs with different microfilarial levels which were 1,650, 1,950, 9,000, 9,250, and 11,550 microfilariae per one ml of blood. Mosquitoes were forced to feed on solution (5% sucrose in 5% dog serum) in capillary tubes for 20 minutes at 7-34 days post-blood feeding. Solutions in capillary tubes then were examined and mosquitoes were dissected and examined for D. immitis larvae under a light microscope. Second stage larvae could be found in the abdomen and malpighian tubules of mosquitoes and third stage larvae can be found in the abdomen, malpighian tubules, thorax, and proboscis of mosquitoes with different levels of infection. No larvae were detected in the solution in capillary tubes of all experiments.

A Dirofilaria immitis polyprotein up-regulates nitric oxide production

We investigated the effect of recombinant Dirofilaria immitis polyprotein (rDiAg) on nitric oxide (NO) production by peritoneal macrophages. rDiAg induced NO production by macrophages from wild-type and lipopolysaccharide-hyporesponsive C3H/HeJ, but not CD40(-/-), mice. These results suggest that CD40 is involved in rDiAg-driven NO production by murine macrophages.

Canine heartworm testing in Canada: are we being effective?

Mass testing of dogs in Canada for the presence of Dirofilaria immitis has been ongoing since 1977. Since that time, there have also been changes in the diagnostic tests available to detect the presence of heartworm and changes in the therapy for heartworm, which necessitate a reevaluation of heartworm screening as currently practiced in Canada. The principles of evidence-based medicine were used to determine the prevalence of heartworm infection in various dog populations, and the effectiveness of screening these populations. The annual surveys of heartworm testing have shown that Canada is a low prevalence area (0.16%), with most of the test-positive dogs located in southern Ontario (0.19%), southern Manitoba (0.18%), southern Quebec (0.09%), and the southern Okanagan Valley (0.04%). Foci of higher prevalence are found within these 4 main geographic areas. Furthermore, the prevalence of heartworm infection is higher in the population of dogs not on preventative medication (0.62%), when compared to the population of dogs on preventative medication (0.04%). The evidence indicates that a heartworm diagnostic test applied to an asymptomatic dog on preventative medication contributes little information regarding the heartworm infection status of that dog. However, testing of a dog characterized as being high risk will provide clinically useful information. Recommendations regarding the testing of dogs for heartworm in Canada are derived on the basis of available evidence.

Susceptibility of geographically distinct Aedes aegypti L. from Florida to Dirofilaria immitis (Leidy) infection

In the present study, five geographically distinct populations of Aedes aegypti L. from various regions of Florida were compared for their susceptibilities to Dirofilaria immitis (Leidy) infection. The populations were from Gainesville (North Central), Jacksonville (North Eastern), Naples (South Western), Sarasota (West Central), and Vero Beach (East Central). Mosquitoes of all the populations had fewer parasites in their Malpighian tubules 6 and 13 days after blood feeding compared to the number of microfilariae initially ingested. There was no significant difference in the mean number of the total parasites per female 6 and 13 days after taking an infectious blood meal. In comparison, significantly larger numbers of the microfilariae completed development in the laboratory-selected Vero Beach susceptible strain. Females excreted microfilariae within 72 hr. of engorgement on an infected dog and the Gainesville, Jacksonville, Naples, and Sarasota populations had 20-23% females that lacked ovarian development six days after blood feeding. Out of these, in 16-22% of the females from the Jacksonville, Naples, and Sarasota populations, parasite development was arrested mostly as moribund prelarvae and only few developing larvae were observed. All females of the Gainesville population that did not develop eggs (20%) also lacked parasites. In the Jacksonville population, 23% of the females that matured eggs had no infection. Eight percent of the females from the Sarasota population exhibited a similar response. Low survivorship was observed at 6 and 13 days after imbibing an infectious blood meal. Females showed melanization of microfilariae in the Malpighian tubules, on the midgut wall, and in the hemocoel. Cellular melanization response was observed in the hemocoel, whereas, a humoral melanization response was observed in the Malpighian tubules. The Vero Beach susceptible strain showed maximum vector efficiency and lowest survival at 13 days post-blood meal compared to the Jacksonville and the Gainesville populations.

Human dirofilariasis in the European Union

The dog parasites Dirofilaria immitis and D. (Nochtiella) repens, well known as zoonotic agents, are widely distributed in southern Europe. Although both species are canine parasites, infection with immature worms has been found in humans, who develop nodules, mainly in subcutaneous tissue or in lung parenchyma arising from branches of the pulmonary artery. In humans, the parasites do not usually reach the adult stage and microfilaremia is absent, as has been shown by diagnosis using invasive methods for removing the nodules. In this article, Antonio Muro, Claudio Genchi, Miguel Cordero and Fernando Simón review the current situation concerning the clinical and epidemiological aspects, immune response and diagnosis of human dirofilariases.

Mosquito frequency and feeding habits in an enzootic canine dirofilariasis area in Niterói, state of Rio de Janeiro, Brazil

Heartworm, a chronic fatal mosquito-borne canine disease, is frequently diagnosed in dogs from the State of Rio de Janeiro, where its prevalence is 29.7% in the city of Niterói. Nevertheless it is rarely detected in cats (0.8%) from the same state. Dogs are the primary source of infection to mosquitoes. because cats either do not demonstrate microfilaremia or it is too low and transient for transmission. A mosquito survey was conducted in Itacoatiara, Niterói, from March 1995 to February 1996, using canine, feline and human baits. A total of 21 mosquito species (3,888 females) was collected and biting frequency was higher at dusk. The four species collected most frequently (88.9%) were: Aedes taeniorhynchus (30% of the total catch; with the peak in May/June); Culex quinquefasciatus (22.5%; August/October); Aedes scapularis (19.4%; August, October/November and January) and Culex declarator (17%; November/January). Human baits were attractive to these species and dogs were significantly more attractive to them than cats. Ae. taeniorhynchus, Cx. quinquefasciatus, Ae. scapularis, Cx. declarator and Cx. nigripalpus are the most likely mosquito species to transmit Dirofilaria immitis parasites to dogs and may transit the parasite to humans. It is also suggested that the vector to cats belongs to the games Culex.

The effect of prostaglandin inhibition on the development of pulmonary pathology associated with dead Dirofilaria immitis

Flunixin meglumine was used to examine the effect of prostaglandin inhibition on the pathogenesis of Dirofilaria immitis in the pulmonary arteries of dogs. Immunopathological reactions to dead filariae were monitored by light and transmission electron microscopy and serology. Lung lesions in prostaglandin-inhibited dogs exposed to dead filariae were enhanced compared to control dogs. This was associated with the persistence of parasitic antigen in lung tissue and in the blood. Serology demonstrated that after insertion of D. immitis in treated dogs, antibody levels did not change, while immune complex and antigen levels increased. These results indicate that prostaglandin may have a protective effect on the way the lung reacts to dead D. immitis, and that altered dynamics of the antigen processing may well contribute to the associated lung lesions.

Experimental Dirofilaria immitis-associated glomerulonephritis induced in part by in situ formation of immune complexes in the glomerular capillary wall

Eight dogs were immunized with an aqueous-soluble extract of adult Dirofilaria immitis. Subsequent to at least 7-fold increases in antibody titer, the left renal artery of each dog was infused with 6 mg of D. immitis antigen. Fourteen days after infusion, the left kidney was compared to the right kidney and preinfusion biopsies. All dogs developed glomerular lesions in the left kidney characterized by 1 or more of the following: mesangial cell proliferation, neutrophil infiltration, increased periodic acid-Schiff-positive staining of the mesangium and glomerular basement membrane (GBM), fibrin deposition, and thickening of the GBM. Left kidney glomerular immunofluorescence was positive in 7 of the 8 dogs using polyclonal antisera for canine IgG and C3 in a linear or fine granular pattern. Ultrastructural lesions were present in the left kidney of all dogs and consisted of irregular GBM thickening, intramembranous and mesangial electron-dense deposits, and mesangial and endothelial cell proliferation. Antibodies directed against D. immitis antigen were demonstrated in all kidney eluates from the left kidney. The right kidneys of 3 of the dogs developed lesions; however, in comparison to the left kidney, the lesions in the right kidneys were inconsistent, mild, and focal. The histologic findings in the left kidney were similar to those observed in dogs with naturally occurring D. immitis infections. In sham-immunized control dogs, renal arterial infusion of D. immitis antigen did not cause consistent immune complex glomerulonephritis; however, antigen adherence to glomerular capillary walls was observed by immunofluorescent microscopy.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemocyte monophenol oxidase activity in mosquitoes exposed to microfilariae of Dirofilaria immitis

Monophenol oxidase (MPO) activity in hemocytes collected from Aedes aegypti Liverpool strain and Aedes trivittatus intrathoracically inoculated with saline alone, inoculated with Dirofilaria immitis microfilariae (mff), or from uninoculated mosquitoes was compared using a radiometric tyrosine hydroxylation assay. Hemocyte MPO activity in mff-inoculated (= immune-activated) mosquitoes was significantly increased at 24 hr postinoculation (PI) in A. aegypti and at 6, 12, and 24 hr PI in A. trivittatus as compared with saline-inoculated controls. Baseline and immune-activated levels of hemocyte MPO activity in A. trivittatus were significantly higher compared with those seen in A. aegypti. Baseline hemocyte population levels were similar in both species, but immune activation did not elicit increases in total hemocyte populations in A. trivittatus as has been demonstrated for A. aegypti. Likewise, immune activation by the inoculation of mff did not significantly alter plasma MPO activity in A. trivittatus as compared with uninoculated or saline-inoculated mosquitoes. Plasma MPO activity in A. aegypti, however, appears to constitute a major component of the immune response. The importance of phenol oxidase(s) in the immune response of mosquitoes against mff and the relationship of observed differences in MPO activity to differences in immunological capability between A. aegypti and A. trivittatus are assessed.

Smooth muscle proliferation in chronically injured canine pulmonary arteries is reduced by a potent platelet aggregation inhibitor U-53,059

Dirofilaria immitis (DI) infection chronically injures canine pulmonary arteries. This injury produces endothelial cell loss, platelet/leukocyte adhesion, and smooth muscle proliferation. In the present study we assessed the effect of the cyclooxygenase inhibitor, U-53,059, on platelet function, platelet kinetics, coagulation, and smooth muscle proliferation in DI infected dogs. Platelet aggregation to the combination of arachidonic acid/ADP was significantly inhibited by U-53,059. Coagulation and hematologic parameters were not effected by either DI infection or U-53,059 treatment. Platelet survival and the number of platelet dense granules were reduced in DI infection. Quantification of the lesions demonstrated that U-53,059 reduced both severity and density compared to non-treated dogs. U-53,059 is a potent and effective inhibitor of platelet aggregation which modifies smooth muscle proliferation produced by chronic vascular injury.

Recovery and viability of Dirofilaria immitis microfilariae

The viability of Dirofilaria immitis microfilariae recovered from canine blood by different methods was determined. Microfilaria recovery techniques included saponin lysis, saponin lysis with a trypsin treatment, dextran sedimentation and phytohemagglutinin treatment. Criteria for evaluating viability were microfilarial motility in vitro at 37 degrees C, microfilarial development in mosquitoes and the ability of microfilariae to circulate in mice. Although each method produced motile microfilariae, differences among groups of microfilariae recovered by different techniques were apparent by each of the criteria for viability. Saponin lysis gave superior yields of viable microfilariae.

Cryopreservation of Dirofilaria immitis microfilariae and third-stage larvae

Microfilariae of Dirofilaria immitis retained their infectivity for susceptible mosquitoes after cooling to -196 degrees C in the presence of 5% dimethylsulphoxide (Me2SO) using a two-step cooling sequence. Motility and in vitro development of cryopreserved microfilariae also compared favourably with unfrozen controls. Third-stage larvae frozen by the same cooling sequence in the presence of either 5% Me2SO or 16% hydroxyethyl starch were motile upon thawing. Thawed larvae completed the third- to fourth-stage moult in vitro at a frequency approximately 5 to 10% of that seen in unfrozen controls.