The Occurrence of Physaloptera hispida and a Mastophorus Sp. in Pulmonary Vessels of Hispid Cotton Rats (Sigmodon hispidus) from Georgia, U.S.A

During 2017-2018, a survey for the rat lungworm, Angiostrongylus cantonensis (Nematoda: Metastrongyloidea), in rodents from Piedmont and Lower Coastal Plains physiographic regions of Georgia was conducted. On 4 occasions, a single worm was recovered from the pulmonary vessels of a single cotton rat (Sigmodon hispidis). One of these worms was identified as a Physaloptera sp. and the remaining 3 as a Mastophorus sp. by morphology. No A. cantonensis were found. Physaloptera (Nematoda: Physalopteroidea) and Mastophorus species (Nematoda: Spiruroidea) are stomach parasites of many wild and domestic animals. This is the first report of these species in the pulmonary vessels of a definitive host. To better characterize these parasites, representative specimens were collected from cotton rat stomachs and identified morphologically and molecularly. Based on partial cytochrome c oxidase subunit 1 (COI) gene sequences, Physaloptera hispida from stomachs were identical to the Physaloptera sp. from the pulmonary vessels. The COI sequences from the Mastophorus sp. from the stomach exhibited a higher degree of variability but confirmed that the pulmonary worms were the same Mastophorus species. Furthermore, sequences of Mastophorus from a coastal site clustered separately from a clade of Mastophorus sequences from cotton rats from a Piedmont site. Our data show that adult worms recovered from pulmonary vessels of cotton rats could be either Physaloptera or Mastophorus sp., indicating that these parasitic worms are not always restricted to the stomach and that worms from pulmonary vessels must be carefully examined to obtain a definitive diagnosis of A. cantonensis infection.

Infection by and Molecular Features of Learedius learedi (Digenea: Schistosomatoidea) in Green Sea Turtles (Chelonia mydas) on the Ogasawara Islands, Japan

Learedius learedi Price, 1934 , is a blood fluke found in sea turtles, and the adult fluke parasitizes the cardiovascular system of the host. In this study we surveyed 46 green sea turtles, Chelonia mydas, on the Ogasawara Islands, Japan, and blood flukes were detected in the heart and blood vessels of 26 turtles. The flukes were identified as L. learedi based on a detailed morphological description. In addition, molecular identification and characterization of the parasite were performed. The nucleotide sequences of nuclear internal transcribed spacer 2 (ITS2) regions were almost identical to those of L. learedi reported previously, but not to those of Hapalotrema spp., which is the closest related genus. The nucleotide sequences of the 28S ribosomal DNA region formed a single clade with those of the reference L. learedi in the phylogenetic tree, but not with those of Hapalotrema spp. Therefore, the nucleotide sequences of ITS2 and 28S are robust markers for distinguishing L. learedi from other species. The nucleotide sequences of the mitochondrial cytochrome c oxidase subunit 1 (COI) region were analyzed to evaluate the genetic variations in L. learedi. The COI haplotypes revealed the extremely high genetic diversity of the species as well as the host turtles on the Ogasawara Islands. The haplotype frequency in the mitochondrial DNA of the green sea turtles on the Ogasawara Islands is known to be significantly different from those in other Pacific rookeries. Although the number of analyzed flukes is small in this study, no haplotype was close to that in other areas; on the basis of the data, we hypothesized that L. learedi differentiated along with the host turtles on the Ogasawara Islands.

High prevalence of Angiostrongylus cantonensis (rat lungworm) on eastern Hawai'i Island: A closer look at life cycle traits and patterns of infection in wild rats (Rattus spp.)

The nematode Angiostrongylus cantonensis is a zoonotic pathogen and the etiological agent of human angiostrongyliasis or rat lungworm disease. Hawai'i, particularly east Hawai'i Island, is the epicenter for angiostrongyliasis in the USA. Rats (Rattus spp.) are the definitive hosts while gastropods are intermediate hosts. The main objective of this study was to collect adult A. cantonensis from wild rats to isolate protein for the development of a blood-based diagnostic, in the process we evaluated the prevalence of infection in wild rats. A total of 545 wild rats were sampled from multiple sites in the South Hilo District of east Hawai'i Island. Adult male and female A. cantonensis (3,148) were collected from the hearts and lungs of humanely euthanized Rattus rattus, and R. exulans. Photomicrography and documentation of multiple stages of this parasitic nematode in situ were recorded. A total of 45.5% (197/433) of rats inspected had lung lobe(s) (mostly upper right) which appeared granular indicating this lobe may serve as a filter for worm passage to the rest of the lung. Across Rattus spp., 72.7% (396/545) were infected with adult worms, but 93.9% (512/545) of the rats were positive for A. cantonensis infection based on presence of live adult worms, encysted adult worms, L3 larvae and/or by PCR analysis of brain tissue. In R. rattus we observed an inverse correlation with increased body mass and infection level of adult worms, and a direct correlation between body mass and encysted adult worms in the lung tissue, indicating that larger (older) rats may have developed a means of clearing infections or regulating the worm burden upon reinfection. The exceptionally high prevalence of A. cantonensis infection in Rattus spp. in east Hawai'i Island is cause for concern and indicates the potential for human infection with this emerging zoonosis is greater than previously thought.

Use of a commercial serologic test for Angiostrongylus vasorum for the detection of A. chabaudi in wildcats and A. daskalovi in badgers

Three species of the genus Angiostrongylus are known to infect European carnivores: A. vasorum (mainly in canids but also in other carnivores), A. chabaudi (in felids) and A. daskalovi (in mustelids). A. vasorum is responsible for clinically severe disease in domestic dogs, most commonly diagnosed based on fecal examination and serological detection of circulating antigens. Considering the poorly known host range and the challenging larval differentiation in the feces between the three species of Angiostrongylus infecting European carnivores, our aim was to evaluate the cross-reactivity of A. chabaudi and A. daskalovi with A. vasorum using a commercial serologic test developed for domestic dogs. Badgers (Meles meles) (n=10) and wildcats (Felis silvestris) (n=8) were examined between 2015 and 2016 by full parasitological necropsy with subsequent morphological and molecular identification of nematodes and by serology, using IDEXX Angio Detect™ tests. Five out of the ten badgers and two out of the eight wildcats were harboring nematodes in the pulmonary arteries. All nematodes were identified morphologically as A. daskalovi in badgers and A. chabaudi in wildcats, respectively. Serological examination of the plasma samples revealed the positivity of the same animals as found in necropsy. None of the animals negative at necropsy was positive at serology. The 100% correlation between the necropsy results and the serologic positivity to IDEXX Angio Detect™ in badgers infected with A. daskalovi and wildcats infected with A. chabaudi suggest that these rapid tests are able to identify circulating antigens of all species of Angiostrongylus found in European carnivores: A. vasorum, A. daskalovi and A. chabaudi. The possibility for future in-clinic use of this test in domestic cats should be further investigated.

Hepatic Shunting of Eggs and Pulmonary Vascular Remodeling in Bmpr2(+/-) Mice with Schistosomiasis

RATIONALE

Schistosomiasis is a major cause of pulmonary arterial hypertension (PAH). Mutations in the bone morphogenetic protein type-II receptor (BMPR-II) are the commonest genetic cause of PAH.

OBJECTIVES

To determine whether Bmpr2(+/-) mice are more susceptible to schistosomiasis-induced pulmonary vascular remodeling.

METHODS

Wild-type (WT) and Bmpr2(+/-) mice were infected percutaneously with Schistosoma mansoni. At 17 weeks postinfection, right ventricular systolic pressure and liver and lung egg counts were measured. Serum, lung and liver cytokine, pulmonary vascular remodeling, and liver histology were assessed.

MEASUREMENTS AND MAIN RESULTS

By 17 weeks postinfection, there was a significant increase in pulmonary vascular remodeling in infected mice. This was greater in Bmpr2(+/-) mice and was associated with an increase in egg deposition and cytokine expression, which induced pulmonary arterial smooth muscle cell proliferation, in the lungs of these mice. Interestingly, Bmpr2(+/-) mice demonstrated dilatation of the hepatic central vein at baseline and postinfection, compared with WT. Bmpr2(+/-) mice also showed significant dilatation of the liver sinusoids and an increase in inflammatory cells surrounding the central hepatic vein, compared with WT. This is consistent with an increase in the transhepatic passage of eggs.

CONCLUSIONS

This study has shown that levels of BMPR-II expression modify the pulmonary vascular response to chronic schistosomiasis. The likely mechanism involves the increased passage of eggs to the lungs, caused by altered diameter of the hepatic veins and sinusoids in Bmpr2(+/-) mice. Genetically determined differences in the remodeling of hepatic vessels may represent a new risk factor for PAH associated with schistosomiasis.

Angiostrongylus vasorum infection in red foxes (Vulpes vulpes) in southern Italy

Angiostrongylus vasorum (Nematoda: Angiostrongylidae) infection was detected at post-mortem examination in the pulmonary arteries and hearts of 34/102 (33,3%) of red foxes (Vulpes vulpes) from the Campania Region in southern Italy. Pathological changes consisted of granulomatous interstitial pneumonia caused by larvae and intravascular pulmonary adult nematodes. These changes confirm that angiostrongylosis infection in red foxes has a mainly chronic course, in which the infected host may disperse parasite larvae in the environment over its lifetime. Results suggest that the life cycle of A. vasorum is well established in the red fox in the Campania Region representing a potential infection risk for dogs.

Case Report of dirofilariasis in grey wolf in Serbia

This paper describes a case of dirofilariasis in a two-year old, female grey wolf (Canis lupus lupus). The autopsy revealed the presence of 42 adult forms of Dirofilaria immitis in the pulmonary artery, right ventricle and right atrium, varying in length from 9.5 to 30 cm. This is, to the best of our knowledge, the second report of D. immitis in grey wolves in Serbia. Our finding confirms that the wolf, as a subspecies distinct from the dog, should also be considered as a very suitable definitive host for dirofilariasis.

First report of Angiostrongylus cantonensis (Nematoda: Angiostrongylidae) infections in invasive rodents from five islands of the Ogasawara Archipelago, Japan

BACKGROUND

Angiostrongylus cantonensis (Chen, 1935) is a parasite of murid rodents and causative agent of human neuro-angiostrongyliasis. In 2011, the Ogasawara Islands in the western North Pacific were assigned a World Natural Heritage site status. The occurrence of A. cantonensis is well documented in the Chichijima, Hahajima, and Anijima Islands. However, the occurrence of A. cantonensis in the other islands of the Ogasawara Islands has not been reported.

METHODOLOGY/PRINCIPAL FINDINGS

Between March 2010 and July 2011, 57 Rattus norvegicus and 79 R. rattus were collected from 9 islands (the Hahajima group: Anejima, Imoutojima, Meijima, Mukohjima, and Hirajima; Chichijima group: Minamijima; Mukojima group: Nakoudojima and Yomejima; and Iwojima group: Iwojima). Adult nematodes were found in the pulmonary artery of 46 R. norvegicus collected in the 5 islands of the Hahajima group (Anejima, Meijima, Imoutojima, Hrajima, and Mukohjima Islands). These nematodes were identified by molecular analysis as A. cantonensis. Comparison of the mitochondrial DNA sequences confirmed that all the samples from the Ogasawara Islands shared only a single lineage of A. cantonensis, which has been previously detected in the Okinawa, Hawaii, and Brazil.

CONCLUSIONS/SIGNIFICANCE

We describe new endemic foci of rat angiostrongyliasis in the Hahajima group (Anejima, Meijima, Imoutojima, Hirajima, and Mukohjima Islands) of the Ogasawara Islands. These findings indicate that the endemic foci of A. cantonensis are widely distributed in the Ogasawara Islands. Although human cases have not yet been reported in the Ogasawara Islands, the widespread detection of A. cantonensis could be of importance from the perspective of public health.

[Hydatic pulmonary embolism: a rare complication of hepatic hydatid cyst]

Hepato-pulmonary hydatidosis is a parasitic disease common in Mediterranean countries. Hydatid pulmonary embolism is extremely rare and is due to rupture of a cardiac hydatid cyst or, more rarely, rupture of a hepatic hydatid cyst. We report three cases of hydatid pulmonary embolism secondary to rupture of a hydatid cyst into the inferior vena cava. Thoracic imaging, mainly CT angiography and MRI, was important for both the diagnosis and decisions on treatment. The prognosis of intra-arterial pulmonary hydatid cyst is poor because of the risk of acute fatal complications such as anaphylactic shock and vascular rupture and also of chronic progression to cor pulmonale and respiratory failure. The therapeutic management is difficult and often only partially effective hence the importance of focusing on preventative treatment.

Embolisation of hydatid cysts in the pulmonary artery presenting with haemoptysis

A 49-year-old female patient who had undergone surgery for hepatic echinococcosis five years previously was admitted with haemoptysis. MRI angiography showed total occlusion of the left inferior pulmonary artery. Echocardiography showed no pulmonary hypertension. The patient underwent pneumonectomy and cysts in the left pulmonary artery were observed. Pulmonary artery involvement should be considered in patients who have undergone hepatic cyst surgery if haemoptysis is the first presenting symptom, especially in endemic regions for hydatidosis.

A two-stage approach to a patient with hydatid cysts inside the right pulmonary artery and multiple right lung involvement

We report on the surgical treatment of a patient in whom hydatid cysts inside the right pulmonary artery and multiple right lung involvement were detected. Since the right pneumonectomy carried a high risk of cyst rupture, and migration of the cysts to the opposite lung during ligation of the pulmonary artery, a two-stage surgical approach was scheduled. Hydatid cysts located at the proximal pulmonary artery were removed by performing a longitudinal arteriotomy along the pulmonary artery to the bifurcation. Subsequently, a right pneumonectomy was performed on a safe right pulmonary artery in a different session.

[Cardiac hydatidosis with dissemination to the pulmonary parenchyma and the pulmonary artery]

Multiple thoracic hydatic disease involving a cardiac and pulmonary localization is exceptional and prognosis is poor. We report a case in a 21-year-old male who presented repeated episodes of hemoptysis. The chest x-ray showed multiple opacities. The thoracic computed tomography and echocardiography visualized cystic formations in the heart and the pulmonary arteries. Hydatic serology was strongly positive. Medical treatment with albendazole was given but the patient died from massive hemoptysis before the cardiac and pulmonary artery cysts could be removed surgically (a procedure which requires extracorporeal circulation). A hydatic cyst of the pulmonary artery is usually secondary to a cardiac localization. The risk is dissemination into the pulmonary and eventually systemic circulation. An arterial localization must be carefully ruled out in all patients with multiple or cardiac hydatidosis. Treatment is surgical to avoid dissemination.

Hydatid cyst of the pulmonary artery secondary to hepatic hydatid cyst embolism

A cystic lesion of the liver extending into the inferior vena cava was discovered in a 33-year old female patient suffering from dyspnea, pain and swelling in the legs. Plain chest X-ray was normal. CT and MRI of the thorax showed a cystic lesion within the right pulmonary artery. The liver lesion was treated by a partial cystectomy and omentoplasty, inferior vena cava and bile ducts repair. Through a right thoracotomy, a hydatid cyst was found in the pulmonary artery and enucleated. Although very rare, pulmonary artery hydatidosis may be the cause of an unexplained dyspnea in patients with hydatidosis of the liver.

Hydatid cysts of the bilateral pulmonary arteries and left ventricle wall: computed tomography and magnetic resonance imaging findings

Echinococcal cysts located inside the pulmonary artery are extremely rare. The cause is usually rupture of intracardiac cysts or, more rarely, dissemination from a hepatic focus. The case of a 39-year-old patient with multiple hydatid cysts in the right and left pulmonary arteries and left ventricle wall is reported. The patient had undergone surgery for a hepatic hydatid cyst 10 years ago. Multidetector computed tomography angiography and magnetic resonance imaging were performed for the diagnostic evaluation.

Dirofilaria immitis: worm burden and pulmonary artery proliferation in dogs from Michigan (United States)

Despite the ability to prevent heartworm disease, infection with Dirofilaria immitis continues to be a major problem for domestic dogs. To determine worm burden in heartworm-positive dogs from three county animal shelters in the state of Michigan in the United States and to assess the relationship between gross intimal proliferation and worm burden, necropsy was done on 176 heartworm-positive dogs. Adult heartworms were found in the heart and pulmonary artery of 170 of the 176 (96.6%) dogs examined. Mean worm burden was 14 +/- 13 (range 0-85). Fifty-nine percent of dogs had < or =10 heartworms. In contrast, 52% of dogs in a published report from the southern US (Florida) had worm burdens >10 [C.H. Courtney, Q.Y. Zeng, The structure of heartworm populations in dogs and cats in Florida, in: Proceedings of the American Heartworm Symposium, 1989]. These data suggest that mean worm burden in northern areas may be < or = that in warmer areas. Also, since diagnostic tests are less sensitive with lower worm burdens, diagnosis of heartworm infection in Michigan and other surrounding more northern states may be a greater challenge than in areas with higher worm burdens.

Specific IgG antibody response against antigens of Dirofilaria immitis and its Wolbachia endosymbiont bacterium in cats with natural and experimental infections

Sera from three groups of cats under different experimental conditions were studied by ELISA to assess the host's immune response against synthetic peptides derived from Dirofilaria immitis (Dipp) and against the surface protein of its endosymbiont, Wolbachia (WSPr). In experimentally infected cats (Group 1), an increase of IgG antibody against both Dipp and WSPr was observed from 2 months post-infection until the end of the study, 6 months post-infection. In experimentally infected cats, treated against infective larvae (Group 2), anti-Dipp IgG decreased dramatically from 4 months post-infection (3 months post treatment), showing very low values till the end of the study (6.5 months from infection, 5.5 months from treatment), while anti-WSP IgG increased constantly till the end of the study. Of 49 outdoor, asymptomatic cats exposed to a high risk of natural infection (Group 3), 9 were positive for anti-Dipp IgG and for a validated, in-clinic commercial antibody diagnostic kit for cats. Two cats were also found positive for circulating antigens of adult female worm. Anti-WSPr IgG were found in five of nine anti-Dipp IgG-positive sera and from eight ELISADipp-negative sera. Our results confirm the strong IgG response in heartworm infected cats and demonstrate the involvement of the Wolbachia endosymbiont in the immune reaction to the parasite both in experimentally infected cats and in cats exposed to a high risk of natural infection.

[Presence of Angiostrongylus cantonensis in Haiti]

In the West Indies Angiostrongylus cantonensis was found first in Cuba in 1973, then in Puerto Rico (1986), in the Dominican Republic (1992) and recently in Jamaica (2002). Concurrently, the presence of the parasite was detected in the Bahamas and in New Orleans (LA, USA) in 1990. To assess the occurrence of A. cantonensis in Haiti, we investigated a number of rats in Port-au-Prince in 2002. Preliminary results among 23 captured and examined rats show that 75% (three of four) Rattus norvegicus and 21% (four of 19) R. rattus harboured A. cantonensis in their cardiopulmonary systems. Haiti is, for the first time, recognized as a new enzootic area for A. cantonensis in the Caribbean. This emerging zoonosis should be considered as a new public health hazard in Haiti.

Kinetics of eosinophil and IgE-mast cell changes following infection with Angiostrongylus costaricensis in Wistar rats

Human abdominal angiostrongyliasis is a severe eosinophilic disease caused by Angiostrongylus costaricensis. Previous studies have demonstrated that wild rodents are critically involved as definitive hosts to this nematode in nature. In this study, we have evaluated the susceptibility of Wistar rats (Rattus norvegicus) to A. costaricensis infection. Kinetics of parasitological and pathological changes, including the number of adult worms recovered from mesenteric arteries, and of IgE, mast cell and eosinophil levels in several compartments have been assessed. The oral inoculation of third-stage larvae (L3) into adult Wistar rats led to a marked accumulation of worms in the branches of the mesenteric arteries 25 and 50 days post-inoculation. Intense bone marrow eosinophilia ranging from 7 to 50 days was accompanied by marked accumulation of eosinophils in the blood, peritoneal and bronchoalveolar spaces. Eosinophilic periarteritis, oedema and granuloma in the intestinal and lung tissues were also histologically evident. Total serum IgE and specific anti-parasite IgE peaked at 25 days post-infection, as measured by ELISA and by the passive cutaneous anaphylaxis test, respectively. At that time point, there was a drastic reduction in the number of intact mast cells in the peritoneal effluent. These findings indicate that Wistar rats are permissive to A. costaricensis infection. IgE-mast cell activation and massive tissue eosinophil infiltration are marked features in the process and are likely to play a crucial role in the immune-response evoked by this parasite.

Echinococcus of the pulmonary artery: CT, MRI and MRA findings

The location of echinococcal cysts inside pulmonary artery is extremely rare. The cause is usually rupture of intracardiac cysts. We report a case of a 67-year-old patient with known lung hydatid disease whose main clinical presentation was dyspnea. The patient did not have any surgery in the past. The importance of the present case lies in the demonstration of the MR angiographic findings.

Comparison of laboratory test results before and after surgical removal of heartworms in dogs with vena caval syndrome

OBJECTIVE

To compare results of laboratory tests in dogs with vena caval syndrome before and after surgical removal of heartworms.

DESIGN

Longitudinal uncontrolled clinical trial.

ANIMALS

51 dogs with vena caval syndrome.

PROCEDURE

Heartworms were removed from the area of the tricuspid valve and pulmonary arteries via venotomy and by use of flexible alligator forceps. Blood samples were obtained before and 10 days after removal of heartworms. Red and white blood cell counts were determined, using an automated cell counter. Biochemical tests were performed, using a dry chemical method.

RESULTS

45 dogs survived the procedure, and 6 died or were euthanatized after surgical treatment. After surgery, RBC count and total protein, albumin, calcium, and sodium concentrations increased, and total bilirubin, ammonia, BUN, creatinine, uric acid, and potassium concentrations decreased in dogs that survived. Creatine kinase, L-lactate dehydrogenase, and amylase activities decreased, whereas alkaline phosphatase and gamma-glutamyltransferase activities and total cholesterol concentration increased. Alanine transaminase activity decreased in 27 dogs but increased in 3 dogs. Changes in test results in dogs that did not survive. Significant differences were found in RBC count, gamma-glutamyltransferase activity, and total protein, total cholesterol, BUN, and total bilirubin concentrations before and after removal of heartworms.

CLINICAL IMPLICATIONS

Hepatic and renal functions improve rapidly after surgical removal of heartworms, presumably because general and pulmonary circulation is normalized. However, cholestasis may develop, and dogs that survive may need additional treatment to preserve hepatic function.

Hapalotrema (Digenea: Spirorchidae) in the green turtle (Chelonia mydas) in Australia

Hapalotrema mehrai Rao, 1976 and Hapalotrema postorchis Rao, 1976 (Digenea: Spirorchidae) are redescribed from the heart and pulmonary arteries of the green turtle, Chelonia mydas, from Moreton Bay in south-eastern Queensland. Hapalotrema pambanensis Gupta and Mehrotra, 1981 from C. mydas in India is made a synonym of H. mehrai. Hapalotrema dorsopora Dailey, Fast and Balazs, 1993 from C. mydas from Hawaii was described with a dorsally opening uterine pore, but this is found to be the opening of Laurer's canal; therefore H. dorsopora is also made a synonym of H. mehrai. In addition to differences in the numbers of testes and general dimensions, H. mehrai and H. postorchis differ in the development of Laurer's canal and in the absence of a canalicular seminal receptacle in H. postorchis.

Effect of arsenical drugs on in vitro vascular responses of pulmonary artery from heartworm-infected dogs

OBJECTIVE

To test the effect of thiacetarsamide and melarsomine on vascular responses in isolated rings of pulmonary artery from heartworm-infected dogs.

ANIMALS

18 heartworm-infected dogs.

PROCEDURE

Isolated rings of pulmonary artery from heartworm-infected dogs were randomly treated with thiacetarsamide (30 micrograms/ml) or melarsomine dihydrochloride (30 micrograms/ml) for 30 minutes; untreated rings from the same dog served as control. Cumulative dose-response relations to norepinephrine, nitroglycerin, and methacholine were determined.

RESULTS

Norepinephrine-induced constriction was not altered by treatment with either thiacetarsamide or melarsomine. Treatment with thiacetarsamide depressed nitroglycerin-induced relaxation, compared with values for untreated control rings and rings treated with melarsomine. Treatment of rings with thiacetarsamide or melarsomine depressed methacholine-induced relaxation, compared with values for untreated rings. Histologic examination of rings indicated that treatment with thiacetarsamide or melarsomine resulted in loss of endothelial cells.

CONCLUSION

Endothelial cell loss as a direct drug effect may be responsible for impaired endothelium-dependent relaxation in pulmonary artery from heartworm-infected dogs. Thiacetarsamide appears to have additional effects on vascular smooth muscle, which may explain why fewer complications are observed in dogs treated with melarsomine.

CLINICAL RELEVANCE

Melarsomine may be a safer drug than thiacetarsamide and could be a better treatment for dogs with heartworm infection.

Effect of heartworm infection on in vitro contractile responses of canine pulmonary artery and vein

OBJECTIVE

To test the effect of heartworm infection on agonist-induced constriction of canine pulmonary artery and vein in vitro.

PROCEDURE

Cumulative concentration-response relations to norepinephrine, serotonin, histamine, prostaglandin F2 alpha, and the thromboxane A2 analog U-44069 were determined, using isolated rings of pulmonary artery and vein from control and heartworm-infected dogs. To determine the role of endothelial cells in histamine constriction, some rings were denuded of endothelial cells in both artery and vein.

ANIMALS

Noninfected control and heartworm-infected dogs.

RESULTS

There was no difference in constriction response to norepinephrine, serotonin, prostaglandin F2 alpha, or U44069 of pulmonary artery or vein from control or heartworm-infected dogs. Histamine-induced constriction of pulmonary artery from heartworm-infected dogs was not different from control values, however, when endothelial cells were removed from control, but not heartworm-infected pulmonary artery, histamine-induced constriction was enhanced. Histamine-induced constriction of pulmonary vein from heartworm-infected dogs was significantly depressed, compared with that of control pulmonary vein. However, removal of endothelial cells in pulmonary vein from heartworm-infected, but not control dogs significantly increased constriction.

CONCLUSION

Heartworm infection alters histamine-induced constriction responses of pulmonary artery and vein. These changes may reflect high circulating histamine concentrations in heartworm-infected dogs, compared with that in controls. Increased circulating histamine concentrations in vivo could bring about decreased sensitivity of histamine receptors o decreases in the number of receptors expressed.

CLINICAL RELEVANCE

Mast cells and histamine may be important factors in altered endothelium-mediated responses associated with heartworm disease.

Re-migration of fifth-stage juvenile Dirofilaria immitis into pulmonary arteries after subcutaneous transplantation in dogs, cats, and rabbits

An assessment was made of the capacity for re-migration of the 5th-stage juvenile canine heartworm, Dirofilaria immitis. Live, 5th-stage juvenile worms recovered from the pulmonary arteries of infected dogs were transplanted into the subcutaneous tissue of uninfected dogs, cats, and rabbits. A mean of 45%, 61%, and 18% of the transplanted worms were recovered from the pulmonary arteries of dogs, cats, and rabbits, respectively, 1 and 3 mo later. The 5th-stage juvenile worms thus have the ability to re-migrate through tissue into the pulmonary arteries of the host.

[The mechanism of distant metastases of alveolar hydatid disease]

The mechanism of the distant metastasis of echinococcosis was investigated using jirds (Meriones unguiculatus) by inoculation of fractions obtained from echinococcal lesions formed in the peritoneal cavity of cotton rats (Sigmoid hispidus). Protoscoleces, cysts, and germinal cells were fractionated from the peritoneal lesions of the cotton rats injected peritoneally with echinococcal germinal cells. Each fraction (protoscoleces; 500 pieces, cysts; 50 pieces, germinal cells; 2 x 10(7) cells) suspended in 0.2 ml of PBS was injected into either the left inguinal vein (IV group) or the mesenteric vein (MV group) of seven week-old jirds. Eight weeks after the injection, the jirds were sacrificed and examined macroscopically and microscopically. In IV group, one of 10 jirds had echinococcal lesions in lung, bilateral adrenal, brain, para-aortic lymph node and left inguinal lymph node by inoculation of only germinal cells. Another one had lung lesions formed by cysts inoculated. In MV group, both intrahepatic and pulmonary echinococcal lesions by inoculation of germinal cells were observed in 3 out of 5 jirds. Cysts inoculated formed intrahepatic lesions in all 5 jirds. However, protoscoleces inoculated through both routes never formed echinococcal lesions in any organs. The typical lesions of echinococcosis were observed in all lesions without protoscoleces and calcification. These results indicate that germinal cells in intrahepatic echinococcal lesions might invade into the intrahepatic vein and metastasize to other organs.

Pulmonary dirofilariasis in a Japanese hare, Lepus brachyurus angustidens

A case of pulmonary dirofilariasis in a Japanese hare, Lepus brachyurus angustidens captured in Aomori Prefecture, was first reported in Japan. Two dead worms recovered from the pulmonary artery and detected within an organized arterial thrombus in the lung, were identified as a male and a female young adult Dirofilaria immitis, respectively. Principal lesions in the lung were associated with pulmonary arterial degeneration and consisted of rugose and villous intimal fibrosis, endarteritis with infiltration by numerous eosinophils and mononuclear inflammatory cells, and thrombosis.

Effects of PF1022A on adult Angiostrongylus cantonensis in the pulmonary arteries and larvae migrating into the central nervous system of rats

We examined the effects of PF1022A, newly developing in Japan, on adult Angiostrongylus cantonensis in the pulmonary arteries of rats. Following five and ten successive oral doses at 10 mg/kg per day, the first-stage larvae in rat faeces disappeared completely at 2 weeks after treatment. The treatment completely killed the female worms, but not the male worms. However, numbers of male worms were also decreased after the administration of either five successive oral doses at 10 mg/kg per day for four courses or five successive intraperitoneal doses at 0.5 mg/kg per day. Next, we examined the effects of PF1022A on larval A. cantonensis migrating into the central nervous system (CNS) of rats. Following five successive oral doses at 5 or 10 mg/kg per day and five successive intraperitoneal doses at 0.5 mg/kg per day, lesser killing effects were observed on male as well as female worms. On the basis of these results it is apparent that PF1022A will become a promising anthelmintic available as treatment for tissue-dwelling as well as intestinal nematodes.

Fatal human pulmonary infection caused by an Angiostrongylus-like nematode

An immunocompetent man developed malaise, fever, progressive weight loss, eosinophilia, and transient pulmonary infiltrates that responded to steroid treatment but recurred after its discontinuation. Examinations of feces, bronchoalveolar lavage fluid, and pulmonary tissue obtained during a 50-day period of hospitalization yielded negative results. When a new bronchoalveolar lavage sample and a new pulmonary biopsy specimen showed nematode larvae and adult worms, treatment with thiabendazole was started. However, therapy with this agent and then with mebendazole had no impact on the patient's downhill course, which ended in respiratory distress and death. Autopsy documented an overwhelming pulmonary infection with a metastrongylid nematode resembling a species of Angiostrongylus. Histologic study revealed features of necrotizing angiitis closely mimicking those of Wegener's granulomatosis. To our knowledge, this is the first reported instance of patent metastrongylid parasitism of the human pulmonary arteries with necrotizing angiitis caused by a reaction to the parasite and/or its metabolic products.

Factors affecting Dirofilaria immitis prevalence in red foxes in northeastern Spain

We determined the prevalence of Dirofilaria immitis (Nematoda, Filariidae) among 433 red foxes (Vulpes vulpes) in northeastern Spain, between 1990 and 1992. Forty-six (11%) of 433 foxes were infected; the intensity ranged from 1 to 36 (mean +/- SE; 4.39 +/- 0.92) nematodes per host. The prevalence of D. immitis was higher in foxes inhabiting riparian zones of the study area. This population has a very high juvenile/adult ratio. Heartworm prevalences did not differ among host sex, weight, or fat condition categories.

Effects of nitroglycerin on hemodynamics in dogs with experimentally inserted heartworms

Hemodynamic effects of nitroglycerin were investigated in dogs with right ventricular failure including engorgement of the pulmonary artery and ascites induced by insertion of adult live heartworms into the pulmonary artery. The mean pulmonary arterial pressure (21.5 +/- 6.6 mmHg) in heartworm-inserted dogs 4 or 5 weeks after heartworm insertion were higher than that of control (4.2-7.1 mmHg). Nitroglycerin administered intravenously at doses of 3 or 10 micrograms/kg decreased pulmonary arterial pressure in these heartworm inserted dogs. This drug also decreased pulmonary vascular resistance and total systemic resistance with no effect on cardiac index and heart rate.

Pulmonary arterial changes in feline dirofilariasis

Eleven cats with spontaneous dirofilariasis were necropsied; ten were domestic shorthairs and one was a Persian. The cats ranged in age from 1 to 10 years, and 6/11 cats were male. One to three heartworms were present in the right ventricle and pulmonary arteries of each of the 11 cats. Patchy areas of rugose thickening of the intima of the pulmonary trunk and marked villous endarteritis of lobar and medium-sized pulmonary arteries were observed. Affected larger vessels were partially occluded by large villous intimal proliferations that were lined by hyperplastic endothelial cells supported by connective tissue stroma. Moderate to marked infiltration of eosinophils and mononuclear inflammatory cells was consistently observed in the intima of affected larger pulmonary arteries. Thrombosis of pulmonary arteries was seen in five cats. Medial hypertrophy, mild intimal proliferative changes, and focal infiltrations of leukocytes were seen in small pulmonary arteries. Lesions indicative of right-sided heart failure consisting of right ventricular dilation and chronic passive congestion of the liver were observed in four cats.

Relationship between pulmonary arterial pressure and pulmonary thromboembolism associated with dead worms in canine heartworm disease

To examine effects of thromboemboli due to dead worms on pulmonary arterial pressure (PAP), 20 to 50 dead heartworms were inserted into the pulmonary arteries of 4 heartworm uninfected dogs (uninfected group) and 11 dogs infected with heartworms (infected group). In the uninfected group, the mean PAP rose 1 week after worm insertion (10.9 to 166. mmHg), but it recovered by the 4th week. Clinical signs, hemodynamics and blood gas findings also deteriorated at the 1st week, but recovered at the 4th week. Angiographic and pathological findings indicated that blood flow recovered through the spaces between thromboemboli and vessel walls at the 4th week. The infected dogs were divided into three groups. In the infected-I group (5 dogs), the intimal lesions of the pulmonary arteries were slight, and clinical and laboratory findings showed changes similar to those of the uninfected group. In the infected-II group (4 dogs), the pulmonary arterial lesions were severe and the mean PAP was higher (25.7 mmHg) than in the uninfected group before worm insertion. An increase in PAP (34.1 mmHg) and worsening of clinical and laboratory findings were noticed till the 4th week. Thromboemboli adhered extensively to the vessel walls. Two dogs in the infected-III group died of severe dyspnea on the 9th and 10th day, and the mean PAP rose remarkably at the 1st week (from 19.4 to 28.2 mmHg). Severe pulmonary parenchymal lesions with edema or perforation were observed. From the above results, it was clarified that effects of dead worms on PAP and clinical signs depended on the severity of pulmonary arterial lesions before worm insertion.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiopulmonary function in dogs with serious chronic heartworm disease

Cardiopulmonary function was examined in 18 dogs with serious chronic heartworm disease showing ascites, subcutaneous edema, prostration, weakness, jaundice and so on. After surgical heartworm removal from the pulmonary arteries, 10 dogs recovered (surviving group), and 8 dogs died or were euthanatized because of poor prognosis (nonsurviving group). The number of live heartworms residing in the pulmonary arteries of the surviving group tended to be larger than that in the nonsurviving group. At necropsy, severe pulmonary arterial lesions such as thromboembolism including dead heartworms, proliferative and villous lesions and intimal hyperplasia were noticed in all dogs examined, and tended to be severer in the nonsurviving group. Heartworm-coiling around the tricuspid valve chord was found in 1 dog of the surviving group and 4 dogs of the nonsurviving group. Before heartworm removal, there was no significant difference in the mean pulmonary arterial pressure (MPAP) between the surviving and nonsurviving group. Right atrial pressure (v-wave) was higher, and the cardiac index (CI) was lower in the nonsurviving group. Arterial oxygen tension was lower in the surviving group than in the heartworm-free group, and it was lower in the nonsurviving group than in the surviving group. Carbon dioxide tension was lower in the surviving group than in the heartworm-free group. Bicarbonate concentration (HCO3-) was lower both in the surviving and nonsurviving groups than in the heartworm-free group. One week after heartworm removal, MPAP decreased (P less than 0.05), and CI and HCO3- tended to increase in the surviving group.

Worm burden and leukocyte response in Angiostrongylus malaysiensis-infected rats: the influence of testosterone

Gonadectomized male albino rats aged 7 weeks were given 1.5 mg/kg testosterone propionate daily and inoculated with 50 third-stage larvae of Angiostrongylus malaysiensis. The treatment significantly increased the number of larvae and adult worms recovered from the brain and pulmonary arteries, respectively, and the rats exhibited smaller thymus glands. The total numbers of leukocytes, monocytes, neutrophils, and especially eosinophils increased significantly post-infection, but the counts were higher in the untreated infected controls. Presumably, immunosuppressive effects of testosterone may at least partly be responsible for the higher loads of A. malaysiensis worms found in male rats as compared with females in the field.

[Human pulmonary dirofilariasis: parasitological aspects of the 2d case reported in Italy]

The parasitological aspects of a case of pulmonary human dirofilariasis, recently reported by Fabbretti and collaborators (1990) in a 58 year-old man from Ferrara province, are described. This is the second case of pulmonary human dirofilariasis recorded in Italy. The nematode was rolled up inside a small pulmonary artery and was associated with a nodular infarcted lesion, discovered during an X-ray check as a "coin lesion". A pulmonary lobectomy was performed on the patient with a presumptive diagnosis of a malignant neoplastic nodule. The exact diagnosis was only made with the histological examination. In spite of the bad preservation of the nematode, it was possible to diagnose it as an immature female of Dirofilaria probably belonging to the species repens.

Pathology of naturally acquired Angiostrongylus vasorum infection in the red fox (Vulpes vulpes)

199 out of 509 foxes culled in a rabies control scheme, were shown to be infected with the metastrongylid parasite Angiostrongylus vasorum. Pathological lesions associated with angiostrongylosis in the fox are described and compared to reported lesions of A. vasorum infection in the dog. The lesions observed in the foxes seemed to be less severe and mainly confined to the ventral parts of the lung lobes which showed granulomatous pneumonia. Right ventricular hypertrophy of the heart was present in all infected foxes. It is believed that the fox population represents an important reservoir of A. vasorum.

Contribution of live heartworms harboring in pulmonary arteries to pulmonary hypertension in dogs with dirofilariasis

To investigate whether adult heartworms harboring in the pulmonary arteries contribute to pulmonary hypertension, we determined the cardio-pulmonary values immediately before and after removal of heartworms from the pulmonary arteries and before and after insertion of live worms in their place. In 10 heartworm-infected dogs, 8 to 46 worms were removed. The mean pulmonary arterial pressure fell significantly from 24.5 +/- 7.9 mmHg to 16.3 +/- 4.9 mmHg (p less than 0.01) immediately after removal. The right cardiac output decreased in 7 of the 10 cases. The total pulmonary resistance and right ventricular stroke work index also decreased. At 24 hours after removal, live heartworms were put back into the pulmonary arteries of their host dog. The mean pulmonary arterial pressure elevated significantly (p less than 0.01) immediately after insertion. The right cardiac output further decreased in 7 of the 10 dogs, and the total pulmonary resistance and right ventricular stroke work index increased. Separate from this, 12 to 42 heartworms were transplanted into the pulmonary arteries of 5 heartworm-free dogs. Immediately after transplantation, the pulmonary arterial pressure did not show any significant change. However, the stroke volume decreased, and the total pulmonary resistance increased. These facts suggest a contribution of live heartworms to the pulmonary hypertension, although there is a complicated interaction among the presence of heartworms, the pulmonary lesions and the pulmonary hypertension.

Morphologic changes in the lungs of cats experimentally infected with Dirofilaria immitis. Response to aspirin

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)

Migratory effects on the body surface of Angiostrongylus cantonensis from subarachnoid space to pulmonary artery in rats

Juvenile worms of Angiostrongylus cantonensis recovered from subarachnoid spaces and pulmonary arteries of rats, respectively, at 28 days post-infection have been compared with respect to their surface composition, antigenicity of surface proteins and morphological appearance. Quantitative and qualitative differences were shown between surface proteins of these two stages of worms. One major and 6 minor proteins appeared on brain stage worm's surface as assessed by surface-labelling and SDS-PAGE techniques. The same, but more predominant banding pattern, with one additional major protein of Mr 80,000 kDa presented on the lung stage worm's surface. Surface components from both stages were antigenic in permissive rat hosts but refractory in nonpermissive human hosts. The surface antigens are common to both stages within the rat. Observed by scanning electron microscopy, the surface appearance of brain stage worms is thickened, rough and irregular. Besides, particle clusters adhere randomly, without cluster adherence but transverse and longitudinal clefts were shown on the surface, before the outer layer was shed. The possible mechanisms of evasion from the host's immune attack with the surface-shedding phenomenon remain to be elucidated.

Heartworm migration toward right atrium following artificial pulmonary arterial embolism or injection of heartworm body fluid

Heartworms harboring in the pulmonary arteries migrated toward the right atrium following insertion of dead heartworms or heartworm-like silicone tubes, or intravenous injection of body fluid extract of a female heartworm. The migration occurred within 3 hr (early group) or 1 to 7 days (late group) after insertion of dead worms, 1 to 11 days after insertion of silicone tubes, and immediately after infusion of heartworm-body fluid. The cardiac output decreased to an unmeasurably low level, and the pulmonary arterial pressure was also reduced in the early group. Although the output decreased, the pulmonary arterial pressure and the total pulmonary resistance increased gradually in the late group. In dogs with heartworm migration, in which silicone tubes had been inserted, the changes in cardiopulmonary values were the same as those in dogs of the late group. In dogs to which the body fluid had been administered intravenously, the changes in cardiopulmonary values were well accord with those in the early group. The systemic blood pressure also fell immediately after the administration with the shock-like state. These results suggest that the death of a part of the heartworms may be closely associated with the migration of heartworms toward the right atrium through the pulmonary arterial embolism and/or shock-like reaction by heartworm body fluid.