Penetration sites and migratory routes of Angiostrongylus costaricensis in the experimental intermediate host (Sarasinula marginata).

The intermediate hosts of Angiostrongylus costaricensis are terrestrian molluscs, mostly of the family Veronicellidae. The present work aimed at clarifying more accurately the sites of penetration and the migratory routes of A. costaricensis in the tissue slugs and at verifying the pattern of the perilarval reaction at different times of infection. Slugs were individually infected with 5,000 L1, and killed from 30 min to 30 days after infection. From 30 min up to 2 hr after infection, L1 were found within the lumen of different segments of the digestive tube having their number diminished in more advanced times after exposition until complete disappearance. After 30 min of exposition, percutaneous infection occurred, simultaneously to oral infection. Perilarval reaction was observed from 2 hr of infection around larvae in fibromuscular layer, appearing later (after 6 hr) around larvae located in the viscera. A pre-granulomatous reaction was characterized by gradative concentration of amebocytes around larvae, evolving two well-organized granulomas. In this work we confirmed the simultaneous occurrence of oral and percutaneous infections. Perilarval reaction, when very well developed, defined typical granulomatous structure, including epithelioid cell transformation. The infection also caused a systemic mobilization of amebocytes and provoked amebocyte-endothelium interactions.     

Angiostrongylus costaricensis: complete redescription of the migratory pathways based on experimental Sigmodon hispidus infection

Angiostrongylus costaricensis lives in the cecal and mesenteric arteries of its vertebrate hosts, and causes an inflammatory disease in humans. To investigate unknown aspects of the abdominal angiostrogyliasis pathogenesis, infected Sigmodon hispidus were sequentially studied in different times of infection. The study revealed that L3 goes alternatively through two migratory courses during its development into an adult worm: lymphatic/venous-arterial and venous portal pathways. The former is considered the principal one, because it is used by most of the larvae. Like other metastrongylides, A. costaricensis passes over the pulmonary circulation to migrate from the lymphatic system to the arterial circulation, where they circulate during some days before reaching their definitive habitat. The oviposition by mature females began on 15th day. Eggs and L1 were detected mainly in the intestine and stomach, surrounded by inflammatory reaction constituted by macrophages, monocytes, and eosinophils. They were also spread to the lungs, mesenteric lymph nodes, pancreas, spleen, and kidneys. The larvae (L1) exhibited the centripetal capacity to invade the lymphatic and venous vessels of the intestine and mesentery. Adult worms that developed in the venous intrahepatic pathway migrated downstream to reach the mesenteric veins and laid eggs that embolized in the portal hepatic vessels.     

Low susceptibility of Achatina fulica from Brazil to infection with AngioIylus costaricensis and A. cantonensis

Introduction of Achatina fulica in Brazil has led to serious concerns about its role as vector for metaIylid worms: AngioIylus costaricensis and A. cantonensis. Experimental infection with both parasites was performed to evaluate the potential risk for their transmission by the giant African snail. Groups of 5 animals, both wild and bred at captivity were exposed at different inocula: 1, 5, and 10 x 10(3) L1 of A. costaricensis and A. cantonensis. In all groups, few snails got infected and parasitic burden was low. Two different ways of infection were tested: ingestion produced higher numbers of L3 than the inoculation through an artificial hole in the shell. We also report the parasitological examination of 6 batches of wild A. fulica from Florianópolis, state of Santa Catarina, Brazil: only 1 out of 244 animals were infected with metaIylid larvae. Taken together these data indicate that the giant African snail occurring in Southern Brazil is not a permissive host for both AngioIylus species and does not represent a significant risk for transmission of these parasites.     

Phyllocaulis variegatus--an intermediate host of Angiostrongylus costaricensis in south Brazil

Molluscs collected in five localities in the State of Rio Grande do Sul (Brazil) were digested and examined. The infected slugs were identified as Phyllocaulis variegatus and the larvae found were inoculated per os into mice. After 50 days, worms with the caracteristics of Angiostrongylus costaricensis were recovered from the mesenteric arterial system. The results establish the role of P. variegatus as intermediate host of A. costaricensis in south Brazil, where many cases of abdominal angiostrongyliasis have been diagnosed.     

Angiostrongylus costaricensis and experimental infection of Sarasinula marginata II: elimination routes

Angiostrongylus costaricensis intermediate hosts are terrestrial mollusks mostly belonging to the Veronicellidae family. In the present investigation we focused on the mechanisms of larval expulsion from Sarasinula marginata infected with A. costaricensis. Twenty-five mollusks were individually infected with 5000 L1 and sacrificed at 30 min and 1, 2, 4, 6, and 8 h post-infection and at days 1, 2, 4, 5, 6, 8, 10, 11, 12, 14, 15, 16, 20, 21, 22, 25, 26, 28, and 30 post-infection; the mollusks were then fixed and stained. Diverse organs involved throughout the course of the migratory routes of larvae from oral penetration on were specified and the mechanisms of larval access to the fibromuscular layer through the kidney, rectum, and vascular system were defined. The elimination of L3, derived from oral and/or cutaneous infections, appears to depend on granulomas located close to the excretory ducts of mucous cells.     

Pterygodermatites nycticebi (Nematoda: Rictulariidae): accidental detection of encapsulated third-stage larvae in the tissue of a white-fronted marmoset

Twin, white-fronted marmosets (Callithrix geoffroyi) born and raised in a zoo in Japan died at 7 mo of age. Several encapsulated nematode larvae were detected in the intestinal wall, as well as a few in the mesenteric lymph nodes of 1 of the twins. In the other marmoset, no encapsulated nematode larva was detected in the organs, but many adult Pterygodermatites nycticebi were found in the intestinal lumen. In the past 5 yr, 5 primates kept in the same zoo, i.e., 1 squirrel monkey (Saimiri sciureus), 2 Pygmy marmosets (Cebuella pygmaea), 1 Senegal galago (Galago senegalensis), and 1 cotton-top tamarin (Saguinus oedipus), died from heavy infestation with the same nematode. A few migrating larvae of the rictulariid were also identified histologically in the intestinal wall and liver of the cotton-top tamarin. Although no other primate currently held in the same zoo was infected with the rictulariid, German cockroaches (Blattella germanica) collected with traps near marmoset cages had encapsulated P. nycticebi larvae, indicating latent perpetuation of the life cycle of this rictulariid species in the zoo premises. Our results indicated that encapsulation or migration of third-stage larvae of P. nycticebi might occur accidentally in the organs of callithrichid primates.     

Histopathology and ultrastructure of Platichthys flesus naturally infected with Anisakis simplex s.l. larvae (Nematoda: Anisakidae)

The histopathology, ultrastructure, and immunohistochemistry of the alimentary canal of flounder Platichthys flesus (L.), naturally infected with the nematode Anisakis simplex s.l. (Rudolphi 1809) from the River Forth (Scotland), were investigated and described. Eight of the 16 flounders were infected with A. simplex s.l. larvae (L3); parasites were encapsulated by serosa on the external surface of the host's digestive tract (intensity of infection 1-8 parasites per host), although nematode larvae were found encysted under the peritoneal visceral serosa of the host spleen and liver and, occasionally, in the liver parenchyma (intensity of infection 3-10 parasites per host). In all sites, different structural elements were recognized within the capsule surrounding larvae. Among the epithelial cells of the intestine of 5 flounders with larvae encysted on external surface of the gut, the presence of several rodlet cells (RCs) was observed. Furthermore, often the occurrence of macrophage aggregates (MAs) was noticed in infected liver and spleen, mainly around the parasite larvae. Eight neuropeptide antisera were tested with immunohistochemistry methods on gut sections of 4 P. flesus infected with extraintestinal nematodes. Sections from the gut of 5 uninfected flounder were used for comparative purposes. In the tunica mucosa of parasitized P. flesus, several endocrine epithelial cells were immunoreactive to anti-CCK-39 (cholecystokinin 39) and -NPY (neuropeptide Y) sera; furthermore, in the myenteric plexus, a high number of neurons were immunoreactive to antibombesin, -galanin, and several to -NPY and -PHI (peptide histidine isoleucine) sera.     

Diagnosis of Strongyloides stercoralis in a peritoneal effusion from an HIV-seropositive man. A case report

BACKGROUND: Strongyloides stercoralis, a nematode parasite in humans with free-living and autoinfective cycles, is often an asymptomatic infection of the upper small intestine. If the host becomes immunocompromised, autoinfection may increase the intestinal worm burden and lead to disseminated strongyloidiasis. The parthenogenetic adult female larvae can remain embedded in the mucosa of the small intestine for years, producing eggs that develop into either rhabditiform, noninfective larvae or filariform, infective larvae. Manifestations of dissemination occur when the filariform larvae penetrate the intestinal wall and migrate into the blood. Pulmonary involvement is common, and the central nervous system may be affected. Blood eosinophilia is typical, and gram-negative sepsis from enteric bacteria may occur. Much less commonly described is invasion of the peritoneal cavity with peritoneal effusion. CASE: A 49-year-old man who came to the United States from Liberia 4 years earlier presented with sudden onset of severe abdominal distention, generalized weakness and marked pedal edema. Diagnostic paracentesis showed numerous filariform larvae of S stercoralis. Stool examination confirmed the presence of both rhabditiform and filariform larvae. Subsequently the patient was found to be HIV seropositive, with a CD4 lymphocyte count of 59. CONCLUSION: Early detection of S stercoralis may alter the often-fatal course of infection. The present case is the second reported one in the English-language literature of the diagnosis of S stercoralis in ascitic fluid.     

Use of heterologous antigens for the immunodiagnosis of abdominal angiostrongyliasis by an enzyme-linked immunosorbent assay

Angiostrongylus costaricensis has a broad geographic distribution spanning from North to South America and the infections of vertebrates with this nematode can result in abdominal complications. Human infections are diagnosed by histological or serological methods because the isolation of larvae from feces is not feasible, as most parasites become trapped in intestinal tissues due to intense eosinophilic inflammation. Because A. costaricensis is difficult to maintain in the laboratory, an immunodiagnostic IgG enzyme-linked immunosorbent assay (ELISA) using antigens from the congeneric Angiostrongylus cantonensis species was evaluated against a panel of serum samples from patients who were histologically diagnosed with A. costaricensis infections. Sera from uninfected individuals and individuals infected with other parasites were used as controls. The sensitivity and specificity of the assay were estimated at 88.4% and 78.7%, respectively. Because the use of purified or cloned antigens has not been established as a reliable diagnostic tool, the use of heterologous antigens may provide a viable alternative for the development of an ELISA-based immunodetection system for the diagnosis of abdominal angiostrongyliasis.     

Enhancement of host resistance against Listeria infection by Lactobacillus casei: efficacy of cell wall preparation of Lactobacillus casei

Cell wall, cytoplasm, polysaccharide, and peptidoglycan fractions prepared from Lactobacillus casei, L. plantarum, and L. acidophilus were examined for their efficacies to enhance resistance of host mice against Listeria monocytogenes infection. Intraperitoneal injections of those cellular fractions of L. casei led to elicitation of inflammatory cells in the peritoneal cavity and the efficacy was highest in the case of peptidoglycan. Macrophage ratio in the resultant peritoneal exudate cells was also highest in mice given peptidoglycan. Macrophages induced with cell wall fraction of L. casei showed the most potent phorbol myristate acetate (PMA)-triggered respiratory burst (chemiluminescence and O2- production determined on the basis of nitroblue tetrazolium reduction) followed by those elicited with peptidoglycan. All the macrophages induced with cell wall of L. casei (two strains) and L. acidophilus enhanced O2- production in response to PMA but L. plantarum did not enhance O2(-)-producing ability in such a manner. The L. casei-cell wall also enhanced in vitro listericidal activity of mouse peritoneal macrophages, but such an activity was not noted in the case of L. acidophilus-cell wall. When mice were intravenously given the cellular fractions 7 or 13 days before L. monocytogenes infection, cell wall fractions of L. casei caused the most potent protective activity. A weak protective activity was also found in peptidoglycan of L. casei. Therefore, the protective action of L. casei against L. monocytogenes infection in host mice may be attributed to cell wall compounds and partially to the peptidoglycan moiety.     

Trichinella spiralis: newborn larval migration route in rats reexamined

The route by which Trichinella spiralis newborn larvae migrate from the small intestine to striated muscle was studied in inbred AO and random-bred Sprague-Dawley rats. Newborn larvae were quantitatively recovered from the thoracic duct lymph, peritoneal cavity, and hepatic portal vein blood during the course of a primary infection with 4000 muscle larvae. The total recovery of newborn larvae assessed in this manner was compared with the number of muscle larvae in control rats receiving the same infection. In both strains of rats, most of the newborn larvae were recovered from hepatic portal vein blood, fewer than 3% of newborn larvae were recovered from the thoracic duct lymph and peritoneal cavity combined. Long-term drainage of thoracic duct lymph (greater than 24 hr) significantly increased newborn larval recovery over short-term drainage (less than 24 hr). We conclude that there are several natural pathways of newborn larval migration that result in muscle larval establishment. These include direct invasion of capillaries and lymphatics in the intestine as well as migration through the intestinal serosa to the peritoneal cavity. In both AO and Sprague-Dawley rats, greater than or equal to 97% of newborn larvae migrate via the hepatic portal vein blood to the general circulation.     

The distribution of inhibited early third stage Cyathostominae larvae in the large intestine of the horse

The distribution of inhibited early third stage Cyathostominae larvae in different parts of the large intestine of the horse was studied in 20 Shetland ponies necropsied in autumn 1982, 1983 and 1984. The location of the larvae in the large intestinal wall was studied by histological examination of the intestines of the eight ponies from 1984. Inhibited larvae were located predominantly and more or less equally in the caecum and the ventral colon. Generally fewer early L3 were in the dorsal colon. In 1984 a considerable proportion (mean 17%, range 9.7-36.9%) of the inhibited larvae was found in the contents instead of in the mucosa of the large intestine, despite a housing period under helminth free conditions of 5 weeks. These larvae probably had been overlooked in 1982 and 1983. In sections cut from the intestinal wall most early L3 were found in the lamina propria. They were surrounded by a small fibrous capsule. Some were found in the lumen or epithelium of the Lieberkühn's crypts and a small proportion in the submucosa.     

Suppression of Brugia malayi (sub-periodic) larval development in Aedes aegypti (Liverpool strain) fed on blood of animals immunized with microfilariae

Preliminary studies were carried out to investigate the role of filarial specific antibodies, raised in an animal model against the filarial parasite, Brugia malayi (sub-periodic), in blocking their early development in an experimental mosquito host, Aedes aegypti (Liverpool strain). In order to generate filarial specific antibodies, Mongolian gerbils, Meriones unguiculatus, were immunized either with live microfilariae (mf) of B. malayi or their homogenate. Mf were harvested from the peritoneal cavity of Mongolian gerbils with patent infection of B. malayi and fed to A. aegypti along with the blood from immunized animals. Development of the parasite in infected mosquitoes was monitored until they reached infective stage larvae (L3). Fewer number of parasites developed to first stage (L1) and subsequently to L2 and L3 in mosquitoes fed with blood of immunized animals, when compared to those fed with blood of control animals. The results thus indicated that filarial parasite specific antibodies present in the blood of the immunized animals resulted in the reduction of number of larvae of B. malayi developing in the mosquito host.     

Immunity to Heligmosomoides polygyrus induced by subcutaneous vaccination with post-infection larvae

The objective of this study was to investigate, using the Heligmosomoides polygyrus (= Nematospiroides dubius)-mouse model, whether live post-infection trichostrongylid larvae recovered from the intestinal wall of donor animals and placed subcutaneously would serve as vaccine protecting against oral challenge by third-stage (infective) larvae (L3). Experiments were conducted to determine the effect of number and age of post-infective larvae as well as age and sex of host on vaccination. Vaccinated BALB/cByJ mice were challenged with 30 L3 and total adult worm burdens compared between vaccinated groups and sham-treated controls (greater than 90% infection rates). All mice subcutaneously vaccinated with either five or 10 larvae harbored significantly fewer challenge parasites in their intestines than did sham-treated controls (P less than 0.001). Both young and mature mice were significantly protected against challenge by the subcutaneous larval vaccine. Adult female mice had significantly (P less than 0.05) fewer parasites than adult male mice. The age of the larvae (indicated as the days between infection and harvesting of the larvae) was important in that day-4 or day-6 larvae (L4) were significantly more protective (P less than 0.001) than day-2 (L3) or day-8 larvae (L5-preadult). Reduction in worm burden for young vaccinated animals ranged from 31 to 39% (P less than 0.001) and for mature animals from 88 to 100% (P less than 0.001). Passive transfer to serum resulted in the reduction of worm burdens by 26-40% (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Trichinella spiralis: vascular recirculation and organ retention of newborn larvae in rats

The recirculation of Trichinella spiralis newborn larvae was studied in inbred AO rats. Newborn larvae collected after in vitro incubation of adult T. spiralis worms for 2 or 24 hr were injected into rats through the tail vein or hepatic portal vein. Blood samples from the femoral vein, hepatic portal vein, and abdominal aorta were collected at intervals from 1 min to 24 hr after larval injection. Newborn larvae of both ages (24 hr or 2 hr old) persisted in femoral vein blood for less than or equal to 5 hr after injection, but they could be detected in portal vein blood by 24 hr after injection. The injection of larvae into a tail vein or the portal vein did not influence the pattern of larval circulation, although there was a 1-5 min delay in newborn larval appearance time after injection into the portal vein. Transcapillary migration through tissue and back to the circulation was evident in the appearance of newborn larvae in the thoracic duct lymph up to 24 (occasionally 48) hr after tail vein injection of newborn larvae. During the course of a natural primary infection, no evidence for trapping of larvae in the mesenteric lymph node could be found despite direct larval migration through this organ. Injected newborn larvae were retained in the lungs, and small numbers could be recovered 24 hr after intravenous injection. We conclude that a proportion of newborn larvae recirculates within the vasculature for several hours; a smaller population extravasates but can reenter the circulatory system via the lymphatics. Furthermore, some newborn larvae are found in organs rich in capillaries up to 24 hr after their entry into the blood.     

Spontaneous occurrence of Angiostrongylus costaricensis in marmosets (Saguinus mystax)

Two marmosets imported from Iquitos, Peru, were found to be infected with Angiostrongylus costaricensis. Both animals had large solitary granulomas involving the wall and adjacent mesentery of the small intestine. Histopathologic examination showed the adult nematodes in the lumina of the mesenteric arteries that coursed through these granulomas. The inflammatory reaction was associated with numerous degenerating eggs and larvae. This is the first report of this parasite in nonhuman primates and extends its geographic range to Peru. In addition, in one animal, Dipetalonema sp were seen free in the abdominal cavity, and pleroceroid larvae (spargana) were in the loose connective tissue of the left axilla. This animal also had microgranulomas associated with eggs and larvae of Angiostrongylus in the kidney, liver, lung, and heart.     

Detection of the acute phase of abdominal angiostrongyliasis with a parasite-specific IgG enzyme linked immunosorbent assay

Angiostrongylus costaricensis may cause intestinal lesions of varied severity when it accidentally infects man in Central and South America. First-stage larvae have never been detected in stools. Therefore, a parasite-specific IgG ELISA was evaluated for the determination of the acute phase of infection. The specificity and the sensitivity of the immunoassay was shown to be 76.2% and 91.1%, respectively. Eight serum samples taken from patients with histopathological diagnosis, at different time points (3 to 15 months) after surgical treatment, showed a sharp and early decline in antibody reactivity. The titration of anti-A. costaricensis antibodies has proved to be a useful method for the diagnosis of acute abdominal angiostrongyliasis.     

The life cycle of Paraquimperia tenerrima: a parasite of the European eel Anguilla anguilla

Previous studies on the life history of the nematode eel specialist Paraquimperia tenerrima (Nematoda: Quimperiidae) have failed to determine whether an intermediate host is required in the life cycle. In the laboratory, eggs failed to hatch below 10 degrees C, hatching occurring only at temperatures between 11 and 30 degrees C. Survival of the free-living second stage larvae (L2) was also temperature dependent, with maximal survival between 10 and 20 degrees C. Total survival of the free-living stages (eggs and L2) is unlikely to exceed a month at normal summer water temperatures, confirming that parasite could not survive the 6 month gap between shedding of eggs in spring and infection of eels in early winter outside of a host. Eels could not be infected directly with L2, nor could a range of common freshwater invertebrate species. Third stage larvae (L3) resembling P. tenerrima were found frequently and abundantly in the swimbladder of minnows Phoxinus phoxinus from several localities throughout the year and were able to survive in this host in the laboratory for at least 6 months. Third stage larvae identical to these larvae were recovered from minnows experimentally fed L2 of P. tenerrima, and eels infected experimentally with naturally and experimentally infected minnows were found to harbour fourth stage larvae (L4) and juvenile P. tenerrima in their intestines. Finally, the whole life cycle from eggs to adult was completed in the laboratory, confirming that minnows are an obligate intermediate host for P. tenerrima.     

Alteration in the endogenous intestinal flora of Swiss Webster mice by experimental Angiostrongylus costaricensis infection

The association between worm infections and bacterial diseases has only recently been emphasized. This study examined the effect of experimental Angiostrongylus costaricensis infection on endogenous intestinal flora of Swiss Webster mice. Eight mice aging six weeks were selected for this experiment. Four were infected with A. costaricensis and the other four were used as controls. Twenty eight days after the worm infection, all mice in both groups were sacrificed and samples of the contents of the ileum and colon were obtained and cultured for aerobic and anaerobic bacteria. In the mice infected with A. costaricensis there was a significant increase in the number of bacteria of the endogenous intestinal flora, accompanied by a decrease in the number of Peptostreptococcus spp. This alteration in the intestinal flora of mice infected by the nematode may help to understand some bacterial infections described in humans.