Rhabditiform Larvae Research Articles

Strongyloides ratti and S. stercoralis: effects of cambendazole, thiabendazole and mebendazole in vitro.

The effects of in vitro incubation of three henzimidazole anthelmintics, thiabendazole, mebendazole and cambendazole on Strongyloides were compared. No drug affected hatching of S. ratti eggs or the viability of infective larvae or parasitic adult worms, but all three inhibited moulting of S. ratti larvae. In addition, cambendazole, but not thiabendazole or mebendazole, impaired the viability of S. ratti first- and second-stage larvae. The three drugs had no effect on isolated S. stercorais free-living adult worms, but they all prevented development of S. stercoralis rhabditiform larvae. Thiabendazole and mebendazole had no effect on the infectivity of either S. ratti or S. stercoralis infective larvae, but infection with these worms was abrogated by prior incubation with cambendazole. These results indicate that cambendazole acts in a different manner to the other two drugs. Since it is active against larvae migrating through the tissues, it is potentially of much greater value than thiabendazole or mebendazole in the therapy of strongyloidiasis.

Cultivation of Free-Living Stages of Trichostrongylus colubriformis in Media without Bacteria, Animal Tissue Extract, or Serum

Trichostrongylus colubriformis was cultured from hatched first-stage to third-stage larvae in bacteria-free media in the absence of animal tissue extract or serum. This was achieved for the first time with a nematode, parasitic in vertebrates, whose rhabditiform larvae are food-dependent. The best media contained enzymatic hydrolysed casein (amino nitrogen:total nitrogen ratio 0.39), yeast extract, phosphatidylcholine from soybean, and a number of chemically defined ingredients, which include a salt solution, a sterol, and an iron porphyrin. The yield of third-stage larvae obtained was up to 17% of all the living larval stages present after incubation. When casein hydrolysate with AN:TN ratio of 0.39 was replaced by casein hydrolysate with AN:TN ratio of 0.53, little or no development to third-stage larvae occurred. Development to infective larvae was shown to be possible in media with soy peptone instead of casein hydrolysate, although to a very limited extent. It is proposed that the free-living stages of the parasite require peptides, whose molecular weights all lie within a narrow range.

Strongyloides stercoralis: Hyperinfection in immunosuppressed dogs

Hyperinfective strongyloidiasis involving the threadworm, Strongyloides stercoralis, is well known in humans and primates. Although this nematode also frequently parasitizes dogs, canine hyperinfective strongyloidiasis has not been reported. To determine whether a fulminant pattern of nematode development can occur in dogs, and to test the S. stercoralis/dog system for suitability as a model for human hyperinfective and disseminated strongyloidiasis, five canine infections with a dog-derived strain of S. stercoralis were monitored by the quantitative recovery of larvae from feces. Even 3-month-old pups controlled their initial infections successfully, the number of larvae excreted declining to near zero in 90 days. Immunosuppressive treatment with prednisolone, prednisolone and azathiaprine, or niridazole resulted in a rapid return to former or greater intensities of infection, as judged by larval output. Only first stage (rhabditiform) larvae were passed in the feces, although third stage (filariform) larvae occurred in the intestinal contents of dogs when they were examined at necropsy. In 3 of the 5 dogs, the adult worm recovery exceeded the inoculated dose greatly and, in one of these, adults and rhabditiform larvae were found in distant, extraintestinal sites. In the remaining 2 of the 5 dogs, the adult worm population was less than the inoculated dose, but, in both, the infection was terminated by the host's death before hyperinfection could have developed. The observations demonstrate that autoinfection occurs in dogs infected with S. stercoralis and that, if it is allowed to continue for a sufficiently long time in immunosuppressed hosts, massive hyperinfection, and even disseminated infection, may occur. This spectrum of increasingly invasive parasitism closely resembles strongyloidiasis in humans. Therefore, the S. stercoralis/dog system has excellent potential as a model for human hyperinfective and disseminated strongyloidiasis.

糞線虫による膵炎の一症例

Symptoms of strongyloidiasis are mostly related to the digestive tract; abdominal pain (45%), diarrhea (30%) and/or abdominal fullness. However, reports of pancreatitis caused by Strongyloidiasis are rare. A 42-year-old male complaining of severe vomiting, dehydration and diarrhea was hospitalized on June 14,1983. He had lived in Okinawa prefecture until the age of 20 years. Laboratory data revealed leucocytosis, anemia and increased serum amylase. It was suspected that he was suffering from dehydration due to acute pancreatitis or acute colitis. Numerous Rhabditiform larvae of Strongyloides Stercoralis were present in the duodenal fluid and stool. Abdominal echo and computerized tomography showed pancreas swelling. The disappearance of the Kerckring's folds were studied by the double contrast picture of the duodenum. Endoscopic retrograde cholangiopancreatography revealed stricture 2 cm from the entrance of pancreatic duct and also showed duct dilation resulting in a maximum dilation diameter of 9 mm. The common bile duct showed irregularity of wall and dilataion of diameter (15 mm). Pyrvinium pamoate was administered 5 times while duodenal intubation was repeated. When Rhabditiform larvae of Strongyloides Stercoralis in the duodenal fluid disappeared the level of serum amylase decreased to normal value. However, Rhabditiform larvae in the stool had not diminished completely. A Few days later, Rhabditiform larvae was still detected in the duodenal fluid. Therefore, he was treated with Thiabendazole,2500 mg daily for two days per os and complete deworming was achieved.

Persistent and disseminated infections with Strongyloides Stercoralis in immunosuppressed dogs

The effects of immunosuppression on the course of infection in dogs infected with a human strain of S. stercoralis were investigated. Four dogs were infected then 4 weeks later, three animals were begun on prednisolone orally in a dose of 150 mg daily for 6 days each week. Rhabditiform larvae continued to be excreted in the stools. After 5 weeks of immunosuppression, one dog was autopsied; plentiful parasites were found in the upper small bowel but worms were not seen in other tissues. Similar findings were made in a second dog killed after 9 weeks of immunosuppression. In the third dog, the dose of prednisolone was increased to 225 mg daily 15 weeks after infection then azathioprine 100 mg daily was added 6 weeks later. This animal was killed 24 weeks after infection and evidence for multiplication of S. stercoralis was obtained. Large numbers of adult worms, eggs and rhabditiform larvae were recovered from duodenal fluid. Infective larvae were seen in homogenised lung, rhabditiform larvae were noted in homogenised spleen and both rhabditiform larvae and adult worms were found in homogenised kidney. Worms in all stages of development were seen in the urine. Histological examination revealed large numbers of adult worms and enormous numbers of eggs and larvae in the duodenal mucosa. Worms were seen throughout the length of the small intestine as well as in the colonic mucosa. The lungs displayed focal haemorrhages and larvae were seen in the alveolar spaces, bronchioles and bronchi. Evidence of immunosuppression was provided by the gross atrophy of the thymus and the fall in anti- Strongyloides antibody titres. In contrast to these dogs, larvae disappeared from the non-immunosuppressed dog by 13 weeks after infection. This animal was then immunosuppressed for 8 weeks but parasites could not be found in either the stools or at autopsy. Two further dogs were immunosuppressed before infection but they died soon thereafter. It is concluded that immunosuppression permits the persistence of infection with S. stercoralis and if continued for long enough and in sufficient degree, that disseminated infection supervenes. This model may provide a means for assessing the efficacy of various therapeutic regimens in overwhelming strongyloidiasis and for investigations of the host-parasite relationship in this infection.

十二指腸液中より糞線虫Rhabditis型仔虫を検出した胆嚢炎の一症例

A 37 year old male complaining of right hypochondralgia was hospitalized on August 17,1974. His previous doctor had suspected the presence of gallstones. He had lived in Kochi prefecture until he was 15 years of age. He then lived in Rio de Janeiro from 1952 to 1965. During this time he often walked barefoot. He has lived in Osaka since 1965. When examined on admission there was oppression and percussion tenderness in his r-hypochondral region. No other abnormalities were found.Lab. data: WBC 7500 (Eosinophils: 12%)Hb 16.7 g/dlliver and renal functions: normalChest-X-P: n. p.Upper GI-series: n. p.Cholecystography: stone (-), contractivity: slightly hypokineticExamination of the duodenal fluid revealed Rhabditiform larvae only in his A-bile and leukocytosis in his B-bile. However, examinations of his stool samples by the direct smear method were always negative. The diagnosis was completed when Filaria-form larvae, a very distinctive form of strongyloides stercoralis, was found by the “test tube filter paper cultivation” method. The patient was treated with Pyrvinium pamoate (total dose: 3300 mg) for 5 days. During the treatment he complained of nausea and vomiting, but no abnormalities were found in the laboratory data. After this treatment, eosinophilia gradually decreased and the test tube filter paper cultivation resulted negative for 28 days. Although the patient seemed to be cured by this treatment, eosinophilia recurred 6 months thereafter and his stool culture again revealed Filariaform larvae.Strongyloidiasis is prevalent mainly in the southernmost parts of Japan, especially the Amami Islands, and in other tropical and subtropical areas of the world. According to “Igaku-chuo-Zasshi”, a comprehensive Japanese medical publication, only 21 cases of strongyloidiasis were reported in Honshu Island between 1965 and 1974. Sixteen out of these patients were from the southernmost parts of Japan or had spent considerable time in tropical or subtropical areas.The cause of infection, and the relationship between the strongyloidiasis and chole cystitis of this patient are discussed.

Kinetics of primary and secondary infections with Strongyloides ratti in mice

Dawkins H. J. S. and Grove D. I. 1981 Kinetics of primary and secondary infections with Strongyloides ratti in mice. International journal for Parasitology 11: 89–96. The kinetics of infection with S. ratti were quantitated in normal and previously exposed C57B1 /6 mice. In primary infections, larvae penetrated the skin rapidly and were seen in peak numbers 12 h after infection. By 24 h after infection, larval numbers had declined appreciably and there was a slow decrease in numbers thereafter. Larvae were first observed in the lungs at 24 h and maximal recovery occurred at 48 h. It is thought that larval migration through the lungs is rapid. Worms were first seen in the intestines two days after infection. Maximum numbers were seen on the fifth day and worm expulsion was complete by day 10. Two moults took place in the small intestine during days 3 and 4 after infection. Rhabditiform larvae were first noted on the fourth day after infection. Mice exposed to S. ratti four weeks previously had significantly less larvae in the skin 4 and 12 h after infection but by 24 h there was no difference when compared with mice with primary infections. Peak recovery of larvae from the lungs occurred 24 h after infection; significantly less larvae were recovered on days 2 and 3 when compared with normal mice. There was a marked reduction in the adult worm burden in the gut; the number of worms recovered was less than one fifth of that seen in primary infections. Those worms which did mature were less fecund and were expelled from the intestines within 7 days of infection. It is suggested that in previously exposed animals, the migration of larvae from the skin is hastened, many of these larvae are destroyed in the lungs and that expulsion of worms which do mature in the intestines is accelerated.

Fatal strongyloidiasis in gibbons (Hylobates lar).

A 6-year retrospective study of necropsy material from a colony of 200 gibbons showed strongyloidiasis to be the most frequent cause of death (24 cases). Clinical signs included diarrhea, constipation, weight loss, paralytic ileus and dyspnea. Lesions were most frequent in the gastrointestinal tract and lungs. In the gut there were erosive and ulcerative enteritis associated with adult female parasites and rhabditiform larvae and acute and granulomatous enterocolitis associated with invading filariform larvae. There was severe multifocal or diffuse hemorrhage associated with migrating larvae in the lungs of 23 gibbons. Filariform larvae and the lesions they caused also occurred in various tissues; this was commensurate with the wide distribution of these larvae when hyperinfection occurred.

Strongyloides fülleborni infections in man in Zambia.

Rhabditiform larvae, and in two cases eggs, of Strongyloides spp. identified in the stools of Zambian patients were cultured to the free-living adult stage. Free-living adults of S. fülleborni, a parasite common in primates in Africa and Asia, were present in cultures from 13 (9.9%) of 131 cases of strongyloidiasis. In three of these cases, both S. fülleborni and S. stercoralis free-living adults were found.

Laboratory diagnosis of autoinfection in strongyloidiasis.

Among 10,072 examinations of concentrated stools, Strongyloides stercoralis rhabditiform larvae were found in 93, and filariform larvae in four. In two of the four cases harboring filariform larvae, subsequent stools revealed only rhabditiform larvae, but filariform larvae continued to be found in the stools and sputum of the other two cases. It was concluded that only two of the cases were true autoinfections, and the other two apparent cases resulted from prolonged storage of unrefrigerated stools in the hospital ward. The importance of distinguishing true autoinfections from a free-living Strongyloides life cycle in stools is stressed.

A case of human strongyloidosis apparently contracted from asymptomatic colony dogs.

A 63-year-old, white, animal caretaker suffered intermittent abdominal pain and diarrhea of 3 weeks duration. Hematological findings included leukocytosis (18,600) with eosinophilia (73%). Fecal examination revealed Stongyloides rhabditiform larvae which on culture yielded a preponderance of filariform larvae and a few free-living adults. Thiabendazole therapy resulted in rapid recovery. Epidemiological investigation yielded no history of previous Strongyloides infection or exposure; his wife and pet dog were not infected, but about one-third of the dogs in the colony under his care were found to be discharging Stongyloides rhaditiform larvae in their feces. Strongyloides infection was successfully trasmitted to specific pathogen-free pups using filariform larvae derived both from the human case and from the dog colony. Specimens recovered from one pup infected with filariform larvae of human origin were identified as Strongyloides stercoralis.

Larva currens (migrans) caused by Strongyloides stercoralis.

A 62-year-old missionary sister suffered from abdominal pains and diarrhoea since she left the Congo in 1939. For the last 20 years she also had recurrent attacks of itching during which she showed rapidly migrating linear urticarial weals on the skin of the abdomen and thighs. After she received prednisone, her skin lesions became generalized and her stools, which had been negative for worms, showed rhabditiform larvae of <i>Strongyloides stercoralis</i>. Eosinophilia was an irregular finding in this patient. She improved rapidly after two courses of thiabendazole.

STUDIES ON STRONGYLOIDES OF PRIMATES: II. FACTORS DETERMINING THE "DIRECT" AND THE "INDIRECT" MODE OF LIFE

Under optimum conditions Strongyloides fülleborni has an indirect life cycle but under adverse conditions, only infective larvae and males are developed. Adverse factors such as pH and consistency of media, absence of food, and unsuitable temperatures appear to act directly on the first-stage rhabditiform larvae developed from the eggs of parasitic females. The potential female larva alone becomes an infective larva, the potential male being unaffected. There is a single free-living generation and all eggs laid by free-living females develop directly into infective larvae. The infective larvae developed directly or indirectly can develop only into parthenogenetic females.

Preparasitic Moults in Nippostrongylus Muris, with Remarks on the Structure of the Cuticula of Trichostrongyles

Rhabditiform first-stage larvae of Nippostrongylus muris are about 270–550μ long. The development of these larvae culminates in a moult, which occurred 36–48 hours after cultures were prepared. The first moult is preceded by an unusually early separation of the first cuticle, which is fine and unstriated, from the body tissue in the tail region and, later, by the formation of an underlying new cuticle, which is thicker and prominently striated.Early second-stage rhabditiform larvae differ in certain morphological respects from first-stage larvae. Second-stage larvae are about 470–750μ long.A second preparasitic ecdysis occurs and the infective larva is a true third-stage larva. This moult was the only one previously known to occur during the preparasitic development of N. muris.The post-cervical cuticular inflation in N. muris is regarded, on the basis of a comparative study of the cuticle of this species and of Haemonchus contortus and other trichostrongyles, as resulting from the separation of the second and third layers of the cuticle. Yokogawa's view that Nippostrongylus muris has two cuticulae is rejected. N. muris has a single cuticula, apparently made up of four layers.N. muris undergoes four complete moults and the development of this species does not differ in any essential respect from that reported for other strongyles.

Experimental Propagation of Strongyloides in Culture.

The nematode parasite Strongyloides simiae of New World monkeys has as a part of its life cycle a free-living phase outside the body of the host. The eggs laid by the parasitic females are passed in the feces, rhabditiform larvae hatched from them feed on bacteria and debris, and under suitable conditions, metamorphose into free-living, sexually mature forms. These adults mate and produce eggs and larvae supposedly identical with those of the first generation. Such second generation individuals have been considered capable only of developing into filariform larvae. Leuckart's1 views on the fate of the second generation larvae probably have influenced the general belief that only one sexual generation of the free-living phase could develop. The only statement regarding the probable continued propagation of the free-living phase of this organism was that by Faust,2 who predicted indefinite free-living development.By planting a known number of S. simiae eggs from the stool of Cebus capucinus imitator which h...