Strongyloides Larvae Research Articles

Human T-lymphotropic virus 1 adult T-cell lymphoma with Giardia and Strongyloides parasitism.

A man originally from Togo, West Africa, developed a 2-month history of abdominal cramps, diarrhea, and weight loss, 4 years after immigrating to Canada. The patient was seropositive for human T-lymphotropic virus 1 (HTLV-1). No human immunodeficiency virus 1 or human immunodeficiency virus 2 antibodies were detected. The patient’s complete blood count values were within laboratory reference intervals, and there specifically was no evidence of adult T-cell leukemia. Upper endoscopy revealed only esophageal candidiasis, which was confirmed histologically. Duodenal biopsies contained clusters of lymphocytes with large pleomorphic nuclei that infiltrated mucosa, including glandular epithelium, and submucosa (Figure, large arrow). These lymphocytes stained with antibodies directed against CD45RO and showed no immunoreactivity for CD20. Adult T-cell lymphoma was diagnosed and was also found involving the stomach. In addition to the diffuse neoplastic process, Giardia lamblia (small arrow) and Strongyloides stercoralis parasites were identified in duodenal biopsies. Occasional cytomegalovirus inclusions within gastric glandular epithelium were also present. Stool examination for ova and parasites revealed S stercoralis rhabditiform larvae, eggs, and parasitic females. Giardia lamblia cysts and trophozoites were also identified. No filariform Strongyloides larvae were present. Human T-lymphotropic virus 1 is an oncogenic retrovirus with a global distribution that is endemic to Southeast Asia, southwestern Japan, the Caribbean, the southeastern United States, and West Africa.1,2 Environmental cofactors, such as Strongyloides parasitism, have been suggested as possible contributing mechanisms to HTLV-1– associated leukemogenesis.3 It is controversial whether HTLV-1 carriers are at increased risk for Strongyloides infection.1 Human T-lymphotropic virus 1–infected patients with adult T-cell leukemia/lymphoma, however, are immunocompromised and specifically have defects of cellmediated immunity.2 These patients are at increased risk for multiple opportunistic infections, including cytomegalovirus, herpes zoster, disseminated herpes simplex, Pneumocystis carinii, Cryptococcus, Candida, and enteric parasites, such as Strongyloides.2,4 Immunocompromised hosts with Strongyloides infections may develop autoinfection and disseminated strongyloidiasis as a result of direct transformation of rhabditiform larvae to filariform larvae

Strongyloides ratti: Thermokinetic Behavior of Third-Stage Larvae on a Temperature Gradient

Tobata-Kudo, H., Shimada, M., Koga, M., and Tada, I. 2000 Strongyloides ratii: Thermokinetic behavior of third-stage larvae on a temperature gradient. Experimental Parasitology95, 196–201. We examined the thermokinetic behaviors of infective third-stage larvae (L3) of the rodent parasitic nematode Strongyloides ratti on temperature gradients using an in vitro agarose tracking assay method. Observed behaviors included both negative and positive thermokineses, the direction of movement depending both on the gradient temperature at which larvae were initially placed and on prior experience of culture temperature. Larvae isolated from rat feces cultured at 25°C and placed on a gradient at temperatures between 22° and 29°C tended to move toward higher temperatures. At higher placement temperatures, most larvae moved little and showed no directional response, whereas at lower placement temperatures, many migrated toward cooler temperatures. At placement temperatures of 20°C or below, few or no larvae moved toward the zone of higher temperature. Larvae isolated from rat feces cultured at 20°C tended to migrate to a high temperature area regardless of placed temperature. Those cultured at 30°C did not respond to the temperature gradient. L3 cultured at 30°C were significantly less infective to rats than those cultured at 25° or 20°C. Additional experiments were designed to demonstrate thermokinetic behaviors during the period after reaching the L3 stage. Larvae incubated in double distilled water (DDW) for 24 h at 37°C lost their ability to respond to lower temperatures, while in those incubated in DDW at 15° and 25°C, responses were still apparent. The thermokinetic behavior of S. ratti L3 is affected by surrounding environmental temperatures and this may have an important role in host finding.

Efficacy of an in-feed formulation of ivermectin against adult worms and somatic larvae of Strongyloides ransomi

The efficacy of an in-feed formulation (IVOMEC® premix) containing 0.6% ivermectin was tested against Strongyloides ransomi in swine. The efficacy of ivermectin against patent infections of S. ransomi when given via the feed at 2 ppm for 7 days (Days 0–7) to provide 100 mcg ivermectin kg −1 body weight day −1 was evaluated in a study with 16 3-month-old male castrated piglets. Seven days prior to treatment each piglet was infected subcutaneously with 2500 infective larvae of S. ransomi. Fecal egg counts were carried out on Days −7, 0, 7 and 14, and worm counts on Day 14. Efficacy was 100% in all treated piglets. Two trials involving 40 pregnant gilts were carried out to evaluate the efficacy of ivermectin against the somatic larval stages of S. ransomi when given at a daily dose of 100 mcg kg −1 body weight for 7 days starting on Days 66, 78, 92 or 103 of pregnancy. The gilts were each experimentally infected with three subcutaneous injections of 250 000 infective larvae, with the last infection given between 12 and 30 days prior to commencement of treatment. Gilts were confirmed free of pre-existing intestinal stages of S. ransomi prior to ivermectin treatment. Fecal nematode egg counts were carried out in gilts/sows and piglets subsequently born. The Strongyloides larvae present in sow milk 1, 2 and 7 days post partum were counted. Fourteen days post natum, worm counts were performed in four randomly selected piglets from each litter. IVOMEC® premix given to pregnant gilts prevented shedding of larvae in sow milk, egg output in feces and the establishment of S. ransomi in piglets.

Coccidial and helminth infections in goats kept indoors in the Netherlands

An investigation was carried out on coccidial and helminth infections in goats kept indoors on five farms in the Netherlands. The goats were individually sampled. Coccidial oocysts were identified and nematode eggs counted. Larval cultures were made and infective larvae identified to the generic or species level. The goats were divided into three groups according to their age: kids, those weaned but not served, and older goasts. Oocysts were found in 26 out of 27 kids (96.3%), in 52 out of 55 weaned but not served goats (94.5%), and in 72 out of 110 older goats (65.5%). Eimeria ninakohlyakimovae was the most common species in all groups with an overall prevalence of 82%, followed by Eimeria arloingi (78%) and Eimeria aspheronica (53.3%). Other species present were Eimeria alijevi (50%), Eimeria christenseni (39.3%), Eimeria caprina (38.7%), Eimeria hirci (28.7%) and Eimeria jolchijevi (7.3%). Nematode eggs were seen on four of the five farms. It appeared that on two farms some goats, although now kept indoors, had been on pasture in the past. These goats excreted low numbers of eggs of Ostertagia and/or Trichostrongylus, Strongyloides papillosus, Haemonchus contortus, Trichuris spp. and larvae of Muellerius capillaris. In goats that were kept exclusively indoors, infections with Strongyloides papillosus were found on two farms in the older group and on one farm also in the group weaned but not served. On two farms Skrhabinema ovis was incidentally observed by the farmer in older goats. This was confirmed by faecal examinations on one farm. All kids were free of nematode infection.

Short Report: Gastric Infection by Strongyloides Stercoralis

Strongyloides stercoralis ordinarily matures in the human proximal small intestine and embeds in the small intestine mucosal wall where eggs are produced. Although Strongyloides may infect many sites in hyperinfection syndromes, reports of gastric involvement are rare. We report a patient taking prednisone and an H2 blocker who developed hyperinfection syndrome, with mucosal Strongyloides larvae seen in a gastric biopsy.

An alternative protocol for the serial passage and maintenance of a homogonic strain of Strongyloides ratti in female sprague-dawley rats

A method which does not involve the tedious use of watch glass coprocultures for obtaining filariform infective (L3) larvae of Strongyloides ratti from faecal pellets of infected Sprague-Dawley rats is described. The alternative method utilises Baermannization (18 h) of faecal pellets to yield rhabditiform (L1) larvae of S. ratti and their subsequent culture for 72 h at 19°C in tissue-culture-flasks containing only dechlorinated tap water to yield infective filariform (L3) larvae. The yields and infectivity of the L3 larvae obtained from the two methods were essentially similar.

Observations on strongyloidiasis in Queensland aboriginal communities.

To report the prevalence and distribution of infections with the parasitic nematode Strongyloides stercoralis in the Aboriginal and Torres Strait Islander communities of Queensland. A 20-year retrospective survey of computerised data and selected files from the former Aboriginal Health Programme (AHP) of the State Health Department of Queensland, based on cases diagnosed by the microscopic examination of preserved faecal specimens. Findings were compared with figures published in annual reports. Children under 15 years of age from 122 Aboriginal and Torres Strait Islander communities. Numbers of specimens examined varied widely according to time and place, as did detected infection rates. In 32,145 faecal samples examined by AHP microscopists during 1972-1991 the overall infection prevalence was 1.97%. Strongyloides larvae were found in only 52 of 122 communities. The parasite was absent from many small, southern inland communities, and the prevalence of infection increased in northern regions with summer wet seasons. On average, it was highest in Doomadgee (12%), where a peak prevalence of 27.5% (92/334 children examined) was detected in a wet season survey. Some infections resolved spontaneously, while others persisted for more than four years. At Gununa (Mornington Island), the prevalence fell from 26.2% to below 7% after thiabendazole treatment of most infected children, and remained at this level for at least four years. Single stool examinations by experienced microscopists may have failed to diagnose at least 26% of infected cases. The records give no indication of the clinical impact of strongyloidiasis. Strongyloidiasis is well established in many Aboriginal communities of north-eastern Australia. Children appear to be the major reservoirs of infection; the prevalence in adults is probably much lower. Failing improvements in community sanitation and hygiene, it may be possible to reduce significantly, if not eradicate, the infection by selectively treating diagnosed children with thiabendazole.

Successful treatment of disseminated strongyloidiasis

To report the successful treatment of Strongyloides stercoralis hyperinfection, which is usually lethal but in this case was diagnosed in its early stages. A 44-year-old woman, who had spent much of her life in Fiji and India, was treated with a high dose of prednisolone for rheumatoid arthritis complicated by gold lung. The onset of abdominal symptoms, an exacerbation of respiratory symptoms, and a persistent high eosinophil count and serum IgE level, led to the detection of numerous Strongyloides larvae in her faeces and sputum. She was treated with thiabendazole for five days, then mebendazole for one month, and the dose of prednisolone was reduced. Clinical symptoms and signs improved within days and after one week parasites could not be found in her faeces. After six months, enzyme-linked immunosorbent assay for Strongyloides infection gave a reading which was 40% of the initial level but still in the positive range. Steroid therapy in individuals with chronic, subclinical strongyloidiasis predisposes to the insidious development of hyperinfection syndrome, which has a high mortality rate. If detected early, this complication can be treated effectively. It can be prevented by actively seeking Strongyloides infection, by faecal microscopy and culture techniques and by serological tests, in high-risk individuals, such as immigrants from endemic areas.

Strongyloidiasis in Cotton Rats (Sigmodon hispidus) from Central Oklahoma

Thirty-one of 40 cotton rats (Sigmodon hispidus) collected from central Oklahoma were infected with Strongyloides sp. (78% prevalence). Larvae of Strongyloides sp. (rhabditiform or filariform) were not demonstrable in intestinal contents and scrapings. Female nematodes recovered from intestinal contents and scrapings had morphological similarities with Strongyloides sigmodontis. Cotton rats infected with Strongyloides sp. were indistinguishable clinically from non-infected hosts. Infected animals had no significant gross lesions, but the presence of Strongyloides sp. in the intestinal mucosa was associated with villus atrophy and mild to moderate infiltration of the lamina propria by lymphocytes, plasma cells and occasional eosinophils. Other organs or tissues examined were free from lesions induced by Strongyloides sp.

Parasite detection efficiencies of five stool concentration systems

Fresh fecal material that was free of ova and parasites was pooled with 10% Formalin in a 1:4 ratio to prepare a standard specimen. Portions of 100 ml of this specimen were individually seeded with Cryptosporidium oocysts, Entamoeba coli, Entamoeba histolytica, and Giardia lamblia cysts; ova of Necator americanus; and Strongyloides larvae. Appropriate volumes of each parasite suspension were used to evaluate the Fecal Concentrator Kit (Remel, Lenexa, Kans.), Fecal Parasite Concentrator (Evergreen Scientific, Los Angeles, Calif.), Para-Pak Macro-Con (Meridian Diagnostics, Inc., Cincinnati, Ohio), and Trend FeKal CON-Trate (Trend Scientific, Inc., St. Paul, Minn.). A standardized gauze filtration method was used as the reference procedure. Tests were performed in triplicate with each individual parasite-concentrator combination, with three slides examined from each sediment. All of the systems effectively concentrated parasites compared with direct examination of unconcentrated fecal material. The Fecal Concentrator Kit provided the best overall performance. Clarity of sediment, lack of debris, and uniformity of background material were found to be important considerations for microscopic detection of parasites in concentrated specimens.

Bacterial infections in patients with the hyperinfection syndrome: interactions between strongyloides larvae and gut bacteria

Bacterial infections in patients with the hyperinfection syndrome: interactions between strongyloides larvae and gut bacteria

A new method to detect Strongyloides stercoralis from human stool.

A new method for the detection of Strongyloides larvae was established. A small amount of stool was placed in the center of an agar plate and was incubated at 37°C for 24 hr. Characteristically aligned bacterial colonies or furrows left by crawling Strongyloides larvae appeared on the agar surface are the positive findings. The larvae gathered in a well made on positive plate were identified. By using this method, Strongyloides was detected in 46 cases (4.5%) out of 1, 017 healthy adults. Whereas, it was detected in 0 and 3 cases (0 and 0.3%) by direct stool smear method and filter paper technique, respectively. Examination of 246 cases by this agar plate method and formalinether method (MGL) revealed that 14 cases (5.7%) were positive by the former and 2 cases (0.8%) by the latter. Agar plate method is not laborious nor expensive, and recommendable for mass examination and for the detection of asymptomatic carriers.

Strongyloides spp.: Demonstration and partial characterization of acidic collagenolytic activity from infective larvae

Infective larvae of Strongyloides spp. have been shown to contain azocollytic enzymes which may aid in host skin penetration. Attempts to demonstrate classical, neutral pH-active collagenase activity in Strongyloides ratti were unsuccessful. In the current study, we investigated the presence of acidic collagenolytic activity in the infective larvae of Strongyloides ransomi, S. ratti, and S. stercoralis. All three species demonstrated collagenolytic activity in acidic homogenates as well as in neutral freeze-thaw fractions. Biochemical characterization of this collagenolytic activity from S. ratti and S. ransomi indicated that it was active over an acidic pH range, although it was stable at a neutral pH. This, along with molecular weight estimates and inhibitor susceptibilities, suggested that the collagenolytic activity was similar to vertebrate acidic cysteinyl proteinases. These studies also indicated that this activity is similar to the acidic cysteinyl proteinases in extracts of S. ransomi.

Host Age and Sex in Relation to Intestinal Helminths of Bobwhite Quail

grating in the cranium or those having reached the intestine. Nevertheless, esophagus length of larvae consistently increased with time after inoculation and with respect to localization of larval recovery. This finding coincides with recent work by Nojima et al. (1981, loc. cit.) and Mimori et al. (1982, loc. cit.). slip pressure can impact on arval length, it is ely tha th re were no diff re ces in body length We conclude that the Esophagus Index (EI) is a useful parameter for assessing development during migration of Strongyloides larvae in hosts, b cause few differences are found in morphological characters between the larvae before and after migration, and furthermore because manipulation of larvae affects their measurement. As well, use of the index seems to support the migration route for S. ratti larvae proposed by Hattori (1981, loc. cit.). l e t at the Esophagus Index (EI) is a eter for as es ing development i ation of Strongyloides larvae in hosts, ifferences are found in morpholog-

Pancreatic cystadenocarcinoma associated with Strongyloides

A 60-year-old woman presented with a mass in the left upper abdominal quadrant. Noninvasive studies showed a cystic structure arising from the pancreas. Pathologic studies of the tumor revealed pancreatic cystadenocarcinoma; the fluid contained Strongyloides larvae. There was no evidence of disseminated Strongyloides or immunosuppression. Results of stool examinations were also negative for Strongyloides. Were these larvae the etiologic agent for the carcinoma? Other parasitic infestations have been associated with carcinoma. This is the first reported association between Strongyloides and cystadenocarcinoma.

A controlled study of endemic sporadic diarrhoea among adult residents of southern Brazil

The aetiology of sporadic summer diarrhoea and enterotoxin (LT) antibody titres was studied among 43 adult patients in southern Brazil who had an acute, untreated diarrhoeal illness and 43 age- and sex-matched controls from the same area. A potential pathogen was identified in 33 of 34 patients and in 17 of 43 controls (p<0·01). 10 Shigella, one invasive Escherichia coli, one Salmonella and one Entamoeba histolytica were identified in 17 patients with inflammatory diarrhoea (faecal polymorphonuclear neutrophil leucocytes (PMN) present). In the other four only enterotoxigenic strains of E. coli were identified. Among 26 patients with non-inflammatory (no faecal PMN) diarrhoea, heat-stable (ST) toxin-producing coliforns were the most common pathogens isolated (27%). Heat-labile (LT) toxin-producing coliforms or serological rises to LT were seen in five patients, Strongyloides larvae in five, Giardia lamblia trophozoites in four and an LT-producing Salmonella in one. No pathogen was found in 10 patients with non-inflammatory diarrhoea. Among 43 controls, 11 LT coliforms, two Shigella and two Strongyloides larvae were found. 40 of 41 controls had detectable serum anti-LT antibody. A single ST-producing E. coli was found in one other control. No pathogen was identified in 26 controls. No rotaviruses or Norwalk-like viral agents were seen by direct or immune electron microscopy of stool filtrates. While LT-producing E. coli are frequently associated with endemic summer childhood diarrhoea in southern Brazil and are recognized causes of travellers' diarrhoea, this study shows that they are often carried asymptomatically by adults living in this region. ST-producing coliforms are the major non-invasive pathogen in adult residents with summer diarrhoea in an endemic area.

Association between Pelodera strongyloides (Nematoda: Rhabditidae) and wood mice, Apodemus sylvaticus.

Pelodera strongyloides larvae were found in the conjunctival sacs of Apodemus sylvaticus and Clethrionomys glareolus and in hair follicles of A. sylvaticus. Those in the eyes were 3rd-stage larvae while most of those in the dermis were early 4th stages. There was no evidence of pathology and sections of the skin showed that the nematodes of freshly killed mice and moulted once to the adult stage in 1-2 days at 15 degrees C. The stimulus to resume development appeared to be a reduction in temperature rather than presence of bacterial food or reduction in osmotic pressure. Countless generations ensued on nutrient agar provided the nematodes were periodically sub-cultured onto fresh agar. Nematodes from the eyes died in culture. Dauerlarvae of P. strongyloides were produced in exhausted cultures. They resumed development on fresh agar but not in distilled water. About half could be induced to exsheath by a temperature similar to that of mouse skin. A. sylvaticus probably accumulates nematode larvae in the dermis during its life and the nematodes resume development when the host dies.

A rapid technique for the recovery of strongyloid infective larvae from pasture and soil samples.

A technique is described for the recovery of infective larvae of strongyloid nematodes from sediment resulting from the washing of pasture and soil samples. The process of recovery and counting of larvae is described by a model based on the binomial distribution. Tests of the technique have shown that it will recover approximately 50% of the larvae present in samples of pasture sediment of either 7.5 or 12.5 ml in volume after centrifugation. The efficiency of the technique was independent of the number of larvae present in samples of pasture sediment. The technique was shown to be less efficient and more variable in recovery of larvae from samples of soil sediment. Estimations in efficiency of recovery from soil sediment ranged from 64 to 110.2% and a significant effect of volume of sediment on recovery was detected.

Strongyloides ratti: Susceptibility to infection and resistance to reinfection in inbred strains of mice as assessed by excretion of larvae

Eleven inbred strains of mice, and one outbred strain, were infected with Strongyloides ratti and larvae in the faeces were quantitated. Three strains, C57B1/6, CBA and BALB/c mice were susceptible to infection while other strains demonstrated negligible infections as assessed by this method. Larvae were first seen in the faeces on day 5, peak levels were reached on days 6 and 7, and excretion ceased 10 days after infection. Factors influencing intensity of larval excretion were examined in C57B1/6 mice. Young mice (1 month of age) were found to be more susceptible to infection than 2 and 6 month old animals. Male mice were much more susceptible to infection than female animals. There was a direct relationship between the number of S. ratti injected and the number of larvae excreted over the range 200–1600 larvae; subsequent increments in dose of injected larvae failed to increase the larval output. Infection by the percutaneous route resulted in a heavier infection than did subcutaneous injection. Previous exposure to S. ratti induced a profound resistance to reinfection. It is suggested that S. ratti infections of C57B1/6 and CBA mice provide a useful model for the investigation of factors influencing the host-parasite relationship in strongyloidiasis.

Tracking radioactive larvae of Strongyloides ratti in the host.

Infective larvae of homogonic Strongyloides ratti grown in faecal culture with 32P or 75Se acquired a significant amount of radioactivity which was firmly attached to them. Heating removed most of the 32P but left 75Se in place. Subcutaneous injection of virgin and nursing mother rats with living and heat-killed radioactive larvae resulted in a pattern of labelling in the small intestine of injected animals and, in the case of 75Se, those of suckling pups, which can only be explained if labelled worms follow the natural migratory routes. The use of this tool in migratory studies is discussed, with precautions to allow for flaws in the technique.