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PubMed1992

Strongyloides fuelleborni kellyi: infection and disease in Papua New Guinea.

A series o f unexplained deaths of two-month-old babies at on isolated mission station in Papua New Guinea led to the description o f a parasitic disease with unique and intriguing features. The parasite was named Strongyloides fuelleborni kellyi; S. fuelleborni is normally a parasite of non-human primates in Africa and Asia and of humans in Africa. How did the new subspecies reach non-human primate-free New Guinea? How do infants become infected in the first few days after birth? Why is the fatal disease restricted to two small areas while the infection itself is widespread? Ten years of study have only begun to indicate answers, as discussed here by Dick Ashford, Guy Barnish and Mark Viney.

Journal Article↗
PubMed1996

Amphids in Strongyloides stercoralis and other parasitic nematodes.

In this review, Francis Ashton and Gerhard Schad examine the ultrastructure of the amphids of several animal parasitic nematodes. These structures are the main chemosensory organs of these worms and probably play an important role in host-finding behavior and the control of development. Reconstructions made from serial micrographs of the neurons in the amphids of the threadworm Strongyloides stercoralis are shown. These stereo images permit three-dimensional visualization of these complex sense organs. The association between each amphidial neuron and its cell body has not been made previously for a parasitic nematode; however, this has been done for the free-living nematode Caenorhabditis elegans, which served as a model for these studies. Recognition of the cell bodies will provide a point of departure for laser microbeam ablation studies to determine individual neuronal function.

Journal Article↗
PubMed1992

Sudden death of calves by experimental infection with Strongyloides papillosus. II. Clinical observations and analysis of critical moments of the disease recorded on videotape.

Four calves experimentally infected with different doses of Strongyloides papillosus were examined for changes of body temperature and other clinical parameters. Also, the critical moments of death, which were recorded on videotape, were analyzed in detail. The first clinical signs included initial accelerated respiration. In general, body temperature was almost normal; however, one calf showed a slight increase after 2 or 3 days of infection, and two calves a gradual increase 7 days after infection. Vocal noises and general spasms were observed 5-14 times during the course of death. Initial vocal noises were heard between 0:50 and 1:30 (minute:second) after the appearance of the initial clinical signs. The final spasm, preceding death, occurred between 3:05 and 3:40 after the appearance of the initial clinical signs.

Animals↗
PubMed1993

Sudden death of calves by experimental infection with Strongyloides papillosus. III. Hematological, biochemical and histological examinations.

Nine calves infected percutaneously with graded doses of Strongyloides papillosus (SPL) were examined for hematological, biochemical and histological changes during the infection. Six of the calves infected with the highest larval doses died suddenly and the three calves given lower doses survived. No changes were observed in blood cell counts except for a transient eosinophilia. Parameters of the blood coagulation system and blood gas remained normal. A decrease in blood glucose was observed in four of the calves that died after the prepatent period of the parasite. However, endotoxic shock could be ruled out as a cause of death because of normal platelet counts, no intravascular coagulation and low levels of serum endotoxin. A transient increase of creatine kinase was observed in three of the calves that died; however, myocardial infarction or myocarditis were not observed. No lesions were observed except for minor inflammatory changes in the lungs and slight cellular infiltrations in the heart. In the absence of any consistent hematological, biochemical or histological changes in the calves that died, the present study failed to demonstrate mechanisms underlying sudden death due to SPL infection.

Animals↗
PubMed1999

Secondary structure model for the ITS-2 precursor rRNA of strongyloid nematodes of equids: implications for phylogenetic inference.

In order to maximise the positional homology in the primary sequence alignment of the second internal transcribed spacer for 30 species of equine strongyloid nematodes, the secondary structures of the precursor ribosomal RNA were predicted using an approach combining an energy minimisation method and comparative sequence analysis. The results indicated that a common secondary structure model of the second internal transcribed spacer of these nematodes was maintained despite significant interspecific differences (2-56%) in primary sequences. The secondary structure model was then used to refine the primary second internal transcribed spacer sequence alignment. The 'manual' and 'structure' alignments were both subjected to phylogenetic analysis to compare the effect of using different sequence alignments on phylogenetic inference. The topologies of the phylogenetic trees inferred from the manual second internal transcribed spacer alignment were usually different to those derived from the structure second internal transcribed spacer alignment. The results suggested that the positional homology in the second internal transcribed spacer primary sequence alignment was maximised when the secondary structure model was taken into consideration.

Animals↗
PubMed1998

Recovery from arrhythmias in lambs infected with Strongyloides papillosus following worm elimination.

Calves and lambs heavily infected with Strongyloides papillosus develop cardiac arrest by ventricular fibrillation which is preceded by continuous sinus tachycardia and prolongation of the PQ interval during the patent infection. In the present study, cardiac rhythms following anthelmintic treatment were investigated in lambs infected with S. papillosus to ascertain whether cardiac disorders due to the infection are based on a reversible and curable change. Eight lambs were given a lethal dose of S. papillosus. Five of the animals were injected with ivermectin when they developed continuous sinus tachycardia and prolongation of the PQ interval. The other three animals served as untreated controls. In the treated animals, elevated heart rates and PQ intervals began to decrease between 10 and 21 h, then continuous sinus tachycardia and prolongation of PQ interval disappeared within 39 h of treatment. No arrhythmias were detected after the disappearance of sinus tachycardia. Faecal egg counts became negative within 61 h of treatment. Only a few worms were collected from the small intestine at necropsy. The control animals developed ventricular fibrillation by 349 h after infection, having high faecal egg counts and intestinal worm burdens. These results indicate that cardiac disorders generated by S. papillosus infection are reversible and curable following worm elimination.

Animals↗
PubMed1980

Development of Pelodera strongyloides (Schneider, 1860) Schneider, 1866 (Nematoda: Rhabditidae) in culture.

Dauerlarvae of Pelodera strongyloides, recovered from two species of lemmings, Dicrostonyx groenlandicus (Traill) and Lemmus trimucronatus (Richardson) trapped at Eskimo Point, N.W.T, were cultured on agar medium with E. coli. Development from egg to adult stage was followed. Eggs hatched between 22 and 26 hours at 22 degrees C. The first moult occurred 24 to 28 hours after the eggs hatched, the second at 40 to 48 hours, the third at 60 to 64 hours and the fourth at 84 to 88 hours at 22 degrees C. Adults lived approximately 5 to 6 days and females oviposited for 2 to 3 days during this time. All stages were measured and described. The effect of temperature on development was examined. Dauerlarvae survived freezing temperatures, short periods of desiccation and prolonged periods without food.

Animals↗
PubMed1983

Demonstration of collagenase activity in adult Strongyloides ratti (Nematoda:Strongyloididae) and its absence in the infective larvae.

Larvae and adults of Strongyloides ratti were examined for collagenolytic activity on 14C proline-labelled, native, guinea-pig skin collagen substrate. The activity was measured by determining either the amount of hydroxyproline released or the amount of radioactivity in the solubilized fraction of the collagen substrate. Bacterial collagenase was used for enzyme control and trypsin served as substrate control. No collagenolytic activity was found in living larvae, their extracts or metabolites. The collagenolytic activity of the metabolites of adult worms appeared weak, whereas that of the extracts of the adults was pronounced. It is suggested that collagenase is active in the adult females at the time of migration in the intestinal mucosa during oviposition.

Animals↗
PubMed1996

The structure of the community of strongyloid nematodes of domestic equids.

The community structure exhibited by strongyloid nematodes from the large intestines of horses was examined using data from autopsies of 150 horses. Thirty-one species of nematodes were encountered, but they were not clearly divisible into core and satellite species. Multiple congeneric, consubfamilial and confamilial species were a prominent feature of the community and were more common than singleton infections. Multivariate analyses provided evidence of a stable community of helminths dominated by positive interactions but with few negative interactions, suggesting the absence of competition within the community.

Animals↗
PubMed1980

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.

Animals↗
PubMed1976

Dynamic determinants of the route of larval Strongyloides ratti in lactating rats and the control of experimental error in quantitative studies of milk transmission of skin-penetrating roundworms.

Subcutaneous injection of nursing mothers from day 16 to day 20 post partum with infective larvae of Strongyloides ratti or Nippostrongylus brasiliensis does not result in the development of worms in the litters if 1 h is allowed between injection and resumed nursing and suckling is terminated 24 h later. Thus the low numbers of N. brasiliensis (1% of the dose) which develop in litters after 24 h, 4 day or 5 days suckling when mothers are injected and returned to their young immediately, represent skin invasion and not milk-borne infection. Taking precautions consistent with the foregoing, S. ratti equivalent to 28%, 45%, 45% and 48% of the dose were shown to be transmitted in the milk to suckling rats of 4 mothers injected with 4000 L 3 on day 18 post partum and 72 h before weaning. One mother of the same batch failed to transmit worms (1% of the dose in the litter) and the take in all 5 mothers was insignificant (max. = 3% of the dose versus an average of 21% in controls). Large numbers of S. ratti were subsequently found in the intestines of mothers whose litters were weaned immediately after (21%) or 6 h after (16%) injection, whereas very few (less than 1%) developed in mothers deprived of their offspring 24 h after injection. Dynamic, rather than static, determinants of larval routes inside the host present the only logical basis for an explanation of these facts.

Animals↗
PubMed1978

Strongyloides ratti: the effect of betamethasone on the course of infection in rats.

Rats were treated with betamethasone at different stages of infection with Strongyloides ratti. Treatment caused a diminution in the number of adult worms recovered but this residual population was not expelled as were worms from untreated rats. If treatment was started after expulsion had already begun adult worm numbers increased--suggesting that autoinfection occurred. Treatment throughout a primary infection prevented the development of an immune response which expelled, or killed, a challenge infection. Treatment, just before and just after challenge, prevented the expulsion of the challenge infection. Worm expulsion up to day 35 was prevented by treating rats with betamethasone 4, 6, 8 and 10 days after infection.

Animals↗
PubMed1976

Milk-borne infection of rats with Strongyloides ratti and Nippostrongylus brasiliensis.

The numbers of mature worms which developed in young rats after their mothers were injected with 4000 L3 late in lactation were 1% (Nippostrongylus brasiliensis) and 24% (Strongyloides ratti) of the dose administered. The low value for N. brasiliensis validates the conclusion that milk is a real and important vehicle for infection in S. ratti since possible errors from skin invasion of the young would have been common to both species. The level of mature S. ratti infection in lactating mothers in this experiment was negligible, 97-99% of the adult worms appearing in the offspring. These results may indicate that the milk route is possible with N. brasiliensis even though it is quantitatively insignificant.

Animals↗
PubMed1996

Foal diarrhoea between 1991 and 1994 in the United Kingdom associated with Clostridium perfringens, rotavirus, Strongyloides westeri and Cryptosporidium spp.

A case control study of foal diarrhoea in the United Kingdom was carried out over a 3-year period. Clostridium perfringens was significantly associated with foal diarrhoea (Odds Ratio (OR) = 3.0), being isolated from 57% of 421 animals with diarrhoea but from only 27% of 223 healthy foals. Also, C. perfringens was significantly associated with fatal diarrhoea (OR = 4.5). About half of diarrhoea with a fatal outcome was attributable to this organism. The other pathogens significantly associated with diarrhoea were rotavirus (OR = 5.6), Cryptosporidium spp. (OR = 3.2) and the nematode Strongyloides westeri, which was significant only when present in large numbers (> 2000 eggs/g of faeces: OR = 6.1). Salmonella spp. (OR = 14.2) and Cryptosporidium spp. (OR = 3.0) were the only other pathogens associated with fatal illness. Overall, C. perfringens, rotavirus, and large numbers of Cryptosporidium spp. or S. westeri were isolated from 80% of foals with diarrhoea. Thermophilic Campylobacter spp., Yersinia enterocolitica, Escherichia coli and other parasites were not associated with diarrhoea. Carriage of C. perfringens, rotavirus and Cryptosporidium spp. was significantly greater in healthy foals in contact with cases of diarrhoea than in foals that were not in contact with diarrhoea (P < 0.05). There were no statistical interactions between any of the pathogens associated with diarrhoea although separate cases from one location often involved more than one pathogen.

Animals↗
PubMed1984

Effect of androgen on the expression of the sex difference in susceptibility to infection with Strongyloides ratti in C57BL/6 mice.

The possible site of expression of the sex difference in susceptibility to infection with Strongyloides ratti was studied in C57BL/6 mice. The intensity of infection, measured by daily larval output in faeces or by intestinal worm burden, was significantly higher in males than in females. This sex difference was already expressed during the migration of larvae from the site of subcutaneous inoculation to the cranial cavity or lung as early as 24 h after infection. Conversely, there was no significant difference in the larval output in faeces or in the worm burden of male or female recipients after implantation of adult worms using a stomach tube. When the susceptibility to infection with S. ratti of gonadectomized animals was examined, the daily larval output in faeces of orchidectomized males was significantly reduced to the level of intact females, while ovariectomy had no effect, suggesting that androgen is one of the important regulatory factors for the expression of sex difference. In fact, testosterone treatment of orchidectomized males or normal females could increase their susceptibility to or above the level of intact males. These results strongly suggest that sex difference in the susceptibility to infection with S. ratti in C57BL/6 mice is mediated by 'natural defence mechanisms' which are under the regulation of testosterone.

Animals↗
PubMed1985

[Inhibition of Plasmodium berghei in rats infested with Strongyloides ratti or Trichinella spiralis; role of high blood corticosterone in reaction to the development of helminths].

The plasma corticosterone induced in the rat by the development of Strongyloides ratti or Trichinella spiralis reaches a sufficient level of intensity to determine reticulocytopenia. The latter is linked chronologically to the inhibition of parasitemia in Plasmodium berghei, which occurs when this protozoa develops at the same time as the Nematodes, and seems to be the causal factor. This hypothesis may be verified by replacing the helminths with the corticotropic action of A.C.T.H. which causes a decrease in the number of reticulocytes.

Adrenocorticotropic Hormone↗
PubMed1983

The effects of 22, 23-dihydroavermectin B1 on Strongyloides ratti and S. stercoralis infections in mice.

The efficacy of the avermectin compound 22, 23-dihydroavermectin B1 against murine strongyloidiasis has been examined. A daily dose of 4 micrograms (200 micrograms kg-1) totally suppressed excretion of Strongyloides ratti larvae in the faeces. A similar marked suppression was seen when 10 micrograms (500 micrograms kg-1) of the drug was given on two days during the phase of larval migration or during the intestinal phase. Avermectin did not affect larval numbers in the skin but reduced larval numbers in the lungs by 91%. Administration of avermectin during the phase of larval migration completely prevented the subsequent appearance of adult worms in the gut. A single dose of 50 micrograms (2.5 mg kg-1) eradicated intestinal adult worms. Some variability was noted in dose-response studies, but the drug was very potent and a dose of 50 micrograms (2.5 mg kg-1) always eradicated the worms. Avermectin greatly reduced the numbers of S. stercoralis larvae in the muscles, whether it was given early or late in the infection. Eradication of S. stercoralis larvae from muscle followed a single dose of 100 micrograms (5 mg kg-1). It is concluded that this avermectin could be valuable in the treatment of human strongyloidiasis.

Animals↗