scholarly journals Density-dependent effects on the survival and growth of the rodent stomach wormProtospirura muricolain laboratory mice

2004 ◽  
Vol 78 (2) ◽  
pp. 121-128 ◽  
Author(s):  
F.M. Lowrie ◽  
J.M. Behnke ◽  
C.J. Barnard
Keyword(s):  
Parasite Burden ◽  
Parasite Growth ◽  
Laboratory Mice ◽  
Density Dependent ◽  
Infective Larvae ◽  
Third Stage ◽  
Survival And Growth ◽  
Stomach Weight ◽  
Higher Doses ◽  
Dependent Processes

AbstractThe spirurid nematode,Protospirura muricola, is of intrinsic interest as a rodent model of gastric nematode infections. Since worm burdens can be very heavy in nature, density dependent processes may constrain parasite growth. Laboratory mice (BKW) were exposed to varying doses of infective larvae ofP. muricolain the range 5 to 40 third-stage larvae (L3), in four separate experiments in which progressively higher doses were utilized. All mice were culled 60 days after infection and a total of 518 worms (226 male and 292 female worms) was recovered, measured and weighed. Overall survival was 58.9%, but survival declined significantly with increasing dose by approximately 21% (from 66% at 5 L3 per mouse to 52% at 40 L3 per mouse). The length and weight of worms correlated positively in both sexes. Total worm biomass increased linearly with increasing numbers of worms. However, whilst the length and weight of male worms declined with increasing worm burden (8.4 and 24.6% respectively), female worms were less affected, only length showing a significant reduction with increasing parasite burden (16.0%). Therefore, increasing worm burdens impeded growth ofP. muricola, but reduction in length and weight were relatively small in relation to the overall size of this nematode. Increasing worm burdens were associated with loss of host weight and reduction in stomach weight and worm burdens in excess of 20 exerted a measurable cost to the host, which in the field, may be associated with loss of overall host fitness.

Density-dependent regulation of the growth of the hookworms Necator americanus and Ancylostoma ceylanicum

Parasitology ◽  
1994 ◽  
Vol 109 (1) ◽  
pp. 119-128 ◽  
Author(s):  
S. M. B. Norozian-Amiri ◽  
J. M. Behnke
Keyword(s):  
Worm Burden ◽  
Infection Intensity ◽  
Dry Weight ◽  
Ancylostoma Ceylanicum ◽  
Density Dependent ◽  
Necator Americanus ◽  
Infective Larvae ◽  
Length Width ◽  
Negative Relationships ◽  
Dependent Processes

SUMMARYLaboratory bred DSN hamsters were exposed to varying doses of infective larvae of Ancylostoma ceylanicum (orally) or Necator americanus (percutaneously) and were autopsied at times which corresponded to a period immediately before cessation of growth of worms or soon afterwards. A total of 829 (404 male and 425 female) A. ceylanicum and 1582 (781 male and 801 female) N. americanus were measured. At worm burdens of fewer than 100, the length of A. ceylanicum appeared to increase with infection intensity and no evidence was found that growth was retarded under crowded conditions. In an experiment comparing directly low (mean worm burden = 22) and heavy infections (mean worm burden = 180) significant negative associations between both weight and width, and worm burden were detected, but length again increased with worm burden. In contrast, 5 experiments with N. americanus indicated negative relationships between measures of worm size (length, width, wet and dry weight) and worm burden. It was concluded that N. americanus is subject to regulation by density-dependent processes within the host while A. ceylanicum is not sensitive to the same degree.

Soil fungal networks moderate density‐dependent survival and growth of seedlings

2021 ◽  
Author(s):  
Minxia Liang ◽  
Liuqing Shi ◽  
David F. R. P. Burslem ◽  
David Johnson ◽  
Miao Fang ◽  
...  
Keyword(s):  
Density Dependent ◽  
Moderate Density ◽  
Survival And Growth ◽  
Growth Of Seedlings

scholarly journals Efficacy of Nitazoxanide againstCryptosporidium parvum in Cell Culture and in Animal Models

1998 ◽  
Vol 42 (8) ◽  
pp. 1959-1965 ◽  
Author(s):  
Cynthia M. Theodos ◽  
Jeffrey K. Griffiths ◽  
Jennifer D’Onfro ◽  
Alexandra Fairfield ◽  
Saul Tzipori
Keyword(s):  
Cell Culture ◽  
Clinical Trials ◽  
Body Weight ◽  
Animal Models ◽  
Cryptosporidium Parvum ◽  
Combined Treatment ◽  
Parasite Burden ◽  
Parasite Growth ◽  
Gnotobiotic Piglet

ABSTRACT Nitazoxanide (NTZ), a drug currently being tested in human clinical trials for efficacy against chronic cryptosporidiosis, was assessed in cell culture and in two animal models. The inhibitory activity of NTZ was compared with that of paromomycin (PRM), a drug that is partially effective against Cryptosporidium parvum. A concentration of 10 μg of NTZ/ml (32 μM) consistently reduced parasite growth in cell culture by more than 90% with little evidence of drug-associated cytotoxicity, in contrast to an 80% reduction produced by PRM at 2,000 μg/ml (3.2 mM). In contrast to its efficacy in vitro, NTZ at either 100 or 200 mg/kg of body weight/day for 10 days was ineffective at reducing the parasite burden in C. parvum-infected, anti-gamma-interferon-conditioned SCID mice. Combined treatment with NTZ and PRM was no more effective than treatment with PRM alone. Finally, NTZ was partially effective at reducing the parasite burden in a gnotobiotic piglet diarrhea model when given orally for 11 days at 250 mg/kg/day but not at 125 mg/kg/day. However, the higher dose of NTZ induced a drug-related diarrhea in piglets that might have influenced its therapeutic efficacy. As we have previously reported, PRM was effective at markedly reducing the parasite burden in piglets at a dosage of 500 mg/kg/day. Our results indicate that of all of the models tested, the piglet diarrhea model most closely mimics the partial response to NTZ treatment reported to occur in patients with chronic cryptosporidiosis.

Improved Methods of Obtaining Clean Larvae of Haemonchus contortus

1963 ◽  
Vol 37 (4) ◽  
pp. 251-254 ◽  
Author(s):  
M. G. Christie ◽  
J. E. Patterson
Keyword(s):  
Free Surface ◽  
Surface Area ◽  
Haemonchus Contortus ◽  
Water Repellent ◽  
Optimum Conditions ◽  
Infective Larvae ◽  
Mucous Coat ◽  
Third Stage ◽  
Free Surface Area ◽  
Improved Methods

A pellet of sheep faeces containing eggs of Haemonchus contortus forms an adequate environment for the development of those eggs to third stage infective larvae, provided that it is kept moist. Observation shows a concentration of developing larvae on the external mucous coat of the pellet. These data suggest that optimum conditions for development would occur when pellets are separated one from another and standing on a water repellent surface, thus presenting the maximum free surface area and minimum opportunity for aggregation and hence of over crowding. The best method of recovering the infective larvae would be one that obtained larvae free from contamination without requiring them to expend energy in separating themselves from the contamination.

Studies on resistance of sheep to infestation with Haemonchus contortus and Trichostrongylus spp. and on the immunological reactions of sheep exposed to infestation. I. The preparation of antigens for the complement fixation test and the reactivity of the biochemical fractions of H. contortus

1950 ◽  
Vol 1 (3) ◽  
pp. 285 ◽  
Author(s):  
DF Stewart
Keyword(s):  
Haemonchus Contortus ◽  
Complement Fixation Test ◽  
Complement Fixation ◽  
Fixation Test ◽  
Mature Adult ◽  
Infective Larvae ◽  
Lipid Fractions ◽  
Significant Difference ◽  
Third Stage ◽  
Free Material

All antigen was developed to detect circulating antibodies by means of the complement fixation test in sheep infested with Haemonchus contortus and Trichostrongylus spp. Extraction of worm material at 100°C. for 10 minutes was found to be the most satisfactory method for the preparation of antigens. Potent antigens were prepared from young adult H. contortus, from third-stage infective larvae, and from the eggs. Old mature adult H. contortus yielded antigens of low potency. No significant difference was found between the potency of antigens prepared from male and female adult H. contortus collected from the same sheep. Both adult Trichostrongylus spp. and third-stage infective larvae consistently yielded antigens of high potency. No significant difference was found in the results obtained with larval or adult H. contortus antigens, adjusted to the same potency and tested with natural H. contortus antisera. H. contortus and Trichostrongylus spp. absorbed the antiserum to each other. It was shown that a lipid was an essential constituent of the boiled antigen in the complement fixation reaction with natural antisera. Lipid-free antigens from H. contortus failed to react with natural antisera. The lipid was not antigenic when injected into rabbits. The carbohydrate fraction of H. contortus did not fix complement in the presence of natural antisera and was not antigenic when injected into rabbits. The lipid fraction of a variety of nematode parasites reacted with natural antisera to H. contortus infestation. Similar lipid fractions of two species of trematodes did not react with natural antisera to H. contortus infestation. Normal saline suspensions of the lipid-free material from a variety of helminths showed a greater degree of specificity when tested with artificially prepared antisera than did the lipid fractions.

Multiple density-dependent processes shape the dynamics of a spatially structured amphibian population

2018 ◽  
Vol 88 (1) ◽  
pp. 164-177 ◽  
Author(s):  
Hugo Cayuela ◽  
Benedikt R. Schmidt ◽  
Avril Weinbach ◽  
Aurélien Besnard ◽  
Pierre Joly
Keyword(s):  
Amphibian Population ◽  
Density Dependent ◽  
Dependent Processes

scholarly journals Chemosensory mechanisms of host seeking and infectivity in skin-penetrating nematodes

2020 ◽  
Vol 117 (30) ◽  
pp. 17913-17923 ◽  
Author(s):  
Spencer S. Gang ◽  
Michelle L. Castelletto ◽  
Emily Yang ◽  
Felicitas Ruiz ◽  
Taylor M. Brown ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Strongyloides Stercoralis ◽  
Sensory Cues ◽  
Ancylostoma Ceylanicum ◽  
Free Living ◽  
Infective Larvae ◽  
Host Seeking ◽  
Third Stage ◽  
Olfactory Preferences ◽  
Insight Into

Approximately 800 million people worldwide are infected with one or more species of skin-penetrating nematodes. These parasites persist in the environment as developmentally arrested third-stage infective larvae (iL3s) that navigate toward host-emitted cues, contact host skin, and penetrate the skin. iL3s then reinitiate development inside the host in response to sensory cues, a process called activation. Here, we investigate how chemosensation drives host seeking and activation in skin-penetrating nematodes. We show that the olfactory preferences of iL3s are categorically different from those of free-living adults, which may restrict host seeking to iL3s. The human-parasitic threadwormStrongyloides stercoralisand hookwormAncylostoma ceylanicumhave highly dissimilar olfactory preferences, suggesting that these two species may use distinct strategies to target humans. CRISPR/Cas9-mediated mutagenesis of theS. stercoralis tax-4gene abolishes iL3 attraction to a host-emitted odorant and prevents activation. Our results suggest an important role for chemosensation in iL3 host seeking and infectivity and provide insight into the molecular mechanisms that underlie these processes.

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