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PubMed2003

Lotus japonicus: a new model to study root-parasitic nematodes.

Sedentary plant-parasitic nematodes engage in complex interactions, and induce specialized feeding structures by redirecting plant developmental pathways, and parallels have been observed with rhizobial nodule development on legumes. A model legume would greatly facilitate a better understanding of the differences between parasitic (nematode) and mutualistic (rhizobia and mycorrhizae) symbioses, and we have developed Lotus japonicus as such a model. Conditions for efficient parasitism by root-knot nematode (Meloidogyne spp.) of the widely used Lotus "Gifu" ecotype were established. Features of Lotus biology, such as thin and translucent roots, proved ideal for monitoring the progress of nematode infection both on live specimens and post-staining. We examined L. japonicus mutants with nodulation phenotypes. One, har1, which is a hypernodulated mutant defective in a CLAVATA1-like receptor kinase gene, was found to be hyperinfected by M. incognita. However, another hypernodulated Lotus mutant exhibited the same level of M. incognita infection as wild-type plants. We also established conditions for infection of Lotus by soybean cyst nematode (Heterodera glycines). In contrast to the response to root-knot nematode, the Gifu ecotype is resistant to H. glycines, and elicits a hypersensitive response. This pattern of resistance recapitulates that seen on nematode-resistant soybean plants. We conclude that L. japonicus is a powerful model legume for studying compatible and incompatible plant-nematode interactions.

Animals↗
PubMed1978

Levamisole in ascariasis. A multicenter controlled evaluation.

An analysis is presented of 10 clinical studies from various countries where levamisole 50--150 mg was compared to pyrantel, piperazine, and placebo in a total of 1,734 patients, mostly children (levamisole: 830, controls: 904), suffering from ascariasis either as a single infection or usually mixed with other nematode infections. Degree of infection and efficacy of treatment were determined by quantitative coproparasitological methods. Levamisole produced higher cure rates (91%) and egg reduction rates (98%) than pyrantel, piperazine, or placebo. The efficacy of levamisole was unrelated to the patients' sex and age, the severity of infection, the presence of another worm infection, the type of associated worm infections, or the egg-counting technique. The overall incidence of reported adverse reactions was lower after levamisole than after piperazine, pyrantel or placebo; abdominal pain and headache, the most frequent complaints after levamisole, were related to the initial severity of ascariasis. Follow-up examinations 6 months after treatment suggested that levamisole might delay reinfection.

Adolescent↗
PubMed1992

A model for nematodiasis in New Zealand lambs.

A strategic model is described for the epidemiology of mixed nematode infections in New Zealand lambs. The model successfully reproduces known patterns of parasite epidemiology and production loss in lambs under currently implemented control strategies. The variation in model output during sensitivity analysis was within acceptable limits defined by field data. Model output was most sensitive to variation in parameters affecting survival and migration of the free-living stages and host resistance to infection, suggesting that these factors are most influential in regulating parasite populations. It is intended to use the model to focus research on key aspects of nematode epidemiology and control and, following the incorporation of appropriate genetic mechanisms, anthelmintic resistance.

Animals↗
PubMed1980

Persistence on pasture of the infective larvae of nematodes parasitizing Maine dairy cattle.

Yearling calves infected with Ostertagia ostertagi, Cooperia oncophora, and Nematodirus helvetianus were allowed to graze on a 0.8 ha pasture plot contaminated during June and August 1977. In June 1978, the plot was subdivided into 10 subplots of equal size. Grazing in 5 of these plots was allowed, each for 1 month, during June, July, August, September, and October by groups of 2 parasite-free 16-week-old calves. The procedure was repeated in 1979 with the remaining 5 subplots. Each group of calves was allowed to graze for 2 weeks, then put into stalls for 2 weeks and killed and examined for worms. There was a good survival of the 3 worm genera over the winter period of 1977-78. In June, calves averaged 250 Ostertagia, 5,345 Cooperia, and 6,955 Nematodirus. Ostertagia and Cooperia were recovered from calves grazing in September and October. The 3rd genus, Nematodirus, also became less plentiful over the summer period, but persisted in calves grazing during September and October. This genus survived a 2nd winter on pasture and worms were recovered until July, 1979.

Animals↗
PubMed1992

Epidemiological study of parasite infection in a cow-calf beef herd in Quebec.

The patterns of gastrointestinal and pulmonary nematode infections in a previously untreated Aberdeen Angus cow-calf herd were observed between May 1988 and December 1990. The cow-calf herd and replacement heifers were on separate pastures. The relatively high mean faecal egg counts of cows and heifers at the time of turnout were mainly owing to the maturation of hypobiotic worms. The strongyle egg counts of calves began to rise soon after turnout onto pasture and reached peak levels at the end of the grazing season. The number of infective larvae on pasture was highest during September/October. Ostertagia, Cooperia and Nematodirus were the most prevalent genera found at necropsy and on pasture. Larvae of these nematodes were able to overwinter on pasture and Ostertagia larvae, additionally, were able to overwinter in the host as arrested early fourth stage larvae. The high egg output of cows at the time of turnout may serve as a source of infection for their calves and be responsible for the late-season rise in pasture larval counts.

Animals↗
PubMed1984

Relationship of histamine in tissues and antiparasitic substances in gastrointestinal mucus to the development of resistance to trichostrongyle infections in young sheep.

The development of resistance to nematode infection and self-cure in a flock of young grazing sheep were examined in relation to changes in the levels of histamine in tissues and levels of antiparasitic substances in gastrointestinal mucus. Analysis of faecal egg counts showed that when the sheep were ranked according to individual mean monthly egg counts there was a significant trend to similar rankings in successive months. Sheep with high and low egg counts were slaughtered at monthly intervals for examination and comparison. Histamine levels in blood and intestinal content fluids were similar in both groups of sheep and were highest during maximum challenge by larval nematodes. Antiparasite activity of the intestinal mucus was significantly higher in sheep with low egg counts than those with high counts, between January and May, and was associated with significantly lower burdens of fourth stage larvae.

Abomasum↗
PubMed1979

Imported parasitic infections in Tasmania.

A number of protozoan, trematode, and nematode infections have been imported into Tasmania over an 18-month period. Some of the cases are briefly discussed as they provide features of clinical interest. The increasing problem of imported infections in Australia is emphasized.

Africa, Northern↗
PubMed1997

Colonic Strongyloides stercoralis infection masquerading as ulcerative colitis.

Strongyloides stercoralis is a nematode infection which predominantly involves the small bowel. Spillover infection to the colon does occur, but is uncommon and is usually associated with an immunocompromised host. Accurate diagnosis is essential and, as this case demonstrates, a long history does not preclude an infective aetiology.

Animals↗
PubMed1993

Notes on necropsy and herbage processing techniques for gastrointestinal nematodes of ruminants.

Necropsy techniques for the digestive tract of ruminants used at the University of Utrecht differ from those used elsewhere in three respects: (1) the abomasum is opened immediately after slaughter and the "contents" are treated separately from the "washings"; (2) the first 10 m of the small intestine are treated separately from the remainder of the intestine; (3) the aliquots are coloured with iodine before being examined for worms. The majority of the worms are found in the washings of the abomasum and the first part of the small intestine, whereas the contents of the abomasum and the remainder of the small intestine contain the bulk of the digesta. Because inhibited stages of Ostertagia, Haemonchus and, particularly, the very small third stage larvae (L3) of Trichostrongylus can be overlooked easily in digesta, these methods imply a more rapid and accurate enumeration of worms. This is more important in small ruminants than in cattle because a much higher proportion of the inhibited larvae will be washed out of the mucosa and because Trichostrongylus is more important in small ruminants. Herbage sampling methods for monitoring gastrointestinal nematode infections on cattle pastures in northwest Europe should also be suitable for lungworm. The agar-bile technique of Jørgensen is an elegant method, but disadvantages are that many gastrointestinal nematode larvae exsheath, resulting in identification difficulties, and recovery of lungworm larvae decreases as a result of ageing. A simple sucrose flotation method, based on the principle that a sucrose solution does not mix easily with water containing nematodes, has been tested at our laboratory.(ABSTRACT TRUNCATED AT 250 WORDS)

Abomasum↗
PubMed2006

Effect of CD4+ T lymphocyte depletion on resistance of Gulf Coast Native lambs to Haemonchus contortus infection.

It has been reported that CD4(+) T lymphocytes are important in acquired immunity to gastrointestinal nematode infection. Whether these lymphocytes are also involved in the immune response of naturally resistant Gulf Coast Native (GCN) sheep to Haemonchus contortus infection remains to be defined. The objective of this study was to determine the role of CD4(+) T lymphocytes in this resistance. Ten GCN lambs were randomly assigned to a control (n=5) or a treatment (n=5) group. The treatment consisted of a series of IV injections with mouse anti-ovine CD4(+) T lymphocyte monoclonal antibodies for a period of 3 weeks. After the second treatment, all lambs were experimentally infected with 10,000 H. contortus infective larvae by oral inoculation. All lambs were monitored for fecal egg counts, blood packed cell volumes, white blood cell differential counts and serum antibody responses on a weekly basis. Fluorescence-activated cell sorter (FACS) analysis was done biweekly to enumerate CD4(+) T lymphocytes in peripheral blood. Necropsies were performed at the end of the study and 10% of the contents of the gastrointestinal tract were preserved for nematode enumeration and identification. Also at necropsy, mesenteric lymph nodes were extracted and FACS analysis was run on lymphoid cells. Mean fecal egg counts on day 21 and 28 post-infection and nematode counts at necropsy of the treated group were significantly (p<0.05) higher than that of the control group. Percent CD4(+) T lymphocytes in peripheral blood was significantly (p<0.05) lower in the treatment group than in the control group from day 9 to the end of the study. No differences were found in blood packed cell volumes, white blood cell differential counts, antibody titer or lymph node CD4(+) lymphocytes between groups. Lambs depleted of their CD4(+) T lymphocytes were more susceptible to H. contortus infection than undepleted lambs. The results of this study suggest that CD4(+) T lymphocytes are associated with the natural resistance of GCN sheep to H. contortus infection.

Abomasum↗
PubMed1990

Anthelmintic efficacy of febantel paste in naturally infected calves.

The purpose of the present study was to verify results of the lowest dose (5 mg kg-1) of febantel evaluated in an earlier trial in which there were no differences in efficacies of three dose rates (5, 7.5 and 10 mg kg-1 body weight) against natural gastrointestinal nematode infections of cattle. Fourteen Angus calves (mean weight and age of 155 kg and 525 days, respectively), from the same farm, with relatively heavy (mean of 448 eggs g-1 feces (epg] parasite burdens were selected. After an adjustment period of 8 days in drylot, beginning on 25 July, seven calves were treated with a 45.5% paste formulation of febantel. On Day 7 post-treatment, calves were necropsied for determination of residual worms. Rectal fecal samples were obtained prior to adjustment, at treatment, 5 days post-treatment and at necropsy. On both Day 5 post-treatment and at necropsy a mean of less than 1 epg was recovered from treated calves compared with 765 and 1566 epg, respectively, in control calves. Worms counts at necropsy revealed an efficacy of 98.5% against all adult abomasal worms (Haemonchus placei, 100%, P less than 0.02; Trichostrongylus axei, 99.4%, P less than 0.0001; Ostertagia ostertagi, 90.5%, P less than 0.0002). Treatment was 100% efficacious against adult small and large intestinal worms. However, numbers of Bunostomum phlebotomum, O. radiatum and Trichuris spp. recovered in the control calves were too low to enable a reliable test of drug efficacy. Treatment was not effective against either mucosal or luminal fourth stage larvae of abomasal O. ostertagi.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Epidemiological observations on helminth infections of calves in southern Ghana.

This paper describes helminth infections in three groups of calves of different ages grazing naturally infested pastures from March 1987 to May 1988. Calves in which the faecal egg output was followed from birth showed Toxocara vitulorum eggs as early as two days after birth and maximum patency occurred after two months. The fall in Toxocara egg output coincided with a rise in that of the strongylates; Haemonchus spp., Trichostrongylus spp. and Oesophagostumum spp. The influence of rainfall in dictating strongylate nematode infection was clear with high egg output during high rainfall and low egg counts when the rainfall was lower. There was an indication that calves carry the infection from the end of the minor rainy season in November to the beginning of the next rains in March and then contribute to pasture contamination. However, calves born in December may remain uninfected until the onset of the rains.

Animals↗
PubMed2000

An ultrastructural study of sporidium formation during infection of a rhabditid nematode by large gun cells of Haptoglossa heteromorpha.

Recently fired gun cells of Haptoglossa heteromorpha, an aplanosporic nematode parasite, were examined ultrastructurally. The everted tubes of the fired cells had penetrated the cuticle of a nematode, and infective sporidia were developing inside the host body. The nematode cuticle was penetrated by the narrow, walled part of the tube below the needle chamber. The lower unwalled part of the tube tail formed the sporidium. The developing sporidium had a multilayered fibrous outer coating and the plasma membrane was separated from the wall in places. Sporidia contained biphasic membrane-bound vesicles that had been generated by the Golgi dictyosome during gun cell development. Immediately following gun cell firing, the nuclear envelope of the sporidium nucleus was not apparent, and the sporidium nucleus contained clusters of electron-dense particles concentrated in the nucleolar region. We compare the structures and organelles found in the mature gun cell with those in the fired cell and attempt to identify the membranous layers around the sporidium.

Animals↗
PubMedDate not supplied

Rate of reinfection with intestinal nematodes after treatment of children with mebendazole or albendazole in a highly endemic area.

The comparative efficacy of albendazole and mebendazole in the treatment of intestinal nematode infections were compared 3 weeks after treatment in a randomized trial among schoolchildren on Pemba Island, Tanzania. Egg counts were compared 3 weeks, 4 months and 6 months after treatment of 731 children seen on each occasion. Differences in the efficacies were apparent with some nematodes 21 d after treatment, but these were no longer apparent 4 months after treatment, and by 6 months intensities of infection were similar to pre-treatment levels. These findings suggest that treatment of schoolchildren every 4 months may be necessary in this highly endemic area in order to have an impact on the intensity of intestinal nematode infections sufficient to be likely to reduce morbidity.

Albendazole↗
PubMed1999

Immunogenic glycoconjugates implicated in parasitic nematode diseases.

Parasitic nematodes infect billions of people world-wide, often causing chronic infections associated with high morbidity. The greatest interface between the parasite and its host is the cuticle surface, the outer layer of which in many species is covered by a carbohydrate-rich glycocalyx or cuticle surface coat. In addition many nematodes excrete or secrete antigenic glycoconjugates (ES antigens) which can either help to form the glycocalyx or dissipate more extensively into the nematode's environment. The glycocalyx and ES antigens represent the main immunogenic challenge to the host and could therefore be crucial in determining if successful parasitism is established. This review focuses on a few selected model systems where detailed structural data on glycoconjugates have been obtained over the last few years and where this structural information is starting to provide insight into possible molecular functions.

Animals↗