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Results for “NEMATODE INFECTIONS”

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PubMed1993

Strongyloidiasis and other intestinal nematode infections.

In contrast to other helminthic parasites, Strongyloides stercoralis can replicate within humans, causing a chronic persistent infection that can be severe and fatal in compromised hosts. This article reviews new developments to help meet the clinical challenges of this infection, including clinical clues to the diagnosis, new diagnostic methods, including stool culture and serological assays, new drugs such as albendazole and ivermectin, and difficult treatment issues. The other major intestinal nematode parasites, including Ascaris, hookworm, and Trichuris, are extremely common worldwide, but in North America their clinical presentation is often more subtly related to low-grade worm burdens or allergic manifestations. Special consideration is given to difficult management issues, including the patient with unexplained eosinophilia, the pregnant patient, and the patient who passes a worm.

Adult↗
PubMed1991

Gene expression in nematode-infected plant roots.

A major pathogen of potato plants (Solanum tuberosum) is the potato cyst nematode (Globodera spp.), which induces localized redifferentiation of a limited number of host cells to form a specialized feeding-site termed the syncytium. A novel strategy utilizing the polymerase chain reaction (PCR) was employed to construct a cDNA library from dissected potato roots highly enriched in syncytial material. The library was differentially screened with cDNA probes derived from the infected root tissue from a compatible interaction and from healthy root tissue. Characterization of one gene identified by the library screen indicated an expression pattern that correlated with events in the immediate vicinity of the pathogen after syncytial establishment. The strategy for library construction and screening could be applicable to the study of gene expression in any plant-pathogen interaction in which the limited supply of cells at the interface of the two organisms precludes a more traditional approach.

Animals↗
PubMed2006

Predictors and markers of resistance to neurotropic nematode infection in rodent host.

Parasite-mediated selection is currently believed to play an important role in life-history evolution. To assess how simple hematoserological and biochemical condition indices reflect host immunocompetence and infection resistance controlled laboratory experiments are required. We addressed these issues by infecting laboratory rats with the standard dose of embryonated eggs of a neurotropic nematode Toxocara canis. Urine baseline corticosterone concentrations, measured 1 week before infection, predicted the number of nematode larvae later recovered from host brains. Thus, this noninvasive clinical marker appeared useful for assessment of potential infection resistance. Rats who had accumulated high number of larvae in their brains and muscle had large spleens and high peripheral eosinophil counts 17 days postinfection. This finding is consistent with the concept that induction of eosinophilic Th2 type humoral immune response benefits the parasite rather than host. Hence, excessive peripheral eosinophilia and spleen enlargement are not markers of efficient antiparasite response in larval toxocariasis.

Animals↗
PubMed1999

The role of IL-13 in helminth-induced inflammation and protective immunity against nematode infections.

Helminth infections induce the production of type 2 cytokines, which contribute both to expulsion of the worms and inflammatory responses that can either protect or damage the host. Although IL-4 has been considered the most critical cytokine for both inflammation and protective immunity, recent observations indicate that IL-13 - a related cytokine - can have equal or even greater importance than IL-4 in inflammatory responses and host protection against infection.

Animals↗
PubMed1996

Field evaluation of doramectin for treatment of gastrointestinal nematode infections and louse infestations of cattle.

OBJECTIVE: To evaluate the safety and efficacy of doramectin given by injection at a dosage of 200 micrograms/kg of body weight for treatment of gastrointestinal nematodiasis or louse infestations of cattle. ANIMALS: 1,031 mixed-breed cattle were treated in the nematode study and 418 were treated in the louse study. PROCEDURE: Naturally parasitized cattle were given 200 micrograms of doramectin/kg or an equivalent volume of saline solution, SC. In nematode experiments, fecal samples were collected from each animal 1 week before treatment, at time of treatment, and at weekly intervals there after for 3 weeks. In louse experiments, louse counts were carried out for each animal on the day of treatment and 14 and 28 days later. All cattle were weighted at the time of treatment and at the end of the experiment. RESULTS: By 21 days after doramectin treatment, fecal egg counts had decreased to zero in 9 of 10 experiments and to 1 egg/g in the remaining experiment. Differences between treatment groups were significant (P < 0.0001) in all instances. Pretreatment coproculture identified Haemonchus, Ostertagia, Cooperia, Trichostrongylus, and Nematrodirus as the represented genera. Doramectin was 100% effective in eliminating infestation with Linogna thus vituli, Haematopinus eurysternus, and Solenopotes capillatus. Infestation with the chewing louse Damalinia bovis was reduced overall by 86%. For all species, post treatment louse counts were significantly (P < 0.02) less for doramectin-treated cattle than for controls. Adverse reactions to doramectin were not apparent in either study. CONCLUSION AND CLINICAL RELEVANCE: Injectable doramectin at a dosage of 200 micrograms/kg is safe and effective for treatment of gastrointestinal nematodiasis and louse infestations of cattle under field conditions.

Animals↗
PubMed1997

Epidemiological observations on gastrointestinal nematode infections in grazing cow-calf pairs in Belgium.

The epidemiology of gastrointestinal helminth infections in beef cows and calves on pasture was studied in Belgium during the 1990 and 1992 grazing seasons. Weight gain, faecal egg counts, generic differentiation of infective larvae, serum pepsinogen levels, herbage larval counts and worm burdens of tracer calves were used as parameters. In Study 1 two groups of ten cows with their spring-born calves grazing on separate pastures (A and B) were monitored during the 1990 grazing season. Ostertagia ostertagi was the predominant species shed by cows and calves. Cows on Pasture A had significantly higher egg counts at turn-out than the B cows, creating a high pasture contamination in the autumn, evidenced by high Ostertagia worm burdens in the Pasture A tracer calves. Calves of both groups showed low egg counts (mean < 60 eggs g-1 faeces, EPG) throughout the grazing season. In Study 2 nine cow-calf pairs were monitored during the 1992 grazing season. The calves were born in winter or spring. Faecal egg counts of the cows remained low throughout the trial period. During the grazing season high egg counts were observed in the calves (mean up to 778 EPG). Cooperia oncophora was the predominant species in the calves. In the cows O. ostertagi, Oesophagostomum, C. oncophora and Trichostrongylus axei were present. It is suggested that, in the first study, the cows were the major source of pasture contamination, while in the second study the winter-born calves, being older and having a higher herbage intake resulting in a higher infection level, were largely responsible for the high Cooperia pasture infection level at housing.

Animals↗
PubMed2000

Animal models of intestinal nematode infections of humans.

In this paper we discuss several established and potential animal models for human parasitic infection, with a focus on rodent, pig and primate models and the nematodes Ascaris, Trichuris and Toxocara spp. Firstly, we discuss the relevance of choosing a suitable animal host to fit the particular study hypothesis, and the interaction between mathematical modelling and animal models. Secondly, we review the use of animal models for the study of nutrition-parasite interaction, evaluation of treatment and control strategies, and bacteria-parasite interactions. We show that rodent, pig and primate models are all very useful in parasitological research, and that each model has its limitations. However, based on recent experience with the pig-Ascaris and pig-Trichuris models, a more extensive use of the pig-parasite model is advocated, especially for the study of the interaction between human malnutrition and helminth infection, and congenital helminth infection.

Animals↗
PubMed1989

Aspects of the epidemiology of nematode infections in a cow-calf herd in Ontario.

On May 29, 1980, 108 cows and calves were placed on a 20 hectare pasture until October 26, except that from September 18 to October 2 they were in a barn. Every two weeks during the total period, fecal samples were taken from 17 cows and 14 calves and herbage samples were collected from the pasture. Parasite fecal egg counts were estimated using the Cornell-Wisconsin centrifugation technique and herbage infective larvae by a modified Sandwich technique. Daily maximum and minimum air temperature and precipitation were recorded. The principal parasite egg found was the trichostrongyle-strongyle morulate, oval-shaped egg referred to as a gastrointestinal nematode (GIN) egg. The mean GIN egg/g of feces for cows varied from 14.2 to 23.9 and for calves it rose from 0.2 in the spring to 134.8 in the fall. Nematodirus, Trichuris, Strongyloides, Moniezia and coccidia were also found. Larvae were recovered first in July, with the greatest number, over 2000/kg of dry weight of herbage, in September and were primarily Cooperia and Ostertagia.

Animals↗
PubMed2005

Effects of jasmonate-induced defenses on root-knot nematode infection of resistant and susceptible tomato cultivars.

Jasmonates, such as jasmonic acid (JA), are plant-signaling compounds that trigger induced resistance against certain pathogens and a broad range of arthropod herbivores. One goal of this study was to determine the effects of JA-dependent defenses in tomato on root-knot nematodes. Another was to determine if the artificial induction of these defenses could enhance nematode control on plants that carry Mi-1.2, a nematode resistance gene that is present in many tomato cultivars. At moderate soil temperatures, Mi-1.2 can effectively suppress reproduction of most isolates of the common root-knot nematode species Meloidogyne javanica, M. incognita, and M. arenaria. Mi-mediated resistance has its limitations, however. Mi-1.2 is reported to lose its effectiveness at soil temperatures above 28 degrees C, and certain virulent nematode isolates can overcome resistance even at moderate soil temperatures. This study used a foliar application of JA to activate induced resistance in two near-isogenic lines of tomato (Lycopersicon esculentum) with and without Mi-1.2, and evaluated the effects of induced resistance at moderate soil temperatures on one avirulent nematode isolate (M. javanica isolate VW4) and two virulent isolates (M. javanica isolate VW5 and M. incognita isolate 557R). In addition, the effects of induced resistance on avirulent nematode performance were examined at a high temperature (32 degrees C). The results indicate that JA application induces a systemic defense response that reduces avirulent nematode reproduction on susceptible tomato plants. Furthermore, JA-dependent defenses proved to be heat-stable, whereas the effects of Mi-mediated resistance were reduced but not eliminated at 32 degrees C. JA treatment enhanced Mi-mediated resistance at high temperature, but did not suppress either of the virulent nematode isolates tested.

Animals↗