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At least 235 records · Page 13Linked to original sources

PubMed1999

Parasite diversity and anthelmintic resistance in two herds of horses.

Diversity of parasite populations was compared between two herds of horses, one a regularly treated herd the other a feral herd which has bad no anthelmintic treatment for at least 25 years. Eggs obtained from fecal samples of both herds were tested for anthelmintic resistance by use of an in-vitro larval hatch/development assay (LDA), DrenchRite. A fecal egg reduction test was also performed with the domesticated herd using fenbendazole, pyrantel pamoate and ivermectin. Cyathostomes were the predominant group of worms present in both herds. Trichostrongylus axei was seen in both herds, but Strongylus equinus, Strongylus vulgaris, Gyalocephalus capitatus, Poteriostomum spp. and Strongyloides westeri were only found in the feral horses. Larvae of Strongylus edentatus were found in a single domesticated horse. Fecal egg reduction tests with the domesticated herd showed a 32% egg count reduction for fenbendazole, a 93% reduction with pyrantel, and a 99% reduction with ivermectin. From the LDA, anthelmintic resistance was evaluated by determining the resistance ratio of the domesticated herd compared with the feral herd. For benzimidazoles in the domesticated herd, 45% of the cyathostome population was 9.4 times more tolerant than the feral herd's parasite population. The parasite population in the domesticated herd was 1.5 times more tolerant to Levamisole, and 1.7 times more tolerant to the benzimidazole/levamisole combination than the parasite population within the feral herd. 9% of the parasite population in the domesticated herd was 90 times more tolerant to avermectins than the feral herd's parasite population, even though a subpopulation of worms in the feral herd were tolerant to low concentrations of avermectins despite never being previously exposed to this class of anthelmintic.

Animals↗

PubMed1999

An experimental evaluation of methods used to enumerate mucosal cyathostome larvae in ponies.

With the increased interest in equine cyathostomes it has become apparent that some evaluations of methods currently used to count the various larval stages which occur in the mucosa would be beneficial. Experiments were conducted to investigate the effects of fixation and storage of mucosal tissues at -20 C on the accuracy of counting these larvae. The accuracy of counting developing larvae within the mucosa by transmural illumination (TMI) and by artificial digestion (DIG) of the mucosa was also compared. The data indicate that fixation of digested mucosa in PBS-buffered 5% or 10% formalin did not effect the enumeration of either early hypobiotic L3 or larger developing L3 or L4. Although not optimal, counting these larvae by either TMI of DIG after freezing did not significantly differ from counts made on fresh tissues. Significant differences were also not seen between counts of developing larvae made by TMI or DIG. Because DIG must be used to count EL3 and small developing L3, it is possible that TMI is not necessary in heavily infected equids.

Animals↗

PubMed1999

Interactions between dietary fibre, endo-parasites and Lawsonia intracellularis bacteria in grower-finisher pigs.

Samples of faeces and feed were collected from grower and finisher pigs kept on 25 commercial breeder-finisher units in the West-Midlands region of England. Faecal samples were examined for parasite eggs (Ascaris suis, Trichuris suum and strongylid species) using faecal flotation; and for Lawsonia intracellularis bacteria using the polymerase chain reaction. Feed samples were subjected to proximate analysis for energy, protein and fibre content and enzymic colorimetry for levels of non-starch polysaccharides (NSPs). Characteristics relating to housing, feeding and dung disposal systems and husbandry practices were recorded for each farm and assessed for their association with the presence of parasites and L. intracellularis at the herd level. Ascaris eggs were identified in 8% of herds, Trichuris eggs in 20% of herds and in strongylid eggs (Oesophogostomum and/or Hyostrongylus) in 44% of herds. Lawsonia intracellularis was detected in 15% of herds investigated. Herds positive for Trichuris and Ascaris had significantly lower levels of digestible energy and higher levels of neutral detergent fibre, total and insoluble NSPs in their diets than negative herds (p < 0.05). Housing weaners on slatted floors was associated with a significant decreased risk of parasite infection in grower-finishers (odds ratio = 0.09, p = 0.04) compared to housing on solid floors. The use of grower diets high in NSPs was associated with an increased risk of Trichuris infection (odds ratio = 27.6, p = 0.007). There was also an association at the herd level between infection with L. intracellularis and the presence of Trichuris eggs (odds ratio = 17.43, p = 0.069). It is concluded that control of dietary fibre intake (NSPs in particular) for growers and environmental hygiene (dung removal) for weaners appear to be the most important factors controlling parasite infection in grower-finisher pigs in the UK at present. The current move towards more straw based systems is thus likely to exacerbate the influence of these factors and is likely to result in increased parasite infection in grower-finisher pigs in the UK.

Animal Feed↗

PubMed2000

Seasonal development and survival of equine cyathostome larvae on pasture in south Louisiana.

Cyathostome development and survival on pasture in subtropical climates of the US have yet to be completely defined and available data on seasonal transmission are minimal. In an attempt to study this phenomenon, a group of pony mares and their foals was maintained on a naturally contaminated pasture in southern Louisiana. Fecal egg counts (FEC) and numbers of infective third stage larvae (L3) kg(-1) dry herbage were recorded biweekly during two time periods, from January 1986 through December 1988, and September 1996 through October 1997. A FEC rise occurred during the late summer-early autumn which preceded the peak of L3 on pasture during the winter season. The numbers of cyathostome L3 were reduced during the hottest months of the year due mainly to daily minimum temperatures above 18 degrees C, and in winter during short freezing spells when daily minimum temperatures dropped below 0 degrees C. Tilling of the pasture reduced the number of cyathostome L3 during the early winter months but this is an efficacious measure only if horses are given an effective anthelmintic treatment prior to being returned to pasture. The data collected suggest that parasite reduction in southern Louisiana is possible using a treatment program with treatment beginning at the end of September and continuing through the end of March.

Animals↗

PubMed2000

Parenterally administered gastrointestinal nematode infective larvae viable after more than 15 years in liquid nitrogen.

After cryopreservation for 13.3-15.8 years, the viability of the infective larvae (L3) of Trichostrongylus axei, T. colubriformis, Oesophagostomum columbianum, Haemonchus contortus, Ostertagia circumcincta, T. falculatus, Nematodirus spathiger, Chabertia ovina and Dictyocaulus filaria was assessed in sheep, by being deposited at their predilection sites. D. filaria was, however, an exception, in that the L3 were injected into the jugular vein. The mean development of all the species was 22.8%, but if three species (O. columbianum, C. ovina and D. filaria), that developed poorly are disregarded, then the mean development was 33.4%, similar to previous tests after shorter periods of cryopreservation. The L3 of some of the species appeared sluggish when examined 10-15 min after being thawed, and in the case of H. contortus practically all the larvae of the original batch tested in the previous trials of the series appeared dead when thawed for use in the present trial, and were replaced by another batch of L3 of the same species. When re-examined after about 8 h, however, a high percentage of the L3 of the original batch appeared to have become revitalised, and their viability was tested in a trial reported elsewhere. The intestinal cells of the majority of the L3 of N. spathiger, O. circumcincta and C. ovina were vesiculated when they were thawed. Nevertheless, the degree of development of the former two species was of the highest in the trial, and it can be concluded that this phenomenon does not necessarily impede the viability of larvae.

Animals↗

PubMed1986

Small strongyles. Recent advances.

The recent increased interest in cyathostomes can be traced to simplification of their taxonomy, improved knowledge of pathogenicity, and failures of practical control due to anthelmintic resistance. Cyathostome ova develop to infective third-stage larvae (L3) at a rate that is directly proportional to environmental temperature. Equine feces serve as a reservoir for L3, which are liberated by moderate amounts of rainfall. Third-stage larvae persist for longer periods at low temperatures, easily surviving over-winter on pastures to provide a source of infection during the following grazing season. Third-stage larvae exsheath within the host and enter the mucosa and submucosa of the cecum and large colon. Larvae develop within mucosal cysts, molt to the fourth stage, and may persist within the tissues for up to 2 1/2 years. Larvae ultimately emerge from the mucosa to become adults in the lumen. Adult populations are replenished by recently ingested larvae and by immature worms newly emerged from arrested development. The magnitude of larval and adult populations within the host displays seasonal variations, with peak numbers occurring in early spring and autumn in the United States. In typical natural infections, a small number of species comprise the majority of the cyathostome populations. Cyathostome infection may result in anorexia, weight loss, diarrhea, colic, and death. Cyathostome ova are easily detected in feces, but ova may not be present during larval cyathostomiasis. Increased concentrations of beta-globulins, hypoalbuminemia, anemia, and leukocytosis occur inconsistently. Two major problems in the treatment of cyathostome infections are anthelmintic resistance and the insusceptibility of encysted larvae to recommended dosages of most anthelmintics. The major goal of cyathostome control is prevention of environmental contamination with nematode ova. Host resistance appears to protect against cyathostome disease rather than cyathostome infection, and one manifestation of this resistance appears to be prolongation of the prepatent period.

Animals↗

PubMed2003

First complete large subunit ribosomal RNA sequence and secondary structure for a parasitic nematode: phylogenetic and diagnostic implications.

The complete sequence and secondary structure of the large subunit of nuclear ribosomal RNA(LSUrRNA) were determined for the parasitic nematode Labiostrongylus bipapillosus (order Strongylida). Its LSU rRNA sequence was shorter (by 18 bp) than that of the free-living nematode, Caenorhabditis elegans (order Rhabditida), the only other species within the Nematoda for which a complete LSU rRNA sequence has been determined. Interspecific differences in sequence were greater in the 12 D domains compared with the core segments, with the secondary structure being maintained by partial or complete compensatory base pair changes. The magnitude of interspecific sequence difference in each D domain (except for D6 and D12) was similar, suggesting that several domains contain informative genetic markers for phylogenetic studies of the phylum Nematoda at different taxonomic levels. The LSU rRNA may also provide species-specific markers for the identification of some bursate nematodes of veterinary and medical importance.

Animals↗

PubMed1986

Inorganic elements in adult Ternidens deminutus (Nematoda: Strongylidae: Oesophagostominae) from humans and baboons.

The present paper presents the results of an analysis of the inorganic elements detected in Ternidens deminutus from human and baboon hosts. It reports on the presence of Zn, Fe, P, Ca, Cu, Mg, Mn and K in the worms and notes especially that worms from humans contained a higher percentage of body weight of Zn than those from baboons, a finding in agreement with an earlier EDAX analysis of the pigment granules of this species.

Animals↗

PubMed1989

Mammomonogamus laryngeus (Railliet, 1899) infections in cattle from Sri Lanka.

During one year 1249 male cattle were examined for Mammomonogamus laryngeus infections in the slaughterhouse at Kandy, Sri Lanka. The overall prevalence was 40% with only light monthly variations (34 to 52%). The infection rate was highest (47%) in 2 to 2.5 year old animals. In infected animals an average of 6.4 parasite pairs was found with higher numbers in older animals. The majority of worms were located on the posterior side of the epiglottis. Lesions observed were mucosal plugs at the site where the parasites were attached to the mucosa and moderate to severe erosions and ulcers in other zones.

Age Factors↗

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↗

PubMed1973