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At least 19 recordsLinked to original sources
PubMed1986

A method for the interpretation of parasite egg counts in faeces of sheep.

A new method for the interpretation of strongyloid egg counts in faeces in sheep flocks is proposed. The "Flock Parasitism Index" (FPI) is based on three epizootiological concepts: extent of parasitism, distribution of its intensity, and risk of pasture contamination by eggs. In the estimation of FPI from a number of faecal samples from different animals in a flock, the percentage of parasitized sheep and the distribution of parasitized animals of the sample into the classical categories of "low", "moderate" and "high" from the number of eggs per gram of faeces (EPG) and the arithmetic mean of EPG of the sample are considered. The pathogenic and epizootiological importance of each one of the "low", "moderate" and "high" categories are considered to be 0.1, 0.5 and 1, respectively. From the relationship between EPG and worm burdens, probabilities for "low", "moderate" and "high" distributions are calculated, and from the percentages of worm burdens estimated and their levels of confidence at 95% it is suggested that values of FPI equal to 2.0 must be considered as the limit of parasitism where economic losses are tolerable.

Animals↗
PubMed1983

Genetic control of liability to infection with Nematospiroides dubius in mice: direct and correlated responses to selection of mice for faecal parasite egg count.

Mice selected as liable (L) and refractory (R) over 10 generations voided significantly more and less Nematospiroides dubius eggs compared with randomly mated (Rd) mice after primary infection with 100 larvae. Strong positive correlation was found between the numbers of N. dubius eggs in mouse faeces and the numbers of adult N. dubius recovered from mice culled from the R, Rd and L colonies. Selection limit based on a faecal e.p.g. was reached in the L mice after 9 generations whereas the faecal N. dubius e.p.g. voided by the R mice continued to decline throughout selection. In contrast, no change in worm numbers was found in L or R mice after 6 generations. The refractory state of the trait, liability to infection with N. dubius, was inherited as a dominant character with a realized heritability value of approximately 0.2. Differential correlated responses from N. dubius infectivity compared with N. dubius fecundity and growth indicated murine genetic control of this trait by 2 major genetic units. In general, there were negative phenotypic and genetic correlations between the faecal N. dubius e.p.g. of mice and murine morphological conformation, but positive correlations between the faecal N. dubius e.p.g. of selected mice and establishment, growth and fecundity of N. dubius populations in these mice. There was little correlation between the faecal N. dubius e.p.g. after primary infection and anti-N. dubius antibody titres and parasite female/male sex-ratio.

Animals↗
PubMed1987

Necator americanus in neonatally infected hamsters. The time-course of infection and antibody response to the surface antigens of L4 and adult worms.

Neonatal hamsters were infected with a hamster-adapted strain of Necator americanus, and the time-course of infection was followed by worm and faecal egg counts. Parasite eggs were first recorded during the 6th week of infection, increasing rapidly thereafter to peak in weeks 7-10. Male hamsters excreted more eggs than females, but both sexes were equally susceptible to infection and harboured comparable worm burdens. Faecal egg counts declined from week 10 onwards and this was associated with a loss of worms from animals with heavy infections. Low level infections were stable over the first 114 d of infection but worm fecundity nevertheless still declined over this period. Both hamster sexes responded similarly to surface antigens on adult worms, the antibody levels rising from week 5 onwards to reach a plateau in weeks 6-7, which persisted until the experiments were terminated. The major antigens recognised on the surface of adult worms had molecular masses corresponding to 25 kDa, 32 kDa, a doublet with the heaviest polypeptide resolving at 46 kDa, and a triplet with the heaviest at 67 and 93kDa. In contrast L4 had only 2 major cuticular antigens resolving at 41 and 93kDa. The 93kDa molecule on L4 and adult worms may be antigenically related.

Animals↗
PubMed1982

Genetic control of resistance to infection with Nematospiroides dubius in mice: selection of high and low immune responder populations of mice.

F1, Quackenbush (Q) x Wild (W) Mus musculus were assayed and selected for their level of immunity to secondary infections with 100 Nematospiroides dubius using faecal parasite egg counts. A significant positive linear correlation was found between the number of parasite eggs voided in the faeces and the number of N. dubius recovered after secondary infections in mice. Selection for immunity was not influenced by the conformation of the mice. High (H) and low (L) responder colonies together with a randomly (Rd) bred colony of mice were established over 5 generations. Adaptive immunity was more efficacious in protecting female than male mice and appeared to be controlled by a few dominant genes; the heritability (h2) of the trait was estimated at 0.56 for the parental stock and 0.55 for the F5 Rd colony and the realized heritability was 0.49. Higher anti-N. dubius antibody titres were detected in H than L mice. H mice harboured fewer and less fecund parasites than Rd colony mice; L mice had more worms with greater fecundities than Rd mice. The levels of primary infections in H and L mice related to the levels developed after secondary infection from F4. This suggested at least partial linkage of genes controlling innate with genes controlling adaptive immunity against N. dubius.

Animals↗
PubMed1997

Production responses following strategic parasite control in a beef cow/calf herd.

Strategic parasite control has been reported to improve performance in a beef cow/calf herd that does not demonstrate clinical parasitism. This study was conducted to determine if strategic anthelmintic treatment at turnout and at midsummer would improve growth and reproduction. Two cow/calf groups of similar composition were grazed on separate, but equivalent pastures in the spring, and at midsummer, they were moved to new pastures. The treated group was given fenbendazole at tumout (cows) and at midsummer (cows and calves). The control group was not treated. The study was repeated in the following year. Across both years of the study, parasite egg counts were substantially reduced in both the treated cows (P < 0.005) and treated calves (P < 0.0001). The calves in the treated group significantly (P < 0.0001) outgained the control calves in both years of the study by 19.3 kg and 13.2 kg, respectively. Average daily gain (ADG) after adjusting for birth weight and birth date for treated calves was 0.13 kg greater than for control calves (0.83 vs 0.70) for the 2-year study (P < 0.0001) There was also a significant (P = 0.0357) increase in the reproductive performance of the cows. The pregnancy rate averaged across years was 94% for the treated cows compared to 82% for the control animals.

Animals↗
PubMed1980

Opisthorchis viverrini: partial success in adoptively transferring immunity with spleen cells and serum in the hamster.

Three groups of golden Syrian hamsters received intraperitoneally either, (1) 1 x 10(7) spleen cells, (2) 0.5 ml. serum or, (3) 1 x 10(7) spleen cells plus 0.5 ml. serum, from donors infected 6 weeks previously with 25 Opisthorchis viverrini metacercariae, one day before and at the same time as challenge with 25 metacercariae. Three groups of control animals received the same quantities of spleen cells, serum or an admixture of both from normal non-infected donors in the same manner followed by challenge with 25 metacercariae. Animals were killed six weeks after challenge, livers and extrahepatic biliary systems carefully removed, and liver worm burdens estimated. Additionally, parasitic egg counts were performed on pooled faeces samples collected one hour prior to death. Animals receiving spleen cells, serum, or an admixture of both, from normal non-infected donors had mean worm burdens of 11.44, 12.00 and 12.66, respectively. Animals receiving spleen cells, serum, or both, from infected donors had mean worm burdens of 9.88, 7.77 and 12.00, respectively. There were no significant differences in mean worm burdens between control and experimental groups. However, a substantial reduction in parasitic faecal egg counts and subsequently mean egg production per worm was observed in all 3 groups of animals receiving spleen cells, serum, or both, from infected donors when compared to their respective control groups. These findings are discussed in relation to adoptive transfer studies performed with other helminths and their possible relevance to naturally acquired immunity is commented on.

Animals↗
PubMed1985

Field efficacy of a morantel sustained release bolus for control of gastrointestinal nematodes in yearling steers.

The efficacy of a morantel sustained release bolus (MSRB) for control of gastrointestinal nematodes in yearling steers was evaluated over a 6-month grazing period commencing on 26 March 1982. Three groups of 15 steers were allotted to the following treatments: Group 1 -- one MSRB at start of trial; Group 2 -- one therapeutic dose of thiabendazole at start of trial; Group 3 -- untreated control. The treatment groups were grazed separately. Parasite egg counts (EPG), herbage larval counts, pepsinogen levels and weight gains were monitored. Every other month, sets of 2 parasite-free tracer calves were placed in the pasture grazed by each treatment group and allowed to graze for 3 weeks before being subsequently necropsied for worm counts. At the end of the trial, 6 animals from each group were also necropsied for worm counts. The MSRB treatment resulted in significantly lower egg counts, fewer infective larvae on pasture, lower pepsinogen levels and lower worm burdens in tracer calves than was the case for the untreated group, but generally the levels were not significantly different from those associated with the thiabendazole treatment. The mean weight gain for the MSRB treated steers showed a significant advantage (70.9 lb) over the untreated animals, but was not significantly different from those which received thiabendazole. Total worm counts at the end of the trial were not different from any treatment group.

Abomasum↗
PubMed2005

The therapeutic effect of the neuropeptide hormone somatostatin on Schistosoma mansoni caused liver fibrosis.

BACKGROUND: The neuropeptide somatostatin is one of the major regulatory peptides in the central nervous system and the digestive tract. Our recent work has delineated an association between fibrosis and low levels of endogenous somatostatin plasma levels in Schistosoma mansoni infected subjects. Based on these results this paper explores the therapeutic potential of somatostatin in a mouse model of hepatic fibrosis associated with S. mansoni infections. METHODS: Groups of outbred Swiss mice were infected with 100 S. mansoni cercariae, infection maintained till weeks 10 or 14, and then somatostatin therapy delivered in two regimens -- either a one or a two-day treatment. All animals were sacrificed one week after therapy and controlled for liver, spleen and total body weight. Circulating somatostatin levels in mice plasma were measured at the time of sacrifice by means of a radio-immuno assay. GraphPad Prism was used for statistical calculations. RESULTS: Somatostatin administration showed little toxicity, probably due to its short half-life. Total liver and spleen weights of S. mansoni infected animals increased over time, with no changes observed due to somatostatin therapy. Total body weights were decreased after infection but were not affected by somatostatin therapy. Snap frozen liver sections were stained with haematoxylin-eosin or Masson's trichrome to study parasite count, hepatocyte status, granuloma size and cellularity. After somatostatin treatment mean egg counts per liver section (43.76 +/- 3.56) were significantly reduced as compared to the egg counts in untreated mice after 10 weeks of infection (56.01 +/- 3.34) (P = 0.03). Similar significant reduction in parasite egg counts were also observed after somatostatin treatment at 14 weeks of infection (56.62 +/- 3.02) as compared to untreated animals (69.82 +/- 2.77)(P = 0.006). Fibrosis was assessed from the spectrophotometric determination of tissue hydroxyproline. Infection with S. mansoni caused increased hydroxyproline levels (9.37 +/- 0.63 micromol at wk 10; 9.65 +/- 0.96 micromol at wk 14) as compared to uninfected animals (1.06 +/- 0.10 micromol). This significant increase in collagen content (P = 0.01; 0.007 respectively) marks the fibrosis observed at these time points. Treatment with somatostatin resulted in a significant decrease in hydroxyproline levels both at wk 10 (4.76 +/- 0.58 micromol) and at wk 14 (5.8 +/- 1.13 micromol) (P = 0.01; 0.03 respectively). Endogenous somatostatin levels were increased at wk 10 (297 +/- 37.24 pg/ml) and wk 14 (206 +/- 13.30 pg/ml) of infection as compared to uninfected mice (119 +/- 11.99 pg/ml) (P = 0.01; 0.008 respectively). Circulating somatostatin levels in infected animals were not significantly affected by somatostatin treatment. Hepatocyte status remained unaltered and granulomas were not remarkably changed in size or cellularity. CONCLUSION: Our experiments reveal an antifibrotic effect of somatostatin in schistosomiasis. We have previously shown that the somatostatin receptors SSTR2 and SSTR3 are present on the parasite egg and worms. We therefore hypothesize that somatostatin reduces either the number of parasite eggs or the secretion of fibrosis inducing-mediators. Our data suggest somatostatin may have therapeutic potential in S. mansoni mediated liver pathology.

Animals↗
PubMed1990

Use of albendazole in feed to control Fascioloides magna infections in captive white-tailed deer (Odocoileus virginianus).

Thirty-six adult white-tailed deer (Odocoileus virginianus) naturally infected with Fascioloides magna were captured and randomly assigned to four groups. Each group was fed pelleted feed coated with albendazole for each of seven consecutive days to deliver the drug at a dose rate of approximately 0.0, 5.0, 8.5, or 16.5 mg/kg bodyweight/day. At 7 wk posttreatment, each animal was euthanized and necropsied. Effects of albendazole treatment included significant reduction (P less than 0.05) in parasite egg count per gram of feces and increase in serum albumin concentration (P less than 0.05). Smaller parasites or remains of dead parasites were seen at the end of migratory tracks in the treated groups. Efficacy of the drug was 82 to 84%.

Administration, Oral↗
PubMed1999

The response of Nigerian West African Dwarf goats to experimental infections with Haemonchus contortus.

One option for controlling haemonchosis in warm pastoral regions is improvement of resistance by selective breeding. Variation in acquired immunity to H. contortus and immunological correlates of infection were studied in West African Dwarf (WAD) goats. Following exposure to 5000 L3, 63 per cent of the inoculum established but 77 per cent of established worms were expelled by week 5. All infected animals were anaemic (day 14). When exposed to 2000L3, 36 per cent of the inoculum was still present (day 35) with no loss by day 49. Persisting primary infection worms survived a superimposed challenge (day 35), but their growth was slowed and resistance to challenge was significant. Most goats showed eosinophilia and parasite-specific IgG responses to primary infection, but only eosinophilia increased after challenge. No consistent associations were found between parasite burden and any immunological measures of infection, but parasite egg counts showed considerable variation. Overall, our results suggest that resistant genotypes exist among the WAD goat population.

Animals↗
PubMed1988

Importance of diagnostic aspects in ostertagism.

Diagnostic methods which reveal only the presence or absence of Ostertagia in grazing animals are of little importance since all will acquire some degree of infection when grazed in the temperate regions of the world. Ostertagia infections may be (1) light--no disease or performance losses occur; (2) moderate--disease may or may not be overtly visible but performance losses occur or (3) heavy--disease is overt with or without death loss. The differentiation of these levels of infection is a quantitative matter insofar as the number of parasites correlates with the degree of pathology and is much less certain than is the presence or absence of infection. Historically, the quantitative parasite egg count in feces (eggs per gram (e.p.g.)), combined with the usual subjective and objective information obtained in clinical examinations has been the procedure used to obtain a quantitative estimate of the level of infection. More recently, the use of plasma pepsinogen levels as an indication of gastric pathology has been adopted by some laboratories. Neither of these methods have met with the desired level of accuracy, but they do have considerable value when their limitations are recognized. In the present era of emphasis on epidemiologically based control programs we are faced with yet another aspect of diagnosis, namely that of a quantitative estimate of numbers of infective stages (L3) on herbage. Methods to assess the number of L3 on forage are not satisfactory for routine clinical use. This paper evaluates the primary objectives of diagnosis as applied to the herd and flock. It briefly evaluates current methodology insofar as the diagnosis of parasitic gastroenteritis is concerned. The use of e.p.g. counts in clinical practice is discussed. Examples applicable to herds of weaner and stocker cattle are presented.

Animals↗
PubMed1982

Multiple infections with Nematospiroides dubius in mice selected for liability to a single infection.

The faecal egg counts and worm burdens of mice selected over 7 generations as refractory (R), random (Rd) or liable (L) to primary infection with Nematospiroides dubius were significantly different, but the antibody titres (generation 8 mice) after 21 days infection were similar, demonstrating that selection had separated populations of mice which differed in their innate immunity. Variations in adaptive immunity were also shown between the three colonies in terms of protection after challenge infections, self-cure reactions, humoral antibody titres and ability of immune serum from R, Rd and L donors to passively protect recipient Quackenbush (Q) strain mice. R mice were more refractory to primary infection and more proficient in acquiring protective levels of adaptive immunity than L colony mice. Correlation of the faecal parasite egg count after primary with that after secondary infection supported the conclusion that the genetic control of liability to primary infection and of the adaptive immune response following challenge infections were at least partially linked.

Animals↗
PubMed1986

Nematospiroides dubius: direct and correlated responses to selection for high and low immune responsiveness in mice.

High and low immune responder lines of mice were bred selectively from an allogeneic stock over 10 generations, based on their fecal parasite egg count assayed 3 weeks after reinfection with 100 Nematospiroides dubius larvae. By generation 10, (F10), the low immune response mice voided about 10 times as many fecal N. dubius eggs as the high immune response mice. Realized heritability for the selected trait, fecal egg count after secondary infection (= protective immunity), was 0.35 at F7. F7 was considered the selection limit. Selection for change in fecal egg count did not significantly influence the conformational nor reproductive characteristics of these mice. Significant phenotypic and genetic correlations were evident between the selected character and innate immunity to N. dubius, humoral antibody response to N. dubius infection, and establishment, growth, and reproduction of N. dubius in the selected mice.

Animals↗
PubMed1987

Evaluation of the parasitological and production responses of a cow/calf operation to an anthelmintic program with ivermectin.

The efficacy of a treatment schedule using ivermectin, given subcutaneously at the rate of 200 micrograms kg-1, to control gastrointestinal parasitism and its effect on liveweight gains was assessed. Two herds with a total of 466 Hereford X Brangus cow/calf pairs were used. Each herd was on six pasture plots of comparable size, stocking rate, and quality and quantity of forage. Pasture groups were paired across the two herds. Pasture groups from one herd were randomly assigned to nonmedicated control and the other three to ivermectin treatment. Treatment assignments per pasture group were reversed in the other herd. The control group contained 118 cows and 112 calves and the medicated group 121 cows and 115 calves. Cows were treated in early July and the calves in late July or early August. Cattle from one herd were weighed on Days -28, 0 (day of cow treatment), 30 (day of calf treatment), 58, and 86, while the other herd was weighed on Days -29, 0 (day of cow treatment), 27 (day of calf treatment), 61, and 89. Day 0 was not the same calendar day for the two herds. Fecal samples for parasite egg counts were obtained from the rectum on weight days from five cows and six calves from each pasture; in most cases the same cattle were sampled each time. Calves treated with ivermectin gained (P less than 0.05) more weight than control calves between day of treatment for cows and the end of the trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Effect of stocking rate, grazing system, and fenbendazole treatment on subclinical parasitism in dairy heifers.

Average daily weight and fecal parasitic egg count were compared among sixty 7- to 15-month-old Holstein heifers randomly assigned to 8 groups. The following variables were examined: grazing system (continuous vs rotational), stocking rate (3.5 vs 5 heifers/ha), and treatment [control vs dosing with a 10% suspension of fenbendazole (5 mg/kg of body weight) given orally 21 and 49 days after heifers were placed on pasture]. Two heifers from each group were euthanatized 4 weeks after the completion of the 148-day trial to determine the number of parasitic larvae and adults in the abomasum and intestine. Heifers treated with fenbendazole had significantly (P less than 0.001) fewer fecal ova and fewer inhibited abomasal larvae (P less than 0.05) than did controls. Mean total weight gain and mean daily rate of gain of fenbendazole-dosed heifers were significantly (P less than 0.01) increased by 17.3 kg or 0.12 kg/day, respectively, compared with those of nontreated heifers. Seemingly, stocking rate and grazing systems had no marked effect on subclinical parasitism in heifers.

Animal Husbandry↗
PubMed1991

Epizootiology of helminth parasitism in a beef cow/calf herd in Minnesota.

To test the effect of a parasite control program for cattle, 2 groups of similar composition were grazed on separate, but equivalent, improved pastures. Cattle in 1 group were treated with fenbendazole at 5.0 mg/kg of body weight at the time they were turned out on pasture in the spring and again at midsummer, when the cattle were moved to a new pasture. The control group was not treated. Parasite egg counts were significantly (P less than 0.04) lower in the treated group. Trichostrongyle-type eggs were the most prevalent throughout the year, except in the month of May, when Strongyloides papillosus eggs were predominant. The number of worms recovered from tracer calves was lower for those on pastures where the treated group grazed than for those on the control group's pasture. The most consistently recovered parasite was Ostertagia ostertagi, and hypobiosis was observed.

Animals↗
PubMed1996

Prevalence and epidemiology of trichostrongylids in Wyoming cattle with consideration of the inhibited development of Ostertagia ostertagi.

During 1988, monthly collections of abomasa and the cranial portion of the small intestine of 208 native Wyoming cattle were examined for adult and larval helminth parasites. Egg counts were performed on colonic faecal specimens. The animals ranged from 7 months to 8 years of age and were sampled at slaughter houses or diagnostic laboratories from five different counties in the State. Most of the cattle had ranged for a long time on non-irrigated, high altitude grass plains from about 1250 to 2500 m above sea level. All animals examined were found infected. Nematode genera (and number of species) found included Ostertagia (4), Trichostrongylus (2), Haemonchus (1), Cooperia (4) and Nematodirus (2). One trematode, Fasciola hepatica, and a cestode, Moniezia benedeni, also were found. Trichostrongylus axei, Trichostrongylus longispicularis and Cooperia lyrata were found for the first time in Wyoming, Ostertagia circumcincta was found for the first time in cattle in Wyoming, and Haemonchus placei, tentatively identified in a previous survey, was definitively confirmed. Predominant species (and prevalence) were Ostertagia ostertagi (98%), Cooperia oncophora (60.6%), Ostertagia bisonis (41.8%), Cooperia bisonis (33.6%) and T. Axei (27.9%). One or more of the four species of Ostertagia were found in all animals. Inhibited O. ostertagi and O. bisonis larvae predominated from November to April and reached a peak in January to comprise 88% of the total nematode burden for that month. The adult population of abomasal nematodes peaked in April and predominated thereafter until October. Haemonchus placei also spent the autumn-winter period in an inhibited state of development. Faecal egg counts were lowest during winter months, when the highest number of worms were present as L4 larvae, as determined by luminal and mucosal counts. Nematode populations in the small intestine peaked in June and persisted until November. The results of this study showed the magnitude and species composition of nematode parasitism in cattle raised on high altitude grass plains, underscored the inaccuracy of faecal egg counts as an indicator of worm burden during fall and winter seasons, and provided information on which anthelmintic treatment timing would be most efficacious.

Abomasum↗