The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
L J E Karlsson - One of the best experts on this subject based on the ideXlab platform.
-
Adjustment of faecal Worm Egg count for faecal moisture content will not affect rate of genetic gain when selecting for Worm resistance in Merino sheep
2020Co-Authors: Johan Greeff, D. Palmer, L J E KarlssonAbstract:Faecal Worm Egg count (WEC) of Merino sheep at weaning and hogget age were analysed to determine to what extent re-ranking would occur when WEC is adjusted to a standard dry matter basis. The phenotypic correlation between WEC and dry matter adjusted WEC was 0.69 or higher in weaners and hogget animals. This indicates that some re-ranking will occur but as the genetic correlation between WEC and dry matter adjusted WEC was very high (>0.92) this indicates that these traits are genetically the same traits and that adjusting WEC for faecal moisture content would not increase genetic progress in selecting for Worm resistance.
-
expression of Worm resistance in sheep selected for low Worm Egg counts fed at maintenance or above maintenance level
Animal Production Science, 2019Co-Authors: J C Greeff, D G Palmer, L J E KarlssonAbstract:The present study reports on changes in faecal Worm-Egg counts (WEC), larval composition, and the number of Worms at different developmental stages in young sheep sourced from a flock selected for reduced faecal Worm-Egg counts over 15 years. The sheep were individually penned and fed a maintenance (1.0 M) or a 1.5 times maintenance (1.5 M) diet over two periods, namely, Worm-free and infection phases. They were dosed weekly with 10 000 Trichostrongylus colubriformis and 10 000 Teladorsagia circumcincta L3 infective larvae for 11 weeks. Sheep on the 1.5 M diet had lower WEC and higher bodyweights than did sheep on the 1.0 M diet. A significant decline in the percentage T. colubriformis occurred during the experiment, but no concomitant change in T. circumcincta was noticed. Resistant sheep had significantly (P < 0.001) fewer Worms at necropsy, and also shed significantly (P < 0.001) fewer Worm Eggs during the experiment. Restricted feeding reduced bodyweight significantly (P < 0.001) and had a small but significant (P < 0.04) effect on the faecal Worm-Egg output and on the number of T. colubriformis Worms (P < 0.01) in both the control and resistant sheep. The study showed that sheep selected for low WEC resulted in significantly (P < 0.001) lower WEC than in an unselected control line fed at a maintenance (1.0 M) and at an above-maintenance (1.5 M) level. Restricted feeding reduced bodyweight and had a small negative, and inconsistent, effect on the faecal Worm-Egg output in both the control and resistant lines.
-
reduction of faecal Worm Egg count Worm numbers and Worm fecundity in sheep selected for Worm resistance following artificial infection with teladorsagia circumcincta and trichostrongylus colubriformis
Veterinary Parasitology, 2010Co-Authors: Kathryn E Kemper, D G Palmer, J C Greeff, S C Bishop, L J E KarlssonAbstract:Abstract We examined the changes to populations of Trichostrongylus colubriformis and Teledorsagia circumcincta in mature sheep selected for reduced faecal Worm Egg count (WEC). Worm resistant (n = 19) and control (n = 10) genotype sheep were penned and dosed with a total of 10,000 T. colubriformis and 10,000 T. circumcincta per week for 18-weeks. Sheep genotypes were from lines previously bred over 15 years for either low WEC (resistant) or non-selected (control). Weekly WEC and the proportion of larvae from each species in faecal culture were measured during weeks 3–17. Egg hatchability was assessed on a pooled faecal sample from Worm resistant or control genotype sheep at weeks 7, 9, 10, 13, 14 and 17. At week 18 the number of adult and immature Worms (early and late 4th, and 5th stage), and indicators of Worm fecundity (female Worm length and number of Eggs in utero) were assessed at necropsy. Results show that resistant sheep had reduced mean WEC to only 18% of the control (P
-
Merino ewes bred for parasite resistance reduce larval contamination onto pasture during the peri-parturient period.
Animal, 2009Co-Authors: A.r. Williams, Johan Greeff, R J Dobson, Phil Vercoe, L J E KarlssonAbstract:The peri-parturient period is crucial for controlling Worms as the acquired immunity of ewes is disrupted, resulting in an increase in faecal Worm Egg counts. Two hypotheses were tested in this experiment that ewes bred for Worm resistance would have lower faecal Worm Egg counts than unselected control ewes, during late pregnancy and lactation, under similar but separate grazing areas; and also that numbers of infective nematode larvae would be lower on pastures grazed by resistant ewes than pastures grazed by unselected control ewes. Faecal samples were collected from resistant and unselected ewes in late pregnancy and early lactation, during the winter rainfall season, and analysed for numbers of Trichostrongylus colubriformis and Teladorsagia circumcincta. Pasture samples were taken 1 week before and 7 weeks after lambing started and analysed for infective larvae. In all sheep, Worm Egg counts rose 2 weeks prior to lambing and continued into lactation. Worm Egg counts were significantly lower in the resistant ewes from 1 week before lambing to 2 weeks after lambing. There were no differences in Egg counts between single- and twin-bearing ewes in the resistant line. However, twin-bearing control ewes had significantly higher Egg counts than single-bearing control ewes. Following lactation, plots grazed by resistant ewes had substantially less contamination with T. colubriformis larvae, but there were no differences in numbers of T. circumcincta larvae. Our results demonstrate that sheep bred for Worm resistance has lower Worm burdens during the peri-parturient phase and that lambs born to resistant ewes face a lower larval challenge during their introduction to grazing. In our environment, selection for low Worm Egg counts has produced sheep highly resistant to T. colubriformis, but has had less impact on resistance towards T. circumcincta.
-
selection response in fecal Worm Egg counts in the rylington merino parasite resistant flock
Australian Journal of Experimental Agriculture, 2006Co-Authors: L J E Karlsson, J C GreeffAbstract:The Rylington Merino internal parasite resistant selection line was initiated in 1987 from a wide genetic base of 100 ewe flocks. Selection for parasite resistance was based on selecting animals with a low Worm Egg count in a natural parasite challenge environment. The realised annual genetic gain for estimated breeding value of Worm Egg count is 2.7%. The genetic gain in parasite resistance has been achieved without any adverse genetic correlations with the other economically important production traits. There is an unfavourable genetic correlation between Worm Egg count and scouring traits. The recommendation to industry is to select for both low Worm Egg count and reduced diarrhoea and combine these traits with other economically important production traits. The relative weighting applied to each component trait will vary according to the local parasite challenge situation and the time frame available to achieve sustainable parasite control.
J C Greeff - One of the best experts on this subject based on the ideXlab platform.
-
temporal changes in circulatory blood cell parameters of sheep genetically different for faecal Worm Egg count and diarrhoea from late summer to spring in a mediterranean environment
Animal Production Science, 2020Co-Authors: J C Greeff, D. Palmer, Graeme MartinAbstract:Differences in haematology traits were investigated in Worm-resistant and Worm-susceptible Merino sheep that were genetically prone or less prone to developing diarrhoea in a winter rainfall region. The experiment was a 2 × 2 × 2 × 5 design. Male and female sheep aged 8–9 months old identified as having high (H) or low (L) breeding values for dags (breech soiling) and for Worm Egg counts (WEC) were allocated to one of four genetic groups: HH, HL, LH and LL (the first letter refers to dags and the second to WEC). The animals were sampled five times from autumn through winter to spring, in March, May, June (ewes only), July (rams only), August and in September after exposure to a natural paddock infection dominated by Trichostrongylus, Teladorsagia, Chabertia and Oesophagostomum. Measurements were packed cell volume, haemoglobin, red blood cell count, differential white cell counts, WEC and faecal consistency score. At all sampling times, there were large (P < 0.01) differences between groups within sex for both the faecal consistency score and WEC. The genetic effect for WEC was large (P < 0.01), as Worm-susceptible sheep shed 10- (ewes) and 6-fold (rams) as many Worm Eggs at their WEC peak as the Worm-resistant sheep at the end of the experiment. In the high-dag groups, the faecal consistency score was ~0.5 units higher for rams and 0.4 units higher for ewes, throughout the experiment. The optimum time to measure dags and WEC in this environment appears to be 6–8 weeks after the start of the winter rain. No differences were found among any of the treatment groups for any haematology trait. The haematogram changed significantly throughout the experiment, but genetic selection for low-dag score (reduced diarrhoea) or low WEC did not provide an acceptable discriminator in circulatory haematology traits between these genetically distinct groups of Merino sheep. It was concluded that circulatory haematology traits do not offer opportunities to select against diarrhoea or increased Worm resistance in sheep.
-
expression of Worm resistance in sheep selected for low Worm Egg counts fed at maintenance or above maintenance level
Animal Production Science, 2019Co-Authors: J C Greeff, D G Palmer, L J E KarlssonAbstract:The present study reports on changes in faecal Worm-Egg counts (WEC), larval composition, and the number of Worms at different developmental stages in young sheep sourced from a flock selected for reduced faecal Worm-Egg counts over 15 years. The sheep were individually penned and fed a maintenance (1.0 M) or a 1.5 times maintenance (1.5 M) diet over two periods, namely, Worm-free and infection phases. They were dosed weekly with 10 000 Trichostrongylus colubriformis and 10 000 Teladorsagia circumcincta L3 infective larvae for 11 weeks. Sheep on the 1.5 M diet had lower WEC and higher bodyweights than did sheep on the 1.0 M diet. A significant decline in the percentage T. colubriformis occurred during the experiment, but no concomitant change in T. circumcincta was noticed. Resistant sheep had significantly (P < 0.001) fewer Worms at necropsy, and also shed significantly (P < 0.001) fewer Worm Eggs during the experiment. Restricted feeding reduced bodyweight significantly (P < 0.001) and had a small but significant (P < 0.04) effect on the faecal Worm-Egg output and on the number of T. colubriformis Worms (P < 0.01) in both the control and resistant sheep. The study showed that sheep selected for low WEC resulted in significantly (P < 0.001) lower WEC than in an unselected control line fed at a maintenance (1.0 M) and at an above-maintenance (1.5 M) level. Restricted feeding reduced bodyweight and had a small negative, and inconsistent, effect on the faecal Worm-Egg output in both the control and resistant lines.
-
heritabilities of iga and ige activities against teladorsagia and trichostrongylus l3 larval antigens correlated with traits for faecal Worm Egg count health and productivity in merino sheep
Animal Production Science, 2019Co-Authors: Zhongquan Zhao, Mengzhi Wang, Dieter Palmer, R J Shaw, John Karlsson, Philip E Vercoe, Graeme Martin, J C GreeffAbstract:Low faecal Worm-Egg count (FEC) has been used as a phenotypic trait for breeding sheep for resistance to nematode infection. Application of this trait has resulted in a major reduction in Worm-Egg output in faeces, but in certain environments some of the resistant sheep develop what is believed to be a hypersensitivity-associated diarrhoea, resulting in soiling of the breech area (dags). To avoid breeding sheep with a propensity to scour, it, therefore, seems logical to combine selection for low FEC with selection for a trait based on the immune response to Worm infection. We, therefore, investigated the relationships between immunoglobulin A (IgA) and immunoglobulin E (IgE) activities against L3 larval antigens of Teladorsagia circumcincta and Trichostrongylus colubriformis and measured their inheritance and their genetic relationships with FEC, dag traits and measures of production. Total plasma IgE concentrations were also determined and included in the study. We used 762 progeny from 23 Merino sires selected for resistance to helminths (the ‘Rylington Flock’) and to breech flystrike. Total plasma IgE and IgE activities against T. circumcincta were negatively correlated with liveweight, longissimus dorsi muscle depth, and fleece weight, but positively correlated with severity of dags, softer faeces and back-fat depth. The IgA activity against T. circumcincta was negatively correlated with liveweight and clean fleece weight, but positively correlated with back-fat depth and faecal consistency score. The IgA activity against T. colubriformis was not correlated with any measure, except the breeding value for dags around yearling age. The heritability for the IgA activity against T. circumcincta and T. colubriformis was 0.13 and 0.08 respectively. The heritability for both IgE activity against T. circumcincta and total plasma IgE concentration was 0.39. We conclude that it is feasible to combine FEC and dag traits with an immune trait (in this case, helminth-specific IgE activity and total plasma IgE concentration) and, thus, genetically select sheep for resistance to both helminths and diarrhoea. However, under natural Worm-challenge conditions, blood sampling protocols need to developed, on the basis of animal age, season and environment, for optimum estimation of the immune trait and its relationships with other traits.
-
reduction of faecal Worm Egg count Worm numbers and Worm fecundity in sheep selected for Worm resistance following artificial infection with teladorsagia circumcincta and trichostrongylus colubriformis
Veterinary Parasitology, 2010Co-Authors: Kathryn E Kemper, D G Palmer, J C Greeff, S C Bishop, L J E KarlssonAbstract:Abstract We examined the changes to populations of Trichostrongylus colubriformis and Teledorsagia circumcincta in mature sheep selected for reduced faecal Worm Egg count (WEC). Worm resistant (n = 19) and control (n = 10) genotype sheep were penned and dosed with a total of 10,000 T. colubriformis and 10,000 T. circumcincta per week for 18-weeks. Sheep genotypes were from lines previously bred over 15 years for either low WEC (resistant) or non-selected (control). Weekly WEC and the proportion of larvae from each species in faecal culture were measured during weeks 3–17. Egg hatchability was assessed on a pooled faecal sample from Worm resistant or control genotype sheep at weeks 7, 9, 10, 13, 14 and 17. At week 18 the number of adult and immature Worms (early and late 4th, and 5th stage), and indicators of Worm fecundity (female Worm length and number of Eggs in utero) were assessed at necropsy. Results show that resistant sheep had reduced mean WEC to only 18% of the control (P
-
selection response in fecal Worm Egg counts in the rylington merino parasite resistant flock
Australian Journal of Experimental Agriculture, 2006Co-Authors: L J E Karlsson, J C GreeffAbstract:The Rylington Merino internal parasite resistant selection line was initiated in 1987 from a wide genetic base of 100 ewe flocks. Selection for parasite resistance was based on selecting animals with a low Worm Egg count in a natural parasite challenge environment. The realised annual genetic gain for estimated breeding value of Worm Egg count is 2.7%. The genetic gain in parasite resistance has been achieved without any adverse genetic correlations with the other economically important production traits. There is an unfavourable genetic correlation between Worm Egg count and scouring traits. The recommendation to industry is to select for both low Worm Egg count and reduced diarrhoea and combine these traits with other economically important production traits. The relative weighting applied to each component trait will vary according to the local parasite challenge situation and the time frame available to achieve sustainable parasite control.
D G Palmer - One of the best experts on this subject based on the ideXlab platform.
-
expression of Worm resistance in sheep selected for low Worm Egg counts fed at maintenance or above maintenance level
Animal Production Science, 2019Co-Authors: J C Greeff, D G Palmer, L J E KarlssonAbstract:The present study reports on changes in faecal Worm-Egg counts (WEC), larval composition, and the number of Worms at different developmental stages in young sheep sourced from a flock selected for reduced faecal Worm-Egg counts over 15 years. The sheep were individually penned and fed a maintenance (1.0 M) or a 1.5 times maintenance (1.5 M) diet over two periods, namely, Worm-free and infection phases. They were dosed weekly with 10 000 Trichostrongylus colubriformis and 10 000 Teladorsagia circumcincta L3 infective larvae for 11 weeks. Sheep on the 1.5 M diet had lower WEC and higher bodyweights than did sheep on the 1.0 M diet. A significant decline in the percentage T. colubriformis occurred during the experiment, but no concomitant change in T. circumcincta was noticed. Resistant sheep had significantly (P < 0.001) fewer Worms at necropsy, and also shed significantly (P < 0.001) fewer Worm Eggs during the experiment. Restricted feeding reduced bodyweight significantly (P < 0.001) and had a small but significant (P < 0.04) effect on the faecal Worm-Egg output and on the number of T. colubriformis Worms (P < 0.01) in both the control and resistant sheep. The study showed that sheep selected for low WEC resulted in significantly (P < 0.001) lower WEC than in an unselected control line fed at a maintenance (1.0 M) and at an above-maintenance (1.5 M) level. Restricted feeding reduced bodyweight and had a small negative, and inconsistent, effect on the faecal Worm-Egg output in both the control and resistant lines.
-
proficiency testing assessments for nematode Worm Egg counting based on poisson variation
Veterinary Parasitology, 2014Co-Authors: A J Van Burgel, J Lyon, R B Besier, D G PalmerAbstract:The Poisson distribution provides an appropriate model for the variation within laboratories in Worm Egg counting. This is demonstrated by the results from annual quality assessment exercises in which laboratories in Australia tested multiple samples from the same mixtures prepared using different Worm Egg densities. Confidence intervals based on simulations using the Poisson distribution are recommended in the analysis of the results to identify laboratories showing significant bias or overdispersion, hence indicating possible procedural errors.
-
reduction of faecal Worm Egg count Worm numbers and Worm fecundity in sheep selected for Worm resistance following artificial infection with teladorsagia circumcincta and trichostrongylus colubriformis
Veterinary Parasitology, 2010Co-Authors: Kathryn E Kemper, D G Palmer, J C Greeff, S C Bishop, L J E KarlssonAbstract:Abstract We examined the changes to populations of Trichostrongylus colubriformis and Teledorsagia circumcincta in mature sheep selected for reduced faecal Worm Egg count (WEC). Worm resistant (n = 19) and control (n = 10) genotype sheep were penned and dosed with a total of 10,000 T. colubriformis and 10,000 T. circumcincta per week for 18-weeks. Sheep genotypes were from lines previously bred over 15 years for either low WEC (resistant) or non-selected (control). Weekly WEC and the proportion of larvae from each species in faecal culture were measured during weeks 3–17. Egg hatchability was assessed on a pooled faecal sample from Worm resistant or control genotype sheep at weeks 7, 9, 10, 13, 14 and 17. At week 18 the number of adult and immature Worms (early and late 4th, and 5th stage), and indicators of Worm fecundity (female Worm length and number of Eggs in utero) were assessed at necropsy. Results show that resistant sheep had reduced mean WEC to only 18% of the control (P
-
biochemical differences in merino sheep selected for resistance against gastro intestinal nematodes and genetic and nutritional effects on faecal Worm Egg output
Animal Science, 2005Co-Authors: T L Smith, L J E Karlsson, R B Besier, D G Palmer, J C GreeffAbstract:The faecal Egg count (FEC) and total Egg output is reduced in parasite-resistant sheep and breeding sheep for resistance should reduce infective larval contamination of pastures. This research compares lambs and rams from the parasite-resistant flock, Rylington Merinos, with unselected controls at the same level of larval challenge and the same level of food supply in an animal-house environment. The sheep were penned individually. The parasite resistant sheep excreted 0·85-fold less Eggs than the control animals after infection with Trichostrongylus colubriformis and Ostertagia circumcincta for 12 or 18 weeks. During the infection period the parasite resistant lambs had higher plasma immunoglobulin concentration and higher ratio of globulin to albumin than the control animals. In the mature rams these genotype differences diminished. They also had lighter mass of the small intestine with a higher proportion of mucosa, but heavier mass of the large intestine. Parasite infection caused a depletion of blood glutathione in the lambs given food at maintenance or 1·5 × maintenance, and the parasite-resistant sheep (both lambs and rams) also had lower glutathione concentration. Maintaining good body nutrient reserve before the infection reduced the Egg output in the early stage of the infection. Food intake had little effect on Worm Egg production in young sheep given food at maintenance or above. It is suggested that an improvement of nutrition, sulphur-containing amino acids in particular, is required to recover the loss of productive performance caused by the infection.
K. Bell - One of the best experts on this subject based on the ideXlab platform.
-
Investigation of causes of "low Worm Egg count diarrhoea" in sheep in Western Australia
2020Co-Authors: Caroline Jacobson, K. Bell, D. Forshaw, R B BesierAbstract:Nine flocks of sheep with "low Worm Egg count scouring" in the south west of Western Australia were investigated over a three-year period. There was no significant difference in the faecal Worm Egg counts of "scouring sheep" (diarrhoea and severe dag) compared to "normal sheep" (pelleted faeces and mild or no dag). Teladorsagia (Ostertagia) circumcincta and Trichostrongylus spp were the strongyles most commonly identified on total Worm counts and differentiation of larvae recovered from faeces and pasture. Immature strongyle Worms accounted for the largest proportion of total Worm counts. Adult Worm burdens were small in most sheep. Scouring sheep had significantly higher numbers of early fourth stage larvae. There was no histopathological evidence of bacterial or viral causes of scouring in any of the flocks that could be supported with bacteriology. Two flocks had marginal selenium status. One flock was diagnosed with helminthosis based on increased Worm Egg counts and high total Worm counts. Larval hypersensitivity scouring, nutrition or a combination of these two factors were the most likely causes of scouring in the other eight mobs based on exclusion of other known causes of scouring. Treatment with moxidectin drench and an ivermectin controlled-release capsule did not change faecal moisture of treated sheep compared to untreated sheep three to five weeks after treatment.
-
associations between trichostrongylid Worm Egg count and productivity measures in dorper lambs
Veterinary Parasitology, 2011Co-Authors: Joshua P.a. Sweeny, Caroline Jacobson, G E Gardner, R J Dobson, K. BellAbstract:Two flocks of pure bred Dorper lambs were managed separately according to sex (283 ewe lambs and 212 ram lambs) in southern Western Australia. Faecal sample collection, weighing and body condition assessments were performed for each lamb on 2 occasions, specifically pre-weaning (approximately 14 weeks of age) and post-weaning (approximately 9 months of age). Body condition score (BCS) was assessed using a scale of 1 (very thin, emaciated) to 5 (excessively fat). Faecal Worm Egg counts (WECs) were measured using a modified McMaster technique and larval cultures were performed to identify trichostrongylid nematode genera present. Eye muscle and c-site fat depths were measured using ultrasound at post-weaning. Lambs received an abamectin anthelmintic treatment at weaning (18 weeks of age). Worm Egg count data was assessed for normality of data distribution and homogeneity of variance. This data was transformed using log10(WEC + 25) to stabilise variances between groups prior to statistical analyses and general linear models were used to assess relationships between WEC and productivity measures. Mean WECs were 564 Eggs per gram of faeces (EPG) and 514 EPG at pre- and post-weaning in the ewe flock and 552 EPG and 480 EPG at pre- and post-weaning in the ram flock. Teladorsagia (Ostertagia) circumcincta, Trichostrongylus spp. and Oesophagostomum spp. larvae were identified. No lambs with WEC 1000 EPG post-weaning. Ewe and ram lambs with WEC > 1000 EPG at pre-weaning were 42 (12-145 95% CI) and 37 (9-153) times more likely to have WEC > 1000 EPG at post-weaning than lambs with WEC 501-1000 EPG at pre-weaning. There were no significant relationships between WEC and live weight in the ram flock, while relationships between WEC and live weight were inconsistent in the ewe lamb flock. There was no relationship between WEC and eye muscle or c-site fat depth. Significant negative relationships between WEC and BCS were identified at pre- and post-weaning for both flocks. Lambs with WEC 1000 EPG at pre- and post-weaning. In conclusion, high WEC was associated with lower body condition in Dorper lambs, however the relationship between WEC and live weight was inconsistent and there was no effect on eye muscle depth.
-
association between nematode larvae and low Worm Egg count diarrhoea in sheep in western australia
Veterinary Parasitology, 2009Co-Authors: Caroline Jacobson, K. Bell, D. Forshaw, Brown BesierAbstract:Nine flocks of sheep with a high prevalence (>30%) of diarrhoea and severe breech faecal soiling were investigated over a three-year period to examine the causes of diarrhoea in sheep with low mean faecal Worm Egg counts (WEC). All nine flocks were located in the southwest of Western Australia in areas with a winter rainfall pattern (Mediterranean climate). There was no difference (p = 0.304) in WEC of diarrhoeic sheep (loose faeces and severe breech faecal soiling) and "normal sheep" (pelleted faeces and mild or no breech faecal soiling). Teladorsagia (Ostertagia) circumcincta and Trichostrongylus spp. were the nematodes most commonly identified by total Worm counts and differentiation of larvae recovered from faeces and pasture. Larval stages of strongyle Worms accounted for the largest proportion of total Worm counts in both diarrhoeic and normal sheep. Adult Worm burdens were small in most sheep. Diarrhoeic sheep had higher numbers of fourth stage larvae than normal sheep (p = 0.046). There was no histopathological evidence of bacterial or viral causes of diarrhoea in any of the flocks or bacteriological evidence of bacterial infections associated with diarrhoea. Two flocks had marginal selenium glutathione peroxidase (selenium) levels. One flock was diagnosed with helminthosis based on rising WEC and high total Worm counts. Larval hypersensitivity diarrhoea, nutritional factors or a combination of these two factors were the most likely causes of diarrhoea in the other eight flocks based on exclusion of other known causes of diarrhoea. Treatment with moxidectin and an ivermectin controlled-release capsule did not change faecal moisture content of treated sheep compared to untreated sheep three to five weeks after treatment. The findings suggest that the immune response to strongyle larvae may explain some cases of low WEC diarrhoea observed during winter-spring in immunocompetent mature sheep grazing in Mediterranean environments.
Caroline Jacobson - One of the best experts on this subject based on the ideXlab platform.
-
Investigation of causes of "low Worm Egg count diarrhoea" in sheep in Western Australia
2020Co-Authors: Caroline Jacobson, K. Bell, D. Forshaw, R B BesierAbstract:Nine flocks of sheep with "low Worm Egg count scouring" in the south west of Western Australia were investigated over a three-year period. There was no significant difference in the faecal Worm Egg counts of "scouring sheep" (diarrhoea and severe dag) compared to "normal sheep" (pelleted faeces and mild or no dag). Teladorsagia (Ostertagia) circumcincta and Trichostrongylus spp were the strongyles most commonly identified on total Worm counts and differentiation of larvae recovered from faeces and pasture. Immature strongyle Worms accounted for the largest proportion of total Worm counts. Adult Worm burdens were small in most sheep. Scouring sheep had significantly higher numbers of early fourth stage larvae. There was no histopathological evidence of bacterial or viral causes of scouring in any of the flocks that could be supported with bacteriology. Two flocks had marginal selenium status. One flock was diagnosed with helminthosis based on increased Worm Egg counts and high total Worm counts. Larval hypersensitivity scouring, nutrition or a combination of these two factors were the most likely causes of scouring in the other eight mobs based on exclusion of other known causes of scouring. Treatment with moxidectin drench and an ivermectin controlled-release capsule did not change faecal moisture of treated sheep compared to untreated sheep three to five weeks after treatment.
-
associations between trichostrongylid Worm Egg count and productivity measures in dorper lambs
Veterinary Parasitology, 2011Co-Authors: Joshua P.a. Sweeny, Caroline Jacobson, G E Gardner, R J Dobson, K. BellAbstract:Two flocks of pure bred Dorper lambs were managed separately according to sex (283 ewe lambs and 212 ram lambs) in southern Western Australia. Faecal sample collection, weighing and body condition assessments were performed for each lamb on 2 occasions, specifically pre-weaning (approximately 14 weeks of age) and post-weaning (approximately 9 months of age). Body condition score (BCS) was assessed using a scale of 1 (very thin, emaciated) to 5 (excessively fat). Faecal Worm Egg counts (WECs) were measured using a modified McMaster technique and larval cultures were performed to identify trichostrongylid nematode genera present. Eye muscle and c-site fat depths were measured using ultrasound at post-weaning. Lambs received an abamectin anthelmintic treatment at weaning (18 weeks of age). Worm Egg count data was assessed for normality of data distribution and homogeneity of variance. This data was transformed using log10(WEC + 25) to stabilise variances between groups prior to statistical analyses and general linear models were used to assess relationships between WEC and productivity measures. Mean WECs were 564 Eggs per gram of faeces (EPG) and 514 EPG at pre- and post-weaning in the ewe flock and 552 EPG and 480 EPG at pre- and post-weaning in the ram flock. Teladorsagia (Ostertagia) circumcincta, Trichostrongylus spp. and Oesophagostomum spp. larvae were identified. No lambs with WEC 1000 EPG post-weaning. Ewe and ram lambs with WEC > 1000 EPG at pre-weaning were 42 (12-145 95% CI) and 37 (9-153) times more likely to have WEC > 1000 EPG at post-weaning than lambs with WEC 501-1000 EPG at pre-weaning. There were no significant relationships between WEC and live weight in the ram flock, while relationships between WEC and live weight were inconsistent in the ewe lamb flock. There was no relationship between WEC and eye muscle or c-site fat depth. Significant negative relationships between WEC and BCS were identified at pre- and post-weaning for both flocks. Lambs with WEC 1000 EPG at pre- and post-weaning. In conclusion, high WEC was associated with lower body condition in Dorper lambs, however the relationship between WEC and live weight was inconsistent and there was no effect on eye muscle depth.
-
association between nematode larvae and low Worm Egg count diarrhoea in sheep in western australia
Veterinary Parasitology, 2009Co-Authors: Caroline Jacobson, K. Bell, D. Forshaw, Brown BesierAbstract:Nine flocks of sheep with a high prevalence (>30%) of diarrhoea and severe breech faecal soiling were investigated over a three-year period to examine the causes of diarrhoea in sheep with low mean faecal Worm Egg counts (WEC). All nine flocks were located in the southwest of Western Australia in areas with a winter rainfall pattern (Mediterranean climate). There was no difference (p = 0.304) in WEC of diarrhoeic sheep (loose faeces and severe breech faecal soiling) and "normal sheep" (pelleted faeces and mild or no breech faecal soiling). Teladorsagia (Ostertagia) circumcincta and Trichostrongylus spp. were the nematodes most commonly identified by total Worm counts and differentiation of larvae recovered from faeces and pasture. Larval stages of strongyle Worms accounted for the largest proportion of total Worm counts in both diarrhoeic and normal sheep. Adult Worm burdens were small in most sheep. Diarrhoeic sheep had higher numbers of fourth stage larvae than normal sheep (p = 0.046). There was no histopathological evidence of bacterial or viral causes of diarrhoea in any of the flocks or bacteriological evidence of bacterial infections associated with diarrhoea. Two flocks had marginal selenium glutathione peroxidase (selenium) levels. One flock was diagnosed with helminthosis based on rising WEC and high total Worm counts. Larval hypersensitivity diarrhoea, nutritional factors or a combination of these two factors were the most likely causes of diarrhoea in the other eight flocks based on exclusion of other known causes of diarrhoea. Treatment with moxidectin and an ivermectin controlled-release capsule did not change faecal moisture content of treated sheep compared to untreated sheep three to five weeks after treatment. The findings suggest that the immune response to strongyle larvae may explain some cases of low WEC diarrhoea observed during winter-spring in immunocompetent mature sheep grazing in Mediterranean environments.
