Where's the risk? Landscape epidemiology of gastrointestinal parasitism in Alberta beef cattle

Review and Evaluation of Ostertagia ostertagi Antibody ELISA for Application on Serum Samples in First Season Grazing Calves

The O. ostertagi-Ab ELISA assay is widely used as a diagnostic tool for monitoring gastrointestinal (GI) nematodes using milk samples from adult dairy cows. This assay is potentially also useful to analyse serum samples from first-season grazing (FSG) calves, providing a more cost-effective and robust diagnostic technique than the current serum pepsinogen assay. However, a comprehensive evaluation of its use in serum samples from FSG calves has not yet been conducted. In this study, we first reviewed the available scientific literature in which the O. ostertagi-Ab ELISA was applied to serum samples from FSG calves. Then, a field study was conducted to compare results from the O. ostertagi-Ab ELISA assay with a serum pepsinogen assay on a set of 230 serum samples from 11 commercial dairy herds (seven in Belgium and four in Sweden). The literature review showed an increase in mean antibody levels, expressed as optical density ratio (ODR) values, from <0.4 (early grazing season) to values of 0.7-1.1 (late grazing season). Three out of five studies found a negative correlation between O. ostertagi antibody levels measured during the late grazing season and weight gain, while the other two studies found no correlation between the two variables. Our field studies showed a good correlation between O. ostertagi antibody levels and the results from the pepsinogen assay. Both indicators were negatively related to average daily weight gain in the Belgian herds, but not in the Swedish herds. Overall, the results suggest that the O. ostertagi-Ab ELISA test can be a useful tool in FSG calves and could replace the use of the serum pepsinogen assay at the end of the grazing season for general monitoring purposes.

Seasonal epidemiology of gastrointestinal nematodes of cattle in the northern continental climate zone of western Canada as revealed by internal transcribed spacer-2 ribosomal DNA nemabiome barcoding

Background

Gastrointestinal nematode (GIN) epidemiology is changing in many regions of the world due to factors such as global warming and emerging anthelmintic resistance. However, the dynamics of these changes in northern continental climate zones are poorly understood due to a lack of empirical data.

Methods

We studied the accumulation on pasture of free-living infective third-stage larvae (L3) of different GIN species from fecal pats deposited by naturally infected grazing cattle. The field study was conducted on three organic farms in Alberta, western Canada. Grass samples adjacent to 24 fecal pats were collected from each of three different pastures on each farm. Internal transcribed spacer-2 nemabiome metabarcoding was used to determine the GIN species composition of the harvested larvae. The rotational grazing patterns of the cattle ensured that each pasture was contaminated only once by fecal pat deposition. This design allowed us to monitor the accumulation of L3 of specific GIN species on pastures under natural climatic conditions without the confounding effects of pasture recontamination or anthelmintic treatments.

Results

In seven out of the nine pastures, grass L3 counts peaked approximately 9 weeks after fecal deposition and then gradually declined. However, a relatively large number of L3 remained in the fecal pats at the end of the grazing season. Nemabiome metabarcoding revealed that Cooperia oncophora and Ostertagia ostertagi were the two most abundant species on all of the pastures and that the dynamics of larval accumulation on grass were similar for both species. Daily precipitation and temperature across the whole sampling period were similar for most of the pastures, and multiple linear regression showed that accumulated rainfall 1 week prior to sample collection had a significant impact on the pasture L3 population, but accumulated rainfall 3 weeks prior to sample collection did not.

Conclusions

The results suggest that the pasture L3 population was altered by short-term microclimatic conditions conducive for horizontal migration onto grass. Overall, the results show the importance of the fecal pat as a refuge and reservoir for L3 of cattle GIN on western Canadian pastures, and provide an evidence base for the risk assessment of rotational grazing management in the region.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05101-w.

Gastrointestinal nematode prevalence and fecal egg counts in beef cattle from western Canada

Fecal samples were collected from cows (n = 1458), calves (n = 1188), and replacement heifers (n = 921) between 2012 and 2014 from 199 herds and generalized estimating equations were used to predict mean fecal egg counts and prevalence of egg-positive samples. Replacement heifers had the highest prevalence of Trichostrongylid-type eggs at 83% [95% confidence interval (CI): 78% to 87%], and cows had the lowest at 75% (95% C: 70% to 81%). Nematodirus spp. was most frequently present in calves [predicted prevalence: 34% (95% CI: 28% to 40%)]. Mean fecal egg counts were highest in calves with 5.9 (95% CI: 3.9 to 7.8) Trichostrongylid-type eggs per gram (EPG) of feces and 1.0 (95% CI: 0.7 to 1.4) Nematodirus spp. EPG. Although mean egg counts were low to moderate, the high prevalence highlights the need to further investigate the epidemiology of gastrointestinal nematodes in western Canada. This is particularly relevant considering management changes, increasing herd sizes, climate change, and threatening anthelmintic resistance.

Prevalence, fecal egg counts, and species identification of gastrointestinal nematodes in replacement dairy heifers in Canada

Information is scarce regarding the epidemiology of gastrointestinal nematodes in Canadian dairy heifers. The objectives of this study were to estimate the prevalence and fecal egg counts of gastrointestinal nematodes in dairy heifers, and using a novel deep-amplicon sequencing approach, to identify the predominant gastrointestinal nematode species in Canadian dairy replacement heifers. Fresh environmental fecal samples (n = 2,369) were collected from replacement heifers on 306 dairy farms across western Canada, Ontario, Québec, and Atlantic Canada. Eggs per gram of feces (EPG) were determined using a modified Wisconsin double-centrifugation sugar flotation technique. Predominant nematode species at the farm level were identified by deep-amplicon nemabiome sequencing of the internal transcribed spacer-2 rDNA locus of nematode third-stage larvae. Generalized estimating equations were used to estimate predicted parasite prevalence and mean EPG in all heifers and by province, allowing for clustering within herds. Individual heifer egg counts ranged from 0 to 141 EPG (median: 0 EPG; interquartile range: 0 to 71 EPG). Gastrointestinal nematodes were detected in 20.9% (95% confidence interval: 17.2 to 24.6%) of heifers, and the predicted mean strongylid EPG accounting for clustering on farms was 1.1 (95% confidence interval: 0.6 to 1.6). The predominant parasite species were Cooperia oncophora and Ostertagia ostertagi. This is the first study in Canada to use a combination of deep-amplicon nemabiome sequencing and a traditional egg count method to describe the epidemiology of gastrointestinal nematodes in dairy heifers.

Bulk tank milk prevalence and production losses, spatial analysis, and predictive risk mapping of Ostertagia ostertagi infections in Mexican cattle herds

This study investigated the prevalence, production losses, spatial clustering, and predictive risk mapping in different climate zones in five states of Mexico. The bulk tank milk samples obtained between January and April 2015 were analyzed for antibodies against Ostertagia ostertagi using the Svanovir ELISA. A total of 1204 farm owners or managers answered the questionnaire. The overall herd prevalence and mean optical density ratio (ODR) of parasite were 61.96% and 0.55, respectively. Overall, the production loss was approximately 0.542 kg of milk per parasited cow per day (mean ODR = 0.92, 142 farms, 11.79%). The spatial disease cluster analysis using SatScan software indicated that two high-risk clusters were observed. In the multivariable analysis, three models were tested for potential association with the ELISA results supported by climatic, environmental, and management factors. The final logistic regression model based on both climatic/environmental and management variables included the factors rainfall, elevation, land surface temperature (LST) day, and parasite control program that were significantly associated with an increased risk of infection. Geostatistical kriging was applied to generate a risk map for the presence of parasite in dairy cattle herds in Mexico. The results indicate that climatic and meteorological factors had a higher potential impact on the spatial distribution of O. ostertagi than the management factors.

Epidemiology of gastrointestinal nematode infections in grazing yearling beef cattle in Saskatchewan

The objective of this study was to provide contemporary data on the epidemiology of gastrointestinal nematode parasite infections of grazing yearling beef cattle in the province of Saskatchewan. Fecal samples (n = 1290) were collected over 4 time periods during the summer grazing season from 21 separately managed groups of cattle. Fecal egg counts (FEC) were estimated using generalized estimating equations with a negative binomial distribution with log link function, adjusting for clustering of samples within each herd for each time period. Nematodirus spp. and Trichuris spp. eggs were enumerated separately and were detected in 5.7% (73/1290) and 1.7% (22/1290) of samples, respectively. One or more strongyle-type eggs were detected in 79.5% (1025/1290) of the samples and FEC increased by 2.8 times over the summer grazing season. Interestingly, FEC were ~3.4 times higher on pastures located in dark brown versus brown soil zones, a finding that warrants further investigation.

Evolution and Biogeography of Haemonchus contortus: Linking Faunal Dynamics in Space and Time

History is the foundation that informs about the nuances of faunal assembly that are essential in understanding the dynamic nature of the host-parasite interface. All of our knowledge begins and ends with evolution, ecology and biogeography, as these interacting facets determine the history of biodiverse systems. These components, relating to Haemonchus, can inform about the complex history of geographical distribution, host association and the intricacies of host-parasite associations that are played out in physiological and behavioural processes that influence the potential for disease and our capacity for effective control in a rapidly changing world. Origins and evolutionary diversification among species of the genus Haemonchus and Haemonchus contortus occurred in a complex crucible defined by shifts in environmental structure emerging from cycles of climate change and ecological perturbation during the late Tertiary and through the Quaternary. A history of sequential host colonization associated with waves of dispersal bringing assemblages of ungulates from Eurasia into Africa and processes emerging from ecosystems in collision and faunal turnover defined the arena for radiation among 12 recognized species of Haemonchus. Among congeners, the host range for H. contortus is exceptionally broad, including species among artiodactyls of 40 genera representing 5 families (and within 12 tribes of Bovidae). Broad host range is dramatically reflected in the degree to which translocation, introduction and invasion with host switching, has characterized an expanding distribution over time in North America, South America, southern Eurasia, Australia and New Zealand, coincidental with agriculture, husbandry and global colonization by human populations driven particularly by European exploration after the 1500s. African origins in xeric to mesic habitats of the African savannah suggest that historical constraints linked to ecological adaptations (tolerances and developmental thresholds defined by temperature and humidity for larval stages) will be substantial determinants in the potential outcomes for widespread geographical and host colonization which are predicted to unfold over the coming century. Insights about deeper evolutionary events, ecology and biogeography are critical as understanding history informs us about the possible range of responses in complex systems under new regimes of environmental forcing, especially, in this case, ecological perturbation linked to climate change. A deeper history of perturbation is relevant in understanding contemporary systems that are now strongly structured by events of invasion and colonization. The relaxation of abiotic and biotic controls on the occurrence of H. contortus, coincidental with inception and dissemination of anthelmintic resistance may be synergistic, serving to exacerbate challenges to control parasites or to limit the socioeconomic impacts of infection that can influence food security and availability. Studies of haemonchine nematodes contribute directly to an expanding model about the nature of diversity and the evolutionary trajectories for faunal assembly among complex host-parasite systems across considerable spatial and temporal scales.