Precision, repeatability and representative ability of faecal egg counts in Heterakis gallinarum infected chickens

Evaluation of trace elements in forages and their effect on gastrointestinal parasite burden in grazing sheep

This study was designed to evaluate the trace elements (minerals) in forages fed to sheep and their effect on gastrointestinal parasite burdens. The ultimate objective was to determine the correlation between the burden of gastrointestinal (GI) parasites and the level of trace minerals in sheep serum as a result of the forages they grazed on. A total of 384 faecal samples were collected from sheep in each of the districts (Sialkot and Multan) and examined quantitatively using the McMaster technique. Serum collected from them and plants were pre-treated, and spectrophotometry was used to determine the concentration of trace minerals (Mn, Co, Cu, and Zn). The level of these trace elements differed significantly (P < 0.05) in forages from both districts. In the district of Sialkot, the highest concentrations (mg/Kg) of Zn (38.53 ± 0.16) were found in Cichorium intybus, Cu (41.57 ± 0.07) in Cynodon dactylon, Mn (39.61 ± 0.05) in Parthenium hysterophorus, and Co (1.42 ± 0.03) in Coronopus didymus. In the district of Multan, the highest concentrations (mg/Kg) of Zn (39.43 ± 0.46) were found in Cichorium intybus, Cu (25.76 ± 0.36) in Cynodon dactylon, Mn (34.29 ± 0.53) in Launaea nudicaulis, and Co (1.74 ± 0.08) in Brachiaria raptens. The prevalence of GI parasites in sheep populations in district Sialkot was 34%, while in district Multan, it was 32%. In tehsil Sialkot of district Sialkot, Zn and Cu were significantly (P < 0.05) correlated with eggs per gram (EPG) of faeces, while in tehsil Multan City of district Multan, only Cu was significantly (P < 0.05) correlated with EPG. The potential mechanism behind the role of trace minerals in lowering the burdens of GI parasites requires more investigation. It is recommended that plants with high content of trace minerals should be utilized as part of comprehensive preventive and control strategies against GI parasitism in ruminant animals like sheep.

Comparison of Mini-FLOTAC, Flukefinder and sedimentation techniques for detection and quantification of Fasciola hepatica and Calicophoron daubneyi eggs using spiked and naturally infected bovine faecal samples

BACKGROUND

Fasciolosis (Fasciola hepatica) and paramphistomosis (Calicophoron daubneyi) are two important infections of livestock. Calicophoron daubneyi is the predominant Paramphistomidae species in Europe, and its prevalence has increased in the last 10-15 years. In Italy, evidence suggests that the prevalence of F. hepatica in ruminants is low in the southern part, but C. daubneyi has been recently reported at high prevalence in the same area. Given the importance of reliable tools for liver and rumen fluke diagnosis in ruminants, this study evaluated the diagnostic performance of the Mini-FLOTAC (MF), Flukefinder(R) (FF) and sedimentation (SED) techniques to detect and quantify F. hepatica and C. daubneyi eggs using spiked and naturally infected cattle faecal samples.

METHODS

Briefly, negative bovine faecal samples were artificially spiked with either F. hepatica or C. daubneyi eggs to achieve different egg count levels: 10, 50 and 100 eggs per gram (EPG) of faeces. Moreover, ten naturally infected cattle farms from southern Italy with either F. hepatica and/or C. daubneyi were selected. For each farm, the samples were analysed individually only with MF technique and as pools using MF, FF and SED techniques. Bayesian latent class analysis (LCA) was used to estimate sensitivity and accuracy of the predicted intensity of infection as well as the infection rate in the naturally infected farms.

RESULTS

The outcome of this study showed that the highest number of eggs (F. hepatica and C. daubneyi) recovered was obtained with MF, followed by FF and SED in spiked infected samples at 50 and 100 EPG, while at lower infection levels of 10 EPG, FF gave the best results. Moreover, the sensitivity for all the techniques included in the study was estimated at > 90% at infection levels > 20 EPG for both F. hepatica and C. daubneyi eggs. However, MF was the most accurate of the three techniques evaluated to estimate fluke infection intensity. Nevertheless, all three techniques can potentially estimate infection rate at farm level accurately.

CONCLUSIONS

Optimization and standardization of techniques are needed to improve the FEC of fluke eggs.

Pattern and repeatability of ascarid-specific antigen excretion through chicken faeces, and the diagnostic accuracy of coproantigen measurements as compared with McMaster egg counts and plasma and egg yolk antibody measurements in laying hens

BACKGROUND

A coproantigen enzyme-linked immunosorbent assay (ELISA) has recently been proposed for detecting ascarid infections in chickens. The excretion pattern of ascarid antigens through chicken faeces and the consistency of measurements over the course of infections are currently unknown. This study evaluates the pattern and repeatability of worm antigen per gram of faeces (APG) and compares the diagnostic performance of the coproantigen ELISA with a plasma and egg yolk antibody ELISA and McMaster faecal egg counts (M-FEC) at different weeks post-infection (wpi).

METHODS

Faecal, blood and egg yolk samples were collected from laying hens that were orally infected with a mix of Ascaridia galli and Heterakis gallinarum eggs (N = 108) or kept as uninfected controls (N = 71). Measurements including (a) APG using a coproantigen ELISA, (b) eggs per gram of faeces (EPG) using the McMaster technique and (c) ascarid-specific IgY in plasma and in egg yolks using an ascarid-specific antibody ELISA) were performed between wpi 2 and 18.

RESULTS

Time-dependent significant differences in APG between infected and non-infected laying hens were quantified. At wpi 2 (t₍₁₆₄₎ = 0.66, P = 1.00) and 4 (t₍₁₆₄₎ = -3.09, P = 0.094) no significant differences were observed between the groups, whereas infected hens had significantly higher levels of APG than controls by wpi 6 (t₍₁₆₄₎ =  -6.74, P < 0.001). As indicated by a high overall repeatability estimate of 0.91 (CI = 0.89-0.93), APG could be measured consistently from the same individual. Compared to McMaster and antibody ELISA, coproantigen ELISA showed the highest overall diagnostic performance (area under curve, AUC = 0.93), although the differences were time-dependent. From wpi 6 to 18 coproantigen ELISA had an AUC > 0.95, while plasma IgY ELISA showed the highest diagnostic performance in wpi 2 (AUC = 0.95). M-FEC had the highest correlation with total worm burden, while APG had highest correlations with weights and lengths of A. galli.

CONCLUSION

Ascarid antigen excretion through chicken faeces can be measured with high accuracy and repeatability using a coproantigen ELISA. The antigen excretion increases over time, and is associated with worm maturation, particularly with the size of A. galli. Our results suggest the necessity of complementary use of different diagnostic tools for a more accurate diagnosis of infections.

Prevalence and magnitude of gastrointestinal helminth infections in cage-free laying chickens in Australia

Helminth infections have been re-emerging with the growing popularity of free-range and floor-based chicken production systems. The aim of this study was to determine the prevalence and worm burdens of intestinal helminth infection in cage-free laying chickens in Australia. In an online survey about worm prevalence, a high proportion of respondents reported the detection of Ascaridia galli (77%), followed by tapeworms (69%) and caecal worms (Heterakis gallinarum) (62%), whereas fewer respondents (23%) reported the presence of hair worms (Capillaria spp.) in their flocks. Total worm recovery from 407 laying hens on four farms found that 92.1% of hens harboured one or more helminth parasite with a prevalence of 73 to 100% across farms. Mixed infections were common with 79% of hens harbouring two or more helminth species. The prevalence of nematode species H. gallinarum, A. galli and Capillaria spp. was 87, 82 and 35% respectively. Five cestode species were found with a low individual chicken prevalence (Raillietina tetragona 4.7%, Raillietina echinobothrida 3.2%, Raillietina cesticillus 5.2%, Choanotaenia infundibulum 4.4%, and Hymenolepis cantaniana 4.4%). The hens harboured an average of 71 worms with H. gallinarum having the highest mean burden (45.5 worms/hen) followed by A. galli (22.0 worms/hen), Capillaria spp. (2.7 worms/hen) and cestodes (0.8 worms/hen). The sex ratio (female:male worms) was 1.38:1 for A. galli, and 1.77:1 for H. gallinarum. There was a strong positive correlation between A. galli female worm count and excreta egg count (EECs) (r_s = 0.94, P < 0.0001) and also between total nematode worm count and EEC (r_s = 0.82, P < 0.0001) in individual hens. When investigating intestinal excreta (n = 10) and caecal excreta (n = 10) of 16 chicken flocks the prevalence of infection with ascarid worms in intestinal and caecal excreta was 71 and 78% respectively and 27% prevalence of Capillaria spp. in intestinal excreta with mean EECs of 407, 404, and 18 eggs/g of excreta (EPG), respectively. These results suggest that most chickens kept in free-range or floor production systems are infected with one or more helminth parasite species. Heavy worm infections would likely affect the production performance and welfare of birds with adverse economic impact. Strategic or tactical anthelmintic treatment with effective anthelmintic could reduce this impact.

Implementation of a targeted treatment strategy for the sustainable control of Ascaridia galli infections in laying hens

Background

Ascaridia galli is a widespread problem in cage-free egg production. Sustainable control of nematode infections is a key component in this sector. This study investigates the effect of a treatment strategy against A. galli, aiming to propose a guideline for anthelmintic use on commercial poultry farms.

Methods

A total of eight flocks of laying hens (a-h) from five commercial poultry farms were included in this study. Faecal samples were collected on a biweekly basis starting at 7-13 weeks post-placement (WPP) and processed using the McMaster method to calculate ascarid egg shedding. Flocks were treated after the threshold of 200 eggs per gram of faeces (EPG) was reached.

Results

The highest initial faecal egg count was 6700 EPG at 11 WPP, whereas the lowest was 50 at 8 WPP. The longest delay to detect A. galli was 7 weeks. The lowest and the highest number of treatments were four and six, respectively. The shortest and longest periods between any two treatments were 5 and 22 weeks, respectively.

Conclusions

These results suggest that monitoring for A. galli should start at approximately 7 WPP and should be repeated every 8 weeks until hens are 50 weeks old. Treatment should be given only if moderate to high faecal egg counts are observed. Treatments after this point may be repeated every 8 weeks without eventually performing a faecal test. These findings provide practical support to veterinarians and egg producers dealing with ascarid worm infection in laying hens in their production stage.

Ascaridia galli eggs obtained from fresh excreta, worm uteri or worms cultured in artificial media differ in embryonation capacity and infectivity

Ascaridia galli infection models use eggs isolated from chicken excreta, worm uteri and worms cultured in artificial media. The aim of this study was to compare the infectivity of A. galli eggs isolated from these sources under two infection regimens. A 3 × 2 factorial arrangement was employed to test the infectivity of A. galli eggs from the three sources and two modes of infection (single or trickle infection). One hundred and fifty-six Isa-Brown one day-old cockerels randomly assigned to the six treatment groups (n = 26) were orally infected with embryonated A. galli eggs obtained from the three A. galli egg sources (worm uteri, excreta or eggs shed in vitro) administered either as single dose of 300 eggs at one day-old or trickle infected with 3 doses of 100 eggs over the first week of life. Twenty-two negative control birds remained uninfected. Eggs obtained from cultured worms or excreta exhibited a higher embryonation capacity (P = 0.003) than eggs obtained from worm uteri. There were higher worm establishment (infectivity) rates from embryonated eggs originating from cultured worms and worm uteri compared with eggs obtained from fresh excreta (P < 0.0001). Trickle infection resulted in a significantly higher total worm burden (P = 0.002), establishment rate (P = 0.002) and excreta egg counts (EEC, P = 0.025) than single infection. Worm length was greater in birds infected with embryonated eggs from excreta than from uteri or cultured worms (P < 0.0001). However, mode of infection did not affect worm length (P = 0.719) and weight (P = 0.945). A strong significant positive linear correlation was observed between EECs and female worm counts at 12 weeks of post infection sampling (r = 0.75; P < 0.0001). Body weight of birds was negatively correlated with both worm burden (r = - 0.21; P < 0.01) and EEC (r = - 0.20; P < 0.05) at 12 weeks post infection. In conclusion, our results show that eggs shed by cultured worms or isolated from worm uteri had greater infective capacity than eggs harvested from excreta and that trickle rather than bolus infection resulted in higher worm establishment. These factors should be taken into account when considering artificial infection protocols for A. galli.

Comparison of the Modified McMaster and Mini-FLOTAC methods for the enumeration of nematode eggs in egg spiked and naturally infected chicken excreta

Excreta egg counting techniques are used for indirectly estimating the magnitude of gastrointestinal nematode infection in live animals. The aim of this study was to optimise laboratory and field sampling methods for routine monitoring of nematode infections in chickens by evaluating the sensitivity, accuracy, and precision of the Modified McMaster (MM) and Mini-FLOTAC (MF) methods using laying chicken excreta samples spiked with estimated true numbers of eggs (Experiment 1 = 5-1500 EPG (eggs/g); Experiment 2 = 5-500 EPG) without and with operator effects, respectively or using individual fresh excreta (n = 230) and fresh floor excreta (n = 42) from naturally infected free-range layer farms. The Coefficient of Variation (CV) was assessed within and between operators and the time spent on sample preparation and counting was also evaluated. MF was more sensitive than MM at ≤ 50 EPG level but not above this while MM had a significantly higher egg recovery rate than MF for ≥ 50 EPG levels (MM = 89.7 %, MF = 68.2 %; P < 0.0001). Operator factors did not have a significant effect (P = 0.358-0.998) on egg counts across methods and EPG levels. The CV between replicates of the MM and MF methods for ≥ 50 EPG was 43.4 and 36.5 %, respectively. The inter-observer CV of the MM and MF methods for ≥ 50 EPG levels was 63.8 and 44.3 % respectively. When the naturally infected free-range layers which were individual caged for excreta sampling, the proportion of samples positive for MM and MF were 91.7 and 96.5 %, respectively (P = 0.023). MM resulted in significantly (P = 0.029) higher excreta egg counts (604) than MF (460) with the difference between methods greatest at higher EPG levels. Fresh floor excreta (pooled or individual) and individual caged chicken excreta did not have significant effect on egg counts (P = 0.274). The total time taken for sample preparation and egg counting was significantly lower using the MM method (4.3-5.7 min) than the MF method (16.9-23.8 min) (P < 0.0001). In conclusion, MM was more accurate than MF, particularly at higher EPG levels, but slightly less precise and sensitive, particularly at low EPG levels, while taking less than 25 % of the laboratory time per sample. Our observations indicate that the MM method is more appropriate for rapid diagnosis of chicken nematodes in the field. Pooled fresh floor excreta samples would be sufficient to indicate infection level in free range farms.

In addition to birds' age and outdoor access, the detection method is of high importance to determine the prevalence of gastrointestinal helminths in laying hens kept in alternative husbandry systems

The prevalence of gastrointestinal helminths was investigated in sixty-six commercial non-caged layer flocks. Twenty-nine flocks were housed indoors in aviaries or floor systems, nineteen flocks were kept in conventional free-range systems with outdoor access, and eighteen flocks in organic free-range systems. Flocks were investigated at end of rearing (mean age 17 weeks), peak of egg production (mean age 38 weeks) and before slaughter (mean age 74 weeks). Four different methods were applied to determine worm infestation. During necropsies, worm infestations were recorded and mucosal scrapings were evaluated for the presence of worm eggs. Faecal samples from each flock were investigated by simple flotation method and McMaster counting technique. No gastrointestinal helminths were found in pullets. During production, 87.9 % of the layer flocks were infected with at least one nematode species at the peak of production. The prevalence further increased significantly up to 98.5 % at the end of production (p=0.05). This increase could be ascribed mainly to infections with Ascaridia (A.) galli and/or Heterakis (H.) gallinarum which were most prevalent in all husbandry systems. Furthermore, their prevalence increased significantly with the age of birds (p=0.023; p < 0.001). With regard to the husbandry system, the prevalence of Capillaria spp. was significantly higher in flocks from outdoor systems compared to flocks that were kept indoors. Cestodes were only detected at the end of production with a prevalence of 15.2 % and significantly more flocks with access to outdoor run were found positive. Interestingly, H. gallinarum was found with a high prevalence indoor and in outdoor systems. Anthelminthic treatment did not impact the prevalence of nematode infections. Comparing four different methods for the detection of helminths it was revealed that their efficiencies varied depending on the worm species. Overall, the simple flotation method was superior to detect A. galli and Capillaria spp. This method proved also very efficient for the detection of H. gallinarum but the additional evaluation of the worm infestation during necropsy increased the level of prevalence. Cestodes were mainly found during necropsies when the worm infestation was evaluated. The detection of parasite eggs in mucosal scrapings from the intestines was the least effective method for all helminths. These findings lead to the recommendation to combine faecal investigations with an evaluation of the worm infestation during necropsy of at least five birds.

Global and regional prevalence of helminth infection in chickens over time: a systematic review and meta-analysis

Gastrointestinal helminth parasites are a concern for the poultry industry worldwide as they can affect the health, welfare, and production performance. A systematic review of the prevalence over time in different countries may improve our understanding of gastrointestinal helminthiasis in chickens and subsequently lead to improved poultry health. The aim of this systematic review and meta-analysis was to provide an overview of the published information regarding the epidemiology and the diagnostic approaches of chicken helminth infection. Six databases were searched for studies, and a total of 2,985 articles published between 1942 and 2019 were identified and subsequently screened for eligibility using title or abstract and full text assessment, resulting in 191 publications to be used in the study. Postmortem diagnostics (73.8%) and the flotation technique (28.8%) were commonly used to detect helminth infections with a pooled prevalence of 79.4% ranging from 4 to 100%. More than 30 helminth species in chicken populations were identified including Ascaridia galli (35.9%), Heterakis gallinarum (28.5%), Capillaria spp. (5.90%), and Raillietina spp. (19.0%) being the most prevalent. The reported prevalence of helminth infection decreased over time in developing countries while it increased in the developed world. Chicken kept in backyard and free-range systems had a markedly higher pooled prevalence of helminth infection (82.6 and 84.8%, respectively) than those housed in cage production systems (63.6%). This may indicate the need for more rigorous control and prevention measures in free-range and backyard production systems using regular deworming coupled with access to early and accurate diagnosis allowing for early intervention.

Accuracy and precision of McMaster and Mini-FLOTAC egg counting techniques using egg-spiked faeces of chickens and two different flotation fluids

Faecal egg counting techniques (ECTs) are useful tools for assessing anthelmintic efficacy and selecting hosts resistant to parasite infection. McMaster (MM) is one of the most commonly used ECTs, but it suffers from low sensitivity and precision. Mini-FLOTAC (MF) has been proposed to replace MM, but so far has not been evaluated for gastro-intestinal nematode infections in chickens. This study compared sensitivity, precision, and accuracy of MM and MF with two trials using egg-spiked faecal samples ranging from 50-1250 eggs per gram of faeces (EPG). In addition, effects of two flotation fluids with different specific gravities (SG), namely salt (SG = 1.20) and sucrose solutions (SG = 1.32), on accuracy and time-spent for both ECTs were evaluated. Overall sensitivity based on the composite reads across all EPG-levels was 97.1 % for MM and 100 % for MF. MF was, however, more sensitive (P = 0.003) or tended to (P = 0.087) be more sensitive than MM at only the lowest EPG-level (i.e. 50 EPG) using one of the duplicate reads, whereas there was no significant difference at any EPG-level using composite reads. Overall average precision of MF (79.5 %) was higher (P < 0.001) than that of MM (63.4 %) across all EPG-levels. Precision of MM increased from 22 to 87 % with increasing EPG-levels from 50-1250 EPG. Corresponding precision estimates for MF ranged from 76 to 91 %. Overall recovery rate of MM (74.6 %) was significantly higher (P < 0.001) than that of MF (60.1 %). There was no significant difference in recovery rate of spiked-eggs among different EPG-levels (P = 0.833). Recovery rate of MM ranged from 64 % to 79 % across different EPG-levels, while it ranged from 54 % to 64 % with MF without an interaction between ECT and EPG-level (P = 0.701). It took more time (P < 0.001) to process (prepare and read) samples with MF than with MM using the same flotation fluid. The sugar solution tended to (P = 0.100) increase egg-recovery with both ECTs, while increasing (P < 0.001) time-spent for processing the samples. Our data collectively suggest that MM is less sensitive than MF only at around minimum detection level of MM when using unrepeated reads. We conclude that McMaster is faster, relatively more accurate but less precise than Mini-FLOTAC. The sugar solution with higher SG increases accuracy of both techniques at the expense of increased labour time.

Cattle gastrointestinal nematode egg-spiked faecal samples: high recovery rates using the Mini-FLOTAC technique

Background

Faecal egg count (FEC) techniques are commonly used to detect gastrointestinal nematodes (GINs) in cattle and to determine anthelmintic efficacy/resistance through the faecal egg count reduction test (FECRT). Mini-FLOTAC is one of the techniques recommended for a standardised FEC/FECRT of helminth eggs in cattle. However, only one paper evaluated the recovery rate of GIN eggs by Mini-FLOTAC (compared to McMaster and modified-Wisconsin method) in cattle, using only a level of contamination of 200 eggs per gram (EPG) of faeces and using GIN eggs collected from goat faeces to spike faecal samples from cattle. To further study the recovery rate of GIN eggs from cattle faeces, this study was conducted in two laboratories, one in Belgium and one in Italy to evaluate the sensitivity, accuracy, precision and reproducibility of the Mini-FLOTAC and McMaster techniques (at two reading levels: grids and chambers) for the detection of GIN eggs in spiked bovine faecal samples.

Methods

In both countries, spiked cattle faecal samples with five different levels of egg contamination (10, 50, 100, 200 and 500 EPG) of GINs were used. The study was performed in both laboratories by the same expert operator and using the same standard operating procedures (SOPs) for the Mini-FLOTAC and McMaster techniques. Sensitivity, accuracy and precision were calculated for each technique and for each level of contamination. Statistical analyses were performed to evaluate differences in performance between the two techniques.

Results

Mini-FLOTAC had a higher sensitivity (100% at all EPG levels for Mini-FLOTAC vs 0–66.6% for McMaster chambers and grids at levels< 100 EPG), a higher accuracy (98.1% mean value for Mini-FLOTAC vs 83.2% for McMaster grids and 63.8% for McMaster chambers) and a lower coefficient of variation (10.0% for Mini-FLOTAC vs 47.5% for McMaster grids and 69.4% for McMaster chambers) than McMaster. There was no significant difference in the recovery of GIN eggs between the two studies performed in Belgium and in Italy.

Conclusions

The high GIN egg recovery rate detected by Mini-FLOTAC and the similar results obtained in Belgium and in Italy indicated that the diagnostic performance of a FEC technique was not dependent on the laboratory environment.

Analysis of antibody levels in egg yolk for detection of exposure to Ascaridia galli parasites in commercial laying hens

Ascaridia galli is one of the most abundant nematode parasites in poultry. A. galli infections can significantly impact the profitability of egg farms and have negative implications for bird health and welfare. The main objectives of this study were to determine whether A. galli specific antibodies in egg yolks can be used to detect prior or current exposure to A. galli in laying hens, and to distinguish between eggs obtained from caged and free-range hens. Twenty-two laying hen flocks from different production systems (10 free-range, 2 barn-housed, and 9 caged flocks) were enrolled in the study. An in-house enzyme-linked immunosorbent assay was used to analyze levels of A. galli specific antibodies in yolk. The numbers of A. galli eggs in hen excreta were also determined in a subset of farms. Free-range flocks had higher and also more variable levels of anti-A. galli antibodies in the egg yolk compared to those of the cage flocks (0.50 ± 0.39 vs. 0.16 ± 0.13 OD units) (P < 0.001). Results also confirmed that excreta from free-range and barn-housed flocks contained higher numbers of A. galli eggs than did excreta from caged flocks in which no A. galli eggs were detected. In conclusion, analysis of anti-A. galli antibodies in the egg yolk can be used to detect worm exposure in commercial layer flocks. However, the method used in this study cannot be used in isolation to distinguish between eggs from cage and free-range production systems as anti-A galli antibodies were detected in egg yolk samples from all production systems, and the range of antibody levels overlapped between production systems.

Diurnal variation in egg excretion by Heterakis gallinarum

Periodicity in nematode egg excretion may be of evolutionary origin as it can favour dispersal of the eggs in the environment. We investigated whether egg excretion by Heterakis gallinarum shows a repeatable pattern of periodicity. The faecal egg concentration and total number of eggs excreted within 4-h intervals were significantly affected by the sampling time within 1 day, but remained unaffected by the sampling day or interaction effects. By contrast, the total number of eggs excreted within 24 h did not differ among the 4 days of the study, collectively indicating repeatable egg excretion patterns. Both host feces and parasite egg excretion increased from night to late afternoon, followed by a decrease in the evening, resulting in higher egg excretion during daytime than the dark period. Feces excretion and worm fecundity showed overlapping diurnal rhythms with similarly timed phases, suggesting the existence of synchronicity between the host feces and nematode egg excretion patterns. We conclude that egg excretion by H. gallinarum is synchronized with host feces excretion and is higher during the daytime than during the dark period. This overlaps with the maximum activity of the day-active host and allows a maximal dispersal of the eggs in the environment.

A comprehensive evaluation of an ELISA for the diagnosis of the two most common ascarids in chickens using plasma or egg yolks

BACKGROUND

Classical faecal egg counts (FEC) provide less reliable diagnostic information for nematode infections in chickens. We developed an ELISA based on Ascaridia galli antigens and tested two hypotheses, as follows: (i) IgY antibodies developed against A. galli will also be useful to identify Heterakis gallinarum infections, and (ii) circulating antibodies stored in egg yolks are as good as plasma samples, so a non-invasive diagnosis is possible. The aim of this study, therefore, was to compare the diagnostic accuracy of the ELISA system with FEC, using both plasma and egg yolks from experimentally infected hens. In addition, naturally infected animals were evaluated to validate the assay.

RESULTS

The assay quantified large differences (P < 0.001) in plasma or in egg-yolk IgY concentrations between infected and uninfected animals in two experiments, each performed with either of the nematode species. The assay performed with high accuracy as quantified with the area under the ROC curve (AUC) values of > 0.90 for both nematodes using either plasma or egg yolks. Sensitivity of the assay was 94 and 93% with plasma and egg yolk samples, respectively, whereas FEC yielded in a sensitivity of 84% in A. galli experiment. Total test accuracy of the assay with plasma samples (AUC = 0.99) tended to be higher (P = 0.0630) than FEC (AUC = 0.92) for A. galli, while the assay with either sample matrix performed similar to FEC (AUC ≥ 0.91) for H. gallinarum. Among the three tests, the FECs correlated better with A. galli burden than the ELISA. Although 90% of naturally infected hens were correctly identified by the ELISA, 45% of the infected hens tested negative with FEC, indicating the validity of the higher test accuracy of the ELISA.

CONCLUSIONS

Antigens of A. galli can be used successfully to identify H. gallinarum-infected animals, indicating that chickens develop cross-reactive antibodies against the two closely related species. Egg yolks are as informative as plasma samples, so that animal welfare-friendly sampling is possible. Although the assay with plasma samples reveals qualitative information of higher quality than FECs on the infection status of naturally infected birds, the latter is still a better tool to assess the intensity of A. galli but not of H. gallinarum infections.

Embryonation ability of Ascaridia galli eggs isolated from worm uteri or host faeces

Experimental infection models for Ascaridia galli rely on the use of eggs isolated either directly from worm uteri or from host faeces. We investigated whether A. galli eggs isolated from the two sources differ in their embryonation ability. A. galli eggs originating from 12 worm infrapopulations were isolated both from faeces of the living host (faecal eggs) and directly from worm uteri after host necropsy (uterine eggs). The isolated eggs from each infrapopulation and source were incubated in Petri dishes (n=24) containing a potassium-dichromate (0.1%) medium for 28 days (d) at room temperature. Starting from the day of egg isolation (d0), in ovo larval development was evaluated every second day by examining morphological characteristics of 200 eggs/petri dish. A total of 72,000 eggs were classified into undeveloped, early development, vermiform or fully embryonated stages. Isolation procedures caused similar damage to uterine and faecal eggs (2.2% and 0.5%, respectively; P=0.180). The first sign of in ovo embryonic development in faecal eggs (7%) was observed during the 24-h period when faeces were collected. On d28, a higher percentage of uterine eggs remained undeveloped when compared with faecal eggs (58.6% vs 11.0%; P<0.001). Although a higher (P<0.001) percentage of faecal eggs entered both the early developmental and vermiform stages, which took place primarily within the first two weeks of incubation, there was no time-shift between the development of faecal and uterine eggs. Starting from day 10, higher (P<0.05) percentages of faecal eggs completed embryonation compared with uterine equivalents. Eggs from both sources reached a plateau of embryonation by the end of 2nd week of incubation, with faecal eggs having a greater than two-fold higher embryonation ability. Cumulative mortality was higher in uterine eggs (14.3%) than in faecal eggs (0.2%). We conclude that faecal eggs have a higher embryonation ability than uterine eggs possibly due to maturation differences.

Density related effects on lifetime fecundity of Heterakis gallinarum in chickens

Background

Density related effects, both inverse density- and density-dependent, contribute to regulating population dynamics of parasites. We investigated whether density related effects are directly controlling lifetime fecundity of Heterakis gallinarum.

Methods

Daily total numbers of H. gallinarum eggs in faeces samples (N = 1365) from chickens (N = 39) were quantified starting from 3 weeks (wk) post-infection (p.i.). The birds were necropsied 8 wk p.i., and intensity and demographic characteristics of infrapopulations were determined. Density related effects on cumulative egg excretion (CEE), lifetime fecundity and worm length were investigated with a segmented regression analysis.

Results

For CEE, lifetime fecundity and female worm length, we determined highly similar parasite intensity thresholds (52–54 worms), which separated infrapopulations for influences of inverse density- and density dependence. CEE increased as parasite intensity increased up to an intensity of 52 worms. After this threshold, the relationship followed more of a horizontal line indicating impaired worm fecundity at higher parasite intensities. Lifetime fecundity was enhanced linearly in infrapopulations with up to 54 worms, but thereafter decreased gradually with increasing infrapopulation size. Female worm length increased linearly with elevating parasite intensity up to a threshold of 54 worms and thereafter declined with a rate of -0.014 mm for each additional worm. Lifetime fecundity and female worm length did not significantly differ between infrapopulations below and above the thresholds (P > 0.05). Lifetime fecundity was positively associated with the percentage of male worms (r = 0.44; P < 0.001), but negatively with absolute deviation from the theoretically expected sex-ratio in the infrapopulations (r = -0.56; P = 0.005). These relationships were stronger in infrapopulations below the threshold (r = 0.51 and -0.61, respectively), and were not significantly different from zero in the infrapopulations above the threshold (P > 0.05).

Conclusions

Egg production of H. gallinarum is regulated by the effects of both inverse density- and density-dependent mechanisms, which result in similar average lifetime fecundity below or above intensity thresholds. In infrapopulations below the intensity thresholds, inverse density dependence effects on lifetime fecundity appear to result partly from sex-ratio fluctuations and impaired mating success of the nematode.

Reducing sampling error in faecal egg counts from black rhinoceros (Diceros bicornis)

Faecal egg counts (FECs) are commonly used for the non-invasive assessment of parasite load within hosts. Sources of error, however, have been identified in laboratory techniques and sample storage. Here we focus on sampling error. We test whether a delay in sample collection can affect FECs, and estimate the number of samples needed to reliably assess mean parasite abundance within a host population. Two commonly found parasite eggs in black rhinoceros (Diceros bicornis) dung, strongyle-type nematodes and Anoplocephala gigantea, were used. We find that collection of dung from the centre of faecal boluses up to six hours after defecation does not affect FECs. More than nine samples were needed to greatly improve confidence intervals of the estimated mean parasite abundance within a host population. These results should improve the cost-effectiveness and efficiency of sampling regimes, and support the usefulness of FECs when used for the non-invasive assessment of parasite abundance in black rhinoceros populations.

A simple method to count total faecal Capillaria worm eggs in racing pigeons (Columba livia)

Capillaria columbae and C. longicollis are fine threadworms found in racing pigeons' small intestines that produce a characteristic lemon shaped bipolar egg. Clinically, capillariasis in racing pigeons can present as severe illness and it has been suggested that worms may affect race performance. A major aim of this study was to validate a cheap, simple to perform flotation technique for counting Capillaria worm eggs in racing pigeon droppings. Trials using reference samples of pigeon droppings laced with 348, 275 and 129 Capillaria eggs per gram, found a typical flotation method based on the modified Wisconsin technique to be inaccurate at counting worm eggs. The main sources of error were due to the loss of eggs in the faecal discard and insufficient flotation time. A new technique, using 0.15 g sample size and 8h flotation time resulted in significantly improved test accuracy. On average the new technique recovered 93% of eggs from reference samples with 129-348 epg concentration, recovering 197 times more eggs than the modified Wisconsin technique. Typical percentage error, as a measure of absolute reliablility, was 10% for the new technique and 50% for the modified Wisconsin technique. The regression line on a test-retest series of samples over a range of egg counts from 0 to 573 epg had a gradient of 0.96 (y=0.96x+6.28; r(2)=0.8408) for the new technique and 0.54 (y=0.54x+0.06; r(2)=0.4249) for the modified Wisconsin technique. The Pearson product moment correlations of the new technique and the modified Wisconsin technique were 0.92 and 0.65 respectively. As measures of relative reliability both the gradient of the regression line and the Pearson product moment correlation further suggested better repeatability of the new technique. It was concluded that the new technique would be an appropriate quantitative method of assessing worm egg burdens in racing pigeons.

Analysis of the accuracy and precision of the McMaster method in detection of the eggs of Toxocara and Trichuris species (Nematoda) in dog faeces

The aim of this study was to determine the accuracy and precision of McMaster method with Raynaud's modification in the detection of the eggs of the nematodes Toxocara canis (Werner, 1782) and Trichuris ovis (Abildgaard, 1795) in faeces of dogs. Four variants of McMaster method were used for counting: in one grid, two grids, the whole McMaster chamber and flotation in the tube. One hundred sixty samples were prepared from dog faeces (20 repetitions for each egg quantity) containing 15, 25, 50, 100, 150, 200, 250 and 300 eggs of T. canis and T. ovis in 1 g of faeces. To compare the influence of kind of faeces on the results, samples of dog faeces were enriched at the same levels with the eggs of another nematode, Ascaris suum Goeze, 1782. In addition, 160 samples of pig faeces were prepared and enriched only with A. suum eggs in the same way. The highest limit of detection (the lowest level of eggs that were detected in at least 50% of repetitions) in all McMaster chamber variants were obtained for T. canis eggs (25-250 eggs/g faeces). In the variant with flotation in the tube, the highest limit of detection was obtained for T. ovis eggs (100 eggs/g). The best results of the limit of detection, sensitivity and the lowest coefficients of variation were obtained with the use of the whole McMaster chamber variant. There was no significant impact of properties of faeces on the obtained results. Multiplication factors for the whole chamber were calculated on the basis of the transformed equation of the regression line, illustrating the relationship between the number of detected eggs and that of the eggs added to the'sample. Multiplication factors calculated for T. canis and T. ovis eggs were higher than those expected using McMaster method with Raynaud modification.

The role of culture media on embryonation and subsequent infectivity of Capillaria obsignata eggs

This study investigated whether infectivity of Capillaria obsignata eggs depends on media culture used for embryonation. Intact female worms were kept in one of following four media: 0.5 % formalin, 2 % formalin, 0.1 % potassium dichromate and 0.1 N sulfuric acid. Embryonation rates of the eggs were quantified either daily in intact females for 16 days, or weekly in disrupted females. Infectivity of the embryonated eggs was tested through an experimental infection of chickens with a single dose of 250 eggs/ bird. The vast majority of the eggs (>82 %) in the first two thirds of the uteri was able to complete embryonation, irrespective of the culture media used for incubation. However, only 32.6 % of total eggs could be harvested after disruption of the intact females. Embryonation rates of the eggs from disrupted worms were different among four culture media, with 0.1 N sulfuric acid resulting in the highest embryonation rate (44.2 %). All the experimentally infected birds harboured mature worms, with varying establishment rates depending on the culture media (P < 0.001). Incubation of the eggs in potassium dichromate 0.1 % resulted in a lower (P < 0.001) establishment rate (10.2 %) when compared with formalin (70.5 and 47.9 % for concentrations at 0.5 and 2 %, respectively) or with 0.1 N sulfuric acid (57.5 %). It can be concluded that most of the eggs in first two thirds of the uteri in the intact females have the potential to complete embryonation without being influenced by the culture media. However, disruption of the intact females results in lower number of harvestable embryonated eggs, with a considerable variation due to culture media used. With the exception of 0.1 % potassium dichromate, any of the three media, particularly 0.1 N sulfuric acid, can be suggested for embryonation of C. obsignata eggs.

The effects of dietary non-starch polysaccharides on Ascaridia galli infection in grower layers

This study examined whether Ascaridia galli infection can be controlled by dietary non-starch polysaccharides (NSP) in chickens. One-day-old chicks were fed either a basal diet (CON) or CON plus insoluble NSP (I-NSP), or CON plus soluble NSP (S-NSP) for 11 weeks. Three weeks later, birds from half of each feeding group were inoculated with 250 embryonated eggs of A. galli, and slaughtered 8 weeks post-infection to determine worm counts. Both NSP diets, particularly S-NSP, increased prevalence of infection (P<0·05) and worm burden (roughly +50%) of the birds (P<0·001). A. galli infection caused a less efficient (P=0·013) feed utilization for body weight gain (BWG) resulting in lower body weights (P<0·001) irrespective of type of diet consumed. NSP-fed birds, particularly those on I-NSP, consumed more (+8%) feed per unit BWG and showed retarded (P<0·001) BW development compared to CON-fed birds. Intracaecal pH was lowered by S-NSP (P<0·05). Both NSP diets increased the volatile fatty acids pool size in caeca (P<0·001) with S-NSP exerting a greater effect (+46%) than I-NSP (+24%). It is concluded that both NSPs supplemented diets alter gastrointestinal environment in favour of the nematode establishment, and thus have no potential for controlling A. galli infection in chickens.