World Association for the Advancement of Veterinary Parasitology (WAAVP) guidelines for evaluating the effectiveness of anthelmintics in chickens and turkeys

Evaluation of anthelmintic efficacy of ethanolic leaf extract of Juglans regia L. on Ascaridia galli: a comprehensive in vitro and in vivo study

Anthelmintic resistance in livestock animals has been spreading across the world in prevalence and severity. As a result, researchers are exploring alternative strategies to combat this issue, and one promising avenue is the utilization of medicinal plants. This study aims to investigate the anthelmintic efficacy of the crude ethanolic extract (CEE) derived from the leaves of Juglans regia against one of the most detrimental nematode parasites affecting poultry, namely Ascaridia galli (A. galli). For the in vitro studies, adult A. galli worms were collected from the naturally infected chickens and the efficacy of CEE was measured at the concentration of 25, 50, and 100 mg/ml using adult worm motility inhibition (WMI) assay. In addition, levamisole (0.55 mg/ml) was used as the positive control. Likewise, Phosphate buffered saline (PBS) was used as the negative control. For the in vivo studies, CEE of J.regia at the doses of 500, 1000, and 2000 mg/kg were evaluated in chickens experimentally infected with A. galli. The anthelmintic efficacy was monitored using faecal egg count reduction (FECR) and worm count reduction (WCR) assays. In vitro studies revealed significant (P < 0.001) anthelmintic effects of CEE of J.regia on the motility of A. galli worms at different hours post-exposure. At the concentration of 100 mg/ml, CEE resulted in 96.5% inhibition of worm motility at 24 h post-exposure. While the synthetic anthelmintic drug, levamisole caused the highest inhibition of worm motility (100%) at the same time period. The in vivo anthelmintic activity of CEE of J. regia demonstrated a maximum effect on day 14 post-treatment by inducing 67.28% FECR and 65.03% WCR. We observed no significant difference (P > 0.05) in worm counts between the negative control group and the chickens treated with CEE at the dosage of 500 mg/kg. Together, the results of the present study suggest that CEE of J. regia leaves possess anthelmintic properties and could be a potential source of novel anthelmintic compounds for controlling helminth parasites.

Anthelmintic Activity of Saussurea costus (Falc.) Lipsch. Against Ascaridia galli, a Pathogenic Nematode in Poultry: In Vitro and In Vivo Studies

AIM OF THE STUDY

The growing resistance of helminth parasites to currently available commercial anthelmintic drugs, combined with apprehensions regarding detrimental chemical residues in livestock products, has sparked an interest in exploring medicinal plants as an alternative strategy for treating helminthiasis. As a result, this study was designed to investigate the anthelmintic activity of crude methanolic extracts (CME) of Saussurea costus root on Ascaridia.galli, a pathogenic nematode of poultry.

MATERIALS AND METHODS

In vitro, the anthelmintic effect of Saussurea costus root was evaluated in comparison to commercial anthelmintic, levamisole on the adult nematode parasites, A.galli using worm motility inhibition (WMI) test. The CME of S.costus was also evaluated for in vivo anthelmintic activity in chickens experimentally infected with Ascaridia galli. For the in vivo study, one hundred-day-old chickens were orally infected with embryonated eggs of A. galli worms. The efficacy of the plant extract as an anthelmintic was assessed through two tests: faecal egg count reduction (FECR) test and worm count reduction (WCR) test. The study investigated three distinct doses of plant extract under in vivo setup: 500 mg kg-1 body weight (bw), 1000 mg kg-1 bw, and 2000 mg kg-1 bw.

RESULTS

In vitro, all the tested concentrations of S.costus (25 mg/ml, 50 mg/ml, and 100 mg/ml) showed a significant (P < 0.001) anthelmintic effects on live adult A. galli worms in terms of inhibition of worm motility at different hours post-treatment. At the highest concentration of the extract, we observed worm motility inhibition of 100% at 24 h post-exposure. On day 14 post-treatment, all birds were slaughtered, and adult A. galli worms were subsequently retrieved from their small intestines. Birds treated with CME extract of S. costus root exhibited a significant (P < 0.001) reduction in faecal egg count. However, the administration of the extract at the dosage of 500 mg kg-1bw to the birds did not reveal any significant (P > 0.05) differences in the worm count compared to the negative control group. The CME of S. costus at a dose of 2000 mg kg-1bw showed the highest anthelmintic activity by inducing 83.10% FECR and 76.47% WCR.

CONCLUSION

In conclusion, the root extract of S. costus has a promising anthelmintic activity on A. galli as demonstrated by the results of the present experiment.

1H-NMR based-metabolomics reveals alterations in the metabolite profiles of chickens infected with ascarids and concurrent histomonosis infection

BACKGROUND

Gut infections of chickens caused by Ascaridia galli and Heterakis gallinarum are associated with impaired host performance, particularly in high-performing genotypes. Heterakis gallinarum is also a vector of Histomonas meleagridis that is often co-involved with ascarid infections. Here, we provide a first insight into the alteration of the chicken plasma and liver metabolome as a result of gastrointestinal nematode infections with concomitant histomonosis. 1H nuclear magnetic resonance (1H-NMR) based-metabolomics coupled with a bioinformatics analysis was applied to explore the variation in the metabolite profiles of the liver (N = 105) and plasma samples from chickens (N = 108) experimentally infected with A. galli and H. gallinarum (+H. meleagridis). This was compared with uninfected chickens at different weeks post-infection (wpi 2, 4, 6, 10, 14, 18) representing different developmental stages of the worms.

RESULTS

A total of 31 and 54 metabolites were quantified in plasma and aqueous liver extracts, respectively. Statistical analysis showed no significant differences (P > 0.05) in any of the 54 identified liver metabolites between infected and uninfected hens. In contrast, 20 plasma metabolites including, amino acids, sugars, and organic acids showed significantly elevated concentrations in the infected hens (P < 0.05). Alterations of plasma metabolites occurred particularly in wpi 2, 6 and 10, covering the pre-patent period of worm infections. Plasma metabolites with the highest variation at these time points included glutamate, succinate, trimethylamine-N-oxide, myo-inositol, and acetate. Differential pathway analysis suggested that infection induced changes in (1) phenylalanine, tyrosine, and tryptophan metabolism, (2) alanine, aspartate and glutamate metabolism; and 3) arginine and proline metabolism (Pathway impact > 0.1 with FDR adjusted P-value < 0.05).

CONCLUSION

In conclusion, 1H-NMR based-metabolomics revealed significant alterations in the plasma metabolome of high performing chickens infected with gut pathogens-A. galli and H. gallinarum. The alterations suggested upregulation of key metabolic pathways mainly during the patency of infections. This approach extends our understanding of host interactions with gastrointestinal nematodes at the metabolic level.

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.

Pumpkin seeds, lemongrass essential oil and ripleaf leaves as feed additives for Ascaridia galli infected laying hens

Abstract

The present study was performed to evaluate the in vivo efficiency of Curcurbita pepo (pumpkin) seeds, Cymbopogon citratus (lemongrass) essential oil and Plantago lanceolata (ripleaf) leaves against helminth infections in laying hens. In the first experiment, 75 Lohmann LSL Classic hens naturally infected with Ascaridia galli were assigned to groups of five; groups were randomly assigned to one of three treatments with five replicates each (untreated control; lemongrass oil: 1 g/bird/day; pumpkin seeds: 10 g/bird/day). Feed consumption and egg production were continuously recorded, individual faecal egg counts were determined weekly, and E. coli and Lactobacillus spp. three times during the experimental period of 29 days. After slaughter, intestinal worms were counted and sexed. Pumpkin improved feed conversion as compared to the control (p = 0.008) and to lemongrass (p = 0.021); no treatment effect on any other parameter was found.

In the second experiment, 75 LSL pullets were artificially infected with 3 × 200 A. galli eggs, randomly divided into groups of five and assigned to one of three treatments (untreated control, lemongrass oil: 1 g/bird/day; ripleaf: 5% of ration). After 109 days of sampling as described above, hens were slaughtered and worm burdens determined. Performance of the animals did not change regardless of the treatment and none of the treatments resulted in changes of the microbiological and parasitological parameters. In conclusion, with the exception of improved feed conversion in the pumpkin group, no positive nor negative effects of the additives on performance, parasitological and microbiological parameters of naturally and artificially A. galli infected laying hens were observed.

A copro-antigen ELISA for the detection of ascarid infections in chickens

A reliable method of diagnosing the most prevalent helminth infections in chickens is vital for developing effective control strategies. Ascaridia galli and Heterakisgallinarum are phylogenetically close nematode species that can elicit the development of cross-reactive antibodies in chickens. Therefore, an enzyme-linked immunoassay (ELISA) based on Ascaridia galli antigens in faeces of chickens to detect and quantify infections with both A. galli and H. gallinarum was developed. The ELISA utilised polyclonal antibodies that were obtained from rabbits immunised with soluble antigens isolated from A. galli. In two separate experiments, chickens were kept as uninfected controls or were orally infected with either 100 or 1000 of embryonated eggs of A. galli or H.gallinarum. Faecal samples were collected after 28-30 weeks post-infection. The ELISA was then used to quantify the concentration of soluble worm antigens in faecal samples, i.e., the amount of antigen per gram faeces, APG. The APG from infected chickens was significantly higher than non-infected groups in both experiments (P 0.001). Both 100 and 1000 infection dose groups were not significantly different (P = 0.999) in the experiment with H. gallinarum, whereas in the experiment with A. galli, APG was significantly higher in the 1000 infection group (P 0.001). A receiver operation characteristics (ROC) analysis that evaluates the qualitative performance of diagnostics tests was used to calculate the assay parameters within each mono-infection experiment. The result showed that the assay had a high diagnostics accuracy with an area-under-curve (AUC) of 0.99 in detecting infection in A. galli infected chickens and a moderate-high accuracy (AUC = 0.89) in birds infected with H. gallinarum. The diagnostic sensitivity and specificity of the assay at the optimal cut-off point equivalent to Youden index were 93% and 100% for detecting infections in A. galli experiment and 85% and 92% in H. gallinarum experiment, respectively. The correlation between faecal antigen concentration and all worm burden parameters was positive but generally low (r < 0.33), which provided less information about infection intensities. Nonetheless, these results indicate that a reliable and accurate qualitative diagnosis of the two most prevalent intestinal nematodes in chickens can be achieved using a non-invasive copro-antigen ELISA assay.

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.

Reflections and future directions for continued development and refinement of guidelines for anthelmintic efficacy studies

This reflection paper complements the WAAVP (World Association for the Advancement of Veterinary Parasitology) general anthelmintic efficacy guideline, which outlines the general principles of anthelmintic efficacy evaluation across all animal host species. It provides background to the recommendations made in the WAAVP general anthelmintic efficacy guideline, with insights into the discussions leading to specific recommendations in the general guideline or the absence thereof. Furthermore, this paper discusses recent technological advancements with potential value to the evaluation of anthelmintic efficacy that may be considered for future versions of the general or species-specific guidelines if supported by sufficient levels of evidence. Finally, it also identifies potential research questions, such as the statistical approach for comparing worm counts between groups of animals.

Worm control practices on free-range egg farms in Australia and anthelmintic efficacy against nematodes in naturally infected layer chickens

This study investigated worm control practices by free-range egg farmers and the efficacy of the commercial anthelmintics levamisole (LEV), piperazine (PIP), flubendazole (FLBZ) and fenbendazole (FBZ) against gastrointestinal nematodes on two free-range layer farms in Australia. An online survey comprising 36 questions was designed and implemented using SurveyMonkey. The survey contained questions about participant demographics, farm and flock characteristics, perceived intestinal worm importance, infection monitoring, deworming and other worm control practices. A link for the survey was emailed to free range egg producers from their industry body in December 2019. The anthelmintic efficacy trial was conducted in a total of 229 layers naturally infected with Ascaridia galli, Hetarakis gallinarum, Capillaria spp. and/or tape worms. Chickens received a single oral dose of LEV (28 mg/kg), PIP (100 mg/kg), FBZ (10 mg/kg) or LEV-PIP co-administered at their full individual doses, and FLBZ (Flubenol®), 30 ppm or 60 ppm) in the feed over 7 days. Anthelmintic efficacies were estimated by both worm count reduction (WCR %) and excreta egg count reduction (EECR %) tests 10 days after start of treatment. The survey with a response rate of 16/203, revealed that worm infection was of moderate concern to the producers and the majority (68%) felt that the current anthelmintics work effectively. The level of understanding of worms, monitoring and control practices did not reveal any major deficiencies of concern. The most commonly used anthelmintic was LEV (73%) followed by PIP (45%). Based on a standard cut-off value (≥90%), LEV, LEV-PIP, and FBZ attained the desired efficacy but PIP exhibited reduced efficacy against immature A. galli (61-85%), all stages of H. gallinarum (42-77%) and Capillaria spp. (25-44%). FLBZ was highly effective against all stages of roundworms and tapeworm infections. Even though there was some association between the efficacies estimated by WCR % and EECR % the latter was poorly associated in the natural infection model and hence does not provide a reasonable alternative for assessing anthelmintic efficacy when immature stages of the lifecycle are included. These results show no evidence of loss of susceptibility to the tested anthelmintics on these farms supporting the perception of producers that participated in the survey that current treatments work effectively. The reduced efficacy of PIP against some species and immature stages is related to its spectrum of activity rather than providing evidence of emerging resistance.

Evaluation of in vitro methods of anthelmintic efficacy testing against Ascaridia galli

To investigate methods for in vitro assessment of anthelmintic efficacy against the chicken nematode Ascaridia galli this study firstly evaluated sample preparation methods including recovery of eggs from excreta using different flotation fluids and induced larval hatching by the deshelling-centrifugation method and the glass-bead method with or without bile. It then evaluated two in vitro assays, the in-ovo larval development assay (LDA) and larval migration inhibition assay (LMIA), for anthelmintic efficacy testing against A. galli using fresh eggs and artificially hatched larvae, respectively. Four anthelmintics, thiabendazole (TBZ), fenbendazole (FBZ), levamisole (LEV) and piperazine (PIP) were employed using an A. galli isolate of known susceptibility. The results suggested that the LDA and LMIA could successfully be used to generate concentration response curves for the tested drugs. The LDA provided EC50 values for inhibition of egg embryonation of 0.084 and 0.071 μg/ml for TBZ and FBZ, respectively. In the LMIA, the values of effective concentration (EC50) of TBZ, FBZ, LEV and PIP were 105.9, 6.32, 349.9 and 6.78 × 107 nM, respectively. For such in vitro studies, a saturated sugar solution showed high egg recovery efficiency (67.8%) and yielded eggs of the highest morphological quality (98.1%) and subsequent developmental ability (93.3%). The larval hatching assays evaluated did not differ in hatching efficiency but the deshelling-centrifugation method yielded larvae that had slightly better survival rates. For final standardization of these tests and establishment of EC50 reference values, tests using isolates of A. galli of defined resistance status need to be performed.

Anthelmintic efficacy evaluation against different developmental stages of Ascaridia galli following individual or group administration in artificially trickle-infected chickens

The efficacy of commercially available anthelmintics against mature and immature stages (including ovicidal effects) of two Australian field isolates of Ascaridia galli was evaluated in two separate experiments. The anthelmintics tested were levamisole (LEV), piperazine (PIP) and flubendazole (FBZ) plus LEV-PIP. A total of 192 artificially trickle-infected young cockerels (96 birds per isolate) were randomized into sixteen experimental groups of 12 cockerels each (7 treatments and 1 untreated control per isolate). Chickens received label-recommended doses of LEV (28 mg/kg), PIP (100 mg/kg) or LEV-PIP co-administered at their full individual doses as a single oral dose or in group drinking water at recommended concentrations of 0.8 mg/ml or 2.5 mg/ml over eight hours for 1 and 2 days respectively and FLBZ (30 ppm) in the feed over 7 days. Anthelmintic efficacies were assessed by worm count reduction (WCR%) and excreta egg count reduction (EECR%) estimated by two methods. Ten days post treatment, all untreated control birds harboured mixed worm population of 10.1 and 12.3/bird for each isolate respectively which was significantly higher (P < 0.0001) than counts in all treatment groups. Luminal or histotrophic larvae comprised 50-57 % of the total worm count. For LEV, PIP and LEV-PIP, individual oral administration provided a somewhat higher efficacy than group medication in drinking water. EECR% values were inconsistent with WCR% and found to be only an indicator of efficacy against adult worms. All developmental stages of the two A. galli isolates were highly susceptible to FLBZ (100 %) followed by LEV-PIP (92.4-100 %) and LEV (87.7-100 %). PIP exhibited good efficacy against adult worms (92-97 %) but reduced efficacy against luminal (79-84 %) and histotrophic (61-72 %) larvae. Embryonation capacity of eggs recovered from worms expelled after treatment with LEV (47-54 %), PIP (44-54 %) or LEV-PIP (45-48 %) did not differ from those from untreated birds (50-51 %) whereas eggs from FLBZ treated worms had a significantly lower (P < 0.05) capacity to embryonate (≤ 2 %). Put together, our results demonstrate no evidence of resistance of the test A. galli isolates to the tested anthelmintics but a significant advantage of FLBZ, followed by LEV-PIP and LEV over PIP in the control of A. galli, specifically with regard to immature stages. A. galli worms expelled after treatment with LEV, PIP or their combination, but not FLBZ contain viable eggs. This has epidemiological implications and may also provide an option for isolating eggs from mature worms for A. galli propagation experiments without having to sacrifice birds.

Ascaridia galli challenge model for worm propagation in young chickens with or without immunosuppression

With the continued growth of free-range egg production, the importance of the chicken roundworm Ascaridia galli is increasing. Investigations into this parasite would be facilitated by the availability of characterised strains and clear guidelines on optimal methods of multiplication and maintenance. Currently, there is lack of well-defined in vivo models for maintaining A. galli and the potential of using host immunosuppression to boost parasite development and worm egg output has not been investigated. To determine the most efficient way of propagating A. galli in young chickens an experiment with a 2 × 3 × 4 × 2 factorial design involving age of chicken at infection (day-old or 14 days old), immunosuppression (dexamethasone (DEX), cyclophosphamide (CY) or sham), infective egg dose (0, 100, 300 or 900 embryonated eggs/bird) and time of worm recovery after infection (8 or 10 weeks post-infection) was conducted. The experiment used a total of 384 layer cockerel chicks. Infection was delivered orally in 3 split doses over one week and immunosuppressants were administered by intramuscular injection concurrently with the infections. Body weight, excreta egg counts, intestinal worm count and worm establishment rate were assessed. The only sign of ascaridiosis noted was mild diarrhoea at the time of slaughter in some birds with a significant- positive association with worm count. Infection caused a significant dose dependent reduction in body weight in non-immunosuppressed birds but this effect was ameliorated by immunosuppression. Age at infection had no significant effect on the studied variables although both worm and egg counts were numerically higher in the day-old infected groups. Egg dose significantly influenced the prevalence of infection, worm establishment rate, worm egg production and mean worm count. The 300 and 900 egg doses resulted in significantly higher worm count and egg production than the 100 egg dose. A significant negative correlation was observed between egg dose and worm establishment rate indicating an inverse relationship. Immunosuppression with DEX, but not CY resulted in significantly higher mean worm burden than in control chickens with excreta egg counts also considerably higher in DEX treated birds. Our results suggest that trickle infection at day-old with infective doses of 300 eggs coupled with immunosuppression with DEX would provide the most efficient way to propagate A. galli worms in vivo, as using older birds or a higher egg dose did not provide any advantage.

Comparative therapeutic efficacies of oral and in-water administered levamisole, piperazine and fenbendazole against experimental Ascaridia galli infection in chickens

Evidence on the current efficacy status of anthelmintics used in the Australian poultry sector is lacking. A controlled trial was conducted to evaluate the efficacy of three commonly used anthelmintics, namely levamisole (LEV), piperazine (PIP) and fenbendazole (FBZ) plus levamisole-piperazine combination (LEV-PIP) against a field strain of A. galli recovered following flock treatment with LEV. A total of 108 A. galli infected cockerels were randomized into nine experimental groups of 12 cockerels each (eight treatments and one untreated control) with each treatment administered by two routes (oral drench or in drinking water). Chickens received label-recommended doses of LEV (28 mg/kg) and PIP (100 mg/kg) while LEV-PIP involved both compounds co-administered at their full individual dose rates. FBZ was tested at two dose rates; 10 mg/kg as a single oral drench or 5 mg/kg in drinking water over 5 days. Anthelmintic efficacies were assessed by worm count reduction (WCR%) and excreta egg count reduction (EECR%) estimated by two methods. Ten days post treatment, the untreated control birds harboured significantly higher worm counts (P < 0.0001) than those in all treatment groups irrespective of the mode drug of application. Oral drenching caused a greater reduction in worm and egg counts (P < 0.05) than medication in drinking water. Based on geometric worm counts the percentage efficacies for the oral drench were 99.1, 96.3, 97.2 and 100 % respectively for LEV, PIP, FBZ and LEV-PIP, and for administration in water 96.4, 93.7, 88.7 and 97.7 % respectively. Efficacies based on EECR% were consistent with WCR% with strong positive linear association between efficacy values. In conclusion, our results demonstrate no evidence of loss of susceptiblity of the test A. galli isolate to both LEV and PIP contrary to our hypothesis. Additional efficacy studies are needed using A. galli isolates sourced from different poultry flocks across Australia.

Excretion of Histomonas meleagridis following experimental co-infection of distinct chicken lines with Heterakis gallinarum and Ascaridia galli

Background

Histomonosis is a severe re-emerging disease of poultry caused by Histomonas meleagridis, a protozoan parasite which survives in the environment via the cecal worm Heterakis gallinarum. Following infection, the parasites reside in the ceca and are excreted via host feces. In the present work, male birds of conventional broiler (Ross 308, R), layer (Lohmann Brown Plus, LB) and a dual-purpose (Lohmann Dual, LD) chicken line were infected with 250 embryonated eggs of Ascaridia galli and Heterakis gallinarum, respectively, with the latter nematode harboring Histomonas meleagridis, to investigate a co-infection of nematodes with the protozoan parasite in different host lines.

Methods

In weekly intervals, from 2 to 9 weeks post infection (wpi), individual fecal samples (n = 234) from the chickens were collected to quantify the excretion of H. meleagridis by real-time PCR and to determine the number of nematode eggs per gram (EPG) in order to elucidate excretion dynamics of the flagellate and the nematodes. This was further investigated by indirect detection using plasma samples of the birds to detect antibodies specific for H. meleagridis and worms by ELISA. The infection with H. meleagridis was confirmed by histopathology and immunohistochemistry to detect the flagellate in the cecum of representing birds.

Results

The excretion of H. meleagridis could already be observed from the 2nd wpi in some birds and increased to 100% in the last week of the experiment in all groups independent of the genetic line. This increase could be confirmed by ELISA, even though the number of excreted H. meleagridis per bird was generally low. Overall, histomonads were detected in 60% to 78% of birds with temporary differences between the different genetic lines, which also showed variations in the EPG and worm burden of both nematodes.

Conclusions

The infection with H. gallinarum eggs contaminated with H. meleagridis led to a permanent excretion of the flagellate in host feces. Differences in the excretion of H. meleagridis in the feces of genetically different host lines occurred intermittently. The excretion of the protozoan or its vector H. gallinarum was mostly exclusive, showing a negative interaction between the two parasites in the same host.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04823-1.

Impact of Nematode Infections on Non-specific and Vaccine-Induced Humoral Immunity in Dual-Purpose or Layer-Type Chicken Genotypes

Nematode infections may induce immune-modulatory effects and influence host-immune responses to other pathogens. The aim of the study was to investigate whether a mixed nematode-infection influences non-specific and vaccine-induced humoral immunity against Newcastle Disease Virus (NDV), Infectious Bronchitis Virus (IBV), and Avian Metapneumovirus (AMPV) in already vaccinated hens of a dual-purpose (Lohmann Dual, LD) or a layer genotype (Lohmann Brown Plus; LB). Until 17 weeks-of-age, LD (n = 70) and LB (n = 109) hens were vaccinated against major bacterial and viral diseases and coccidiosis. At 24 weeks-of-age, the hens received either a placebo or an oral inoculation of 1,000 infectious eggs of A. galli and H. gallinarum. Plasma total immunoglobulin (Ig) isotypes (IgY, IgM, IgA) levels and vaccine-induced antibody titers against NDV, IBV, and AMPV were determined from 2 to 18 weeks post-infection (wpi). Infections had no suppressing effect on total Ig isotypes IgY, IgM, and IgA as well as on vaccine-induced antibody titers against NDV, IBV, and AMPV (P > 0.05). Overall, LB hens had higher levels of IgY, IgM, and IgA than those of LD hens (P < 0.05). There were no differences between IBV titers of the two genotypes (P > 0.05). Independent of infection status of the hens, NDV titers were higher in LB hens than in LD hens at wpi 2 (P < 0.05), but not in following weeks (P > 0.05). Uninfected LD hens had lower AMPV titers than their infected counterparts at 6 and 14 wpi (P < 0.05). Regardless of nematode infection, LD hens revealed a higher risk of responding weak to vaccination against NDV (odds ratio = 5.45; P = 0.021) and AMPV (odds ratio = 13.99, P < 0.001) than did LB hens (P > 0.05). We conclude that nematode infections have no adverse effects on non-specific and vaccine-induced humoral immunity in either genotype. LB hens have higher levels of total immunoglobulin isotypes than LD hens. Except for IBV, vaccine-induced humoral immune responses show a dependency on genotype. Dual-purpose hens show lower responsiveness to vaccinations against NDV and AMPV, possibly due to factors associated with increased body fat reserves in this genotype.

Differentially Expressed Gene Patterns in Ascarid-Infected Chickens of Higher- or Lower-Performing Genotypes

Simple Summary

Nematode infections may increase mortality and welfare problems in laying hens. The two ascarid worms, Ascaridia galli and Heterakis gallinarum, are highly prevalent in laying hens kept in non-cage housing systems worldwide. The ability of a host to expel pathogens is a component of resistance to diseases. The molecular basis of differences between different host animals in their efficiency to expel worms is, however, not well understood. Therefore, we performed a detailed analysis of differentially expressed genes (DEGs) in two chicken genotypes (Lohmann Brown Plus (LB), Lohmann Dual (LD)), each with a lower or higher infection intensity level of A. galli and H. gallinarum. Our data showed significant upregulation of Guanylate Binding Protein 7 (GBP7) in LD hens. Gene ontology analysis revealed higher transcriptome activity related to “response to external stimulus” in LB hens, implying a higher stress response in this genotype. In contrast, LD hens showed higher transcriptomic expression of genes associated with a higher tolerance to infections.

Abstract

Here, we describe the first transcriptomic investigation of the peripheral blood of chickens exposed to Ascaridia galli and Heterakis gallinarum infections. We investigated differentially expressed gene (DEG) patterns in two chicken genotypes with either a higher (Lohmann Brown Plus, LB) or lower (Lohmann Dual, LD) laying performance level. The hens were experimentally coinfected with A. galli and H. gallinarum, and their worm burdens and infection parameters were determined six weeks post infection. Based on most representative infection parameters, the hens were clustered into lower- and higher-infection intensity classes. We identified a total of 78 DEGs contributing to infection-related phenotypic variation in the two genotypes. Our data showed significant upregulation of Guanylate Binding Protein 7 (GBP7) in LD hens, making it a promising candidate for tolerance to ascarid infections in chickens. Gene ontology analysis revealed higher transcriptome activity related to biological processes such as “response to external stimulus” in LB hens, implying a higher stress response in this genotype. In contrast, LD hens showed higher transcriptomic expression of genes related to ontology classes that are possibly associated with a higher tolerance to infections. These findings may help explain why lower-performing genotypes (i.e., LD) are less sensitive to infections in terms of maintaining their performance.

Anthelmintic efficacy of fenbendazole and levamisole in native fowl in northern Iran

BACKGROUND

With the increasing number of free-range domestic chickens, helminth parasites have potentially become more of a threat to commercial flocks in recent years, and routine poultry deworming is needed to improve the efficiency of chicken production. The present study deals with a field trial to study the efficacy of two generally used anthelmintics, fenbendazole and levamisole, against gastrointestinal nematodes of domestic chickens in northern Iran.

METHODS

Of 45 domestic chicken flocks involved in the study, 20 flocks were selected to participate in fecal egg count reduction testing based on flock size from April 2017 to September 2018. The infected chickens were randomly divided into three equal groups of 30 each. Ninety chickens in the infected groups received one of the following treatments (d 0 of treatment): Group 1: 5 mg kg^-1 body weight (BW) fenbendazole for 3 consecutive days; Group 2: 16 mg kg^-1 BW levamisole; Group 3 control: placebo, water + DMSO (dimethylsulfoxide). The efficacy of the treatments was evaluated by comparing fecal egg counts in the treated and control groups.

RESULTS

Examination of three flocks of chickens from the control group showed that 95.0% of the animals were infected with gastrointestinal nematodes with an average geometric value of 361 eggs per gram of feces. Fenbendazole at a dose of 5 mg kg^-1 BW for 3 days showed an efficacy of 83.7% (P ≥ 0.05), and levamisole at a dose of 16 mg kg^-1 BW showed 71.8% efficacy (P ≥ 0.05) with geometric mean eggs in a gram of feces of 100 and 199.6, respectively. In general, fenbendazole and levamisole treatment led to significantly lower activity. The result of this study revealed that fenbendazole was a better and more effective dewormer than levamisole on the three Iranian domestic chicken flocks, but the difference was not significant. Capillaria spp. were the most generally resistant nematodes followed by Trichostrongylus spp. and Amidostomum anseris.

CONCLUSION

Our results indicated that fenbendazole and levamisole effectively reduced the number of nemathodes in three Iranian domestic chicken flocks. Given the results of our study, resistance can be expected in the parasitic helminths of poultry. Additional larger scale studies are required to determine the prevalence of anthelmintic resistance in the poultry industry.

Germination capacity of the Pochonia chlamydosporia fungus after its passage through the gastrointestinal tract of domestic chickens (Gallus gallus domesticus)

This study evaluated the germination capacity of Pochonia chlamydosporia (VC4) fungus after its passage through the gastrointestinal tract of domestic chickens and its interaction with Ascaridia galli and Heterakis gallinarum eggs. Twenty-two domestic chickens were divided in two groups: control group (G1) received shredded corn substrate without VC4; and treatment group (G2) received a single dose of 29 g corn substrate containing 3.3 × 10⁶ conidia/chlamydospores (VC4). Subsequently, chicken fecal samples were collected at intervals of 0, 6, 8, 10, 12, 18 and 24 h. Petri dishes from fecal samples of the treated group (G2) were subdivided (G2a and G2b), and then replicated in 2% agar-water medium for the microbiological test. After VC4 growth, approximately 200 eggs of A. galli (G2a) and H. gallinarum (G2b) were added to each subgroup to evaluation of ovicidal activity. There was fungal viability after passage through chicken gastrointestinal tract and egg predation of 59.9% and 43.2% for A. galli and H. gallinarum, respectively. The present work demonstrates the ability of the fungus P. chlamydosporia to survive after passing through the gastrointestinal tract of domestic chickens, an extreme environment (low pH, enzymes, microbiota and mechanical action), and still germinate after being excreted with feces.

Resistance to fenbendazole in Ascaridia dissimilis, an important nematode parasite of turkeys

An important factor in efficient production of poultry is management of parasites. Ascaridia dissimilis is the most prevalent small intestinal nematode parasite of turkeys with up to 100% of flocks infected. High worm burdens can cause necrotic enteritis leading to high mortality in flocks. Recently, we were made aware of multiple cases where high burdens were seen at slaughter despite the administration of anthelmintics at frequent intervals, suggesting that resistance may have evolved in A. dissimilis. To address this issue, we obtained eggs of A. dissimilis from 4 commercial turkey farms and performed controlled efficacy tests to determine if fenbendazole resistance was present. Three farms had histories of frequent use of fenbendazole and worms found at slaughter, suggesting they may have resistance, and one was an organic farm where we had no additional history other than the farm had transitioned to organic production a few years earlier. For each worm isolate there were 2 treated and 2 untreated groups containing 9 birds each, with all groups being replicated in 2 separate rooms. Birds were infected with approximately 200 infective eggs, and treated groups received fenbendazole in the water (SafeGuard Aquasol, 1 mg/kg) for 5 consecutive days starting on day 24 post-infection. One week after the last treatment birds were necropsied, intestinal contents were collected and worms enumerated. Three of the four isolates demonstrated greater than 99% efficacy, indicating they were fully susceptible to fenbendazole. However, the fourth isolate demonstrated a significantly reduced efficacy of 63.89%, indicating the presence of resistance. Interestingly, this was the organic farm, whereas the 3 farms with "suspected" resistance all turned out to be fully susceptible. Given that 1 randomly acquired isolate of A. dissimilis, out of 4 tested, demonstrated resistance in this study, fenbendazole resistance may be a much larger problem on turkey farms than is currently recognized. Additional studies are needed to determine the prevalence of resistance, as well as the economic impact that resistant A. dissimilis have on turkey production.

Resistance and tolerance to mixed nematode infections in relation to performance level in laying hens

Modern chickens have been genetically developed to perform high under optimal conditions. We hypothesized that high-performance is associated with a higher sensitivity to environmental challenges in laying hens. By using nematode infections as an environmental stressor, we assessed performance-level associated host responses in a high (i.e. Lohmann Brown Plus, LB) and in a lower performing, a so-called dual-purpose chicken genotype (i.e. Lohmann Dual, LD). The hens were infected with 1000 eggs of Ascaridia galli and Heterakis gallinarum at 24 weeks of age. Hen performance parameters, humoral immune responses in plasma and egg yolks and worm burdens were assessed at several occasions over a period of 18 weeks post infection (wpi). While infections had no significant effect on feed intake (P = 0.130) and body weight in both genotypes (P = 0.392), feed conversion efficiency was negatively affected by infections (P = 0.017). Infections reduced both laying rate and egg weight and thereby per capita egg mass in both genotypes (P < 0.05). While laying rate in infected LB hens decreased significantly (P < 0.05) in the early infection period (i.e. by 3 wpi), the decrease in LD hens appeared much later (i.e. by 14 wpi). Worm burdens resulting from the experimental infection were not different between the genotypes for both worm species (P > 0.05), whereas LB hens were more susceptible (P < 0.05) to re-infections than LD hens. Changes in humoral immune responses (i.e. ascarid-specific IgY antibodies in plasma and egg yolks) of the two genotypes over time reflected closely the corresponding changes in larval counts of the hens, descending from both experimental and subsequent natural infections in both genotypes. Infections caused a shift in egg size classes, leading to smaller frequency of larger eggs in both genotypes. Infections reduced egg weight (P = 0.018) and led to a reduced fat content in the egg yolks (P = 0.045). The proportion of poly-unsaturated fatty acids (PUFA), especially n-6-PUFA, was also lower in egg yolks of the infected hens (P = 0.032). We conclude that tolerance to nematode infections in laying hens is dependent on host-performance level. The impairment in host tolerance was both genotype and time dependent, likely due to differences in genetic programming for production peak and persistency of the two genotypes. The two genotypes exhibited similar levels of resistance after a fully controlled experimental infection, but the high performing hens were more susceptible to subsequent natural infections. Infections negatively affected economically important egg-quality traits, including egg weight, fat content and fatty acid profiles in egg yolks.

Resistance and tolerance to mixed nematode infections in chicken genotypes with extremely different growth rates

Fast growing broilers are less able to cope with fitness related challenges. As the allocation of metabolic resources may be traded off between performance and defence functions in parasitized hosts, we hypothesized that fast growing broilers are more sensitive to mixed nematode infections compared with slower growing genotypes under the same environmental conditions. Therefore, we compared male birds of genotypes selected for either meat production (Ross-308, R) or egg production (Lohmann Brown Plus, LB) or for both purposes (Lohmann Dual, LD), to assess their resistance and tolerance to mixed nematode infections with Ascaridia galli and Heterakis gallinarum. While infections reduced feed intake in all three genotypes, feed conversion efficiency was not affected. Infections impaired growth performance only in R birds, indicating lower tolerance in the fast growing genotype compared with slower growing LB and LD genotypes. Impaired tolerance in R birds was associated with a relative nutrient scarcity due to an infection-induced lower feed intake. Resistance to experimentally induced infections depended on host genotype as well as on the worm species involved. Overall, the A. galli burden was higher in R than LB, whereas the burden of LD was not different from that of R and LB. In contrast, the H. gallinarum burden of first generation worms was similar in the three genotypes. Susceptibility to re-infection with H. gallinarum was higher in LB than in LD, whereas very low levels of re-infection were observed in R birds. Our data collectively suggest that resistance and tolerance to mixed nematode infections are sensitive to growth rate in chickens. These differences amongst genotypes may partly be associated with a mismatch between the actual nutrient supply and genotype-specific nutrient requirements.

Co-expulsion of Ascaridia galli and Heterakis gallinarum by chickens

Worm expulsion is known to occur in mammalian hosts exposed to mono-species helminth infections, whilst this phenomenon is poorly described in avian hosts. Mono-species infections, however, are rather rare under natural circumstances. Therefore, we quantified the extent and duration of worm expulsion by chickens experimentally infected with both Ascaridia galli and Heterakis gallinarum, and investigated the accompanying humoral and cell-mediated host immune responses in association with population dynamics of the worms. Results demonstrated the strong co-expulsion of the two ascarid species in three phases. The expulsion patterns were characterized by non-linear alterations separated by species-specific time thresholds. Ascaridia galli burden decreased at a daily expulsion rate (e) of 4.3 worms up to a threshold of 30.5 days p.i., followed by a much lower second expulsion rate (e = 0.46), which resulted in almost, but not entirely, complete expulsion. Heterakis gallinarum was able to induce reinfection within the experimental period (9 weeks). First generation H. gallinarum worms were expelled at a daily rate of e = 0.8 worms until 36.4 days p.i., and thereafter almost no expulsion occurred. Data on both humoral and tissue-specific cellular immune responses collectively indicated that antibody production in chickens with multispecies ascarid infections is triggered by Th2 polarisation. Local Th2 immune responses and mucin-regulating genes are associated with the regulation of worm expulsion. In conclusion, the chicken host is able to eliminate the vast majority of both A. galli and H. gallinarum in three distinct phases. Worm expulsion was strongly associated with the developmental stages of the worms, where the elimination of juvenile stages was specifically targeted. A very small percentage of worms was nevertheless able to survive, reach maturity and induce reinfection if given sufficient time to complete their life cycle. Both humoral and local immune responses were associated with worm expulsion.

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.

Time- and dose-dependent development of humoral immune responses to Ascaridia galli in experimentally and naturally infected chickens

Factors affecting the development of Ascaridia galli-specific humoral responses and their protective roles are largely unknown. We investigated the effects of time and infection dose on A. galli-specific IgY antibody levels following experimental infection. The acquisition and development of new infections and reinfections were also monitored by using tracer birds. Relationships between the retrospective IgY and the final worm burden of the birds were investigated to determine whether humoral immune responses generated during infection provide protection to the host animal. Young chickens were infected (+) with either 100 or 1000 embryonated eggs of A. galli (100+: n = 45; 1000+: n = 45) or kept as uninfected controls (CON: n = 10). Uninfected birds were also added to each infection group as tracer (T) birds (T100+; n = 5 and T1000+; n = 5). Faecal egg counts and IgY antibody concentrations in plasma and egg yolk were determined at selected intervals. Final worm burdens were quantified at 28 weeks post infection (wpi). The plasma antibody (PAB) and egg yolk antibody (EAB) levels of experimentally infected birds were compared to those of control and tracer birds throughout the study period, and PAB levels were found to depend initially on the infection dose but thereafter mainly on reinfections. Starting at wpi 2, 1000+ had consistently higher PAB levels than CON did (P < 0.05). With exceptions at wpi 0, 2 and 12, PAB levels were also higher (P < 0.05) or tended to be higher (P < 0.10) in 100+ than in CON. An earlier and higher increase was observed in the PAB levels of T1000+ than in those of T100+, implying that (re-)infection occurrence depended on the infection dose. Although 1000+ showed higher (P < 0.05) EAB levels than CON did at both wpi 14 and 18, EAB levels were higher in 100+ than in CON only at wpi 28 (P < 0.05). The total worm burdens in the initial experimentally infected birds were similar (P = 0.257); they were also highly comparable between experimentally and naturally infected birds, indicating that final worm burden was mainly determined by the naturally occurring infections resulting from continuous exposure. When all available information on the retrospective plasma and egg yolk IgY levels was collectively evaluated to estimate the larval or total worm burdens of the experimentally infected birds, both PAB and EAB levels at particular wpi were significantly associated with worm burden, especially with larval count. In conclusion, our data support the hypothesis that the number of larvae, rather than the number of mature worms, affects the antibody levels in both plasma and egg yolk. Despite the increased levels of A. galli-specific antibodies in plasma and egg yolk throughout the study period, only a weak indication was found that antibodies might be directly associated with protection.

Helminth infections in chickens (Gallus domesticus) raised in different production systems in Brazil

The current study evaluated helminth infections in birds raised in different production systems for different purposes (extensive/dual-purpose, semi-intensive/broiler, semi-intensive/hen, intensive/hen and intensive/broiler) in Brazil. A total of 374 birds was assessed for helminths at necropsy using standard parasitological methods. During the necropsies, organs from the gastrointestinal tract (crop, esophagus, proventriculus, gizzard, small intestine, large intestine and ceca) of each bird were collected and the contents fixed in 70% ethanol. Additionally, the trachea and eyes were assessed for the presence of helminths. The small intestine was examined using a methodology that allowed the recovery of cestode scolices attached to the intestinal mucosa. Stereomicroscopy and optical microscopy were used to detect and identify helminth species based on their morphological characteristics. Fifteen helminth species were found among birds from the different systems. The extensive system presented the highest number of helminth species (six cestodes, seven nematodes and one trematode) and the highest number of parasites (mean helminths/bird), followed by the semi-intensive system (broiler: six cestode and four nematode species; hens: five cestode and three nematode species). Hens from the intensive system were parasitized by five cestode, four nematode and one trematode species. No parasites were detected in broilers raised in the intensive systems. The results obtained in this study highlight the need for special attention and the implementation of biosecurity measures for the prevention of helminth infections in intensive systems (hens) and particularly in extensive and semi-intensive alternative poultry production systems.

Prevalence of gastrointestinal helminth infections in free-range laying hens under mountain farming production conditions

1. A cross-sectional study was conducted from September 2015 to July 2016 in South Tyrol, Northern Italy to examine the prevalence of gastrointestinal helminths in free-range laying hens under mountain farming production conditions. 2. A total of 280 laying hens from 14 free-range mountain farms (4 organic, 10 conventional) were randomly collected at the end of the laying period. Faecal samples were taken to analyse faecal egg counts (FEC) and faecal oocyst counts (FOC). The gastrointestinal tracts were removed post mortem and examined for the presence of helminths. 3. In faeces, FEC values averaged 258 eggs per g of faeces, which were dominated by Ascaridia galli and Heterakis gallinarum. Mean FOC was 80 oocysts/g. In the gastrointestinal tract, at least one nematode species was found in 99.3% of the examined hens. H. gallinarum was the most prevalent nematode (95.7%), followed by Capillaria spp. (66.8%) and A. galli (63.6%). Thirty per cent of the chickens were infected with cestodes (tapeworms). Correlation coefficients between worm counts of H. gallinarum, Capillaria spp. and A. galli ranged from 0.41 to 0.51. 5. The helminth prevalence did not differ between conventional and organic farms, whereas total worm burden was higher in organic compared with conventional farms (318.9 vs. 112.0). Prevalence and infection intensity did not differ between farms that used anthelmintic treatments and those that did not. 6. In conclusion, free-range laying hens under the studied mountain farming conditions are at high risk of nematode infection, especially in organic systems. The vast majority of hens are subclinical infected with at least one helminth species.

Immune responses following experimental infection with Ascaridia galli and necrotic enteritis in broiler chickens

Broilers commonly suffer from necrotic enteritis (NE). Other gastrointestinal infectious diseases affect poultry, including nematode infections which are considered a re-emerging disease in barn and free-range systems. The aim of this study was to characterize the immune response of broilers after artificial infection with NE and contrast these with responses to the nematode Ascaridia galli and determine whether immune parameters measured during the course of infection can be used to distinguish infected from uninfected birds. A total of 96 one-day-old male Ross 308 broiler chickens were used in this study. At 10 days of age, broilers were randomly assigned to one of the following treatment groups: control birds (n = 32), A. galli infected birds (n = 32), or NE infected birds (n = 32) and inoculated with the appropriate infective agents. The immune response of birds was monitored through evaluation of haematology parameters, acute phase protein production, and intraepithelial intestinal lymphocyte population changes at 11, 16, 20, and 32 days of age. T-helper cells (CD4⁺CD8^-) increased significantly over time, and were significantly higher in A. galli and NE compared to day 10 controls. In conclusion, α-1 glycoprotein levels can distinguish birds with NE from other birds, including those infected with A. galli; also T-helper cell numbers can distinguish both NE and A. galli from uninfected birds and thirdly, 10 days post infection is the best time point to evaluate the bird's immune response for A. galli infections.

Evaluation of benzimidazole resistance status in Ascaridia galli

Susceptability of Ascaridia galli to benzimidazole (BZ) was investigated using faecal egg count reduction test (FECRT), in ovo larval development test (LDT) and genetic markers (mutations at codons 167, 198 and 200 of β-tubulin gene). Six flocks (F1−F6) of a commercial laying hen farm with different number of exposure to BZ were recruited. The FECR was calculated by analyzing individual faeces (F1, F2, F4 and F5) before and 10 days after treatment. The LDT was performed on parasite eggs from pooled samples from F1 to F6 and LC50 and LC99 were calculated. DNA was extracted from 120 worms and sequenced for β-tubulin gene. In all flocks, the FECRs were above 95% (lower CI above 90%). No significant difference was observed (p > 0·05) among obtained LC50 (F1/F4 and F2/F5 vs F3/F6) in the LDT. However, LC50 and LC99 were higher than suggested values for declaration of resistance in other nematode species. No variation was observed in codon positions involved in BZ resistance. Overall, our results indicated lack of evidence of resistance to BZ in A. galli. More research is needed to confirm these results and to further optimize the existing tools for detection and monitoring of anthelmintic resistance in A. galli.

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.

A description of village chicken production systems and prevalence of gastrointestinal parasites: Case studies in Limpopo and KwaZulu-Natal provinces of South Africa

The majority of rural households in developing countries own village chickens that are reared under traditional scavenging systems with few inputs and exposure to various parasitic infestations. Understanding of the village chicken farming system and its influence on helminth infestation is a prerequisite for optimal prevention and control strategies. This study investigated the village chicken production system and associated gastrointestinal parasites in 87 households from Limpopo (n = 39) and KwaZulu-Natal (n = 48) provinces of South Africa. A total of 191 village chicken faecal samples and 145 intestines were collected to determine the prevalence of gastrointestinal parasites in villages of Limpopo and KwaZulu-Natal provinces, respectively. The faecal floatation analysis of samples from Limpopo and KwaZulu-Natal provinces indicated infestations by Ascaridia galli (18.77%), Heterakis gallinarum (15.56%) and Capillaria spp. (4.00%); tapeworms Choanotaenia infundibulum (2.10%) and Raillietina cesticillus (6.00%) and Eimeria spp. (29.46%). Mixed infestations were observed in five (4.90%) samples from Limpopo province and in only four (4.49%) from KwaZulu-Natal province, of which 1.12% were a mixture of C. infundibulum and Eimeria spp. and 3.37% a combination of H. gallinarum and Eimeria spp. In Limpopo, 2.94% of the chickens were positive for H. gallinarum and Eimeria spp., whilst 0.98% had A. galli and Capillaria spp. infestations. Further investigation is needed to understand the impact of gastrointestinal parasites on village chicken health and production and develop appropriate intervention and control strategies feasible for smallholder farmers.

Mello and Campos (1974) method adapted for the recovery of cestodes in birds ( Gallus domesticus )

ABSTRACT: The specific diagnosis and evaluation of the intensity of avian helminth infections are essential for efficacy studies and the determination of drug doses targeted to their control. This study evaluated the Mello and Campos method, originally described for parasitological diagnosis in dogs, in the recovery of scolices from cestode parasites of poultry (Gallus domesticus ). A total of 52 naturally infected birds obtained from farms underwent parasitological necropsy using the Mello and Campos method. The method consisted of four steps: content, soaking, scraping and evaluation. The number of scolices recovered per bird ranged from 1 to 4,345, and the highest number of scolices was recovered from material derived from the soaking step. The cestodes species diagnosed were Amoebotaenia cuneata , Choanotaenia infundibulum , Hymenolepis sp., Raillietina tetragona , Raillietina echinobothrida and Raillietina cesticillus . The Mello and Campos method, originally used to test for helminths in dogs, was effective in avian cestode testing because it includes a soaking step, which enables a more efficient recovery of scolices.

Population genetic structure of Ascaridia galli of extensively raised chickens of South Africa

Ascaridia galli is one of the most common nematode affecting chickens. This study characterized A. galli parasites collected from South African village chickens of Limpopo (n=18) and KwaZulu-Natal (n=22) provinces using the 510bp sequences of cytochrome C oxidase subunit 1 gene of the mitochondrial DNA. Fourteen and 12 polymorphic sites were observed for Limpopo and KwaZulu-Natal sequences, respectively. Six haplotypes were observed in total. Haplotype diversity was high and ranged from 0.749 for Limpopo province to 0.758 for KwaZulu-Natal province isolates. There was no genetic differentiation between A. galli from Limpopo and KwaZulu-Natal provinces. The six South African haplotypes were unique compared to those published in the GeneBank sampled from Hy-line chickens raised under organic farming in Denmark. The utility of cytochrome C oxidase subunit 1 gene as a potential genetic marker for studying A. galli in village chicken populations is presented.

Efficacy of anthelmintic treatment in captive-reared black stilts (Himantopus novaezelandiae) released to the wild

AIMS

To assess the efficacy of praziquantel (PZQ) administered to control helminths in captive-reared critically endangered black stilts (Himantopus novaezelandiae) before their release into the wild and determine the effect on their survival shortly after release.

METHODS

Of 77 captive black stilts, 37 were treated with PZQ prior to release into the wild in South Canterbury, New Zealand, in August and September 2007. Faecal helminth egg counts (FEC) were measured before and after anthelmintic treatment, and before and after release to the wild using modified faecal flotation and sedimentation methods. In addition, total helminth counts were determined in 11 of the birds that died following release, as well as four captive and 11 other wild stilts.

RESULTS

The efficacy of PZQ against trematodes was 92% and against Capillaria spp. was 34%. No trematode or Capillaria spp. eggs were detected in treated birds 1 day after treatment, but FEC increased 3-5 days after treatment. There were no differences in the total helminth counts for trematodes, cestodes or Capillaria spp. in control or treated birds (p>0.2). Survival did not differ between treatment groups in the August or September releases (p>0.4). Of control and treated birds, 11/17 (65%) and 8/14 (57%) survived to 31 days, respectively, in the August release, and 16/20 (80%) and 10/15 (67%) survived to 84 days, respectively, in the September release.

CONCLUSION

Overall, the results suggest that PZQ treatment may be an unnecessary cost and the risks of producing anthelmintic resistance, injuring the birds during processing or producing an unnecessary stress response at the time of release could exceed any likely benefits.

CLINICAL RELEVANCE

It is recommended that pre-release anthelmintic treatment of black stilts should be used only if indicated by health screening. Any treatment should incorporate annual efficacy testing to monitor the emergence of anthelmintic resistance.

Spatial distribution of infectious stages of the nematode Syngamus trachea within pheasant (Phasianus colchicus) release pens on estates in the South West of England: Potential density dependence?

The spatial distribution of the infectious stages of parasites with a direct life cycle is one of the most important factors influencing infectious disease dynamics, and acquisition rates will generally increase as the contact time between parasite and host increases. For animal species that are constrained by feeding opportunities, one might expect disease patterns to be highly skewed within confined systems. The aim of the present study was to identify to what extent, if any, eggs of avian parasites are aggregated within the release pen, and to evaluate what effect, if any, this aggregation had on the distribution of the adult stages within the host species. The abundance of Syngamus trachea eggs were highly aggregated within pens, with high levels of contamination driven by a combination of feeder placement, soil moisture and host-mediated heterogeneities in immuno-competence. The log mean and log variance of egg abundance was highly linear (R(2)=0.97-0.99), with an estimated slope (b) of between 1.79 and 1.97 for individual sites, and 2.11 when sites were combined, which indicated aggregation relative to an estimated Poisson slope of unity. Although the placement of feeders and environmental moisture could be contributing to parasite aggregation, density-dependent processes appear to be ensuring the population does not become too over or under-dispersed, in order to maintain the transmission-virulence equilibrium. To the best of our knowledge, this is the first paper to explicitly demonstrate the high spatial aggregation of eggs around feeding sites and the first to suggest possible density-dependent regulatory mechanisms stabilising disease dynamics between S. trachea and ring necked Pheasants (Phasianus colchicus).

Spatio-temporal factors influencing the occurrence of Syngamus trachea within release pens in the South West of England

Syngamus trachea is a pathogenic tracheal nematode that causes syngamiasis in wild and game birds, especially when birds are managed at high densities. Despite its pathogenic nature, very little is known about its epidemiology and relationship with ambient temperature and humidity. The spatial and temporal modelling of disease was undertaken on two pheasant estates within the South West of England from April 2014 to August 2014. Significant differences between the mean numbers of eggs per gram of soil were identified between pens at both site 1 and site 2 but did not differ significantly between sites. Egg abundance was significantly associated with soil moisture content, with greater egg survival between years in pens with higher average volumetric soil moisture content. Previous years stocking density and pen age were also associated with greater egg survival between years with more eggs being recovered in pens with greater stocking densities, and pens that had been sited longer. The greatest model to explain the variation in the numbers of eggs per gram of soil per pen was a combination of soil moisture content, stocking density and pen age. Larval recovery differed significantly between sites. Larval abundance was significantly and positively associated with temperature and relative humidity at site 1. Similarly, temperature and humidity were also positively and significantly associated with larval abundance at site 2. Rainfall did not influence larval recovery at either site 1 or site 2. The model with the greatest ability to explain larval abundance at both sites, was a combination of temperature, humidity and rainfall. Infection status (positive faecal egg counts) was significantly and positively associated with larval abundance at both sites, but rainfall was only positively associated at site 1. Temperature and humidity were positively associated with infection status at site 2, but not at site 1. The present study highlights the influence of climatic variables on both egg survival and larval abundance, and could therefore be used to develop more targeted treatment strategies around periods of higher disease risk. The frequent use of release pens is a clear factor in the epidemiology of syngamiasis, and it is recommended that pens be rested and/or rotated in order to reduce infection pressure in subsequent flocks.

In vitro and in vivo screening of anthelmintic activity of ginger and curcumin on Ascaridia galli

Intestinal helmintic infection, continue to be a cause of major concern in several parts of the world, particularly in the developing nations. The use of plant extracts to control poultry helminths is increasing in different rearing systems. The anthelmintic activity of ginger and curcumin was studied on the nematode Ascaridia galli. In vitro and in vivo studies were allocated. Live parasites for in vitro studies were collected from the intestine of naturally infected chickens. Some living worms were incubated at 37 °C in media containing ginger at three concentration levels (25, 50, and 100 mg/ml), and others were incubated in media containing curcumin at the same concentration levels. Another living worm group was incubated in media containing albendazole at a dose of 7.5 mg/ml. The extracts' efficacy was exhibited in a concentration-time-dependent manner mainly at 100 mg/ml and after 48 h. The in vivo study takes place on experimentally infected chickens. Group of infected chickens was treated with ginger extract at dose of 100 mg, another group was treated with curcumin extract at dose of 100 mg, and a third group was treated with albendazole at dose of 7.5 mg. In vivo study of ginger and curcumin recorded lower mortality rates than the in vitro study. It is concluded that ginger and curcumin extracts have potential anthelmintic properties against A. galli. Ginger in all concentrations used exhibited a higher death rate observed than curcumin. Their wormicidal effect is concentration-time dependent.