Ascaridia galli - An old problem that requires new solutions.

Reports of Ascaridia galli in laying hens in Europe have increased since the ban on conventional battery cages in 2012. As this parasite is transmitted directly via the faecal-oral route by parasite eggs containing a larva, it is reasonable to assume that the escalating problem is related to the increased exposure now occurring in modern welfare-friendly cage-free housing systems. On many farms, A. galli reappears in subsequent flocks, even though the birds have no access to the outdoors, biosecurity is high and empty houses are cleaned and disinfected during downtime. Since the egg production cycle lasts only ≈80 weeks and recombinant antigen production for helminth vaccines has not yet been solved, the development of a vaccine seems to be an unrealistic option. Therefore, disrupting the life cycle of the parasite by other means, including the strategic use of dewormers, appears to be the key to controlling infection. Of concern is that only one class of anthelmintics is licenced for poultry in Europe and that are usually administered indiscriminately through the birds' drinking water and often too late when the parasite is already established. If current calendar-based parasite control strategies are not changed, there is a risk that resistance to anthelmintics may develop, as has already been demonstrated with nematodes in livestock. We insist that treatments can be more effective and the risk of developing drug resistance can be mitigated if we invest in a better understanding of A. galli responses to more prudent and judicious use of anthelmintics. This review identifies knowledge gaps and highlights aspects of sustainable parasite control that require further research to support commercial egg producers.

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

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.

Pharmacokinetics and therapeutic efficacy of levamisole in Ascaridia galli experimentally infected ducks.

This study investigated the pharmacokinetics and therapeutic efficacy of levamisole (LVS) after intravenous (i.v.) and oral administrations to healthy and Ascaridia galli-infected ducks by developing an infection model. Twenty-four two-week old ducklings were experimentally infected with A. galli. The ducks were monitored for the development of infection and after 8 weeks they were administered with LVS at a single dose of 30 mg/kg by oral or i.v. administration. Sixteen healthy ducks were subjected to the same treatment and served as control. Serial blood samples were taken for LVS determination with HPLC-UV and pharmacokinetic analysis was carried out based on the non-compartmental approach. The LVS therapeutic efficacy was determined 1 week post drug administration by intestinal worm count at necropsy. In vivo data on development of ascariasis in ducks showed that 8 weeks post inoculation the number of eggs per gram of feces reached at least 100 in each bird. After a single dose of LVS, no parasites were recovered upon necropsy. Results of the pharmacokinetic study showed no statistical differences between infected and non-infected birds for both routes of administration. The mean oral bioavailability was slightly below 50% in both experimental groups. In conclusion, the pharmacokinetics of LVS in ducks was not affected by experimentally-induced ascariasis. A single dose of LVS was found to be efficient against experimental ascariasis in ducks induced by in field isolates of A. galli.

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.

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.

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.

Safety of fenbendazole in common peafowl (Pavo cristatus).

The present study was undertaken to find out the safety levels of fenbendazole in common peafowl. This bird, raised on aviaries and zoos, can be severely parasitized with Ascaridia galli (enteric worms) and Syngamus trachea (gapeworm) along with other parasitic worms. Fenbendazole is a highly effective benzimidazole-class anthelmintic in animals. The objective of this work was to provide target animal safety data in young peafowl and to demonstrate reproductive safety in adult birds. During the experimental study, diets containing fenbendazole at 0, 100, 200 and 300 ppm were fed for 21 days (three times the normal treatment duration). Data for feed consumption, feed conversion rate, and body weights were recorded for each bird in each group. Drug concentrations in different tissues of birds were determined to correlate concentrations with clinical observations, clinical pathology, and histologic findings. There were no morbidities or mortalities after study day 21. Additionally, there were no statistically significant treatment-related differences among above mentioned parameters. Analysis of fenbendazole concentrations in kidney, liver, leg/thigh, and breast muscle and skin with associated fat revealed that, even at the highest dose level used and with no feed withdrawal, fenbendazole concentrations were relatively low in these tissues. These findings indicate that fenbendazole has a relatively wide margin of safety in young peafowl and that the proposed dose of 100 ppm in the feed for 7 consecutive days is well within the margin of safety. In the reproductive safety study, five breeder peafowl farms fed fendbendazole at 100ppm for 7 days and collected data on hatching percentage of peahen eggs before and after treatment. Reproductive performance in peahen was not adversely affected.

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 ß-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 ß-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.

Comparison between anthelmintic treatment strategies against Ascaridia galli in commercial laying hens.

The efficacy of a sustainable deworming strategy based on targeted treatments (TT) against Ascaridia galli was investigated for the first time in laying hen flocks on a Swedish commercial farm. Three experimental protocols with different levels of treatment, e.g. targeted treatment (TT), conventional treatment (CT) and untreated (UT), were tested in randomly allocated flocks of two different bird hybrids. Every second week faecal egg counts (FECs) were determined from pooled faecal materials collected on trays (20×27cm) placed for a maximum of 12h on the litter belts. In the TT, anthelmintic administration (fenbendazole, 1mg/kg body weight for 5days) started at 22 weeks post placement (wpp) and was repeated twice when the pooled FECs surpassed the assigned threshold of 200 egg per gram faeces (EPG). The CT flocks were treated once at 27wpp using the same anthelmintic. Hens in the UT were not dewormed and served as controls. Additionally, FECs on cloacal contents, worm fecundity and worm burdens were determined at 19, 35 and 45wpp. None of the flocks became infected until after 16wpp. The cumulative pooled FECs at the end of the study were significantly (p<0.01) lower in the TT compared to both CT and UT. Although repeated treatment in the TT protocol did not affect the fecundity, a worm density-dependent increase in fecundity was observed. Cloacal FECs and the number of adult A. galli in TT at 35 and 45wpp were significantly lower compared to other flocks. This study provides evidence that the TT strategy is better in terms of lower worm burden and decreased cumulative environmental parasite egg numbers compared to CT strategy. The TT strategy should be considered as an alternative to the CT strategy with regard to A. galli control in commercial laying hens.

The efficacy of flubendazole against different developmental stages of the poultry roundworm Ascaridia galli in laying hens.

Infection with the poultry roundworm Ascaridia galli has increased in European countries due to the ban on battery cages. This study was conducted in two commercial laying hen flocks (F1 & F2) on different farms in central Sweden. The aims were to (1) investigate the efficacy of flubendazole (FLBZ, 1.43 mg/kg administered in drinking water for 7 days) against adult and larval stages including histotrophic larvae of A. galli, and (2) determine how long it took before the flocks were reinfected after deworming. Accordingly, 180 randomly selected hens were sacrificed before drug administration (bd), on day 3 and 7 during drug administration (dd), and on a weekly basis for up to five weeks post drug administration (pd). Intestinal contents and cloacal materials of each hen plus pooled faecal samples from manure belts were investigated to assess the worm burden and the parasite egg per gram faeces (epg). Additionally, drinking water, and serum and gastrointestinal digesta content samples obtained from ten treated animals were analyzed by HPLC to measure FLBZ and its reduced (R-FLBZ) and hydrolyzed (H-FLBZ) metabolites. No parasite eggs were observed in cloacal samples on day 21 and 28 pd on F1 and on day 21 pd on F2. The epg in manure decreased by 65% and 88% on day 3 dd and by 99% and 97% on day 35 pd on F1 and F2 respectively. Mean FLBZ concentrations quantified in duodenal contents ranged between 0.50 and 0.79 µg/g. Although, no histotrophic larvae were found dd, they reappeared one week pd (7 ± 7 F1, 0.5 ± 0.5 F2). Adult worms were found in both flocks before drug administration (44 ± 20 F1, 35 ± 25 F2), on day 3 dd (4 ± 3 F1, 2 ± 2 F2), and then not until day 35 (0.2 ± 0.6) on F1 and day 28 (0.4 ± 0.9) pd on F2. Thus, the only period in which no A. galli were found was on day 7 dd. Although FLBZ was highly efficient our results indicate that the birds were reinfected already within one week pd.

Anthelmintic effects of citrus peels ethanolic extracts against Ascaridia galli.

The use of phytogenic bioactive compounds to control poultry helminthes is increasing in different production systems. In vitro and in vivo anthelmintic activity of citrus peels against Ascaridia galli was investigated. Ethanolic extracts of three citrus peels species were suspended in 0.5% dimethyl sulfoxide (DMSO) to form an experimental composition (EC). EC was mainly composed of Limonene (96%), followed by ß-Pinene (1.5%), α-Pinene (0.5%), and Sabinene (0.3%). For in vitro investigation, adult A. galli worms (n=225) were collected from naturally infected chickens and distributed to 3 equal groups. Groups 1, 2, and 3 were exposed to Fenbendazole (0.5mg/ml), EC (50mg/ml), and 0.5% DMSO, respectively. For in vivo investigation, 200 Lohmann Selected Leghorns chicks were infected at 1-day old with 250 embryonated A. galli eggs. At 6 weeks of age, 150 A. galli infected birds were randomly allocated into 5 equal groups. Groups 1, 2, and 3 were treated with 300, 600, and 1200 mg EC kg(-1) body weight, respectively. Group 4 was treated with Fenbendazole (50 mg kg(-1)). Group 5 was left as control. Birds were euthanized 2-weeks post-treatment, and all worms were collected from their intestines. EC possessed significant (P<0.001) in vitro anthelmintic properties on live worms. No significant (P>0.05) difference was quantified between number of motile worms exposed either to EC or Fenbendazole 7h post-exposure. A significant (P<0.0001) reduction in fecal egg count was observed 14 days post-treatment with 1200 mg kg(-1) EC. No significant differences were observed in worm burden of the 300 mg EC-treated group compared to the controls. In contrast, the 600 and 1200 mg EC-treated groups showed significant (P<0.0001) reduction in worm burden. Fenbendazole was the most effective in reducing A. galli burden (Efficacy=97%) followed by 1200 mg EC kg(-1) (68%), 600 mg EC kg(-1) (66%), and 300 mg EC kg(-1) (5%). It is concluded that citrus peels extracts have potential anthelmintic properties against A. galli.

Efficacy of allicin from garlic against Ascaridia galli infection in chickens.

The use of garlic as a treatment against helminth infections is increasing in organic layer farms in several European countries. Its efficacy against these parasites, however, has not been demonstrated thus far. Therefore, a study was conducted to determine the efficacy of a commercially available garlic product consisting of a high concentration of allicin (i.e., the main active component of garlic) against experimentally induced Ascaridia galli infection in chickens. In total, 450 Lohmann LSL-Classic cockerels were used. Group 1, the uninfected, untreated group, consisted of 50 chickens. Groups 2 to 5, each consisting of approximately 100 chickens, were inoculated with 300 embryonated A. galli eggs/chicken at 6 wk of age. Group 2 was not treated, whereas groups 3 through 5 were given daily individual oral treatments from 13 wk of age onward. Group 3 received the recommended dose of allicin for 2 wk, whereas group 4 received a 10-fold dose of allicin. Group 5 was given 10 mg of flubendazole/kg of BW for 1 wk. Necropsy of 20 birds of all groups was performed weekly between 13 and 16 wk of age to determine adult worm loads. Group 1 remained free of A. galli. The experimental infection in the other groups resulted in a mean adult worm load of approximately 16 worms/bird. No significant differences were observed in worm counts of the allicin-treated groups (groups 3 and 4) compared with the infected, untreated group (group 2) at any week (P > 0.05). In contrast, no worms were found in chickens after flubendazole treatment (group 5). It was concluded that allicin does not represent an alternative to flubendazole for the treatment of A. galli infections in chickens.

Effect of extra dietary lysine in Ascaridia galli-infected grower layers.

The hypothesis examined in this study was that extra dietary lysine (Lys) above the recommended standard exerts beneficial effects on the defence reactions, growth performance and nutrient utilization in Ascaridia galli-infected chickens. Therefore, 1-day-old female Lohmann Selected Leghorn chickens were at first fed standard Lys diet (8.5 g Lys/kg DM). At 4 weeks of age, the birds were allocated to groups 1 and 3, both being continued on standard Lys diet, whereas birds in groups 2 and 4 were switched to extra Lys diet (10.5 g Lys/kg DM). Birds in groups 3 and 4 were additionally infected at this age (4 weeks) with 250 embryonated eggs of A. galli. All the birds were slaughtered 7-week-post-infection (p.i.) at an age of 11 weeks. Infected birds on standard Lys diet consumed more feed and reached a similar level of Lys intake as birds on extra Lys diet 7-week-p.i. Utilization of feed, crude protein, and Lys for body weight (BW) gain was adversely affected in infected birds on standard Lys diet (P<0.001). Extra Lys diet reduced the incidence of infection (P<0.05), but worm counts, worm length, faecal egg counts and female worm fecundity were not different between the infected groups (P>0.05). Extra Lys diet led to higher final BW in uninfected and infected birds (P<0.05). It is concluded that extra Lys above the normal recommended standard supports the defence reactions and compensates the negative effect of infection on growth performance and nutrient utilization in A. galli-infected birds.

Case of retinochoroiditis associated with porcine ascarids diagnosed by antibodies in subretinal fluid.

PURPOSE: To determine the cause of retinochorioditis in a patient with a granulomatous retinal exudate and an exudative retinal detachment. CASE: A 45-year-old man presented at another hospital with increased visual disturbances of the left eye. He was diagnosed with uveitis, and treated with topical steroids for 1 month. However, the uveitis worsened, and he was referred to our hospital. Ophthalmoscopy showed a yellowish-white granulomatous exudate, and an exudative retinal detachment in the lower peripheral retina. The retinal detachment worsened and affected the macula. Pars plana vitrectomy was performed, and the retina was reattached. During the surgery, ocular samples were collected for further examinations. The titers of antibodies against 12 kinds of ascaridis were examined, and elevated titers of specific antibodies against porcine ascarids were detected in the subretinal fluid, but not in the aqueous humor, vitreous, or serum. CONCLUSIONS: Vitrectomy with the collection of ocular samples, especially subretinal fluid, was a key procedure in the diagnosis and treatment of retinochoroiditis associated with the porcine ascarids.

Effect of selenium and Ascaridia galli infection on antioxidant biomarkers in broiler chickens: a mathematical model for parasite reduction and host growth.

The activity of selenium-dependent glutathione peroxidase (GPX), liver concentration of vitamin E, and plasma and liver selenium levels were used for estimation of the antioxidant status of broiler chickens infected with Ascaridia galli. These biomarkers were recorded in an experiment covering 70 days p.i. At the same time the establishment rate of A. galli in chicken intestines, gain in the host body weight and chicken survival were studied. Broiler chickens (Cobb hybrids) were infected with 1450 embryonated A. galli eggs and treated with Sel-plex. A mathematical model was applied to determine the rate of nematode reduction and the relative rate of gain of host body weight, which are essential kinetic parameters of parasite-host interaction. The activity of GPX increased with both elevated selenium and reduced infection levels. The concentrations of selenium and vitamin E, and the GPX activity in the infected chickens demonstrated a similar pattern of change with time after day 30 p.i. The supplementation of the broilers with dietary selenium in the form of Sel-plex improved their antioxidant status. Increases by 29% in vitamin E concentration, 15% in GPX activity, and 22% in liver selenium concentration, respectively, were recorded in the infected and treated, compared to infected and untreated broilers.

Influence of Ascaridia galli infections and anthelmintic treatments on the behaviour and social ranks of laying hens (Gallus gallus domesticus).

In the present study, the effects of an experimental Ascaridia galli infection and anthelmintic treatment on the behaviour and social status of laying hens of two different lines were studied. Sixty white (Lohmann LSL; LSL) and 60 brown (Lohmann Brown; LB) hens were reared under helminth-free conditions. The hens of each line were divided into four groups. The birds in two of the groups were artificially infected with 250 embryonated A. galli eggs at an age of 27 weeks. The other two groups were kept as uninfected controls. One infection and control group was dewormed at 38 weeks of age and slaughtered 4 weeks later, contemporary with the other animals. Individual faecal Ascaridia egg counts (FEC) were performed 11 weeks post-infection (p.i.). Body weights, laying performance and egg weights were recorded regularly. Blood was taken to measure testosterone levels. The worm burdens established in the intestines were counted in the infected not treated group after slaughtering. In addition, 15 behavioural parameters were recorded by focal animal observation (n=10 per group) of one infection (plus anthelmintic treatment) and one control group, according to the time-sampling method throughout the experiment. All agonistic interactions within the groups were recorded simultaneously on an ongoing basis, thereby allowing the calculation of an individual social rank index. The following results were obtained: Mean FEC and worm burden were higher (p < 0.01) in the LSL hens than in the LB hens, but their performances were not different (p > 0.05) from the controls. Infections with A. galli resulted in significant behavioural changes in both lines as the infected birds showed a higher food intake and lower locomotion activity during the prepatent and patent periods. After anthelmintic treatment, food intake decreased and locomotion increased. Behavioural changes were more pervasive in the infected LSL hens, as these hens also showed changes in ground pecking and nesting activity not only during the prepatent and patent periods, but also after anthelmintic treatment. Social rank did not significantly change as a consequence of A. galli infection, but the infection groups of both lines had a tendency to display more agonistic activity than the non-infected controls. Serum testosterone values only increased significantly in the LSL hens during the patent period compared to the controls. No significant correlations were apparent between serum testosterone level, parasitic parameters, social status and/or aggressiveness in any of the groups. This study showed that even sub-clinical A. galli infections and their anthelmintic treatment can have an impact on animal behaviour.

Administration of Zn-Co-Mn basic salt to chickens with ascaridiosis. II. Sex ratio and microelement levels in Ascaridia galli and in treated and untreated chickens.

Hisex chickens were infected with 1,450 embryonated Ascaridia galli eggs and treated with a new synthesized basic mixed salt (Zn(x)Co(y)Mn(1-x-y)) x (OH)6SO4 x 2H2O). The worm burden was determined and sex ratios for A. galli of M:F = 1.4 and M:F = 2 in untreated and treated chickens, respectively, were found. A decrease in the mean establishment rate of A. galli in treated chickens was observed. The levels of zinc, cobalt and manganese were determined in liver and muscle of the host and in male and female A. galli. The survival of the chickens and gain in body weight were improved, and the restoration of microelement content was observed by treatment with the salt. A positive effect of the basic Zn-Co-Mn salt was also observed in the nematode microelement levels. Significant differences were found between the levels of zinc, cobalt and manganese in male and female A. galli.

Administration of Zn-Co-Mn basic salt to chickens with ascaridiosis. I. A mathematical model for Ascaridia galli populations and host growth with and without treatment.

A newly synthesized basic mixed salt (Zn(x)Co(y)Mn(1-x-y)) x (OH)6SO4 x 2H2O) was administered to chickens with ascaridiosis. Improvement in survival, gain in body weight (of 19.03%) and restoration of microelement content were observed in the treated chickens. An increase in the gain in body weight of 7.62% in uninfected treated chickens was also observed. The establishment of Ascaridia galli populations in chickens, and chicken growth in control and infected hosts, untreated and treated, were modelled mathematically. Some kinetic parameters (the rate of reduction of the nematode population nu and the relative rate mu of gain in body weight of the host) were determined. The values of nu =0.027 day(-1) and nu* =0.032 day(-1) were calculated for the reduction rates in infected, untreated chickens and in infected, treated chickens, respectively. The worm burden in infected, treated chickens was 20.4% lower than in infected, untreated chickens.