Anthelmintic activity of ivermectin against experimental Ascaridia galli infection in chickens

The efficacy of ivermectin against Ascaridia galli infection was evaluated in chickens under controlled laboratory conditions in two separate experiments. In each experiment 22 White Leghorn chicks were randomly assigned to three groups of 10 (infected-treated), 9 (infected-control) and 3 (uninfected-control) birds. Each bird in the former two groups was orally infected with 1,500 embryonated A. galli eggs. The chicks in the treated group were subcutaneously injected with ivermectin at a dose of 0.3 mg kg-1 body weight on Day 10 (Experiment 1) and Day 35 post-infection (Experiment 2) for immature and adult infections, respectively. The treated birds had 0.9% (Experiment 1) and 0.4% (Experiment 2) worm recovery compared with 8.7 and 8% in the infected-untreated controls of the respective experiments. The fall in post-treatment faecal egg counts was 81 and 92% in birds treated on Days 10 and 35, respectively. The drug was found to be 90 and 95% effective against immature and adult worms, respectively. The lower lesion score and post-treatment near-normal haematobiochemical picture in treated birds confirmed these observations. The treated birds also had a better growth rate than the untreated chickens. The mature worms in the intestinal lumen of the host were more sensitive to the treatment than the immature stages of the parasite in the tissue phase.     

Establishment of Ascaridia galli in betamethasone-treated chickens

Twenty-five day-old White Leghorn chickens were each infected orally with 500 (Group I), 1000 (Group II) and 2000 (Group III) infective eggs of Ascaridia galli and were killed 30 days after the infection. A high percentage of the infecting dose (6.5%) established as adult worms in the intestine of chickens receiving the lowest level of primary infection, but as the amount of primary infection given to birds increased, there was a significant fall in the percentage establishment of adult worms in the intestine. A similar pattern of worm establishment was shown by chickens of the same age and receiving similar levels of primary infections, but which were treated with betamethasone at a dose of 2 mg/kg body weight commencing 5 days before and continuing up to 15 days after the infection. Betamethasone-treated birds, however, showed more establishment of worms in the intestine, but lower weight gains in comparison to the birds which were not treated. Different levels of primary infections given, with or without treatment with betamethasone, had no effect on the sex ratio of the resultant male/female worm populations, which became established in almost equal numbers in the intestine of chickens.     

The effect of concurrent infections with Pasteurella multocida and Ascaridia galli on free range chickens

Pasteurella multocida and Ascaridia galli are observed with high prevalences in free range chickens in Denmark, but the impact is unknown. A study was carried out to examine the interaction between A. galli and P. multocida in chickens and the impact on production.Five groups, each with 20 18-week-old Lohmann Brown chickens were infected. Group 1 was orally infected with 1000+/-50 embryonated A. galli eggs. Group 2 received 10(4) cfu P. multocida intratracheally. Group 3 was infected with A. galli and subsequently with P. multocida. Group 4 was infected with P. multocida followed by A. galli. Group 5 was the control. The study ran for 11 weeks where clinical manifestations, weight gain and egg production were recorded. Excretion of P. multocida was determined on individual basis and blood smears were made for differential counts. At the end of the study pathological lesions and the number of adult worms, larvae and eggs in the faeces were recorded.The birds were more severely affected when infected with both pathogens compared to single infections with A. galli or P. multocida, respectively. A lower weight gain and egg production was observed with dual infections. A. galli infection followed by a secondary P. multocida infection resulted in more birds with pathological lesions and continued P. multocida excretion.In conclusion a negative interaction between A. galli and P. multocida was observed and it is postulated that free range chickens are at higher risk of being subjected to outbreaks of fowl cholera when they are infected with A. galli.     

Genetic resistance to Ascaridia galli infections in chickens.

Ascaridiosis is still a cause of economic losses in modern poultry production systems. Improving genetic resistance to this disease provides an attractive alternative for free-range organic poultry producers and will eventually reduce the extensive use of anthelmintic drugs. An experiment was conducted to compare resistance to Ascaridia galli infections in Lohman Brown (LB) and Danish Landrace (DL) chickens. A self-cure mechanism to A. galli infections was observed in both breeds. However, significantly higher worm burdens and egg excretion were seen in the DL compared to LB chickens during primary infection. This indicates that breeding for resistance to A. galli is possible in chickens.     

Localization of Ascaridia galli larvae in the jejunum of chickens 3 days post infection

The normal habitat of the parasitic stages of Ascaridia galli is in the small intestine of poultry but the exact localization is poorly understood. Therefore, a histological study was conducted in order to localize the larvae during the early phase of infection. Six layer pullets seven-week old were infected orally with 20,000 embryonated A. galli eggs each, whereas four chickens were left as un-infected controls. At necropsy 3 days after infection the first half of jejunum/ileum was divided into two equally sized sections (J1 and J2). After taking samples for histology from the middle of J1 and J2 and the junction between these determined JX, the two sections were subjected to parasitological examination. A higher number of A. galli larvae were recovered from section J2 than J1 and the majority of larvae were recovered from the most profound layers. Based on histology 144 larvae were identified and their location was noted. The highest number of larvae was observed in the JX sample as compared to J1 and J2 (P<0.001). Most of them were located in the profound crypt zone of the mucosa (51%) as compared to the other zones (P<0.05). The number of larvae was higher in the lumen (63%) compared to the epithelium (32%) and lamina propria (5%) (P<0.001). A significantly higher number of eosinophils were found in lamina propria of the infected group compared to the control group (P<0.001). This experiment clearly showed that only few larvae had penetrated the epithelium and were positioned in the lamina propria at 3 days post infection. It was far more common that the larvae were localized within the epithelium or in the lumen of the crypts. It is therefore suggested that at least in this early phase "mucosal phase" is a more appropriate term to be used for the A. galli larval localization as compared to the term "histotrophic phase" currently used in many textbooks.     

Age-related differences of Ascaridia galli egg output and worm burden in chickens following a single dose infection

Ninety white chickens (Lohmann LSL) were reared under helminth-free conditions and divided into five groups. Four groups were artificially infected with 250 embryonated Ascaridia galli eggs at the age of 6, 12, 18 or 24 weeks. Ten birds were kept as uninfected controls. Six and 10 weeks after infection (p.i.), individual faecal egg counts (FEC) were performed. The birds were slaughtered after the second sampling and their gastrointestinal tracts were examined for the presence of adult A. galli. The FEC increased from the first to the second sampling significantly in all the infected groups. The highest increase was shown in the group infected at 12 weeks of age, whereas the increase in the other groups was relatively moderate. However, the total worm burden and mean FEC at the second sampling were highest (p<0.01) in those birds infected at an age of 12 or 18 weeks. The serum protein and triiodothyronine (T3) levels did not differ significantly (p>0.05) between any of the groups. Thyroxine (T4) was significantly different between the groups infected at 6 and 18 weeks of age (p<0.05), and those at 6 and 24 weeks of age (p<0.01). The thyroid hormone levels correlated significantly with the FEC. Age does not seem to play a major role in resistance to A. galli infections in layers, whereas a bird's hormonal and immune status, related to laying activity, seems to have a significant negative impact on resistance.     

Does Plasmodium gallinaceum induce relapse of Eimeria acervulina infection in chickens?

An experiment was carried out to test the hypothesis that chickens previously infected with Eimeria acervulina, but having ceased producing oocysts, recommence E acervulina oocyst production when infected with Plasmodium gallinaceum. No relapse of coccidiosis was caused by the malarial infection. Subsequent treatment with the immunosuppressant betamethasone of the control chicks infected with E acervulina only did not reveal any occult coccidial infection. The results are critically compared with previously published results which apparently supported the hypothesis.     

Effect of irradiated Ascaridia galli eggs on growth and cell-mediated immune responses in chickens

Growth and cell-mediated immune (CMI) responses were studied in 7-day-old chicks given orally 1000 irradiated (12.5 kR) or normal infective eggs of Ascaridia galli. Chicks immunised with irradiated eggs showed normal weight gains. CMI responses, as assessed by dinitrofluorobenzene (DNFB)-induced contact and delayed hypersensitivity reactions, were enhanced in the immunised group as compared with healthy controls, suggesting stimulation of CMI responses due to irradiation of A. galli eggs. CMI as well as growth responses were, however, found to be depressed in the birds administered normal infective eggs of A. galli. The present study highlights the role of the CMI response in protection against A. galli infection.     

Comparison of parasite-specific immunoglobulin levels in two chicken lines during sustained infection with Ascaridia galli

Increasingly large numbers of poultry are held in production systems with access to outdoor areas. In these systems intestinal helminths are found with flock prevalences of up to 100%. Helminth infections influence chicken health negatively, which is why the following investigation has been performed.In the present experiment, 20 chickens of two inbred chicken lines containing the major histocompatibility complex (MHC) haplotypes, B14 and R5, were inoculated with 500 embryonated Ascaridia galli eggs. The A. galli-specific IgG titres of serum samples and the excretion of A. galli eggs in chicken faeces were measured for a period of 81 weeks.The level of excreted A. galli eggs measured as eggs per gram chicken faeces (EPG) varied greatly between chickens in each line. Significant differences were found between the two lines and with the R5 chickens reaching the highest levels. Likewise, the A. galli-specific IgG titres in serum differed significantly between the two lines, and an inverse relationship between infection level (EPG) and antibody titres was found. Although this inverse relationship suggests that humoral immunity may be involved in protection against A. galli infection, the high antibody titres did not prevent continued infection.     

Response of two breeds of chickens to Ascaridia galli infections from two geographic sources

Comparative resistance to different isolates of Ascaridia galli was investigated in a local chicken breed from Jordan (LC) and in the Lohmann LSL white chicken (LW) strain. In two trials, birds of LC and LW were inoculated orally at 1-day old with 250 embryonated A. galli eggs. In the first trial a German source of A. galli was used, whereas in the second trial, a Jordan source of A. galli was used. At week 7 of infection, infected LC birds harbored significantly (P<0.05) fewer worms and excreted less A. galli eggs than infected LW birds. A. galli isolated from Jordan were less infectious than A. galli from Germany. Results suggest that the variation in genetic background between LC and LW is involved in the resistance to A. galli infection. A. galli isolates from different geographic areas differ in their ability to infect different chicken genotypes.     

Effect of anthelmintics on phosphatases in Ascaridia galli.

In vitro addition of the drugs tetramisole (TMS) and levamisole (LMS) caused an inhibition of the specific activities of acid phosphatase and Mg(++)-dependent adenosine triphosphatase. The inhibition was non-competitive in nature. No significant inhibition was caused by TMS in the activity of glucose-6-phosphatase, but LMS inhibited the enzyme in a non-competitive manner. The activity of alkaline phosphatase was, however, increased in the presence of both TMS and LMS.     

The development of Plasmodium gallinaceum infections in chickens following single infections with three different dose levels

In the present study, groups of 5-day-old chickens were inoculated intravenously with approximately 10(6), 10(4) or 10(2) P. gallinaceum-infected erythrocytes. The outcome of disease in relation to dose level was evaluated in terms of number of parasitized erythrocytes, change in number of erythrocytes, pathological changes of organs and the course of exo-erythrocytic stages of the parasite in various organs over a period of 8 weeks. Mean weight gain and mortality were also recorded. With regard to differences between the size of the inoculation dose and the severity of disease, relationships could be observed in relation to clinical signs, mortality, prepatent period, exo-erythrocytic parasites and severity of pathological changes in organs, but in relation to weight gain, erythrocyte loss and number of parasitized erythrocytes no relationships were observed.     

The effect of levamisole and albendazole on some enzymes of Ascaridia galli and Heterakis gallinae

Ascaridia galli and Heterakis gallinae obtained from the common fowl Gallus gallus were exposed to 10(-2)-10(-5)M levamisole and albendazole; both compounds caused death of the parasites in vitro. The effect of the drugs was investigated on homogenates of the treated worms. Albendazole, at 10(-2)M, inhibited oxaloacetate reduction by 67 and 53% and malate oxidation by 21 and 17% in A. galli and H. gallinae, respectively, whereas 10(-4)M levamisole completely inhibited malate dehydrogenase activity in both directions in the two parasites. Lactate dehydrogenase was not affected significantly by either anthelmintic. Aldolase activity was diminished by 57 and 32% in A. galli and H. gallinae, respectively, with 10(-4)M levamisole. Levamisole at 10(-4)M also inhibited the activity of acid and alkaline phosphomonoesterase and cholinesterase. Albendazole had no significant effect on these enzymes in either parasite. Malate dehydrogenase and cholinesterase activity of the host tissue (intestine and caecum) was also reduced significantly with 10(-2) and 10(-3)M levamisole. These studies indicated a multiple mode of action of levamisole and albendazole.     

Effect and repeatability of Ascaridia galli egg output in cockerels following a single low dose infection

Three groups of caged 20 Tetra-SL cockerels aged 1 day were orally infected with 30, 60 or 125 embryonated Ascaridia galli eggs. After 11, 12 and 13 weeks, faecal egg counts (FECs) were determined. All birds were slaughtered after the last sampling. A group of 25 control birds was sampled and slaughtered in parallel. The gastrointestinal tracts were examined for the presence of adult stages of A. galli. A random sample of 10% was also examined for the presence of immature stages of A. galli. The group with an infection dose of 125 eggs showed the highest average worm burden (p<0.05) and number of females (p<0.05), but the mean establishment rate was the lowest in this group. There was no significant difference in the mean logFEC between the groups. The logFEC per female worm was the highest in the low infection group (p<0.05). The average worm length and weight and the birds body weight were not significantly different among the groups. The estimated repeatabilities for mean logFEC of the different samples were reasonably high (0.55-0.87). This may open a way of genetic selection for A. galli resistance in chickens, which will be of importance for birds kept in alternative and organic farming systems.