Ascaridia galli: Diagnosis, alternative treatments and influence on cytokine expression, microbiota, egg quality and digestibility

Abstract

Because of the trend of cage-free egg production, infections with the nematode Ascaridia galli are receiving increased attention. The aim of the first study was to evaluate and quantify the parasitological challenge in pastured poultry production. Fecal samples from turkeys, broilers and layers were collected in two-week intervals to determine counts of coccidia oocysts and worm eggs. Seasonal differences suggested that higher temperatures might increase worm egg survival in the environment. Counts of coccidia were lower than published numbers in conventionally reared poultry, indicating that the rotation system effectively reduced the infection pressure. However, this was not true for worm eggs. Next-generation sequencing showed the presence of most described Eimeria spp. in these birds. The second study established a timeline for the influence of A. galli on the expression of key cytokines and on the composition of the jejunal microbiota. Birds were challenged with 500 embryonated A. galli eggs for 3 consecutive days starting at 24 days of age. Starting on day 31, three birds of each group were euthanized weekly until 8 weeks post infection (WPI). The number of larvae isolated from the intestinal wall decreased over time. At 5 WPI, there was a numerical upregulation of all cytokines in the infected group compared with the uninfected control and significant differences in the intestinal microbiota between groups. The upregulation of all cytokines evaluated might be the reason for resolution of the infection. A high infection dose and a more nutritionally dense feed might have contributed to the birds’ immune system clearing the infection before the worms were able to reach maturity. The third study tested if Artemisia absinthium (0.02% in the feed) and pumpkin seed (1% in the feed) can alleviate potential negative effects of an A. galli infection on egg production and quality, nutrient digestibility, cytokine expression and intestinal microbiota. Sixteen-week-old laying pullets were divided into three groups: untreated control, treated with artemisia or pumpkin seed. At 25 weeks, half of the birds were challenged with 250 embryonated A. galli eggs. At 35 weeks, birds were euthanized, intestines were checked for worms and samples were collected. For all nutrients, digestibility was lower in challenged birds. Differences in cytokine expression were minor. Jejunal microbiota of treated birds showed an increase on Lactobacillales. None of the treatments were effective against A. galli, but had minor effects on alleviating the calcium digestibility reduction. This research provides evidence that nematodes have high prevalence on alternative production systems and tools for controlling the diseases are still needed.