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Updated: Feb 11, 2026
Nucleofection and In Vivo Propagation of Chicken Eimeria Parasites
Published on: February 14, 2020
Evaluation of autofluorescent Eimeria maxima oocysts as a potential indicator of non-viability when enumerating
L C Beer1, L R Bielke2, J R Barta3
1Division of Agriculture, Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, AR 72701, United States.
Abstract:
Aging, poor oxygenation, or improper storage temperature can lead to variable Eimeria oocyst viability, which is not readily assessed microscopically. Under fluorescent microscopy, some aged Eimeria maxima (EM) oocysts were strongly autofluorescent (AF) within the oocystoplasm and sporocysts, whereas others were distinctly non-fluorescent, leading to the hypothesis that non-viable oocysts may be detectible using this simple approach. Using accelerated aging conditions at 45°C, two experiments were conducted to evaluate variable percentages of autofluorescent EM oocysts on body weight gain (BWG), lesion scores (LS), and total oocyst shedding (OS) per bird. Through oral gavage, EM oocysts were administered on d10, whereas LS and BWG were determined d5 post-inoculation. Experiment 1 groups consisted of non-challenged controls (n = 15), or 25,000 EM exhibiting 12.8% (n = 14), 61.1% (n = 10), or 93.3% (n = 10) autofluorescence. BWG in 12.8% AF group was lower (P = 0.054) than non-challenged control. LS were higher (P < 0.05) in 61.1% and 12.8% AF groups as compared to non-challenged control and 93.3% AF groups. Experiment 2 groups consisted of non-challenged controls (LS n = 20/BWG n = 40), or 22,500 EM exhibiting 7% AF (LS n = 20/BWG n = 40), 80.6% AF (LS n = 19/BWG n = 39), or 99% AF (LS n = 19/BWG n = 39). BWG in 7% AF group was lower (P < 0.05) than non-challenged control and 99% AF groups. LS were higher (P < 0.05) in 80.6% and 7% AF groups as compared to non-challenged control and 99% AF groups. OS from d5-8 post-inoculation was determined for each of five replicates per group (n = 20/group; n = 4/replicate), with higher (P < 0.05) OS in 80.6% and 7% AF groups than in non-challenged control or 99% AF groups. Taken together, data indicate lower LS, higher BWG, and reduced OS with higher %AF oocysts, consistent with the hypothesis of lowered viable challenge with this EM isolate.
Insights
Autofluorescence under microscopy can indicate Eimeria maxima oocyst viability. Higher autofluorescence percentages in Eimeria maxima oocysts correlate with reduced lesion scores and oocyst shedding, suggesting lower infection challenge.
Area of Science:
- Veterinary Parasitology
- Poultry Health
- Microbiology
Background:
- Eimeria oocyst viability is crucial for infection challenge but difficult to assess microscopically.
- Aging and storage conditions affect oocyst viability.
- Autofluorescence (AF) under fluorescent microscopy is a potential indicator of Eimeria oocyst non-viability.
Purpose of the Study:
- To investigate the correlation between Eimeria maxima (EM) oocyst autofluorescence (AF) and infection parameters.
- To evaluate if AF can predict oocyst viability and subsequent host response.
Main Methods:
- Two experiments using accelerated aging (45°C) of EM oocysts with varying AF percentages (7% to 99%).
- Oral gavage administration of EM oocysts to birds.
- Assessment of body weight gain (BWG), lesion scores (LS), and oocyst shedding (OS) post-inoculation.
Main Results:
- Higher AF percentages in EM oocysts were associated with lower lesion scores (LS) and reduced oocyst shedding (OS).
- Body weight gain (BWG) was negatively impacted in groups with lower AF percentages.
- Data suggest that higher AF correlates with a reduced viable challenge from EM oocysts.
Conclusions:
- Autofluorescence is a promising, simple method for assessing Eimeria oocyst viability.
- Increased autofluorescence in Eimeria maxima oocysts indicates reduced pathogenicity.
- This finding aids in evaluating oocyst quality for research and vaccine development.
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