COCCIDIOSIS levels were consistently stable over the first 10 months of 2023 according to Elanco’s most recent broiler health tracking report.

It is the first period of coccidiosis stability for the UK’s broiler sector since 2021, according to Elanco.

See also: Broiler disease investigation – understanding the process 

Almost 6,000 birds from 438 individual sheds on 269 UK farms formed the sample, taken between January and October 2023.

Elanco uses a range of factors from post-mortem examinations to create an “intestinal integrity” score, which it calls the I2 index. This score is then used to give an overall picture of broiler gut health across the survey.

In 2022, national Intestinal Integrity (I2) scores dipped for several reasons, including changes in coccidial programmes and inconsistent raw material quality. As a result, a rise in coccidiosis cases was seen, a significant contributor to the I2 index.

However, the index started to improve towards the end of 2022 and remained stable in 2023, with average values similar to those in 2021.

Coccidia species prevalence

The trends for coccidia species follow a similar trend to the I2 index, with cases starting to return to pre-2022 levels.

James Bishop, Elanco’s monogastric technical consultant, explained the findings: “In 2023, 37.8% of birds were affected by E. acervulina, a decrease from 40.1% in 2022. This lower percentage is similar to that seen in 2021.

“Levels of E. acervulina remained relatively high throughout 2022, and this rolled over into early 2023. However, levels have gradually decreased to the lowest values since pre-spring 2022. 

“This is likely due to producers returning to long-term Narasin based programmes in late 2022, regaining some consistency and improving stability throughout 2023.”


Of the 2,241 birds showing E. acervulina lesions, 69.2% were mild (score one), 25.6% were moderate (score two) and 5.2% were severe (scores three/four).

However, the report demonstrates 10.5% of birds presented with gross E. maxima. While this is on a par with 2022 levels, it is a 50% increase from 2021. 

“As the largest species of coccidia, E. maxima can cause the most harm to the intestinal tract without causing mortality, having a significant impact on farm performance and profits,” added Dr Bishop. 

Emaxima can be hard to manage in the winter months, and due to the wetter summer in 2023, producers have struggled to reduce levels back to where they were in 2021.

“The fluctuating levels seen over 2023 show how anticoccidial programme instability can lead to lasting changes which impact birds through future crops.”


The species most likely to cause mortality in the bird, clinical E. tenella, is not often seen within the average UK broiler house. The report reveals that in 2023, 5.3% of birds presented gross E. tenella lesions, a five-fold increase from 2021.

“The spring of 2023 saw a steady decrease in the levels of E. tenella since the spike in levels in Autumn 2022,” said Dr Bishop.

“However, in May 2023, levels started to rise again and remained higher through the summer than in 2021 but are lower than that of 2022, this effect is likely due to the challenging weather conditions that were experienced last summer, and a higher environmental challenge compared to the previous year.” he concluded.

The full report is available here.