Coccidosis – monitoring

Coccidial Oocyst in chicken.
Coccidial Oocyst in chicken.

These notes are are particularly relevant to broiler growers.

Signs of coccidiosis

The first indications you may have of a failure of the anticoccidial may be wet litter, watery droppings, poor growth, uneven chicks and perhaps, at worst, mortality. I have seen Caecal coccidiosis as early as 8 days of age and E.necatrix as late as 22 weeks of age.

A compounding issue these days is that there is an association between coccidiosis and necrotic enteritis.

It would appear that the damage that coccidia cause to the lining of the gut permits the clostridia that cause necrotic enteritis to gain a foothold. It would therefore seem that monitoring the degree of control that we achieve for coccidiosis would be a sensible thing to do.


There is a problem. Despite all the hard work done on coccidiosis, there is still no very simple way of predicting how and when a coccidiosis outbreak may occur. We can monitor various things but only after the infection has occurred.

  1. For example, you could take histological sections of the gut at specific ages and estimate how many coccidia we can see infecting the gut wall. This is time consuming and relatively expensive.
  2. You can cull a representative sample of birds at about 28 days of age and do lesion scores. This entails looking for the damage that the coccidia have already caused in specific parts of the intestine. However, not all species of coccidia cause visible damage.
  3. You can monitor litter or faeces and count the coccidial oocysts. The sampling method is very important and must be consistent from flock to flock.

Regular monitoring over time does allow a picture of the infection to be built up provided sample collection is consistent and the data that is provided with the samples is complete.

Litter samples.

These are undoubtedly the easiest to collect but they must be done in regular fashion.

1. Ensure that we always pick the same age of bird to sample, and I would suggest 28-29 days of age.

2. You will always need to use the same pattern for the selection of samples from across the house. Probably the simplest way is either to imagine the letter ‘W’ written across the floor of the house, or make an ‘X’ across the house from one corner to another.

3.Then, divide this into 12 sampling spots.

4.At each spot that you stop to take a sample, take a pinch-and I mean a pinch-of litter from in front of you, behind you and to your left and right. Then proceed onto the next sampling station. These are small samples, but spread across the house you will find that you have picked up quite a lot of litter.

5.This sample should then be identified and a note recording the age of the birds, house number, date, anticoccidial programme, especially the anticoccidial that the birds are on at the time of sampling and a note as to whether there have been any other problems.

The samples should then be posted in a jiffy bag back to the laboratory as soon as possible. This sampling regime would apply to routine sampling of every flock throughout the year.

Result and conclusions

You can expect to see differences as a result of the season and the anticoccidial programme that you are on.

Over time the correlation of a rising coccidial oocyst count with an increasing FCR would indicate that performance is being lost and a review of your anticoccidial programme is required.

D.G. Parsons MSc Cert PMP NSch MRCVS

November 2001

Copyright © 2002 D.G.Parsons M.R.C.V.S.

About David Parsons 19 Articles
David Parsons began his veterinary career in mixed practice which triggered his 39-year passion for poultry. Following positions as a veterinary research officer in the Poultry Department at the government’s Central Veterinary Laboratory and then as a poultry company veterinarian, he set up his own poultry veterinary practice in the southwest of England in 1985. He obtained his MSc in Applied Immunology in 1981, Certificate in Poultry Medicine and Production in 1989 and a Nuffield Farming Scholarship Trust to study the“Status of diseases specific to poultry and their control in Europe” in 1991.

He has been an Honorary External Lecturer at the University of Bristol Veterinary School on poultry medicine and production since 1999,a lecturer on the Institute of Animal Health’s poultry disease course since 2000 and is a regular monthly contributor of veterinary articles for backyard poultry keepers in the Practical Poultry magazine.