Coccidiosis is one of the oldest known diseases in poultry. It was described already by Tyzzer in 1927. Up till today, it causes major economic losses worldwide. Despite intensive research for so many years, this disease is still not fully controlled. Yet it is clear that management, immunology and feed are important aspects to controlling coccidiosis.
By Wouter Steenhuisen, poultry consult, Boxmeer, the Netherlands*
The infective form of the coccidia is the oocyst (egg) which is shed with faeces of the infected bird. It is excreted by the chicken in an undifferentiated stage and will only become infective after sporulation. This occurs in the environment and is depending on temperature, humidity and oxygen. A susceptible chicken gets infected when it eats one or more sporulated oocysts from the environment. In practice it needs usually two or three cycles like that to get sufficient infection pressure to cause clinical problems. This will only occur if birds are kept in contact with the manure. In caged housing systems coccidiosis problems are rare.
There is hardly any farm without oocysts. These oocysts are easily spread all over the surroundings of the farm and can survive for a long time inside and outside poultry houses. They are very resistant to common disinfectants and to environmental extremes. Oocysts survive for weeks in soil, but survival in poultry litter is only a few days, due to ammonia and heat produced by composting. Live oocysts have been found in dust inside and outside poultry houses and on insects like darkling beetles ('tempex beetles').
Realising the complications as indicated above, what can be done practically to reduce the coccidiosis? First of all, it should be realised that coccidiosis cannot be eliminated from a farm, but in the best case be reduced. Construction of the house is very important in this respect. Only smooth concrete floors without cracks can be washed sufficiently to control the oocysts. On earth floors or concrete floors with wholes or cracks, this is practically impossible. Also avoid wooden or other rough materials in the poultry house which cannot be cleaned effectively. And try to clean the surroundings of the house, preferably have paved area around the house to enable cleaning outside.
The most important part of the cleaning process is the use of sufficient water to wash away most of the oocysts. Common disinfectants have little or no effect on oocysts. Ammonium Hydroxide has been reported as a highly effective disinfectant against oocysts. An old but effective system to control coccidiosis in an empty house is use of slated lime and ammonium sulphate: per 100 m2 floor surface 10 kg of Calcium Hydroxide (slated lime) and 20 kg of Ammonium Sulphate (fertiliser) is spread on the floor and approximately 100 litres of water is sprayed on top. This will produce a high level of ammonia, killing the oocysts. It also produces a gypsum, which will help to cover remaining oocysts in cracks in the floor. Use a proper gasmask when applying this system!
A few commercial disinfectants are also registered for use against coccidiosis, but these are only available in a limited number of countries so far. Increasing the down time of houses will only have a limited effect on coccidiosis, as oocysts can survive for weeks in the environment.
How to prevent introduction of coccidiosis in a house? After cleaning and disinfecting a house, the highest risk of introduction of oocysts is on boots and tyres. A classical foot dip is insufficient to prevent introduction of oocysts.
The recommended system is changing footwear at the entrance of the house, preventing contact between inside and outside used materials.
It is often believed that in a dry litter, less coccidiosis would occur. This is a misunderstanding. Research has shown that in wet litter sporulation is suboptimal due to the influence of ammonia and bacteria. In fact, dry litter shows better sporulation rates. However, increasing the humidity in litter as a control matter to reduce sporulation is not a practical solution as it will cause other problems like pododermatitis.
Coccidia have a live cycle of approximately 14 days in the intestine of the chicken and the immune system of the chicken will definitely detect these. Within a few hours after ingesting the oocyst, the host chicken begins to respond to the infection and by around four days this will lead to a protective immune response.
This response is specific to the strain of coccidia (eimeria) involved. The efficacy of the response depends on the amount of oocysts ingested and the state of the mucosal immune system. A healthy gut is well able to control low levels of infection. However, in case of disturbances in the intestine, like Dysbacteriosis/Bacterial enteritis, which is very common in broilers, the immune system might not be able to control coccidiosis efficiently.
So maintaining a good intestinal health is vital for a proper coccidiosis control. Complications like clostridiosis will have a direct effect on the coccidiosis infection.
Optimal gut health is obviously directly dependant on a good balanced and digestible feed. Such a balanced diet will reduce the risk of dysbacteriosis/bacterial enteritis problems and in that way indirectly reduce the risk of coccidiosis problems. A coarse grinded feed, so with larger particles (prior to pelleting/crumbling) will be better digested due to slower passage of the feed in the intestine. In that way, it will also help improving gut health and indirectly reducing coccidiosis risk.
It was found that lower coccidiosis lesion scores for E. acervulina occur when whole wheat is used in broiler diets, compared to fine wheat. This effect could not be demonstrated for E. tenella.
Besides texture of the feed, little is known about feed composition in relation to coccidiosis problems. Feed restriction has shown to improve the effect of E. tenella infection. However this is most probably again an indirect effect, as feed/light programmes in broilers can have a positive effect on gut health. Possibly, feed restriction also causes higher trypsin levels, which could help in reducing the replication of the coccidia.
Many alternative methods like homeopathy, phytopathy and aromatherapy have been used to control coccidiosis. But to the best of my knowledge, none of these therapies have been scientifically proven to be effective. The same holds true for probiotics, prebiotics and organic acids. In the best case, these products have an effect on the intestinal health and therefore indirectly on the immunity against coccidiosis, but no direct effect has been proven.
* References can be obtained from the author - www.poultryconsult.com firstname.lastname@example.org
[Source: World Poultry – Managing Coccidiosis, 2014]