Coccidiosis is a parasitic disease that requires continued exposure to the Eimeria vaccine oocysts (a stage in the coccidia life cycle) to establish long-term protection. Dr. Linnea Newman, global poultry technical service director, Merck Animal Health, says the most common misunderstanding when starting a layer pullet coccidiosis vaccination program is an expectation of fast immunity.
“Most viral and bacterial disease vaccines are very successful in initiating an immune response within three to seven days after being properly administered. However, coccidiosis vaccination requires up to four to five weeks of oocyst cycling to stimulate immunity,” said Newman.
Consequently, to successfully immunize the flock, ongoing management practices in the pullet house require careful attention to relative humidity, proper management of litter and/or cage paper to allow cycling of vaccine oocysts and monitoring of oocyst counts.
The initial vaccination administers a controlled number of live sporulated oocysts which stimulate a primarily cellular immune response in the intestinal tract. These oocysts continue reproducing in the gut and eventually are shed in the feces. It’s important for pullets to have access to the feces where oocysts sporulate to continue the immunization process. As birds ingest oocysts, the coccidia reproductive life cycle begins anew and the bird responds with an even higher level of immunity.
The Eimeria reproductive life cycle takes four to seven days and chickens require two to five cycles to develop needed immunity (both time periods vary by coccidia species). Consequently, a successful immunization requires proper initial vaccination as well as continued consumption of oocysts for up to five weeks. After that time, the flock should be able to resist a coccidiosis challenge, assuming an ongoing exposure to oocysts remains through the production period.
Vaccination process starts in the hatchery
Most layer pullets are vaccinated in the hatchery by spray. The vaccine is generally ingested as chicks respond to the colored vaccine solution by preening themselves.
When using coarse spray administration, vaccine management is extremely important to ensure oocysts are constantly agitated to prevent settling in the bottom of the diluent container. Another spray delivery method utilizes a gel solution. It’s important to mix the gel and vaccine thoroughly so the oocysts remain in suspension.
Accurate calibration of the spray equipment is required to ensure proper coverage of all the chicks. Birds not initially vaccinated have a later start in the immunization process and there is a risk of a greater reaction or infection from wild strains.
Good lighting is required so that chicks are able to see the colored vaccine diluent solution or gel to continue preening. Some hatcheries strive to provide 93-foot candles of light for at least six minutes after vaccination. It is also important that the holding area temperature is maintained at comfortable temperatures to prevent chilling and loss of body temperature. Close observation of the chicks will reveal when preening has been finished.
Environment in the pullet house
Three requirements for coccidia oocyst reproduction on the farm are humidity, heat and oxygen. Proper chick brooding practices provide the needed heat and oxygen. Relative humidity should be maintained in the 50 to 60 percent range for the first five weeks of age.
Lower humidity can delay or stop the oocyst cycling process before adequate immunity is established. Humidity is usually controlled by ventilation. If the house is too dry, producers might spray water on the walls or concrete walkways between cages to increase humidity or if the house is equipped, briefly run cooling foggers each week on a day of anticipated peak oocyst cycling.
Management of floor-raised birds
Bird density is a key to successful immunization of flocks raised on the floor. Controlling the density helps regulate the rate of ingestion of oocysts – too many oocysts can cause intestinal damage, while too few available oocysts can result in delayed or inadequate immunity.
Also, bird density needs to be monitored to ensure there is not too much competition for feed and water which affects pullet uniformity.
Litter management is important to maintain the proper environment for oocysts to reproduce.
Ideal litter conditions include a temperature of 82 to 85⁰ Fahrenheit and a moisture level of 25 to 35 percent. Monitor and adjust ventilation settings to help maintain proper litter humidity. Extremely high litter moisture levels result in too many oocysts reproducing which can cause clinical disease. Use litter that will absorb moisture such as wood shavings or rice hulls. Avoid turning the litter over during the first four to five weeks while the vaccine is cycling. Ensure all watering equipment is in good working order and not leaking.
Starting Pullets in Cages
Heavy, waxed cage paper, pressed fiber flats or even the rough bottoms of paper plates are used on cage floors to collect manure and allow chicks’ access to oocysts for the cycling process.
At least 40 percent of available floor space should be covered by the paper. Producers should use paper products that will remain viable for 21 to 28 days. During the first week feed should be spread on the paper to encourage picking at the feed and feces to ensure oocyst consumption.
After initial brooding, pullets are often moved to different tiers to allow them adequate space. Try to move birds to a lower tier as their exposure level will be more consistent with birds above them.
Paper materials should be divided and moved with chicks to the new cages to continue the cycling process. In aviary systems, papers should be moved to the floor when pullets are allowed floor access.
Measuring immune response is an important part of all vaccination programs. For coccidiosis vaccines, submitting fecal samples to a laboratory for oocyst counts is used to evaluate adequate immune response.
Laboratories provide results as a total of species combined expressed as OPG (oocysts per gram) of fecal material. Dr. Kelli Jones, CEVA Manager Technical Services, states “OPG counts are the best tool as they tell the story of what’s happening in the pullet house. Use this tool to monitor the immunization process and fine tune your program.”
There are two schools of thought on frequency of sampling. Some feel that samples taken at days seven, 14, 21 and 28 (at times extending to include a 35-day count) correlate well with peak oocyst cycling times. Others recommend sampling every three days starting at day seven and continuing until day 37 for routine monitoring (or up to day 42 when first establishing a coccidiosis vaccination program).
Initial counts often are relatively low, especially in caged pullets. More frequent, longer sampling provides a more detailed picture of cycling (often smaller increases are noted as different species cycle at different time points).
Some coccidia species require three or four cycles to establish immunity, so depending on the species included in the vaccine and the house environment, variation is expected. Vaccine titer and efficacy of vaccine administration also affect oocyst counts.
If initial oocyst counts are higher than expected due to excessive cycling, watch closely for signs of a coccidiosis break when treatment with a full dose of amprolium may be indicated to maintain flock health. If inconsistent cycling is noted from sampling results and/or some birds show mild symptoms of clinical disease, a less aggressive treatment program can be used for that specific flock. It is recommended to use amprolium at ¼ dose to reduce the disease incidence. This low dose allows natural exposure to oocysts to “trickle” through and birds can build up natural immunity.
Other factors to consider
Pullet managers should be mindful to avoid stressing chicks at days six to eight, 13 to 15 and 20 to 22 when oocyst cycling peaks. If birds are beak trimmed or moved in the pullet house, these periods should be avoided as oocyst ingestion might temporarily decline. Likewise, avoid known stressful vaccinations which affect bird activity.
Use of products that have some anti-coccidial effect should be avoided during the first three to five weeks of rearing. Reduced immunity and outbreaks later in life could result from treatment with products which might interfere with the cycling process such as coccidiostats, tetracyclines, sulfas or essential oils, such as oregano.
Careful attention to management details will ensure successful coccidiosis immunization and avoid costly outbreaks during egg production.