Coccidiosis, a re-emerging issue for egg producers

Thereare nine Eimeria species that affect chickens, and five of these are associatedwith coccidiosis: necatrix, tenella, brunetti, maxima, acervulina. Coccidiosis vaccinesprovide layer pullets with a controlled dose of drug-susceptible strains of thefive important Eimeria species, which allow the birds to develop immunity to thecoccidia with minimal negative impact on the birds.

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Cage-free housing systems allow opportunities for hens to exhibit foraging behavior, but this also means more access to feces and the potential for coccidiosis issues.
Cage-free housing systems allow opportunities for hens to exhibit foraging behavior, but this also means more access to feces and the potential for coccidiosis issues.

There are nine Eimeria species that affect chickens, and five of these are associated with coccidiosis: necatrix, tenella, brunetti, maxima, and acervulina. Coccidiosis vaccines provide layer pullets with a controlled dose of drug-susceptible strains of the five important Eimeria species, which allow the birds to develop immunity to the coccidia with minimal negative impact on the birds.

The increased number of birds housed in alternative systems, where they are exposed to feces, has made coccidiosis more challenging to control. Resistance of coccidia populations in poultry houses to chemical coccidiostats and ionophores continues to be a growing problem with no new drugs introduced in the past few decades. In addition to providing the chance for birds to develop resistance, coccidiosis re-establishes populations of susceptible strains of coccidia on pullet and layer farms.

Coccidiosis vaccination for layers

Layers and breeders are considered to be long-lived birds, and developing immunity against tenella and necatrix is very important for these birds, according to Dr. Kelli H. Jones, technical services manager, Ceva Animal Health. She told the audience at the Midwest Poultry Federation Convention's Egg Production Workshop that tenella and necatrix are the two hardest Eimeria species for chickens to develop immunity for, because they are less prolific than the other three.

Each species of Eimeria has a different part of the gut in which it favors living. Necatrix, which is found in the lower gastrointestinal tract, tends to break in birds after six weeks of age. Jones said that with necatrix breaks, you will see blood and bird mortality. With tenella breaks, she said that you will also see mortality and bloody ceca. The life cycle for Eimeria in chickens takes around a week, and because necatrix isn't as prolific as other Eimeria, it can take four cycles for a flock to develop immunity to necatrix.

Jones said that in order to develop good immunity from a coccidiosis vaccination, "You want uniform day of age vaccination; you don't want to blast them with lots of oocysts. After the first 14 days, you will probably have developed 85 percent of the immunity that you will develop. Vaccination allows you to give a controlled low dose when you want to give it. By controlling the amount and timing of exposure with non-wild strains, the bird has the best chance to develop immunity with a minimum of negative impact."

Vaccination will cause some irritation to the gut of the bird, Jones stated. "You want to give enough oocysts to give immunity, but you don't want more reaction than is needed. You want a cellular immune response, which you get with a low level of infection."

Vaccination: On-farm or at the hatchery

Spray systems have been developed for vaccinating chicks at the hatchery. Initial systems sprayed liquid vaccine on the chicks which the birds would preen off each other's feathers, but systems have been developed to spray gel droplets which do not chill the birds by wetting their down.

Jones said the oocysts need heat, moisture and oxygen to activate and that these conditions can be found in the gizzard of the bird. Many egg producers have the perception that on-farm vaccination is better for chicks because it gives them time to recover from hatchery stress prior to the vaccination, Jones reported. She said on-farm vaccination may actually be better if the time between hatch and chick placement is greater than 20 hours, because after on-farm vaccination, the chicks have immediate access to feed and water. Feed and water in the gizzard trigger grinding action and enzyme release which break down the protective wall of the oocysts and activate them so they can infect the bird.

Access to litter

Chicks need access to feces in order to recycle the oocysts and develop immunity. For birds that are raised on the floor or who have access to litter, the ideal moisture level in the litter is 25-35 percent to get sporulation of the oocysts. Jones recommended keeping birds at 0.5 square feet per bird through 7-10 days post vaccination, and at 0.75-1.0 square feet per bird through 14 days to maintain the proper litter moisture levels. She said fencing is a good way to create these higher-density zones within the pullet house.

The litter should not get too wet, according to Jones. Too much moisture and high levels of ammonia are detrimental to cycling of the oocysts. Jones said to avoid tilling the litter. To keep the litter from getting too dry, Jones said the relative humidity of the air in the house should be between 35 and 40 percent.

When using a coccidiosis vaccine, Jones said to avoid using products that have anticoccidial properties or are antagonistic, like tetracyclines, sulphonomides and essential oils, for the first three weeks after vaccination. Jones also said vaccination works best if the flock can avoid other stressors like temperature fluctuations or being out of feed or water.

Another stressor to factor into the timing of your coccidiosis vaccination program is beak trimming. Jones suggested trimming when the birds are 9-10 days old - rather than 7 days, when the first cycling of oocysts occurs - in order to avoid trimming during critical oocyst uptake times.

Cage-reared birds

Pullets and layers that are raised in cages have less access to feces during their lives, and this reduces the coccidial challenge that the birds will likely be exposed to during their lives, but it means steps must be taken to ensure they are exposed to enough oocysts early in their lives to develop immunity. Jones reported on research that showed that having 40 percent of cage floor covered with dissolvable fiber trays for five weeks was found to be a highly effective means of exposing vaccinated pullets to enough oocysts to allow them to develop immunity. She said thick dissolvable paper and paper plates also have proven effective in studies. At minimum, the birds need 23-24 days of continuous paper in cages to ensure they have enough exposure.

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