Coccidiosis remains leading problem in caged pullets

Coccidiosis remains a leading health problem in caged pullets, according to a recent survey conducted by the Association of Veterinarians in Egg Production (AVEP).

In the survey, AVEP members were asked to rate 21 common diseases of pullets and 30 for layers, based on the prevalence and severity in their respective service areas. The rating scale ranged from one, indicating the condition wasn’t a problem, to four, meaning the disease was widespread.

For caged pullets, 19 respondents cited coccidiosis as the No. 1 health problem, with an average rating of 2.16. In the last survey, conducted in 2009 by AVEP, coccidiosis ranked third with a rating of 2.00, Dr. Eric Gingerich reported during the annual meeting of the US Animal Health Association, held last November In Minneapolis, Minnesota.

Coccidiosis was also cited by 10 respondents as the leading health problem in cage-free pullets; 13 respondents said it was the third-leading health problem in cage-free layers, following cannibalism and Escherichia coli infection, said Gingerich, technical service specialist with Diamond V, a manufacturer of nutritional fermentation products.

In caged pullets, coccidiosis continues to be a problem due to contamination of houses with coccidial oocysts from past outbreaks and delivery of the oocysts to chickens in cages by flies or beetles, he said.

In addition, vaccination to prevent coccidiosis in caged and cage-free pullets has “met with challenges of high mortality due to poor uniformity of vaccine application and litter moisture in cage-free housing,” Gingerich said.

POST-VACCINATION MANAGEMENT ‘KEY’

In an interview with Layer Health, Dr. Charlie Broussard, U.S. poultry technical service director for Intervet/Schering-Plough Animal Health, manufacturer of the live coccidiosis vaccine Coccivac-D, said, “I believe coccidiosis in vaccinated chicks has less to do with the initial vaccine application and that the problem is post-vaccination management that prevents proper coccidial recycling.”

Producers can achieve excellent vaccine uniformity with the newer, spray-on equipment, such as the SprayCox spray cabinet, which is available to hatcheries for use on day-old chicks.

“From then on, the key to good results with coccidiosis vaccination is management that facilitates the recycling of vaccinal coccidial oocysts. It’s repeated exposure that enables vaccinated birds to develop full immunity against coccidiosis,” he said.

“When we’ve investigated cases of problems in layers vaccinated against coccidiosis, we’ve found a lot of variability in recycling management,” he added.

ENHANCED OOCYST RECYCLING

Broussard cited a study conducted by Intervet/Schering-Plough Animal Health in which cage-reared pullets were vaccinated with Coccivac-D, which was administered by a hatchery spray cabinet at day 1. Next, cage floors were covered either with paper that lasted 2 weeks or fiber trays that lasted 5 weeks; the paper and trays were used to enhance oocyst recycling and provide repeated exposure to vaccine oocysts. Fecal oocyst counts demonstrated coccidial cycling after vaccination.

After a high-dose challenge with mixed coccidial species, pullets from high-tiered cages suffered from significant mortality, while birds from lowtiered cages — which could reach the “clean” returning manure belt when they got tall enough — were well-protected against coccidial challenge.

Under field conditions, however, the pullets from high-tiered cages had evidence of exposure, demonstrated by only moderate oocyst shedding, and they did not break with clinical signs. The four previous placements in this facility had experienced clinical coccidiosis and mortality. Pullets from the lower tiers did not even respond to exposure; no oocyst shedding was detected and protection was complete.

Birds that were reared with the fiber trays were better protected than birds that were on the paper, since the trays provided longer vaccine oocyst exposure, he said (Table 1).

The study results, which were presented at the 2010 American Association of Avian Pathologists annual symposium, indicate that whenever possible, pullets in lower-tiered cages should be transferred to lower-tiered cages, where the coccidial challenge is greatest, and pullets in higher-tiered cages should be transferred to higher-tiered cages, where the challenge is minimal, he said.

“Oocyst cycling in caged pullets can be challenging compared to cycling in broilers because there is little access to feces and conditions are dry, but the study demonstrated that with some added attention to management, these birds can develop solid immunity against coccidiosis,” he said.

In cage-free birds, factors such as stocking density and litter moisture must be considered to achieve the best results after coccidiosis vaccination.

For instance, high stocking density and high litter moisture can enhance coccidial recycling, but if overdone, it can cause too much recycling; conversely, low stocking density and low litter moisture may result in inadequate oocyst recycling and inadequate immunity. “It’s about finding the right balance,” Broussard said.

Table 1. Tier position and the recycling method significantly affected the results.