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Schering-Plough's tech service team answers questions about managing coccidiosis in broilers

A. Based on a recent survey of 33 isolates of Eimeria maxima collected from 11 states and 18 major poultry integrators throughout the US, only three of the isolates (less than 10%) showed only partial protection by the Coccivac strain of E. maxima. In other words, the prevalence of E. maxima among US poultry integrators that is highly variant to the E. maxima in Coccivac is very low and is not of major significance at this time.

The results of the study also indicate that if birds are properly immunized, the vaccine strain of E. maxima in Coccivac-B would protect against a wide range of field isolates encountered in commercial operations in the US.

Q. IS THERE ANY MERIT TO USING AN AUTOGENOUS VACCINE FOR VARIANT SPECIES OF EIMERIA?

A. Autogenous vaccines are derived from uncharacterized Eimeria field species. These poorly defined species are not subjected to the same rigorous testing as the licensed, defined species of Coccivac. To develop a safe, consistent vaccine, it is imperative that the basic species characteristics such as pathogenicity, antigenicity and anticoccidial drug sensitivity are well defined. Using a poorly defined vaccine highly increases the risk of rapidly spreading unwanted contaminates from a few selected farms to all company farms, which could be an overnight disaster and a very expensive problem to control later; it also decreases the chances of maximizing production performance due to inconsistent product manufacturing from serial to serial.

Q. ARE YOU RE-ISOLATING THE VACCINE STRAINS FOLLOWING THE USE OF COCCIVAC?

A. Yes. All research to date supports our initial hypothesis that the vaccine strains over 2 to 3 flocks are displacing wild field strains. This is evident by the Eimeria population shift toward more sensitive strains as measured via anticoccidial sensitivity testing (AST).

Q. HOW STABLE IS THE POPULATION SHIFT TO EIMERIA STRAINS CONTAINED IN THE VACCINE?

A. It is not a permanent change - it's a shift. The vaccine strains become predominant in the absence of drug pressure. With drug pressure and time, the strains will shift back to those that are drug tolerant/resistant.

Q. HOW MANY CYCLES OF COCCIVAC USE DOES IT TAKE BEFORE NOTICING A CHANGE IN THE EIMERIA POPULATION?

A. It's difficult to say specifically how many, but the longer the removal of pressure from the drugs, the greater the chance of seeing a change in the Eimeria population. We can say, however, that there should be a minimum of two cycles and that three cycles are preferred.

Q. WHAT ABOUT COMPETITION BETWEEN THE WILD AND VACCINE STRAINS OF EIMERIA? WILL A SHORT LAYOUT TIME INFLUENCE THE OUTCOME?

A. Layout time will influence the desiccation rate of Eimeria. Coccidia will not be eliminated, but the longer the layout period, the greater the reduction in numbers.

The advantage of vaccination is that birds are exposed early in life to vaccine strains; eventually, they will develop immunity. Using a live vaccine allows us to control the dose (level of exposure) as well as the timing (day-1) of exposure. These are two major advantages in controlling any disease process.

Q. DO COCCIDIOSIS VACCINES REQUIRE SPECIAL HANDLING?

A. Yes. Make sure the vaccines are never frozen, which will kill or damage sporulated oocysts and ruin their effectiveness.

If ice crystals are noticed in the liquid, the vaccine should be discarded. Store Coccivac vaccines at a temperature between 36°F to 47°F (2°C and 8°C). The vaccines should be kept at these temperatures during shipping as well as during transport to farms or hatcheries. When the vaccines are refrigerated, watch for uneven temperatures that might allow partial freezing.

Q. ARE COCCIVAC VACCINES TESTED FOR POTENCY?

A. Yes. Potency testing in live birds is conducted on every serial (batch) of Coccivac manufactured. Birds are vaccinated with the serial being tested and are then challenged with every species of Eimeria contained in the vaccine to make sure they develop immunity. If they have developed immunity, they do not develop coccidiosis. The validity of each potency test is checked by challenging unvaccinated birds.

Q. DOES THE METHOD OF VACCINATION AFFECT THE AGE WHEN CHICKS CAN BE VACCINATED WITH COCCIVAC?

A. Yes. When the Spraycox spray cabinet is used, chicks can be vaccinated in the hatchery because the sprayer enables uniform distribution; 21 ml of coarse spray is delivered for each box of 100 chicks. Chicks "preen" to clean and dry their feathers and ingest the vaccine. Red dye mixed in with the vaccine gets their attention and stimulates preening.

An alternative to using the Spraycox applicator is feed spray application. It does not deliver the vaccine as uniformly as the Spraycox applicator, but can be used when hatchery application is not possible. Chicks must be 4 days of age, however, since younger chicks may not have developed uniform feed consumption patterns.

Q. WHAT'S THE DUAL-NOZZLE SPRAYCOX CABINET?

A. It enables simultaneous administration of Coccivac-B and Newcastle/ Bronchitis (ND/IB) vaccines, which in turn provides producers with convenience and reduced labor costs. The nozzle for Coccivac delivers the coccidiosis vaccine as droplets that are ingested by preening. The nozzle for ND/IB produces a flat, even spray across the box.

Q. HOW DOES STOCKING DENSITY AFFECT COCCIVAC VACCINATION?

A. You'll get more uniform results if the initial stocking density is 0.75 ft2 to 1.0 ft2 per bird. Higher stocking density could result in excessive litter moisture and a high litter oocyst density.

After vaccination, third-house and half-house brooding encourages proper Coccivac cycling for the first 7 to 14 days. Remember that for full immunity to develop, birds require not only the initial "dose" of live sporulated oocysts administered via the vaccine, but two or more life cycles of coccidia.

Q. WHAT'S THE BEST LITTER MOISTURE CONTENT FOR BIRDS THAT RECEIVE COCCIVAC?

A. A minimum litter moisture content of about 25% is needed to stimulate the coccidial life cycle, but too much moisture will lead to poor Coccivac results. If the litter is too wet, coccidial cycling may be heavy, causing too much reaction in birds and even overgrowth of the bacteria that causes necrotic enteritis. Too much litter moisture also can lead to transient immunosuppression due to "cold stress" as well as high ammonia, resulting in blindness and poor flock uniformity.

Q. WHAT TIPS DO YOU HAVE FOR GOOD MANAGEMENT OF LITTER MOISTURE?

A. One way to reduce litter moisture is by properly maintaining nipple drinkers, which reduce the amount of water spilled into the litter. Consider your ration formulation. Some rations reduce the amount of excreted moisture. Litter type and depth should accommodate the amount of moisture expected in the house. Ventilation also can be adjusted to control litter moisture. Bird density needs to be controlled to avoid the moisture concentration.

For more information on managing litter moisture, see the article by Mike Czarick on page 12.

Source: CocciForum Issue No.7, Schering-Plough Animal Health.

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