Aiming for optimal turkey coccidiosis vaccination

Spray administration of coccidiosis vaccines used in chicken and turkey production enables the vaccine Eimeria oocysts to enter the anterior digestive tract. Photo: Henk Riswick

Consumer preference for antibiotic-free animal products has increased interest in vaccination. Coccidiosis vaccination has become more common in recent years, especially in antibiotic-free or ‘no antibiotics ever’ production facilities. The turkey industry has a limited number of anticoccidials compared to the chicken industry. Vaccination is a wise strategy to maintain the efficacy of existing anticoccidials, combat coccidiosis and support drug sensitivity.

The Coccidiosis-causing Eimeria protozoa species are ubiquitous in commercial turkey production and are very difficult to eradicate from a barn due to their prolific nature and resistance to commonly-used disinfectants.

Coccidiosis is a disease of significant economic proportions in turkeys. The economic losses due to coccidiosis are attributable not only to the mortalities but also production losses associated with reduced weight gain, poor feed conversion rate, poor uniformity and the cost of prophylactic and therapeutic medications.

Coccidiosis compromises intestinal integrity and impairs the normal digestion mechanism by making it vulnerable to various intestinal pathogens, as well as providing a niche for opportunistic pathogens. Apart from compromising intestinal health, it affects bird welfare. Improving gut health by stabilising intestinal microbiota is a key factor in raising healthy turkeys.

Poults are not passively immunised against coccidiosis through maternal antibodies from the hens, so they are highly susceptible to coccidiosis infection early on in life. Uncontrolled exposure to virulent Eimeria field strains at a young age adversely affects intestinal health, compromises intestinal integrity and sets the stage for subclinical/clinical coccidiosis. In addition, it provides an optimum niche for secondary bacterial infections. Naïve turkeys, at any age, exposed to virulent wild-type Eimeria strains are highly susceptible to coccidiosis.

Current disease management

The pathogenic ability of Eimeria field strains to infect naïve turkeys requires control measures starting from the day of placement. Coccidiosis is controlled and managed by chemicals, ionophores, phytochemicals and vaccines. Various coccidiosis control programmes are followed and adapted worldwide based on necessity, economics and adaptability.

Rotation programmes are followed to mitigate coccidiosis in which different anticoccidials are rotated between the flocks depending on the seasons. Including coccidiosis vaccination as part of the rotation programme helps to reduce anticoccidial-resistant strains in the field. Shuttle programmes are applied to control coccidiosis in which different anticoccidials are used at different turkey growth stages.

In bio-shuttle programmes, hatchery vaccine administration is followed by an in-feed anticoccidial, starting at about 14-28 days of age. Bio-shuttle programmes are followed to reduce the peak cycling of Eimeria oocysts, as well as optimise production performance by balancing performance loss and feed conversion that may occur following the coccidiosis vaccination. Different programmes may be used for sustainable coccidiosis control and optimal flock performance.

Benefits of vaccination

Consumer concerns about antibiotic resistance has led to an increase in the production of antibiotic-free turkeys. According to the 2023 Turkey Industry Annual Report by Dr Clark and Dr Chiaia, coccidiosis ranks 13 among the issues facing US turkey production facilities and reflects a growing trend towards ‘No antibiotics ever’ and ‘Raised without antibiotics’ programmes. Ionophores are considered antibiotics in the US and cannot be used in turkey production facilities claiming antibiotic-free status.

‘No antibiotics ever’ and ‘Raised without antibiotics’ programmes do not permit the use of ionophore anticoccidials. In addition, some programmes prohibit the use of FDA-approved chemical anticoccidials. In addition, in view of the prevalence of anticoccidial resistance, the use of coccidiosis vaccine in turkeys has drastically increased over the past few years.

Coccidiosis vaccination is a commonly-used approach to restore anticoccidial sensitivity in turkey flocks. Switching from the use of anticoccidial administration in feed to vaccination is often used to reduce drug resistance in Eimeria strains. With coccidiosis vaccination, poults are safely exposed to Eimeria vaccine strains in a controlled manner. Vaccinating the turkey flock with a commercial turkey coccidiosis vaccine helps to reseed barns with drug-sensitive Eimeria strains and replace drug-resistant strains, eventually restoring drug sensitivity.

Choice of vaccines

Vaccines are important to the turkey industry to protect against Eimeria and reduce drug-resistant strains. The vaccines should be chosen based on the field pressure. E. meleagrimitis, E. adenoeides and E. gallopavonis are considered highly pathogenic species in turkeys and are documented as predominant strains in the field. It is well known that there is generally little to no cross protection between different Eimeria species. Thus, choosing the right coccidiosis vaccine will offer complete protection against the predominant strains.

Few companies adapt autogenous turkey coccidiosis vaccines that are custom-made vaccines and flock specific. Autogenous vaccines are restricted to specific farms or complexes and their use is limited in commercial turkey operations. Both the virulence and drug sensitivity of autogenous vaccine candidates needs to be evaluated before inclusion in the vaccination programme. If the autogenous vaccine candidates are not properly evaluated, there is a high risk of drug-resistant strains spreading in the flock.

Autogenous vaccines are composed of different strains and dosages and the success rate is highly variable. Commercial turkey coccidiosis vaccines contain drug-sensitive Eimeria strains. Including coccidiosis vaccination in the rotation programme is a prudent strategy to minimise the risk of developing antibiotic resistance in Eimeria field strains. In the US commercial coccidiosis vaccines are approved by the USDA and thus considered safe and effective to use in commercial turkey operations.

Creating ideal conditions

Spray administration of coccidiosis vaccines enables the vaccine Eimeria oocysts to enter the anterior digestive tract. Consumption of the oocysts in subsequent cycles increases the host’s exposure to the parasite, resulting in a robust immune response in subsequent weeks. To enable the favourable oocysts to thrive, the moisture content of the litter should be between 25-35% for sporulation.

It is also important to make sure that the feed does not contain any anticoccidials. Although Eimeria species stimulate both cellular and humoral immune responses, the cellular immune response is predominant in offering protection against Eimeria species. Protection is provided only against the Eimeria species included in the vaccine and does not confer cross protection against other species. Thus, protective immunity is provided only against those Eimeria species incorporated in the vaccine. Vaccination does not offer protection immediately and it usually takes 3-4 weeks for robust immunity to build up.

Close monitoring

The success of coccidiosis vaccination in turkeys relies on the effective administration of the vaccines, followed by management practices that ensure proper cycling of the Eimeria oocysts in the barn. Counting the oocysts per gramme in faeces for a few weeks after vaccination may help in assessing the cycling of the Eimeria vaccine. A few birds can be randomly chosen from different locations in the barn and faeces can be collected by applying mild pressure to the abdomen and squeezing the vent region. Faeces can also be collected from the litter in different locations of the farm and analysed.

Oocysts per gramme analysis is a simple and effective method to monitor the cycling of Eimeria vaccine strains in turkeys. Choosing the right vaccine candidate based on field pressure and proper administration of the vaccine plays a key role in coccidiosis vaccination. Following the appropriate post-vaccination management measures with adequate litter, feed, bird density, ventilation and lighting helps in re-cycling the Eimeria oocysts from the vaccine and aids in the development of robust immunity.

A holistic approach is essential when choosing the right coccidiosis control programme and should include homogenous vaccine administration followed by appropriate post-vaccination management strategies to increase the success of coccidiosis vaccination.