Prevention of coccidiosis in chickens with live vaccines means suspending the use of anticoccidials, but a reduction in other antibiotics has also been observed. Reduction in antibiotic use in animal production is currently one of the aims of the poultry industry. Antimicrobial resistance has become a global public health problem in humans and livestock and plans to reduce the use of antibiotics are being implemented by the authorities in most countries.
Obviously, chemicals and ionophores used to control coccidiosis should be considered as antibiotics because the parasites that are intended to be controlled with these products can develop resistance with prolonged use of these substances.
The fight against coccidiosis in chickens means the adoption of different strategies depending of the type of bird. If we are managing long life cycle birds, we have to pay special attention to clinical Eimeria species that are able to generate a real coccidiosis process with macroscopic lesions and symptoms that will reduce the healthy status of the birds and will compromise the development of immunity against other diseases or cause the death of the birds.
However, when we are rearing standard, certified or even free-range broilers, the focus needs to be a different one. In these cases it will be difficult to find real clinical coccidiosis. Otherwise, the “silent” species – such as Eimeria praecox among others – will affect the intestinal mucosa and will reduce the capacity of a broiler for nutrient absorption. Dealing with subclinical species is essential in coccidiosis in chickens with a high growth rate.
Within the scope of assessing new strategies for the control of coccidiosis in poultry, the first factors to consider are always immunological and physiological but also include less objective factors such as the management. However, when these new strategies come to be assessed, the exercise has to be carried out in perspective by evaluating those indicators that are the most critical in order to decide whether maintaining such strategies or to replacing them with others. In the production of broiler chickens, these indicators are solely productive.
Live precocious attenuated vaccines for coccidiosis in poultry like HIPRACOX® have been used in numerous countries and situations, and these experiences serve to support the implementation of vaccine rotation programmes for the control of coccidiosis in poultry.
EVALON® is a live coccidiosis vaccine against avian coccidiosis in poultry composed of E. acervulina, E. brunetti, E. maxima, E. necatrix and E. tenella. All the strains have been selected to maximize immunogenicity. Avian Eimeria have a complex life cycle with a combination of exogenous and endogenous stages that trigger the immune system of the host. However, Eimeria parasites have also been described as being highly elusive to the immune system as well as producing chemokines than can slow or inhibit the immune response (Jang 2011,Schmid 2014, Miska 2013).
Although it is well known that live vaccines can induce an adequate immunity, we strongly believe that immune modulation is crucial in providing a strong, fast and long-lasting immunity (Dalloul 2005). This could be essential in the prevention of coccidiosis in poultry.
The cellular and molecular mechanisms leading to immune protection against coccidiosis in chickens are complex and include multiple aspects of innate and adaptive immunity. Innate immunity is mediated by subpopulations of immune cells that recognize pathogen-associated molecular patterns. Adaptive immunity, which is important in conferring protection against secondary infections, involves subtypes of T and B lymphocytes that mediate antigen specific immune response. Experimental studies in coccidiosis in chickens now support the role of lymphocytes and their secreted products (Lillehoj et al. 2011)
Eimeria parasites have a long and complex biological cycle with exogenous and endogenous phases that trigger the immune system of the host. These parasites that cause coccidiosis in chickens can produce substances (chemokines) than can inhibit the immune response.
From the very beginnings of this type of animal production, control of digestive diseases in the poultry industry has been one of the most significant health challenges. Moreover, among digestive diseases, coccidiosis in poultry continues to pose a challenge for the poultry farming worldwide. The incorporation of new tools provides new resources for safe and effective control.
Where are we coming from?
The housing conditions of birds used in production constitute a trigger factor for digestive diseases, with coccidiosis in poultry being one of the most prevalent, caused by parasites of the Eimeria genus.
When we think about the prevention of coccidiosis in chickens raised for a long cycle (breeders and layers) we cannot imagine any treatment other than vaccines. Apart from cost considerations, the use of coccidiostats has been always a handicap in birds that usually have restrictions on feed consumption. This is the reason why the protection conferred by a vaccine applied in the first days of life should be high enough to give a level of immunity that is able to protect them throughout the cycle.
Lesion scores of mid-intestine at 6 days post-challenge with E. necatrix. Lesion scoring grading 0-4 according to Johnson and Reid, 1970. Control vs EVALON® + HIPRAMUNE®T.
Layers and breeders have a production cycle of not less than 60 weeks in most cases. One of the main characteristics of these birds is that the rearing period in a normal poultry house is different to that in a production house.
In the world of livestock farming and animal protein production, the poultry industry has always been the sector with the greatest focus on achieving maximum control and information when it comes to the management of the production process and of the system for monitoring the medicinal products used in this process. HIPRA is going one step further along this path by offering a new vaccination concept, Smart vaccination, designed to provide improved vaccination monitoring and traceability for the prevention of coccidiosis in poultry.
From the early days of animal production, poultry farming has been in the vanguard of technology, feeding systems, farm automation, etc. Poultry production is one of the most advanced and streamlined of all the animal production sectors, guaranteeing all the quality standards demanded by the consumer in each market. A paradox exists, however: the processes associated with vaccination, unlike other parameters such as feeding, environmental conditions, etc., are beyond control.
Coccidiosis in poultry is one of the diseases that probably cause most damage in the broiler rearing industry. It is not a case of producing high mortality within flocks but a subclinical process affecting economic performance, greater use of antibiotics and a loss of environmental farm conditions that will probably affect animal welfare.
E. praecox in the duodenum: A type of coccidiosis that is not clinical but causes a decrease in growth and feed conversion.
Coccidiosis in poultry has become a truly complex disease that is not only an intestinal disease but also involves other issues that affect global production. In the past, coccidiosis was diagnosed as a clinical disease –even by the farmers- with coccidiosis caused by Eimeria tenella being the most simple example of this disease.
Coccidiosis in chickens is one of the more common and widespread diseases. Since the beginning of the industrial production of broilers, veterinarians and farmers have been trying to control this costly parasite.
The annual cost is believed to be around $1.5 billion/year. The cost of coccidiosis in chickens is based on direct production losses and indirect costs through the application of control measures.
In the past, the fight against the different Eimeria species was through the use of several molecules in the food. The first chemicals used against coccidiosis in chickens were introduced in the 1950’s. It soon became clear that there were some efficacy problems with these molecules, in the sense that the Eimeria spp. present on the farms could develop resistance against them after they were used consecutively a couple of times on the same farm.