Avian coccidiosis is a parasitic disease caused by protozoa of the genus Eimeria spp. These parasites multiply in the intestine, damaging the tissue and causing poor absorption of nutrients, diarrhea of ​​varying severity, possible dehydration, and death. This disease has a great economic impact worldwide, due to its effect on the growth and mortality of chickens, and the costs of the prevention and control of coccidiosis. (more information about the disease here)

There are seven species of coccidia that can colonize the intestinal tract of chickens (Gallus domesticus): E. acervulina, E. maxima, E. tenella, E. mitis, E. necatrix, E. praecox, and E. brunetti. Eimeria tenella is the species with the highest prevalence in Asia (Chengat et al., 2017; Huang et al., 2017). Most of the animals are parasitized by more than one species of Eimeria simultaneously, with Eimeria necatrix being the most frequent species in mixed infections (Huang et al., 2017). In addition, the lesions produced by this parasite are the gateway for other infectious processes, such as necrotic enteritis.

The transmission of this coccidia within the facility or even between farms is carried out in a feco-oral way, or through vectors, whether they are contaminated materials, or by live vectors, such as rodents, worms, flies or beetles (Belli et al., 2006).

Alphitobius diaperinus, also known as darkling beetle, has a worldwide distribution and constitutes one of the main pests that affect the poultry industry. The growth of this beetle is favoured by the environmental conditions (high temperatures and relative humidity, wet litter, presence of faeces) present in intensive poultry farming, as well as the ability to resist the usual disinfectants. Its economic impact is due to the effects on the facilities and their isolation, as well as its role as a vector of multiple pathogens, such as Eimeria, Marek’s disease virus, bacteria such as E. coli, Salmonella or Staphyloccocus spp., and even fungi like Aspergillus spp.

Conventional anticoccidial program

Prevention and control of coccidiosis has usually been done by the combination of different tools, including the correct application of a biosecurity plan, cleaning and disinfection of the facilities, together with the use of anticoccidial drugs.

Coccidiostatic drugs are used continuously in preventive programs to prevent the reproduction of the coccidia and the appearance of symptoms. Although, coccidiostats do not cause the death of the parasite and they allow the development of a certain immunity of the animal against the agent.

They differ according to their origin and mode of action into synthetic coccidiostats, such as nicarbazin, or ionophore coccidiostats, such as monensin or maduramycin, obtained from the fermentation of different strains of Streptomyces spp. or Actinomadura spp.

Challenges in the conventional anticoccidial program

The continued and abusive use of these products has favoured the appearance of resistances, which has been described in all continents. The long-time exposure to these products, as well as the high reproductive potential of coccidia, increase the likelihood of resistant mutant strains to be selected and survive.

In Asia, in order to minimize the risk of resistance to coccidiostats, it is common to carry out rotation or shuttle programs, in which different synthetic coccidiostats and ionophores are used in each production cycle or even within the same cycle. Ionophores are widely used in Asia and are sometimes combined with synthetic anticoccidials in rotation programs. Despite this, these strategies are not a complete guarantee to avoid the appearance of resistances, and there is the possibility of cross-resistance between similar drugs.

In addition, the growing pressure to reduce and even ban the continued use of drugs in animals intended for human consumption, clears the need to work with alternatives that allow the control of coccidiosis while achieving the desired productive and economic parameters.  achieve the desired product and economic rates.

New methods for the prevention and control of coccidiosis

There are new methods for the prevention and control of coccidiosis, which replace the use of coccidiostats on a continuous basis. These new strategies are based on the immunological control of coccidiosis, like vaccination or natural solutions, such as pronutrients.

• Vaccination

Vaccination seeks to stimulate immunity against Eimeria spp. by administering oocysts and re-exposure of the animals to the oocysts present in the litter. Three types of vaccines have been developed: live attenuated vaccines, live non-attenuated vaccines, and subunit vaccines.

Live vaccines are based on the selection of strains of coccidia that can cause the disease, which have a shorter life cycle and a lower reproduction rate. In this way, these strains can retain their immunogenic capacity without causing severe infections. This type of vaccine is the one used in Europe.

Non-attenuated vaccines contain unmodified strains, although they contain a low number of oocysts of the most pathogenic species, which allow the induction of protective immunity. These vaccines are widely used in North America, South America, Asia, and Australia. Due to their price, vaccination in Asia is more widespread in breeders than in broilers. Animals are usually vaccinated on day 1 of life, with a repetition usually at 7 days of life.

However, the limitations of vaccination should be considered:

• The Eimeria species included in the vaccine may not match the species present on the farm. As there is no cross-immunity between species, the administration of the vaccine does not guarantee a complete protection against the disease.
• In the case of vaccination with non-attenuated strains, it should be noted that:
  • The necessary reinfection cycles to generate a good immunity may fail, either due to an excessive reduction in oocysts production, or due to a reduced sporulation. These facts may be linked with inadequate environmental conditions, low density of animals or the production in cage systems.
  • It can cause a growth retardation in broilers that may not be compensated before slaughter.

The vaccines made up of Eimeria antigenic subunits are based on the acquisition of maternal immunity. These vaccines are applied to hens prior to the start of the laying phase, and they generate protection for the first 7-10 days of the animal’s life. Then, it must be the immune system itself that fights against the disease. This system works when broilers ingest a low number of oocysts, as their immune system is still immature and can be overwhelmed if faces a high challenge.

Therefore, this prophylaxis can work in farms with good health status, with little history of coccidiosis and strict cleaning measures, which is practically non-existent in commercial production.

• Natural solutions: Pronutrients

The natural solutions, used as dietary supplements, aim to improve the innate defense mechanism of the animal to reduce or eliminate the use of drugs against coccidiosis.

Intestinal optimizer pronutrients are compounds of plant origin with proven efficacy. Pronutrients have a metagenetic mechanism of action. Intestinal optimizer pronutrients enhance the local immunity of the intestine, since they stimulate the expression of interleukins (IL-1, IL-12, IL-18) by intestinal polymorphonuclear cells (PMNs).

Interleukins are proteins that act as chemical mediators in the cellular immune response, and attract defense cells to the affected area. For this reason, they play a fundamental role in the response to coccidiosis and in the prevention of symptoms.

In addition, their advantage lies in the fact that intestinal optimizer pronutrients are natural substances that do not have a pharmacological effect, since they stimulate the intestinal physiology of the animal, so they do not generate resistances, and they do not need a withdrawal period, because no residues are left in tissues.

Products based on intestinal optimizer pronutrients offer a great versatility to be included in the anticoccidial plan of farms, since they allow to replace coccidiostats totally or partially (shuttle or rotation programs), and can complement vaccination.

To demonstrate the efficacy of the intestinal optimizing pronutrients, the following are the results obtained commercially between two batches (Table 1) that received:

• Group 1- Pronutrients:
  • Day 0-22: narasin + nicarbazine (0.5 kg / t)
  • Day 23-slaughter: intestinal optimizer pronutrients (0.5 kg / t)
• Group 2 – Monensin:
  • Day 0-22: narasin + nicarbazine (0.5 kg / t)
  • Day 23-29: monensin (0.5 kg / t)
  • Day 30-slaughter: intestinal optimizer pronutrients (0.5 kg / t)

As shown in table 1, the group with pronutrients obtained a better performance, which corroborates that pronutrients are a safe bet to replace coccidiostats like monensin.

Conclusions

Coccidiosis is a disease of worldwide distribution, favoured by intensive poultry production. Traditionally, the prevention and control of coccidiosis has been based on chemoprophylaxis. The continued and abusive use of anticoccidial drugs has generated the appearance of resistances to these products.

The emergence of resistances, together with the global trend towards the reduction and prohibition of the use of drugs for disease prevention in animals for human consumption, has motivated the search of new strategies to control the disease.

The new methods for the prevention and control of coccidiosis are based on the immunological control of coccidiosis. Intestinal optimizer pronutrients are a natural tool to stimulate the local immune response of the gut against coccidiosis. This natural solution does not generate resistance and has great versatility, since they can be applied by replacing coccidiostats in shuttle or rotation programs and as support for vaccination. Furthermore, these products do not leave residues on meat nor eggs, so they can be used in organic production.

However, it should be noted that the management, environmental and biosecurity measures must complement the techniques described above to ensure a correct control of the disease.

Intestinal optimizer pronutrients, manufactured by Biovet S.A., are marketed under the name Alquernat Zycox, available in liquid form for drinking water and powder premix to mix with feed, for conventional and organic production.

Alquernat Zycox is the only product indicated for the prevention and control of coccidiosis with a patented technology, developed by Biovet S.A., whose mechanism of action and positive effect on immunity and productivity has been demonstrated in multiple in vivo and in vitro trials.