Poultry farming worldwide has made remarkable progress in the control of infectious diseases which affect poultry production. Among these diseases, there is a large number produced by infectious agents of all types. An important group is constituted by internal parasites, divided into different families, and affecting several organs and production stages.

These diseases cause a great economic impact on poultry farms due to treatment, control, loss of productivity, and mortality. For this reason, it is of great importance to establish strategies to control these infectious diseases.

Coccidiosis in poultry

Avian coccidiosis is a parasitic disease caused by protozoa of the genus Eimeria, phylum Apicomplexa, family Eimeriidae.

Eight different species of Eimeria of great importance in poultry production are recognized, among which the pathogenic capacity is variable. The most pathogenic species are E. tenella and E. necatrix. The species E. brunetti is rare but highly pathogenic. Those of moderate to mild pathogenicity are E. acervulina, E. maxima, and E. mivati. Finally, E. mitis and E. praecox are of very mild or rare pathogenicity.

Once the Eimeria protozoa reach the intestinal epithelium, it is reproduced. During this process, the cells of the epithelium (enterocytes) can be affected by the rapid multiplication of the parasite. Avian coccidiosis causes intestinal inflammation processes, disruption of intestinal integrity, hemorrhages, and predisposition to bacterial infections. In addition, affected poultry lots can have high morbidity and mortality.

The economic impact of poultry coccidiosis

The economic impact of poultry coccidiosis is an important factor to consider. On the one hand, this parasitic disease produces lesions at the intestinal level and affects processes such as nutrient absorption and defense barrier. In addition, it causes a growth and development delay in the poultry and causes weight loss. On the other hand, when avian coccidiosis is severe, increased mortality and a low response to costly treatments are observed.

For these reasons, the economic impact may be difficult to estimate, but it is certainly considerable. For example, in the United States, the costs associated with treatments for poultry coccidiosis are more than $90 million. Meanwhile, worldwide, costs can exceed $300 million annually, possibly more.

What role does coccidiosis have in necrotic enteritis?

Avian coccidiosis is considered the main predisposing factor for the development of necrotic enteritis. This pathology is caused by Clostridium perfringens. The lesions generated by the protozoan parasite favor the multiplication and colonization of this pathogenic bacteria in the poultry intestine.

The gram-positive bacteria Clostridium perfringens is a normal inhabitant of the intestinal microbiota and not all strains are harmful. However, in stressful or pathological events such as coccidiosis, defense and immunity barriers are reduced. Thus, the growth of pathogenic strains is exacerbated, and toxin production begins. Clostridium perfringens produce up to 12 toxins that cause necrotic enteritis in poultry. The most important are alpha, beta, epsilon, and iota. These toxins are produced by the biotypes of C. perfringens called A, B, C, D, and E.

For this reason, it is of great importance to establish coccidiosis control strategies to prevent the occurrence of secondary infections.

Classical control of poultry coccidiosis

Anticoccidial drugs

The parasite that causes avian coccidiosis is usually treated using drugs called anticoccidials that aim to eliminate or control the number of parasites present.

Some of these commonly used products include ionophores or amprolium, for example. However, in recent years it has been discovered that resistances to these drugs are increasing. The excessive or inappropriate use of these drugs causes parasites to develop resistance mechanisms and they lose efficiency. For this reason, it is advisable to avoid their use or to incorporate alternative control strategies.

Vaccination

In countries such as the United States, the field of vaccines against avian coccidiosis has been notably developed. Live vaccines are considered the most common vaccine presentation and include both attenuated and non-attenuated oocysts.

The mechanism of live vaccines is to expose poultry production to low doses of the pathogen. In this way, the animals can generate a robust immune response that protects them against future challenges. Vaccinated younger poultry can develop a strong immune memory against avian coccidiosis. It is recommended to vaccinate day-old chicks and booster, if necessary, later.

Generally, these vaccines for broilers include E. acervulina, E. maxima, E. mevati, and E. tenella species. For laying hens, they include E. tenella, E. mevati E. acervulina, E. maxima, E. brunetti, E. hagani, E. necatrix, and E. praecox.

However, the efficiency of these vaccines may vary between countries, since the Eimeria species used cannot guarantee the protection of regions affected by other species. In addition, as these are live vaccines, their circulation is limited due to the risk of introducing pathogenic species in regions where they did not exist previously. Furthermore, the possibility of poultry farms developing outbreaks of coccidiosis caused by the live vaccine must be considered. This event can occur mainly in rainy seasons or highly humid areas that favor the pathogenicity of Eimeria.

Alternative strategies for the control of coccidiosis

Considering the limitations of classical control strategies against avian coccidiosis, it is important to examine other alternatives. These strategies have different mechanisms of action that allow reducing the parasite load, reducing intestinal lesions, or improving the digestive physiology of the poultry.

Among the control alternatives for poultry coccidiosis, there are essential oils whose mechanisms of action are variable. In addition, other alternatives are prebiotics and probiotics that are used simultaneously have an effect against Eimeria. Fatty acids administered in the diet have also shown an effect against the intestinal parasite.

On the other hand, there are products such as intestinal optimizer pronutrients that have been shown to have a potent effect against avian coccidiosis.

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Intestinal optimizer pronutrients

Intestinal optimizer pronutrients, contained in the product Alquernat Zycox, developed by Biovet S.A., are molecules of natural origin that offer multiple advantages for the prevention of avian coccidiosis.

These pronutrients stimulate genes associated with the defensive functions of immune cells in the intestine. Specifically, the optimizers pronutrients increase the expression of essential gut interleukins to control Eimeria species. In this way, the local immunity of the digestive system is activated and reinforced, which prevents the pathogenic effect of the parasite.

On the other hand, field trials show that Alquernat Zycox is efficient against any Eimeria species, which is an advantage compared to the limitations of classical anticoccidials and vaccines.

In addition, Alquernat Zycox can be complemented with the use of Alquernat Nebsui, which contains intestinal conditioner pronutrients. The product contributes to the control strategies of this intestinal parasite. These pronutrients favor the regeneration of enterocytes affected by Eimeria. In this way, the absorption of nutrients is increased, as well as the optimization of digestive processes.

CONCLUSIONS

Avian coccidiosis is one of the most important infectious diseases of poultry farming in the world. This protozoan causes millions of dollars in losses to the poultry industry every year.

There are multiple options for dealing with the disease. Classical strategies include anticoccidial drugs that seek to eliminate the parasite, but resistance to these drugs has been found in recent years. On the other hand, vaccines are another strategy to create immunity in poultry against the parasite but may have commercial or epidemiological limitations.

Alternative strategies for the control of avian coccidiosis have multiple fields of action. Among these strategies is the use of essential oils of fungal or botanical origin. The use of organic acetates and antioxidants has also been studied, as well as prebiotics and probiotics.

Finally, there are intestinal optimizers pronutrients that have multiple advantages for the control of avian coccidiosis. Thanks to the activation of the local immune system of the intestine, they can control all Eimeria species affecting poultry. In addition, due to their mechanism of action, they do not create resistance and do not leave residues in animals or their products.