Exploring the Crucial Role of Coccidiostats in Disease Management
1. Introduction
Over recent decades, the poultry industry has seen remarkable growth driven by advancements in technology and genetics. However, this intensification has brought challenges such as increased stress and disease incidence, notably coccidiosis caused by protozoa parasites. Coccidiosis affects poultry health and productivity, leading to poor weight gain, feed conversion and egg production, along with heightened susceptibility to other infections like mycoplasmosis and colibacillosis. In warm, humid environments, coccidiosis spreads easily among birds, resulting in significant economic losses, estimated at 2 billion euros annually worldwide. To mitigate these losses and ensure sustainable production, preventive measures including the use of anticoccidial medications in feed, are crucial. Stallen South Asia Pvt. Ltd. offers a wide range of anticoccidial products, including Anacox, Anacox-Plus, Cozuril, Racoxi, Robinex, Duacox and Amprostat-K. These products are specifically formulated for the prevention and treatment of coccidiosis in poultry.
2. Coccidiosis: – In poultry, Coccidia undergoes a seven-day life cycle both outside (sporogony) and inside the host, involving asexual and sexual stages of reproduction. Outside the host, unsporulated oocysts shed infeces become infective only after sporulation, a process requiring warmth and oxygen for 24 to 48 hours. Each sporulated oocyst contains four sporocysts, each with two sporozoites. Upon ingestion by the bird, active oocysts release sporocysts in the intestine, where sporozoites are liberated.
2.1. Symptoms: – Untreated, these host-specific protozoa invade the intestinal tract, causing damage to epithelial cells, impairing nutrient absorption, and leading to diarrhoea and potential bleeding. Even mild infections can facilitate secondary infections, worsening the animal’s health. Chickens can be parasitized by at least seven Eimeria species, each with a varying four to seven-day life cycle. In broiler chickens, Eimeria acervulina, Eimeria maxima, and Eimeria tenella are economically significant. This disease predominantly affects young animals, as they develop immunity rapidly following initial exposure. However, there is no cross-immunity between different Eimeria species in birds, leading to the possibility of subsequent outbreaks caused by different strains.
3.Coccidiostats: –Coccidiostats are chemical compounds, either synthetic or naturally derived from microorganisms, that are effective against protozoa parasites responsible for coccidiosis. Unique formulations such as Anacox (Maduramicin), Anacox-Plus/ Duacox (Maduramicin+Nicarbazin), Cozuril (Diclazuril), Racoxi(Salinomycin), Robinex (Robenidine)and Amprostat-K (Amprolium) are specifically crafted to prevent and treat poultry coccidiosis effectively.
4. Anticoccidial products are categorized into three main groups based on their origin:
a) Synthetic Compounds: These are chemically synthesized drugs, often referred to as “chemicals.” They have a specific mode of action targeting the parasite’s metabolism. For instance, amprolium (Amprostat-K) competes with the absorption of thiamine (vitamin B1) by the parasite.
b) Polyether Antibiotics or Ionophores: These products are derived from the fermentation of Streptomyces spp. or Actinomadura spp. They disrupt coccidia by interfering with the balance of crucial ions such as sodium and potassium. There are several groups of ionophores:
- Monovalent ionophores e.g., monensin, narasin, and salinomycin (Racoxi)
- Monovalent glycosidic ionophores e.g., maduramicin (Anacox) and semduramycin
- Divalent ionophores e.g., lasalocid
c) Mixed Products: Some formulations consist of a combination of either a synthetic compound and an ionophore e.g., nicarbazin/narasin or two synthetic compounds e.g., Maduramicin & Nicarbazin (Anacox / Duacox). These mixed products are also utilized in the control of coccidiosis.
Anticoccidial compounds exert their effects on the parasite metabolism, although the precise mechanisms are not always fully understood. They can be broadly categorized based on their mode of action.
5. Mechanism of Action
a) Products Affecting Cofactor Synthesis:
- Ethopabate: Blocks synthesis of para-aminobenzoic acid (PABA) and nucleic acids, particularly effective against Eimeria maxima and Eimeria brunetti.
- Sulphonamides: Interfere with dihydropteroate synthetase reaction, effective against E. brunetti, E. maxima, and Eimeria acervulina.
- Pyrimethamine: Inhibits dihydrofolate reductase enzyme, synergistic with sulphonamides, affecting second-generation schizonts.
- Amprolium: Thiamine antagonist, blocks thiamine absorption, particularly effective during schizogony.
b) Product affecting mitochondrial functions
- Quinolone Drugs: Buquinolate, Decoquinate, and Nequinate inhibit coccidia respiration by blocking electron transport in mitochondria, arresting sporozoite development.
- Meticlorpindol: Inhibits electron transport in mitochondria, potentially at a different level than quinolones. It shows synergy with 4-hydroxiquinolones.
- Nicarbazin: Its mode of action is uncertain but has been observed to inhibit mitochondrial functions and affect calcium ion accumulation.
- Robenidine: Though its exact mechanism is unknown, it’s believed to inhibit oxidative phosphorylation in mitochondria.
- Toltrazuril: This compound affects enzyme activities in the respiratory chain, possibly also influencing plastid-like organelles. It is effective against all intracellular stages of Eimeria spp. and induces changes in parasite organelles without impairing natural immunity.
c) Products affecting cell membrane functions
Polyether antibiotics, such as ionophores, disrupt cell membrane transport of mono- or divalent cations (Na⁺, K⁺, and Ca²⁺), leading to osmotic damage. These drugs accumulate in extracellular parasite stages within the intestine lumen. Depending on the dosage, ionophore anticoccidials can promote the development of immunity against coccidia.
d) Product with unknown mode of action
Diclazuril, a nucleoside analogue, likely disrupts nucleic acid synthesis, impacting later phases of coccidia differentiation. It interferes with parasite wall synthesis, causing abnormal thickening and incomplete oocyst wall formation, along with zygote necrosis in Eimeria brunetti and Eimeria maxima. Halofuginone, a quinazolinone derivative, affects the first generation of schizogony, but its precise mode of action remains unknown.
6. Coccidiostats Programmes
- Single Drug Programmes: Involve using the same drug in the feed of a single flock. Over time, efficacy declines due to the selection of resistant strains.
- Shuttle Programmes: Incorporate different synthetic drugs sequentially in starter, grower, finisher diets, and during withdrawal. This strategy prevents resistance development to one drug by alternating with others.
- Rotation Programmes: Alternate the use of two or more drugs in successive flocks at intervals of several months. Most rotations involve synthetic drugs in starter and/or grower feeds to preserve efficacy and reduce resistance incidence.
| Option /Months | Nov | Dec | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | |
| Shuttle | Prestarter/Starter | Robinex(Robenidine)/Cozuril (Diclazuril) | Robinex (Robenidine) /Cozuril (Diclazuril) | Robinex (Robenidine) /Cozuril (Diclazuril) | |||||||||
| Finisher | Anacox(Maduramycin)/Anacox-plus(Maduramicin + Nicarbazin) | Anacox(Maduramicin) | Anacox (Maduramycin ) / Anacox-plus (Maduramicin + Nicarbazin) | ||||||||||
| Rotation | Day1 toMarketing | Cozuril (Diclazuril)/Duacox (Maduramicin+ Nicarbazin) | Anacox (Maduramicin ) | Cozuril (Diclazuril) / Duacox (Maduramicin + Nicarbazin) | |||||||||
7. Vaccine
Vaccination offers an alternative to drug-based control of coccidiosis, stimulating strong immune responses in birds against avian coccidia. Effective vaccination involves administering vaccines containing sporulated oocysts of pathogenic Eimeria species, with E. maxima being particularly immunogenic. Recent advancements include “in ovo” inoculation into embryonated eggs for precise and repeatable vaccine delivery.
Vaccination methods include oral administration, eye spray, or hatchery spray, but high costs have limited widespread implementation. Three types of vaccines are used: non-attenuated, attenuated, and recombinant. Non-attenuated vaccines have been effective for decades, especially when in-feed anticoccidials fail. Attenuated vaccines, while still used, often require supplementation with adjuvants to enhance immunity. Recombinant vaccines, though promising, face challenges in identifying antigens for effective immunity against field strains.
Rotation programs, alternating between vaccination and drug use in successive flocks, can sustain coccidiosis control over the long term.
8. Management and Control Approach
To further combat coccidia, it’s crucial to focus on sanitation and hygiene practices. Implementing strict sanitation measures, such as regular cleaning of equipment and facilities, helps reduce the risk of coccidia transmission. Regular monitoring of flock health is essential for early detection of coccidiosis outbreaks. This includes conducting regular fecal examinations and observing flock behaviour for signs of illness. Prompt diagnosis allows for timely intervention and treatment, minimizing the impact of the disease on poultry health and productivity. Furthermore, integrating biosecurity measures can help prevent the introduction of coccidia into poultry facilities. This involves restricting access to visitors, implementing proper biosecurity protocols for personnel and equipment, and preventing contact between poultry flocks and potential sources of contamination.