Summary of Information on Coccidiosis in Poultry
Dr. Hogir Omar / Poultry Disease Consultant
5/ 9/ 2025
- Introduction to Coccidiosis
Coccidiosis is a widespread disease globally, and particularly in Iraq, affecting all types of poultry. It is caused by single-celled parasites of the genus Eimeria. These parasites are often host-specific and infect the intestinal lining or caecum of poultry.
Main species of coccidia in chickens:
- Eimeria acervulina
- E. brunetti
- E. maxima
- E. mitis
- E. necatrix
- E. praecox
- E. tenella
Life cycle of coccidia: It involves asexual and sexual stages of reproduction within host cells. Infection begins with the ingestion of the sporulated oocyst from the environment.
Diagnosis of coccidiosis: The differential diagnosis of coccidia species depends on eight main characteristics, such as the (affected intestinal region, the overall appearance of the lesion, the shape of the parasite, and cross-sectional immunological tests).
- Examination and Classification of Lesions
Identifying and classifying lesions is crucial for diagnosis. Some of the main types of lesions are:
Type 1: E. acervulina: Infects the duodenum. Characterized by “ladder-like white lesions”.
Type 2: E. maxima: Infects the mid-intestine. Known for its large, reddish-brown parasites.
Type 3: E. necatrix: Infects the mid-intestine. Causes a “salt and pepper” appearance.
Type 4: E. brunette: Infects the lower intestine. Often causes severe weight loss. The fifth species, E. tenella, causes cecal coccidiosis or “bloody” coccidiosis, and infects the cecum.
Lesions are classified using the Johnson-Reed method: a technique that assigns a numerical score to the overall severity of lesions, ranging from 0 to +4.
- Preparation of Coccidia Oocysts
Collection of oocysts: The method of oocyst collection depends on its purpose (from litter, for vaccine preparation). Equipment includes a centrifuge, a blender, and a sieve.
Sporulation and storage of oocysts: All oocysts must sporulate before becoming infectious (within 24-72 hours). They are stored in a potassium dichromate solution.
Counting oocysts: Two methods are used:
- McMaster chamber method.
- Hemocytometer method (preferred for clean samples).
- Procedures and Protocols for Anticoccidial Drug Testing
Three types of tests are used to evaluate anticoccidial drugs:
- Battery tests: To determine the efficacy of new compounds and to measure dose response.
- Floor pen tests: To provide performance data under controlled conditions.
- Commercial tests: To test drugs under typical field conditions.
Measurements required to assess the disease: Mortality, weight gain, feed conversion, lesion scores, hematocrit values, etc.
Statistical analysis of the disease: Data are analyzed using appropriate statistical designs, such as a completely randomized block design.
- Epidemiology and Control of Coccidiosis
Coccidiosis is a common and widespread disease in broiler chickens worldwide.
Factors influencing its occurrence:
- Widespread distribution of oocysts.
- The pattern of infection peaks between the 4th and 6th week.
- Overall flock health and other diseases.
Key elements for control:
- Use of anticoccidial drugs and vaccines.
- Management of the housing environment (ventilation, litter moisture, stocking density).
- Monitoring feed quality and ensuring uniform mixing of medications.
- Anticoccidial Drugs and Vaccines
Anticoccidial drugs:
- Amprolium: Inhibits thiamine absorption.
- Nicarbazin: Highly effective but heat-sensitive.
- Polyether ionophores (e.g., monensin, salinomycin): Form lipid-soluble complexes with cations.
- Triazines (e.g., decoquinate): Parasiticidal.
Vaccines used for coccidiosis prevention:
- Inactivated vaccines: e.g., Coccivac, Immucox.
- Live attenuated vaccines: e.g., Paracox (the first live attenuated vaccine).
- Subunit vaccines: e.g., CoxAbic.
Importance of vaccines: They offer protection similar to drugs and lead to replacement of resistant strains with susceptible ones.
Conclusion
Prevention and control of coccidiosis in poultry requires a comprehensive approach that combines the use of anticoccidial drugs and vaccines with high standards of animal health, nutrition, and production environment management.
References
“Poultry Coccidiosis: Diagnostic and Testing Procedures” by Donal P. Conway and M. Elizabeth McKenzie. 3rd edition, 2007.
