Commercial poultry birds especially broiler birds have gained importance in terms of Feed Conversion Ratio (FCR) as a great deal of expense is gone under the heading of feed while farming. Parasitic diseases, usually chronic, cause poor FCR of the birds and thus have more economical importance. Flock un-uniformity, stunted growth and dullness are the clear indications of parasitic diseases. Coccidiosis, a parasitic disease, is still one of the important diseases that are notorious for the production loss in the birds. Coccidiosis is the infection notable on the basis of clinical signs; however, a term Coccidiasis is used for a light infection, not showing any considerable signs, without any gross entriritis. Coccidiosis is mostly a concern of intensive poultry farming.
This disease is caused by a coccidial parasite (Eimeria) that multiplies in the intestinal mucosa of the host. Many species of it have been identified in the domestic and commercial poultry but E. necatrix and E. tenella are associated with a high pathogenicity and mortality. They cause intestinal and cecal coccidiosis respectively. The prevalence of E. tenella is found to be greatest in Lahore and Faisalabad area. Seasonal relevancy is also correlated with coccidiosis i.e. highest prevalence is found in autumn and summer; this may be due to hot and humid season at that time. Coccidiosis is highly suggestive of poor litter conditions.
Onset of coccidiosis is occurred when sporulated oocysts are ingested by birds. Emeria has a direct type of lifecycle that needs no intermediate host. Young birds pick up the infection from contaminated litter, droppings or from soil. It may be due to previous exposure of coccidiosis and improper disinfection on the farm or through contaminated transmission by visitors. Oocysts are non-sporulated when secreted in the droppings. To become potentially infective the oocysts must undergo sporulation in the external environment. It requires warmth, humidity and air. The whole life cycle of the coccidia is so rapid that it comprises only 5-7 days in the body. From a few oocysts ingested it may result into thousands or millions of oocysts. The oocysts fail to sporulate if conditions are unfavorable, becoming un-infective for the bird. Oocysts do not sporulate in dry litter.
Severity of the disease depends upon the amount of the oocysts ingested, immune status of the bird and predisposing factors. Coccidia cause necrosis and hemorrhage of the intestinal mucosa resulting in hemorrhage, dehydration and death. Early signs include sudden increase in daily mortality and later bloody droppings. The birds become pale due to anemia, dull and show poor growth resulting in a reduction in daily weight gain. Feather shininess is lost and FCR becomes poor. Laying birds decrease egg production. Postmortem lesions of hemorrhagic enteritis are characteristic of coccidiosis. Enlarged, blood filled ceca and intestines are seen depending upon the species of Emeria.
Intestinal scrapings are examined under microscope for oocysts. However diagnosis can be made on the basis of lesions depending upon the personal experty.
Coccidial infection usually induces good immune response and the birds remain immune for the rest of their life due to low exposure of infection afterwards. “Trickle” infection induces best level of immunity.
For the treatment of coccidiosis following drugs are used as coccidiocidal agents:
- Sulfaquinoxaline @ 0.05 % in feed
- Amprolium Plus @ 0.024 % in water
- Toltrazuril
To prevent coccidiosis following measures should be taken:
Proper Hygiene and Litter Management: Litter should be kept dry and racking should be managed during hot humid weather. Farm should be sprayed with 5 % formaline or 5% CuSO4.
Immunization: Live attenuated vaccines are available worldwide; PARACOX®, UK. Immunity against coccidiosis is species specific, no cross protection so this strategy is not well developed. However natural “Trickle Infection” on farm is considered best for protection.
Coccidiostats: These compounds inhibit the Emeria to infect but they don’t kill it. Quinolones, Amprolium, Nicarbazine, Toltazuril, Clopidol and Monensin are useful coccidiostatic agents. However rotation or shuttling must be considered as resistance is developed after prolonged use of single drug. May be added in feed or water.
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