MASTERING COCCIDIOSIS: Cocci Clinic Series – Part 2

Decoding Coccidia: Spot the Tell-Tale Signs & Navigate Diagnosis for your Farm

Written by Zamira Australia

What is Coccidiosis?

Coccidiosis is an intestinal infection in chickens caused by a group of intracellular parasites belonging to the genus Eimeria. Seven common Eimeria species are known to cause intestinal infections in poultry, with four of them regularly leading to enteritis and mortality (see table below). Each Eimeria species invades specific sites of intestinal cells, resulting in seven distinct intestinal infections.

Understanding Post-Coccidiosis Immunity in Flocks

Following a coccidiosis infection in a flock, surviving chickens develop some degree of immunity to protect against future infections for a limited period. This protection is specific to the Eimeria strain that caused the initial infection, offering no cross-protection against infections by other Eimeria strains.

Clinical Signs of Coccidiosis

Symptoms of coccidiosis most commonly occur in young chickens but are rarely observed in chickens under two weeks of age. The clinical signs of coccidiosis in chickens are directly linked to the Eimeria strain and the level of infection at any given time.

Eimeria strains that invade and destroy the deeper layers of intestinal cells may cause bleeding and mucus production, which are passed in droppings. Affected chickens appear depressed, cease eating feed and drinking water, seek isolation, exhibit ruffled feathers, and experience rapid weight loss. Severe infections often result in significant mortality.

Subclinical coccidiosis is caused by Eimeria strains that do not infect and destroy the deeper cells lining the intestine. The main signs of infection include a depressed growth rate, adverse feed conversion efficiency, and gradual weight loss. Affected flocks may not experience mortality but still suffer adverse economic consequences.

Unique Effects of Different Eimeria Strains on Poultry

Coccidia infections are confined to the intestines, and the site of infection varies between strains of coccidia. Typical patterns among the four major Eimeria species are outlined in the table below. Coccidiosis can occur more than once within the lifetime of a broiler, with different Eimeria species infecting a chicken simultaneously. Effects may vary depending on the infection load, stage of infection, nutritional status, and concurrent infections.

Table : Four primary species responsible for enteritis and/or mortality in poultry

Understanding the Impact of Concurrent Infections on Poultry Health

Clostridia
Both Clostridia perfringens and Eimeria spp. are capable of causing serious enteric disease individually, and potentially more serious disease when both infections occur simultaneously. The incidence of concurrent infection usually occurs under all practical conditions. Coccidia infection has the potential to predispose the intestinal epithelium to Clostridia invasion; therefore, managing coccidiosis is an important part of reducing the effects of Clostridia infection.

Clostridia perfringens is endemic in poultry flocks and remains a serious economic concern for the poultry industry. The organism survives in the poultry farm environment and readily infects and colonises the intestines, especially the caecum, once ingested by the chicken. The pathogenesis of infection varies with the strains of Clostridia perfringens and its potential for toxin production. The severity of pathological damage is influenced by factors such as intestinal integrity, concurrent infection, and the age of chickens. Clinical infection is often recognised as Toxaemia (septicaemia) or Necrotic enteritis, of varying degrees.

Immunosuppressive viruses
The two most common and endemic viral infections in broiler flocks associated with immunosuppression are Infectious Bursal Disease Virus (IBDV) and Marek’s Disease Virus (MDV).

Both IBDV and MDV have the potential to influence the coccidia lesions by negatively affecting immune response to coccidia challenge. Exposure to coccidia challenge and both viral infections is frequently experienced during the first two weeks of life. Concurrent infection by either single or both viruses in commercial flocks has the potential to exacerbate coccidia lesions, mortality from coccidiosis and adversely affect commercial parameters. Concurrent infection may lead to the misinterpretation of efficacy of anticoccidials in use.

There is potential risk that these viral infections, individually or concurrently, would directly influence the incidence of coccidia lesions, clinical coccidiosis, and immunity to coccidiosis. It is worth considering that the continued presence of coccidia lesions or an inadequate immune response may indicate a concurrent infection with either of the viruses.

Mastering Coccidiosis Diagnosis & Management with Zamira Australia

Clinical signs of coccidiosis among chickens are not sufficient for a definitive diagnosis; however, the presence of mucus and blood in the faeces is suggestive of the disease. A postmortem conducted by a professional is often warranted for a definitive diagnosis. 

Zamira Technical Specialists are qualified veterinarians with extensive experience in poultry postmortems and coccidia diagnosis. With teams located in Australia, Southeast Asia, and South Asia, Zamira Australia is well-equipped to collaborate with you on tailored solutions to meet your specific needs. Our commitment to efficient delivery of specialised products, services, and on-the-ground support ensures that we effectively address the unique requirements of each market and customer.

While the incidence of coccidiosis in chickens is endemic and eradication is not feasible, proactive steps can be taken to control it, particularly with anticoccidials. Zamira Australia offers a comprehensive range of anticoccidials specifically developed for rotation and shuttle programs. As your trusted animal health partner, Zamira brings extensive experience and expertise to tailor a solution to meet your flock’s coccidiosis prevention and treatment requirements.

Part 3: Prevention or Treatment? The Ultimate Strategy Against Coccidiosis – coming soon!

Stay tuned for our next instalment in Zamira’s Cocci Clinic Series for insights into the ultimate strategy against this poultry threat.

Revisit Part 1: Navigating Coccidiosis: Understanding the Life Cycle and Best Practices for Management

Part 1 of Zamira’s Cocci Clinic Series takes you on a journey through the life cycle of this persistent pathogen, equipping you with the best practices for effective management.


Zamira is an Australian animal health company with a mission to improve the health, wellbeing and productivity of animals through prevention, detection and treatment . Read more about us here.

How can we help you?

Want to find out more about how to prevent and control coccidiosis in your flock? Zamira Australia has teams in Australia, South East Asia and South Asia who can work with you on a tailored solution to meet your needs. Fill out the form below and we’ll get in touch with you shortly.

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