Coccidiosis in Poultry: Causes, Transmission and Control

Coccidiosis is a common and highly contagious parasitic disease that has significant impacts on poultry production around the world. Globally, it is estimated to cost the industry around 10 billion USD each year due to economic losses generated from reduced performance as well as cost of prevention and treatment (Blake et al., 2020). With the growing human population and subsequent increase in demand for poultry products, understanding coccidiosis and its control is more important than ever.

Causes

Coccidiosis is a parasitic disease of the intestinal tract caused by coccidia, a very large and diverse group of protozoa. Although these protozoa can infect a wide variety of organisms, they are generally species-specific (Muller and Hemphill, 2013). Several species of the Eimeria genus are responsible for causing disease in chickens including E. maxima, E. acervulina, and E. tenella. Each species typically targets a specific part of the intestines and has a different pathogenicity. Identification of specific species helps to aid with treatment of diseased animals. For example, infection of E. maxima can result in pinpoint blood clots of the mid-intestine, while E. acervulina can result in white, scattered lesions throughout the duodenum (Johnson and Reid, 1970). 

Transmission

Coccidia are transmitted through the ingestion of sporulated oocysts from the environment, which are shed in the excreta of infected birds. Oocysts must go through a process called sporulation in the environment to become infective, which requires optimal conditions of oxygen, temperature, and humidity (Waldenstedt et al., 2001). Once inside of the intestinal tract of a chicken, Eimeria invade the host’s intestinal cells and disrupt protein absorption, impair digestion, and increase cell permeability (Nabian et al., 2018). Depending on the species and severity, infection can result in elevated mortality, reduced growth, and poor performance. 

Control 

There are a variety of methods used to prevent and control coccidiosis including ideal farm management practices, anticoccidials, vaccines, and natural products. Proper ventilation and litter management are important to reduce moisture that aids in sporulation of the infective oocysts (Noah et al., 2019). Anticoccidial drugs, such as ionophores, can be added to the feed or water to directly kill or stop the development of the parasite. Anticoccidial resistance has been documented for most drugs available, but this can be slowed by rotating through different products with unique mechanisms of action (Chapman, 1997). Separate from anticoccidial drugs, vaccines utilize a small number of live oocysts sprayed directly onto chicks to induce protective immunity. Lastly, natural products, such as probiotics, prebiotics, and phytogenics, can be used to compliment a coccidiosis control program by improving intestinal integrity or modulating microbiome metabolism (Bortoluzzi et al., 2023). Best practices in poultry production include a variety of these approaches due to the broad nature of coccidiosis infection.