Coccidiosis

The article discusses the pathogen, life cycle, clinical disease, prevention, immune response, detection, and epidemiology of Coccidiosis.

Coccidiosis, as defined in the original article, is an animal disease caused by a protozoan parasite. This protozoan parasite can be examined using binocular compound microscopes. Binocular compound microscopes are used to differentiate the seven species of Eimeria that is known to cause this disease in chickens. The seven Eimeria species, classified using binocular compound microscopes are Eimeria acervulina, E. brunetti, E. maxima, E. mitis, E. necatrix, E. praecox, and E. tenella.

The oocysts of these protozoan parasites, when studied under binocular compound microscopes, vary in size with E. maxima being the largest and E. mitis being the smallest. The oocysts of coccidia can only be differentiated by extracting DNA samples from the oocysts and by using molecular techniques and a specialized microscope.

It takes four to six days to complete the life cycle of the Eimeria oocysts from ingestion to release. Their life cycle begins from the oocysts being ingested by chickens. Due to the grinding motion and enzymes of the chicken’s digestive system, the oocysts are released into the sporozoite stage. The sporozoites will then invade the epithelial lining cells of the chicken’s intestine within six hours. It is in the epithelial that the sporozoite will replicate and then develop into the merozoite stage. Binocular compound microscopes will be useful in examining and studying these stages. The merozoites stage is the stage that could determine the effect of the Coccidiosis infection. It is in this stage that the host epithelial cells of the merozoites lyses or becomes destroyed. Also, according to the original article, as many as four generations of merozoites can replicate and reproduce during this stage (number of merozoites generations dependent upon the Eimeria species). Next, the merozoites will develop into micro and macro gametocytes by an unidentified signal. Micro gametocytes are male gametocytes while macro gametopcytes are female gametocytes. A zygote is the combination of these gametes. Zygotes will then develop into hard-shell covered oocysts which are released in the feces of the chicken and the cycle continues.

The observed symptoms of chicken infected with Coccidiosis infection typically manifests decreased weight gain, droopiness, emaciation, and death. As mentioned before, the effects of this infection is seen in the lysis of the epithelial lining of the chicken’s intestines.

Anti-coccidial drugs have helped poultry farmers in preventing the spread of this infection. The anti-coccidial drugs are mixed together with the chicken feeds and are removed a week prior to the sale of the chicken.

Alternative control measures are now being done by poultry farmers, according to the original article, because of the Eimeria parasite’s ability to become resistant to the anti-coccidial drugs. Chickens are now being vaccinated with low doses of attenuated Eimeria oocysts to develop immunity.

Chickens can only develop specific immunity which means they are only immune to a specific species upon infection, not to the other species.

Eimeria infection can only be detected and diagnosed upon examination of the tissues of the chicken’s intestines. Binocular compound microscopes can be used to examine intestinal scrapings at 250-400x magnification.