What is the Difference Between Eimeria and Isospora

The main difference between Eimeria and Isospora is that Eimeria does not use a paratenic host, whereas Isospora uses a paratenic host. 

Eimeria and Isopora are two genera of apicomplexan parasites causing the disease coccidiosis. The disease is common in poultry, cattle, and smaller ruminants, including sheep and goats. 

Key Areas Covered

1. What is Eimeria
– Definition, Features, Behaviour
2. What Isospora
– Definition, Features, Behaviour
3. Similarities Between Eimeria and Isospora
– Outline of Common Features
4. Difference Between Eimeria and Isospora
– Comparison of Key Differences

Key Terms

Eimeria, Isospora

What is Eimeria

Eimeria is a genus of parasites that belong to the phylum Apicomplexa. Coccidiosis is a disease caused by the genus Eimeria. It occurs in animals such as poultry, cattle, and smaller ruminants, including sheep and goats. Also, the life cycle stages are visible under a microscope. The asexual (merogony) stage, sexual (gametogony and fertilization) stage, and oocytes are the three stages of the life cycle of Eimeria. Oocytes have an oval or elliptical shape and are 28 µm by 22 µm in size. They have a thin, smooth shell.

Life Cycle – Phylum Apicomplexa

Freshly passed oocytes are unsporulated and contain one or two cells. After a few days, each oocyte becomes infective. Sporulated oocytes of Eimeria contain four sporocysts, each containing two sporozoites.

Figure 1: Eimeria Life Cycle

Furthermore, following the ingestion by a suitable host, the oocyte hatches to produce eight sporozoites. These sporozoites enter the intestinal mucosa and divide to form merozoites. And these merozoites are enclosed by meronts. Then, meronts are released from the infected cells into the intestinal lumen to penetrate new enterocytes. Here, the merogony cycle can be repeated depending on the species. Notably, the repeating merogony cycle can significantly increase the number of merozoites. However, merozoites produce microgametocytes (“male”) and macrogametocytes (“female”) within the enterocytes. Several microgametes occur in the microgametocyte, while a single macrogamete occurs in the macrogametocyte. After the disintegration of the microgametocyte, it releases microgametes that fertilize the macrogamete. This forms gamonts that develop into the unsporulated oocyte, which bursts from enterocytes passing through feces.  

What is Isospora

Isospora is another genus of parasites from the phylum Apocomplexa, forming the coccidiosis. However, the life cycle of Isospora also contains the asexual merogony stage, sexual gametogony stage, and oocyte stage. The oocyte of the Isospora is subspherical to ellipsoid in shape. The size of the oocyte is 20 by 15 µm. Also, meronts, merozoites, macrogametocytes, microgametocytes, gamonts, and oocysts are the intestinal stages of Isospora.

Figure 2: Isospora Oocyte

Moreover, Isospora uses a paratenic host in which the parasite does not need the host for its development. But it serves to maintain the parasite’s life cycle.

Similarities Between Eimeria and Isospora

• Eimeria and Isopora are two genera that cause coccidiosis. This disease is common in poultry, cattle, and smaller ruminants, including sheep and goats.
• They belong to the phylum Apicomplexa.
• Their asexual (merogony) and sexual (gametogony) reproduction occur inside enterocytes of the small intestine.
• They produce oocytes that infect enterocytes. Their oocyte contains eight sporozoites.
• They are not zoonotic.

Difference Between Eimeria and Isospora

Definition

Eimeria refers to a genus of coccidian protozoans that invade the visceral epithelia and especially the intestinal wall of many vertebrates, while Isospora refers to the genus of parasitic protozoans of the sporozoan subclass Coccidia.

Host

Eimeria does not use a paratenic host, while Isospora uses a paratenic host. 

Oocyte

The oocyte of Eimeria is oval or elliptical in shape and 28 µm by 22 µm in size, while the Isospora oocytes are subspherical to ellipsoid in shape and 20 by 15 µm in size.

Signs

The signs of Eimeria infection are diarrhea, dysentery, dehydration, and loss of appetite, while the signs of Isospora infection are diarrhea, dehydration, weight loss, and depression.

Conclusion

In brief, Eimeria and Isospora are parasites that cause coccidiosis in animals. Also, they belong to the phylum Apicomplexa. Significantly, Eimeria does not use a paratenic host. Additionally, the signs of Eimeria are diarrhea, dysentery, dehydration, and loss of appetite. In comparison, Isospora uses a paratenic host. Its signs are diarrhea, dehydration, weight loss, and depression. Therefore, the main difference between Eimeria and Isospora is their type of host.

References:

1. Eimeria species – sheep – learn about parasites – western college of veterinary medicine. Learn About Parasites. (2021, April 4). 
2. Isospora suis – learn about parasites – western college of veterinary medicine. Learn About Parasites. (2021b, April 12). 

Image Courtesy:

1. “Eimeria life cycle usda” By USDA – Own work (Public Domain) via Commons Wikimedia
2. “Isospora belli” By UFRGS – Own Work (CC-BY 4.0) via Commons Wikimedia