''Cystoisospora belli'', previously known as ''Isospora belli'', is a

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

that causes an intestinal disease known as

cystoisosporiasis Isosporiasis, also known as cystoisosporiasis, is a human intestinal disease caused by the parasite ''Cystoisospora belli'' (previously known as ''Isospora belli''). It is found worldwide, especially in tropical and subtropical areas. Infection of ...

.Centers For Disease Control: https://www.cdc.gov/parasites/cystoisospora/index.html This protozoan parasite is opportunistic in immune suppressed human hosts. It primarily exists in the epithelial cells of the small intestine, and develops in the cell cytoplasm. The distribution of this

coccidia Coccidia (Coccidiasina) are a subclass of microscopic, spore-forming, single-celled obligate intracellular parasites belonging to the apicomplexan class Conoidasida. As obligate intracellular parasites, they must live and reproduce within an ...

n parasite is cosmopolitan, but is mainly found in tropical and subtropical areas of the world such as the Caribbean, Central and S. America, India, Africa, and S.E. Asia. In the U.S., it is usually associated with HIV infection and institutional living.

Morphology

A fully mature (sporulated) oocyst of genus ''Isospora'' is a spindle-shaped body that has two sporocysts that contain four sporozoites each. The oocysts of ''Cystoisospora belli'' are long and oval shaped. They measure between 20 and 33 micrometers in length and between 10 and 19 micrometers wide.

Life cycle

*An oocyst with one sporoblast is released in stool of infected person *After the oocyst has been released, the sporoblast matures further and divides into two *After the sporoblasts divide they create a cyst wall and become sporocysts *The sporocysts each divide twice, resulting in four

sporozoites Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism is ...

*Transmission occurs when these mature oocysts are ingested *The sporocysts excyst in the small intestine where sporozoites are released *The sporozoites then invade epithelial cells and schizogony is initiated *When the schizonts rupture, merozoites are released and continue to invade more epithelial cells *Trophozoites develop into schizonts, containing many merozoites *After about one week, development of male and female gametocytes begin in the merozoites *Fertilization results in the development of oocysts, which are released in the stool The sporulation time of this parasite's egg is usually 1–4 days, and the entire life cycle takes about 9–10 days. The infective stage found in stool is the mature oocyst. The mature oocyst for Cystoisospora belli can remain infective in the environment for months.

Symptoms

Immune competent individuals are usually asymptomatic to this parasite's infection. But clinical symptoms such as mild diarrhea, abdominal discomfort, and low grade fever for approximately one week has been observed in some individuals.

Immunocompromised Immunodeficiency, also known as immunocompromisation, is a state in which the immune system's ability to fight infectious diseases and cancer is compromised or entirely absent. Most cases are acquired ("secondary") due to extrinsic factors that a ...

people are more severely affected by ''Cystoisospora belli'' and can experience extreme diarrhea that can lead to weakness, anorexia, and weight loss. Other symptoms of cystoisosporiasis include abdominal pain, cramps, loss of appetite, nausea, vomiting, and fever, that can last from weeks to months.

Diagnosis and treatment

''Cystoisospora belli'' is diagnosed by identification of the oocyst through examining a stool sample under a microscope. The diagnostic stage is the immature oocyst that contains a spherical mass of protoplasm. In other words, the oocyst that is diagnosed in the stool sample is unsporulated, and contains only one sporoblast. For stool diagnosis, direct smear, concentration smear, microscopic wet mount, or iodine stains of fecal smears are adequate. But for easy screening, acid-fast stains is recommended. If stool test is negative, and biopsies of the small intestine is performed, different stages of schizogony and

sporogony Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism i ...

should exist in the epithelial cells, but the alteration of the villi is not necessarily present. Eosinophilia may also be seen unlike in the case of other protozoal infections. This infection is easily treated with antibiotics. The most common antibiotic that is prescribed is co-trimoxazole (trimethoprimsulfamethoxazole), more commonly known as Bactrim, Septra, or Cotrim.
In AIDS patients, treatments can result in the disappearance of the symptoms, but recurrence of symptoms is common. In order prevent the recurrence, medication is continued in AIDS patients and other immunosuppressed patients.

Transmission and prevention

Cystoisospora belli does not require an intermediate host and currently is only known to transmit from person to person. The method of transmission is ingesting food or water that has been contaminated with feces from someone who is infected. Washing your hands with soap and warm water after using the toilet, changing diapers, and before handling food is vital. Also, educating children the importance of hand-washing and good hygiene practice is important. Because HIV-AIDS patients will have higher risk of symptomatic intestinal parasitic infections, and pathogenic burden can increase disease progression and contributes to early death, routine screening of parasites especially in patients with lower CD4 count should be emphasized.Gupta, K., Bala, M., Deb, M., Muralidhar, S., & Sharma, D. K. (2013). Prevalence of intestinal parasitic infections in HIV-infected individuals and their relationship with immune status. Indian Journal of Medical Microbiology, 31(2), 161-165. doi:10.4103/0255-0857.115247

History

''Isospora belli'' was discovered by

Rudolf Virchow Rudolf Ludwig Carl Virchow (; or ; 13 October 18215 September 1902) was a German physician, anthropologist, pathologist, prehistorian, biologist, writer, editor, and politician. He is known as "the father of modern pathology" and as the founder ...

in 1860 and was named by Charles Morley Wenyon in 1923. The parasite is now known as ''Cystoisospora belli''.

References

{{Taxonbar, from1=Q83792086, from2=Q2715018 Conoidasida