INTESTINAL PARASITE: Cyclospora cayetanensis (Rakhi Gurung Jha)

 INTESTINAL PARASITE: Cyclospora cayetanensis

Rakhi (Gurung) Jha

Department of Science and Teachnology

INTRODUCTION

Human intestinal is harbor of many parasites include bacteria, protozoans and helminthes such as Helicobacter pyloric, Shigella spp., Salmonella typhi, Escherichia coli, Campylobacter Giardia lamblia, Entamoeba histolytica, Isospora belli, Blastocystis hominis, Balantidium coli, Dientamoeba fragilis, Ascaris lumbricoides, Strongyloides spp,  Ancylostoma duodenalis , Cryptosporidium spp., Cyclospora cayetanensis etc. Among all of them Cyclospora cayetanensis is an elusive pathogenic coccidian parasite that has gained attention of whole world in 1979. Ashford is credited with having first identified C. cayetanensis as a human pathogen in 1979 in Papua New Guinea. Thereafter, the parasite remained largely uninvestigated until 1994, when the first detailed morphological description and naming of C. cayetanensis was done. So, before 1995, this coccidian parasite was primarily reported as a cause of gastroenteritis among children living in poor sanitary condition and adults from industrialized countries who lived or travelled in developing countries. The first known outbreak of cyclosporiasis in the US occurred in 1990 in a Chicago hospital’s physicians’ dormitory and was attributed to an infected water source. The food borne transmission was first suggested in 1995 when the food prepared in Haitian kitchen was brought in the airplane. In 1996 and 1997, cyclosporiasis outbreaks in North America were linked to eating Guatemalan raspberries.  The first documented outbreak of cyclosporiasis in Nepal occurred in 1989, affecting 55 British expatriates. In Nepal, the investigation is done among school children, people living in slum area, diarrheal and non-diarrheal patients, in health care facilities, sewage and drinking water, vegetables, fruits and stool of different birds and animals. The prevalence of Cyclospora is higher in the summer and early rainy seasons.   At present it is globally distributed in tropical and subtropical regions and an important cause of foodborne outbreaks of enteric disease in many developed countries.    

 MORPHOLOGY AND LIFE CYCLE

Cyclospora cayetanensis is a spherical oocysts that are between 7.5 and 10 μm in diameter that also has a 50-nm-thick wall. It is classified as a coccidian parasite, in the phylum Apicomplexa, family Eimeriidae. All members of Eimeriidae have single-host and fecal-oral cycle. 

The parasite is monogenetic as it complete its lifecycle in epithelial cells and gastrointestinal tract of single host. 

-  When Cyclospora oocysts are first pass in stool, they are not infectious and need to undergo sporulation to become infectious.

-    After some time outside the body (days to weeks) oocysts undergo sporulation at around 220C- 350C and form sporocysts, (containing sporozoites).

-   When a person ingests food and water contaminated by sporocysts than in the GI tract of human, sporozoites are released by rupturing cyst wall of sporocyst and invade the lining of small intestine.

-   In the intestine, sporozoites multiply and developed into meronts. Some meronts stay in the asexual cycle, other undergo sexual reproduction to form zygote.

-  Zygote is then enveloped to form oocysts which are then released from person stool.

LIFE CYCLE OF Cyclospora cayetanensis

Oocyst under microscope

MODE OF INFECTION

Cyclospora cayetanensis is transmitted when the poop or feces of someone having oocysts gets into a water supply. If any other person drink untreated water or eat fruits and vegetables that came in contact with contaminated water then they may be infected by parasite.

 INCUBATION PERIOD

It is 2 days -2 weeks or more

 PATHOGENESIS

The disease cause by Cyclospora cayetanesis is known as cyclosporiasis. It causes acute and chronic diarrhea. The primary symptom of cyclosporiasis is sudden nonbloody, watery diarrhea, with fever, bloating, abdominal cramps, loss of appetite, nausea, anorexia, malaise, fatigue, fever and weight loss.

  In immunocompetent patients, the illness usually resolves spontaneously but can last for months. Relapses may follow improvement in symptoms.

 DIAGNOSIS

• Microscopic examination of stool for oocysts

• Detection of parasite DNA in stool

Diagnosis of cyclosporiasis is by stool tests, either molecular testing for parasite DNA or microscopic examination for oocysts. A modified Ziehl-Neelsen or Kinyoun acid-fast staining technique can help identify Cyclospora. 

 PREVENTIVE MEASURES

·   Washing fruits and vegetables in clean water prior to consumption. 

·   Proper disposal of human excreta.

·   Personal cleanliness and proper sanitation.

·   Avoiding food or water that may have been contaminated with feces.

TREATMENT

•  Antibiotics. Trimethoprim/sulfamethoxazole (TMP/SMX) is a combination of two antibiotics that’s most effective in treating Cyclospora infections. Ciprofloxacin  can be taken instead of sulfa medications in allergy.

• Antidiarrheal medications. diphenoxylate-atropine or loperamide prevent dehydration and prevent loss of important nutrients.

• Hydration. Oral Rehydration Solution to restore electrolytes (minerals that keep your body working properly)