Cyclospora cayetanensis

Cyclosporiasis Microchapters
Home
Patient Information
Overview
Historical Perspective
Classification
Pathophysiology
Causes
Differentiating Cyclosporiasis from other Diseases
Epidemiology and Demographics
Risk Factors
Screening
Natural History, Complications and Prognosis
Diagnosis
History and Symptoms
Physical Examination
Laboratory Findings
Electrocardiogram
Chest X-Ray
CT Scan
MRI
Ultrasound
Treatment
Medical Therapy
Primary Prevention
Case Studies
Case #1
Cyclospora cayetanensis On the Web
Most recent articles
Most cited articles
Review articles
CME Programs
slides
Images
American Roentgen Ray Society Images of Cyclospora cayetanensis All Images X-rays Echo & Ultrasound CT Images MRI
Ongoing Trials at Clinical Trials.gov
US National Guidelines Clearinghouse
NICE Guidance
FDA on Cyclospora cayetanensis
on Cyclospora cayetanensis
Cyclospora cayetanensis in the news
Blogs on Cyclospora cayetanensis
Directions to Hospitals Treating Cyclosporiasis
Risk calculators and risk factors for Cyclospora cayetanensis

This page is about microbiologic aspects of the organism(s).  For clinical aspects of the disease, see Cyclosporiasis.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]

Overview

Cyclospora cayetanensis is a protozoan that causes disease in humans, and possibly in other primates. It has also been isolated from the feces of other animals such as ducks and chickens. Due to the spherical shape of C. cayetanensis sporocytes, it was placed in the Cyclospora genus. It has a double layered wall that gives it resistance against disinfectants and adhesins which are responsible for its adherence characteristics. The bacteria show tropism for epithelial cells of the small intestine, especially of the duodenum and jejunum.

Taxonomy

Three uniformly stained Cyclospora cayetanensisoocysts in the field of view. Image provided by the CDC Centers for Disease Control and Prevention

Photomicrograph of a fresh stool sample, which had been prepared using a 10% formalin solution, and stained with modified acid-fast stain, revealed the presence of four Cyclospora cayetanensis oocysts in the field of view Image provided by the CDC Centers for Disease Control and Prevention

Eukaryota; Alveolata; Apicomplexa; Conoidasida; Coccidia; Eucoccidiorida; Eimeriorina; Eimeriidae; Cyclospora

Biology

Cyclospora cayetanensis is an obligate intracellular apicomplexan, cyst-forming coccidian protozoan, of the family of Eimeriidae, which commonly causes self-limiting diarrhea. Morphologically C. cayetanensis has spherical oocysts that are between 7.5 and 10 micrometers in diameter that also have a 50 nanometer thick bilayered wall with an outer threadlike coat that has been called a wrinkle by some researchers.

According to a phylogenetic analysis performed with the 18S rRNA gene, in the Cyclospora species isolated from a group of baboons, this species, although different, was proved to be similar to the C. cayetanensis that infects humans. These two species were then documented was belonging to the same clade of the Eimeria species. Other three species of Cyclospora were also identified in non-human primates and characterized with the SSU rRNA analysis, later that year. Because there are morphologically similar, there can not be differentiated by light microscopy. These species: C. cercopitheci, C. colobi and C. papionis were identified in green monkeys, colobus monkeys, and baboons, respectively. C. cayetanensis and these three other species of Cyclospora all share the characteristic of being host-specific.

It is not known the exact conditions and location required for the sporulation of oocysts in the natural environment, however, these data would help to understand and predict the distribution and seasonality of C. cayetanensis. Due to its double-layered wall it is highly resistant, particularly to disinfectants used during food processing. This resistance along with its binding affinity to certain produce, explains the risks associated with contaminated foods. The adhesive properties of C. cayetanensis are stronger than those of the oocysts of Giardia or Cryptosporidium, however, the responsible adhesins are yet to be identified.

Tropism

Cyclospora cayetanensis shows tropism for epithelial cells of the small intestine, especially for the jejunum.

Natural Reservoir

C. cayetanensis is an host specific parasite that is able to infect humans. Cyclospora oocysts have also been isolated from the feces of several animals, such as ducks, chickens and dogs. Attempts to identify and to infect different animals with C. cayetanensis have failed. Certain shellfish may acquire C. cayetanensis from contaminated waters, and concentrate its oocyst for several days.

Differential diagnosis

Cyclospora cayetanensis infection must be differentiated from other causes of viral, bacterial, and parasitic gastroentritis.

Organism			Age predilection	Travel History	Incubation Size (cell)	Incubation Time	History and Symptoms			Diarrhea type8				Food source	Specific consideration
							Fever	N/V	Cramping Abd Pain	Small Bowel	Large Bowel	Inflammatory	Non-inflammatory
Viral	Rotavirus		<2 y	-	<102	<48 h	+	+	-	+			+	-	Mostly in day cares, most common in winter.
	Norovirus		Any age	-	10 -103	24-48 h	+	+	+	+			+	-	Most common cause of gastroenteritis, abdominal tenderness,
	Adenovirus		<2 y	-	105 -106	8-10 d	+	+	+	+			+	-	No seasonality
	Astrovirus		<5 y	-		72-96 h	+	+	+	+			+	Seafood	Mostly during winter
Bacterial	Escherichia coli	ETEC	Any age	+	108 -1010	24 h	-	+	+	+			+	-	Causes travelers diarrhea, contains heat-labile toxins (LT) and heat-stable toxins (ST)
		EPEC	<1 y	-	10†	6-12 h	-	+	+	+			+	Raw beef and chicken	-
		EIEC	Any ages	-	10†	24 h	+	+	+		+		+	Hamburger meat and unpasteurized milk	Similar to shigellosis, can cause bloody diarrhea
		EHEC	Any ages	-	10	3-4 d	-	+	+		+	+		Undercooked or raw hamburger (ground beef)	Known as E. coli O157:H7, can cause HUS/TTP.
		EAEC	Any ages	+	1010	8-18 h	-	-	+		+		+	-	May cause prolonged or persistent diarrhea in children
	Salmonella sp.		Any ages	+	1	6 to 72 h	+	+	+		+	+		Meats, poultry, eggs, milk and dairy products, fish, shrimp, spices, yeast, coconut, sauces, freshly prepared salad.	Can cause salmonellosis or typhoid fever.
	Shigella sp.		Any ages	-	10 - 200	8-48 h	+	+	+		+	+		Raw foods, for example, lettuce, salads (potato, tuna, shrimp, macaroni, and chicken)	Some strains produce enterotoxin and Shiga toxin similar to those produced by E. coli O157:H7
	Campylobacter sp.		<5 y, 15-29 y	-	104	2-5 d	+	+	+		+	+		Undercooked poultry products, unpasteurized milk and cheeses made from unpasteurized milk, vegetables, seafood and contaminated water.	May cause bacteremia, Guillain-Barré syndrome (GBS), hemolytic uremic syndrome (HUS) and recurrent colitis
	Yersinia enterocolitica		<10 y	-	104 -106	1-11 d	+	+	+		+	+		Meats (pork, beef, lamb, etc.), oysters, fish, crabs, and raw milk.	May cause reactive arthritis; glomerulonephritis; endocarditis; erythema nodosum. can mimic appendicitis and mesenteric lymphadenitis.
	Clostridium perfringens		Any ages		> 106	16 h	-	-	+		+		+	Meats (especially beef and poultry), meat-containing products (e.g., gravies and stews), and Mexican foods.	Can survive high heat,
	Vibrio cholerae		Any ages	-	106-1010	24-48 h	-	+	+	+			+	Seafoods, including molluscan shellfish (oysters, mussels, and clams), crab, lobster, shrimp, squid, and finfish.	Hypotension, tachycardia, decreased skin turgor. Rice-water stools
Parasites	Protozoa	Giardia lamblia	2-5 y	+	1 cyst	1-2 we	-	-	+	+			+	Contaminated water	May cause malabsorption syndrome and severe weight loss
		Entamoeba histolytica	4-11 y	+	<10 cysts	2-4 we	-	+	+		+	+		Contaminated water and raw foods	May cause intestinal amebiasis and amebic liver abscess
		Cryptosporidium parvum	Any ages	-	10-100 oocysts	7-10 d	+	+	+	+			+	Juices and milk	May cause copious diarrhea and dehydration in patients with AIDS especially with 180 > CD4
		Cyclospora cayetanensis	Any ages	+	10-100 oocysts	7-10 d	-	+	+	+			+	Fresh produce, such as raspberries, basil, and several varieties of lettuce.	More common in rainy areas
	Helminths	Trichinella spp	Any ages	-	Two viable larvae (male and female)	1-4 we	-	+	+		+		+	Undercooked meats	More common in hunters or people who eat traditionally uncooked meats
		Taenia spp	Any ages	-	1 larva or egg	2-4 m	-	+	+	+			+	Undercooked beef and pork	Neurocysticercosis: Cysts located in the brain may be asymptomatic or seizures, increased intracranial pressure, headache.
		Diphyllobothrium latum	Any ages	-	1 larva	15 d	-	-	-	+			+	Raw or undercooked fish.	May cause vitamin B12 deficiency

8Small bowel diarrhea: watery, voluminous with less than 5 WBC/high power field

Large bowel diarrhea: Mucousy and/or bloody with less volume and more than 10 WBC/high power field
† It could be as high as 1000 based on patient's immunity system.

The table below summarizes the findings that differentiate inflammatory causes of chronic diarrhea

Cause	History	Laboratory findings	Diagnosis	Treatment
Diverticulitis	Bloody diarrhea Left lower quadrant abdominal pain Abdominal tenderness on physical examination Low grade fever	Leukocytosis Elevated serum amylase and lipase Sterile pyuria on urinalysis	Abdominal CT scan with oral and intravenous (IV) contrast	bowel rest, IV fluid resuscitation, and broad-spectrum antimicrobial therapy which covers anaerobic bacteria and gram-negative rods
Ulcerative colitis	Diarrhea mixed with blood and mucus, of gradual onset. Signs of weight loss Rectal urgency Tenesmus Blood is often noticed on underwear Different degrees of abdominal pain	Anemia Thrombocytosis A high platelet count Elevated ESR (>30mm/hr) Low albumin	Endoscopy	Induction of remission with mesalamine and corticosteroids followed by the administration of sulfasalazine and 6-Mercaptopurine depending on the severity of the disease.
Entamoeba histolytica	Abdominal cramps Diarrhea Passage of 3 - 8 semiformed stools per day Passage of soft stools with mucus and occasional blood Fatigue Intestinal gas (excessive flatus) Rectal pain while having a bowel movement (tenesmus) Unintentional weight loss	cysts shed with the stool	detects ameba DNA in feces	Amebic dysentery Metronidazole 500-750mg three times a day for 5-10 days Tinidazole 2g once a day for 3 days is an alternative to metronidazole Luminal amebicides for E. histolytica in the colon: Paromomycin 500mg three times a day for 10 days Diloxanide furoate 500mg three times a day for 10 days Iodoquinol 650mg three times a day for 20 days For amebic liver abscess: Metronidazole 400mg three times a day for 10 days Tinidazole 2g once a day for 6 days is an alternative to metronidazole Diloxanide furoate 500mg three times a day for 10 days must always be given afterwards.