Infection of Cyclospora cayetanensis in Diarrhoeal Children of Nepal

Introduction: Cyclospora cayetanensis is a coccidian parasite that causes recurrent gastroenteritis among children living under poor sanitary condition and adults from industrialized countries who lived or traveled in endemic developing countries. Methods: A total of 1842 stool specimens from gastroenteritis patients were examined between March 2006 to February 2007 and collected various types of faecal specimens from human, animals and samples of water and green leafy vegetables. Results: Of 1842 stool specimens collected from different areas of Nepal, 146 (7.9 %) were found to be positive for Cyclospora cayetanensis. with the majority were from children 2-9 years of age. The highest rate of infections was found in the month of June; (31.6%). Cyclospora cayetanensis were found to be contaminated in green vegetables including leaves of basil, mint leaves, water sources and feces of domestic animals and these findings were presented in the paper. Conclusion: Cyclospora-like oocysts were detected in vegetables leaves, feces of domestic animals and water sources. The results suggest that water, vegetables and domestic animals are possible sources of infection in Nepal. The study also obtained more information on Cyclospora cayetanensis a coccidian parasite that infect humans especially children and causes prolonged diarrhea and life threatening infestation.


Introduction
C yclospora cayetanensis has emerged as an important cause of acute and chronic gastroenteritis worldwide 1,2,3 .The organism was fi rst described by Ashford in 1979 4 , and recently it was categorized as an important gastrointestinal parasite.Cyclospora infection has been reported from Papua New Guinea, Indonesia, India, Pakistan, Nepal, the Middle East, North Africa, South Africa, the United Kingdom, the Caribbean, the United States of America, Central America, and South America 5,6,7,8,9,10,11 .
Although C. cayetanensis is reported from all areas of the world, little is known about the biology of the organism and the means of transmission remains an enigma.Susceptible humans are suspected to be infected by ingesting sporulated oocysts.Water is probably an important vehicle, either drinking parasite contaminated water directly or indirectly when water is used to grow plant foods.Water has been implicated in outbreaks in the United States, and in Nepal 12,11,13 .Food borne transmission is also suspected with reports of fi nding oocysts in washing of leafy vegetables in Peru and Nepal 14,15 .Patients suffer from a chronic watery diarrhea, fatigue, nausea, vomiting, abdominal cramps, anorexia, weight loss and myalgia.However, it is not known what is responsible for the pathogenesis.In previous study of Sherchand and Cross between 2001 and 2004 in Nepal, they have identifi ed some possible sources of infection with Cyclospora 15,17,18 .
To obtain more evidence, the present studies were carried out from March 2006 to February 2007 in order to determine the prevalence and distribution of Cyclosporiasis from different areas of Nepal.Further study on animals' feces, water, and green leafy vegetables were collected and examined.The study was also conducted to investigate source of infection.

Materials and Methods
A total of 1842 stools samples were collected from different areas of Nepal and examined in Tribhuvan University Institute of Medicine, Public Health Research Laboratory.The collected stool samples were examined soon after the passage by direct light microscopy at 400x and stools were also preserved in 2.5% potassium dichromate solution for further study.During the study period, the patients were asked to respond questionnaires to record their age, sex, educational status, occupation, clinical history including duration of illness, current diarrhoeal status, demographic and food habit of family either vegetarian or non vegetarian.
Samples of water and green leafy vegetable: During sampling collection in the different districts, samples from irrigation canal, pond water, public drinking water of different sources and green-leafy vegetables were collected to determine the contamination of Cyclospora oocyst and to investigate the possible sources of infection.The leaves were washed in distilled water, the washings and the samples of water were centrifuged and the sediments were examined microscopically.The excess amounts of sediments were resuspended in 2.5 % potassium dichromate solution, and the recovery of sporulation was noted.Cyclospora study in various animals: Studies of 320 stools were examined for Cyclospora oocysts from chicken, pigs, monkeys, dogs, cats, goats, cows, buffaloes.
Microscopic examination and standard staining application: Direct microscopic examination after concentration with formalin-ether and sucrose solution, phase contrast microscopy was performed.All the positive samples from human and animals faeces as well as sewage and green leafy vegetables were further confi rmed by following modifi ed acid fast staining method: The samples were heat fi xed and stained with carbolfuchsin (Sigma, St. Louis) for 30 minutes.Samples were decolorized for 1 minute with a 1 % solution of HCl in 75 % ethanol.C. cayetanensis oocysts were identifi ed with their characteristic size (8-10 um), round shape and red coloration.Other protozoa and helminthes eggs were also recorded.

Results
Cyclospora cayetanensis in different areas: Of 1842 stool specimens collected from different areas, 146 (7.9 %) were found to be positive for Cyclospora cayetanensis.

Gender and Age-wise distribution
Out of 1842 people, 846 were males and 996 were females ranging from 2 years to 70 years of age were examined.Of total 146 positive patients, 68 (46.6%) were male and 78 (53.4%) were female.The highest prevalence of C. cayetanensis infection 74 (50.7 %) was found between 2 and 5 years of age group where as the lowest prevalence 6 (4.1%) were above 28 years of age (Fig 1).

Occupation-wise distribution of Cyclospora infection
The study samples were collected from different occupational groups: Farmer 658, Business people 106, Service holder 102, children/ students 909 and other such as unemployed people 67.The distributions of Cyclospora infection in these groups are shown in Fig 2 .The highest infection rate was found among children/student (dependent group) (65%) and lowest (2%) among business people (P< 0.05).

Education and Cyclospora infection
The highest rate of cyclospora infection was found among children age group between children who were studying in class 1 to 5 (41.7%) compared to other group of people (P<0.05) as shown in Fig 3.

Distribution of one or more mixed parasites in Cyclosporiasis patients
A total of 146 Cyclospora infected patients 34 (23.2) had one or more mixed intestinal parasites.The highest mixed parasitic infection was due to Giardia lamblia (24.7%) and the lowest was due to Isospora belli (1.2%).There was no difference in the distribution of coinfecting parasites between patients with diarrhea and non diarrhea (P= > 0.05).

Month-wise distribution of Cyclospora cayetanensis infection
The higher distribution of Cyclospora infection in Nepal is during summer and rainy season-June and July as shown in Figure 4.The prevalence decreased during the winter, although there are few cases were identifi ed in early winter in October.

Examination of Vegetables
Green vegetables collected from different areas and vegetable markets consisted of cabbage, lettuce, caulifl ower, spinach, green onions, mint, basil, radishes, green leafy vegetables, mustard leaves and carrot, in which lettuce, spinach, mustard and basil leaves were found to be contaminated with Cyclospora (Fig 5).Cyclospora were further confi rmed by the development of two sporocysts, after two weeks incubation period in potassium dichromate solution.

Examination of water samples
Water samples were collected from different areas and studied for Cyclospora as shown in Figure 6.Cyclospora contamination was found in June, July in irrigation canal and Pond water.Several other parasites: Giardia lamblia, amoeba, unidentifi ed trophozoites, ova of Ascaris, larvae of helminthes and many small insects, worms were detected.In 2 sources of water samples (Pond, and irrigation canal) Cryptosporidium parvum oocysts were also identifi ed.

Examination of stool samples from different animals
Of total 327 different animal samples examined, 3 animals were found to be positive for Cyclospora oocysts.Among these animals, one chicken (1.7%), 2 monkeys (6.5%), and 2 dogs (3.8%) were found positive as shown in Fig 7.

Discussions
The current study presented to explain upgrade information on Cyclospora cayetanensis a coccidian parasite that infect humans and causes prolonged diarrhoea in both immunocompetent and immunocompromised hosts.The mechanisms of pathogenesis and virulence factors of Cyclospora cayetanensis are yet to be defi ned, but tissue damage and jujunitis have been reported 14 .The present study advances our understanding both of the epidemiology of Cyclospora cayetanensis in Nepal where there are repeated outbreaks of the emerging diseases associated with gastroenteritis.Although Cyclospora infection has been reported from all parts of the world, most of the epidemiological information comes from studies in Nepal, Haiti, Peru and United States, where it is endemic 11,13,18,19,20,21 .Cyclosporiasis appears to be seasonal, with peak incidence during the rainy seasons from April to June in Peru and May to September in Nepal 1,3,16,18 .Although all age groups can acquire the disease, the highest attack rates occur among children older than 18 months 19,22 , where as in our study the highest attack rates was found among children age between 2 to 5 years.There is no apparent immunity to infection, and reinfection can occur at all ages 23,24 .
In the United States, the outbreak of diarrheal disease associated with Cyclospora in 21 medical residents in 1990 was epidemiologically linked to a contaminated water supply 11,12,13 .Subsequently, more than 1000 confi rmed cases in the US and Canada were reported 26 .In this study oocysts of Cyclospora were found in irrigation canal and pond water in June, July during the high transmission period.Cyclospora infection occurs most commonly via contaminated water 12,25 and the oocysts are resistant to chlorination and not readily detected by methods that are currently used to assure the safety of drinking water.Though Cyclospora has been detected in water samples, however, the available method for detection in water has very low sensitivity 25 .Contaminated food has long been proposed as a possible route for transmission of Cyclospora 23 .Vegetables in particular are suspicious since they are often ingested raw or undercooked.Vegetables are easily contaminated and provide organisms with an optimal environment for survival prior to host ingestion.It is believed that Cyclospora, must sporulate for at least 7-10 days in the environment to be infectious.Fertilization of plants with human waste or indirectly via contaminated water used for crop irrigation and to freshen produce could lead to contamination of vegetables with Cyclospora.Findings on vegetable studies have shown that lettuce, spinach, mustard and basil leaves were contaminated with Cyclospora which confi rmed that food-borne transmission is feasible.It still remains to be determined if recovered oocysts are infectious.The source of vegetable contamination with oocysts is still unknown, but it may be due to fecally contaminated water used on the vegetables from the irrigation water or directly from contaminated hands of food handlers.Moreover, in Nepal, vegetables coming in the markets are dipped and rinsed into highly contaminated water of small ponds or rivers in order to wash and clean it, but actually it becomes too contaminated once again.There are thousands of such instances of how food is rendered unsafe due to unhygienic conditions, handling and practices and poor environment.In cities of Nepal, the water supply is contaminated through seepage into water pipes from sewage.In rural areas, the source of water itself (wells, ponds, rivers etc) is polluted from the contact of waste disposal deposits.One of the common food contamination problems is again from insects and rodents and as a result food becomes unfi t for human consumption.
Although more studies are needed to clarify the direct link between Cyclospora infection and these sources, the results suggests that green leafy vegetables, water from sewage and irrigation canal are possible sources of infection in Nepal 18,20 .To obtain more evidence on the source of infection, specimens from rodents, birds, insects and domestic animals are need for extensive study.Wider dissemination of skilled laboratory diagnosis is a prerequisite for a better understanding of the epidemiology of this infection and its association with disease.The frequency of malabsorption in clinical illness needs to be established.Detail histopathological and electron microscopical studies on biopsy material should be done to understand the life cycle and pathogenesis of the Cyclospora.In vitro cultivation system for drug screening and controlled trials of drug therapy are needed.Better knowledge of the behavior of Cyclospora in AIDS patients along with other coccidia, Cryptosporidium, Isospora and Toxoplasma need to be studied in the context of Nepal.In addition, we need to identify alternative effi cacious agents for therapy as well as prophylaxis and to develop inexpensive, reliable molecular and diagnostic tools.

Conclusion
The study obtained more information on Cyclospora cayetanensis a coccidian parasite that infect humans especially children and causes prolonged diarrhea and ultimately life threatening infestation.Current fi ndings of Oocysts of Cyclospora in vegetables leaves, feces of domestic animals and water sources suggests that water, vegetables and domestic animals are possible sources of infection, however, more studies are needed