| Abstract|| |
Helminthic contamination of fresh vegetables is common. 116 samples of Coriandrum sativum was processed by Baermann funnel method for recovering Strongyloides stercoralis larvae which were identified by their morphology. The prevalence rate of contamination with larvae was found out. Out of 116 samples, 73 (63%) samples were harboring the parasites and 43 (37%) samples had no larvae. Among 73 positive samples, 25 samples contained rhabdatiform larvae, 12 contained filariform larvae, and 36 contained both types of larvae. 63% prevalence rate of contamination of Coriandrum sativum in Karimnagar is the definite risk factor for acquiring infection by farm workers, handlers, transporters, and consumers of this vegetable. This high prevalence of larvae acts as an environmental source of the parasite; especially the infective filariform forms constituting 65% of the contaminated samples. Larvae can spread from the source through direct contact while handling the vegetable, necessitating estimation of asymptomatically infected persons and burden of the parasitic infestation.
Keywords: Coriandrum sativum , stercoralis larvae, vegetable contamination
|How to cite this article:|
Muniswamappa K, Rao SD, Venkatramana K. Prevalence of Strongyloides stercoralis contaminating Coriandrum obtained from vendors in Karimnagar. Ann Trop Med Public Health 2012;5:298-301
|How to cite this URL:|
Muniswamappa K, Rao SD, Venkatramana K. Prevalence of Strongyloides stercoralis contaminating Coriandrum obtained from vendors in Karimnagar. Ann Trop Med Public Health [serial online] 2012 [cited 2020 Feb 25];5:298-301. Available from: http://www.atmph.org/text.asp?2012/5/4/298/102030
| Introduction|| |
Parasitic infections occupy sixth position in the list of most harmful infective diseases in the world. Strongyloides stercoralis is a ubiquitous parasite having free-living form in soil and can cause chronic infection in humans in tropical and subtropical regions. Raw fresh tender Coriandrum sativum is extensively used in this region in preparing foods, salads, chutney, and other dishes. Contaminated soil and water with human excreta used for irrigation surely increase the likelihood of soil-borne helminthic infections. The study is undertaken to assess the prevalence of Strongyloides stercoralis larvae in Coriandrum sativum, which is posing the risk of infection to humans in the region.
| Materials and Methods|| |
116 samples of Coriandrum sativum were purchased from various vegetable vendors in Karimnagar during the months of April to June 2011. About 50-75 g of the plants were washed especially roots and lower stems in a beaker of 250 ml, containing 100-120 ml of clean water which was kept for sedimentation for an hour. 50-60 ml of the sediment was sieved with a coarse sieve (1-2 mm) to remove roots, leaves, and coarse soil particles, etc. The collected water was filled into Bearmann funnel (12.5 cm dia.) with suitable wire mesh and tissue.  After 12-14 h the water is transferred into 15 ml glass centrifuge tubes, centrifuged at 2500 rpm for 5 min. Discarded the supernatant, the sediment about 1 ml was resuspended with 1 ml of clean water, transferring a drop or two by pipette on to a clean slide was examined under microscope with 10X and 40X for larvae.
| Results|| |
Rhabditiform larvae were identified by their short buccal cavity, length (250-300 μm) and prominent genital primordium [Figure 1].
Filariform larvae with long esophagus, measuring (500-600 μm) in length and notched tail, were identified under microscope [Figure 2], [Figure 3], [Figure 4].
Other larvae, paramecia, protozoa, cysts, and motile bacteria were ignored. Out of 116 samples examined, 73 contained Strongyloides stercoralis larvae. Out of these 73 samples, both the developmental stages were identified in 36 samples, rhabdatiform larvae in 25 samples, and filariform larvae in 12 samples [Figure 5]a and b.
|Figure 5: (a,b) Charts showing total number of samples processed and distribution of various stages of larvae identified|
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63% of prevalence of contamination is very significant as these act as source of infection to humans in the region including animals like dogs which can also be infected. It can also be an indicator of contaminated moist soil along with improper disposal of human waste, possibly unhygienic practices of cultivation. Among the larvae, 60% are infective stages which incline us to suppose that there might be high prevalence of asymptomatic infection in the area especially among farm workers. No studies are available in the area regarding true incidence, prevalence, and asymptomatic infection due to Strongyloides stercoralis infection. Hence, congenial environment, persistent infection in humans, and their excretion of larvae into water and soil need to be studied.
| Discussion|| |
Strongyloidiasis is estimated to affect 100-200 million people worldwide in 70 countries.  Strongyloides stercoralis is a geohelminth having free-living life cycle in warm humid soil. Prevalence of strongyloidiasis is underestimated. It is most prevalent in South-East Asia, Africa, and Middle East. Occur in mental institutions, prisons, and military personnel. Global prevalence rate is as high as 40%.
Strongyloides stercoralis is a geohelminth having free-living life cycle in warm humid soil. The filariform larvae are infective by penetrating skin of humans who walk barefoot in the larval contaminated soil.  The soils of vegetable gardens also harbor helminthic parasites as it is contaminated with human excreta, especially in places where it is used as manure. A study conducted at rural area Kaula Lipis showed 7.1% soil contamination.  In our study, most of the Coriandrum sativum purchased for study had soil particles sticking to roots. Further studies are required to assess the magnitude of soil contamination with geohelminths in the places where the samples are grown. In addition, factors like temperature, humidity, microflora, access of water to animals, and agricultural practices should be investigated in the large scale to determine the particular factors responsible for high prevalence rate. 
In our present study, the prevalence of contamination is 63% (73 out of 116). Among the positive samples, 36 had both the types of larvae, 25 have rhabdatiform larvae, and 12 have filariform 12, which is very significant. High prevalence is related to tropical environment. The samples were collected in the months of summer (April-June) from various venders. High prevalence of larvae is a potential source of infection to humans. Since coriander plant cannot be kept for long before it is used, the larvae remain viable on the vegetable. Gardens, vegetable markets, and road-side shops are the places of potential infection. All age groups are at risk especially immunodeficient. The prevalence of contamination of vegetables varies in different parts of the world 15-82% in Brazil, 1.1-16.5% in Costa Rico, 26% in Zair, and 48% in Central African Republic. A study at Gada Biu market recorded higher prevalence of vegetable contamination of 60%. Prevalence also varies according to the season.
Coriander should be kept moist after recovering the plant entirely, including roots, from the soil by repeated sprinkling of water in hot weather after wrapping it with cloth or gunny bad to prevent it from drying. The process of keeping moisture with unhygienic wrapper and contaminated water provide moisture for the larvae to survive on Coriandrum sativum.
In some places 83% of raw water used for irrigation of the soil where vegetables are grown is contaminated grossly by the intestinal helminthic parasites. 
Asymptomatic infection in man is very common with Strongyloides stercoralis in endemic areas, who serve as source of infectious larvae. They persist for many years by repeated internal reinfection. Symptoms are confined to skin manifestations like raised erythematous lesions on buttocks and gastrointestinal symptoms like mild diarrhea, epigastric pain mild colitis occasional malabsorbtion. Eosinophila is common. Pulmonary symptoms are very rare in uncomplicated asymptomatic strongyloidiasis.
Strongyloides stercoralis is the only helminthic parasite which multiplies in the host. Risk factors such as immunocompromised state, long-term corticosteroid therapy hematologic malignancy lead to autoinfection, hyperinfection syndrome.  In persons where there is deficient immune response as result of HIV infection with low CD4 count of 50 cells/cu.mm, tuberculosis, treatment with antimalignant drugs, corticosteroids, chronic alcoholism, and uncontrolled diabetes mellitus, the larvae can directly enter into circulation and spread to various organs. Entering into lungs, central nervous system, peritoneum, liver, and kidney they cause pneumonia, meningoencephalitis, peritonitis enteritis, and death in HIV infected.  During penetration the larvae also carry bacteria causing gram-negative septicemia. Treatment with glucororticoids in disseminated infection is often fatal. These people excrete large number of larvae into the environment. Rhabdatiform larvae develop into filariform larvae or differentiated into sexual forms that are free living in the soil. Rhabdatiform larvae can survive in the favorable soil.
One more surprising fact is that the prevalence of the parasite would have been more if sensitive method such as agar culture technique were used.  Hence, population should be screened for asymptomatic infection.
To take preventive measures to decrease the impact of the disease in risk groups in an area, both stool examination and serological studies should be done.
| Conclusion|| |
Infective forms of larvae of Strongyloides stercoralis is found on Coriandrum sativum, though the prevalence of which may vary according to the season of the year, place and conditions of the soil, and endemicity. Prevalence of larvae on vegetables is the determinant of risk of infection to human beings particularly the risk groups mentioned. Hence, it is proposed to screen the population for infection with the parasite and administer treatment to prevent complications of hyperinfection syndrome. Environmental sanitation personal hygiene improvement in agricultural practices should be taken care by creating awareness in the community including handling, transport, and consumption of Coriandrum sativum.
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Department of Microbiology, Prathima Institute of Medical Sciences, Nagunoor, Karimnagar, Andra Pradesh
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]