Detection of Giardia, Entamoeba, and Cryptosporidium in unprocessed food items from northern India

Abstract

This study was conducted to evaluate the load of three food- and water-borne parasites, namely, Giardia, Entamoeba, and Cryptosporidium on food items that are consumed either raw or in an unprocessed state in the northern parts of India. A two-step diagnostic method was employed to assess the presence of Giardia and Cryptosporidium, the immunofluorescence assay (IFA) combined with the polymerase chain reactiion (PCR assay), whereas a Tech lab diagnostic kit in combination with PCR assay was used for accurate detection of Entamoeba histolytica in the samples. The methods for isolation and enrichment of cysts/oocysts from the various food items were tested and discussed here. Our results showed that the overall spectrum of incidence of the three parasites on food items in decreasing order were Giardia > Entamoeba > Cryptosporidium. When data were subjected to the chi-square test, the prevalence of all three parasites was found to be independent of the food items. To determine whether the presence of two types of parasites in a food item is uniform, a Poisson distribution test was conducted. On comparing the intensity of occurrence of the different parasites in various food items, it was observed that the occurrence of Giardia and Entamoeba was not of the same order at 5% level of significance only in case of samples of raw meat and milk. This confirmed that a high number of raw or unpasteurized milk and meat samples are more likely to be contaminated with Giardia than with Entamoeba. Therefore, our observations point to the unhygienic practices of food handlers being a major contributor in the transmission of parasites to unprocessed food products.

Annexure 1: Statistical analysis

Incidence rates of parasites in food items

Note: Expected values are in boxes within each cell of observation. The values outside the boxes are the observed values.

$$ \chi^{2} = \sum\limits_{i} {\frac{{\left( {O_{i} - E_{i} } \right)^{2} }}{{E_{i} }}} = 4.76 $$

Tabulated $\chi^{2}$ = 9.488 at α = 0.05 for 4 degrees of freedom

Rate of incidence of two parasites in a specific food item

Raw vegetable leaves

• (a) Giardia (N ₁) = 12 and Entamoeba (N ₂) = 8

  $$ F = \frac{{N_{1} }}{{N_{2} + 1}} = \frac{12}{8 + 1} = 1.33 $$

  Tabulated F_18,24 = 2.18 at α = 0.05

• (b) Cryptosporidium (N ₁) = 1 and Giardia (N ₂) = 12

  $$ F = \frac{{N_{1} }}{{N_{2} + 1}} = \frac{1}{12 + 1} = 0.076 $$

  Tabulated F_26,2 = 1.98 at α = 0.05

• (c) Cryptosporidium (N ₁) = 1 and Entamoeba (N ₂) = 8

  $$ F = \frac{{N_{1} }}{{N_{2} + 1}} = \frac{1}{8 + 1} = 0.11 $$

  Tabulated F_18,2 = 19.45 at α = 0.05

Meat samples

• (a) Giardia (N ₁) = 13 and Entamoeba (N ₂) = 7

  $$ F = \frac{{N_{1} }}{{N_{2} + 1}} = \frac{13}{7 + 1} = 1.63 $$

  Tabulated F_16,26 = 1.67 at α = 0.05

• (b) Cryptosporidium (N ₁) = 3 and Giardia (N ₂) = 13

  $$ F = \frac{{N_{1} }}{{N_{2} + 1}} = \frac{3}{13 + 1} = 0.214 $$

  Tabulated F_28,6 = 4.0 at α = 0.05

• (c) Cryptosporidium (N ₁) = 3 and Entamoeba (N ₂) = 7

  $$ F = \frac{{N_{1} }}{{N_{2} + 1}} = \frac{3}{7 + 1} = 0.37 $$

  Tabulated F_16,6 = 4.0 at α = 0.05

Milk samples

• (a) Giardia (N ₁) = 16 and Entamoeba (N ₂) = 7

  $$ F = \frac{{N_{1} }}{{N_{2} + 1}} = \frac{16}{7 + 1} = 2.0 $$

  Tabulated F_16,32 = 1.98 at α = 0.05