Protozoa of significance in food

Fruits and vegetables can become contaminated with free living Protozoa through contact direct with soil, irrigation water, air, rain, insects, and during industrial produce‐washing.

Amoebae have been recovered from mushrooms and vegetables such as carrots, cauliflower, lettuce, radishes, scallions, spinach, and tomatoes.

Flagellates were found on spinach, Romaine lettuce, and butterhead lettuce.

Ciliates were recovered from mushroom surfaces.

The number of Protozoa on leafy vegetables can be high, with flagellates being more abundant than amoebae and ciliates.

Washing or rinsing lettuce leaves followed by spin‐drying in a household salad spinner reduced the protozoan number only by a maximum 1 log unit (90%).

Protozoa have also been recovered from ready‐to‐eat lettuce, which suggests that they are able to survive mild treatments such as industrial washing.

The following table summarises research conducted over many years into the various species of Protozoa found on particular vegetables – this can be useful when undertaking a HACCP hazard analysis.

VegetablesMorphogroupIdentified speciesReference
Lettuce, scallions, radishesAmoebaeArhysodesApalestinensisNaegleria gruberiCiurea‐Van Saanen (1981)
Mushrooms (Agaricus bisporus)AmoebaeAcanthamoeba spp., Hartmannella spp., Vannella spp.Napolitano (1982)
CiliatesColpoda sp., holotrichs, hypotrichs
Oak leaf lettuce, Boston lettuceAmoebaeAcanthamoeba spp., Hartmannella spp.Napolitano and Colletti‐Eggolt (1984)
Carrots, radishes, tomatoes, mushrooms, cauliflowers, spinachAmoebaeApolyphagaArhysodesAcastellaniiRude and others (1984)
CarrotsAmoebaeAculbertsoniArhysodesHvermiformisSharma and others (2004)
Romaine lettuceAmoebaeA. palestinensisGourabathini and others (2008)
CiliateGlaucoma sp.
SpinachCiliateC. steinii
Butterhead lettuceAmoebaeCochliopodium sp., Mayorella vespertiloidesRipella platyopodiaRipella platyopodiaVannella simplexH. vermiformisSaccamoeba sp., Vahlkampfia sp.Vaerewijck and others (2011)
FlagellatesGoniomonas truncataBodo saltansBodo sp., Cercomonas spp., Notosolenus sp., Peranema trichophorumPetalomonas sp., Rhynchomonas nasutaAllantion tachyploonSpumella spp.
CiliatesAspidisca lynceusCinetochilum margaritaceumChilodonella uncinataC. steiniiColpoda sp., Cyclidium glaucomaGlaucoma scintillansGlaucoma sp., Paramecium putriniumPlatyophrya sp., Tachysoma pellionellumTrachelophyllum sp., Vorticella convallaria complex, Vorticella sp.
Ready‐to‐eat lettuce (butterhead lettuce)FlagellatesBodo saltansCercomonas spp., Spumella cylindricaSpumella‐like flagellatesVaerewijck and others (2011)
CiliateC. steinii

The prevalence of Protozoa in meat and fish has not been established through research: however, it is reasonable to accept that if good hygiene practices are not followed, there can be cross contamination during processing.

The most significant Protozoa for causing illness in humans are Giardia and Cryptospiridia. Both can cause significant illness, especially in children.