Food Parasitology

Cyclospora

Cyclospora cayetanensis is a protozoan parasite that causes intestinal infections called cyclosporiasis. Outbreaks of this desease have been frequently associated with consumption of contaminated fresh fruits, primarily of the berries family, and contaminated drinking water. Countries in the tropical or subtropical regions of the world are endemic for cyclospora and therefore people in those countries are at higher risks for infections with this parasite. In the US, food borne outbreaks of cyclosporiasis have been linked to various types of imported fresh produce.

Cyclospora affects the small intestine and the main symptoms of the disease of watery diarrhea. Acute infection is characterized by intermittent episodes of explosive, watery diarrhea with mild fever and muscular pain. The disease can last few days to several weeks. In some in stances, people become infected but do not develop symptoms.

Transmission

Cyclospora cayetanensis is transmitted via the fecal-oral route, although Cyclospora is not passed directly from one person to another. Infected people serve as the source of contamination of the environment or the food that then become the source of contamination to others. Transmission of cyclosporiasis may be facilitated by eating food or drinking water contaminated with infectious oocysts persisting freely in the environment after being shed in human stools.

Identification

clyclospora

Figure 1: Cyclospora spp. oocyst (DIC Microscopy 100X)

IEH Laboratories offer diagnostic services for Cyclospora cayetanensis based on different platforms. Direct microscopic identification using the acid-fast staining technique and differential interface contrast microscopy (DIC) aided by the detection of autofluorescence. The bases for these method is the observation of the oocysts in the food sample. Cyclospora oocysts are autofluorescent. Therefore, the direct observation of a food sample under an ultraviolet fluorescence microscope allows for the detection of the oocysts, which appear blue or green against a black background. Molecular diagnostic methods, such as polymerase chain reaction (PCR) analysis, are also used to detect the DNA of this parasite in the sample. ELISA and PCR-based assays are the most efficient fast tests used at IEH for detecting contamination with Cyclospora cayetanensis oocysts. The sporulation assay is also available for confirming the presence of characteristic sporocysts and sporozoites.

Cryptosporidium

The parasites of the Cryptosporidium genus are responsible for waterborne or foodborne cryptosporidiosis, which is an important disease in the US. Cryptosporidium spp. are widely distributed in the environment. There are more than 15 species of Cryptosporidium, but five species have been the main ones associated to human infections: C. hominis, C. parvum, C. meleagridis, C. canis and C. felis. In the case of C. parvum, C. canis and C. felis, humans are minor or secondary hosts. Cryptosporidiosis is a disease characterized for acute or chronic episodes of projectile watery diarrhea and abdominal cramps. Human cryptosporidiosis may be a life threatening disease for immunocompromised individuals, young children and the elderly.

Identification

Cryptosporidium

Figure 1: Cryptosporidium spp. oocysts (DIC Microscopy 100X)

IEH Laboratories offer diagnostic services for Cryptosporidium based on direct microscopic identification using differential interface contrast microscopy (DIC) aided by immunofluorescent antibody test (USEPA Method 1622 and USEPA Method.1623). PCR-based assays are used at IEH for detecting Cryptosporidium oocysts. DNA sequencing assays are performed for Cryptosporidium oocysts speciation. The evaluation of the viability of Cryptosporidium oocysts is offered via the in vitro excystation assay and in vitro cell cultures. The excystation process is when the sporozoites, which are the infective form of the parasite, are released from the oocysts after the ingestion by the host.

  • July 8th, 2013
  • Posted in
  • No Comments