Cyclospora species are found in humans, insectivores and other animals; however Cyclospora cayetanensis is the only species of this genus found to infect humans.
The oocyst of Cyclospora cayetanensis are spherical in shape and are up to twice the size of Cryptosporidium oocyst, at 7.5 – 10um in diameter. The oocyst is surrounded by a 50nm thick wall and outer fibrillar (63nm) coat that contains complex carbohydrates and lipids which make the oocyst acid fast. Within the oocyst are two long oblong sporocyst that in turn contain two infectious sporozoites. Once ingested by the host, the oocyst excyst in the gastrointestinal tract freeing the sporozoites which then invade the epithelial cells of the small intestine. Inside these cells, the sporozoites undergo asexual multiplication and sexual development to form unsporulated non-infectious oocysts that rupture the host cell and are then excreted with the stool. In the environment, after 7 to 12 days and with temperatures between 22 and 32oC, sporulation occurs which results in division of the sporont into two sporocysts.
Cryptosporidium are protozoan that infects humans and non-human hosts. Fifteen species are infectious for non-human vertebrate host; however only seven of these (Cryptosporidium baileyi, Cryptosporidium canis, Cryptosporidium felis, Cryptosporidium hominis, Cryptosporidium meleagridis, Cryptosporidium muris and parvum) have been report to infect humans. The majority of species of Cryptosporidium appear to have some host specificity but are not strictly host specific.
Data has shown that Cryptosporidium hominis is common in humans whereas Cryptosporidium parvum is common in zoonotic species. The remaining species that have caused infections occurred mainly in patients with weak immune system.
Cryptosporidium species exists as a spherical oocyst (5um diameter) in the environment. The wall of the oocyst is made up of complex carbohydrates and lipids which surround four banana shaped sporozoites. This makes the oocyst extremely resistant to the environment.
After ingestion and exystation, the sporozoites stage enters into the host cells and begins a complex infection process. Asexual reproduction is followed by sexual reproduction where female macrogamonts and male microgamots develop and fertilisation occurs.
The resulting zygote zygote then develops a thick walled infectious oocyst that will exit the host or developed a thinned walled oocyst that will auto-infect the host.
Giardias are protozoan that inhabits the intestinal tracts of nearly all classes of vertebrates. Some species are commonly found more so in human’s and these are Giardia duodenalis which is sometimes referred to as Giardia intestinalis or Giardia lamblia. Zoonotic genotypes of Giardia duodenalis can be found in livestock, pets and some wildlife with some genotypes appearing to be host specific.
Giardia duodenalis exists as a cyst (12 x 5um), with a chitin-like wall making it resistant and protecting it from the harsh environment.
Infection of Giardia occurs in human when the cyst is transmitted through contaminated food, water or even human to human contact (faecal to oral due to poor hygiene).
Once the cyst is ingested, it opens (excystation) and releases two infectious non-encysted motile trophozoites. These trophozoites are bilaterally symmetrical, pear- shaped (12-15 by 6-8um) and binucleate. They have four pears of flagella along with a convex dorsal surface that allows attachment to the mucosa of the proximal small bowel of the host. The trophozoites multiply through asexual reproduction and some of the encyst are excreted when it passes through the bowels ready to infect another host.
Did you know that bacteria are not the only cause food poisoning outbreaks. There are other microorganims out here that can produce similar symptoms. These are the protozoan pathogens and they include Giardia, Cryptosporidium and Cyclospora. All have been associated with several foodborne outbreaks.
Protozoan are single-celled, microscopic animals that reproduce in the intestinal tract of the host (eg humans and animals). As part of their life cycle, they produce eggs (cyst or oocyst), which is part of their reproductive cycle and helps them to spread and reproduce. These eggs are excreted in the faeces and are extremely infectious through water or food. With the majority being waterborne, they are found in sewage, lakes and ponds. Although rare, swimming pools and possibly the drinking water could a source. The only way to find if they are present is to test for them using water microbiology laboratory.
If you are infected with these protozoans (intestinal tract), it causes the following symptoms: Watery diarrhoea, fever, muscle aches, abdominal cramps, nausea and vomiting. Symptoms can last for months.
