[Biology Class Notes] on Cryptosporidium Life Cycle Pdf

Knowledge of infectious diseases is understood deeply by the influence of fathers of microbiology such as Louis Pasteur and Robert Koch who has given the relationship between diseases and the microbial world. Their work led to identifying the world’s most infectious diseases. 

Cryptosporidium was first described in the early 20th century which has included Cryptosporidium parvum and Cryptosporidium muris as its first species. C. parvum was known to cause bovine diarrhoea in the 1970s. C. baileyi was known for causing respiratory disorders in poultry. Cryptosporidium is a water-borne protozoan parasite that has its importance in both medical and veterinary. It is known popularly for causing gastroenteritis in most of the hosts of vertebrae. Its genomes include Cryptosporidium parvum and C. hominis 

Cryptosporidium Parvum Life Cycle and Cryptosporidium Hominis Life Cycle

Cryptosporidium can cause diarrhoea which sometimes may be prolonged. Symptoms include diarrhoea and abdominal pain. Some other symptoms include nausea, vomiting, and fever. The infection depends on the variety of characteristics of parasite and host. Several species have been identified in Cryptosporidium, C. parvum, and C. hominis is the main reason for almost 90% of the cryptosporidiosis disease cases found in humans. C. hominis is associated with nausea, vomiting, diarrhoea, and malaise. C. parvum is associated with diarrhoea only. 

Cryptosporidium transmission can happen directly or indirectly, where the direct transmission can occur by fecal-oral, from animals to animals or animals to humans or human to human or human to animal. Where the human to human spread is being considered as a secondary case. Indirect transmission includes contact with fecally contaminated material, which includes water, food, clothes, and footwear. The indirect transmission may also occur due to environmental contamination that includes contamination of water bodies with feces that overflow due to heavy rainfall. There is another way of transmission that includes inhalation of oocytes, which causes immunocompromised diseases in children and adults. 

The major risk factor for C. parvum is the touching of farm animals and the main reservation for C. parvum is zootonic. The major risk factor for C. hominis is to travel outside the country and diaper change and the main reservoir includes asymptomatic carriage in the children. 

Cryptosporidium Life Cycle CDC

[Fig: Cryptosporidium life cycle]

The Cryptosporidium parvum life cycle and cryptosporidium hominis life cycle are as follows: the sporulated oocysts consist of four sporozoites, these oocysts are released by the infected host through feces or respiratory secretions. Where the transmission occurs through consumption of contaminated water or food or direct contact with an infected person, it is transferred to the suitable host where the excystation occurs. 

• The sporozoites are released and it infects the epithelial cells of the gastrointestinal tract and sometimes the respiratory tract as well. 

• In these cells, the parasites undergo asexual multiplication and then sexual multiplication in the brush border to produce microgamonts and macrogamonts. 

• The microgamonts undergo fertilization by microgametes that rupture from microgamont, oocysts are developed and sporulated in the host. 

• The zygote forms two different types of oocysts that are thick-walled and thin-walled.

• The thick-walled oocysts are excreted into the environment from the host and the autoinfection cycle is involved in the thin-walled oocysts and is not recovered from the stools.

• On excretion, the oocysts become infectious that enables the immediate transmission of feces orally. 

• Now, these oocysts are ready to enter the other host.

The infection caused by Cryptosporidium species and genotypes has different symptoms and signs. The incubation period of the parasite or cryptosporidium life cycle time is about two to ten days. The patients with immunocompetent, diarrheal illness are limiting and can be resolved typically in two to three weeks. Sometimes the immunocompetent illness can cause more severe complications that can be life-threatening. 

Conclusion

The Cryptosporidium species is considered an increasing water-borne protozoan parasite. It causes diarrhoea and immunocompromised diseases such as AIDS. Cryptosporidiosis in early childhood can cause impairment in growth, physical fitness, and cognitive development. The c parvum life cycle is comparatively complex and has multiple modes of transmission. The oocysts can survive in the environment for a long time and they are resistant to chemical disinfectants that are used in the water to remove the species.