Question

virology and parasitology homawork 1: ( be careful about the plaigarism )

Explain Cyprtosporidium infection. Talk about in which parasite group it is, its morphological forms, life cycle, transmission routes, diseases that it causes and diagnostic methods.

Answer 1

Ans:

Introduction:

The Cryptosporidium is a small, unicellular protozoan parasite often reported in mammals including humans and cattle by causing the disease named cryptosporidiosis. Their distribution is wide-spread. A sporadic form of this disease also been reported. The members of the genus Cryptosporidium belong to the family of Cryptosporidiidae and were first reported by Tyzzer in 1907. On an average of 25 or 30 different species have been described under this genus. There are many subtypes of this pathogen discovered across the world showing a variety of clinical manifestations. The name 'Cryptosporidium' was derived from the fact that their cells have spores closed (cryptos) by a very tough wall.

Infection: The parasite often reported to cause infections in the human intestine and various dairy animals. It may infect other vertebrates. They may enter through different routes such as an oral cavity, feces, etc. They are often reported from immunocompromised patients such as those infected with Human Immunodeficiency Virus (HIV). The incubation period of the Cryptosporidium is as long as two weeks once enters the body. The Cryptosporidium infection may be symptomatic or asymptomatic which is very critical to its wide-spread transmission. Children are easily affected by this parasite while if the immunity of the adults is strong then its infection could be limited. The species that infect humans and cattle generally include Cryptosporidium hominis and Cryptosporidium parvum and have raised major health concerns.

Parasite group: There are various species known to cause cryptosporidiosis in a variety of vertebrates which include C. parvum, C. hominis, C. galli, C. felis, etc. They are generally classified under the phylum Apicomplexa which also includes other parasites such as genera Plasmodium, Toxoplasma, Theileria, etc.

Morphological form: the Cryptosporidium developmental stages could be described as follows

1. Meronts-type I, type II
2. Gamonts
3. Oocysts

Life cycle: A thick-walled oocyst expelled through the host can develop into sporozoite that converts into a trophozoite. Asexually it converts into type I meront which further converts into a merozoite. It can form type II meront that further convert into merozoite and enter into the sexual cycle by the conversion to undifferentiated gamont which may have variable cell size (micro or macro). The microgamonts can produce microgametes that further give rise to a zygote. Also, macrogamonts can directly convert into a zygote. The zygote can either release tough walled oocyst into the environment or form thin-walled oocyst that can have a potential for self infection. In this way, a tough walled spore containing oocyst is ready to infect the environment by many routes such as feces and can contaminate water bodies. Such water could be ingested by humans through the oral cavity where it directly enters the intestine and invades its tissues to cause infection. It can remain them for many days or months probably. The sporulated oocyst can exit host via feces.

Transmission route: The major transmission route is the oral cavity and feces. Usually, the mature oocyst released into the environment via zygotes of the parasite can contaminate the water which may be ingested by humans or cattle or other vertebrates. It enters the intestine and further exits through feces. So, the cycle continues.

Disease: In humans, it causes watery diarrhea, fatigue, fever, etc. The disease called cryptosporidiosis is developed in humans and cattle. Its clinical symptoms are wide and cause severe infections in immunocompromised patients. It can also cause infection in fishes and reptiles. The disease could be deadly or sporadic in nature. Very rare diseases or infections are reported apart from that of the intestine.  

Diagnosis method: There are various ways to diagnose the disease which include tissue biopsy or the examination of the stool samples to detect the presence of oocysts. The cellular staining method which is called acid-fast staining is widely utilized for the microscopic examination of the parasite. The other popular method is known as direct fluorescent antibody has also been suggested by doctors and researchers investigating this parasite's mode of infection. There are many commercially diagnostic kits available to detect its presence by means of the Enzyme-Linked Immunosorbent Assay (ELISA) method.