What is the Difference Between Cryptosporidium and Giardia

The main difference between Cryptosporidium and Giardia is that the Cryptosporidium is the most common protozoan parasite that causes diarrhea, whereas the Giardia is not very much positively associated with moderate to severe diarrhea. Furthermore, nitazoxanide is the only drug that is effective for the cryptosporidiosis, while several classes of drugs, including tinidazole and metronidazole, show a good efficacy for giardiasis. 

Cryptosporidium and Giardia are the two genera of common protozoan parasites. Generally, they are well known for causing waterborne illnesses.  

Key Areas Covered 

1. Cryptosporidium
     – Definition, Features, Pathology
2. Giardia
     – Definition, Features, Pathology
3. What are the Similarities Between Cryptosporidium and Giardia
     – Outline of Common features
4. What is the Difference Between Cryptosporidium and Giardia
     – Comparison of Key Differences

Key Terms 

Cryptosporidiosis, Cryptosporidium, Diarrhea, Giardia, Giardiasis, Parasitic Protists

Difference Between Cryptosporidium and Giardia - Comparison Summary

Cryptosporidium – Features, Pathology 

Cryptosporidium is a genus of parasitic protists that causes cryptosporidiosis. The main symptom of this disease is moderate to  severe diarrhea. Therefore, Cryptosporidium is generally associated with moderate to severe diarrhea. Some of the other symptoms of this disease include abdominal pain, nausea, vomiting, and low-grade fever.  These symptoms last for less than 30 days.

Difference Between Cryptosporidium and Giardia

Figure 1: Cryptosporidiosis

However, in immunodeficient patients, including AIDS and cancer patients, the cryptosporidiosis can become lethal. Deaths may occur due to severe diarrhea. 

Giardia – Features, Pathology 

Giardia also belongs to the genus of parasitic protists. It causes giardiasis. It is usually associated with mild to moderate diarrhea. The other symptoms of this disease include gastrointestinal disturbances, flatulence, and discomfort. These symptoms may last for several days.

Cryptosporidium vs Giardia

Figure 2: Giardia lamblia Life Cycle

Concerning the transmission of this parasite, the giardiasis transmits by the ingestion of cysts through the fecal-oral route. Here, the cysts are the dormant structures of Giardia. Also, the cyst is capable of staying infectious in cold water for up to three months.  

Similarities Between Cryptosporidium and Giardia  

  • Cryptosporidium and Giardia are the two common genera of parasitic protozoans that cause waterborne illnesses. 
  • Importantly, they infect the gastrointestinal tract of both animals and humans. 
  • Also, they can multiply inside the host and therefore, a serious infection can develop even from a single organism.  
  • The common route of this infection is through drinking water or contaminated hands. 
  • In both types of infections, diarrhea is the most common symptom. But, the severity defers. 
  • Other symptoms include dehydration, stomach pain, lack of appetite, weight loss, bloating, nausea, vomiting, etc.  
  • The diagnostic method in both cases is the testing of the stool.  
  • Infected people pass dormant, protective cysts of parasites through their feces, contaminating soil, food or water. 
  • Also, both parasites can live long periods in the environment, especially in lakes, rivers, streams and roof water.  
  • Furthermore, both dormant stages contain chlorine-resistant outer shells. 
  • Concerning the preventive measure, proper purification of drinking water, reliable wastewater treatment systems, sanitation, and hygiene can eliminate the risk of these infections. 

Difference Between Cryptosporidium and Giardia


Cryptosporidium refers to a genus of parasitic protists that primarily involves in watery diarrhea while Giardia refers to another genus of flagellate protozoans inhabiting the intestines of various mammals. 

Dormant Stage 

The dormant stage of Cryptosporidium is the oocyst, while the dormant stage of Giardia is the cyst. 


Cryptosporidium causes Cryptosporidiosis while Giardia causes giardiasis. 

Pathological Significance 

Cryptosporidium is the most common diarrhea-causing protozoan parasite worldwide, while Giardia is not significantly positively associated with moderate-to-severe diarrhea. 

Appearance of Symptoms 

Symptoms of cryptosporidiosis appear between 1 and 12 days (usually 7 days) after the infection while the symptoms of giardiasis appear between 3 and 25 days (usually 7 to 10 days) after the infection. 

Persistence of the Illness 

Symptoms of cryptosporidiosis may persist for 2 weeks, while the symptoms of giardiasis may persist for 3-4 days. 


Nitazoxanide is the only effective drug for cryptosporidiosis while several classes of drugs, including tinidazole and metronidazole show a good efficacy for giardiasis. 

Difficulty in Eradication 

Cryptosporidium oocyst can survive several months in cold water, soil in dark, and up to one year in low-turbidity water while Giardia cysts can survive several months in cold water.  


Basically, Cryptosporidium is one of the two main types of parasitic protists that cause waterborne illnesses. It produces a dormant oocyst, which passes through the feces of infected individuals to the outside environment. Furthermore, cryptosporidiosis is the disease caused by the Cryptosporidium, which is the most common diarrhea-causing pathogen. Cryptosporidiosis causes moderate to  severe diarrhea. On the other hand, giardiasis is a disease caused by Giardia. Giardia is the second type of parasitic protists that causes mild to moderate diarrhea. It produces a dormant cyst. Therefore, the main difference between Cryptosporidium and Giardia is the severity of diarrhea. 


1. Squire, Sylvia A., and Una Ryan. “Cryptosporidium and Giardia in Africa: Current and Future Challenges.” Parasites & Vectors, BioMed Central, 20 Apr. 2017, Available Here.

Image Courtesy:

1. “Cryptosporidiosis 01” By CDC/Alexander J. da Silva, PhD/Melanie Moser (PHIL #3386), 2002 – CDC Public Health Image Library (Public Domain) via Commons Wikimedia  
2. “Giardia lamblia life cycle” By PHIL – Public Health Image Library – search for giardia, life, cycle (Public Domain) via Commons Wikimedia  

About the Author: Lakna

Lakna, a graduate in Molecular Biology and Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things. She has a keen interest in writing articles regarding science.

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