CRYPTOSPORIDIUM: CHARACTERISTICS, SPECIES, CONTAGION, SYMPTOMS - BIOLOGY - 2025

Cryptosporidium is a genus of organisms belonging to the protista kingdom, specifically the phylum Apicomplexa. It is found mainly in polluted waters and is one of the main causative agents of diarrhea in humans.

It is an organism that has parasitic life, since it requires a host to complete its development. In his case, the host is the human being. Furthermore, it does not require any animal to act as a vector.

Cryptosporidium. Source: Punlop Anusonpornperm

This parasite is responsible for the development of an infection known as cryptosporidiosis, which mainly affects the organs of the intestinal tract. It is not very dangerous, unless the immune system is compromised. It is also linked to poor hygienic conditions, since its main route of infection is water.

characteristics

Morphology

Cryptosporidium oocysts have a characteristic shape, which can be spherical or oval. They can measure between 6 and 7 microns. These are surrounded and protected by a fairly resistant wall that is double.

A total of four sporozoites are found inside the cysts. The latter have a vermiform shape. It is important to note that some oocysts have thick walls and others have thinner walls.

Lifecycle

The life cycle of this parasite is a bit complex, as it undergoes a series of transformations within its only host, which is humans. It is also made up of a phase of asexual reproduction and another of sexual reproduction.

The main source of infection for this parasite is water. But not necessarily the water that is consumed, but also the water from swimming pools and other recreational water sources. Exceptionally, it can also happen that the parasite enters the host's body through some foods such as salads.

What is found in the water are oocysts, within which several sporozoites are contained. These are just one of the many stages that occur in the life cycle of parasites of the genus Cryptosporidium.

Cryptosporidium life cycle. Source: CDC / Alexander J. da Silva, PhD / Melanie Moser (PHIL # 3386), 2002

These sporozoites reach the environment from infected subjects, who release them through two mechanisms: through feces or through bodily fluids such as respiratory fluids. Likewise, the entry of sporozoites into the body can be by ingestion or by inhalation.

Inside the host

Once inside the host, the oocysts travel through the digestive tract until, at the level of the intestine, they break, releasing the sporozoites that are contained in them. These have the ability to infect the epithelial cells of the intestine. Inside cells, sporozoites transform into trophozoites.

Reproduction types

Asexual reproduction

It is important to note that it is in epithelial cells where asexual reproduction takes place, which is known as merogonia. This process consists of a series of successive divisions in which each fragment obtained has a portion of cytoplasm.

Trophozoites transform into type I meronts. These contain within them a total of 8 merozoites, which have the ability to enter other adjacent cells and transform again into type I meronts. Type II meronts can also form. These contain 4 merozoites.

Sexual reproduction

Each merozoite, which is also called a gamonte, undergoes a process of gametogenesis, through which female gametes (macrogamonts) and male gametes (microgamonts) are formed.

When they are mature, fertilization or fertilization occurs between a macrogamont and a microgamont. As a result of this a zygote is obtained. From here the oocysts originate.

Now, not just one type of oocyst is obtained, but it is possible that two types are formed:

- Some that are expelled through faeces or other fluids, which are characterized by having a hard cover and resistant to hostile environmental conditions

- Other oocysts that remain inside the host, have a thin cover and fulfill the function of reinfecting it, thus keeping the infection latent.

Species

Cryptosporidium parvum

Cryptosporidium parvum. Source: See page for author

It is the best known and most studied species of the genus Cryptosporidium. Within this group, it is the main cause of gastroenteritis in humans, since it greatly affects the intestinal tract. It can be particularly deadly in people who have a compromised immune system, such as those HIV positive who are already in the AIDS phase.

Cryptosporidium

It is the second most common species of the genus Cryptosporidium. Together with Cryptosporidium parvum, it is one of the protists that are most widely used as causative agents of human digestive system infections.

Cryptosporidium bailey

It is a species of Cryptosporidium that has a predilection for birds, with chickens being its main host. It is mainly housed in the digestive tract of these animals and causes symptoms that have to do with diarrhea. In addition to chickens, this species can affect other types of birds such as ducks, turkeys or quail.

Cryptosporidium serpentis

This species of Cryptosporidium exclusively affects reptiles, especially snakes. From there it derives its name. As a member of this genus, its life cycle is similar to that of the type species, Cryptosporidium parvum. The main manifestation of an infection by this protozoan in snakes is the constant regurgitation of ingested food.

Disease

The disease caused by this protozoan is known as cryptosporidiosis. This name is generic for infections that are caused by any of the Cryptosporidium species out there.

Contagion

As mentioned above, the means through which oocysts, which are the infecting forms, enter the body is through water. It can be through the water that is ingested and used to prepare food or also through the water of a pool or natural body of water in which the individual enjoys a bath.

Similarly, another route of infection is the ingestion of contaminated food.

The contagion is generally fecal - oral, which is why it is frequent in populations where hygiene measures are deficient. Likewise, cases have also been described in which the contagion has been from person to person or from animal to person.

Symptoms

Because the Cryptosporidium parasite fixes mainly on the intestinal mucosa, its signs and symptoms are related to the digestive system. Among these, the most frequent that can occur are:

- Severe stomach pain, colicky type

- Frequent liquid stools

- Decrease in body weight, because the nutrients are absorbed by the parasite.

- vomiting

- Nausea

- Increase in body temperature

- Dehydration from diarrhea and vomiting

More severe symptoms

These symptoms occur in all people who are affected by this parasite. However, the severity of the condition is determined by the state of the person's immune system. In the case of those who have some type of immunosuppression, the symptoms are usually more severe, such as:

- Considerable weight loss (approximately 10% of body weight)

- Jaundice (yellowing of the skin and mucous membranes)

- Severe pain in the right upper quadrant of the abdomen

- Intense diarrhea, even reaching more than 10 stools a day, with consequent dehydration

- Chronic deficiency in the absorption of nutrients

Consequences

It is important to note that if these symptoms are not treated in time, the medical condition worsens, causing serious consequences, such as:

- Significant weight loss, which can lead to progressive wear of the different body systems.

- Deterioration and chronic inflammation of some important organs of the digestive tract such as the gallbladder, pancreas or liver.

- Chronic malnutrition, caused by poor absorption of nutrients at the intestinal level.

- Serious and continuous dehydration, which also greatly affects various organs and the internal balance of the body.

In people known as immunocompetent, that is, who have an immune system that works in optimal conditions, infection by this parasite does not involve much care and risk.

However, in those whose immune system is weakened by some condition or disease, this pathology can even have fatal consequences.

Diagnosis

When a patient goes to the doctor suffering from continuous and persistent diarrhea for more than two weeks, he must rule out the presence of an intestinal parasite, those belonging to the Cryptosporidium genus being among the first options.

Now, infections by this genus of protozoa can be diagnosed through various medical procedures. These include:

Stool examination

Also known as stool culture, it is an examination by which stool is evaluated at a microscopic level in order to identify possible pathogens.

Although this is not a test that allows the diagnosis of Cryptosporidium infection, it is very useful because it allows a differential diagnosis with respect to infections by other parasites.

Acid fast stain test

It is the most widely used test to definitively diagnose infections caused by parasites of the Cryptosporidium genus.

This is a fairly specialized test, which consists of taking a sample of stool or intestinal tissue and subjecting it to a staining procedure with a special dye and then being washed with an acid solution.

Microorganisms that retain dye despite acid washing are considered acid fast. In this case, the microorganisms of the genus Cryptosporidium turn out to be acid resistant, in such a way that this is a test that provides high reliability and is the one most used by specialists to make an accurate diagnosis.

Imaging exams

Medical procedures that allow imaging of the inside of the body can also be of great help in the diagnosis of cryptosporidiosis.

Through abdominal ultrasound and specialized ultrasound it is possible to detect chronic inflammation of some organs such as the liver or the gallbladder, especially the bile ducts, which, added to the rest of the characteristic symptoms, could lead to a disease caused by this microorganism.

Treatment

As already indicated previously, cryptosporidiosis is not a very dangerous disease for people who suffer from it, as long as the immune system is in optimal condition and functions properly. In these people, the infection usually resolves in a reasonable period of time and does not exceed a few episodes of diarrhea.

In those whose immune system is depressed, it is necessary to apply a treatment that solves the negative effects of the symptoms.

One of the treatment options for this infection is medications that reduce intestinal motility. This results in food remaining in the intestine for a longer period of time, which mainly helps to stimulate the absorption of fluids, thus relieving the effects of constant diarrhea. Among these drugs, the most widely used is loperamide.

On certain occasions, depending on the severity of the condition, the doctor may also prescribe some antiparasitic medicine, which can intervene in the metabolism of Cryptosporodium and thus counteract its harmful effects, especially diarrhea. The antiparasitic most chosen by doctors for these cases is nitazoxanide.

References

1. Curtis, H., Barnes, S., Schneck, A. and Massarini, A. (2008). Biology. Editorial Médica Panamericana. 7th edition.
2. Luján, N. and Garbossa, G. (2008). Cryptosporidium: one hundred years later. Acta Bioquímica Clínica Latinoamericana. 42 (2).
3. Luna, S., Reyes, L., Chinchilla, M. and Catarinella, G. (2002). Presence of Cryptosporidium spp oocysts in surface waters in Costa Rica. Latin American parasitology. 57 (2).
4. Navarro, L., Del Águila, C. and Bornay. (2011). Cryptosporidium: a genus in review. Situation in Spain. Infectious Diseases and Clinical Microbiology. 29 (2).
5. Neira, P. (2005). About Cryptosporidium spp in Chile. Medical Journal of Chile. 133 (7).
6. Robertson, L. (2014). Introduction to Cryptosporidium: The parasite and the Disease. Chapter of the book Cryptosporidium as a Foodborne Pathogen.
7. Rodríguez, M., Muñoz, P., Valerio, M., Bouza, E., Rabadán, P. and AnayaF. (2010). Cryptosporidium parvum infection in a kidney transplant recipient. Nephrology (Madrid). 30 (4).