Intestinal infections: Isosporiasis

By Cristiano Antonino On Oct 31, 2022

Isosporiasis is an infection localised in the intestine and caused by Isospora belli (a protozoan coccidium)

The parasite attacks already debilitated immune systems, as in the case of HIV infection.

In these individuals, infection is not uncommon and in most cases is also accompanied by rather persistent diarrhoea (can last up to a month).

Isosporiasis, therefore, is counted among the possible complications of HIV, especially in developing countries where it occurs in 10% of cases.

How isosporiasis is transmitted

Transmission occurs via the fecal-oral route. Once the capsule of the oocyst (the first life stage of the parasite) has reached the intestine, it penetrates the cells of the intestinal mucosa; there the most significant modifications of the parasite begin, and it transforms first into a trophozoite (i.e. it assumes a round or amoeboid shape) and then into a schizont.

The schizonts multiply, generating the birth of merozoites, which destroy the enterocytes with which they come into contact.

How I notice it

The characteristic symptoms of an isospora belli infection are particularly evident in HIV-infected individuals, due to their debilitated immune system.

They include:

nausea
vomiting
chronic diarrhoea
abdominal pain
fever

An advanced stage of the infection is characterised by atrophy of the villi (projections of the mucous membrane inside the lumen), incorrect absorption of carbohydrates and lipids and osmotic diarrhoea.

In turn, this leads to weight loss, betabolic acidosis and hydroelectrolyte disturbances.