What is Isosporosis?
Human isosporosis is caused by Isospora belli (Isospora hominis) spores. Parasites multiply in the epithelial cells of the mucous membrane of the small intestine, going through cycles of schizogony, sexual reproduction and sporogony, which ends in the external environment.
Causes of Isosporosis
Isospores are widely distributed in nature, there are more than 200 species, but only 2 of them cause pathology in humans. Isosporosis is anthroponosis, since I. belli and I. natalensis affect only humans.
Pathogenesis during Isosporosis
The source of infection is man. Infection occurs through the use of water contaminated with oocysts or food. Diseases are more often observed in children, both sporadic and small epidemic outbreaks (in institutions). In tropical countries, the incidence is much higher.
In the external environment, the isospores undergo asexual cycle of development, forming oocysts.
A person becomes infected with an alimentary route: oocysts get into his intestine with contaminated water and food. The development cycle of isospores in the intestine can be asexual (in these cases, the parasites, penetrating into the epithelial cells of the duodenal and jejunum mucous membranes, undergo a repetitive multiplication cycle of division, as a result of which more and more new cells are involved). Individual merozoites (one of the stages of the parasite development) form sex cells, which, merging, form immature oocysts. Oocysts are colorless, transparent, have an oval shape (predominantly), a thin double-shell, dimensions 25-30 x 12-15 microns. Further maturation of oocysts, trapped in the external environment during defecation, occurs in the soil.
Reproduction of isospores in the epithelial cells of the intestine leads to its damage, disruption of the processes of absorption of fluid and nutrients from the intestinal lumen – a diarrheal syndrome develops, accompanied by cramping abdominal pain. Stools frequent, watery, often subfebrile temperature.
The process in an immunocompetent organism usually proceeds favorably, all phenomena subside no later than after 7–10 days even without treatment. In many infected people, diarrhea syndrome does not develop at all, although isospores are found in feces.
Symptoms of Isosporosis
Isosporosis Clinic is characterized by symptoms of enteritis. The incubation period lasts 5-7 (up to 10) days. The disease begins with an increase in body temperature (sometimes up to 39 ° C). The febrile period can last up to a week. Simultaneously with an increase in body temperature or for 2-3 days, profuse watery diarrhea develops, sometimes with an admixture of a small amount of mucus and blood. Some patients have vomiting. In some cases, oocysts can be found in the feces of people who have no apparent clinical manifestations. Usually, the disease is acute, ending with recovery in 7-20 days after its onset. Occasionally, severe cholera-like forms of isosporosis and cases of its prolonged course are observed. They are noted in persons with reduced immunity or in patients with AIDS. In these cases, parasites can go beyond the mucous membrane of the small intestine and cause the development of disseminated isosporosis, which often leads to the death of the patient.
Diagnosis of Isosporosis
The diagnosis of isosporosis is established when cococidia oocysts are detected in native feces smears, as well as in smears stained with Lugol solution or 1% potassium dichromate solution. Viewing drugs produced with an increase of 10×40 or 7×40. Since the oocysts are almost transparent, they are easier to see when the condenser is lowered and the diaphragm is half-closed. Since the parasites in the feces are always scarce and they are difficult to detect, a series of fecal samples should be examined, looking at 8-10 drugs in each and at least 100 fields of view in each of them. To improve the efficiency of diagnostics, it is also recommended to carry out flotation of the material under study in a saturated solution of sodium salt according to the Fülleborn method.
The Darlington method is also used, which consists in the fact that feces are mixed with water and centrifuged to obtain a dense sediment. Then the precipitate is stirred in a mixture of equal parts of salt with glycerin and centrifuged again. After that, a film is taken from the surface of the loop for examination.
Microscopic preparations. In smears stained with Lugol’s solution and iron hematoxylin, the oocysts have the appearance of oblong-ellipsoid bodies, one or two ends of which are sometimes narrowed. Their sizes are 20–33 x 1O – 19 (30×12) µm. The oocyst wall is thin, smooth and colorless. In immature oocysts, the cytoplasm concentrated in the center forms a granular globe with a nucleus in the form of a bright rounded spot. In mature cysts one can see two oval-coated oval sporocysts covered with their own sheath with four elongated, comma-shaped sporozoites and residual bodies inside each.
Cultural and immunological methods in the diagnosis of isosporosis do not apply.
For the rehabilitation of patients using metronidazole, Fansidar, fazizhin and other drugs. It should be remembered about the toxicity of many therapeutic agents and their not very high effectiveness.