From Big Medical Encyclopedia

COCCIDIOSIS (coccidiosis) — the invasive disease resulting from development in cells of an intestinal epithelium of the person of parasitic protozoa — koktsidiya and characterized by disturbance of functions of intestines at unsharply expressed phenomena of intoxication.

It is around the world described by only several hundred cases To., about a nek-eye dominance in the countries with hot climate; in the Soviet Union To. it is registered in the Russian Federation, in the republics of Transcaucasia, the Uzbek and Ukrainian SSR. To. occurs both among adults, and among children.

The etiology

the Isospora belli Wenyon Activator, 1923, and Isospora hominis (Rivolta, 1878) Dobell, 1919, concerns to the Eimeriidae family of the class Sporozoa of the Protozoa type. In South Africa isolated cases of detection at the person of a koktsidiya of Isospora natalensis Elsdon-Dew, 1953 are described, but their pathogenicity for the person is found out still insufficiently.

Koktsidiya have a difficult development cycle, in Krom asexual reproduction (schizogony) is replaced sexual (sporogony) therefore the propagativny stage of koktsidiya — the oocyst allocated to the environment with excrements is formed. At one types koktsidy all development cycle happens in an organism of one owner, at other types — to change of owners.

Development of oocysts before formation of sporozoit in them proceeds at different types of koktsidiya in various time terms: from several hours to several days.

Fig. 1. Diagrammatic representation of oocysts of Isospora belli: 1 — an oocyst with a zygote in the center; 2 — formation of sporoblasts in an oocyst; 3 — an oocyst with two sporocysts containing four sporozoites.

Isospora belli parasitize only at the person in cells of an epithelium of a small bowel where there is all development cycle of a parasite (a schizogony and a sporogony). Oocysts are colourless, an ellipsoidal form or with small characteristic compression since one end, on Krom the micropyle — the opening in a cover covered with a lid is located. Length of an oocyst is from 20 to 30 microns, width is from 12 to 16 microns. The cover is double-circuit, homogeneous. Unripe oocysts contain the isolated spherical zygote located in the center of an oocyst (fig. 1, 1). At the room temperature during 24 — 72 hours or slightly more zygote is divided into 2 sporoblasts (fig. 1,2) which after formation of covers turn into the 2nd sporocysts of the spherical or a little extended form. Length sporocysts from 12 to 14 microns, width is from 7 to 9 microns. In everyone a sporocyst 4 sporozoites (fig. 1, 3) and a residual (residual) body are formed.

Isospora hominis occurs at the person a little less than I. belli. The development cycle of I. hominis is connected with change of the owner. The schizogony occurs in muscles of cattle and, apparently, at pigs therefore the large cysts containing a large number of merozoites are formed. The cysts which got together with meat of an animal into intestines of the person give rise to a sexual cycle of development (sporogony) in cells of an epithelium of a small bowel which comes to an end with formation of oocysts. The oocysts allocated with excrements already contain 2 the developed sporocysts about 4 sporozoitam and a residual body everyone. Cover of an oocyst very thin, as if tense on sporocysts, often broken off and it it is not always possible to consider in this connection sporocysts are found separately. Length of oocysts is 20 microns, width is 15 microns. The micropyle is not defined.


At To., the caused I. belli, a source of activators of an invasion is the person. In the environment of an oocyst of koktsidiya can keep viability within several months. Factors of transfer of activators are the food, water, hands and objects of use contaminated by the excrements containing oocysts of koktsidiya. A source of an invasion at To., the caused I. hominis, cattle is. Infection of people occurs at the use of badly boiled thoroughly or fried thoroughly meat containing cysts of koktsidiya.

To. is registered usually in isolated cases, however the flashes in a children's day nursery which captured during short term are described (apprx. 2 months) St. 30% of children.

The pathogeny

At penetration of sporozoit into cells of an epithelium of intestines arises the catarrh of a mucous membrane leading to disorder of functions of intestines and plentiful mucifyings, sometimes with impurity of blood.

Pathological anatomy

Fig. 2. Microdrug of a wall of a small bowel: 1 — long thin fibers of a mucous membrane are normal (are specified by shooters); 2 — deformation of fibers at a coccidiosis (it is specified by shooters).

Data on pathoanatomical changes at To. at the person are extremely limited. Not numerous data of biopsies confirm existence of inflammatory and atrophic changes in a small bowel. The atrophy of fibers of a small bowel, their flattening, deformation as club-shaped educations (fig. 2), expansion of crypts against the background of infiltration of a mucous membrane of a gut are described by eosinophils, polinukleara, lymphocytes and plasmocytes. On a top of fibers of a small bowel focal defeat of an epithelium in the form of consolidation, polymorphism, deviations in polarity of kernels while the epithelium of crypts constantly looks normal is noted and does not contain the activator. Massive infections with koktsidiya can lead to education in intestines of extensive erosion and sometimes ulcers.

Electronic microscopically in cytoplasm of an epithelium of fibers of a small bowel find all stages of sexual and asexual reproduction of a parasite, vacuoles of various size containing lipids. Increase in quantity of lysosomes, expansion of interepithelial spaces where lymphocytes, eosinophils, and also lipids get is noted. Parallelism between a damage rate of an epithelium and the number of the activator in it is not revealed. There is an assumption that the epithelium is damaged for the second time owing to dystrophy of own membrane of a mucous membrane.

A clinical picture

it is Experimentally established that an incubation interval at To., the caused I. belli, 6 — 8 days last. At natural infection it, apparently, can be other. The disease proceeds variously, without idiosyncrasies. Most often it is expressed by symptoms of enteritis, is more rare than a coloenteritis, and is followed by small temperature increase. Patients complain of the general weakness, a headache, lack of appetite, nausea, abdominal pains. A chair liquid with impurity of slime, sometimes blood, 4 — 6 and more times a day. Acute manifestations To. are connected with the period of asexual reproduction of koktsidiya (schizogony) in an epithelium of a small bowel and usually proceed apprx. 2 weeks. With approach of the period of a sporogony the acute phenomena calm down and in excrements there are oocysts which allocation can continue from several days to 1 month and more. At a blood analysis of patients To. in some cases hypochromia anemia is defined; from a leukocytic blood count of special changes it is noted. The disease proceeds approximately apprx. 1 month and usually comes to an end with recovery.

Cases of a heavy current are described To. with the sudden beginning, a rapid current, with temperature increase to 39 °, frequent (to 20 times a day) a liquid chair with impurity of a large amount of slime, pus and blood, with sharply expressed intoxication. In some cases a disease To. gets the long current and allocation of oocysts accompanied with disorder of intestines, several months can proceed.

Considerable part of cases To. proceeds without any symptoms and is defined only by detection in excrements of oocysts of koktsidiya.

At To., the caused I. hominis, at Krom in intestines of the person only the sexual cycle of development of koktsidiya proceeds, a wedge, symptoms are limited only to insignificant disorder of intestines.

The diagnosis

the Diagnosis can be made only on the basis of detection of oocysts of koktsidiya in excrements of the patient. Oocysts appear in excrements after the acute period of a disease owing to what the diagnosis is always late and is put already during recovery of the patient.

In excrements of the person sometimes it is possible to find transit oocysts of the koktsidiya parasitizing at various animals. They easily differ from oocysts of I. belli and I. hominis in the sizes, a form, number a sporocyst and number of sporozoit in everyone a sporocyst. For detection of oocysts do a native smear of excrements in a drop of water and investigate under a microscope. It is recommended to use also one of floatation enrichment methods of excrements (see. Helmintologic methods of a research ). Identification of species of koktsidiya perhaps only after finds of mature oocysts. For receiving they on a bottom of a Petri dish a uniform layer are distributed by 5 — 10 g of the excrements containing oocysts and fill in 2% with solution of potassium bichromate (for a growth inhibition of bacteria). At the room temperature in several hours or days in oocysts sporocysts and sporozoita on the basis of which studying the type of koktsidiya is defined develop.


Treatment is developed insufficiently. In mild and moderately severe cases symptomatic and fortifying treatment, vitamin therapy is applied; appoint bismuth nitrate the main on 1 g three times a day. In hard, long cases purpose of Chloridinum and Sulfazinum is recommended.

Forecast favorable. Complications and lethal outcomes at To. are not described.

Prevention same, as well as at other intestinal invasions, napr, amebiasis (see), lambliasis (see), it is also directed to identification and treatment of patients, and also suppression of ways of transfer of activators. Specific prevention is not developed.

Bibliography: Laboratory methods of a research of pathogenic protozoa, under the editorship of D. N. Zasukhin, page 247, M., 1957; L of e of yt-m and M.'s N 3. Amebiasis, coccidiosis, balanthidiasis and lambliasis, Tashkent, 1976, bibliogr.; The multivolume guide to microbiology, clinic and epidemiology of infectious diseases, under the editorship of H. N. Zhukova-Verezhnikov, t. 9, page 208, M., 1968; H e at d about of n A. The lake of u. R about a TT of e of 1 M. of Beitrage zum Lebenszyklus der Sarkosporidien, Berl. Mlinch. tierarztl. Wschr., S. 121, 1972, Bibliogr.; Levine N. D. a. I v e n s V. The coccidian parasites (Protozoa, Sporozoa) of rodents, Urbana, 1965; T r i e r J. S. a.o. Chronie intestinal coccidiosis in man, intestinal morphology and response to treatment, Gastroenterology, v. 66, p. 923, 1974.

V. B. Schensnovich; I. K. Yesipova (stalemate. An).