Colorectal cancer (CRC) has the third highest cancer incidence in the world. There is mounting evidence that the intestinal microbiota plays an important role in colorectal carcinogenesis. but there is no information on protozoa of intestinal microbiota except Blastocystis hominis, although data on this issue is scarce. In this study we are going to evaluate the prevalence of intestinal helminthes and protozoa in CRC patients and control group that includes random residents. Patients will be examined before, after surgery and chemotherapy. Parasites and protozoan infection intensity will be estimated by triple coproscopy.

The study will be conducted on the basis of Research Institute of Epidemiology, Microbiology and Infectious Diseases and Research Center of Oncology, Ministry of Public Health of the Republic of Uzbekistan.

All the CRC patients from Research Center of Oncology will be examined with their written concent. Diagnosis of CRC is based on the results of clinical examination, endoscopic, histological, X-ray and laboratory data according to International Classification proposed by the American Joint Committee on Cancer (AJCC) with application TNM (T-tumor, N-nodus, M-metastases) for diagnosis. Descriptors in T (primary tumor) mean the degree of the tumor spreading in layers of the intestine; descriptors in N mean absence of metastases or the number of lymph nodes with metastases; descriptors in M shows absence or presence of remote metastases.

The control group will be a random residents of Tashkent city without any complaints from gastrointestinal tract matched by gender and age to the patients with CRC. Age of individuals under examination will be taken at the range from 17 to 90 years old.

Collection of stool samples Three stool samples for parasitological examination will be taken from both control subjects and CRC patients at 1-2 days interval. Stool samples were collected in individual containers, containing 5 ml of Turdiev's preservative provided conservation and staining of protozoa cysts and eggs of worms for a year. The Turdiev's preservative includes:80 ml of 0.2% aqueous solution of sodium nitrite, 10 ml of formaldehyde, 2 ml of glycerin, 8 ml of Lugol's solution, 250 ml of distilled water.

Collection of material for C. parvum (Cryptosporidium parvum) detection in stool samples will be carried out by preparation of fresh feces thin smears.

Stool samples examination Parasitological diagnosis will be performed by triple coproscopy using formalin - ethyl acetate concentration technique. For preparations staining Lugol's solution was used. The intensity of protozoa will be estimated by the number of protozoa in the field of view (ocular x10, objective x40), the number of protozoa will be calculated at least in 10 fields of view. 1-2, 3-4 and 5-6 microorganisms in a field of view were considered as infection of low, mean and high intensity respectively.

Modified Ziehl- Neelsen method will be used for staining and detection of C. parvum preparations. The stained smears will be observed with ×100 oil immersion lens for the presence of C. parvum.

Parasitological examination of the additional group of the patients obtained chemotherapy will be carried out before and after surgery and complete course of chemotherapy.

Inclusion Criteria:

• All patients with colorectal cancer before, after surgery and chemotherapy.

For control group:

• Includes all individuals that doesn't have any complaints from gastrointestinal tract

Exclusion Criteria:

• Age before 18.
• Patients with other gastrointestinal disorders
• Patients with any chronic concomitant diseases

All patients with colorectal cancer hospitalized in Department of Coloproctology at Research Center of Oncology. Diagnosis of colorectal cancer is based on the results of clinical examination, endoscopic, histological, X-ray and laboratory data according to International Classification proposed by the American Joint Committee on Cancer (AJCC) with application TNM for diagnosis.

The control group will be a residents of Tashkent city without any complaints from gastrointestinal tract matched by gender and age to the patients with CRC.