Cryptosporidiosis is a protozoal infection caused by cryptosporidia and occurring with a predominant lesion of the digestive tract. Typical clinical manifestations of cryptosporidiosis include profuse watery diarrhea, nausea, vomiting, spastic abdominal pain. Individuals with immunodeficiency, along with severe gastrointestinal form, may develop cryptosporidiosis of the biliary tract and respiratory tract. Cryptosporidiosis is diagnosed by detecting cryptosporidium oocysts in stool samples; less often with the help of ELISA, RIF, PCR. Treatment includes diet, rehydration, enzymes; according to indications – antibiotics.
ICD 10
A07.2 Cryptosporidiosis
General information
Cryptosporidiosis is a parasitic intestinal invasion characterized by gastroenteritis with diarrheal syndrome. Along with salmonellosis, shigellosis, campylobacteriosis, rotavirus infection, giardiasis, cryptosporidiosis is one of the most common intestinal infections of humans. The prevalence of cryptosporidiosis in industrially developed countries is 1-3%; in developing countries with a low level of sanitary culture – 5-10%. The risk of cryptosporidiosis is higher among children and immunocompromised patients (including HIV-infected people), in whom the infection can acquire a severe course. Nosocomial outbreaks of cryptosporidiosis, cases of group infection in kindergartens, schools, and families are possible.
Causes
The causative agents of protozoal infection are intracellular parasites of Cryptosporidia (Cryptosporidium), belong to the class of Sporozoasida, a subclass of coccidia (Coccidiasina). Cryptosporidia of the C. parvum species are pathogenic for humans. The entire life cycle of the parasite takes place in the body of a single host (animal or human), which secretes invasive oocysts with feces. Cryptosporidium oocysts can retain their pathogenic properties in the external environment for a long time.
Infection with cryptosporidiosis occurs by the fecal-oral mechanism (when drinking water, milk, food contaminated with pathogens), less often – through contact with infected animals or humans, homosexual sexual contact. In addition, sporozoites from oocysts can be released directly in the intestine without leaving the host body, which determines the mechanism of autoinfection in cryptosporidiosis.
The widespread occurrence of cryptosporidiosis in the population is partly explained by the low infecting dose of cryptosporidia: the disease can even cause 1-10 oocysts to enter the gastrointestinal tract; the average infecting dose is about 132 oocysts. A unique feature of cryptosporidium oocysts is their resistance to disinfectants (in particular, to chlorine), as well as their small size (4-7 microns), which allows them to freely penetrate through many filters. Most of the modern water purification technologies do not allow to achieve a 100% delay of cryptosporidium oocysts, therefore, the waterway of infection with cryptosporidiosis is considered today as the leading one. Children under 10 years of age, animal breeders, veterinarians, laboratory assistants, medical personnel of infectious departments have an increased risk of infection with cryptosporidiosis.
In the human digestive tract, the shells of the oocyst are destroyed, and sporozoites are released from it, which penetrate into enterocytes, separating from the cytoplasm of the cell by a double shell. In intestinal epithelial cells, sporozoites turn into trophozoites, and then, as a result of multiple division, into schizonts and merozoites of type I. The latter are able to attach to other epithelial cells, increasing the number of parasites. In addition, after several cycles of asexual reproduction, type I merozoites transform into type II merozoites forming male and female gametes. After the fusion of germ cells, a zygote is formed, which then develops into an oocyst.
Approximately 80% of cryptosporidium oocysts have a thick cell wall and are released into the external environment with feces or pharyngeal mucus. The remaining oocysts are thin-walled; sporozoites are released from them into the intestinal lumen, triggering a new cycle of parasite development as a result of endogenous invasion. The entire development cycle of parasites in the body of one host (from penetration to isolation into the external environment) takes 4-7 days.
Parasitizing in the intestinal epithelium, the pathogens of cryptosporidiosis cause degenerative changes in enterocytes. This is accompanied by the development of malabsorption syndrome, slowing down the absorption of water and electrolytes, inhibition of intestinal enzymatic activity, which finds clinical expression in the occurrence of profuse watery diarrhea. With cryptosporidiosis, it is also possible to damage the epithelium of the pharynx, larynx, esophagus, stomach, colon, and with aspiration of vomit – trachea and bronchi.
In severe cryptosporidiosis, hematogenic spread of cryptosporidia into various internal organs is noted. With normally functioning protective mechanisms, the cyclical development of cryptosporidia in the body is quickly suppressed and the manifestations of cryptosporidiosis are stopped. In immunocompromised individuals, the persistence of infection in the body can occur indefinitely, which causes the chronic course of cryptosporidiosis in the absence of repeated infection.
Symptoms
The duration of the incubation period in cryptosporidiosis is on average 4-14 days. The nature of clinical manifestations and the severity of the infection depends on the initial immune status of the patient. Individuals with normal immunity usually develop a gastrointestinal form of cryptosporidiosis; patients with immunodeficiency often have a bronchopulmonary (respiratory) form of infection, as well as dissemination to other organs.
In typical cases, cryptosporidiosis occurs in the form of acute gastroenteritis or enteritis. The most characteristic manifestations are profuse watery (“cholera-like”) diarrhea, cramping pains in the mesogastrium, nausea, repeated vomiting. The stool is watery, abundant, frequent (5-10 to 20 or more times a day), with a fetid smell. Signs of dehydration can be expressed to varying degrees: from a feeling of thirst and dry skin to a decrease in tissue turgor and tonic seizures. It is possible to increase the temperature to subfebrile or febrile indicators. In patients with a normal immune system, diarrheal syndrome lasts 5-12 days, after which the manifestations of cryptosporidiosis are stopped, and recovery occurs.
The course of cryptosporidiosis in patients with immunodeficiency (congenital hypogammaglobulinemia, receiving immunosuppressive therapy, undergoing organ transplantation, HIV /AIDS patients, etc.) is more severe and prolonged. In the gastrointestinal form of cryptosporidiosis, toxic-infectious and diarrheal syndromes, signs of dehydration are more pronounced. Approximately 60% of patients have an intestinal infection lasting 4 months or more.
Of the extra-intestinal forms of cryptosporidiosis, there is usually a lesion of the respiratory tract, biliary tract, rarely the pancreas. Respiratory (bronchopulmonary) cryptosporidiosis is accompanied by shortness of breath, cough with scanty mucosal sputum, respiratory failure, fever, lymphadenitis. Patients with AIDS often have cryptosporidiosis pneumonia, which leads to a fatal outcome. When the biliary tract is affected, cholecystitis, sclerosing cholangitis or hepatitis develops. Patients are worried about fever, nausea, pain in the right hypochondrium, jaundice, diarrhea.
Diagnosis and treatment
Differential diagnosis of acute intestinal infections and confirmation of cryptosporidiosis is based on the detection of oocysts of the pathogen in the stool. For this purpose, methods of staining fecal smears according to Zil-Nielsen, Romanovsky-Giemse, Kester are used. It is possible to detect cryptosporidium antigen in feces by ELISA, RLA, PCR, as well as in blood using immunofluorescence or enzyme immunoassay.
In the bronchopulmonary form of cryptosporidiosis, bronchoscopy is performed. Endoscopically, signs of tracheitis and bronchitis are detected; cryptosporidium oocysts are detected in the obtained material (sputum, tracheal and bronchial aspirate, bronchial biopsy). X-ray examination of the lungs allows you to see the picture of bilateral interstitial pneumonia. To confirm cryptosporidiosis of the biliary tract, percutaneous puncture of the gallbladder and intrahepatic bile ducts is resorted to.
Most infectious disease specialists believe that people with a normal immune system, mild or moderate course of infection do not need special treatment for cryptosporidiosis. For the relief of clinical manifestations, it is enough to prescribe a diet, oral rehydration, enzymes, antidiarrheal agents. In severe cases, including immunocompromised persons, it is necessary to prescribe antibacterial drugs of the macrolide group, furazolidone, metronidazole, pyrimethamine, spiramycin, etc.; correction of the water-electrolyte state using infusions of water-salt solutions.
Prognosis and prevention
In immunocompetent individuals, cryptosporidiosis occurs in a mild or moderate form and usually ends with spontaneous recovery. The greatest danger of cryptosporidiosis is for children under 2 years of age, patients with immunodeficiency conditions and receiving long-term immunosuppressive therapy. Disinfection of wastewater, boiling of tap water, installation of additional filters for water purification, sanitary education, compliance with anti-epidemic regime in children’s and medical institutions, as well as personal hygiene measures will prevent or minimize the risk of infection with cryptosporidiosis.