Overview
Isospora coccidiosis is a parasitic protozoan disease caused by Isospora coccidia parasitizing the epithelium of the human intestinal mucosa, causing damage to the intestinal mucosa. Clinical manifestations include diarrhea, nausea, vomiting and abdominal pressure. There are two types of Isospora parasites in humans: Isospora belli and I. natalensis. Human infections with Isospora belli are dominated by Isospora natalensis, and Isospora natalensis is very rare. Isosporic coccidiosis is a self-limiting disease, and the worms are cleared on their own in most patients.
Etiology
The life history of Isospora includes cleavage, gametogenesis and sporulation, the first two of which take place in the host. After accidental ingestion of food or drinking water contaminated with mature oocysts, the oocysts are ruptured by digestive juices in the small intestine, and the ascospores escape and enter the epithelial cells of the small intestinal mucosa to develop into trophozoites, which produce large numbers of cleavage bodies through cleavage reproduction, and then rupture the bodies to release the schizospores and invade into neighboring epithelial cells to continue their cleavage bodies. After about 1 week, some of the schizonts develop into female and male gametocytes and female and male gametes in the epithelial cells or intestinal lumen, and after mating, they form syncytia and secrete the cystic wall to develop into oocysts, which are discharged in the body or with feces and continue to develop.
Symptoms
Isospora infection can last for weeks or even years, and most symptoms are mild. Diarrhea is the main symptom, and mucus stools are common. Eosinophils are often present in large numbers, but neutrophils are rare. Diarrhea occurs several times a day, but there are reports of up to twenty times a day, lasting three to four days, with periodic episodes lasting several months. In addition, patients often have abdominal cramps, fever, nausea, vomiting, loss of appetite, and weight loss. A few patients have malabsorption in the small intestine, especially fat malabsorption, with coarse fat particles in the stool. Abdominal discomfort, low-grade fever and diarrhea are the most common symptoms in foreign “volunteer” experimental infections or accidental infections among laboratory workers. Diarrhea begins 1 week after infection and lasts for 5 to 10 days, but the discharge of oocysts in the stool can continue for 10 to 20 days. Asymptomatic carriers are present in this disease, but the exact number of asymptomatic carriers cannot be determined because oocysts are often missed in the stool.
Examination
Microscopic examination of fresh stools concentrated by zinc sulfate floatation improves oocyst detection. Isospora oocysts are highly transparent and can be easily missed in direct smears, in which case the aperture of the microscope can be narrowed until other protozoa or bacteria are clearly outlined in the smear.
Diagnosis
The definitive diagnosis of the disease depends on the finding of Isospora coccidia oocysts in the stool. The detection of oocysts can be improved by microscopic examination of fresh stool taken and concentrated by zinc sulfate floating. Isospora coccidia oocysts are highly transparent and can be easily missed in direct smears, which can be helped by narrowing the aperture of the microscope until other protozoa or bacteria are clearly outlined in the smear. The main criteria for identification are the size of the oocysts, the number of ascospores, and the presence or absence of sporocysts around the ascospores. In addition to stool examination, biopsy of small intestinal mucosa and examination of intestinal contents may also reveal various stages of Isospora development. Examination of duodenal drainage fluid may also be positive in some patients.
Differential diagnosis
This disease should be distinguished from other diarrhea, isosporic coccidiosis is widely distributed in the tropics and subtropics, especially with amoebic dysentery, intestinal trichomoniasis, Giardia lamblia, cryptosporidiosis, etc., but the patient’s body infection is quite rare.
Complications
Chronic diarrhea, water-electrolyte disorders, persistent or fatty diarrhea, weight loss, and even death may result. The damage to the intestinal mucosa, resulting in diarrhea and vomiting, etc., can lead to water electrolyte disorders, and if the condition is not treated in a timely manner, or in severely ill patients, it can lead to fatty diarrhea and malnutrition.
Treatment
Isosporic coccidioidomycosis is a self-limiting disease, most patients can be cleared of the worms themselves. There is no specific treatment for this disease. The treatment of choice is sulfamethoxazole/metronidazole (compound sulfamethoxazole), or furazolidone. Ethylaminopyrimidine plus sulfadiazine and primaquine plus chloroquine have some efficacy; however, metronidazole and tetracycline seem to be ineffective.
Prevention
1. Don’t drink cold water, eat raw food and unclean fruits and vegetables.
2. Wash hands and cut nails before and after meals.
3. Cook food thoroughly, especially when barbecuing or eating hot pot.
4. Educate children to change the habit of eating fingers and biting nails.
5. It is best if children do not wear open underwear to bed to prevent them from scratching their anus.
6. Clean toys regularly or scrub them with 0.05% iodine solution.
7. Strengthen the management of water sources to avoid water pollution.