Cystoisospora/Cystoisosporiasis and Cyclospora/Cyclosporiasis

General Characteristics

Basic features of Cystoisospora and Cyclospora

• Protozoans Protozoans Cell Types: Eukaryotic versus Prokaryotic:
  • Single-celled
  • Obligate intracellular parasites
• Taxonomy:
  • Class: Conoidasida
  • Subclass: Coccidia

Clinically relevant species

Both organisms cause intestinal disease in humans.

• Cystoisospora belli (formerly Isospora belli) causes cystoisosporiasis.
• Cyclospora cayetanensis causes cyclosporiasis.

Epidemiology

Cystoisospora:

• Occurs worldwide
• Predominantly seen in tropical and subtropical regions
• The least common of the intestinal coccidia that infect humans

Cyclospora:

• Found in developing nations in tropical and subtropical areas:
  • Latin America
  • Egypt
  • Sub-Saharan Africa
  • India
  • Southeast Asia ASIA Spinal Cord Injuries
• United States: approximately 16,000 cases of foodborne illness each year

Pathogenesis

Host

Both species are found only in humans.

Risk factors

Cystoisospora (severe disease):

• HIV HIV Anti-HIV Drugs/ AIDS AIDS Chronic HIV infection and depletion of CD4 cells eventually results in acquired immunodeficiency syndrome (AIDS), which can be diagnosed by the presence of certain opportunistic diseases called AIDS-defining conditions. These conditions include a wide spectrum of bacterial, viral, fungal, and parasitic infections as well as several malignancies and generalized conditions. HIV Infection and AIDS
• Lymphoma Lymphoma A general term for various neoplastic diseases of the lymphoid tissue. Imaging of the Mediastinum and leukemia
• Hypogammaglobulinemia Hypogammaglobulinemia Selective IgA Deficiency
• Immunosuppressive therapy
• Infants and young children

Cyclospora:

• Endemic areas:
  • Poor sanitation Sanitation The development and establishment of environmental conditions favorable to the health of the public. Hepatitis E Virus
  • Low socioeconomic status
• Nonendemic areas:
  • Travelers
  • Import of fresh food from endemic regions
• Severe disease:
  • Young children
  • Older adults
  • Immunocompromised immunocompromised A human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation. Gastroenteritis individuals (e.g., those with HIV HIV Anti-HIV Drugs/ AIDS AIDS Chronic HIV infection and depletion of CD4 cells eventually results in acquired immunodeficiency syndrome (AIDS), which can be diagnosed by the presence of certain opportunistic diseases called AIDS-defining conditions. These conditions include a wide spectrum of bacterial, viral, fungal, and parasitic infections as well as several malignancies and generalized conditions. HIV Infection and AIDS)

Transmission

Both species are transmitted via the fecal–oral route (ingestion of contaminated food and water).

Life cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation

Cystoisospora and Cyclospora undergo a similar life cycle Cycle The type of signal that ends the inspiratory phase delivered by the ventilator Invasive Mechanical Ventilation:

• Ingestion of sporulated oocysts from contaminated food or water
• Sporozoites Sporozoites The product of meiotic division of zygotes in parasitic protozoa comprising haploid cells. These infective cells invade the host and undergo asexual reproduction producing merozoites (or other forms) and ultimately gametocytes. Antimalarial Drugs released in the small intestine Small intestine The small intestine is the longest part of the GI tract, extending from the pyloric orifice of the stomach to the ileocecal junction. The small intestine is the major organ responsible for chemical digestion and absorption of nutrients. It is divided into 3 segments: the duodenum, the jejunum, and the ileum. Small Intestine: Anatomy → penetrate intestinal epithelial cells
• Undergo asexual reproduction → sexual stage begins after invading another cell
• Fertilization Fertilization To undergo fertilization, the sperm enters the uterus, travels towards the ampulla of the fallopian tube, and encounters the oocyte. The zona pellucida (the outer layer of the oocyte) deteriorates along with the zygote, which travels towards the uterus and eventually forms a blastocyst, allowing for implantation to occur. Fertilization and First Week results in immature oocysts → excreted in the stool
• Sporulation occurs in the environment

Clinical Presentation

Cystoisosporiasis

Cystoisosporiasis has an incubation Incubation The amount time between exposure to an infectious agent and becoming symptomatic. Rabies Virus period of 7–14 days. Presentation of the disease can vary depending on the individual’s immune status.

• Immunocompetent host:
  • Acute
  • Usually mild and self-limited (usually resolves in 7–10 days)
  • Some hosts are asymptomatic.
  • Diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea:
    • Nonbloody
    • Watery
    • Sudden onset 
  • Crampy abdominal pain Abdominal Pain Acute Abdomen
  • Anorexia Anorexia The lack or loss of appetite accompanied by an aversion to food and the inability to eat. It is the defining characteristic of the disorder anorexia nervosa. Anorexia Nervosa
  • Nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics and vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia 
  • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever 
  • Malaise Malaise Tick-borne Encephalitis Virus
  • Malabsorption Malabsorption General term for a group of malnutrition syndromes caused by failure of normal intestinal absorption of nutrients. Malabsorption and Maldigestion and weight loss Weight loss Decrease in existing body weight. Bariatric Surgery (with prolonged symptoms)
  • Also associated with acalculous cholecystitis Acalculous cholecystitis Inflammation of the gallbladder wall in the absence of gallstones. Cholecystitis
• Immunocompromised immunocompromised A human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation. Gastroenteritis host:
  • Chronic, protracted clinical course
  • Severe diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea:
    • Nonbloody
    • May develop steatorrhea Steatorrhea A condition that is characterized by chronic fatty diarrhea, a result of abnormal digestion and/or intestinal absorption of fats. Diarrhea 
  • Abdominal pain Abdominal Pain Acute Abdomen 
  • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever 
  • Malabsorption Malabsorption General term for a group of malnutrition syndromes caused by failure of normal intestinal absorption of nutrients. Malabsorption and Maldigestion and weight loss Weight loss Decrease in existing body weight. Bariatric Surgery 
  • Dehydration Dehydration The condition that results from excessive loss of water from a living organism. Volume Depletion and Dehydration:
    • Renal insufficiency
    • Electrolyte disturbances

Cyclosporiasis

Cyclosporiasis has an incubation Incubation The amount time between exposure to an infectious agent and becoming symptomatic. Rabies Virus period of approximately 7 days. 

• Mostly asymptomatic, especially in immunocompetent individuals
• Can last weeks to months (if untreated)
• General symptoms:
  • Diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea: 
    • Watery
    • Blood or mucus can occasionally be seen
  • Anorexia Anorexia The lack or loss of appetite accompanied by an aversion to food and the inability to eat. It is the defining characteristic of the disorder anorexia nervosa. Anorexia Nervosa
  • Nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics
  • Fatigue Fatigue The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli. Fibromyalgia
  • Weight loss Weight loss Decrease in existing body weight. Bariatric Surgery
  • Bloating Bloating Constipation and flatulence
  • Low-grade fever Low-Grade Fever Erythema Infectiosum
  • Biliary disease

Diagnosis

Diagnosis of cystoisosporiasis

• General laboratory findings:
  • Eosinophilia Eosinophilia Abnormal increase of eosinophils in the blood, tissues or organs. Autosomal Dominant Hyperimmunoglobulin E Syndrome
  • Evidence of dehydration Dehydration The condition that results from excessive loss of water from a living organism. Volume Depletion and Dehydration:
    • ↓ K
    • ↓ Magnesium Magnesium A metallic element that has the atomic symbol mg, atomic number 12, and atomic weight 24. 31. It is important for the activity of many enzymes, especially those involved in oxidative phosphorylation. Electrolytes
    • ↓ Bicarbonate Bicarbonate Inorganic salts that contain the -HCO3 radical. They are an important factor in determining the ph of the blood and the concentration of bicarbonate ions is regulated by the kidney. Levels in the blood are an index of the alkali reserve or buffering capacity. Electrolytes
    • ↑ Creatinine
• Diagnostic testing:
  • Detection of the oocyst Oocyst Zygote-containing cysts of sporozoan protozoa. Further development in an oocyst produces small individual infective organisms called sporozoites. Then, depending on the genus, the entire oocyst is called a sporocyst or the oocyst contains multiple sporocysts encapsulating the sporozoites. Toxoplasma/Toxoplasmosis in the stool:
    • Thin-walled and ellipsoidal
    • Acid-fast positive (using modified acid-fast staining)
  • PCR PCR Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR) to detect Cystoisospora DNA DNA A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA Types and Structure
  • Intestinal biopsy Biopsy Removal and pathologic examination of specimens from the living body. Ewing Sarcoma showing parasites

Diagnosis of cyclosporiasis

• Detection of the oocyst Oocyst Zygote-containing cysts of sporozoan protozoa. Further development in an oocyst produces small individual infective organisms called sporozoites. Then, depending on the genus, the entire oocyst is called a sporocyst or the oocyst contains multiple sporocysts encapsulating the sporozoites. Toxoplasma/Toxoplasmosis in the stool: 
  • Modified acid-fast staining: pink or purple, round bodies 
  • Safranin stain: oocysts are red/reddish orange
  • Autofluorescence with fluorescence microscopy
• PCR PCR Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR) to detect Cyclospora DNA DNA A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA Types and Structure in stool

Management

Cystoisosporiasis management

• Usually self-limited in immunocompetent individuals
• Fluid and electrolyte replacement for dehydration Dehydration The condition that results from excessive loss of water from a living organism. Volume Depletion and Dehydration
• Nutritional support in cases of malnutrition Malnutrition Malnutrition is a clinical state caused by an imbalance or deficiency of calories and/or micronutrients and macronutrients. The 2 main manifestations of acute severe malnutrition are marasmus (total caloric insufficiency) and kwashiorkor (protein malnutrition with characteristic edema). Malnutrition in children in resource-limited countries
• Antimicrobial therapy:
  • Indications:
    • Immunocompromised immunocompromised A human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation. Gastroenteritis individuals
    • Immunocompetent individuals with persistent symptoms
  • Options:
    • Trimethoprim Trimethoprim The sulfonamides are a class of antimicrobial drugs inhibiting folic acid synthesize in pathogens. The prototypical drug in the class is sulfamethoxazole. Although not technically sulfonamides, trimethoprim, dapsone, and pyrimethamine are also important antimicrobial agents inhibiting folic acid synthesis. The agents are often combined with sulfonamides, resulting in a synergistic effect. Sulfonamides and Trimethoprim– sulfamethoxazole Sulfamethoxazole A bacteriostatic antibacterial agent that interferes with folic acid synthesis in susceptible bacteria. Its broad spectrum of activity has been limited by the development of resistance. Sulfonamides and Trimethoprim (TMP-SMX; 1st-choice)
    • Ciprofloxacin Ciprofloxacin A broad-spectrum antimicrobial carboxyfluoroquinoline. Fluoroquinolones 
    • Pyrimethamine Pyrimethamine One of the folic acid antagonists that is used as an antimalarial or with a sulfonamide to treat toxoplasmosis. Antimalarial Drugs plus leucovorin
    • Nitazoxanide
• Antiretroviral therapy Antiretroviral therapy Antiretroviral therapy (ART) targets the replication cycle of the human immunodeficiency virus (HIV) and is classified based on the viral enzyme or mechanism that is inhibited. The goal of therapy is to suppress viral replication to reach the outcome of undetected viral load. Anti-HIV Drugs for individuals with AIDS AIDS Chronic HIV infection and depletion of CD4 cells eventually results in acquired immunodeficiency syndrome (AIDS), which can be diagnosed by the presence of certain opportunistic diseases called AIDS-defining conditions. These conditions include a wide spectrum of bacterial, viral, fungal, and parasitic infections as well as several malignancies and generalized conditions. HIV Infection and AIDS
• Secondary prophylaxis Prophylaxis Cephalosporins to ↓ risk of relapse Relapse Relapsing Fever in immunocompromised immunocompromised A human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation. Gastroenteritis individuals: TMP-SMX

Cyclosporiasis management

Antimicrobials used for the treatment of cyclosporiasis include:

• TMP-SMX (1st-choice)
• Nitazoxanide
• Ciprofloxacin Ciprofloxacin A broad-spectrum antimicrobial carboxyfluoroquinoline. Fluoroquinolones

Differential Diagnosis

• Microsporidiosis Microsporidiosis Microsporidia are a group of obligate intracellular organisms that were recently reclassified as fungi. The most common species of Microsporidia is Enterocytozoon bieneusi. Microsporidia species are ubiquitous, with a wide range of reservoirs. Immunocompromised individuals (particularly those with AIDS and a CD4 count < 100 cells/µL) most commonly develop symptomatic microsporidiosis. Microsporidia/Microsporidiosis: caused by a group of obligate intracellular spore-forming organisms that were recently reclassified as fungi Fungi A kingdom of eukaryotic, heterotrophic organisms that live parasitically as saprobes, including mushrooms; yeasts; smuts, molds, etc. They reproduce either sexually or asexually, and have life cycles that range from simple to complex. Filamentous fungi, commonly known as molds, refer to those that grow as multicellular colonies. Mycology (formerly classified as protozoa Protozoa Nitroimidazoles). Microsporidia Microsporidia Microsporidia are a group of obligate intracellular organisms that were recently reclassified as fungi. The most common species of Microsporidia is Enterocytozoon bieneusi. Microsporidia species are ubiquitous, with a wide range of reservoirs. Immunocompromised individuals (particularly those with AIDS and a CD4 count < 100 cells/µL) most commonly develop symptomatic microsporidiosis. Microsporidia/Microsporidiosis most commonly affect immunocompromised immunocompromised A human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation. Gastroenteritis individuals (particularly those with AIDS AIDS Chronic HIV infection and depletion of CD4 cells eventually results in acquired immunodeficiency syndrome (AIDS), which can be diagnosed by the presence of certain opportunistic diseases called AIDS-defining conditions. These conditions include a wide spectrum of bacterial, viral, fungal, and parasitic infections as well as several malignancies and generalized conditions. HIV Infection and AIDS) and cause diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea and other disseminated infections Disseminated infections IL-12 Receptor Deficiency. The diagnosis is made by identifying organisms in stool, urine, secretions, or biopsy Biopsy Removal and pathologic examination of specimens from the living body. Ewing Sarcoma specimens. Management depends on the species and includes a wide range of antimicrobials.
• Gastroenteritis Gastroenteritis Gastroenteritis is inflammation of the stomach and intestines, commonly caused by infections from bacteria, viruses, or parasites. Transmission may be foodborne, fecal-oral, or through animal contact. Common clinical features include abdominal pain, diarrhea, vomiting, fever, and dehydration. Gastroenteritis: inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the stomach Stomach The stomach is a muscular sac in the upper left portion of the abdomen that plays a critical role in digestion. The stomach develops from the foregut and connects the esophagus with the duodenum. Structurally, the stomach is C-shaped and forms a greater and lesser curvature and is divided grossly into regions: the cardia, fundus, body, and pylorus. Stomach: Anatomy and intestines, commonly caused by infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease from bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology, viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology, or parasites. Most cases are viral. Common clinical features of gastroenteritis Gastroenteritis Gastroenteritis is inflammation of the stomach and intestines, commonly caused by infections from bacteria, viruses, or parasites. Transmission may be foodborne, fecal-oral, or through animal contact. Common clinical features include abdominal pain, diarrhea, vomiting, fever, and dehydration. Gastroenteritis include abdominal pain Abdominal Pain Acute Abdomen, diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea, vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia, fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, and dehydration Dehydration The condition that results from excessive loss of water from a living organism. Volume Depletion and Dehydration. Diagnostic testing with stool analysis or culture is not always required but can help determine the etiology in certain circumstances. Most cases are self-limited; therefore, the only required treatment is supportive therapy (fluids). 
• Cryptosporidiosis: infection with Cryptosporidium Cryptosporidium A genus of coccidian parasites of the family cryptosporidiidae, found in the intestinal epithelium of many vertebrates including humans. Hyper-IgM Syndrome. Individuals will have watery diarrhea Watery diarrhea Rotavirus, abdominal cramping Abdominal cramping Norovirus, nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics, and fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever that lasts 2–3 weeks, but the infection can be more persistent and severe in immunocompromised immunocompromised A human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation. Gastroenteritis individuals. Diagnosis is with identification Identification Defense Mechanisms of the organism in a stool specimen. Cryptosporidiosis is generally self-limited, but it may require nitazoxanide in persistent or severe cases.  
• Giardiasis Giardiasis An infection of the small intestine caused by the flagellated protozoan giardia. It is spread via contaminated food and water and by direct person-to-person contact. Giardia/Giardiasis: caused by Giardia Giardia A genus of flagellate intestinal eukaryotes parasitic in various vertebrates, including humans. Characteristics include the presence of four pairs of flagella arising from a complicated system of axonemes and cysts that are ellipsoidal to ovoidal in shape. Nitroimidazoles lamblia, a flagellated protozoan that can infect the intestinal tract. The hallmark symptom of giardiasis Giardiasis An infection of the small intestine caused by the flagellated protozoan giardia. It is spread via contaminated food and water and by direct person-to-person contact. Giardia/Giardiasis is foul-smelling steatorrhea Steatorrhea A condition that is characterized by chronic fatty diarrhea, a result of abnormal digestion and/or intestinal absorption of fats. Diarrhea. Individuals who develop chronic infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease may experience weight loss Weight loss Decrease in existing body weight. Bariatric Surgery, failure to thrive Failure to Thrive Failure to thrive (FTT), or faltering growth, describes suboptimal weight gain and growth in children. The majority of cases are due to inadequate caloric intake; however, genetic, infectious, and oncological etiologies are also common. Failure to Thrive, and vitamin deficiencies as a result of malabsorption Malabsorption General term for a group of malnutrition syndromes caused by failure of normal intestinal absorption of nutrients. Malabsorption and Maldigestion. The diagnosis is made through detection of Giardia Giardia A genus of flagellate intestinal eukaryotes parasitic in various vertebrates, including humans. Characteristics include the presence of four pairs of flagella arising from a complicated system of axonemes and cysts that are ellipsoidal to ovoidal in shape. Nitroimidazoles organisms, antigens, or DNA DNA A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA Types and Structure in the stool. Management includes supportive treatment and antimicrobial therapy with metronidazole Metronidazole A nitroimidazole used to treat amebiasis; vaginitis; trichomonas infections; giardiasis; anaerobic bacteria; and treponemal infections. Pyogenic Liver Abscess, tinidazole Tinidazole A nitroimidazole alkylating agent that is used as an antitrichomonal agent against trichomonas vaginalis; entamoeba histolytica; and giardia lamblia infections. It also acts as an antibacterial agent for the treatment of bacterial vaginosis and anaerobic bacterial infections. Nitroimidazoles, or nitazoxanide. 
• Traveler’s diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea: gastroenteritis Gastroenteritis Gastroenteritis is inflammation of the stomach and intestines, commonly caused by infections from bacteria, viruses, or parasites. Transmission may be foodborne, fecal-oral, or through animal contact. Common clinical features include abdominal pain, diarrhea, vomiting, fever, and dehydration. Gastroenteritis that is usually caused by bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology or viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology in the local water, such as enterotoxigenic Escherichia coli Escherichia coli The gram-negative bacterium Escherichia coli is a key component of the human gut microbiota. Most strains of E. coli are avirulent, but occasionally they escape the GI tract, infecting the urinary tract and other sites. Less common strains of E. coli are able to cause disease within the GI tract, most commonly presenting as abdominal pain and diarrhea. Escherichia coli (ETEC) or norovirus Norovirus Norovirus is a nonenveloped, single-stranded, positive-sense RNA virus belonging to the Caliciviridae family. Norovirus infections are transmitted via the fecal-oral route or by aerosols from vomiting. The virus is one of the most common causes of nonbacterial gastroenteritis epidemic worldwide. Symptoms include watery and nonbloody diarrhea, nausea, vomiting, and low-grade fever. Norovirus. Symptoms occur after consumption of contaminated water or food and include watery diarrhea Watery diarrhea Rotavirus, malaise Malaise Tick-borne Encephalitis Virus, and abdominal cramping Abdominal cramping Norovirus. The diagnosis is clinical, and the illness is self-limited.