Ascariasis overview

# Overview
Ascariasis is a globally occurring helminthic infection of humans. It is the most common human helminth infection. The transmission of infection is usually from hand to mouth, and humans are the only known host. Ascariasis is more common in tropical areas of the world and predominantly affects the pediatric age group.

# Historical Perspective
Ascariasis has been around for several years and the scientific study of Ascaris lumbricoides was promoted by Edward Tyson.

# Pathophysiology
The transmission of infection is usually from hand to mouth, and humans are the only known host. Following ingestion of infective eggs, larvae hatch and invade the intestinal mucosa. The larvae are carried via the portal, then systemic circulation to the lungs. The larvae mature further in the lungs, penetrate the alveolar walls, and ascend the bronchial tree to the throat. The larvae are then swallowed. Upon reaching the small intestine, they develop into adult worms. The adult worms can live for 1 to 2 years.

# Causes
Ascariasis is a soil helminth infection caused by the nematode Ascaris lumbricoides.

# Differentiating Ascariasis from other Diseases
Ascariasis can mimic other worm infections, and also gastrointestinal pathologies like peptic ulcer disease, intussusception in children, bile duct stone, etc.

# Epidemiology and Demographics
Ascariasis affects at least 1 billion people worldwide and about 4 million people in the United States. It is more common in the pediatric age group (ages 2-10 years). Ascariasis is three times more common in African-Americans compared to Caucasians.

# Risk factors
The risk factors for ascariasis are often associated with poor sanitary conditions and environmental fecal contamination.

# Natural History, Complications and Prognosis
Ascariasis is often asymptomatic and more than 80% of infected individuals experience minimal or no symptoms of the disease. Complications may arise when adult worms move to certain organs such as the bile duct, pancreas, or appendix. A high worm burden can also result in complications such as intestinal obstruction. The prognosis is good as most cases of ascariasis are asymptomatic, but mortality can sometimes be as high as 60,000 per year. Mortality from ascariasis is usually as a result of complications from the infection, approximately 4.6% of patients hospitalized with complications of ascariasis die from the infection.

# History and Symptoms
Ascariasis is often asymptomatic. It can sometimes present with mild pulmonary and abdominal symptoms such as cough, dyspepsia, and nausea. However, severe cases of ascariasis occasionally occur especially following mechanical obstruction of a viscus.

# Physical Examination
The physical examination findings in ascariasis vary and it is usually dependent on the worm burden and the involved organ. Abdominal tenderness can occur secondary to intestinal obstruction, appendicitis, biliary colic, acute cholangitis, acute cholecystitis, hepatic abscess, etc.

# Laboratory Findings
Ascariasis is frequently diagnosed in the laboratory via microscopic identification of eggs in the feces.

# Chest and Abdominal X-ray
A chest x-ray can reveal varying sizes of oval or round infiltrates (Loffler's syndrome). These infiltrates usually resolve spontaneously. Plain abdominal radiographs and contrast studies can reveal worm masses in bowel loops.

# CT
CT scan with contrast can reveal foreign bodies such as worms in the gastrointestinal tract.

# Ultrasound
Ultrasonography can reveal worms in the biliary tree,  pancreatic duct and bowel loops.

# Other Diagnostic Studies
Imaging studies such as endoscopic retrograde cholangiopancreatography (ERCP) can identify worms in the pancreaticobiliary tract.

# Medical Therapy
All ascariasis infection (symptomatic and asymptomatic) should be treated with antimicrobial therapy. Due to the high rate of reinfection, it is sometimes necessary to repeat antimicrobial therapy. Antimicrobial therapy with albendazole is usually the treatment of choice for ascariasis, although other antihelminthic medications can effectively eradicate the parasite.

# Surgery
Ascariasis is usually managed conservatively with medical therapy but surgery may be indicated when medical management fails or complications arise. Some of the indications for the surgical management of ascariasis include complete intestinal obstruction with inadequate decompression, complications such as volvulus, intussusception or intestinal perforation, acute appendicitis, worms trapped in ducts, etc.

# Prevention
The prevention of ascariasis is best achieved through improvements in personal hygiene and environmental sanitation.