Ascariasis

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Organism, Causative agent, Etiologic agent
Ascariasis is caused by the intestinal nematode Ascaris lumbricoides belonging to a class of parasites often referred to as “soil-transmitted helminths”.

Transmission
Transmission is primarily via the fecal-oral route. Eggs are shed in an infected person’s feces but require exposure to a warm, moist, soil environment to mature and become infectious. Once the eggs have incubated in soil they can be transmitted via contaminated water, agriculture products, fingers, or other fomites. Human to human transmission of Ascaris species does not occur.

Symptoms
Most infections with Ascaris spp. are asymptomatic. Heavier infections may result in gastrointestinal issues, malnutrition, and/or intestinal obstruction. Severe infections in children may result in nutrient deficiencies leading to growth retardation and cognitive impairment. During larval migration through respiratory passages, acute transient pneumonitis and eosinophilia may occur. Adult worms may migrate under stressful conditions (fever, anesthesia etc.) which may lead to intestinal wall perforation, appendicitis, peritonitis, pancreatitis, cholangitis or biliary colic. In very rare instances, intestinal obstructions may cause gangrene and if untreated result in death.

Prevention
The best method for prevention of ascariasis is proper disposal of human waste.  Avoiding the use of human waste-based fertilizer (night soil) will also decrease the risk of transmission. Thoroughly washing hands and all produce before cooking and eating is also highly recommended in order to prevent ingestion of parasite eggs.

Texas Trends
Ascariasis became a reportable condition in 2016. The average annual case count from 2016 to 2020 is 12.8, ranging between 6-19 cases per year.