Intestinal Parasites: Ascariasis and Whipworm Quiz

Soil Transmitted Helminthiasis (STH)

• STH is a group of parasitic nematode worms
• These infections are common in deprived communities worldwide
• The worms thrive in warm, moist soil of tropical and subtropical regions
• Transmission occurs via contact with parasite eggs or larvae
• Infection is commonly co-endemic in areas with poverty and poor sanitation
• Children are most commonly affected

Types of Soil-Transmitted Helminths

• Nematodes (complete developmental stages in humans, require soil for transmission)
• Ascaris lumbricoides
• Trichuris trichiura
• Hookworms: Necator americanus and Ancylostoma duodenale
• Strongyloides stercoralis

Global Prevalence

• Ascaris lumbricoides infects over 1 billion people
• Trichuris trichiura infects 795 million people
• Hookworms (Necator americanus and Ancylostoma duodenale) infect 740 million people
• Highest numbers of infections in sub-Saharan Africa, the Americas, China, and East Asia

Mode of Transmission

• Infections result from ingestion of eggs from contaminated soil
• Transmission also happens through active penetration of the skin by larvae in soil
• Soil-transmitted helminths usually need 2-3 weeks in soil to become infectious
• People infected with STHs have parasite eggs in their faeces
• Transmission happens in areas without latrines, contaminating soil and water.

Route of Infection (Oral Transmission)

• Ascaris lumbricoides and Trichuris trichiura
• Larvae ingest eggs from contaminated vegetables not cooked, washed or peeled.
• Ingestion of eggs from water sources also possible.
• Children playing on the ground, putting their hands in their mouths, are susceptible.

Route of Infection (Skin Penetration)

• Hookworms and Strongyloides stercoralis
• Eggs hatch into larvae in the soil
• Transmission via larvae penetrating the skin, usually between toes.

Epidemiology

• Climate is critical for transmission; adequate moisture and warm temperatures are crucial for larval development.
• Poverty, inadequate water supplies, and poor sanitation are also significant factors.
• Soil-transmitted helminth species are commonly co-endemic in areas with these conditions.

Prevalence in Different Communities

• Prevalence data presented in percentages
• Urban slum communities exhibit a high prevalence rate compared to other groups. (Details in the text)

Clinical Manifestation

• STH infections are often asymptomatic (5-10 worms typically)
• Heavy infections can lead to nutritional deficiency, abdominal pain, intestinal obstruction, and various complications
• Lung migration of larvae can cause asthma, eosinophilia or other allergic reactions in severe instances

Host-parasite Interactions

• Soil-transmitted helminths are resistant to host immune responses
• Even with strong immune reactions, infections persist for life
• Intensity of infection (e.g., hookworm) may increase with the host's age.
• Worms may actively suppress the host's immune system

Control and Prevention

• Control strategies focus on treating once or twice a year
• Target groups include preschool and school-age children, women of childbearing age (including pregnant and lactating women), and adults at high risk (e.g., tea-pickers, miners).

Ascaris lumbricoides

• Largest intestinal roundworm causing ascariasis
• Adult female (20-35 cm), male (10-25 cm).
• Fertilized egg is broadly oval (45-75 x 35-50 μm).
• Thick shell, with brown bile-stained outer covering (albumin layer).

Ascaris lumbricoides Lifecycle

• Ingested embryonated ova hatch in the small intestine.
• Larvae penetrate intestinal wall and migrate to the liver, right heart, and lungs.
• Larvae pass to the trachea and pharynx
• Larvae swallowed, mature and mate in the small intestine.
• Fertilized ova pass in feces to become infectious within 2 weeks

Trichuris trichiura

• Also known as whipworm.
• Long, slender, thread-like anterior portion, thicker posterior portion resembling a whip handle.
• Adult worm (30-50 mm), male with a coiled tail and spicule
• Oval (barrel-shaped), bile-stained eggs with thick shell and a clear polar plug at each end(45-55 μm × 20-23 μm)

Trichuris trichiura Lifecycle

• Direct life cycle, after passage in feces
• Eggs take 2 weeks to mature in soil
• Ingested and develop in the large intestine.
• No lung migration
• Worm attaches to intestinal mucosa and takes 3 months for adult to lay eggs
• Whipworm is globally distributed.

Other Notes

• The report noted that the greatest burden of infectious diseases in children aged 5-14 in developing countries is caused by soil-transmitted helminth infections.
• Deworming school-aged children is an economically efficient public health approach
• Sanitation and personal hygiene are crucial for prevention
• Avoid using feces as fertilizer
• Common drugs for treatment include Mebendazole and Albendazole.
• Standard lab methods for diagnosis including microscopy are used for feces samples.

Test your knowledge on intestinal parasites, specifically focusing on ascariasis and Trichuris trichiura. This quiz covers their life cycles, complications of infections, common medications for treatment, and preventive measures. See how well you understand these important topics in parasitology.