Neglected Tropical Disease

measured in terms of years of healthy life lost – Disability Adjusted Life Years (DALYs) – 46-57 million DALYs lost / yr

• NTDs second only to HIV/AIDS; and higher than TB or malaria

• Overworked doctors

• Isolation, poor employment
• Young women – work and marital prospects

Education in children – school attendance and performance; future employment

Ascaris lumbricoides (roundworm)

Trichuris trichiura (whipworm)

Necator, Ancylostoma (hookworms)

Enterobius vermicularis (pinworm)

Strongyloides stercoralis

Leading infectious cause of blindness

Visual impairment or blindness in 1.9 million

190 million living in endemic area, at risk of trachoma blindness

Poorest and most rural areas

Public health problem in 41 countries

Africa, S. America, Asia, Australia, Middle East

Aetiology

Caused by Chlamydia trachomatis

• Direct contact with infected eye and nasal discharges

• Contact with contaminated fomites

Eye-seeking flies

Child-to-child (eg. classroom); child-to-mother

• Prevalence of 60-90% preschool children
• Poor hygiene, lack of clean water & proper sanitation, overcrowding, etc.

Repeated infections

• Scarring of eyelids
• Excoriation of cornea / conjunctiva by eyelashes
• Pain, photophobia, blindness typically by 30-40 yrs

• Deterioration in quality of life,
• Employment potential
• Females > males 4:1
  • Close contact with infected children

WHO SAFE strategy (since 1993):

• Surgery (to treat trichiasis);
• Antibiotic (azithromycin);
• Facial cleanliness;
• Environmental improvement (access to water & sanitation)

• About 0.4 million people affected
• 102 countries
• High endemicity: Brazil, Sri Lanka, etc

Caused by Mycobacterium leprae

disease is not highly contagious like the flu

• Not by skin, thought to be spread through infected droplets (nasal)

Disfiguring skin condition etc

Social stigmatisation:

isolation or marginalisation; unemployment; marital status, etc.

Strategy:

1. Diagnosis
2. Multi-Drug Therapy (MDT): rifampicin, dapsone, and clofazimine
3. WHO ‘Final Push’ strategy: to achieve prevalence of <1 per 10,000 population and eventual elimination

1. Ascaris lumbricoides (roundworm)
2. Trichuris trichiura (whipworm)
3. Necator, Ancylostoma (hookworms)

1. Enterobius vermicularis (pinworm)
2. Strongyloides stercoralis

• Warm humid areas; warmer mths in temperate zones
• Acquired via ingestion of infective (inactive) eggs

(activated in the host, gut)

• Pulmonary symptoms: cough, dyspnoea, wheeze, fever, eosinophilia

Mild: Asymptomatic or mild symptoms

• Abd discomfort, nausea, anorexia

Severe: malnutrition, intestinal obstruction, etc.

(because of the big mass of worm)

Trichuriasis primarily affects children in developing regions of tropics / subtropics

Geographical distribution similar to A. lumbricoides

Light infections: may be asymptomatic

Chronic heavy infection:

• abd pain, diarrhoea, blood in faeces, iron-deficiency anaemia, growth retardation

• Ingestion; feces (soil)

Infection occurs mainly in tropics/subtropics

Up to a third of pregnant women in sub-Saharan Africa affected by hookworms

Impact

Iron-deficiency anaemia & growth retardation are significant long-term consequences

Low-birth weight babies; poor milk production; failure to thrive in babies

Increased mortality: pregnant women with anaemia 3.5x more likely to die during childbirth than non-anaemic women

• Pruritic maculopapular rash (‘ground itch’) associated with larval penetration of skin

• Transient pneumonitis associated with larval migration through lungs

Chronic light: usually asymptomatic

Heavy infections: malabsorption (hookworms located mainly in small intestines)

• Iron-deficiency anaemia; malnutrition; chronic abd pain, eosinophilia

• “hooks” into skin, from Feces (soil),

Microscopy

• Visualisation of eggs or worms on microscopy
• Ascaris adult worm 15-35 cm
• Trichuris worm 4-5 cm; characteristic ‘whip-like’ tail

• Treatment of Ascaris/Trichuris/hookworms:
  • Drugs: mebendazole or albendazole

• Prevention:
  • safe drinking water, proper food prep, hand washing, shoes,
  • adequate sanitation and waste management, etc.

1. Periodic preventive chemotherapy for children & women of childbearing age & adults in high-risk occupations in areas with STH prevalences of >20%
2. WHO target to treat >75% children in endemic countries by 2020
   1. 2014: >270 million school children treated (47% children at risk

1. Health & hygiene education to communities
2. Improve sanitation to reduce soil contamination of eggs

Dracunculus medinensis:

found mostly in tropical regions of Africa; now endemic only in four African countries

Caused by Dracunculus medinensis

Carried in water fleas

• Ingestion of unsafe water (containing water fleas Cyclops spp.)
• Blister burst → Worm exposes → Lays eggs → transmitted

Often no clinical signs until worm is ready to discharge larvae (1 yr)

• Papule → Ulceration → Discharge

• ‘Disease of empty granary’ (Mali)

(Since the peak transmission period often coincides with the agricultural season, fields are left untended and food production level goes down)

Strategy:

Surveillance and mapping structure for all endemic villages

Case containment measures: wound care, education re: avoidance of contact with water

Safe water supplies (eg. filtration, even with finely woven cloth); education of community re: preventative measures

Vector control of unsafe water sources eg. insecticide temephos

Reporting and certification system for eradication country by country

Favourable factors for eradication

Easily recognisable clinical features (diagnosis)

• Intermediate host (Cyclops water fleas) restricted to stagnant waters only (compared to airborne hosts like mosquitoes for some infections)
• Limited geographical distribution
• Simple cheap interventions; easy to implement
• Political commitment

Insecticide to unsafe water sources

• Progressive rolling of emerging worm onto stick

Thiabendazole: no effect on adult worm but may reduce inflammation

Dramatic fall in prevalence after global effort in health education and access to safe water supplies:

• >3.5 million in 1986 (20 countries);
• <5,000 cases in 2007 (6 countries);
• 542 cases in 2012 (4 countries);
• 126 in 2014

Chad: unusual epidemiology in dogs with emerging worms

• Fishing villages along Chari river
• Access to fish entrails

2016: >1000 dogs in Chad with emerging worms

• First case of dracunculiasis reported in Angola in 2018