Neglected Tropical Diseases and Helminthic Infections Flashcards
What are neglected tropical diseases?
- Disease preventable and treatable
- Affect poor, vulnerable populations living in hard to reach places
The world wide the top 5 neglected tropical diseases are?
- Lymphatic filariasis
- Onchocerciasis
- Schistosomiasis
- Soil-transmitted helminths
- Trachoma
Lymphatic filariasis
Lymphatic filariasis, considered globally as a neglected tropical disease (NTD), is a parasitic disease caused by microscopic, thread-like worms. The adult worms only live in the human lymph system. The lymph system maintains the body’s fluid balance and fights infections.
Parent Disease: Parasitic disease
Vector: Mosquitoes
Onchocerciasis
Onchocerciasis, also known as river blindness, is a disease caused by infection with the parasitic worm Onchocerca volvulus. Symptoms include severe itching, bumps under the skin, and blindness. It is the second-most common cause of blindness due to infection, after trachoma.
Causes: Onchocerca volvulus spread by a black fly
Symptoms: Itching, bumps under the skin, blin…
Other names: River blindness, Robles disease
Specialty: Infectious disease
Schistosomiasis
Schistosomiasis, also known as bilharzia, is a disease caused by parasitic worms. Although the worms that cause schistosomiasis are not found in the United States, people are infected worldwide. In terms of impact this disease is second only to malaria as the most devastating parasitic disease.
Soil-transmitted helminths
Soil-transmitted helminths refer to the intestinal worms infecting humans that are transmitted through contaminated soil (“helminth” means parasitic worm): Ascaris lumbricoides (sometimes called just “Ascaris“), whipworm (Trichuris trichiura), and hookworm (Anclostoma duodenale and Necator americanus).
Trachoma
Trachoma is a disease of the eye caused by infection with the bacterium Chlamydia trachomatis. Blindness from trachoma is irreversible. It is a public health problem in 44 countries, and is responsible for the blindness or visual impairment of about 1.9 million people.09 May 2021
Causes: Chlamydia trachomatis
Diseases or conditions caused: Blindness
The burden of Neglected tropical disease.
> 1.5-billion people (24% of the world’s population)
40% live in Africa
> 7 countries have been validated as having eliminated one of the five diseases
2 are from Africa (Morocco [trachoma, 2016] and Togo [lymphatic filariasis, 2017]
WHO strategies recommended to address neglected tropical diseases
Community-based surveys for mapping or monitoring and evaluation purposes are core activities of NTD programmes
- Preventive chemotherapy
- Individual care management
- Vector control
- Veterinary public health
- Water, sanitation and hygiene
Considerations during the covid-19 pandemic
> Temporary suspension of community-based surveys, mass treatment and active case finding
> Community-based vector control and veterinary public health interventions should continue with strict precautions
:hand hygiene, respiratory etiquette, physical distancing
Treatment targets for neglected tropical diseases
- 65% and above for lymphatic filariasis and Onchocerciasis
- 75% and above for Schistosomiasis in school-aged children
- 75% and above for soil-transmitted helminths in school-age and pre-school children
- 80% and above for trachoma
In South Africa, the most common NTDs are?
In SA, the most common NTDs include infection with the soil-transmitted helminths - Ascaris lumbricoides, Trichuris trichiura, Necator americanus, Enterobius vermicularis - and the less prevalent but common Strongyloides and Taenia spp. and Schistosoma haematobium and S. mansoni.
Soil-transmitted helminths and
Schistosomiasis
What is a helminth?
- derived from the Greek helmins :“parasitic worm”
- Exist as free-living organisms or as parasites of plant or animal hosts
- Nemathelminthes: e.g. nematodes (roundworms)
- Platyhelminthes e.g. cestodes (tapeworms) and trematodes (flukes)
Helminthic parasites?
Helminthic parasites are multicellular worms
Complex life cycles with stages of development outside the human host
Soil-transmitted helminths
> Roundworm (Ascaris lumbricoides)
Whipworm (Trichuris trichiura)
Hookworm (Anclostoma duodenale and Necator americanus)
The epidemiological triad of the soil-transmitted helminthic infections
- Host: human
- Age, gender, behavior, immune status, nutritional status
- Agent: roundworm, whipworm, hookworm
- Mode of transmission
- Life cycle
- Environment
- macroclimate, microclimate (eg. housing), water and sanitation
Transmission of Soil-transmitted helminths
Contact with eggs that are passed in the faeces of infected people
Adult worms live in the intestine where they produce thousands of eggs each day
In areas that lack adequate sanitation, these eggs contaminate the soil
Roundworm
infection with roundworm is called: Ascariasis
- Ascaris lumbricoides
- Most common parasites found in gut of children
- Pink and smooth
- ≈ 25 cm long
- Look like pale garden earthworms
- Common in children between ages of 1 and 5 years
- produce thousands of eggs a day - passed in child’s stool
- eggs have a characteristic shape, easily recognized under a microscope
- 5 developmental stages: an adult stage and 4 sequential larval stages
The life cycle of the Roundworm
- Roundworm eggs hatch in the child’s small bowel and the newly hatched larvae then pass through the bowel wall into the bloodstream and are carried to the alveoli of the lungs.
- From here they make their way up the bronchi and trachea then get swallowed.
- In the small bowel the roundworm larvae mature into adult worms where they can live for 2 years.
Roundworm infection symptoms
> Often asymptomatic
Younger children more likely to have symptoms:
- Worms in a bowel movement or coming out of the nose or mouth
- Stomach pain
- Coughing
- Loss of appetite
- Fever
- Wheezing
- Weight loss or failure to grow
Whipworms
Trichuris trichiuria
short, thin worms (about 4 cm)
attach to mucosa of large bowel cause bleeding
rare to see worms in stool
unlike roundworms, larvae do not migrate through the lungs
The life cycle of Whipworm
-When embryonated eggs ingested –> digestive system, larvae hatch in the small intestine and you will find adult worms in cecum
Whipworms symptoms
- Usually infect children over 5 years of age
- If the infection is light, usually no symptoms or signs
Heavy infection:
- Loose stools containing blood
- Rectal prolapse may occur; worms may be seen attached to the rectal mucosa
- Iron deficiency anemia due to chronic blood loss in the stool
- Malnutrition
Hookworms
Ancylostoma duodenale and Necator americanus
common in warm, moist climates e.g. northern KZN, Mozambique coast
eggs in stool contaminate soil, hatch rapidly
infect feet of barefoot children
Once skin penetrated, hookworms behave like roundworms enter bloodstream, travel via lungs to get into small bowel
attach to bowel mucosa and cause bleeding
≈ 1cm long
The life cycle of Hookworm
Via penetrating the skin [steps on infected poop] and enters the body, the respiratory tract and into the intestine.
Hookworms symptoms
- Usually no symptoms unless heavy infection
- Unusual increase in appetite
- May want to eat sand
- Iron deficiency anaemia in severe cases
Host [vulnerable populations]
Young children
Adolescent girls
Women of childbearing age
Risk factors
-Host:
>Malnutrition
>Poor hygiene
>Food that has not been cooked thoroughly
-Environment: poor sanitary conditions, poor access to running water
The burden of disease of these worm infections in South Africa
Not routinely collected data Not one of the indicators on the DHIS Data from studies: 120 households in eThekwni KZN A. lumbricoides [roundworm] (59%), T. trichiura (48%)
Management
> Primary prevention:
-address the social determinants: adequate water supply and sanitation
- health and hygiene education
/washing raw vegetables before they are eaten
/washing hands before preparing or eating meals
/preventing children from eating soil
and also Periodic de-worming to at-risk population
Treatment
Treatment : Mebendazole or Albendazole
Important that the whole family is treated simultaneously to prevent re-infection.
Treat other co-morbidities like iron deficiency and anemia
Global Targets for Soil-transmitted Helminth(iases) by 2030
- Achieve and maintain elimination of STH morbidity in pre-school and school-age children
- Reduce the number of tablets needed in preventive chemotherapy for STH
- Increase domestic financial support to preventive chemotherapy for STH
- Establish an efficient STH control programme in adolescent, pregnant and lactating women
- Establish an efficient strongyloidiasis control programme in school-age children
- Ensure universal access to at least basic sanitation and hygiene by 2030 in STH-endemic areas
Treatment coverage: SA
Increased from 43% in 2017 to 54% in 2018
Pre-school and school-aged children needing [prophylactic treatment] treatment: 15.83m
receiving treatment: 8.55m
