Epidemiology of Schistosoma Hematobium Flashcards
What is epidemiology?
the study of the distribution and determinants of health-related states or events (including disease), and the application of this study to the control of diseases and other health problems
What is schistosomiasis?
An acute and chronic, parasitic disease caused by blood flukes/trematode worms of the genus Schistosoma.
Infections causing illness in humans are with?
- Schistosoma mansoni,
- S. haematobium,
- S. japonicum,
- S. guineensis
- S. mekongi and S. intercalatum
- less commonly can cause disease.
Which species causes intestinal schistosomiasis?
S. mansoni
Which species causes urogenital schistosomiasis?
S. haematobium
Describe the signs and symptoms in the early phase of infection of schistosomiasis?
- Rash or itchy skin within days after infection
- Fever, chills, cough, and muscle aches can begin within 1-2 months of infection.
- Most people have no symptoms at this stage
Describe the signs and symptoms in the late phase of infection of schistosomiasis?
Symptoms are caused by body’s reaction to the eggs produced by worms
- Eggs from adult worms travel to the intestine, liver or bladder, causing inflammation or scarring
- Damage to the liver, intestine, lungs, and bladder.
- Rarely, eggs are found in the brain or spinal cord and can cause seizures, paralysis, or spinal cord inflammation.
- Female genital schistosomiasis
Children who are repeatedly infected by schistosomiasis can develop?
- anemia
- malnutrition
- learning difficulties
Describe the signs and symptoms of S. haemotobium?
include urogenital symptoms & signs:
- Cystitis
- Ureteritis with hematuria,
- Bladder cancer
- Glomerulonephritis and
- Central nervous system lesions e.g. transverse myelitis with flaccid paraplegia
How do you diagnose SH?
Use samples of urine
1. Color – blood urine
2. Examined for the presence of eggs
– using the filtration technique for SH
Describe the global burden and distribution of SH?
- Schistosomiasis transmission reported in 78 countries
- Only 51 countries with moderate-to-high transmission require large scale treatment in communities
- Affects 240 million people worldwide
- At least 206 million people were infected or required treatment in 2018
- At least 91.4% of those requiring treatment for schistosomiasis live in Africa
- WHO estimates the annual death rate at 200 000 globally
Describe the geographical distribution of S. mansoni?
parts of South America (Brazil and Venezuela) and the Caribbean, Africa, and the Middle East
Describe the global geographical distribution of S. haemotobium?
Africa and the Middle East and Corsica (France)
Describe the global geographical distribution of S. japonicum?
Far East
China, Indonesia, the Philippines
Describe the global geographical distribution of S. mekongi?
Southeast Asia and Several districts of Cambodia and the Lao People’s Democratic Republic
Describe the global geographical distribution of S. intercalatum?
Central West Africa
Describe the transmission and prevalence of SH?
- Transmission in Malawi is highly focal, with considerable variation in space and time
- National prevalence of S. haematobium
~6.9% (95% CI 1.9 - 11.9%) - prevalence rates of up to 94.9% for Schistosoma haematobium in some communities
Seasonality of transmission of SH varies by?
geographical, environmental, biological and behavioural factors.
How are people infected by SH?
during routine agricultural, domestic, occupational, and recreational activities, which expose them to infested water
Describe the determinants and risk factors of SH with regards to populations and the environment?
Populations in frequent contact with infected sources
1. Mostly affects poor and rural communities
2. Agricultural and fishing populations
– E.g along the Lake Malawi or rivers
3. Women doing domestic chores in infested water
4. Children (SAC) vulnerable to infection
– frequent contact with infested waters
5. Migration to urban areas /population
movements introduce disease to new areas
6. Development schemes , dams
7. Tourists to infected areas
What are the public health interventions for prevention and control of SH?
- Large-scale treatment of at-risk population groups (preventive chemotherapy)
- Access to safe water
- Improved sanitation
- Hygiene education
- Snail control
Describe the large scale treatment of at risk population groups (preventative chemotherapy)?
– Repeated over a number of years in a
community, will reduce and prevent morbidity.
– Targets all who are at-risk
– WHO strategy for control focuses on reducing disease morbidity through periodic, targeted treatment with praziquantel.
Describe the epidemiology of large scale treatment of at risk population groups?
In 2019 - at least 236.6 million people required preventive treatment for schistosomiasis - more than 105.4 million people were reported to have been treated
The groups targeted for treatment of SH are?
- School-aged children in endemic areas.
- Adults considered to be at risk in endemic areas
- people with occupations involving contact with infested water, such as fishermen, farmers, irrigation workers
- women whose domestic tasks bring them in contact with infested water.
- Entire communities living in highly endemic areas
Which drug is used to treat SH?
Praziquantel is the recommended treatment
against all forms of schistosomiasis.
• It is effective, safe, and low-cost
What are the public health interventions for prevention and control of SH?
- Access to safe water
- Improved sanitation
- Hygiene education
- Snail control
- Praziquantel
Describe some of the challenges for SH control?
- Need for integrated approach to the
control, other aspects not adequately done
- Poverty
- Access to safe water / Improved sanitation - Inadequate behavioural change
- Lack of praziquantel in other countries
- Lack of better methods for snail control
