Schistosomiasis Flashcards
(39 cards)
1
Q
What is Schistosomiasis?
A
Schistosomiasis, also known as bilharzia, is a disease caused by parasitic worms. Schistosomiasis ranks second to malaria as the most common parasitic disease in Africa.
2
Q
Two forms of Schistosomiasis:
A
There are two forms of the disease namely:
I) intestinal schistosomiasis caused by Schistosoma mansoni and S. japonicum, and
II) urinary schistosomiasis caused by S. haematobium.
- Infection with Schistosomes may present as an acute infection or as a chronic disease.
3
Q
Alternate names for Schistosomiasis.
A
Bilharziasis, bilharzia, bilharziosis, and snailfeveror, in the acute form, Katayamafeverare alternate names for schistosomiasis.
4
Q
A parasitic disease caused by flukes (trematodes) of the genusSchistosoma.
A
Schistosomiasis
5
Q
The 5 main species of Schistosomiasis
A
- Schistosoma Mansoni [lateral spine]
- Schistosoma Japonicum
- Schistosoma Mekongi
- Schistosoma Intercalatum
- Schistosoma Haematobium [terminal spine]
6
Q
What are the RISK FACTORS for Schistosomiasis?
A
- Wading or swimming in lakes, ponds, and other bodies of water that are infested with snails.
- Finishing [both men and women]
- Women washing clothes in infested water are at risk
- People with STIs
7
Q
The life cycle of Schistosomiasis
A
- Parasite eggs are released by way of urine or defecation into the environment from infected individuals.
- The eggs hatch on contact with fresh water to release the free-swimming miracidium
- Miracidium penetrates a water snail tissue where it develops into cercaria
- Cercaria is release into the water from the snail
- Cercaria penetrates the skin of human (definitive host), circulates to organs (GIT, urinary tract)
8
Q
Migratory phase
A
- Occurs when cercariae penetrate the skin
- Often asymptomatic
9
Q
Acute Schistosomiasis
A
- Mild, maculopapular skin lesions may develop in acute infection within hours after exposure to cercariae.
- Significant dermatitis is rare with the major human schistosomal pathogens, probably because the invading and developing cercariae are minimally immunogenic.
10
Q
Acute Schistosomiasis (Katayama syndrome)
A
- Systemic, serum sickness-like illness that develops after several weeks in some, but not most, individuals with new schistosomal infections.
- Associated with marked peripheral eosinophilia and circulating immune complexes.
- It is most common withS japonicumandS mansoni infections and is most likely to occur in heavily infected individuals after primary infection.
- Symptoms usually resolve over several weeks, but the syndrome can be fatal.
11
Q
Chronic Schistosomiasis
A
- Results primarily from host responses to eggs retained in tissues.
- Early on, intestinal mucosal ulcerations caused byS. mansoniorS. japonicummay bleed and result in bloody diarrhea.
- As lesions progress, focal fibrosis, strictures, fistulas, and papillomatous growths may develop in the intestine.
- Granulomatous reactions to eggs ofS. mansoniandS. japonicumin the liver usually do not compromise liver function, but they may cause fibrosis and cirrhosis, which can lead toportal hypertension, resulting insplenomegaly, and esophageal varices. Esophageal varices may bleed, causing hematemesis.
12
Q
> Chronic schistosomiasis is far more common than the acute form of the infection.
It results from:
A
Eggs in the lungs may produce granulomas and focal obliterative arteritis, which may ultimately result inpulmonary hypertensionandcor pulmonale.
- Egg-induced immune response
- Granuloma formation
- Associated fibrotic changes
13
Q
> Chronic intestinal Schistosomiasis can present with: BAP
A
- Bleeding
- Acute complications of appendicitis
- Perforation
14
Q
Schistosoma Haematobium
A
S. haematobium infection also associated with an increased rate of bladder cancer, usually squamous cell rather than transitional cell.
- Egg retention and granuloma formation in the urinary tract (S. haemobium) can lead to:
- Hematuria
- Dysuria
- Bladder polyps and ulcers
- Obstructive uropathies
15
Q
Ectopic egg deposition can lead to additional clinical syndromes, including involvement: SLAB GEM
A
- Skin
- Lungs
- Adrenal glands
- Brain
- Genitalia
- Muscles
16
Q
CNS involvement can result in:
A
- Transverse myelitis [best described for Haematobium and Mansoni]
- Cerebral disease [most common with Japonicum]
17
Q
Epidemiology of Schistosomiasis
A
- Over 290 million people required treatment in 2018
- More than 207 million people in at least 74 countries have active schistosomal infection.
- Of this population, approximately 60% have disease symptoms, including organ-specific complaints and problems related to chronic anaemia and malnutrition from the infection; more than 20 million are severely ill.
18
Q
is found in 10 countries within the rain forests of central Africa.
A
S intercalatum, S japonicum,andS mekongi
19
Q
Gender and Schistosomiasis
A
- Schistosomiasis is more common in males, most likely because of increased exposure to infected water via bathing, swimming, and agricultural activities.
- S haematobiumcauses genital lesions in 30% of women who are infected.
- Vulval lesions may increase the risk of HIV transmission.
20
Q
Age related demographics
A
- The prevalence and severity of schistosomal infections vary with age.
- Children and adolescents are infected most often and are infested most heavily.
- Infection rates and severity may vary with gender-specific activity at all ages.
- Globally, infections peak in individuals aged 10-19 years. In some areas, the prevalence in this group may approach 100%.
- In persons older than age 19 years living in endemic areas, the prevalence of active infection and egg counts slowly declines.
21
Q
History of Schistosomiasis in South Africa
A
- The first record of urogenital schistosomiasis in South Africa was in 1863.
- Dr J Harley, a general practitioner in Port Elizabeth, diagnosed boys from Uitenhage in the Eastern Cape with schistosomiasis.
- Case reports between 1864 and 1899 revealed how children, mostly boys between the ages of 3 and 16, were infected with schistosomiasis in the Eastern Cape.
22
Q
Scistosomiasis in South Africa
A
- Transmission among the boys was as a result of recreational swimming, contact with infested water in open pools, farm dams and furrows.
- The most common symptom was haematuria.
- In the 1920s and 1930s, the wide spread of schistosomiasis in South Africa and negative consequences of the disease, particularly in children.
23
Q
Epidemiology of Schistosomiasis in SA
A
- Schistosoma haematobium -areas extending from Uitenhage in the Eastern Cape, northwards through the eastern coastal belt and into the coastal and midland parts of KwaZuluNatal.
- However, this parasite does not appear in the mountainous regions of the Drakensberg nor is it found south of the Magaliesberg (in what is now Gauteng), Lesotho, Free State or the Western Cape
- Schistosoma mansoni is found mainly in Mpumalanga and the Limpopo Province, in central Gauteng, the low-lying parts of Swaziland and coastal regions of KwaZulu-Natal
- Bilharzia affect approximately four million people in South Africa especially school-going children.
24
Q
Population impact/Public Health Issues
A
- School-aged children, teenagers, women and young adults are mostly hit with the morbidity and mortality associated with schistosomiais.
- Schistosomiasis can cause growth retardation, fatigue, weakness, impairment of memory and cognitive reasoning, and increased risk ofanaemia, leading to poor academic performance, thus limiting the potential of infected children.
- These negative outcomes in children add to the socioeconomic burden of the society.
25
Population impact
- Iron deficiency is also an outcome of the disease sequel to nutritional impairment such as nutrient malabsorption and digestive disorder like diarrhoea.
- Urogenital schistosomiasis is a key predisposing agent for Human Immunodeficiency Virus (HIV) transmission.
- Urogenital schistosomiasis in HIV-infected women increases the ease of transmission to male sexual partners, as well as transmission from an HIV-infected male to his sexual partner.
- It also hastens the progression of the disease in people already infected with the virus by increasing the plasma concentration of the HIV RNA (viral load)
26
Other Public Health Issues
- Climate change- local infection and geographical expansion is influenced by climatic changes and global warming.
- Proximity to water sources- Estimated 76% of the sub-Saharan population live close to various open water bodies which are infested with the intermediate snail host necessary for the transmission of the disease.
- Man-made ecological changes- Ecological changes due to man-made construction of irrigation schemes, reservoirs, and dams for agricultural purposes and electricity generation are also responsible for the continued transmission of schistosomiasis.
- Socio-economic factors- poverty occupational activities, poor sanitation and hygiene, and non-availability of potable water for domestic use.
27
Treatment of Schistosomiasis
Drug: Prazequnatel
Dose:40mg/kg single oral dose
60mg/kg in 2 divided doses is quantity of ova is high. [Review in 2 weeks]
The Aim of the treatment:
- Reversing acute or early chronic disease
- Preventing complications associated with chronic infection
- Preventing neuroschistosomiasis.
>The goal of treatment is reduction of egg production via reduction of worm load; this reduces morbidity and mortality even in the absence of complete worm eradication. [just as long as we reduce the number of worms in the body]
28
!!Complications include!!
- GIT bleeding
- GI obstruction
- Malnutrition
- Schistosomal nephropathy
- Renal failure
- Pyelonephritis
- Heamturia
- Infertility
- Severe anemia
- End-organ disease
- Pregnancy comlications from vulvar or fallipian granuloma
- Carcinoma of the liver, bladder or gallbladder.
29
~Prevention~
- Avoiding contact with fresh water infested with Schistosome parasites-- Swimming, wading, or any other aquatic activities in these bodies of water exposes the skin to possible penetration by the cercariae
- Boil water before use
- Allowing the water to stand for 24 hours or more before using it may also help in preventing infection.
- Fine-mesh filters may also be used to filter the cercariae possibly contained in the water.
- Insect repellants may be applied topically to prevent cercariae from penetrating the skin, but this is not a very reliable measure.
30
- In 2001, the World Health Assembly resolution 54.19 endorsed chemotherapy as the main strategy for control of schistosomiasis through mass drug administration.
- Set a target of 75%–100% regular chemotherapy coverage for school-aged children (aged 5–14 years) at risk of morbidity by 2010.
- This target was not achieved.
- In 2010, over 108 million school-aged children required treatment, and at least 21 million were given treatment (19%) far below the target stated in the resolution.
31
Control Program
- 3 complementary targets to cut the transmission chain
- 1. intermediate hosts (snails)
- 2. contacts of people with freshwater
- 3. reduction of the number of excreted eggs
32
1. Targeting snails
- Mollusciciding
- chemical product : niclosamide
- 2 opposite ways for use:
- large applications: main irrigation canal or…by plane! but the ecological impact, cost, no cooperation of the community
- focused application » localization of all water contact-areas » cercarial research » focused mollusciciding. frequency of application: every 3 or 6 months?
33
2. Hygiene and sanitation
- 2 ways:
- Health education -modification of behaviour linked to educational level and socioeconomic necessities. This however, has poor impact \ takes a (very) long time.
- For behavioral change to be feasible, alternatives must be given and complemented with provision of sanitary water and toilet facilities
- provision of sanitary facilities • washing-places • latrines • water supplies.
34
Mass Drug Administration
- Praziquantel • single oral dose of 40 to 60 mg\kg
- well tolerated
- Who? – targeted treatment? : children, fishermen… – whole population?
- When? – every 3 ? 6 ? months
Epidemiological assessment of the community should be done to determine the prevalence and presence of ongoing transmission of infection.
35
Where should preventive treatment be taken at least once a year?
High-risk communities (prevalence of infection is at least 50% or urinary schistosomiasis has a prevalence of 30% or higher based on history of hematuria) all school-aged children as well as adults considered to be at risk are eligible for preventive treatment and should be treated at least once a year.
36
Where should preventive treatment be taken every 2 years?
Communities where prevalence is at least 10% but not less than 50% or where urinary schistosomiasis detected by history of hematuria has a prevalence of less than 30%- school-aged children as well as those in the special risk groups should be given preventive treatment every 2 years.
37
In which areas are only school-aged children treated?
Only school-aged children are treated in areas classified as low-risk communities (prevalence <10% by parasitological methods).
- Treatment should be given only twice during the primary school years.
- The drug should be made available in community clinics or dispensaries for treatment of suspected cases
38
Integrated Control Strategy
Includes:
- WASH
- Annual Mass drug administration
- Health Education
- Targeted Mollusciciding
39
WASH interventions are diverse, potentially including improvements in water access
WASH interventions are diverse, potentially including improvements in water access
- (e.g., water quality, water quantity, and distance to water)
- sanitation access (e.g., access to improved latrines, latrine maintenance, and faecal sludge management)
- and hygiene practices (e.g., handwashing before eating and/or after defecation, water treatment, soap use, wearing shoes, and water storage practices).
- Interventions often include multiple components while also providing hygiene education.
