NTD Flashcards
Schistosomiasis - definition/organisms
Water-borne parasitic infection with an intermediate host of freshwater snails. Two primary syndromes including intestinal (S.mansoni, S. japonicum) and urogenital (S.haematobium)
Schistosomiasis - geographical distribution
Mansoni - Sub-Saharan Africa and Brazil
Japonicum - China, Philippines, Indonesia
Haematobium - Sub Saharan Africa
Intestinal schistosomiasis clinical features
Diarrhoea, abdominal pain, blood in stool
Chronic inflammation can lead to intestinal strictures and obstruction, as well as liver fibrosis and portal hypertension
Urogenital schistosomiasis clinical features
Haematuria, dysuria. Chronic inflammation leading to contractures, hydronephrosis and squamous cell carcinoma of the bladder
Male/female genital schistosomiasis can cause STI symptoms like vaginal/bloody discharge and itch, pain during sex, infertility, increased risk of HIV
Acute (Katayama fever)
4-6 weeks later fever, urticaria, cough, abdominal pain
Schistosomiasis non-specific clinical features
Anaemia, growth faltering, reduced educational performance, cecariae dermatitis
Ectopic presentations of schistosomiasis
Transverse myelitis, pulmonary HTN and cerebral schistosomiasis
Schistosomiasis diagnostics - parasitological methods
- Stool microscopy - Kato-Katz (thick faecal smear)
- Urine microscopy - egg count, urine filtration and centrifugation
Intestinal schistosomiasis - diagnostics
- Stool microscopy
- Faecal occult blood/calprotectin
- Eosinophils + Hb
- Colonoscopy
- US liver
Urogenital schistosomiasis - diagnostics
- Urine microscopy
- Urine dip (haematuria)
- Urine antigen detection CAA (cannot speciate)
- Ultrasound and cystocopy
- Eosinophilia
Schistosomiasis - returning traveller approach to diagnostics
- Asymptomatic â wait for 3 months after last freshwater contact.
- Serology for schisto antibodies
- Blood count (Hb, eosinophilia)
- 3 x MSU for RBCs/ova
- 3 x stool for ova - Febrile presentation
- Exclude other life threatening illnesses
- Will need repeat PZQ if diagnosis confirmed
- Unclear whether steroids might be worth giving - Symptoms e.g. haematuria/change in ejaculate
Same as 1. and refer to Urology/Gastro/Gynae depending on symptom
Schistosomiasis - returning from an endemic area - approach to diagnostics
- Asymptomatic
- Blood count (eosinophilia)
- 3 x MSU RBCs/ova
- 3 x stool for ova
- Urine antigen detection CAA (most sensitive and can be used for all types, CCA for S mansoni) - Symptoms or signs (e.g. haematuria, splenomegaly)
Same as 1 and include onward referral to Urology/Gastro/Gynae
Schistosomiasis treatment
Praziquantel
Needs repeat as not effective against non-adult forms
Praziquantel in schistosomiasis - pros and cons
Pros:
- Safe
- Effective against all species
Cons:
- Only effective against adults
- Global shortage
- Requires second dose a month later
- Taste is horrible
Prevention measures in schistosomiasis
- MDA annually in endemic regions
- Improved sanitation (open defecation and urination)
- Snail control - mulluscicides, habitat modification
- Safe water provisions
Onchocerciasis - organism
Onchocerca volvulus parasite
Onchocerciasis - transmission
Transmitted by blackflies (Simulium damnosum and Simulium ochraceum). Females bite outdoors in the daytime
Onchocerciasis - life cycle
- Blackflybites host and delivers 3rd stage larvae into the skin
- Larvae mature into adult worms in the subcutaneous tissue (itching)
- Adult worms produce microfilariae which migrate through the skin and eyes. They die, leading to inflammation and pathology
- When a blackfly bites a human it ingests the microfilariae which move into the midgut then to flight muscles before moving on to the mouthparts
Onchocerciasis - clinical features
- Skin - itching and firm/painless subcutaneous nodules in the acute stage followed by skin atrophy and patchy depigmentation (leopard skin) chronically
- Eye symptoms including keratitis, anterior uveitis, secondary cataracts, optic atrophy and chorioretinitis.
- Neurological - epilepsy, nodding phenomenen
Ochocerciasis - diagnostics
- Skin snips with microscopy to see the microfilariae
- Ov16 ELISA test
Onchocerciasis - treatment
- Ivermectin - does not kill adult worms so often needs prolonged/recurrent treatment
- Doxycycline - kills the Wolbachia bacteria which is needed for worm fertility. Give a 4 week course for definitive treatment.
Prevention strategies in onchocerciasis (5)
- Community directed treatment with ivermectin (MDA)
- Vector control - insecticide and environmental management
- Health education
- Surveillance and mapping
- Cross-border collaboration
Challenges in eliminating onchocerciasis (7)
- Cross border re-invasion
- Treatment limitations (ivermectin does not kill adult worms)
- Co-infection with Loa Loa endemicity as ivermectin can be life-threatening
- Sustaining public interest and funding in the longterm
- Conflict zones
- Competing public health concerns
- Capacity building of expertise - public health, entomologists, laboratories
Baylisascaris procynosis - definition
A racoon round worm infection from old poo (not fresh).
Found in Europe, N.America, Japan
Baylisascaris - clinical features
Human infections often asymptomatic but can cause visceral larva migrans, neural larva migrans and ocular larva migrans
Baylisascaris - treatment
Zap the eye with laser
Albendazole
Steroids in neurological diseases
Diffuse unilateral subacute neuroretinitis - definition and causes (5)
DUSN is caused by a live, motile nematode infecting the retina
It primarily affects one eye and leads to inflammation, vision loss, and retinal damage if untreated
- Gnathatoma - Thailand - eating raw fish/frog (drill head)
- Angiostrongylus - America, Vietnam, Thailand, Hawaii
- Toxocara canis, ancylostoma caninum (dog poo)
- Strongyloides
- Baylisascaris
Ciguatera poisoning - symptoms
Diarrhoea and vomiting within hours of ingestion
Neurological symptoms 3-72 hours after ingestion (paraesthesia, metallic taste, hot/cold allodynia, reversible cerebellar dysfunction)
Cardiovascular: Bradycardia, heart block, hypotension
Ciguatera poisoning - definition
Non-bacterial fish poisoning which can occur worldwide - especially Asia and Caribbean
Ciguatera poisoning - differentials
GBS, MS, organophosphate poisoning, botulism, scombroid, shellfish and pufferfish poisoning
Scombroid - symptoms
ALLERGY - Rash, palpitations, tachycardia
Shellfish poisoning - symptoms
GI upset, rapid onset pararesthesia and paralysis
Pufferfish poisoning - symptoms
Weakness (Na channel blockage)
Botulism - symptoms
GI upset, CN dysfunction, descending paralysis
Sea urchin injury - definition and treatment
Painful, visible puncture wounds
Causes granulomatous inflammation
1. Hot water soak
2. Remove visible spines where possible
3. Cover with antibiotics (staph, strep, mycobacterium marinarum, aeromonas hydrophilia) and topical steroids
Phytophotodermatosis - definition
Contact dermatitis on the skin when certain compounds are exposed to sunlight. This reaction results in skin inflammation and can cause blistering, redness, and hyperpigmentation.