Parasitology clinical Flashcards
Trichomonas Pregnancy
PROM
Chagas Epidemiology
WHO estimates 5-8mil people worldwide infected. Bolivia is peak, largely central and south America, including Mexico - Bolivia has the highest incidence and prevalence in the Americas, but there are parts of Bolivia where there is no transmission at all – there is no granularity of where the risk areas are – problem for countries, but also for migrant health services – difficult to ascertain lifetime risk and offer testing to everyone (probably the safest)
Chagas Vector
Triatomine bug - painless bite, bigger than mosquitos or midges
Chagas Organism
Trypanosoma cruzi
Chagas Sequelae
2/3 indeterminate - disease free, 1/3 determinate - disesase - End organ damage to heart and GI tract (or both
Chagas Transmission
Vector faeces, vertical, transfusion, transplantation, oral ingestion (large dose - fatal)
Chagas Treatment
No evidence clearing the parasite has any impact on sequelae, BUT growing interest to treat women of childbearing age to interrupt vertical transmission
Chagas Atypical presentations
HIV mimic cerebral toxo with SOL/meningoencephalitis, transplant recipients - fever, rash, myocarditis (mimics acute Chagas)
Chagas Exposure
Risk related to duration of exposure to Triatomine, probably need to be living at least 6 months in area, no cases described in traveller
Chagas Life cycle
Bug gets infected from blood meal of infected host, replication occurs in the stomach. Bug bites to take a blood meal, satisfied with blood meal defaecates – causes itch and human scratch inoculates it. Portal of entry mucus membrane of eye – often bite around the eye, defaecates – wipe faeces into eye – Romanya’s sign (infrequent clinical sign) – looks like periorbital cellulitis – manifestation of acute Chagas
Chagas Family
Diagnosis should prompt wider family testing, may have common maternal source
Chagas Natural history
Self-cure does not occur in most infected individuals, paradigm is lifelong infection. Infection does not necessarily lead to disease. Indeterminate ‘have not developed end-organ disease’ – just have a positive antibody test. most determinate disease is isolated cardiac disease, some digestive (megacolon), some unlucky get both
Chagas Cardiac disease
Arrhythmia, Myocardial abnormalities esp DCM -> aneurysms -> thromboembolic events
Chagas GI disease
Megaoesophagus or Megacolon - severe constipation
Chagas Serology
2 tests to confirm, eg RDT screen, ELISA confirm. Titre unhelpful, Ab response to therapy variable
Chagas PCR
Not widely available, only performed if seropositive, helps to guide giving treatment, but killing parasite may not have any impact on whether they develop disease in the future, and the same for those with disease
Chagas Xenodiagnosis
Xenodiagnosis no longer routinely used – put the bug on the patient to bite (painlessly) to take a blood meal – then keep triatomine alive for a few weeks, then examine stomach for whether the parasite present – need to use the right triatomine for the person’s geographical location
Chagas Treatment
Benznidazole or nifurtimox, 60d poorly tolerated 1/3 will not complete - effective for parasite clearance, effect upon clinical endpoints unproven except prevents vertical transmission. BENEFIT trial demonstrated no benefit in reducing progression of cardiac disease
Chagas Treatment who
Indeterminate (pre-disease) seropositive, and immunocompromised with determinate, plus girls and women of child-bearing age, in addition to infants and children - treatment is toxic, lengthy and of variable benefit, but patients often want it as don’t like the idea of parasite
Chagas Treatment future
BENDITA study - shorter courses of benznidazole (2w instead of 60d) + MULTIBENZ study - probably can get away with shorter and lower dose courses
Chagas HTD protocol
Confirm serology, PCR, assess end-organ (cardiac ECG, 5d holter TTE, GI only if sx), explain diagnosis and implications for patient, siblings, children (if female), discuss merits and uncertainties of antiparasitic treatment, treat the underlying end-organ disease, and offer antiparasitic treatment, annual review to follow progression to determinate disease
Chagas Summary
2/3 infections ‘silent’, serodiagnosis then PCR, benznidazole treatment is toxic, therapeutic benefit uncertain - affects parasitological cure but impacts upon future end-organ damage less clear, shorter, better tolerated regimens are shifting balance towards offering treatment to wider range of patients
Chagas Vector control
Spraying campaigns, vector avoidance
Chagas Vertical transmission
Vertical transmission occurs in 5% pregnancies in women with T cruzi infection, without testing the transmission is invisible, antiparasitic treatment of infants is highly effective so early detection and treatment is critical, antiparasitic treatment during pregnancy is contraindicated, but future pregnancies can be protected by treatment, pre-conception antiparasitic treatment prevents almost all vertical transmission
Chagas UK Chagas Hub
Diagnosis gap in London, community engagement to promote diagnosis and engagement in care successful
