Parasitology clinical

Question 1

Trichomonas Pregnancy

Answer 1

PROM

Question 2

Chagas Epidemiology

Answer 2

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)

Question 3

Chagas Vector

Answer 3

Triatomine bug - painless bite, bigger than mosquitos or midges

Question 4

Chagas Organism

Answer 4

Trypanosoma cruzi

Question 5

Chagas Sequelae

Answer 5

2/3 indeterminate - disease free, 1/3 determinate - disesase - End organ damage to heart and GI tract (or both

Question 6

Chagas Transmission

Answer 6

Vector faeces, vertical, transfusion, transplantation, oral ingestion (large dose - fatal)

Question 7

Chagas Treatment

Answer 7

No evidence clearing the parasite has any impact on sequelae, BUT growing interest to treat women of childbearing age to interrupt vertical transmission

Question 8

Chagas Atypical presentations

Answer 8

HIV mimic cerebral toxo with SOL/meningoencephalitis, transplant recipients - fever, rash, myocarditis (mimics acute Chagas)

Question 9

Chagas Exposure

Answer 9

Risk related to duration of exposure to Triatomine, probably need to be living at least 6 months in area, no cases described in traveller

Question 10

Chagas Life cycle

Answer 10

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

Question 11

Chagas Family

Answer 11

Diagnosis should prompt wider family testing, may have common maternal source

Question 12

Chagas Natural history

Answer 12

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

Question 13

Chagas Cardiac disease

Answer 13

Arrhythmia, Myocardial abnormalities esp DCM -> aneurysms -> thromboembolic events

Question 14

Chagas GI disease

Answer 14

Megaoesophagus or Megacolon - severe constipation

Question 15

Chagas Serology

Answer 15

2 tests to confirm, eg RDT screen, ELISA confirm. Titre unhelpful, Ab response to therapy variable

Question 16

Chagas PCR

Answer 16

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

Question 17

Chagas Xenodiagnosis

Answer 17

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

Question 18

Chagas Treatment

Answer 18

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

Question 19

Chagas Treatment who

Answer 19

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

Question 20

Chagas Treatment future

Answer 20

BENDITA study - shorter courses of benznidazole (2w instead of 60d) + MULTIBENZ study - probably can get away with shorter and lower dose courses

Question 21

Chagas HTD protocol

Answer 21

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

Question 22

Chagas Summary

Answer 22

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

Question 23

Chagas Vector control

Answer 23

Spraying campaigns, vector avoidance

Question 24

Chagas Vertical transmission

Answer 24

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

Question 25

Chagas UK Chagas Hub

Answer 25

Diagnosis gap in London, community engagement to promote diagnosis and engagement in care successful