STIs Flashcards
define commensal micro-organism
a micro-organism that derives food/other benefits from another organism w/o hurting or helping it
define pathogen
micro-organism that causes disease
define infection
invasion of all/part of the body by an organism
sub-clinical - asymptomatic
clinical - symptomatic
define sexually transmissable organism
virus/pathogen/insect/arthropod which can be spread by sexual contact
commensal/pathogen
define sexually transmitted infection - STI
infection by a sexually transmissable pathogen which is unlikely to be transmitted by non-sexual means
e.g. Neisseria gonorrhoeae, HPV type 6
define sexually transmitted disease - STD
disorder of structure/function caused by a sexually transmitted pathogen
e.g. pelvic inflammatory disease, genital warts
examples of bacterial sexually transmitted organisms in UK
Chlamydia trachomatis Klebsiella granulomatis Mycoplasma genitalium syphilis - treponema pallidum pallidum Neisseria gonorhoeae Chancroid - haemophilus ducreyi
examples of viral sexually transmitted organisms in uK
HSV
HIV
HPV
molluscum contagiosum virus
examples of parasitic sexually transmitted organisms in UK
pthirus pubis
sarcoptes scabei
trichomonas vaginalis
characteristics and their implications of STIs
contagious - sexual contact tracing
mostly asymptomatic - can’t eradicate just by treating symptom
unpredictable minority suffer significant complications - early detection and treatment needed
avoidable - 1y prevention is the goal
what is meant by sexually transmitted - different types of sexual contact
group sex anal sex vaginal sex oral sex - cunnilingus, fellatio touching someone else's genitals w/ your genitals mutual masturbation 'pants on'
increasing chance of catching infection the higher up the list
activity required for transmission examples
skin contact only: pubic lice scabies warts herpes
penetrative sex - chlamydia, gonorrhoea
group sex - hep C
pubic lice causative organism
pthirus pubis
scabies causative organism
sarcoptes scabeii
warts causative organism
HPV 6, 11
herpes causative organism
HSV 1, 2
why are STIs important
- morbidity and mortality - unpleasant symptoms - grouped into syndromes, psychological distress
- resources cost
- common
examples of symptoms caused by STIs
ulceration lumps genital discharge non-genital discharge rashes
examples of STIs that cause ulceration
2y syphilis
HSV
less common - chancroid, donovanosis
examples of STIs that cause lumps
genital warts
molluscum contagiosum
examples of STIs that cause genital discharge
penile, vaginal, rectal gonorrhoea chlamydia mycoplasma genitalium trichomoniasis - vaginal
examples of STIs that cause non-genital discharge
gonorrhoea - eyes
chlamydia - eyes
examples of STIs that cause rashes
scabies syphilis HIV crab lice molluscum contagiosum and other lump causing organisms
systemic symptoms of STIs
fever rash lymphadenopathy malaise arthralgia and arthritis
e.g. HIV, syphilis
late complications of STIs
infertility - chlamydia
cancer - 250 000 deaths globally from cervical cancer (HPV)
300 000 adverse pregnancy outcomes from syphilis p/a
where in the world are most deaths due to HIV
resource poor settings
where in the world are most deaths due to STIs (not including HIV)
e.g. syphilis, donovanosis, chancroid
all more likely in resource poor settings
south asia, many african countries
cost of resources for STIs
managing infertility due to chlamydia - IVF cost
cost of HIV medication/management of HIV related health conditions
taking time off work for treatment
how common are STIs
> 1mln new STIs acquired every day
>500mln have genital herpes
why do numbers of STI diagnoses change over time
- true difference in number of cases
- change in diagnoses but no actual difference in number of cases
changes in true number of cases - reproductive number
reproductive number (R0) = likelihood of transmission per encounter x rate of acquiring new partners x duration of infectivity
R0 >1 then epidemic is sustained
R0 <1 then epidemic reduces
what can we do to reduce transmissibility
vaccinate unexposed person before they are exposed to the organism
e.g. HPV
changes in number of partners from 1990-2010
increased numbers of partners/person
increased concurrent partners
more people having anal sex
more men reporting sex with men
more condom use
easier ways to find sexual partners e.g. apps
alcohol - hazardous drinkers
why might there be a change in number of diagnoses over time but no chance in cases
greater awareness of STIs = more testing
more people asking for tests, more clinicians considering STIs and testing for them
better tests
why are some STIs more common in some groups than others
e.g. syphilis
large proportion of cases occuring in men who have sex with men
cores and associative mixing theory; chains and random mixing
cores and assortative mixing theory
some people have sex with people like them - similar lifestyle, same ethnicity etc
high prevalence within a subpopulation (core) but limited spread through the community
examples of cores and assortative mixing
syphilis in people who exchange sex for drugs
lymphogranuloma venereum or HCV in HIV+ve MSM
chains and random mixing
some cores are very big e.g. heterosexual M and F
random mixing leads to lower prevelance but wider dissemination along chains
- most people have few sexual contacts over a given period of time and so chains are quite short
- if this was generalised, STI epidemics wouldn’t be sustained
management of someone w/ symptoms suggestive of STI
good hx
partner notification
HIV testing
health promotion
consultation w/ someone w/ symptoms suggestive of STI
standard hx components - PC, HPC, PMH/SHx, DHx
gynae hx
direct questions about symptoms
why is a sexual history necessary
determining possible cause of symptoms
detecting high risk behaviour and advising on risk reduction
tracing contacts
questions to ask in sexual hx
when did you last have sexual contact
casual contact vs regular partner - how long have you been together for
were they M/F
nature of sex act (often not relevant) - anxiety about specific incident, will it alter where you swab from
were condoms used
other contraception used
nationality of contact
assessment of longer term sexual risks (men)
have you ever had sexual contact with another man
have you ever injected drugs
sexual contact w/ - IDU, someone outside UK (clarify)
medical treatment outside UK (clarify)
paid for sex/been paid
what are the 2 ways of partner notification
patient tells contacts - client referral, preferred
NHS tells contact - provider referral
recommended further testing in consultation
most STIs are risk factors for HIV acquisition and transmission
if someone has one STI they could have another
health promotion in consultation
condoms prevent transmission of some STIs oral sex carries risks too address hazardous drug use vaccination HIV pre-exposure prophylaxis
pros and cons of condoms for prevention of tranmission
prevent transmission - HIV, chlamydia, gonorrhoea
not so good at preventing transmission of others - herpes, warts
risks from oral sex
not as great as vaginal/anal sex
fellatio more than cunnilingus
