STIs Flashcards
What is a commensal organism?
A micro-organism that derives food or other benefits from another organism without hurting or helping it
What is a micro-organism that can cause disease called?
A Pathogen
What is an infection?
The invasion of all or part of the body by a micro-organism
No symptoms=Sub-clinical
Symptoms=Clinical
What is a sexually transmissible organism?
A virus, bacteria, protozoan, insect or arthropod which can be spread by sexual contact (commensal or pathogen)
What is the difference between an STI & STD?
STI=An infection by a pathogen which is sexually transmissible and which is unlikely to be transmitted by non-sexual means
(Neisseria gonorrhoeae, HPV type 6)
STD=A disorder of structure or function caused by a sexually transmitted pathogen (organism on you as an infective process that is now causing harm)
(Pelvic inflammatory disease, Genital warts)
What is Chancroid & what organism causes it?
Bacterial sexually transmitted infection characterized by painful sores on the genitalia.
Haemophilus ducreyi
What are some examples of bacteria, viruses or parasites that are sexually transmitted organisms?
Bacteria:
Chlamydia trachomatis
Klebsiella granulomatis
Mycoplasma genitalium
Viruses: HSV, HPV, HIV
Parasites:
Pthirus pubis
Sarcoptes scabei
Trichomonas vaginalis
What are some pathogens that can be passed on through sex but are not classed as STIs?
- Sars CoV2
- Ebola
- Rika
What are some key implications of these characteristics of STIs?
1) They are contagious
2) Asymptomatic most of the time
3) Unpredictable minority suffer significant complications
4) Totally avoidable
1) Sexual contact tracing
2) Can’t eradicate by just treating the symptomatic
3) Early detection & treatment needed
4) Primary prevention is the goal
What does ‘sexually transmitted’ mean?
Not completely clear as there are lots of different types of sexual contact- some forms increase the chance of catching an infection
What type of infection is more commonly transmitted in group sex?
Hepatitis C
What can be spread by skin contact only?
Pubic lice (Pthirus pubis)
Scabies (Sarcoptes scabeii)
Warts (human papilloma virus types 6 &11)
Herpes (Herpes Simplex Virus types 1 & 2)
Why are STIs important if so many asymptomatic?
STDs cause morbidity & can even kill
They have unpleasant symptoms-grouped into syndromes
Psychological distress
What are some symptoms of STIs?
- Ulceration (e.g.HSV)
- Lumps (e.g. Mulloscum contagiosum)
- Genital discharge
- Non-genital discharge
- Rashes (syphilis & HIV both cause a rash that looks like measles)
What are the systemic symptoms of STIs?
- Fever
- Rash
- Lymphadenopathy
- Malaise
- Arthralgia & arthritis
What can be late complications of STIs?
- Infertility-chlamydia
- Cancer - e.g. cervical cancer-HPV
- Adverse pregnancy outcomes-syphilis
In what ways are STIs a drain on resources?
Managing infertility due to chlamydia: cost of IVF.
Cost of HIV medication/ management of HIV related health conditions
Taking time off work to get your warts frozen.
Are STIs common?
YES
More than 1M new STIs acquired every day.
More than 500M people have genital herpes
Why is the No. of people infected showing not many real signs of declining?
Partly due to ability to keep people alive for almost a normal lifespan
What does diagnoses of STIs not necessarily equate to?
Number of infected people
Why do diagnoses of STIs change over time?
- A true difference in the no. of cases
- A change in diagnoses but no actual difference in no. of cases
What does R number apply to and what is it?
R=average number of infections produced
It applies to every communicable disease
If R<1 what does this mean?
Epidemic reduces
If R>1 what does this mean?
Epidemic is sustained
How is Reproductive number calculated?
R0=BcD
= likelihood of transmission per encounter
c = rate of acquiring new partners
D = duration of infectivity
Why do we vaccinate unexposed person?
Reduce the transmission of the organism before they are even exposed to it
Eradicate main diseases caused by HPV
How do we know that there is a greater awareness of STIs?
More testing
- More people asking for tests
- More clinicians considering STIs and testing for them
(Better tests too- e.g. nucleic acid amplification tests vs enzyme immunoassays for chlamydia)
Describe Modelling and mapping the spread of STIs - Sexual network analysis?
’ Cores’ & assortative mixing
Some people have sex with people like them (similar lifestyle – eg IDU, same ethnicity)-leads to high prevalence within a subpopulation (core) but limited spread through the wider community.
E.g. syphilis in people who exchange sex for drugs or lymphogranuloma venereum or HCV in HIV+ve MSM
Core transmission – can link out to a wider population
Cores linked in the network
What are ‘chains’ & random mixing in sexual network analysis?
- Some ‘cores’ are very big – eg heterosexual men and women.
- Random mixing leads to lower prevalence 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
What is crucial in the management of someone with symptoms suggestive of an STI?
A GOOD HX
HEALTH PROMOTION
- Partner notification
- HIV testing
What histories should also be included in the consultations?
Sexual and gynae histories
Also need to ask direct questions about symptoms- Get thoughts on their condition & what they think it might be
What is a sexual Hx necessary for?
- Determining possible cause of symptoms
- Detecting high risk behaviour & advising on risk reduction
- Tracing contacts
What questions should be asked in a sexual Hx?
- When did you last have sexual contact?
- Casual contact vs ‘regular’ partner?
(How long were you going out with them for?) - Were they male or female?
- Asking about nature of sex act sometimes useful (anxiety about a specific incident or
If it’s going to alter where you swab from eg MSM) - Did you use condoms?
- Other contraception used
- Nationality of contact
In men what questions are asked to assess for longer term sexual risks?
Have you ever had sexual contact with another man?
Have you ever injected drugs?
Sexual contact with
anyone who’s injected drugs?
someone from outside the UK? (clarify)
Medical treatment outside UK? (clarify)
Paid for sex or been paid?
What are the 2 ways of partner notification aka contact tracing?
- Client referral (Patient tells contacts)
- Provider referral (NHS tells contact)
Why is further testing offered/recommended?
Most STIs are risk factors for HIV acquisition and transmission.
If someone has one STI (eg chlamydia) they could have another (eg HIV)
Do condoms prevent transmission of all STIs?
No but some- e.g. HIV, chlamydia, gonorrhoea
Not so good at preventing transmission of others such as herpes & warts
Does oral sex carry risks too?
Yes, not as great risks as vaginal or anal sex
Fellatio more than cunnilingus
Apart from use of condoms & risk awareness what should also be involved in health promotion?
- Address hazardous drug use
- Vaccination
- HIV pre-exposure prophylaxis
How will eradication most likely be achieved?
Through vaccination
How can you go about identifying and informing sexual contacts of someone with an STI?
‘Partner notification’ or ‘contact tracing’
(Don’t usually trace sexual contacts of people with warts or herpes as we have no tests or treatment for asymptomatic contacts.)
What are the signs of gonorrhoea (caused by Neisseria gonorrhoeae) in males compared to females?
Men
- 10% of males have no symptoms though might have clinical signs if examined.
- Thick, profuse yellow discharge, dysuria. Rectal and pharyngeal infection often
asymptomatic.
Women
- >50% have no symptoms.
- vaginal discharge, dysuria or intermenstrual/post-coital bleeding
What are the possible complications of gonorrhoea?
Male: Epididymitis
Female: Pelvic inflammatory disease. Bartholin’s abscess. [Gonococcal ophthalmia neonatorum.]
Both: Acute monoarthritis usually elbow or shoulder. Disseminated Gonococcal Infection: skin lesions - pustular with halo. (both v rare).
How is gonorrhoea diagnosed and treated?
Nucleic Acid Amplification Test (NAAT) on urine or swab from an exposed site – vagina, rectum, throat. Could be self-obtained or clinician-obtained.
Blind treatment with ceftriaxone 1g im. Can also treat according to antibiotic sensitivities.
Follow-up: Test of cure at 2 weeks and test of reinfection at 3 month
What symptoms can chlamydia present with (majority are asymptomatic)?
Men=slight watery discharge, dysuria
Women=vaginal discharge, dysuria, intermenstrual bleeding/post coital bleeding
Both=Conjunctivitis
What are the complications of chlamydia?
Men Epididymitis.
Women: PID and hence ectopic pregnancy, pelvic pain and infertility.
Both: Reactive arthritis/ Reiter’s syndrome – urethritis/cervicitis + conjunctivitis + arthritis
How is chlamydia diagnosed and treated?
First void urine in men. Self-taken or clinician-taken swab from cervix, urethra, rectum as appropriate.
All specimens tested using a NAAT
Treatment:
Doxycycline 100mg bd 1 week
Azithromycin 1g po once if pregnant
Follow-up: Test for reinfection at 3-12 months. Earlier test of cure not needed unless symptoms persist.
What are the symptoms of herpes?
80% have no symptoms. The rest have recurring symptoms – monthly, annually.
Burning/itching then blistering then tender ulceration
Tender inguinal lymphadenopathy. Flu-like symptoms.
Dysuria, Neuralgic pain in back, pelvis and legs,
What are the complications of herpes?
Autonomic neuropathy (urinary retention), neonatal infection, secondary infection
..?.. is important co-factor for HIV transmission
HSV2
How is herpes diagnosed and treated?
Clinical impression.
Swab from lesion tested using PCR.
Treatment:
- Primary outbreak: Aciclovir: various regimens
Lidocaine ointment
= Infrequent recurrences: Lidocaine ointment. Aciclovir once daily until symptoms gone (1-3 days)
- Frequent recurrences: Aciclovir 400bd long-term as suppression.
How does trichomoniasis present if it is not symptomatic in women (in men it is usually asymptomatic)?
Profuse thin vaginal discharge - greenish, frothy and foul smelling. Vulvitis
Complications=miscarriage and preterm labour
How is trichomoniasis diagnosed and treated?
Diagnosis: PCR on a vaginal swab. NB not validated on urine yet so no test for men.
Point of Care - Microscopy of wet preparation of vaginal discharge.
Treatment: Metronidazole
What causes anogenital warts?
Human Papilloma Virus types 6 and 11 (and occasionally type 1). (NB different strains from those that cause cervical cancer)
What are the symptoms of anogenital warts?
Lumps with a surface texture of a small cauliflower. Occasionally itching or bleeding especially if
perianal or intraurethral
What is the diagnosis and treatment of anogenital warts?
Diagnosis: Appearance. Biopsy if unusual – to exclude intraepithelial neoplasia, but this is rarely needed.
Treatment: Podophyllotoxin (brands warticon and condyline), imiquimod (brand Aldara). Both home treatments.
Others – cryotherapy
Bulky warts – diathermy, scissor removal
What is syphilis caused by and what are the symptoms?
Treponema pallidum
Often entirely asymptomatic or mild symptoms which go unreported.
Primary Local ulcer (chancre)
Secondary Rash, mucosal ulceration, neuro symptoms, patchy alopecia, other symptoms.
Early latent no symptoms but <2years since caught.
Late latent no symptoms but >2 years since caught.
Tertiary Neurological, cardiovascular or gummatous – skin lesions, (all v rare).
What are the complications of syphilis?
Neurosyphilis – cranial nerve palsies are commonest, cardiac or aortal involvement.
Congenital syphilis (extremely rare in Scotland).
How is syphilis diagnosed and treated?
Diagnosis: Clinical signs
Serology for TP IgGEIA, TPPA and RPR
PCR on sample from an ulcer
Treatment:
Early (<2 yrs and no neurological involvement):
- Benzathine penicillin
- Or Doxycycline
Late (>2 years) and no neurological involvement
- Benzathine penicillin
- Doxycycline (different dosing)
