Chapter 10

Introduction

• One of the major problems society faces is the spread of sexually transmitted diseases, or STDs.

• Many of them are bacterial and some are viral.

• Of all the diseases we face STDs can disrupt our quality of life and even cut it short.

• We’ll consider several of these topics in the next two lectures.

Fig. 10-01

Bacterial Diseases

• Bacteria (pathogens) cause many diseases in humans.

• Chlamydia, Gonorrhea, and Syphilis are all caused by a bacteria.

• We also may call these diseases communicable since they are spread by host to host contact.

• Some are also found in soil, water, food, etc.

Fig. 10Ab

Fig. 10Aa

How do we get around them?

• Most bacterial infections are treatable by simple antibiotics. Good for us!

• Antibiotics kill bacteria according to where they interfere in the bacteria’s metabolism.

• Resistance to treatment is always an issue.

• Antibiotics vs. bacteria will be a continuing war for us all.

The Big Three

• Chlamydia• Gonorrhea• Syphilis

Chlamydia

• Pathogen: Chlamydia trachomatis

• This is the leading cause of STDs in the US!

• ~18% of women have it, and don’t know it!

• Nearly 50% infection rate on college campuses estimated!

Chlamydia Symptoms

• Maybe none.

• Mild burning (18-21 days post sex) during urination.

• Vaginal discharge

• PID common side effect.

• Can affect babies during birth.

Chlamydia Treatment

• Single dose of Azithromycin, tetracycline or erythromycin.

Fig. 10-02

Infant with Chlamydia infection. Occurrence post-birth.

Gonorrhea

• Another “popular” bact. infection!

• Caused by Neisseria gonorrhoeae.

• Although the occurrence of this disease has declined drastically in reacent years, a rise in infection rates has been noticed since the late 90’s in adloescents, young adults, and African Americans.

Gonorrhea…

• Strangely enough, regular use of oral contraceptives in women increases their likelihood of contracting this disease. (Makes the birth canal more susseptable to infections by pathogens.)

• A double whammy? People diagnosed with “G” often also are diagnosed with “C.”

• Additionally, the presence of either (or both) of these diseases increases the likelihood of HIV infection.

• Why?

Rates of Infection Gonorrhea (1981-1999)

Gonorrhea Symptoms

• In men, this is relatively easy to detect. Why?

• Pain during urination, milky discharge 3-5 days post coitally (or after contact with pathogen).

• Women show lesser symptoms or are asymptomatic! May experience sever pain in the adbomial region due to PID.

• Women using IUDs are very succeptable to PID from the big “G.”

More symptoms…

• Gonorrhea of the anus?? Yep! Also known as gonorrhea proctitis. Pain, inflammation, blood or pus in the feces.

• Eye contact can also result in infection.

• Spreading to internal parts of the body is also possible.

Treatment for Gonorrhea

• Ladies, if your partner is infected, then you might as well flip a coin if you’re worried about having sex with them and becoming infected (Women: 50-60%, Men: 20%).

• Resistance is becoming more and more of an issue since many men and women don’t realize they are carriers. (Sharing of antibiotics also an issue…more later.)

• New tests are being devleope, but most rely on blood samples.

Syphilis

• Agent: Treponema pallidum.

• This one has three stages! Chancre, body rash, and gummas.

• ChancreChancre (right) is the site where the bacterium actually enters the body cavity.

Syphilis

• Palms of the hand can also be used to identify carriers.

• Body rash in these locations is obvious, although the rash doesn’t itch.

Syphilis

• Tertiary syphilis (gummas) may not always evolve.

• This stage lasts until the patient dies. Cure??

• Symptoms include cardiovascular weakening, aneurysms. Nervous system disorders, blindness, confusion, insanity.

Diagnosis and Treatment

• Diagnosis is often made by a blood test, or microscopically.

• Blood: Reagin (antibody)

• Usually followed up by a microscopic evaluation, since blood test may result in a falso positive.

• Penicillin will cure all stages if given in time and of sufficient dosage!

Viral Pathogens

Herpes, HIV, Genital Warts, Hepatitis.

What a Virus Isn’t

• Not a bacterium

• Not an independently-living organism

• Cannot survive in absence of a living cell within which to replicate

• Antibiotics do no harm to a virus, unless indirectly

• Treatment of a flu virus with antibiotics is only the treatment of its symptoms

• You don’t kill the organism that causes the flu!

What are Viruses?

• Infectious agents composed mainly of nucleic acid with a protein coat (capsid)

• Can only be seen with an electron microscope• Range in size from 10 to 200 nanometers (nM)• Carry on normal cell-like function unless free, then

infectious• In infectious form, they neither grow nor respire

• Can enter living plant, animal or bacterial cell

What do Viruses Look Like?

• Most viruses have a capsid, core and genetic material (DNA/RNA)• Capsid: outer shell of the virus which encloses genetic material (link:

chemical structure of capsid helps determine immune response to virus)

• Capsid is made of many identical individual proteins, precisely assembled

• Protein core under capsid protecting genetic material• Sometimes an additional covering (lipid bilayer w/embedded proteins)

on outside known as an envelope• Resembles a baseball• Various forms: rods, filaments, spheres, cubes, crystals

What do Viruses Actually Do?

• All viruses only exist to make more viruses• All, with the exception of some bacterial viruses,

appear to be harmful• Their replication leads to the death of the cell which

the virus has entered• Virus enters the cell by first attaching a specific

structure on the cell’s surface• Depending on the virus, either the entire virus enters

the cell or only the genetic material is injected

The Virus Invasion

• Phase 1: spike and fibers attach themselves to the walls of the cell or bacteria

• Phase 2: the sheath contracts and drives the core through the cell wall (injection)

• Phase 3: the nucleic acid passes through the core, from the capsid head, into the host cell

• Phase 4: nucleic acid disappears, afterwards (10m) hundreds of virions appear causing the cell to rupture, releasing hundreds of small viral replicates

• This is how it can replicate so quickly!!

The Virus Invasion

What Things Can Become Infected by a Virus?

• All living things have some susceptibility to a particular virus

• Virus is specific for the organism

• Within a species, there may be a 100 or more different viruses which can affect that species alone

• Specific: for example, a virus that only affects one organism (humans and smallpox)

• Influenza can infect humans and two animals.

Different Types of Viruses

• Major classification: animal, plant, bacterial• Sub-classified by arrangement and type of nucleic acid• animal virus group: double-stranded DNA, single-

stranded DNA, double-stranded RNA, single-stranded RNA, retrovirus

• influenza: SS-RNA• for all viruses, regardless of the kind of arrangement of

genetic material, the virus is capable of replicating within a living cell and can produce progeny

Human Viruses

“Best way not get hit is not be there when punch arrive.”

-Mr. Miagi (The Karate Kid II)

• Good advice! Applies to viruses too. Prevention of transmission is the ultimate cure.

• Herpes, Genetal warts, and Hepatitis are problematic in this area as they are very difficult to control outbreaks.

Herpes 1 and 2

• Herpes simplex virus 1 and 2 (HSV 1 and HSV 2) are difficult to deal with.

• HSV 1: Cold sores primarily• HSV 2: Genital herpes

• Cross-over symptoms work both ways.

• 45 million people are estimated to be infected.

Symptoms

• Tingling, itching followed by blisters on the genitals.

• Ruptured blisters are slow to heal (3 weeks) and painful.

• Fever and swollen lymph nodes in the groin also likely. (Copius vaginal discharge in women.)

• Healed ulcers don’t mean cure! Only latent condition.

• Sun, stress, and menstrual cycles will trigger outbreaks.

• Newborns can also be affected when passing through the birth canal. (Cesarean section avoids this!!)

Trasmission

• Transmission from infected individuals occurs primarily during lesion outbreaks.

• Monogamous relationships go a long way toward low risk.

• No cure. Multiple treatments for symptoms.

Treatment (cont.)

• Acyclovir and vidarabine: disrupt the viral reproduction, but don’t stop it altogether.

• Ointment of acylovir works to relieve initial symptoms, while oral drug valaciclovir (Valtrex) is most often prescribed for treatment of recurrent symptoms.

Genital Warts

• Caused by human papillomavirus (HPV)

• ~5.5 million people infected each year.

• A large cooccurence of genital warts and cervical cancer in women.

• No cure once infected, although warts can be removed.

• Vaccines exist for some strains.

Hepatisis

• Disease that attacks the liver. • Hep A: Sewage (aquired natural immunity possible)• Hep B: DNA virus spread by needle sharing• Hep C: infected blood (death)• Hep E: developing countries (rare in US)

• Vaccines available for Hep B (children get it now)

Fig. 10-08

HIV (AIDS)

• Aquired Immune Deficiency Syndrome (AIDS) is caused by the human immunodefficiency virus (HIV).

• Blood infection (64 million worldwide)

• While you’ve looked at this slide, at least 2 new cases have occurred in heterosexuals!

HIV (AIDS)

• Most cases are reported in Africa, many due to unprotected sex with infected men.

• How does HIV work? It’s complicated. That’s why our bodies haven’t developed an immunity, yet.

How AIDS Works• Lymphocytes in our blood

fight infection.

• B-lymphocytes are pathogen specific in action.

• T-lymphocytes which kill cells directly (T-killer cells) or assist others work better (“T-helper cells”) are the primary line of cellular defense against pathogens

• HIV destroys T-helper cells: ultimate result=immune system compromised

AIDS Stages

• AIDS has three phases: Acute (Category A), Chronic Infection (Category B), and AIDS (Category C).

• Most people die of secondary diseases also known as opportunistic infections (ex. Pneumonia).

• HAART treatment used to fight disease involves expensive drugs which disrupt replication of virus or help to strengthen existing immune system.

• Newer drugs actually promote active immunity in humans (turn on T-killer cells).

Other issues…

• “Vaginitis” caused by bacteria (Gardnerella vaginalis), parasites (Trichomonas spp.) (L), or yeast (Candida albicans) (R).

Crabs can also be problematic. Caused by a louse, Phthirus pubis. Treated with Lindane.