Quiz 8 material: Chs 26, 28

Question 1

What is the function of the lacrimal gland?

Answer 1

secretes tears to keep the eye moist

Question 2

What is the function of lacrimal puncta?

Answer 2

two small openings that collect tears from the eye

Question 3

What is the function of lacrimal ducts?

Answer 3

move tears to a reservoir for tears called the lacrimal sac or tear sac

Question 4

Where do tears flow after passing through lacrimal ducts?

Answer 4

through nasolacrimal duct to inner nose

Question 5

what chemicals do tears contain to protect against pathogens?

Answer 5

defensins, lactoferrin, lysozyme

Question 6

What is the conjunctiva and does it normally contain bacteria?

Answer 6

mucous membrane surfaces of the eyeball and inner eyelid-contain some microbiota

Question 7

What is the vitreous humor and does it normally contain bacteria?

Answer 7

the watery material inside the eyeball. protected from contact with the environment and is almost almost always sterile, with no normal microbiota

Question 8

What is conjunctivitis?

Answer 8

inflammation of the conjunctiva (pink eye)

Question 9

What is blepharitis?

Answer 9

inflammation of the eyelids

Question 10

What is keratitis?

Answer 10

inflammation of the cornea

Question 11

What is keratoconjunctivitis?

Answer 11

inflammation of cornea and conjunctivitis

Question 12

What is dacryocystitis?

Answer 12

inflammation of the lacrimal sac

Question 13

Describe the pathogenesis of Chlamydia trachomatis and what eye disease it causes.

Answer 13

infection of the upper eyelid; re-infection and chronic infection causes inflammation with mononuclear infiltration; scar tissue contracts, eyelashes are pulled back and inturned-abrade cornea (entropion, corneal scarring, blindness). 4 serotypes are responsible trachoma

Question 14

What is the most important eye infection globally, and what pathogen causes it?

Answer 14

trachoma caused by four serotypes (A, B, Ba, and C) of Chlamydia trachomatis

Question 15

How are chlamydial infections prevented, diagnosed and treated?

Answer 15

prevented by face washing, diagnosed with nucleic acid amplification tests such as PCR (although often diagnosed in endemic areas based on clinical symptoms and microscopic analysis of conjunctival fluid or scrapings. Treated with azithromycin and doxycycline

Question 16

Which bacterial conjunctivitis infections are associated with purulent discharge?

Answer 16

Streptococcus pneumoniae,

Haemophilus influenzae and Staphylococcus aureus (also infects newborns as well as adults)

Question 17

What causes ophthalmia neonatorum, and how is it treated?

Answer 17

Neisseria gonorrhea as baby passes through birth canal, seen on first or second day of life and requires urgent treatment with ceftriaxone due to widespread penicillin resistance.

Question 18

Are conjunctival infections transmitted by the blood or nervous system?

Answer 18

both

Question 19

How can HSV cause eye infections? How can it be treated?

Answer 19

travels through trigeminal nerve to eye, infection leads to keratitis. Treat with acyclovir

Question 20

Which eye infection can varicella-zoster virus cause?

Answer 20

conjunctivitis

Question 21

What is the most common cause of viral conjunctivitis?

Answer 21

adenovirus (shipyard eye)

Question 22

What pathogen causes toxoplasmosis and how is the infection normally acquired?

Answer 22

The protozoan Toxoplasma gondii causes toxoplasmosis.
The infection is widespread in adults and children and is normally acquired by swallowing oocysts released by infected cats (the definitive host) or by eating raw or undercooked meat containing tissues cysts.

Question 23

How can pregnant women transmit toxoplasmosis to the fetus?

Answer 23

tachyzoite stage can cross the placenta

Question 24

How can toxoplasmosis affect the fetus?

Answer 24

tissue cysts can form in the retina of the fetus and undergo continuous proliferation, producing progressive lesions particularly when levels of immunity are low. These lesions may also involve the choroid and lead ultimately to blindness. One or both eyes may be affected.

Question 25

Describe the morphology of tachyzoites

Answer 25

Tachyzoites are typically crescent-shaped with a prominent, central placed nucleus.

Question 26

What infection causes 'river blindness' and by what vector?

Answer 26

Onchocerca volvulus infection causes 'river bindless' and is transmitted by Simulium flies

Question 27

What is the life cycle of Onchocerca volvulus?

Answer 27

1. Blackfly (genus Simulium) takes a blood meal (L3 larvae enter bite wound) 2. subcutaneous tissues 3. adults in subcutaneous nodule 4. adults produce unsheathed microfilariae that typicaly are found in skin and lymphatics of connective tissues, but also occasionally in peripheral blood, urine, and sputum. 5. Blackfly takes a blood meal (ingests microfilariae) 6. Microfilariae penetrate blackfly's midgut and migrate to thoracic muscles 7. L1 karvae 8. L3 larvae 9. Migrate to head and blackfly's proboscis

Question 28

What changes are seen in the eye when infected with Onchocerca volvulus?

Answer 28

The inflammatory responses in the eye cause a number of pathological changes, which may affect both the anterior and posterior chambers. These include: • punctate and sclerosing keratitis: death of small groups of cells on corneal surface • iridocyclitis: inflammation of iris and ciliary body (share blood supply) • chorioretinitis: inflammation of the choroid (thin pigmented vascular coat of the eye) and retina of the eye. It is a form of posterior uveitis. • optic atrophy.

Question 29

Why is Onchocerca volvulus infection called 'river blindness'?

Answer 29

Because Simulium flies (vector of the disease) develop in fast flowing rivers, and people living near these sites are most affected.

Question 30

What causes dengue fever, and what are the vectors?

Answer 30

Dengue virus, a flavivirus with 4 serotypes causes Dengue fever. Transmitted by mosquitoes (like Yellow Fever Virus) –Aedes aegypti and Haemagogus

Question 31

What is the pathophysiology of Dengue Fever?

Answer 31

Virus replicates in dendritic cells, peripheral blood monocytes, liver parenchymal cells and macrophages in lymph nodes, liver and spleen. • After an incubation period of 4–8 days, there is malaise, fever, headache, joint pain, nausea, vomiting and sometimes a skin rash. • Recovery may be followed by prolonged fatigue and/or depression. • Dengue hemorrhagic fever/dengue shock syndrome---is a Severe form of disease

Question 32

How does immunity against one serotype of dengue virus affect future/further infection with another serotype?

Answer 32

• After initial infection, antibodies are formed that are specific for that serotype. • After an infection with a different serotype, antibodies bind to the virus and not only fail to neutralize it, but enhance its ability to infect monocytes. • Infection of increased numbers of monocytes results in an increased release of cytokines into the circulation • this leads to vascular damage, shock and hemorrhage, especially the gastrointestinal tract and skin.

Question 33

How can dengue fever be prevented, treated and diagnosed?

Answer 33

• Prevention: Live attenuated tetravalent vaccine licensed in December 2015 • WHO recommends that its introduction should be considered only in locations where there is a high burden of disease. • There is no current recommendation for vaccination of travelers. • Treatment: supportive care • Diagnosis: Antibody detection (IgM/IgG); Antigen detection; PCR; Virus isolation

Question 34

What pathogen causes Lyme disease, and through which vector?

Answer 34

caused by Borrelia burgdorferi in the US and by B. garinii and B. afzelii in Europe transmitted by Ixodes ticks

Question 35

What is the incubation period of Lyme disease, and what are the signs and symtoms?

Answer 35

``` The bacteria multiply locally and, after an incubation period of about 1 week • characteristic lesion at the site of the tick bite develops in 80- 90% infections (erythema migrans) • fever • headache • myalgia • Lymphadenopathy ```

Question 36

What other tests are required to confirm diagnosis of Lyme disease if the patient has a distinctive rash called erythema migrans?

Answer 36

none

Question 37

What additional disease can Lyme disease cause, and what is the treatment for this disease?

Answer 37

In 75% of untreated patients, from 1 week to >2 years after the onset of illness. The initial manifestations to appear are neurological (meningitis, encephalitis, peripheral neuropathy) and cardiological (heart block, myocarditis). • The subsequent manifestations are arthralgia and arthritis, which may persist for months or years. Immune complexes are found in affected joints. • These late manifestations are immunological in origin and are probably due to antigenic cross-reactivity between Borrelia and host tissues. • Treatment: antibiotics (doxycycline) in early stages – complete recovery—late stages of disease IV antibiotics

Question 38

What pathogen causes malaria, and through what vector?

Answer 38

``` 5 species of Plasmodium (protozoan) cause disease • Plasmodium falciparum (most virulent) • P. knowlesi (most virulent) • P. vivax • P. malariae • P. ovale ``` -transmitted by the bite of an infected female Anopheles mosquito

Question 39

Describe the life cycle of malaria

Answer 39

1. Sporozoites from Anopheles saliva enter human blood as it take a blood meal, and travel to liver. 2. 2-weeks to mature in liver cells 3. Merozoites are released and infect Red Blood Cells 4. Merozoites mature into ring form, trophozoite and schizont forms 5. Schizonts release merozoites

Question 40

What is the pathogenesis of fever in malaria?

Answer 40

fever follows rupture of erythrocytic schizonts and is mainly due to the induction of cytokines such as interleukin 1 (IL-1) and TNF

Question 41

Why do different Plasmodium species have specific patterns of fever, and how do these patterns differ among the causative organisms?

Answer 41

synchronous cycle in red cells P. malaria has one pattern that exhibits higher fever on day 3 than the pattern ofr P. vivax, P. ovale, and P, falciparum

Question 42

What pathogen(s) cause(s) African sleeping sickness? what is the vector?

Answer 42

The protozoan Trypanosoma brucei gambiense and T.b. rhodesiense vector: Tsetse fly

Question 43

What are the signs of symptoms of African sleeping sickness?

Answer 43

fever, splenomegaly • signs of myocardial involvement • The CNS may become involved headache, psychological changes, weight loss and finally coma (sleeping sickness) and death.

Question 44

How is T. brucei so adept at surviving freely in the blood?

Answer 44

antigenic variation: can switch between ~900 different genes for surface glycoprotein coat

Question 45

What are two causes of acute hemorrhagic conjunctivitis?

Answer 45

enterovirus 70, coxsackievirus A24

Question 46

Keratoconjunctivitis from which three viruses can result in severe damage?

Answer 46

adenovirus, HSV, VZV