Quiz 8 material: Chs 26, 28 Flashcards
What is the function of the lacrimal gland?
secretes tears to keep the eye moist
What is the function of lacrimal puncta?
two small openings that collect tears from the eye
What is the function of lacrimal ducts?
move tears to a reservoir for tears called the lacrimal sac or tear sac
Where do tears flow after passing through lacrimal ducts?
through nasolacrimal duct to inner nose
what chemicals do tears contain to protect against pathogens?
defensins, lactoferrin, lysozyme
What is the conjunctiva and does it normally contain bacteria?
mucous membrane surfaces of the eyeball and inner eyelid-contain some microbiota
What is the vitreous humor and does it normally contain bacteria?
the watery material inside the eyeball. protected from contact with the environment and is almost almost always sterile, with no normal microbiota
What is conjunctivitis?
inflammation of the conjunctiva (pink eye)
What is blepharitis?
inflammation of the eyelids
What is keratitis?
inflammation of the cornea
What is keratoconjunctivitis?
inflammation of cornea and conjunctivitis
What is dacryocystitis?
inflammation of the lacrimal sac
Describe the pathogenesis of Chlamydia trachomatis and what eye disease it causes.
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
What is the most important eye infection globally, and what pathogen causes it?
trachoma caused by four serotypes (A, B, Ba, and C) of Chlamydia trachomatis
How are chlamydial infections prevented, diagnosed and treated?
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
Which bacterial conjunctivitis infections are associated with purulent discharge?
Streptococcus pneumoniae,
Haemophilus influenzae and Staphylococcus aureus (also infects newborns as well as adults)
What causes ophthalmia neonatorum, and how is it treated?
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.
Are conjunctival infections transmitted by the blood or nervous system?
both
How can HSV cause eye infections? How can it be treated?
travels through trigeminal nerve to eye, infection leads to keratitis. Treat with acyclovir
Which eye infection can varicella-zoster virus cause?
conjunctivitis
What is the most common cause of viral conjunctivitis?
adenovirus (shipyard eye)
What pathogen causes toxoplasmosis and how is the infection normally acquired?
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.
How can pregnant women transmit toxoplasmosis to the fetus?
tachyzoite stage can cross the placenta
How can toxoplasmosis affect the fetus?
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.
Describe the morphology of tachyzoites
Tachyzoites are typically crescent-shaped with a prominent, central placed nucleus.
What infection causes ‘river blindness’ and by what vector?
Onchocerca volvulus infection causes ‘river bindless’ and is transmitted by Simulium flies
What is the life cycle of Onchocerca volvulus?
- Blackfly (genus Simulium) takes a blood meal (L3 larvae enter bite wound)
- subcutaneous tissues
- adults in subcutaneous nodule
- adults produce unsheathed microfilariae that typicaly are found in skin and lymphatics of connective tissues, but also occasionally in peripheral blood, urine, and sputum.
- Blackfly takes a blood meal (ingests microfilariae)
- Microfilariae penetrate blackfly’s midgut and migrate to thoracic muscles
- L1 karvae
- L3 larvae
- Migrate to head and blackfly’s proboscis
What changes are seen in the eye when infected with Onchocerca volvulus?
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.
Why is Onchocerca volvulus infection called ‘river blindness’?
Because Simulium flies (vector of the disease) develop in fast flowing rivers, and people living near these sites are most affected.
What causes dengue fever, and what are the vectors?
Dengue virus, a flavivirus with 4 serotypes causes Dengue fever.
Transmitted by mosquitoes (like Yellow Fever
Virus) –Aedes aegypti and Haemagogus
What is the pathophysiology of Dengue Fever?
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
How does immunity against one serotype of dengue virus affect future/further infection with another serotype?
• 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.
How can dengue fever be prevented, treated and diagnosed?
• 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
What pathogen causes Lyme disease, and through which vector?
caused by Borrelia burgdorferi in the US and by B. garinii and B. afzelii in Europe
transmitted by Ixodes ticks
What is the incubation period of Lyme disease, and what are the signs and symtoms?
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
What other tests are required to confirm diagnosis of Lyme disease if the patient has a distinctive rash called erythema migrans?
none
What additional disease can Lyme disease cause, and what is the treatment for this disease?
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
What pathogen causes malaria, and through what vector?
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
Describe the life cycle of malaria
- Sporozoites from Anopheles saliva enter human blood as it take a blood meal, and travel to liver.
- 2-weeks to mature in liver cells
- Merozoites are released and infect
Red Blood Cells - Merozoites
mature into ring form, trophozoite and schizont forms - Schizonts release
merozoites
What is the pathogenesis of fever in malaria?
fever follows rupture of erythrocytic schizonts and is mainly due to the induction of cytokines such as interleukin 1 (IL-1) and TNF
Why do different Plasmodium species have specific patterns of fever, and how do these patterns differ among the causative organisms?
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
What pathogen(s) cause(s) African sleeping sickness? what is the vector?
The protozoan Trypanosoma brucei gambiense and T.b. rhodesiense
vector: Tsetse fly
What are the signs of symptoms of African sleeping sickness?
fever, splenomegaly
• signs of myocardial involvement
• The CNS may become involved headache, psychological
changes, weight loss and finally coma (sleeping
sickness) and death.
How is T. brucei so adept at surviving freely in the blood?
antigenic variation: can switch between ~900 different genes for surface glycoprotein coat
What are two causes of acute hemorrhagic conjunctivitis?
enterovirus 70, coxsackievirus A24
Keratoconjunctivitis from which three viruses can result in severe damage?
adenovirus, HSV, VZV
