B&B Path and Micro Flashcards
transmitted by mosquitoes to birds and mammals, birds being the major reservoir
humans are incidental hosts
can be transmitted through breast milk, transplant organs, transplacentally
maculopapular rash in 50% of cases
replicates in skin dendritic cells then migrates to lymph nodes for further replication before entering bloodstream and crossing the BBB
fatal cases are associated with loss of CCR5 chemokine receptor
perivascular and leptomeningeal chronic inflammation, microglial nodules, neuronophagia in temporal lobes & brainstem
High risk: elderly & immunosuppressed
West Nile Virus
Dx: serology, viral culture, PCR
Large encapsulated ds DNA virus
acute infection followed by latent infection
-During latency only LATs (RNA transcripts of latency) are produced and viral proteins are absent
-large pink to purple intranuclear inclusions (Cowdry bodies) that contain intact and disrupted virions
-dewdrop on a rose petal that progresses to pustular lesions, ulcers and crusted lesions
#1 associated with fever blisters and can cause corneal blindness or fatal sporadic encephalitis
#2 can be transmitted to neonates via birth canal
disseminates to liver, lung & other organs including CNS where it can cause death or mental retardation even with tx (mortaility 50%)
Encephalitis: lesions are limited to one of the temporal lobes, destruction gives rise to erythrocytes in CSF, seizures, focal neurologic abnormalities (most frequent cause of sporadic encephalitis); mortality 70% if untreated
meningitis:caused by #2 and resolves on its own
Herpes simplex virus
(Dx: Tzanck smear: large pink to purple Cowdry bodies and multinucleate syncytia)
Tx: acyclovir, valacyclovir, famcyclovir
moa acyclovir: inhibition of DNA polymerase
Spherical unencapsulated RNA enterovirus that persists in parts of Africa.
- spread mostly summer and fall
- infection in childhood results in very mild disease
- 90% asymptomatic
- transmitted by fecal-oral route and infects tissues of the oropharynx, is secreted into saliva and then swallowed
- multiplies in intestinal mucosa and lymph nodes
- transient viremia & fever
- 1 in 100 infection with this virus invades CNS and replicates in motor neurons of spinal cord or brainstem
- infects the brain by first infecting skeletal muscle then traveling retrograde viral spread along axons of motor neurons
Poliovirus
Tx/prevention: vaccination has eliminated wild-type polio from western hemisphere
Beta group virus that causes asymptomatic or mono-like infections in healthy individuals but devastating infections in neonates & immunocompromised
- transmitted via placenta, at birth, through breast milk, saliva in preschool year or venereal route after age 15
- latently infects monocytes and their bone marrow precursors; reactivated by depressed cellular immunity
- Inclusion disease: IUGR, jaundice, hepatosplenomegaly, anemia, thrombocytopenia with bleeding, encephalitis; fatal cases show calcification in brain & microcephaly
Cytomegalovirus
(Dx: large inclusion body with clear halo within the nucleus (owl’s eye); infected cells are strikingly enlarged; serology)
severe encephalitis from bite of animal or exposure to bats
-intense edema & vascular congestion in brain
-virus enters CNS by ascending along peripheral nerves from wound site
-incubation 1-3 months, depending on distance from site of wound to the brain
-slight touch is painful causing violent motor responses progressing to convulsions
-aversion to swallowing water due to contracture of pharyngeal musculature
ss RNA virus
enveloped rhabdovirus
Rabies virus
(Dx: Negri bodies are eosinophilic inclusions found in pyramidal neurons of hippocampus & Purkinje cells of cerebellum)
Tx: HRIG given IM in deltoid (3 doses); wash wound with soap and water
causes primary CNS lymphoma
- encephalitis is common in chronic phase
- widely distributed microglial nodules with or without tissue necrosis and reactive gliosis
- foamy or pigmented perivascular macrophages in subcortical white matter, diencephalon & brainstem
- multinucleated giant cell
HIV
-viral encephalitis caused by JC polyomavirus
-probably spreads by respiratory infection
-crosses the BBB by replicating in the endothelial cells of the capillaries
-infects oligodendrocytes and causes demyelination
-enlarged astrocytes with abnormal nuclei, resembling glioblastoma
-occurs primarily in immunosuppressed or in pregnancy
-most people exposed to virus by age 14 with no clinical disease associated with primary infection
focal and progressive neuro symptoms with reactivation of virus
destruction of cerebral white matter that may involve entire lobe
-impaired speech, vision, coordination, mentation or a combination
Survival: 1-4 months after dx
Progressive multifocal leukoencephalopathy
edge of lesion greatly enlarged oligodendrocyte nuclei with glassy inclusions. Bizarre astrocytes within lesions
interstitial keratitis, Hutchinson teeth (small and look like pegs), 8th nerve deafness
congenital syphilis
chronic venereal disease caused by T. pallidum spread by sexual contact
syphilis
exudate from chancre is used for testing
positive result 4-6 weeks after infection
negative in tertiary syphilis but positive in secondary syphilis
false positives associated with acute infections, SLE, drug addiction, pregnancy, hypergammaglobulinemia, lepromatous leprosy
Veneral Disease Research Laboratory (VDRL)
virus acquired by inhalation & causing primary infection in the tonsils and mucosa of the respiratory tract. Can also be spread by contact with vesicles.
Progresses via bloodstream and lymphatic system to reticuloendothelial system. Secondary viremia spreads through body and skin, infecting T cells.
-unique feature is presence of rash on scalp
-Viral replication in the lung is a major source of contagion
-latent in dorsal root or cranial nerve ganglia
-reactivated in adults with impaired cellular immunity & rash appears along dermatome innervated (may cause infection in one who is not immune)
Immunocompromised & newborns at risk for life-threatening pneumonia, encephalitis, and progressive disseminated varicella
ds linear DNA
Varicella-zoster virus
Dx: Cowdry type A intranuclear inclusion body and syncytia
Screen for immunity: serology
Tx: Vaccine (VZIG) within 4 days of infection, pain killers & topical anesthetics; acyclovir, famcyclovir, valacyclovir; booster VZV for older adults
Type A more severe in adults & children
-lesions of soft palate (herpangina), fever, sore throat, painful swallowing, vomiting, anorexia
-sudden unexplained heart failure in older children and adults; high mortality
Type B can be harmful to infants
-myocarditis & pleurodynia (devil’s grip)
Hand-foot-mouth disease:vesicular lesions of hands, feet, mouth & tongue, mild febrile illness
(+) SS, linear RNA picornaviridae
Coxsackievirus
(+) ss, linear RNA virus
picornaviridae
causes paralytic disease, encephalitis/meningitis, carditis, neonatal disease, rash, respiratory tract infection, undifferentiated fever, GI, disease in immunodeficient patients
Echovirus
(+) ss RNA virus
Vector: Aedes, Culiseta mosquito
Host: birds
Distribution: N & S America, Caribbean
Disease: mild systemic (fever, headache), severe encephalitis
highest mortality rate
decreased consciousness for 3-10 days during which provide supportive care
possible complications: paralysis, seizures, mental disability, death
Eastern Equine
killed vaccine for those working with the virus
(+) ss RNA virus Vector: Culex, Culiseta mosquito Host: birds Dist: N&S America Disease: mild systemic, encephalitis
Western Equine
killed vaccine for those working with the virus
