Viral Diseases – Part IIViscerotropic & Neurotropic

Viruses

Nestor T. Hilvano, M.D., M.P.H.

Learning Objectives You should be able to: 1. Describe the diseases associated with Epstein-Barr

virus. 2. Describe the epidemiology of cytomegalovirus infection. 3. Describe the epidemiology, treatment and prevention of

hepatitis B 4. Compare and contrast hepatitis A, B, and C. 5. Describe the effects of mumps infection and its

prevention.6. Describe the effects of polioviruses on humans 7. Contrast the two types of dengue fever. 8. Differentiate between a disease and a syndrome using

AIDS as an example. 9. Describe the effects, treatment, and prevention of rabies. 10. Discuss the effects of roravirus and parvovirus in

digestive tract.

Viscerotropic Viruses • Infectious mononucleosis, Burkitts

lymphoma (Epstein-Barr virus)

• Cytomegalic inclusion disease (CMV)

• Hepatitis (Hepatitis A, B, C)

• Mumps (paramyxovirus)

• Enteritis (parvovirus, rotavirus)

Epstein- Barr Virus Infections • Transmission via saliva (kissing) • Infectious mononucleosis

- atypical, activated T cells (mononuclear cells)- infected B cells rupture → viremia - Symptoms = fever, 2-4 weeks; fatigue; sore throat; enlargement of lymph nodes, liver, and spleen; also affect heart, lungs, kidney, CNS- Mx = focus on relief of symptoms - Prev = impossible; virus widespread

• Burkitts lymphoma (first virus implicated with human CA) - infectious, malignant tumor of jaw (nasopharyngeal CA)

- responsive to chemotherapy and surgery

Cytomegalovirus disease• CMV become latent• Transmitted in secretions

- thru sexual contact, intrauterine exposure, vaginal birth, blood transfusion, breast feeding, respiratory

droplets, or organ transplant • 10% neonates – teratogenic (erthroblastosis fetalis),

premature, low birth weight, anemia, jaundice, splenomegaly, deafness, brain damage

• 90% - no manifestations at birth; s/sx develop later• Outcome – die (50%), some mentally retardate, or some

recover • Inclusion bodies - half the size of nucleus, surrounded by

clear halo (viral coat)

Hepatitis A

• Endemic in central and south america

• Hepatitis A virus (enterovirus 72)

• Acute hepatitis (fatigue, malaise, nausea, vomiting, jaundice, light stools, enlarged liver)

• Infection via fecal-oral route, contaminated food/water or milk

• Self-limiting; return to non- carrier state; mortality < 0.1%

• 45% Americans have antibodies

Hepatitis B• Carrier to symptomatic• Acute hepatitis B→

hepatocellular CA• Incubation up to 6 months• Infection via – percutaneous;

non-percutaneous (sex); vertical (mother to baby)

• Prev – Immunization (3 doses HBV over 6 months period)

Hepatitis C• Flavivirus (hepatitis C) • 90% of non-A, non- B in US (>4 mil.)• Most prevalent hepatitis in the world; silent epidemic• Spread via needles, organ transplants, and sexual

activity• Chronic hepatitis lasting for 20 years or more Progressive liver damage→ cirrhosis

→ liver failure (and cancer) → death • Other hepatitis

- hepatitis D = can propagate only with hepatitis B- hepatitis E = enteric hepatitis (gastroenteritis);

fecal- oral route

Mumps Virus • Single stranded RNA virus• Spread in respiratory secretions• Rubulavirus infect cells of URT

- Fever and pain on swallowing

- Parotitis – painful, enlarged ________. • Viremia develop - orchitis • Others aymptomatic • Recovery complete• Vaccine - MMR

Enteritis (Stomach Flu) • parvovirus and rotavirus

• Acute diarrhea, vomiting= GIT symptoms

• oral-fecal route

• Parvovirus (ssDNA)

- also cause red rash on cheeks and spread trunk and limbs (erythema infectiosum or fifth disease)

• Rotavirus (dsRNA)

- gastroenteritis in children ; self-limiting

Neurotropic Viruses • Directly infective

- poliomyletis - rabies

• Arthropod-borne (mosquito vector)- eastern equine meningoencephalitis - western “ “ - venezuelan “ “ - california “ “ - east nile “ “- west nile “ “ - dengue fever- yellow fever

• Hemolymphopoietotropic viruses- HIV

Poliomyelitis • Nearly eradicated worldwide• Serotypes:

a. asymptomatic, minor polio (5% cases)b. nonparalytic polio (<2%)c. paralytic polio – causing paralysis of limbs (LMN) and resp. muscles (iron lungs/death)

• Vaccines, 2 types - inactivated (killed) polio vaccine (IPV) = Jonas Salk, first tested in 1955- oral polio vaccine (OPV) = attenuated (weakened) poliovirus, dev. by Albert Sabin and first used in 1961

Rabies • Caused by rhabdoviridae• Transmitted via bite of infected animals• Affects P.N. into CNS• Manifestations – fever, headache, malaise, anorexia,

hydrophobia, seizures, hallucinations, and paralysis• Test on animals – identify negri bodies in brain (oval or

bullet-shaped inclusions in cytoplasm)• Rx

- clean the wound with soap and water- injection of human rabies immunoglobulin (HRIG)- rabies (deactivated) vaccine (HDCV) administer thru IM on day 0, 3,7,14, and 28 after exposure

• Prev – immunization of domestic animals

Dengue Fever• Flavivirus• Transmitted by Aedes mosquito• Tropical and subtropical region• Epidemic in Africa• 2 phases:1st phase – fever, weakness, and body pains

(breakbone), self-limiting, lasting in 6- 7 days

2nd phase – dengue hemorrhagic fever, serious disease

HIV • 1981 1st documented case of AIDS• Infection via body fluids• HIV 1 – prevalent in US;

HIV 2 – prevalent in Africa• Kills T- helper cells, macrophages, smooth muscle cells,

and antigen-presenting cells (CD4) • A CD4 lymphocyte count of 200 or less — a normal

count ranges from 800 to 1,200 • AIDS – dev.

- pneumocystis carinii pneumonia- Karposi’s sarcoma = red or purple patches on the skin and/or mucous membranes and spreads to other organs in the body, such as the lungs, liver, or intestinal tract; death

• Rx – AZT (azidothymidine, nuccleotide analog)

Prional Diseases• Prions - infectious protein particles; lack nucleic

acids; self- replicating proteins; 132˚C for 1 hr. destroys prions

• convert cellular protein into prions (single protein) by conformational change (alpha helices to beta pleated sheets)

• Cause spongiform encephalitis (motor disorder)

1. bovine spongiform encephalitis = mad-

cow disease in cattle

2. scrapie in sheep

3. Kuru or Creutzfeldt – Jacob disease

Mad Cow Disease in cattle• Bovine spongiform encephalitis• MOT: Infected/contaminated tissue via ingestion,

transplant, contact of mucous membrane, and skin abrasions

• Food contaminated with prions (1986)• 2006 there were 200 individuals worldwide (3 in

the US) • FDA banned mammal-derived food supplements• In Human- loss of mental and physical functions;

no cure

Scrapie • first identified in the 18th century • Degenerative disease affecting the central

nervous system of sheep and goats.  • passed mostly during the birthing process – via

placenta or fetal fluids• Loss of motor control - cannot get up and eat and

drink, and all body functions can be impaired• Loss of wool → loss of skin → death• No cure

Kuru/Creutzfeldt-Jakob Disease• 200 case per year; fatal neuro-

degenerative disorder • Usually within the same family • accumulates in the neural cells,

disrupting function and leading to vacuolisation and cell death

• Clinical manifestations -behavioural disturbances, progressive dementia, visual disturbances, cerebellar, pyramidal and extrapyramidal signs.

• No cure

Homework

1. Define – Burkitt’s lymphoma; hepatitis; parotitis; orchitis; poliomyelitis; hydrophobia; negri bodies; dengue hemorrhagic fever; karposi’s sarcoma

2. Compare and contrast hepatitis A, B, and C.

3. Describe the effects of polioviruses on humans.