Microbiology-Zoonotic Viral Diseases Flashcards
A mother brings in her 5 year old boy who has wart-like 5mm papular lesions on his face, back and buttocks. He is actively involved in gymnastics and swimming. His brother had similar lesions when he was 5 and they resolved after 6 months. What is causing his condition?
Poxvirus: Molluscum contagiosum, commonly spread via towels in swimming pools and gymnasiums.
You are doing a humanitarian mission in Africa and see a man with a fever and severe headache for the past 3-4 days. Today the popular lesion popped up on his finger as shown below. His coworker had a similar infection that resolved after a month. What is causing his condition?
Poxvirus: Tanapox/Yabapox. Note the vesicular Orf lesion caused by sheep, goat, cow pox or vaccinia virus. These are commonly transmitted to humans from infected animals via arthropods.
A young boy presents with the lesions shown below, fevers, sweats, malaise and sore throat. 15% of people who get this die and there is an immunization for it. What is causing his condition?
Orthopox: Monkeypox. Note that the infection can be transmitted by prairie dogs and the Gambian giant rat.
What would you expect to see on EM of a patient infected with a poxvirus?
Brick-shaped virions in the cytoplasm
A patient presents who was bitten by a bat with nausea, vomiting, fever and encephalitis. He later expires. What would you expect to see on EM of his peripheral nerves?
Rabies is an enveloped, -ssRNA, bullet-shaped rhabdovirus.
Common animals that carry rabies
Skunks, foxes, bats and coyotes. Cats are the most common domestic animals with rabies in the US. Dogs are the most common worldwide.
CNS findings in a patient infected with rabies?
Negri bodies (eosinophilic cytoplasmic inclusion bodies)
Rabies Tx
If they have never been vaccinated, give both HRIG and vaccinate. Only give booster vaccination if vaccinated previously.
Virus responsible for SARS
Coronavirus: enveloped +ssRNA virus
SARS reservoir
Bats, they harbor lots of different types of coronaviruses
A patient presents with pneumonia. She recently returned from a medical service mission in Asia. She is the 4th person from that group to present with atypical pneumonia. How should you proceed?
Her travel history, occupation and association with other atypical pneumonias increase suspicion for SARS-CoV and you should
MERS-CoV reservoir
Camels
What makes Hendra and Nipah viruses so virulent? What type of viruses are they?
They have broad tropism: ephrinB2/B3 receptors allow for infection of many cells. These are paramyxoviruses.
How do humans get infected by Hendra and Nipah viruses?
Fruitbats infect animals and animals infect people.
Clinical manifestations once you’ve been infected by Nipah or Hendra virus?
Widespread vasculitis, thrombosis, ischemia and necrosis. Most sever in the brain, lungs and spleen; resulting in severe respiratory distress and acute encephalitis w/brain necrosis.
1st vaccine against BSL-4 agent for public use
Equivac HeV (against Hendra-sG soluble G glycoprotein subunit). Largely used in horses.
Filoviruses
Ebola & Marburg
Arenaviruses? Common vector?
Lass and South American Hemorrhagic fevers. Common vector is rat excreta.
Bunyaviruses? Common vector?
Congo-Crimean Hemorrhagic Fever (CCHF), Rift valley fever and Hantaviruses-HFRS and HPS. Common vector is deer mouse excreta for hantavirus.
All arboviruses and rodent-borne viruses are what?
RNA and enveloped (except reovirus, it is not enveloped)
A patient presents with fever and malaise 10 days after returning from a trip in west Africa. A few days later he becomes nauseated, vomits, has abdominal pain, sore throat and chest pain. He also complains that he has lot his hearing. While in your office he begins hemorrhaging from all orifices and is taken to the ICU where he expires of shock. If Mastomys rodents were found in the place he stayed at in Africa, what is the likely cause of his condition?
Lassa fever. The rat is the natural reservoir and people get infected by contact with rat urine and feces. Human to human transmission is possible.
Arenavirus characteristics
Enveloped, grainy appearance from ribosomes and 2 strands of ambisense RNA
A patient presents with fever, malaise, anorexia, myalgias and headache. Symptoms go away for a few days, then he comes back with a fever, headache, stiff neck, confusion, paralysis, sensory disturbances and seizures. In his house he has pet hamsters and mus musculus (common house) mice. What is causing his condition?
Lymphocytic choriomeningitis virus (LCMV). The 1st and 2nd phases are seen in this patient.
Virus that is likely an under-recognized cause of pregnancy complications
LCMV: associated with abortion, congenital hydrocephalus, chorioretinitis and retardation
Hantavirus characteristics
Enveloped -ssRNA w/3 segments. Transmitted by direct inhalation of rodent excrement or direct skin contact.
A patient presents with fever, headache, back pain, chills, blurred vision and rash 2-3 days after cleaning out his garage. On day 5 he become hypotensive and day 9 he develops renal failure, hemorrhage and goes into shock. Deer mice are found in the garage. What is causing his symptoms?
Hantavirus: hemorrhagic fever with renal syndrome (HFRS). There is also a hantavirus pulmonary syndrome (HPS, Sin Nombre Virus) that predominately damages the lungs (below) over the kidney.
5 stages of hantavirus infection
1) Febrile 2) Hypotensive 3) Oliguric 4) Diuretic 5) Convalescent
Arbovirus with 3 segmented genome
Bunyaviruses
Arbovirus with no envelope and 12 segmented dsRNA genome
Reovirus
Arbovirus that is bullet shaped
Rhabdovirus
Diseases transmitted by the Aedes mosquito
Dengue, Yellow Fever, VEE (rodent reservoir), EEE (bird reservoir), Rift Valley Fever
Diseases transmitted by the Culex Mosquito
Japanese (bird and pig reservoir), West Nile and St. Louis Encephalitis, WEE
Diseases transmitted by the sandfly
Sicilian Sandfly Fever, Toscana Virus
A patient presents with fever, rash, aches and chills. Later he becomes confused and develops encephalitis. He lives next to a pond with lots of mosquitos. How would you narrow your diagnosis and what vaccines are available for these diseases?
Serology is usually used to diagnose arbovirus infections. PCR can be used. Vaccine is available for yellow fever, Japanese encephalitis and West Nile is in the pipeline.
What type of virus is West Nile Virus? What other important viruses are in this family?
+ssRNA flavivirus. Japanese encephalitis, yellow fever and dengue are also in this family.
2 types of yellow fever
Jungle: cycles between non-human primates and mosquitos, humans infected when going into jungle. Urban: transmitted by Aedes mosquito.
Global distribution of yellow fever
South America and West Africa
Who proved that the secret to stopping epidemics of yellow fever is to get rid of the mosquitos that carry it?
Walter Reed
A patient presents with chills, fever, headache, malaise, myalgias, jaundice and black vomit from GI hemorrhage. Serology reveals yellow fever. When should be people be vaccinated against this?
It is a live attenuated vaccine that has rare side effects of yellow fever-like symptoms. Consequently it should only be given when people are traveling to or living in areas endemic with yellow fever.
A patient presents with high fever, lymphadenopathy, myalgias, arthralgias, headache, maculopapular rash, hemorrhage and shock. He lives near standing water and is thought to have dengue. What is responsible for his hemorrhage and shock?
There are 4 dengue serotypes. People usually have more severe infections when they have been previously infected by a different serotype.
What type of viruses are the equine encephalitis viruses?
Togaviruses
A patient presents with a flu-like illness that progresses to encephalitis 3-10 days after infection. The infection clears but he is left with sequelae of paralysis and mental retardation. Serology shows a togavirus. What are likely causes of his condition?
WEE (more common), EEE (infrequent), VEE (CNS less common and less severe). Note that all of these infections are typically asymptomatic.
Most important cause of pediatric arbovirus encephalitis in the US
La Crosse Virus, a bunyavirus
A patient from the Pacific Northwest presents with fever, chills, headache, myalgia, arthralgia, photophobia and lethargy. He develops hemorrhagic disease. A wood tick is found on his back. What is likely causing his condition? How do you narrow your diagnosis?
Colorado Tick Fever Virus, a reovirus. This virus is in many animal reservoirs and infects erythroid precursor cells. Hemorrhagic disease results from infection of vascular endothelium. Diagnosis with immunofluorescence on blood smear.
