Biology 261

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Brandon47
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120924
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Biology 261
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2011-12-05 10:12:15
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Chapter 34
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Chapter 34
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  1. What causes rabies and how is the diagnosis confirmed? What is Negri bodies? How is the spread of rabies controlled? What are the guidelines for rabies immunization?
    - Rabies is caused by a rhabdovirus, a negative-strand RNA virus that infects cells in the central nervous system of most warm-blooded animals, almost invariable leading to death if not treated.

    - Negri bodies: fluorescent antibodies in nerve cells.

    - All dogs and cats should be vaccinated against rabies beginning at 3 months of age, and booster inoculations should be given yearly or every 3 years.
  2. Describe the spread of hantavirus to humans. What are the
    two diseases associated with hantavirus infection? What are some effective measures for preventing infection by hantaviruses?
    • • “Four corner” disease, traced to the deer mouse as a natural reservoir. Other rodents also serve as
    • reservoir.

    • In 1993 outbreak 32 deaths in 53 affected adults.

    • A member of Bunyaviridae, negative strand RNA virus.

    • • Cause either hantavirus pulmonary syndrome (more
    • typical in Western Hemisphere) or hemorrhagic fever with renal syndrome (common
    • in Asia).

    • Humans are infected through exposure to dry urine and feces of rodents.

    • Death is within 5 days

    • • Typical detection is
    • with ELISA or by RT-PCR

    • • No treatment or vaccine.
    • A BSL-4 pathogen.
  3. Name rickettsial diseases commonly encountered
    in the US. What are the pathogens that cause these diseases? How would you diagnose, treat and control rickettsial infections?
    • Rickettsia are closely related to mitochondria and contain several virulence genes.

    • • Typhus fever - Rickettsia prowazekii. Transmitted through body or head louse bites. 3 million death
    • in WWI. Epidemic typhus mortality can reach 6-30%. Treated with tetracycline
    • and chloramphenicol. Vaccine is available.

    • • Rocky Mountain spotted fever - Ricketsia ricketsii. Transmitted through injection of tick fecal
    • matter during tick bites. Mortality 1-30%. Treated with tetracycline and
    • chloramphenicol.

    • Human monocytic ehrlichiosis - Ehrlichia chaffeensis and Neorickettsia sennetsu. Human granulocytic anaplasmosis (ehrlichiosis) - Ehrlichia ewingii and Anaplasma phagocytophilum. Both transmitted by ticks. Deer and rodents are additional reservoirs. Flu –like symptoms. Treatment with doxycycline.

    • • Q fever - Coxiella burnetii. Transmitted from animal to animal through insect bites. Humans become infected through contact with animals and animal products. Flu-like infection, treated with
    • tetracycline.

    • • Diagnosis of rickettsial diseases with fluorescent antibodies, the presence of specific antibodies in
    • blood (ELISA, latex bead agglutination) or PCR.

    •Control through control of lice, fleas and ticks.
  4. What are the primary symptoms of Lyme disease?
    Where is it spread and why? What are the complications associated with Lyme disease. How would you diagnose, treat and control Lyme disease?
    •Spirochete - Borrelia burgdarferi, which is spread by the deer tick.

    • Natural tick’s hosts are deer and white-footed field mouse.

    • Most frequently found in northeastern regions of the United States (see next picture).

    • Headache, backache, chills and fatigue. A large rush, erythrema migrans, is observed in 75% of cases. At this stage disease is easily treatable with tetracycline and penicillin.

    • • If progresses to chronic stage, arthritis (40-60%), neurological damage (15-20%) and cardiac damages
    • (8%) may occur. Ceftriaxone is used to treat chronic Lime disease.

    • • Detection of antibodies to Borrelia burgdorferi with ELISA, fluorescent antibody assay,
    • immunoblot, PCR. Can be cultured in 80% of cases.

    • No effective vaccine is available. A recently available vaccine has been pulled off the market.

    • Prevention: tick control and personal precautions.
  5. What causes malaria and how is it spread?
    Describe the life cycle of malaria. What are the two Plasmodium species, which are most commonly associated with malaria? How can malaria be diagnosed, prevented and treated?
    •350 million people are infected with malaria and 1 million dies every year.

    •Four species of protozoan belonging to the Sporozoa phylum. Plasmodium vivax is most common, Plasmodium falciparum is most deadly.

    • Transferred through bites of Anopheles mosquitoes, which prefer a hot climate and require water for breeding.

    • Diagnostics: microscopic observation of malaria cells in erythrocytes.

    • •Prophylaxis and treatment with chloroquine and primaquine and lariam (mefloquine). Melarone
    • (atovaquone and proguanil) is used for drug resistant strains. Doxycyline can
    • also be used for prophylaxis.

    •Control of malaria: (1) elimination of habitat, (2) elimination of mosquitoes.

    • Despite control, endemic malaria still exists in the US.
  6. What are genetic adaptations in of the human
    species to malaria infection?
    • Circle cell anemia

    • – Mutation in a beta chain of hemoglobin, valine is replaced with glutamic acid. Resulted hemoglobin is
    • called hemoglobin S.

    • – Under low oxygen condition hemoglobin S form long chains change the shape of erythrocytes. P.
    • falciparum cannot grow in such erythrocytes.

    • Glucose-6-phosphate dehydrogenase deficiency in some areas in Italy.

    • Thalassemias in Mediterranean populations lead to protection against P. falciparum.

    • •One specific MHC I and MHC II genes are expressed in some individuals in West Africa making them
    • resistant to malaria
  7. What causes plague and how is it spread? What are the form of plague and how is it treated and controlled?
    • Killed 25% to 33% of Europe population during the Middle Ages.

    • Natural disease of domestic and wild rodents (see next picture). Endemic in the southeastern states of the US.

    • Transferred by rat fleas.

    •Once infected Y. pestis travels to lymphatic nodes and form buboes. If not treated death occurs within 3-5 days.

    Pathogenesis is not clears. The V and W antigens inhibit phagocytosis. Murine toxin is an exotoxin produced by virulent strains. Endotoxin plays important

    • The epidemiology of plague due to Yersinia
    • pestis. Plague in most wild rodents is generally a mild, self-limiting infection. Plague in rats and humans is frequently fatal. Infected fleas desert the dead host and look for other hosts, such as humans, an accidental
    • host.



    • •Treatment: If treatment started promptly, mortality is 1-5%. Treated with streptomycin, tetracycline
    • and ciprofloxacin.

    • Control: surveillance of infected animals vector and human contacts.

    • Vaccine is available.
  8. What are the three modes, by which fungi can affect human
    health? What are mycoses? What are systemic mycoses common for the US? What makes people susceptible to mycoses?
    • Yeasts or molds, only 50 species cause diseases in human.

    • Hyperallergic response. Aspergillus spp.

    • Mycotoxin production, Aspergillus flavus

    • Mycosis

    – superficial mycosis

    – subcutaneous mycosis

    – systemic mycosis

    • primary and secondary infections
  9. Why are antifungal drugs difficult to develop?
    • A primary mycosis - direct infection with a fungal pathogen.


    • A secondary mycosis - in immunosuppressed individuals or following therapy with antibiotics.

    •In the US most common mycoses are:

    • Histoplasmosis caused by Hisptoplasma capsulatuim, Ohio and Mississippi river valleys,

    • • Coccidioidomycosis caused by Coccidioides immutis
    • (San Joaquin Valley fever).

    • Infected by inhalation, particularly serious infections in AIDS patients.

    • Treatment: amphotericin B.
  10. How does an infection with C. tetani takes place and what are effects of the tetanus toxin on
    a human body?
    • Caused by Clostridium tetani

    • Infection through contaminated wound, usually a deep puncture

    • C. tetani produces an exotoxin, the tetanus toxin

    • A vaccine is very efficient

    • Treatment: antibiotics, usually penicillin, antitoxin and support therapy. Once disease developed, morbidity and mortality are very high despite treatment.
  11. How is tetanus prevented and treated?
    •Caused by Clostridium tetani

    • Infection through contaminated wound, usually a deep puncture

    • C. tetani produces an exotoxin, the tetanus toxin

    • A vaccine is very efficient

    • Treatment: antibiotics, usually penicillin, antitoxin and support therapy. Once disease developed, morbidity and mortality are very high despite treatment.
  12. What are the primary symptoms of West Nile fever? Where is it spread and why? What are the vectors and reservoirs for West Nile fever?
    How would you diagnose and control West Nile
    fever?
    • West Nile fever or encephalitis.

    • Active disease in birds (more than 150 species) , can be transferred to human and horses by mosquito bites.

    •Human mortality is 4%, for horses it is up to 40%.

    • Adults over age 50 are most susceptible.

    • Diagnosis by ELISA and RT-PCR.

    • No specific treatment, prevention is a control of the vector.

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