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Page 3: One Animal-Transmitted Viral Diseases (2 of 2)

  • Zoonosis: Animal disease transmissible to humans

    • Wild animals are a reservoir for disease

    • Generally transmitted via direct contact, aerosols, or bites

  • Diseases in animals may be either enzootic or epizootic

    • Enzootic: present endemically in certain populations

    • Epizootic: incidences reaching epidemic proportions in certain populations

Page 4: 32.1 Rabies Virus and Rabies (1 of 4)

  • Rabies

    • Occurs primarily as an epizootic disease in animals but can be spread as a zoonotic disease to humans

    • Reservoirs in the United States are raccoons, skunks, coyotes, foxes, and bats

    • Nearly 60,000 people per year die from rabies worldwide, primarily in developing countries

    • Worldwide, nearly 14 million people receive prophylactic treatment for rabies after exposure annually

Page 7: 32.1 Rabies Virus and Rabies (2 of 4)

  • Symptoms and pathology of rabies

    • Rhabdovirus: A negative-strand RNA virus that causes rabies

    • Infects central nervous system of warm-blooded animals

    • Leads to death if not treated

    • Enters the body through a wound or bite

    • In humans, nine months may pass before onset of symptoms

    • Virus proliferates in the brain and leads to fever, excitation, dilation of the pupils, excessive salivation, anxiety, and fear of swallowing

Page 8: 32.1 Rabies Virus and Rabies (3 of 4)

  • Diagnosis, treatment, and prevention of rabies

    • Rabies is diagnosed using tissue samples

    • Victim can be passively immunized with rabies immune globulin

    • A rabies virus vaccine also provides immunization

  • Rabies spread is prevented largely through immunization of domestic animals

  • Rabies treatment strategy has been extremely successful in the United States

    • Fewer than five cases a year are reported in humans, nearly always the result of bites from wild animals, most frequently from bats

Page 11: 32.2 Hantavirus and Hantavirus Syndromes (1 of 3)

  • Hantaviruses

    • Cause several severe diseases: hantavirus pulmonary syndrome (HPS) and hemorrhagic fever with renal syndrome (HFRS)

    • Both syndromes caused by hantavirus-infected rodents

    • Significant outbreaks have occurred in the United States

      • Yosemite camp sites in 2012

      • Arizona, Colorado, New Mexico, and Utah in 1993 caused 32 deaths among 52 infected people (60% mortality)

Page 12: 32.2 Hantavirus and Hantavirus Syndromes (2 of 3)

  • Symptoms and pathology of hantavirus syndromes

    • Hantavirus are enveloped viruses having segmented single-stranded minus-sense RNA genomes

    • Characterized by a sudden onset of fever, myalgia, thrombocytopenia, leukocytosis, and pulmonary capillary leakage

    • At nearly 40 percent, the mortality rate for HPS strains is significantly higher than for HFRS strains (1–15%)

Page 13: 32.2 Hantavirus and Hantavirus Syndromes (3 of 3)

  • Epidemiology, diagnosis, and prevention of hantavirus syndromes

    • Infections are handled with BSL-4 safety precautions

    • Infect rodents including mice, rats, voles, and lemmings

    • Up to 200,000 cases are recognized annually; this number can be reduced by limiting mouse habitats and contact with mice and their urine

    • Transmitted by inhalation of virus-contaminated rodent excreta

    • No virus-specific treatment or vaccine for hantaviruses

Page 19:

  • Spotted Fever Rickettsiosis (Rocky Mountain Spotted Fever) in the United States, 2017

Page 20:

  • Rickettsia rickettsii and Spotted Fever Rickettsiosis

Page 21:

  • Rickettsial Diseases (4 of 5)

    • Example: Ehrlichia chaffeensis

      • Emerging diseases are human granulocytic anaplasmosis (HGA) and human monocytic ehrlichiosis (HME), which are spread by tick bites

      • Flulike symptoms include fever, headache, malaise, and leukopenia or thrombocytopenia

      • Prompt recognition of these diseases is essential but remains difficult

      • Treatment with antibiotics is usually successful

      • Avoiding hosts and using insect repellents are the best measures for reducing chances of exposure

Page 22:

  • Rickettsial Diseases (5 of 5)

    • Q fever

      • Q stands for "query;" pneumonia-like symptoms are caused by Coxiella burnetii, which is an intracellular pathogen

      • Transmitted through contact with animals or their products (contaminated wool or meat)

      • Treated with tetracycline

      • Q fever is considered a potential bioweapon

Page 23:

  • Lyme Disease and Borrelia (1 of 4)

    • Lyme disease

      • Affects humans and other animals

      • Cases were first recognized in Old Lyme, Connecticut

      • Most prevalent arthropod-borne disease in the United States

      • Caused by the spirochete Borrelia burgdorferi

Page 24:

  • The Lyme Disease Spirochete, Borrelia burgdorferi

Page 25:

  • Lyme Disease and Borrelia (2 of 4)

    • Pathology, diagnosis, and treatment of Lyme disease

      • Spread primarily by the deer tick

      • Transmitted to humans while tick is obtaining blood meal

      • Symptoms of Lyme disease include headache, backache, chills, and fatigue

      • In 75 percent of cases, a large rash occurs at the site of the tick bite

Page 26:

  • Deer Ticks, the Major Vector of Lyme Disease

Page 27:

  • Lyme Disease Infection

Page 28:

  • Lyme Disease and Borrelia (3 of 4)

    • Pathology, diagnosis, and treatment of Lyme disease

      • During the initial stages, Lyme disease can be treated with antibiotics

      • Chronic stage develops in weeks to months

        • Some patients develop arthritis

        • Others develop neurological damage or heart damage

        • No toxins or virulence factors have been identified but the pathogen triggers a strong immune response

Page 29:

  • Lyme Disease and Borrelia (4 of 4)

    • Epidemiology and prevention of Lyme disease

      • Deer and white-footed field mouse are the prime mammalian reservoirs

      • Also identified in Europe and Asia

      • In the United States, most cases reported in the Northeast and upper Midwest

      • Number of Lyme disease cases rising yearly

Page 30:

  • Lyme Disease in the United States, 2017

Page 31:

  • Yellow Fever, Dengue Fever, Chikungunya, and Zika (1 of 3)

    • Yellow fever

      • Caused by yellow fever virus

      • Transmitted by mosquito bites

      • Endemic disease of tropical and subtropical climates

      • Found in Latin America and Africa

      • No antiviral drugs are effective

      • Preventable by vaccination

Page 32:

  • Yellow Fever and Dengue Fever

Page 33:

  • Yellow Fever, Dengue Fever, Chikungunya, and Zika (2 of 3)

    • Dengue fever

      • Caused by dengue virus

      • Transmitted by mosquito bites

      • Endemic disease of tropical and subtropical climates

      • Found in Mexico, Latin America, India, Indonesia, and Africa

      • Most infected individuals improve on their own

      • No antiviral drugs are effective, no vaccine for dengue

Page 34:

  • Yellow Fever, Dengue Fever, Chikungunya, and Zika (3 of 3)

    • Zika and Chikungunya disease

      • In 2015, Zika appeared in Brazil and has spread throughout South America

      • By 2016, outbreaks of Zika virus disease were reported in the United States

      • Zika can be transmitted from mother to fetus, and seems to cause severe neurological problems in the developing embryo (microcephaly or pathological small head)

      • Both Zika and Chikungunya are considered relatively mild diseases carried by mosquitos

      • Symptoms include headache, fever, and general malaise

Page 35:

  • West Nile Virus (1 of 2)

    • West Nile fever transmission and pathology

      • Caused by West Nile virus (WNV)

      • Transmitted by mosquito bites

      • Like the yellow fever, dengue, and Zika viruses, WNV is a flavivirus

      • Transmission of WNV is seasonal

      • At least 130 species of birds are WNV reservoirs

Page 36:

  • West Nile Virus

Page 37:

  • West Nile Virus (2 of 2)

    • Control and epidemiology of WNV

      • Humans and other animals are dead-end hosts

      • West Nile is now endemic in both birds and mosquitos across the United States

      • No antiviral drugs are effective in vivo against WNV

      • Veterinary WNV vaccine is widely used in horses where the mortality risk demands it, but no human WNV vaccine is currently available

Page 38:

  • Average Annual Incidence of West Nile Disease in the United States, 1999–2017

Page 39:

  • Plague (1 of 3)

    • Plague has caused more human deaths than any other bacterial disease in recorded history

    • Caused by Yersinia pestis, a gram-negative, facultatively aerobic, rod-shaped bacterium

    • Fleas are intermediate hosts and vectors that spread plague between mammalian hosts

Page 42: Plague (2 of 3)

  • Sylvatic plague is enzootic among rodents

  • Most common form of plague is bubonic plague

    • Buboes develop in the infected individual

    • Local hemorrhages produce dark splotches on the skin

    • Tissue necrosis occurs, giving plague its historical name, the "Black Death"

  • Pneumonic plague occurs when Y. pestis reaches the lungs

  • Septicemic plague is the rapid spread of Y. pestis throughout the body

Page 44: Plague (3 of 3)

  • Plague is a disease of domestic and wild rodents

  • Humans are accidental hosts

  • Y. pestis produces virulence factors that contribute to the disease process

  • Plague can be treated if rapidly diagnosed

    • Treatment with gentamycin or streptomycin

    • Prompt treatment reduces mortality to less than 5 percent of those infected

Page 47: Anthrax (1 of 2)

  • Robert Koch first isolated the causative agent of anthrax, Bacillus anthracis

  • Koch used anthrax to develop his principles for linking cause and effect in infectious disease (Koch's postulates)

Page 49: Anthrax (2 of 2)

  • Bacillus anthracis is the cause of anthrax

  • Endospores enhance the ability of B. anthracis to disseminate

  • Natural reservoir is soils

  • Three forms of human anthrax: cutaneous, gastrointestinal, and pulmonary

  • Anthrax is treatable with antibiotics if done early

  • Vaccine is available for high-risk individuals

Page 51: Tetanus and Gas Gangrene (1 of 2)

  • Tetanus is a serious, often life-threatening disease caused by an exotoxin produced by Clostridium tetani

  • Natural reservoir is soils

  • C. tetani gains access to the body through a soil-contaminated wound, typically a deep puncture

  • Result of C. tetani infection on people is lockjaw

  • Tetanus is preventable with the existing vaccine

Page 54: Tetanus and Gas Gangrene (2 of 2)

  • Gas gangrene is tissue destruction due to proteolysis and gas-producing clostridia

  • Clostridia enter deep tissue through trauma

  • Mainly caused by Clostridium perfringens found in soil and intestinal tract of mammals

  • Treatment with antibiotics and hyperbaric oxygen

  • Amputation of dead