zoonotic bacterial dz Flashcards
Modes of zoonotic bacterial acquisition
cutaneous contact (bites), arthropod vector, inhalation, ingestion
ZOONOTIC INFECTIONS-Definition
•Infections which are transmitted between man and other vertebrate animals. Humans are not necessary for transmission of zoonotic infections in nature. Infections in other animal host are frequently asymptomatic or mildly symptomatic
Name the bacteria associated with the following diseases: plague, Tularemia, Lyme’s disease, cat scratch fever, Typhus
plague: Yersinia pestis. Tularemia: Francisella tularensis. Lymes disease: Borrelia burgdorferi. Cat scratch: Bartonella species. Typhus: Rickettsia species
What caused the black death
The plague- yersinia pestis transmitted by fleas
define enzootic plague
A stable rodent - flea infection cycle that is maintained in a relatively resistant host population without excessive host mortality; a long-term reservoir of infection
define epizootic plague
Occurs when plague bacilli are introduced into rodent or small mammal populations that are moderately or highly susceptible to the lethal effects of the infection
define zootic plague
Transmission from animals to humans. Cats (NOT dogs) can develop pneumonic disease which can allow the organism to spread directly to people (e.g. veterinarians) without an intermediate insect vector. Fleas are usually responsible for human transmission though.
define demic plague
Transmission from humans to humans (e.g. Pneumonic Plague which is spread by aerosols)
types of plague
BUBONIC - Fever, painful lymphadenopathy from bite of flea 2-5 days earlier - 60-90% mortality untreated. SEPTICEMIC - - fever, hypotension, Invasion of almost all organs; no significant evidence of prior disease - death occurs in 12-24 hours. Usully from ingestion. PNEUMONIC - primary or secondary lung infection which is highly infectious and 100% fatal untreated.
Yersinia Pestis structure
Bipolar “safety-pin” Staining Bacteria. facultative bipolar-staining Gram-negative bacillus with capsule belonging to the Enterobacteriaceae. Contains coagulase-fibrinolysin. Grows more slowly at 37oC than at 28oC. Plasmids provide virulence and encode complement-resistant determinants and YOPS (tyrosine phosphatases) that interfere with phagocytes.
Y. enterocolitica/Y. pseudotuberculosis
less virulent relatives of Y. pestis cause enterocolitis (which mimics an appendicitis), reactive arthritis, septicemia, and mesenteric adenitis,
Septicemic plague complications
Hallmarks are ecchymoses (rupture of blood vessels under skin) and petechia, complicated by DIC
Yersinia pestis virulence factors
Ability to penetrate and multiply in non-phagocytic eukaryotic cells, and to kill phagocytic cells. These actions are due to: 1. plasma encoded genes: VW surface antigens; Type III secreted proteins -tyrosine phosphatase, cytotoxic factors; Flea associated virulence factors - coagulase-fibrinolysin. 2. Chromosome encoded genes: iron acquisition systems, attachment and invasion factors, endotoxin
Plague diagnosis
Wayson/Giemsa/Gram strains of a bubo aspirate; bubo/blood/sputum culture with confirmation by fluorescent antibody; serology
Plague treatment
streptomycin; supportive care; alternative: tetracycline, chloramphenicol and fluoroquinolones. You have to use antibiotics that are effective against intracellular pathogens since many will not penetrate human cells.
Plague prevention
killed vaccine gives short-term protection to high-risk individuals. (e.g. All laboratory and field personnel who are working with Y. pestis
Francisella tularensis transmission/ life cycle
Spread occurs from wild-animal reservoirs to domestic animals, especially rabbits and cats, and transmission to humans results from animal or insect bites, the handling of infected animal tissues, or inhalation of aerosolized organisms during activities such as landscaping or lawn mowing.
Francisella tularensis infectious dose
This is one of the most infectious bacterial organisms known. < 50 organisms applied to the unbroken skin can cause an infection; 5 - 10 organisms by the respiratory route; 10^6 - 10^8 organisms by ingestion. However, F. tularensis infections are not a severe as those caused by Y. pestis.
Types of Tularemia
Glandular - lymph node only. from a tick bite or other arthropod; no apparent lesion. Ulceroglandular - breach of skin; direct contact with infected animals (rabbits, rodents, coyotes)- ulcers (80% of cases). tender regional lymph node and a local papule that evolves into a chancriform lesion. Oculoglandular- inoculation of infected material directly into the eye or conjunctiva (~1%). Typhoidal - ingestion of contaminated material (meat, H2O). systemic disease without localized findings. Pulmonary - inhalation of contaminated material or hematogenous spread- occupational disease (bioterrorism??)
Francisella tularensis structure/ growth
Aerobin, pleomorphic Gram-negative coccobacillus that requires cysteine for growth; survives intracellularly; phase variation allows organism to avoid host immune system.
Which animals is F. tularensis most often associated with?
Type A is most commonly associated with infections with rabbits and cats
Tularemia diagnosis and treatment
diagnosis: serology. Treatment: Streptomycin or Gentamicin. Alternatives are levofloxacin, chloramphenicol or doxycycline.
Compare/contrast Tularemia and plague
Both are potential Bioterrorist weapons, Both are spread by aerosol and insect vectors, Both present with similar symptoms - Plague is usually more severe and more likely to be fatal. Only Plague can be transmitted person to person (i.e. pneumonic plague). A person with Tularemia does NOT spread the infection to another person.
Lyme disease- mode of transmission
Bite of Ixodes tick infected with Borrelia burgdorferi. Animal reservoirs include white-footed mouse and deer. Ticks have a 2 yr life cycle
Borrelia burgdorferi structure
loosely-coiled spirochete; difficult to culture from humans.
Lyme disease diagnosis
clinical. Serology in late dz but cant differentiate btw active/ previous dz. Use two tier testing: ELISA or IFA, confirmed by western blot. PCR not standardized. Infection with Babesia, Ehrlichia or tick-borne encephalitis must be ruled out.
Lyme disease clinical features
Erythema migrans, recurrent arthritis. Also possible is Bells palsy, radiculoneuropathy, meningitis/ encephalitis and cardiac problems
Stages of Lyme disease
- 3-30 day incubation period. 2. Stage 1- Localized infection, 1-4 weeks. Causes erythema migrans due to organisms multiplying in skin. 3. Stage 2- Disseminated infection 1 week- 6 months, symptoms are commonly intermittent. Secondary annular skin lesions, meningitis, carditis, musculoskeletal pain, eye abnormalities. 4. Stage 3- latent infection 6 months to 30 years. Acrodermatitis chronica atrophicans. Intermittent or chronic arthritis, chronic encephalopathy, polyneuropathy or leukoencephalitis, chronic cardiomyopathy
Describe erythrema migrans
Bulls eye rash. It may be warm, but is not usually painful. . The binding of human plasminogen and its activators to the surface of the spirochete may facilitate spread through the skin and other tissue matrices.
describe arthritis in Lyme disease
Large joint (knee) arthritis occurs months after exposure. Spirochetal decorin-binding proteins A and B bind decorin, a glycosaminoglycan on collagen fibrils; this binding may explain why the organism is commonly aligned with collagen fibrils in the extracellular matrix in the heart, nervous system, or joints
Most common cardiac conditions associted with Lyme disease
conduction block
Sx and treatment for suspected Lyme dz (high probability)
Sx: erythema migrans. Treatment: Empirical antibiotic treatment without serologic testing
Sx and treatment for suspected Lyme dz (intermediate probability)
Sx: oligoarticular arthritis. Plan: Serologic testing and antibiotic treatment if test results are positive
Sx and treatment for suspected Lyme dz (low probability)
Sx: nonspecific findings like myalgias, arthralgias and fatigue. Plan: Neither serologic testing nor antibiotic treatment
Which Abx are used for Lyme disease
doxycycline for early disease (oral) if >9. Alternatives are amoxicillin cefuroxime, azithromycin. Amoxicillin if <9 yrs. ; ceftriaxone (IV) 2-4 wks for neurologic disease
Lyme vaccine
Arthritis side effects. NO longer in use
