Lecture 36 11/18/24 Flashcards
How can Lyme disease be detected in humans?
-IgM increase within 2-3 weeks of bite
-IgG increase within 4-6 weeks of bite
-IFA and EIA (high sensitivity, low specificity)
-Western Blot (done after positive or questionable IFA/EIA, higher specificity)
What are the characteristics of IFA and Western Blot?
-IFA can be positive due to vaccination
-Western Blot is only positive with true infections
What are the characteristics of the Idexx 4DX SNAP test?
-contains antibodies to recombinant C6 peptide antigen
-only detects true Lyme infection, not vaccine responses
-also screens for Anaplasma, E. canis, and heartworm
What are the characteristics of serology results for Lyme?
-antibody titers can stay high for years
-positive titers do not indicate current infection
-have to see consistent clinical signs concurrently to diagnose based on serology alone
-do not test dogs or people without clinical signs
What are the characteristics of Lyme treatment in people?
-rash often resolves without treatment
-risk of systemic disease outweighs side effects and cost of antibiotics
-recommended to treat people with bullseye rash to prevent systemic dissemination
What is the post-exposure treatment for Lyme in people?
single dose of doxycycline within 72 hours of tick bite
What are the characteristics of Lyme vaccination in dogs?
-goal is to lower infection rate and allow for milder disease
-used mostly in endemic areas
-best to vaccinate dogs prior to exposure
-yearly boosters
-high vx reaction rate and limited efficacy
What are the characteristics of southern tick-associated rash illness?
-undetermined infectious etiology
-possibly caused by Borrelia, but NOT Borrelia burgdorferi
-spread by Amblyomma americanum/lone star tick
-responds to antibiotics
What are the clinical signs of STARI?
-bullseye rash
-fatigue
-fever
-headache
-muscle aches
-joint aches
What are the characteristics of ehrlichiosis?
-most common species associated with human disease are E. chaffeensis and E. ewingii
-associated with Amblyomma americanum/lone star tick
-similar symptoms to other tick-borne diseases
What causes the red meat allergy associated with Amblyomma americanum/lone star tick?
alpha-gal sugar in tick saliva
What is the most common Rickettsial disease in the US?
Rocky Mountain spotted fever
What are the characteristics of Rickettsia rickettsii?
-gram-neg.
-intracellular bacteria
-reservoir is rodents
-vectored by Dermacentor variabilis and Dermacentor andersoni
-ticks bite, are ingested, or contaminate wound with feces or fluids
What are the characteristics of Rocky Mountain spotted fever pathogenesis?
-tick must attach for only 6-20 hours
-tick saliva has anticoagulant to increase blood flow
-bacteria invades endothelial cells and causes them to rupture
-causes diffuse vasculopathy, perivascular inflammation, and microvascular thrombosis
What is the clinical presentation of Rocky Mountain spotted fever in humans?
-incubation of 3-12 days
-starts with a fever
-petechial rash develops
-myalgia
-headache
-fatigue
What are the potential complications of Rocky Mountain spotted fever?
-severe vasculitis
-septic shock
-SARDS
-renal failure
-GI hemorrhage
-thrombotic stroke
-meningitis
What are the risk factors for increased severity of Rocky Mountain spotted fever?
-male
-alcohol abuse
-advanced age
-non-caucasian
What are the clinical signs of Rocky Mountain spotted fever in dogs?
-fever
-lethargy
-anorexia
-weight loss
-petechiae
-ocular changes
How is Rocky Mountain spotted fever diagnosed?
-IFA serology for IgM or IgG antibodies
-PCR on blood or tissue biopsy
-immunohistochemistry on tissue
-culture
What is the treatment for Rocky Mountain spotted fever?
-antibiotics, including doxy, enrofloxacin, or chloramphenicol
-potentially IV fluids
-immunosuppression if immune mediated hemolysis or thrombocytopenia occurs
What are the four subspecies of Francisella tularensis?
-A/tularensis: most virulent, found predominately in North America
-B/holoarctica: rarely fatal, found in Europe and Asia
-novicida: occurs in immunocompromised individuals in North America
-mediasiatica: found in central Asia, not much is known
What are the characteristics of Tularemia?
-gram neg. coccobacillus
-very stable
-survives in water, mud, and dead animals
-associated with rabbits and rodents
-very few organisms needed for infection
-rare infection
-category A bioterrorism agent
How is tularemia transmitted?
-contact with infected animal tissues
-bite of infected tick
-ingestion of contaminated food or water
-bite of infected deerfly
-inhalation
What are the 5 types of tularemia presentation?
-ulceroglandular
-oculoglandular
-oropharyngeal
-typhoidal
-pneumonic
Which tularemia presentations are most common in humans?
glandular and ulceroglandular
How is tularemia diagnosed in people?
-culture
-gram stain
-DFA
-PCR
-four-fold increase in antibody titer
What is the treatment for tularemia in people?
streptomycin or gentamycin
What are the characteristics of tularemia in cats?
-typically have more severe signs
-obtain disease by ingesting wild rabbits and rodents
How is tularemia diagnosed in animals?
-culture
-FA serology
-PCR
How is tularemia treated in animals?
-streptomycin
-gentamicin
-chloramphenicol
-enrofloxacin
-doxycycline
How is tularemia prevented?
-do not handle potentially infected animals
-use tick/insect repellants for people and animals
-keep cats indoors
-do not ingest potentially contaminated food or water
What are the characteristics of heartland virus?
-phlebovirus
-transmitted by lone star tick
-similar symptoms to other tick-borne diseases
-clinical signs in reservoir animals unknown
-no vaccine or specific treatment
-no routine diagnostic test
What are the characteristics of Powassan virus?
-flavivirus
-transmitted by Ixodes spp.
-rodents act as reservoir
