A Landscape use changes 1800s early 1900s most of the land used for pasture hay production crops such as cotton etc As automobiles replaced horses much less land needed for pasture hay fields land reverts to forest good deer habitat due to lots of forest margin plants to browse B Elimination of predators wolves screw worm flies More food A less predation B Deer pop ns 12 x pre European colonization levels More deer more Ixodes ticks remember deer are not reservoirs for Borria burgdorferi though C Human pop n distribution suburbs farther from city more rural more contact with vectors More reservoirs more deer more rural lifestyle more disease Unit 3 PPT 3 Rocky Mountain Spotted Fever Pathogen Rickettsia rickettsii Vectors Dermacentor andersoni West D variabilis East Vectors also serve as reservoirs efficient transovarial transmission Amplification through a variety of vertebrates especially chipmunks microtine rodents Widely distributed through Central America South America Formerly in Rocky Mountain states but now more prevalent in Appalachian states esp North Carolina Tennessee GA about 5th or 6th on the list local hot spots eg Long Island Both vertical transmission mother to egg larva and horizontal transmission to amplifying hosts chipmunks other rodents maintains the pathogen in Nature Dermacentor variabilis Rocky Mountain Spotted Fever Symptoms occur 2 14 days post bite Initially non specific signs such as fever myalgia headache nausea Often gastrointestinal involvement which may become severe Typically 88 92 of cases a petecial rash develops between 3rd and 5th day Petecial rash spotted rash see photos Some cases have delayed rash or rash never develops Serious illness fatal in 4 8 of cases historically 20 80 if untreated Responds to tetracyclines doxycycline and chloramphenicol RMSF Rash gangrene Note each rash spot reflects site where blood vessel is hemorrhaging You can see this on the skin but it is also occurring internally including in the gut causing the gastrointestinal tract symptoms Eventually excessive damage to blood vessels impairs circulation and can cause organ failure and impaired circulation to extremities sometimes leading to life threatening RMSF incidence 1993 2010 another emerging tick borne disease Ehrlichiosis Anaplasmosis Obligate intracellular pathogens in membrane bound vacuoles Occur in grape like clusters termed morulae Two species infect humans Ehrlichia chaffeensis Human Monocytic Ehrlichiosis Anaplasma phagocytophila Human Granulocytic Ehrlichiosis Dogs Ehrlichia canis E ewingii Horses E equi A phagocytophila E ewingii will occasionally infect humans Note some species formerly included in Ehrlichia have been moved to other genera Eg Ehrlichia phagocytophila now included in Anaplasma Human Monocytic Ehrlichiosis HME Vector of HME Amblyomma americanum Reservoir white tailed deer Pathogen Ehrlichia chaffeensis Ehrlichia chaffeensis morulae immunofluorescence assay IFA Note no need to memorize any numbers on this slide The point is just that symptoms are general and there is no unique diagnostic sign unlike Lyme bulls eye rash or RMSF petechial rash Monocytic ehrlichiosis is an emerging disease in the US Human granulocytic Anaplasmosis Vector Ixodes scapularis Pathogen Anaplasma phagocytophila Reservoir white footed mouse Same ecology as Lyme disease however much less prevalent Why White footed mice are able to infect vectors for only 5 10 days before their immune system contains the infection so few ticks can be infected per reservoir host Mice infected with Lyme are able to infect vectors for the rest of their life immune system does not eliminate Borrelia infection so many ticks can feed become infected