Effect on Virulence of Trichinella Spiralis.pdf
Effect on Virulence of Trichinella Spiralis.pdf
Effect on Virulence of Trichinella Spiralis.pdf
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The <str<strong>on</strong>g>Effect</str<strong>on</strong>g> <strong>on</strong>-<strong>Virulence</strong> <strong>of</strong> <strong>Trichinella</strong><strong>Spiralis</strong> from Passage Through Rabbits,Guinea Pigs and Rats"An AbstractBy JO S r~OLIVEH GONZALEZFrom the Department <strong>of</strong> .If edical Z oolo{/!/ I\f the School <strong>of</strong> Trop ical .Ifediciue ,San J uun, Puerto RicoVIHU L E ",.' n ; is an innate physiological potentiality which variesrapidly and significantly in any give n strain <strong>of</strong> micro -organ isms. These variati<strong>on</strong>s which occ ur under certain circ umstancesare a co mm<strong>on</strong> obse rvat i<strong>on</strong> in almost all st rains <strong>of</strong> parasiti cforms .Variati<strong>on</strong>s in the viru lence <strong>of</strong> man y organ isms are <strong>of</strong>ten broughtabout by changes in t he en vir<strong>on</strong> me rrt. In bacteri a a cha nge from ahigh to a low gra de <strong>of</strong> virulence is commo nly seen as the result <strong>of</strong> theuse <strong>of</strong> an unsui tabl e cult ure med ia, or as th e result <strong>of</strong> t he prol<strong>on</strong>gedartificial gro wth <strong>of</strong> t he organism . The change from a low to a highgra de virulence has bee n accomplished by al tering the envir<strong>on</strong>men tin wh ich th e organ ism gl'ows. P assa ges <strong>of</strong> culture through bloodser um has been found effective as a method <strong>of</strong> raising virulence.On e <strong>of</strong> the earliest known obser va ti<strong>on</strong>s <strong>on</strong> th e cha nges in viru lence<strong>of</strong> an organis m which occ urs as a resul t <strong>of</strong> animal passa ge is P asteur'swor k <strong>on</strong> rab ies. Pasteur showed that t he virus <strong>of</strong> hydrophobi awhen successively passed thro ugh rabbits gained in virulence, whilewith <strong>on</strong>ly three pa ssages t hro ugh m<strong>on</strong>keys the virul ence was reducedalmos t t o ext incti<strong>on</strong>. The sa me rcluti <strong>on</strong>ship bet ween hostand parasite also exis ts with ot her micro-organism s. The virulen ce <strong>of</strong>attenuated pneu mococci is increa sed by successive passage throughnu ce.Wi th parasitic helminth s no work has been d<strong>on</strong>e with the intenti<strong>on</strong><strong>of</strong> studying t he change in viru lence <strong>of</strong> parasites in relati<strong>on</strong> toanimal pa ssage, but with indirect ev ide nce the same c<strong>on</strong>d iti<strong>on</strong>s aswith bacteri a are kn own t o occ ur . Boyd, working with Plasmodiumpraecox in cana ries, obser ved th at the virul ence <strong>of</strong> t he parasite in cre ased by rapid passage from <strong>on</strong>e bird to a no ther ."Abstra cted from a D issert a ti<strong>on</strong> sub mitt ed to th e Faculty <strong>of</strong> the D ivisi<strong>on</strong> <strong>of</strong> the BiologicalSciences, University <strong>of</strong> Chicago, in can didacy for the Degree <strong>of</strong> ~las le r <strong>of</strong> Science, August,l!) ~l(l . . .(j1
..( ' e) l~ 'I'hc j~:trec{ Oil <strong>Virulence</strong> cd Trichi uella S piralisIn this studv <strong>of</strong> th e effec t <strong>on</strong> th e virulen ce <strong>of</strong> Trichin ella spirali«from passa ges' through rats, rabbits and guinea pigs, it. ha s beendem<strong>on</strong>strated that th e parasite suffers a gradual diminuti<strong>on</strong> illvirulence as the infecti<strong>on</strong> is passed from rabbit to rabbit and fromzuincu !Ji,,' to sruiucu pig. The loss in virulence <strong>of</strong> th e str a ins wasb b b