Host-parasite relationships of Helminths in a coyote population from Southern Texas with particular reference to the dog hookworm

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Title: Host-parasite relationships of Helminths in a coyote population from Southern Texas with particular reference to the dog hookworm
Author: Radomski, Andrew Alan
Abstract: Prior to the development of proper management and effective control programs for coyotes (Canis latrans ) , general information regarding demographic data , particularly growth rates and mortality in the neonates , must be well understood . Chapter I reviews some of the current literature pertaining to natural mortality in coyotes and present control methods used on this predator . Chapter II examines certain facets of the question of whether or not a parasite can function as a mechanism to limit the population growth rate of its vertebrate host . This study was initiated to obtain additional information to support or refute the general hypothesis of coyote population regulation by hookworm disease . The specific objectives were to : (1 ) document the effects of hookworm infection (morbidity and mortality ) on experimentally infected hand -reared coyote neonates ; (2 ) determine if selective density -dependent pathogenicity of hookworm infection occurs in coyote neonates and , if so , obtain an estimate of hookworm densities required to cause clinical signs of morbidity and to cause mortality ; and (3 ) determine if differential susceptibility exists among individuals within a litter . These objectives were accomplished by experimentally inoculated 51 captive handreared coyote neonates from a captive coyote population in Utah . The strain of infective strongyliform dog hookworm (Ancylostoma caninum ) larvae was cultured from the feces of a free -ranging coyote captured in southern Texas . Twenty -eight coyote neonates , 3 - to 4 -wk -old , were inoculated at random with 0 (control ) , 250 , 500 or 1 ,500 hookworm larvae /kg body weight to establish threshold levels of mortality . Mean weight gains and hematocrit values were recorded over a 30 -day study period . An initial threshold level of 250 to 500 hookworm larvae /kg was estimated to cause 50 % mortality (LD50 ) among neonates in Experiment I . Lesions in neonates included initial pneumonitis and pulmonary consolidation as a result of larval migration , with severe hemoglobinopathy and anemia associated with localization of hookworms in the small intestine over time . Differences in susceptibility among neonates within the same litter , as well as a more accurate estimate of hookworm larvae densities required to cause morbidity and mortality , were examined in Experiment II . Differential susceptibility was observed within litters administered the same dose of hookworm larvae . A threshold level of > 300 hookworm larvae /kg was determined to be the lethal number of hookworm larvae needed to cause mortality based upon 23 neonates in 7 different litters used in Experiment II . The absolute number of hookworms recovered in these experimental studies corresponded to the number of hookworms reported from naturally -infected free -ranging juvenile coyotes in southern Texas ; suggesting that this infection could result in densitydependent pathogenicity in natural populations of this vertebrate host . Thus , hookworm can be considered as a potential factor in the regulation of coyote population growth rates in the in southern Texas . Chapter III examines the persistence and interrelatedness of a recurrent group of macroparasitic helminths from the small intestine in a free -ranging population of coyotes in southern Texas at 4 -yr intervals (1979 to 1987 ) , as well as across seasons (spring and fall 1979 ) and over a 1 -yr period (fall 1986 and fall 1987 ) . The study was designed to strengthen the data concerning the community ecology of the intestinal helminth species operating in this host population . The priori hypothesis was that a stable recurrent group of helminth species persists over time and that the respective Helminth species in this recurrent group are stable in terms of their frequency distributions and abundances . This hypothesis was addressed by examining the effects of the intrinsic factors of host sex and age on the population dynamics of a helminth community in coyotes from southern Texas . Eight species of helminths (Alaria marciana^r A . caninum . Mesocestoides lineatus . Qncicola canis . Physaloptera rara . Taenia multiceps , T . pisiformis . and Toxascaris leonina ) composed the community occurring along the small intestinal gradient of coyotes in southern Texas . Computation of the Eager index and subsequent recurrent group analysis and rank correlations indicated the persistence of a small group of recurring species along with several affiliated species . These results provide information on the inter -relationships of these intestinal helminths that remain as a persistent recurrent group within coyotes in southern Texas and provides further documentation of the species that could most effect this coyote population (i .e . , be an additive mortality factor in conjunction with hookworm to affect host population dynamics ) .
URI: http : / /hdl .handle .net /2346 /20482
Date: 1989-08


Host-parasite relationships of Helminths in a coyote population from Southern Texas with particular reference to the dog hookworm. Master's thesis, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /20482 .

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