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The capacity of the eggs of the Rivulus cylindraceus larvivorous fish to resist partial desiccation for a certain period of time is described. It was demonstrated that while the normal development of the eggs last for approximately 14 days, the maximum time of permanence out of the water was of 70 days. Some characteristics of the R. cylindraceus, which place it among the annual fishes to be used as biological control agents, are described. The use of R. cylindraceus as bioregulator in permanent as well as temporary reservoirs is proposed.
The flow of food into a fire ant colony is a decentralized process in which a global pattern, the even distribution of food among larvae, emerges from the interactions of individuals responding to each other with relatively simple rules of thumb. A simulation of worker-larva feeding interactions (rate and duration of worker-to-larva regurgitation) was employed to resolve the effect of each behavioral component on the distribution of food among larvae during one meal. When feeding interactions between workers and larvae simulated those of the fire ant (larvae signal for feedings at rates depending upon their size and their level of hunger; workers regurgitate a small, fixed volume of food), meal size was proportional to larval size, all larvae were brought to fullness together over an eight-hour period and the proportion of protein in each larva's meal was proportional to that found in the environment. These patterns of food distribution among larvae were the standard against which we compared simulated interactions. When simulated larvae signaled for feedings based upon their hunger (percent of midgut emptiness) but not their size, workers required nearly 12 hours to fill the last larva and, some larvae became full far sooner than others. When simulated larvae signaled for feedings based upon their size but not their hunger, they were brought to fullness evenly over time but were grossly overfed, absorbing food that would have been stored in worker crops. Lengthening the duration of worker-to-larva regurgitation generated substantial variation in the proportion of protein in larval meals, especially among small larvae. When simulated interactions were randomized, larvae received meals that varied substantially in volume and protein, some larvae were filled far sooner than others, and workers required over 24 hours and twice as much food to bring the last larva to fullness. Variation in worker response thresholds (simulated as variable worker-larvae ratios) affected only the total time required to deliver meals to larvae, Dissecting the relationship between worker-larva feeding interactions and the distribution of protein among larvae allowed us to propose a mechanism by which colony growth and reproduction could be regulated. Copyright 1998 Academic Press
The eggs and rhabditoid larvae of canine hookworm were irradiated with ultraviolet rays for one hour at a distance of 10, 20, 30, and 40 cm. The infective stage larvae of the same parasites were irradiated for l, 3, 5 and 14 hours from the same distances. The infective larvae were also exposed under direct sunlight for l, 2, 3 and 4 hours. PARASITES: Ancylostoma caninum was used. Eggs were collected in vitro from female adult worms. The worms were kept at 37 degrees C in petri-dish filled with Kreb's Ringer solution. There was an average of two cell stages, and they were used as early as possible before the morula stage. Rhabditoid larvae were obtained by culture of the above eggs for twenty-four hours in 25 degrees C incubator. The larvae reached the infective stage in seven days culture at the same condition. IRRADIATION OF ULTRAVIOLET RAY: Kingston ultraviolet light (100 volt, 10 watt, 50 cycles, 0.230 ampere) was used. The potential U.V.R. power was 1.8 watts. The distances between the material and the light were 10, 20, 30 and 40 cm at a temperature of 25 degrees C in each case. The samples were smeared on the tile in order to keep them in saturated moisture. Fully wetted ten ply gauze was laid underneath the tile. The tile was surrounded by 2 x 5 cm rectangular piece of glass in order to prevent the spread of the larvae to the outside. All of the samples received irradiation for one hour and were cultured for a period of seven days. The hatching of the egg and the development of the larvae were observed. For the purpose of the study, the infectivity and pathogenicity of the irradiated samples, were inoculated into mice orally. The lungs, livers and carcass were examined three days after the infection. A routine pathological examination of the organs was also carried out. In order to study the eggs productivity, the larvae were given to the proper host, dog. The eggs in the feces were examined from three to 6 weeks after infection, both quantitatively and qualitatively. As a supplementary experiment, the infective larvae of canine hookworm were exposed four hours under direct sunlight (September 25), and the infectivity and pathogenicity of the host were examined. HATCHING, DEVELOPMENT AND INFECTIVITY OF IRRADIATED EGGS: Hatchability of the irradiated group for one hour according to the distance from the light to the sample were 48.0 % at 10 cm, 60.3 % at 20 cm, 85.2 % at 30 cm and 88. 2 % at 40 cm respectively. None of them developed to the infective stage. They remained rhabitoid for several days and were destroyed. None was found alive in the host. 93.0 % of the control group hatched and developed to the infective stage. DEVELOPMENT AND INFECTIVITY OF IRRADIATED RHABDITOID LARVAE: None of the irradiated group reached the infective stage. Under irradiation they coiled and died soon after straightening out again. Only the group irradiated at the distance of 40cm survived for six days. They finally granulated. There was no manifestion of irradiated larvae alive in the host tissue. LIFE SPAN, INFECTIVITY, PATHOGENICITY AND EGG-PRODUCTIVITY OF THE IRRADIATED INFECTVE STAGE LARVAE: All were destroyed in the group of fourteen hours irradiation at 40 cm distance. Thirteen precent survived in the five hours irradiation group at the same distance. The survivability of larvae was reduced by the period of irradiation and at the shortest distance. The infectivity to mice was only 0.8 % at 30 cm, and 8.2 % at 40 cm in the three hour irradiation group. The recovery of the infected larvae from the host tissues was reduced as the irradiation period was increased and the distance shortened. The pathogenicity was paralleled with the vitality of the irradiated larvae. From the groups of one hour irradiation and ten cm distance, three hour irradiation and ten to thirty cm distance, the egg-productivity was all negative. But as the irradiation period decreased and the distance lengthened the egg-productivity tended closer to normal. The infective stage larvae which were exposed to direct sunlight were destroyed within three hours, but survived 81 % in the one hour exposure group and 20 % in the two hour exposure group. The summary of the results is as follows: 1. The hatching of eggs was reduced to half for one hour irradiation at the ten cm distance. Even hatched larvae did not develop to infective stage. 2. Infectivity was inhibited by the irradiation to at the ten cm distance for one hour. About ten percent of the irradiated infective stage larvae were recovered from the infected animal among the group of 40 cm distance for one hour. The egg-productivity became lower in the group of one hour irradiation at 40 cm distance. 3. The pathogenicity of the irradiated group was mild compared to the control group. 4. The direct sunlight destroyed the infective stage larvae within three hours. In general, the ultraviolet ray showed the inhibitory action in the hatching, development, pathogenicity and egg-productivity of the hookworm. The grade was paralleled with the period of irradiation and reversed to the distance between the light and samples.
The implantation and development of intravenously injected Trichinella spiralis newborn larvae were examined in different strains of inbred mice by determining muscle larvae burden. This was compared to the numbers of muscle larvae that established after a natural infection during which a quantitative assessment of intestinal newborn larvae production was made. In most inbred strains of mice, newborn larvae do not all successfully implant in muscle. Mice of the DBA/1 strain are the most resistant to successful implantation, and C3H mice are the most permissive. This pattern is evident in the strains studied whether newborn larvae are injected intravenously or are produced by intestinal adults. Thus, after a natural infection, 100% of intestinally produced newborn larvae implanted in C3H mice, whereas in NFR 68% and DBA/1 mice 62% successfully matured in muscle. Immunity to newborn larvae could be demonstrated as early as 10 days after exposure to this stage of the life cycle. This immunity was protective against a complete challenge infection given 9 days after newborn larvae had been injected intravenously. Protection against newborn larvae was identical in male and female mice or in mice from 1 to 9 months of age. We conclude that there are two mechanisms by which mice impair newborn larvae establishment or development in muscle. The first appears to be nonimmunological (non-specific resistance), and the second is immunological. Genetically determined variation in strain-specific expression is apparent with both mechanisms. In strains displaying high intrinsic "resistance" (DBA/1), this process is likely to account for most of the 38% reduction in newborn larvae establishment in a primary infection. However, immunity against newborn larvae develops quickly enough to have a significant effect on migratory larvae in primary infections where adults persist in the intestine (e.g., the B10 congenic mice), or when high adult worm burdens delay adult worm rejection. Muscle larvae burden, therefore, reflects systemic nonspecific resistance to newborn larvae as well as immunological processes that occur in the intestine and systemically.
The objective of this study was to determine the effects of condensed tannins (CT) and an extract containing crude sesquiterpene lactones (CSL) from chicory (Cichorium intybus) on the motility of the first-(L1) and third-stage (L3) larvae of deer lungworm Dictyocaulus viviparus and the L3 larvae of gastrointestinal nematodes in vitro, using the larval migration inhibition (LMI) assay. The CT and CSL had a profound effect on the motility of the larvae displayed by their ability to inhibit larval passage through nylon mesh sieves. Incubation of lungworm L1 larvae in rumen fluid (collected from deer fed pasture) containing 100, 400 and 1000 microg CT/ml, inhibited 12, 28 and 41% of the larvae from passing through the sieves, respectively, while the incubation of L3 larvae with rumen fluid (pH 6.6) containing the same concentrations inhibited 26, 37 and 67% of L3 larvae from passing through the sieves, respectively. Gastrointestinal larvae seem more susceptible to CT than lungworm larvae especially at higher concentrations. CT inhibited 27, 56 and 73% of gastrointestinal larvae from passing through the sieves when used at a concentration of 100, 400 and 1000 microg/ml, respectively. CT were more effective (P<0.001) at reducing the motility of lungworm L1 and L3 larvae when added to the rumen fluid than when added to the abomasal fluid (pH 3.0). Addition of 2 microg polyethylene glycol/microg CT eliminated the inhibitory effect of CT against L1 and L3 larvae especially during incubation in rumen fluid, confirming the effect as due to CT. The CSL extract also showed similar inhibitory activity against L1 and L3 lungworm and L3 gastrointestinal larvae in both fluids, indicating that this extract was not affected by the pH of the fluid, and was more effective against L3 than L1 lungworm larvae. Condensed tannins appeared to be more effective than CSL at inactivating L1 and L3 lungworm and L3 gastrointestinal larvae in rumen fluid, but CSL were particularly effective against L3 lungworm larvae in abomasal fluid. Activity of these secondary compounds explains the reduced parasite problem of young deer grazing chicory.
In Hynobius retardatus, most larvae in regions of low elevation metamorphose by autumn of the same year. However, larvae of some populations found in cold, mountainous ponds cannot metamorphose within the year and become aged, overwintered larvae. Gonadal development in larvae under the age of 1 year (larvae developed from eggs spawned in the same year) and in aged, overwintered larvae (spawned and hatched in previous years) was examined at the same developmental stage (stage 63, full-grown larval stage). The number of germ cells and the cross-sectional areas of the gonads were much larger in 2-season-overwintered (third year) larvae than in larvae under the age of 1 year. To obtain reliable probes for investigating the possible contribution of TSH, FSH and LH to metamorphosis and gonadal development, cDNAs for Hynobius TSHbeta, FSHbeta and LHbeta genes were cloned. Their expressions were analyzed by means of semi-quantitative RT-PCR in larvae under the age of 1 year and in 2-season-overwintered larvae. No differences were observed in expression levels of either TSHbeta or LHbeta between larvae under the age of 1 year and the overwintered larvae. In contrast, expression of FSHbeta was much higher in the overwintered larvae than in larvae under the age of 1 year. These results suggest that gonadal development proceeds gradually with age even in the overwintered larvae, but that metamorphosis is retarded, probably due to the larvae's cold habitat. Heterochronic development of gonads and external morphology has been demonstrated in H. retardatus, suggesting a potency for neotenic reproduction in this species.
Three environmental cues influence both the entry into and exit from the developmentally arrested dispersal stage called the dauer larva: a dauer-inducing pheromone, food, and temperature. The pheromone, which is a measure of population density, induces dauer larva formation at the second (L2) molt and inhibits recovery in a dose-dependent manner. Food acts competitively to reduce the frequency of dauer larva formation and to enhance recovery. The pheromone causes a specific extension of the second larval stage, coupled with a transient decrease in the growth rate of the L2. Second-stage larvae grown in the presence of added pheromone are morphologically distinguishable from L2 larvae grown without pheromone. We have named the pre-dauer L2 larva the L2d. Commitment to dauer larva formation can occur at the L2d molt. When L2d larvae are shifted out of pheromone to a lawn of E. coli just before the L2d molt, a few worms complete development into dauer larvae. In contrast, worms are essentially committed to the non-dauer life cycle by the first larval molt if the L1 larvae are not grown in appropriately high levels of pheromone. In the presence of pheromone, the percentage of dauer larva formation is enhanced at higher temperatures within the normal growth range. Temperature down-shifts induce dauer larva recovery. Temperature-shift experiments show that the enhancement of dauer larva formation requires exposure to the higher temperature around the L1 molt. Two sensory mutants defective in thermotaxis are altered in their sensitivity to the dauer-inducing pheromone, but their pheromone response retains temperature dependence. Response of dauer larvae to environmental cues is highly age dependent, with older dauer larvae exhibiting an increased tendency to recover.
Eosinophil leukocytes have been reported to have a major role in host defense against invasive, migratory phases of helminth infestations, yet the relative larvicidal abilities of eosinophils and neutrophils have not been thoroughly examined. This study examined the killing of newborn (migratory phase) larvae of Trichinella spiralis during incubation by human granulocytes in vitro. The assay employed cultue of larvae with cells, sera, and reagents in microtiter wells with direct counting of surviving larvae after incubation. Killed larvae appeared to be lysed. Verification of the microplate assay was obtained by demonstrating complete loss of infectivity of larvae incubated with leukocytes and immune serum. In the presence of optimal immune serum concentrations, purified neutrophils or eosinophils achieved >/=95% killing of larvae at cell:larva ratios of 2,000:1 or greater. Fresh normal serum prompted slight (19%) killing by leukocytes at a cell:larva ratio of 9,000:1. Cells plus heat-inactivated normal serum and all sera preparations in the absence of leukocytes killed <8% of the larvae. The activity of immune serum was opsonic. Cells adhered to larvae that had been preincubated in immune serum, and immunofluorescent studies indicated that such preopsonized larvae were coated with immunoglobulin (Ig)G. However, preopsonized larvae lost opsonic activity and surface IgG during incubation for 3 h in medium lacking immune serum. The rate of killing was dependent on the cell:larva ratio; at high leukocyte concentrations (4,200:1), 99% were killed within 7 h; at lower cell:larva ratios, killing increased steadily during a 20-h incubation period. Killing was inhibited by 20 mug catalase, 5 mug/ml cytochalasin B, or 5muM colchicine, but was unchanged by superoxide dismutase and was enhanced by azide or cyanide. Leukocytes from a patient with chronic granulomatous disease, lacking ability to mount a normal oxidative response, demonstrated a markedly suppressed larvicidal effect. The data indicate that neutrophils are at least as effective as eosinophils in the killing of newborn larvae of T. spiralis. The killing appeared to be mediated by the oxidative metabolic burst with its generation of hydrogen peroxide.
Wild-type (Canton-S) Drosophila melanogaster larvae are generally repelled by white light. Mutant larval photokinesis A (lphA) larvae are less strongly repelled than controls. Mutant Larval photokinesis B (LphB) larvae are unresponsive to light, as are larvae from LI2, an isofemale line whose progenitors were recently derived from a natural population. To characterize the behavior of larvae from the mutant stocks and the isofemale line more precisely, we determined the range of wavelengths that repel wild-type (Canton-S) D. melanogaster larvae and identified wavelengths to which larvae are most sensitive. In comparison to adult flies, Canton-S larvae are much less sensitive to white light and respond to a narrower range of wavelengths. The wavelengths to which Canton-S larvae are maximally sensitive are 500 nm (green), 420 nm (indigo), and 380 nm (ultraviolet). Mutant lphA larvae respond abnormally to green and indigo light but are as strongly repelled by ultraviolet light as controls. In contrast, mutant LphB larvae and larvae from the LI2 isofemale line are unresponsive to green, indigo, or ultraviolet light. Thus, lphA larvae have a wavelength-specific defect, while LphB and LI2 larvae are generally unresponsive to wavelengths that repel wild-type larvae.
In 1999, an aerial application of VectoLex WDG (water-dispersible granules) at 1.68 and 0.56 kg/ha, applied against sentinel 3rd-stage larvae of Psorophora columbiae installed in 0.42-ha rice plots 48 h after treatment, provided no control at 72 and 96 h after treatment. Less than 10% reduction was obtained at both rates 8 and 9 days after treatment against larvae of Ps. columbiae installed at 7 days after treatment. In a later test, VectoLex WDG manually applied at 5.04 and 1.68 kg/ha to small rice plots containing sentinel 3rd-stage larvae of Ps. columbiae and Anopheles quadrimaculatus obtained 90 and 97% control of Ps. columbiae at both rates, respectively, 24 h after treatment. A 2nd installation of Ps. columbiae at 24 h after treatment resulted in 7% and no control at both rates, respectively, even in the presence of larval carcasses from the 1st installation. VectoLex WDG was not effective against Ps. columbiae after 24 h atter treatment at either rate. Poor control was obtained at both rates against An. quadrimaculatus 24 h and 48 h after treatment for both installations. Two types of commercial rice fields containing native populations of larvae of An. quadrimaculatus were used for field tests in Cleveland, MS. In 1999, VectoLex WDG, aerially applied at 1.68 and 0.56 kg/ha to 0.2-ha plots in a contoured rice field, produced 81 and 85% reductions in early (neonate and 1st- and 2nd-stage) larvae and 94 and 76% reductions in late (3rd- and 4th-stage) larvae 2 days after treatment, respectively. At 2 days after treatment, means for all 4 developmental groupings (early larvae, late larvae, pupae, and combined stages) were significantly higher in untreated plots. Both VectoLex WDG rates did not differ significantly from one another. At 8 days after treatment, untreated plots contained significantly greater mean numbers of early larvae, late larvae, and combined stages, whereas both VectoLex WDG treatments were not significantly different. In 2000, VectoLex WDG applied at 1.68 kg/ha to two 0.40-ha plots in a precision-leveled field yielded 59 and 100% reductions of early and late larvae, respectively, 2 days after treatment. Reduction of late larvae remained 100% at 8 days after treatment. The numbers of late larvae, pupae, and combined stages were significantly greater in the untreated plot 2 days after treatment. At 8 days after treatment, numbers of early larvae and combined stages were significantly higher in the VectoLex WDG plot, whereas numbers of late larvae were significantly higher in the untreated plot. The differences in susceptibility of Ps. columbiae and An. quadrimaculatus to VectoLex WDG could be attributed to species differences in larval feeding behavior, body positioning in the water column, and developmental time. In tests in Arkansas, Ps. columbiae were controlled more quickly, usually within 24 h of exposure, whereas the percent reduction for An. quadrimaculatus in both tests in Cleveland, MS, suggests that control of this species within the region tested required from 48 h up to 8 days of exposure.
The direct action of diethylcarbamazine (DEC) on the infective larvae of Brugia pahangi was studied. The larvae were cultured in RPMI 1640 supplemented with foetal bovine serum and antibiotics for 22 days. Most of the larvae remained alive for 8 days, but survival rate of larvae decreased rapidly from day 10 onwards. The larvae did not grow in the culture system. The addition of DEC did not affect the morbidity of the larvae and no difference was observed in the morphological characteristics between the larvae cultured in the presence or absence of DEC. The infective larvae were cultured in vitro for 5 days in the presence or absence of DEC, and inoculated into jirds. The animals were necropsied at intervals, and developing larvae and adult worms were recovered. When the larvae were cultured without DEC and then inoculated subcutaneously into jirds, 29.8% of the inoculum was recovered 3-15 days, and 25% 19-22 weeks, post-inoculation. However, when the larvae were exposed to DEC in vitro and inoculated into jirds, the rate of recovery was reduced to 25% 3-15 days post-inoculation and 2% after 19-22 weeks. When the control larvae cultured in vitro were inoculated intraperitoneally into jirds, 41.3% of inoculum was recovered 3-15 days, and 42.8% 19-22 weeks, post-inoculation. Again the corresponding value for larvae exposed to DEC in vitro was reduced to 19.8% 3-15 days, and 8% 19-22 weeks, post-inoculation. It was observed that the larvae exposed to DEC in vitro were retarded in their development in jirds.(ABSTRACT TRUNCATED AT 250 WORDS)
Infective larvae of an intestinal nematode, Strongyloides venezuelensis, enter rodent hosts percutaneously, and migrate through connective tissues and lungs. Then they arrive at the small intestine, where they reach maturity. It is not known how S. venezuelensis larvae develop during tissue migration. Here we demonstrate that tissue invasion ability of S. venezuelensis larvae changes drastically during tissue migration, and that the changes are associated with stage-specific protein expression. Infective larvae, connective tissue larvae, lung larvae, and mucosal larvae were used to infect mice by various infection methods, including percutaneous, subcutaneous, oral, and intraduodenal inoculation. Among different migration stages, only infective larvae penetrated mouse skin. Larvae, once inside the host, quickly lost skin penetration ability, which was associated with the disappearance of an infective larva-specific metalloprotease. Migrating larvae had connective tissue migration ability until in the lungs, where larvae became able to settle down in the intestinal mucosa. Lung larvae and mucosal larvae were capable of producing and secreting adhesion molecules.
Experiments were conducted to determine the effects of feeding larvae of the darkling beetle (lesser mealworm), Alphitobius diaperinus (Panzer) [Coleoptera:Tenebrionidae], to turkey poults on poult growth and of beak trimming on poult feeding on the larvae. Young turkey poults readily fed on the larvae and exhibited reduced growth in the absence of other feed. Poults 3 to 5 d old restricted to a diet of only larvae consumed 259 +/- 99 (+/- SD) larvae per poult per day and their body weights were significantly lower (mean = 30 g) at the end of the 3 d than for poults on starter feed during the same time. After return to starter feed for 16 d after feeding on larvae for 3 d, the poults did not compensate for the weight loss although weight gains were normal. Poults from 2 through 10 d of age were given a choice between starter turkey feed and darkling beetle larvae. The numbers of larvae consumed per poult per day were: 174 +/- 8 for Days 2 to 4, 221 +/- 3 for Days 5 to 7, and 189 +/- 80 for Days 8 to 10. There was no significant difference between the body weight of poults feeding on larvae and starter feed compared with that of poults consuming feed only. In the presence of larvae, the mean feed consumption per poult was lower than for poults provided with only starter feed. The beetle larvae were 68% crude protein and 21% fat (DM basis) and had higher amounts of 18 amino acids than the starter feed. Poults that were beak trimmed consumed only about one-third as many larvae as poults with intact beaks. Poults (1 to 3 d old) with intact beaks consumed 169 +/- 20 larvae per poult per day; poults with trimmed beaks consumed 58 +/- 23 larvae per poult per day.
Aseptic larvae of Anopheles stephensi and Toxorhynchites amboinensis were reared on a continuous cell line (RU TAE 12 V) from the mosquito, T. amboinensis, that grew in suspension as multicellular vesicles. Surface-sterilized eggs were hatched in a 24-well plate containing 0.2 ml of Leibovitz's L-15 medium per well and incubated in a humidified atmosphere. Toxorhynchites amboinensis eggs of 36 hr or older were placed singly to assure hatching and avoid cannibalism. Hatching rates were over 80%. All larval instars were maintained in L-15 medium at 28 C with a 12-hr photoperiod. Anopheles stephensi larvae were reared in 25-cm2 tissue culture flasks containing 10 ml of L-15 medium with 30 to 50 first and second instar larvae or 10 third and fourth instar larvae per flask. Toxorhynchites amboinensis larvae remained in the 24-well plate in 1.5 ml of medium through the second instar; third instar larvae were kept in 12-well plates (3 ml of medium per well) and transferred to 25-cm2 flasks (10 ml per flask) when they reached the fourth instar. First and second instar A. stephensi larvae were fed cultured cells once, and third or fourth instar larvae twice a day. Toxorhynchites amboinensis larvae were fed vesicles once during the first 4 days after hatching, and every 1 or 2 days thereafter. Each A. stephensi larva consumed approximately 2 X 10(6) cells, and T. amboinensis larvae 10 times more cells before pupating. Anopheles stephensi pupated after 7 to 8 days and adults emerged during days 9 to 11. Pupation in T. amboinensis began on day 21 after hatching and adults emerged 5 days later. Cell lines isolated from A. stephensi larvae or embryos of the ticks Rhipicephalus sanguineus and Anocentor (Dermacentor) nitens supported only limited growth of A. stephensi larvae. Defibrinated hamster (Mesocricetus auratus) blood, though readily ingested, did not support the growth of A. stephensi whereas larvae reared on blood cells plus T. amboinensis cells showed limited growth.
To observe the possibility of human visceral larva migrans due to eating of raw liver of domestic animals, especially of cattle, and also to serve as a good reference for adequate sanitary measures, the investigation survey was carried out from May 1975 to May 1976. From the subjects of a l,048 inhabitants (male 558, female 490) in five localities including two Provinces and three different cities, food habit was studied by questionnaire mannual. Larvae isolated from liver tissues of cattle, and pig were identified. Experimental observation on the chicken and mice infected with Toxocara canis was undertaken to draw a assumption of possibility inducing human visceral larva migrans. The results obtained from the present study are summarized. 1. A part of Korean people has the habit to eat the livers of cattle, fowl, pig and dog raw. Eating rate of raw beef liver was 37.8% out of l,048 inhabitants, and its rate was higher markedly in male(57.7%) than in female (15. 1%), and the highest rate among the group of 31-40 years old. Eating rate of raw liver of fowl was 5.9%, pig 5.3%, and dog 2.5%. 2. Larva recovery rate from beef liver was 11.8% out of 195 samples and 72.0% of total detected 1arvae were identified as Toxocara(=Neoascaris) vitulorum. From pig liver, larvae of nematoda were found in 6.4% out of 109 samples but no larva was detected from 120 fowl livers. 3. Larvae detected from one-half of tissues and organs of infected chicken with about 2,000 Toxocara canis eggs were 8-245 in number, and 85-100% of recovered larvae were from their 1iver tissues. 4. Toxocara canis larvae, 45, 31, 42 and 23 in number at 3rd, 14th, 25th and 55th day in one-half of the tissues and organs after infection respectively, were demonstrated from the mice infected with 500 larvae collected from infected chicken liver. Most of the larvae were recovered from the carcass of the mouse. It was approved the larvae isolated from chicken possess infectivity to the mice. 5. Typical eosinophilic granulomatous change was not observed in the liver tissue of the infected chicken at 20th day after infection. As it summarized above, the liver of various domestic animals is the favorite tissue for migration of nematodes larvae. Therefore, the possibility of human visceral larva migrans may be induced due to eating of raw liver of domestic animals.