Parasite Biomass Research Articles

Biological controls in mixed trichostrongyle infections

The parasite reaction phenotype of 80 lambs was determined with natural infection on pasture. These lambs were then assigned to outcome groups and randomized into treatment groups. Developing some simple but unusual analytical techniques it was possible to demonstrate that mixed natural infections of trichostrongyles with the chief biomass component Haemonchus contortus cayugensis protected against superinfections with 35000 infective larvae but protected against superinfections with 1000 infective larvae per day only within the limits characteristic of the enclosing barn ecosystem. The limits of the barn ecosystem were less constraining on more diathetic sheep than the natural pasture infection. Internal evidence from the experiment suggests that the interaction of sheep X pasture X infective trichostrongylid larvae constrains the parasite biomass in the host in more diathetic animals at significantly lower levels. Anaphylactoid 'self-cure' did not occur in this experiment but something like premunition certainly did.

Host-Parasite Relationship in Echinococcosis. I. Parasite Biomass and Antibody Response in Three Strains of Inbred Mice against Graded Doses of Echinococcus multilocularis Cysts

Susceptibility studies in C57L, DBA, and C57B1 mice, infected intraperitoneally with 1, 5, 20, and 100 cysts of Echinococcus multilocularis, showed a significant difference in the cyst weights, after a 12-week period. With all 4 inocula C57L mice supported a greater larval load than DBA and C57B1 mice. Sera obtained at 2, 4, 8, and 12 weeks postinfection (p.i.) from these mice showed hemagglutinating antibodies (HAA) only at 12 weeks p.i. in the 1and 5-cyst groups of mice but much earlier in the 20and 100-cyst groups. C57L and DBA mice showed similar HAA titers and had 1 to 4 precipitin bands depending on the stage of infection. These results are discussed with regard to a possible nonprotective role of antibodies in echinococcosis. No specific data are available on the functional relationship between the immune mechanisms of the host in either unilocular (Echinococcus granulosus) or the alveolar (E. multilocularis) types of hydatid disease. The former species has been of continuing interest because of its worldwide distribution and consequent higher incidence of infection in man and animals (Kagan, 1968; Gore et al., 1970; Williams et al., 1971). In recent years screening of experimental animals for laboratory maintenance and studies on the histogenesis of E. multilocularis have been described (Rausch, 1954; Yamashita et al., 1958; Lubinsky, 1964; Webster and Cameron, 1961), but quantitative data on parasite burden, antibody response, and ensuing immunopathological changes in response to various infective inocula in inbred strains of laboratory animals are lacking. The development of an experimental model using an inbred strain of mice and establishment of measurable parameters in order to study the host response or, conversely, the apparent inability of suitable strains of mice to contain rapid proliferation and elimination of alveolar cysts, appear to be in order. This paper reports the parasite biomass and antibody response in three strains of mice against variable inocula of E. multilocularis

Energetics of a Host-Parasite Relationship as Illustrated by the Leech Malmiana Nuda, and the Shorthorn Sculpin Myoxocephalus Scorpius

The weekly energy budget was balanced for two groups of the sculpin, Myoxocephalus scorpius at 10ﾟC. An accurate estimate of weekly energy expenditure could be made by calculating the metabolic energy, measuring the waste production and measuring the energy incorporated into new tissue. The metabolic energy component was measured as the difference between weekly energy input and the sum of calories of growth and calories of waste production. The logarithm of the calculated respiration rate was proportional to the logarithm of body weight, and equal to approximately twice the resting respiration rate as measured in a flowing water-type respirometer. There was no significant difference between the summed components of energy expenditure and weekly energy input. -- There was a significant difference between the expected energy expenditure and the observed energy input of fish parasitized with a known weight of the leech Malmiana nuda. This difference was proportional to the biomass of parasites and equal to 2238 calories/gram of leech. -- The resting energy consumption of the leech was estimated from measurements of resting oxygen consumption. Resting oxygen consumption was proportional to weight, and environmental temperature. It was calculated that the resting leech would consume 63 m./gram/week at 10ﾟC. (equivalent to approximately 285 calories). At this rate of energy expenditure, there would be an additional 75 calories of waste produced. Growth would account for 1240 calories/gram of new tissue. -- The energy input also was estimated by measuring the amount of blood in the gut of recently fed leeches. It was observed that a leech would contain about 2 ml. of blood/gram. One ml. of blood was equal to 575 calories, resulting in an estimated energy input of approximately 1100 calories. This suggests that a leech continuously fed would absorb about 1600 calories of energy per week, or the equivalent of 2 3/4 ml. of blood. -- It was suggested that the ratio of energy loss from the host to energy expenditures of the parasite would be an indication of the degree of adaptation of the system. A well adapted host parasite relationship would exert a metabolic demand which is little more than the energy requirements of the parasite.

Changes in the distribution of Hymenolepis diminuta (Cestoda: Cyclophyllidea) within the rat intestine during prepatent development.

The changes in the distribution of Hymenolepis diminuta within the rat intestine have been followed over the period 3 to 16 days postinfection using rats, each infected with 10 cysticercoids of H. diminuta, fed ad libitum on Purina Rat Chow.The parameters investigated were distribution of scolex attachment sites in the intestine, and distribution of parasite biomass in the intestine based on strobila length, ex vivo weight distribution, and in vivo weight distribution. Both the scoleces and biomass of 3- and 5-day-old worms are concentrated in the second quarter of the intestine. The mean scolex attachment point for 5-day-old worms was 39% of the total intestinal length behind the pyloric sphincter. Between days 5 and 7 there was a marked anterior migration of the young worms, so that at 7 days the mean scolex attachment site was 15% of the total intestinal length behind the stomach. Over the same period of time the mean in vivo weight distribution moved forward from a point 44% behind the pyloric sphincter to one only 23% along the intestine. After 7 days there was a gradual posteriad spreading of the scolex attachment sites and of the parasite biomass. Hymenolepis diminuta can attach itself anywhere in the anterior 75% of the intestine, including in front of the opening of the bile duct: no worms were found in the small intestine extending back into the caecum.The pattern of migration and the changes in worm distribution in the intestine suggest that H. diminuta selects an appropriate, but changing position, on one or more of the gradients that have been demonstrated or postulated along the length of the small intestine.It is also suggested that the long-term migration during prepatent development is interrelated, but distinct from the daily migrational movements that H. diminuta undergoes within the small intestine.

Variation in the size and position of Hymenolepis diminuta (Cestoda: Cyclophyllidea) within the rat intestine

Data on the dry weight of 410 worms from both male and female rats is shown not to differ significantly from the normal (Gaussian) frequency distribution. This finding justified the use of statistics based on this function.Host body weight is shown to have a highly significant (P < 0.01) effect upon worm dry weight. The heavier the rat, the smaller the worms. An experimental design taking rat body weight into consideration is shown to be up to 36% more efficient in demonstrating differences between groups than one that ignores this source of variation. The point of scolex attachment behind the pyloric sphincter also has a significant effect (P < 0.05) upon worm dry weight. The nearer the scolex is to the stomach, the smaller the worm.The distribution of worm biomass in the intestine does not follow a normal (Gaussian) frequency, but is both asymmetrical (P < 0.001) and flattened (P < 0.001). Over 50% of the parasite biomass lies within the second quarter of the intestine. The distribution of the median points of worm strobilae in the rat intestine is also asymmetrical (P < 0.01) with a peak in the zone which represents a distance of 30–35% from the stomach.The migration of H. diminuta within the rat intestine results in the greater part of the parasite body lying in the second quarter of the intestine. The median points of the strobilae are concentrated at the junction of the first and second quarters of the intestine. This region of the rat intestine appears to offer the optimum site for the growth of H. diminuta.

Intraspecies competition in a field population of Gregopimpla himalayensis (Hymenoptera: Ichneumonidae) parasitic on Malacosoma neustria testacea (Lepidoptera: Lasiocampidae)

SummaryIntraspecies competition in a field population of Gregopimpla himalayensis (Hym.: Ichneumonidae) parasitic on the prepupae of Malacosoma neustria testacea (Lep.: Lasiocampidae) was investigated.The parasite oviposits the sufficient number of progeny (5 individuals/0.1 g dry weight of host) to exhaust a single host in a single attack. However, at the intensity less than 22–26 individuals/0.1 g d.w. of host, all individuals can emerge, i.e. density‐dependent mortality does not occur. Within this range of intensity, survival of parasite larvae is guaranteed by diminution in body size and decreasing sex ratio. In contrast, total biomass of parasites showed a peak at 5 individuals/0.1 g d.w. of host at which a single host is exhausted.Above the intensity of 22–26, extraordinary minute individuals appeared and they died before maturation.If intraspecies competition play a role in regulation of G. himalayensis population in the field, the process is usually not through density‐dependent mortality but through decreasing reproductive rate caused by decrease in the sex ratio, adult longevity and fecundity.