Contortus Cayugensis Research Articles

Hybridization of Australian Haemonchus placei (place, 1893), Haemonchus contortus cayugensis (Das & Whitlock, 1960) and Haemonchus contortus (Rudolphi, 1803) from Louisiana

There were distinct ecotypie differences in the ability to develop to third stage larvae at a constant 11 or 13°C for two weeks. H. conforms cayugensis could develop at both 11 and 13°C; H. contortus from Louisiana could develop at 13°C but not 11°C and H. placei could not complete development at either temperature. Eggs produced from the first cross between ecotypes had the same cold tolerance as their maternal parent. F 1 eggs were intermediate between parental ecotypes, while F 2 eggs, when fertile, developed at the same temperature as the most cold-tolerant parent in the first cross. The H. placei knobbed vulvar morph type was dominant to H. contortus cayugensis smooth morph type and recessive to the H. contortus (Louisiana) smooth morph type. Knobbed morph type of H. contortus (Louisiana) was dominant to smooth of H. contortus cayugensis. Dominance of morph type was enhanced by a matroclinous effect in the between species matings but not in the within species matings. No fertile eggs were produced by the F 1 of the mating between female H. placei × male H. contortus (Louisiana) or by the F 2 of the reciprocal mating. Reciprocal matings between H. placei × H. contortus cayugensis produced an F 1 and F 2 that had reduced fertility but were not completely sterile. No decrease in fertility was observed in the F 2 and F 1 from the H. contortus cayugensis × H. contortus(Louisiana)matings. Cytological studies revealed several kinds of meiotic disturbances in the between species F 1 and F 2. The most frequent were aneuploidy, failure of chromosome pairing, and pairing between non-homologous chromosomes. Males were more seriously affected than females by meiotic disturbances. The H. placei X chromosome appeared to be selected against by the hybrid genetic background. Within species hybrids showed no meiotic disturbances and the percentage of male offspring from these crosses was the same as for female offspring.

Genetics of vulvar morph types in Haemonchus contortus: Haemonchus contortus cayugensis from the finger lakes region of new york

The inheritance of the four most common morph types (smooth, knobbed, linguform A and B) in Haemonchus contortus cayugensis was studied by selection of offspring from females of known morph type and also by mating males from an inbred strain of linguiform A with smooth and linguiform B females. The dominance hierarchy of these characters was found to be linguiform > knobbed > smooth. Linguiform B was recessive to linguiform A but neither character is expressed in the presence of the smooth morph type.

Response of Haemonchus contortus cayugensis to a change in the ratio of smooth to linguiform

The equilibrium of vulvar phenotypes in Haemonchus contortus cayugensis was changed by infecting lambs with either a selected strain of smooth or of linguiform worms. Subsequently the lambs grazed the same pasture and observations were made on changes in worm populations in the lambs, and on pasture it appeared that the seasonal change in the relative frequencies of A and B linguiform worms was related to density-dependent factors in the host. In the spring, when lambs first become infected, the worm population is small and the majority of linguiform worms are A-type. As the season progresses the density of the parasite population increases. Once the population becomes crowded selection begins to favour the B-type females. The effects of crowding on linguiform A females can be seen as a positive correlation between the percentage of linguiform A and their weight. Population density also affected the survival of A-type worms since there was a negative correlation of percentage A-type on total worm numbers. There was a similar negative correlation between percentage A-type on total worm numbers. There was a similar negative correlation between percentage A-type and total worm numbers in both the continuously infected and tracer lambs. Population density did not affect the proportion of smooth worms. However, smooth worms increased in the tracers from approximately 10% at the beginning of the experiment to 55% at its conclusion 18 weeks later. The latter percentage is almost within range of the local subspecies, which has 60% or more smooth worms. It appears therefore that the proportion of smooth to linguiform worms is a stable equilibrium maintained by natural selection.

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.

Optimum temperature for egg development of phenotypes in haemonchus contortus cayugensis as determined by arrhenius diagrams and sacher's entropy function

Lejambre L. P. and Whitlock J. H. 1973. Optimum temperature for egg development of phenotypes in Haemonchus contortus cayugensis as determined by Arrhenius diagrams and Sacher's entropy function. International Journal for Parasitology 3: 299–310. Oxygen uptake, maturation time and percentage hatch were determined on eggs from “wild-type” Haemonchus contortus cayugensis populations as well as those from the morph types smooth, linguiform B and linguiform A. Sacher's organizational entropy, which is essentially a sum of oxygen utilized by a system corrected for the number of viable units in the system, was used to determine the optimum temperature for development of the eggs. Although the eggs from “wild-type” H. contortus cayugensis hatched well across a broad temperature range; individual phenotypes showed a much narrower range. The optimum temperature for the development of eggs from smooth worms was approximately 30°C while linguiform A and B hatched best at 25°C. Linguiform A eggs had a broader temperature tolerance than linguiform B so that at temperatures of 17°C they hatched with a greater efficiency than did either smooth or linguiform B. It is argued that H. contortus follows a “strategy” of having many phenotypes, each one of which appears to be adapted to a different temperature. This would allow a population to maintain a broad range of optimal temperatures without the expense of maintaining the cybernetic machinery which a single individual would have to have if it were to tolerate the same range of temperature.

Evidence that the seasonal alternation of polymorphs apparent in linguiform H. contortus cayugensis also occurs in the other phenotypes

Evidence that the seasonal alternation of polymorphs apparent in linguiform H. contortus cayugensis also occurs in the other phenotypes

Analyses of Supernatant Fluids from Exsheathing Infective Haemonchus contortus cayugensis Larvae

Infective Haemonchus contortus cayugensis larvae were exsheathed and the supernatant fluids from such exsheathed larvae were harvested for determinations of bacteria, leucine aminopeptidase, and exsheathing activity. Supernatant fluids harvested after increasing incubation time contained increasing amounts of total nitrogen and Lowry protein, but the bacteria counts were constant. It was concluded that our system of ecdysis was unsuitable for the multiplication of bacteria. Small traces of leucine aminopeptidase were demonstrated only inconsistently in supernatant fluids concentrated to 1 mg protein/ml and harvested after the larvae were incubated for 20 min. However, the concentrated supernatant fluids produced refractile rings in sheaths dissected from infective larvae. A 20-min-incubation concentrated supernatant fluid showed much higher exsheathing activity than a 6-hr-incubation concentrated fluid. Slocombe and Whitlock (1969, 1970b) detailed a method for rapid ecdysis (20-min) of infective larvae of Haemonchus contortus cayugensis Das and Whitlock, 1960. Slocombe and Whitlock (1971) presented some nitrogen and protein analyses of supernatant fluids harvested from such exsheathed larvae. We now present analyses for bacteria, leucine aminopeptidase in, and exsheathing activity of, the supernatant fluids from larvae which were exsheathed and were incubated for varying periods before harvest of the supernatant fluids. MATERIALS AND METHODS Feces were collected from sheep infected with H. contortus cayugensis and were prepared for culture (Slocombe, 1969). The cultures were incubated, harvested, cleaned, and stored as described by Slocombe and Whitlock (1970a). When required 1 X 106 ? 6% infective larvae were exsheathed as a unit. The larvae were prepared for exsheathment and then exsheathed with 10 ml 0.02 M Na2B407'101 H20. The exsheathment rate was determined. Then the clear supernatant fluid from incubated exsheathed or unexsheathed larvae was harvested, and the total nitrogen and Lowry protein content of the clear supernatant fluid estimated (Slocombe and Whitlock, 1971). The number of bacteria, the amount of leucine aminopeptidase, and the exsheathing activity of the supernatant fluid were estimated as described below. Received for publication 24 November 1970. * Present address: Department of Pathology, Ontario Veterinary College, University of Guelph, Guelph, Ontario. This investigation was supported by the State of New York, The NSF (GB-3697), and NIHGRS, 466-001-74-604. Bacterial counts Counts of bacteria were conducted on the supernatant fluid harvested after several different experiments. The fluid was diluted with sufficient sterile physiological saline to display 30 to 200 organisms per 0.7 ml of diluted fluid, when such an aliquot was flooded over an agar plate and was incubated for 48 hr at 38 C. The counts were subjected to a square root transformation for statistical analysis. In Experiment 1, the larval units were prepared for exsheathment by washing them either 3 or 15 times with sterile 0.05% NaCl. The larvae were then exsheathed and were incubated for 20 min. In Experiments 2 and 3, the larval units were washed 3 times and then were exsheathed and were incubated for either 20 min, 1, 3, 6, or 24 hr. Leucine aminopeptidase (LAP) determination LAP activity of the supernatant fluid was assayed using a kit, containing reagents for the test and a standard curve, supplied by Sigma Chemical Company, St. Louis, Missouri. The technique, essentially a modification of the colorimetric method of Goldbarg and Rutenburg (1958), utilized the enzyme to catalyze the following reaction: L-Leucyl-B-Naphthylamide + LAP H20 > Leucine + B-Naphthylamine The colorless B-Naphthylamine was then diazotized and combined with a dye. B-Naphthylamine + NaNO2 + Dye Base ---> Blue Dye. The optical density of the dye produced was proportional to the amount of B-Naphthylamine which in turn depended on the LAP activity. These procedures were outlined by Sigma Chemical Co., for the determination of LAP activity in serum (Sigma Technical Bulletin Number 251, 1969), and were followed with one modification for assaying the LAP activity of the supernatant fluid. Instead of

The influence of pCO2 and the rate of shaking on the ecdysis of infective Haemonchus contortus cayugensis larvae

Infective Haemonchus contortus cayugensis larvae were stimulated to exsheath in 0·02 m-Na2B4O7. 10H2O saturated with varying concentrations of CO2. Larvae stimulated to exsheath with 40% CO2 gave a higher exsheathment rate than larvae stimulated with 99·95 % CO2. There was a linear relationship between the exsheathment rate and the shaking rate over the range from 40 to 100 c/min when the larvae were stimulated to exsheath with 99·95 % CO2.

The inhibitory effect of CO2 on the ecdysis of infective Haemonchus contortus cayugensis larvae.

Infective Haemonchus contortus cayugensis larvae were stimulated to exsheath in 0·02 m-Na2B4O7. 10H2O, into which was bubbled CO2. The larvae under the exsheathing stimulus were found to be coiled and sluggish. The larvae became very active after most of the CO2 was removed by compressed air, oxygen or nitrogen. The exsheathment rate in each of the latter instances was higher than when larvae were exsheathed completely in an atmosphere of CO2. Carbon dioxide is an essential component of the exsheathing stimulus, but the continued presence of a high pCO2 or carbonic reaction products appeared to inhibit larval motility and caused lower exsheathment rates.

The effects of larval age and cold storage on the ecdysis of infective Haemonchus contortus cayugensis larvae.

Infective Haemonchus contortus cayugensis larvae were harvested from faecal cultures, cleaned and stored at 4°C. By means of small sample runs, exsheathment rates were determined for batches of clean larvae prior to and during storage. The larvae were stimulated to exsheath at 40°C in 0·02 m-Na2B4O7. 10H2O into which a gas mixture of 40% CO2–60% N2 was bubbled. A 20 and 60 min exsheathing time produced some and no decrease in exsheathment rates respectively for freshly cleaned unstored larvae and larvae stored 1–12 weeks. In all instances there was a reduction in the exsheathment rate 24 h after the larvae were placed in cold storage. This was considered a result of a cold shock from which the larvae did not recover until after the fourth day.

The development of a standard method for rapid ecdysis of infective Haemonchus contortus cayugensis larvae

Infective Haemonchus contortus cayugensis larvae were rapidly exsheathed (20 min) using 0·02 m-Na2B4O7. 10H2O, a gas mixture of 40 % CO2–60 % N2, and subsequent aeration with compressed air as reported previously. Several variables in this system were examined. The optimum concentration of sodium tetraborate was found to be 0·02 m. The exsheathment rate decreased with increasing molarities of the salt over the range 0·02–0·08 m. Exsheathment rates were low when the larvae received the full stimulus to exsheath for only 5 and 10 min before aeration. The larvae required at least 15 min of the full stimulus before aeration to ensure high exsheathment rates. The rapid method of ecdysis caused no abnormalities in or death of larvae, and all the larvae at the end of the incubation period were very motile and appeared normal. The exsheathment rate was consistently high as the larval concentration was increased from 2 ×103 to 2×106/10 ml of 0·02 m-Na2B4O7. 10H2O.

Effects of Heat and Lugol's Iodine on the Evaluation of Ecdysis of Infective Haemonchus contortus cayugensis Larvae

Effects of Heat and Lugol's Iodine on the Evaluation of Ecdysis of Infective Haemonchus contortus cayugensis Larvae