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H C Gibbs

Publications and source records attributed to H C Gibbs.

At least 37 records · Page 2Linked to original sources
PubMed1986

Long-term population dynamics of pinworms (Syphacia obvelata and Aspiculuris tetraptera) in mice.

The population dynamics of concurrent infections of Syphacia obvelata and Aspiculuris tetraptera (Nematoda) in laboratory mice were investigated under conditions of constant re-exposure over periods of 56 and 115 days. The results indicate that A. tetraptera burdens equilibrate at a higher level than S. obvelata burdens and that both parasites become aggregated in the mouse population. Parasite burdens were higher following short-term (7 day) exposure of uninfected tracer mice to both parasites when compared with parasite burdens attained over long-term exposure, indicating probable development of immunity. A significant positive correlation was detected between numbers of immature S. obvelata and immature A. tetraptera for both experimental and tracer mice.

Animals↗
PubMed1985

Effectiveness of a slow-release, morantel tartrate anthelmintic bolus for controlling parasitic gastroenteritis in replacement dairy heifers.

Two experiments were done to evaluate the effectiveness of a slow-release, morantel tartrate, anthelmintic bolus for controlling parasitic gastroenteritis in replacement dairy heifers. In experiment 1, good control of nematode contamination of pasture was indicated by lower worm burdens in tracer calves that grazed with 15 heifers treated orally with a single bolus and by significantly decreased numbers of nematode eggs in the feces of the 15 treated heifers, as compared with numbers of eggs in the feces of 15 nontreated control calves. Significant differences in weight gain were not seen between treated and nontreated heifers, probably due to low amounts of larval exposure, the small number of heifers evaluated, and parasitic resistance in the heifers, which may have developed as a result of prestudy exposure to contaminated pasture. In experiment 2, done 1 year after the 1st experiment, using the same pastures that were used in experiment 1, young heifers were used. Many of the heifers were parasite naive at the beginning of the experiment (ie, nematode eggs were not found before the experiment). Treatment with the bolus was effective in controlling parasitic gastroenteritis in the heifers and in controlling nematode contamination of pasture. Compared with nontreated heifers, treated heifers had significantly higher cumulative weight gains, a significant decrease in plasma pepsinogen concentrations, and a significant decrease in worm egg excretion. The number of worms acquired by tracer calves that were grazed with treated heifers was significantly less than for tracer calves that were grazed with nontreated heifers.

Animals↗
PubMed1982

Gastrointestinal nematodiasis in dairy cattle.

Infection with gastrointestinal nematode parasites appears to be widespread in the cattle population. The pathologically important genera of worms all belong to the family Trichostrongylidae. The most pathogenic species is Ostertagia ostertagi, which can produce profound changes in abomasal mucosa of affected animals. These nematodes show developmental adaptations, such as seasonally arrested development, that are of prime importance to their survival and persistence on a year to year basis. Whereas nematode prevalence in cattle is high, their association with outbreaks of clinical disease is lower. This has focused attention on their so-called subclinical effects, particularly reduction of milk production in lactating cows. Evidence for this effect is still equivocal, but constant exposure to low infection apparently can depress milk production. Subclinical effects also have been demonstrated in young animals and include depressed rates of gain and interference in energy and nitrogen metabolism. Evidence suggests that these effects may be partly due to hypersensitivity reactions at the mucosal level in sensitized animals.

Age Factors↗
PubMed1981

Effects of naturally acquired mixed helminth parasitism in yearling dairy calves.

The effects of Strongyle parasitism were studied in yearling calves. One group (4 calves) was a noninfected control, and 2 groups (4 calves each) were infected by exposure on pasture to the same type and degree of parasitism. One of the 2 infected groups were given coumafos at 4-week intervals and the other was not treated. Few significant differences were found between the control and infected groups in hematologic and serum glucose and urea nitrogen values. The control group gained an average of 2.2 kg/week, as compared with 1.0 kg/week, as compared with 1.0 kg/week for the treated group. The parasitized-untreated group lost 0.2 kg/week. Overall, the control group gained 26.8 kg for the 12-week period, which was significantly different (P less than 0.05) from an 11.4-kg gain by the parasitized-treated group and a 2.3 kg loss for the parasitized-untreated group. In the face of constant pasture challenge exposure, most adult worms were eliminated from the drug-treated animals, but the adverse effects of parasitism were not reversed.

Animals↗
PubMed1981

Effects of clinical and subclinical gastrointestinal helminthiasis on digestion and energy metabolism in calves.

Digestion and energy metabolism trials were conducted in 2 groups of 4 steer calves each, experimentally infected with Cooperia and Ostertagia larvae. In group 1 calves given an amount expected to cause clinical parasitism (8,000 larvae/kg 0.75), fed intake and nutrient digestibility were significant (P less than 0.05) depressed at postinfection week (PIW) 3 (the time that infections became patent); nitrogen balance in these calves were also low. The apparent absorbed nitrogen fraction was significant (P less than 0.05) depressed because of a significant (P less than 0.05) decrease in digestion. Protein catabolism was also increased. Although energy balance was significantly depressed at PIW 3, the calves seemed to recover from the effects of parasitism by PIW 5. In group 1 calves, weight gains were significantly (P less than 0.05) depressed, with mean weight gains of 10.68 kg of body weight as compared with gains of 41.44 kg for group 3 calves (noninfected controls). In group 2 calves given an amount expected to cause a subclinical infection (800 larvae/kg 0.75), nitrogen absorption was significantly (P less than 0.05) depressed at PIW 2 and 3 and energy balance was significantly (P less than 0.05) depressed at PIW 3. In group 2 calves, mean weight gains (34.76 kg) were less than were those for group 3 calves (41.44 kg). The degree of parasitism seen in group 2 calves was comparable with that observed in field examinations of naturally infected calves of approximately the same age. Seemingly, under grazing conditions in Maine, these low levels of parasitism could result in appreciable production losses in young animals.

Animals↗
PubMed1980

Persistence on pasture of the infective larvae of nematodes parasitizing Maine dairy cattle.

Yearling calves infected with Ostertagia ostertagi, Cooperia oncophora, and Nematodirus helvetianus were allowed to graze on a 0.8 ha pasture plot contaminated during June and August 1977. In June 1978, the plot was subdivided into 10 subplots of equal size. Grazing in 5 of these plots was allowed, each for 1 month, during June, July, August, September, and October by groups of 2 parasite-free 16-week-old calves. The procedure was repeated in 1979 with the remaining 5 subplots. Each group of calves was allowed to graze for 2 weeks, then put into stalls for 2 weeks and killed and examined for worms. There was a good survival of the 3 worm genera over the winter period of 1977-78. In June, calves averaged 250 Ostertagia, 5,345 Cooperia, and 6,955 Nematodirus. Ostertagia and Cooperia were recovered from calves grazing in September and October. The 3rd genus, Nematodirus, also became less plentiful over the summer period, but persisted in calves grazing during September and October. This genus survived a 2nd winter on pasture and worms were recovered until July, 1979.

Animals↗
PubMed1979

Relative importance of winter survival of larval nematodes in pasture and infected carrier calves in a study of parasitic gastroenteritis in calves.

A study was done in Maine to determine the relative importance of winter survival of nematode larvae in pasture and infected carrier animals as sources of infection for susceptible calves. Under the conditions of the experiment, it appeared that winter survivals in pasture of the infective stages of the genera Ostertagia, Cooperia, Nematodirus, and Trichostrongylus were of greater importance than carrier animals as sources of infection for susceptible calves. While animals in plots infected the previous summer and simultaneously allowed to graze alongside infected carrier animals did show more worms than those grazed only in infected plots, these differences were not statistically significant. Both groups had significantly (P greater than 0.01) more worms than did calves grazed only with carrier animals for the period of the experiment (8 weeks). It was also observed that carrier calves with low fecal egg counts (less than 200 eggs/g of feces) introduced in early spring to uncontaminated pasture could produce enough parasitic contamination by early fall to cause fulminating infections in susceptible calves grazing the pasture at the same time. Infected animals that survived clinical disease during their 1st summer developed a strong immunity which limited their acquisition of further infections when they were exposed to severe pasture contamination the following year.

Animals↗
PubMed1978

Avian cholera in eider ducks in Maine.

Outbreaks of avian cholera (Pasteurella multocida) occur frequently in common eiders (Somateria mollissima dresseri) in Maine during early summer. Studies over a seven year period show that over 90% of the loss occurred in incubating females and might be associated with their weakened condition because females do not feed during the incubation period. High nesting densities also may contribute to the losses. The exact source of P. multocida is unknown although carrier birds were found.

Animals↗
PubMed1977

Seasonal changes in stomach worms (Obeliscoides cuniculi) in snowshoe hares in Maine.

The stomachs of 141 (96.5%) of 146 snowshoe hares (Lepus americanus) collected in the area of East Corinth, Maine between the months of February, 1972 and February, 1973 were infected with Obeliscoides cuniculi. Nematodes were counted in 140 infected adult hares. The greatest intensity of infection occurred during the period from spring into summer (March to July) and at this time the populations of nematodes were mainly adults. During this period, female hares harbored significantly greater numbers of nematodes than males. Lowest numbers of nematodes were seen in late fall and early winter (October to December). The proportions of immature (fourth stage) nematodes in the populations increased appreciably from late summer on into winter and by December these constituted some 60% of the total population. A marked decline in immature nematode numbers was observed after February, with a concurrent increase in numbers of adults. A well-defined cyclical population fluctuation in natural infections of O. cuniculi was evident.

Animals↗
PubMed1977

Occurrence and seasonal behavior of gastrointestinal nematodes infecting Maine dairy cattle.

Gastrointestinal tracts of 48 yearling Maine dairy cattle were examined (8 animals every 2 months) for 1 year. Adult and immature nematodes were identified and counted. Species recovered were Bunostomum phlebotomum, Cooperia mcmasteri, Cooperia oncophora, Cooperia pectinata, Cooperia punctata, Haemonchus placei, Nematodirus helvetianus, Oesophagostomum radiatum, Ostertagia circumcincta, Ostertagia lyrata, Ostertagia ostertagi, Trichostongylus axei, and Trichuris ovis. Strongyle parasitism was observed during every sampling period and the overall incidence was 93.7%. The most commonly encountered genera were Ostertagia spp (85.4%) and Cooperia spp (81.2%). Seasonal fluctuations in the worm burden of various nematodes were observed, with largest numbers seen in the fall. The incidence and degree of parasitism appeared to be related to environmental conditions. Proportions of adult and immature worms were shown to fluctuate with the time of year. Greatest numbers of immature worms were observed during the fall and winter.

Animals↗
PubMed1977

"Spring rise" in fecal nematode egg counts in sheep in Maine.

A "spring rise" in fecal nematode egg counts occurred in Maine sheep housed under conventional conditions during 2 years. Nematodes causing this increase were Haemonchus contortus in one year and Ostertagia sp in the other. The increase in egg counts was greater in sheep that lambed than in unbred sheep. Most of the eggs in the spring rise were probably produced by worms that passed the winter in developmental arrest in the sheep. Some of the female worms probably came from contaminated bedding and developed in the sheep without arrest in growth. Acquisition from contaminated bedding, therefore, should be considered as an additional factor in the epizootiologic character of the condition in Maine.

Animals↗