Serological Studies of Parasitized Cattle: II. Electrophoretic Properties of Serial Serum Samples

Electrophoretic examinations using cellulose acetate strips were made on 17 serum samples collected at two-week intervals from each of three calves before and for about four months after they were placed on parasite-infected pastures in June, 1964. Four additional serum samples taken during the winter months when the animals were stabled and two obtained after they were again exposed to infected pastures in June 1965, were also examined. Two control animals of the same age, that were placed on clean pasture in 1964 and not exposed to infected pasture until June 1965, were bled on the same dates and their sera examined in parallel. All five calves showed an increase in the proportion and amount of γ-globulin in their serum as they increased in age but the gain was greatest in the two exposed calves that developed the highest complement-fixing titres with nematode antigens. Complement-fixing titres rose slowly in the other exposed calf and its serum γ-globulin level remained relatively comparable to that of the two controls.     

Controlled field trial on the anthelmintic effectiveness of the morantel sustained-release bolus in grazing calves

The direct and indirect anthelmintic efficacies of the morantel sustained-release bolus given to calves were assessed in a 154-day controlled field trial. A permanent calf pasture (divided into 2 lots) and naturally parasitized calves were used. The medicated calves were given the bolus at the time they were placed on the pastures. Control calves did not receive anthelmintic therapy. The effectiveness of the bolus to control parasitic gastroenteritis was determined by monitoring various parasitologic determinants. The treated calves had significantly (P less than 0.01) reduced numbers of fecal nematode eggs for every posttreatment sampling period when compared with the control calves. Tracer calves, used periodically during the study to indicate pasture larval infectivities, had equivalent worm burdens at the beginning of the trial (treated vs control pasture). Tracer calves, added later in the study to the lot with treated calves, harbored 83% to 94% fewer nematodes than did their counterparts in the lot with the controls. Plasma pepsinogen concentrations, reflective of abomasal worm burden size and/or activity, were significantly higher (P less than 0.01) in the control than in the treated calves from day 54 until trial termination. At trial termination, the treated calves weighed an average of 27.8 kg more and harbored 80.9% fewer nematodes than the control calves. The morantel sustained-release bolus is an anthelmintic delivery device that has therapeutic and prophylactic antinematode activities. To achieve its optimum performance, the bolus must be used so that the epizootiologic patterns of the predominate parasitic nematodes are effectively disrupted. Generally, internal nematode parasitisms in the calf flourish during the animal's first springtime grazing period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Strategic use of anthelmintics to prevent parasitic gastroenteritis in cow-calf herds in California

On the basis of the hypothesis that the peak numbers of infective nematode third-stage larvae (L3) on herbage in winter months results from fall contamination of pastures, 2 methods to reduce fall contamination were tested. In trial 1, morantal sustained-release boluses were administered to 15 fall-calving cows on Sept 7, 1982. Fifteen untreated cows (controls) were placed on separate pastures. Numbers of L3 on herbage during the winter and spring were assessed by use of worm-free tracer calves. In trial 2, 19 cattle due to calve in the fall were administered 200 micrograms of invermectin/kg of body weight, SC, on Sept 2, 1983. Also, 17 cattle similarly were given a placebo injection and served as control animals. Treated cattle were placed on the pasture used by control cattle in trial 1 and control cattle on the pasture used by treated cattle in trial 1. Worm-free tracer calves were again used to assess numbers of L3 on herbage. In trial 1, tracer calves grazing the control animal pasture from January 14 to 28 acquired 37 times as many nematodes as did those grazing the treated animal pasture. In trial 2, the greatest difference observed was a 10-fold increase of nematodes in calves grazing control animal pastures, compared with worm numbers in tracer calves grazing the treated animal pasture.     

On the Persistence of Infective Ostertagia ostertagi, Cooperia oncophora and Nematodirus helvetianus on Pastures

By grazing parasite-free susceptible calves on naturally infected paddocks for eighteen day periods, Nematodirus helvetianus was shown to survive over two winters on marshland pastures under Maritime climatic conditions in three successive years although the numbers surviving the second winter in two of the three years were low. Climatic conditions of below normal temperatures and little snowfall would appear to have a detrimental effect on the survival of Nematodirus over a second winter although large numbers did survive one winter of such adverse weather. However, under certain conditions, large numbers of Nematodirus can overwinter two years on pastures since over 12,000 worms were picked up by individual calves grazing paddocks in 1969 which had been vacant since 1967.

The findings indicated that few, if any, Ostertagia ostertagi and Cooperia oncophora survive over a second winter under Maritime conditions. The sharp decline in numbers of infective Ostertagia and Cooperia on pastures during the first grazing season following pasture contamination observed in this and previous investigations indicate that few worms of these species survive longer than a year under Maritime conditions.

     

Efficacy of morantel against nematode populations in calves exposed on a pasture stocked for two years with morantel sustained-release bolus-treated calves

Two groups of 10 parasite-free calves were maintained either for 2 weeks on a pasture grazed by nonmedicated cattle (pasture A) or for 3 weeks on a pasture grazed by morantel sustained-release bolus-treated cattle (pasture B) for the preceding 2 years. After a 4-week holding period to allow for maturation of acquired gastrointestinal nematodes, 5 calves from each group were administered a therapeutic dose (10 mg/kg of body weight) of morantel tartrate. All calves were necropsied 1 week later, and the abomasal and small intestinal nematodes were isolated, identified, and enumerated. A comparison of efficacies between nonmedicated and morantel tartrate-treated calves of each pasture demonstrated that morantel was equally effective against the gastrointestinal nematode infections, regardless of infection source (ie, pasture A vs pasture B). The overall nematode reductions due to morantel tartrate treatment of calves that grazed pastures A and B were 98% and 96%, respectively. It was concluded that the sensitivity of gastrointestinal nematodes to morantel tartrate was not diminished in calves maintained on pasture B, which had been stocked with morantel sustained-release bolus-treated calves for the preceding 2 grazing seasons.     

PRELIMINARY OBSERVATIONS ON THE REMOVAL OF TAENIA SAGINATA EGGS FROM SEWAGE USING VARIOUS TREATMENT PROCESSES

SUMMARY Cattle were grazed for four months on pasture irrigated by effluent from activated sludge plants, a trickling filter plant, from a lagooning process or with raw sewage, and then killed and their heart, diaphragm, tongue, and muscles of their head and one forelimb were sliced and examined for Cysticercus bovis. None of the cattle grazed on pasture irrigated with effluent from lagooning were infected compared with 3.3% from the trickling filter plant, 9.0% and 12.5% from the two activated sludge plants and 30.0% of cattle on pastures irrigated with raw sewage. Of the 40 control calves killed at the time the test calves were placed on the various pastures, 2.5% were infected. It appears that modern sewage purification methods do not efficiently remove Taenia saginata from the final effluent and that prolonged settling is necessary before effluent is used to irrigate cattle pastures if C. bovis infection is to be reduced to very low levels.     

The Development, Clinical Signs and Economic Losses of Gastrointestinal Parasitism in Feeder Cattle on Irrigated and Non-irrigated Dikeland and Upland Pastures

Investigations were carried out over three grazing seasons with parasitized and treated (control) steers on irrigated and non-irrigated upland and dikeland pastures. The stocking rate in each paddock was adjusted by either adding or removing animals so as to maintain as uniform a sward and rate of grazing as possible. Animals were weighed on and off the pastures and fortnightly during the grazing seasons.

During the first grazing season clinically normal steers shedding low numbers of gastrointestinal worm eggs contaminated the parasite-free pastures sufficiently to give rise to large residual pasture infections and clinical parasitic gastroenteritis in grazing stock during the second grazing season. Worm burdens of 100,000 to 200,000 Ostertagia ostertagi and Cooperia oncophora were established in several steers showing marked clinical signs. In spite of treatments with high dosages of thiabendazole in attempts to keep worm burdens at a minimum, there was a slow but gradual buildup of pasture infections in the paddocks grazed by the control steers over the three year period.

During the second and third grazing seasons there were significant differences in the daily rate of gain between the parasitized and control animals on both upland and dikeland pastures. The parasitized groups of steers had daily rates of gain ranging from 0.29 to 0.80 pounds less than their comparable control groups.

Under Maritime conditions, irrigation did not have a consistent effect on weight gains and development of parasitism.

     

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.     

Overwintering of Bovine Gastrointestinal Nematodes in Southwestern Ontario

Several steers, reared in isolation until approximately six months of age, were placed on a small isolated enclosed pasture from late spring to late fall of 1970, 1971 and 1972. The pasture was left vacant and unused during the winters and early springs. The pasture had been used in previous years by cattle, and in the late spring of 1970 was grazed by cattle know to be passing gastrointestinal nematode eggs in their feces. The steers were slaughtered periodically, and the prevalence of nematode species in the abomasum, small intestine, and large intestine, was determined from random samples of up to 100 adult male worms from each segment. The following nematodes were found in the steers in 1971 and 1972 and survived winters on pasture: Ostertagia ostertagi, O. lyrata, Cooperia oncophora, C. mcmasteri, Nematodirus helvetianus and Trichuris discolor. Two nematodes Cooperia punctata and Bunostomum phlebotomum known to be present on pasture in 1970, since they were recovered from the steers in that year, were not found in the steers in 1971 and 1972.     

Observations on the resumption of development of inhibited Ostertagia, Cooperia and Nematodirus infections in calves stabled overwinter.

Two groups of three month old, parasite-free calves grazed a permanently infected pasture for 14 days, Group A during the first two weeks of September and Group B during early November. Half of each group was killed 14 days after removal from the pasture and the remainder stabled overwinter before slaughter and parasitological examination. Marked inhibition of development occurred for Cooperia oncophora with a variable lower level of inhibition for Ostertagia ostertagi and practically none for Nematodirus helvetianus in those calves grazing late in the fall. Under the conditions of this study, inhibited Cooperia larvae resumed development in several calves soon after they were stabled while small numbers of Ostertagia resumed development regularly during the winter and spring with a considerable number of Ostertagia still present when the calves were slaughtered at the end of the stabling period. On the other hand, Nematodirus and practically all Cooperia worms were lost during the stabling period. In three of seven calves grazing late fall pastures, large Cooperia infections were either not established or failed to become patent.     

Seasonal availability of gastrointestinal nematode larvae to cattle on pasture in the central highlands of Kenya

The type and level of infective strongylid nematode larvae on pasture were monitored fortnightly from July 1995 to June 1996 in the central highlands of Kenya. The number of larvae on pasture was moderate, reaching > 1,200 kg(-1) dry matter of grass during the period of, and soon after, the rains, and remained low in the dry seasons. The number of larvae on pasture was directly related to the rain-fall pattern which was found to be the most important factor for the development of eggs and free-living stages. Haemonchus was the predominant genus, followed in decreasing order by Trichostrongylus, Cooperia, Oesophagostomum and Bunostomum. The mean total adult worm burdens of tracer calves released at monthly intervals were related to the levels of herbage larvae and there was a positive correlation between faecal worm egg counts and worm burdens (r = 0.58) during the study period. These results indicate that a reduction in the contamination of pasture with nematode eggs before the rains could result in pastures carrying fewer larvae and thus form the basis of effective worm control programmes for cattle.     

The effectiveness of a single dose of doramectin pour-on in the control of gastrointestinal nematodes in yearling stocker cattle

Three field studies were conducted to determine the efficacy of a single dose of doramectin pour-on in the control of gastrointestinal nematode infections in yearling stocker calves on pasture. These 140-day studies were carried out between October 1995 and March 1996 in Tennessee (TN), between January and June 1997 in Louisiana (LA), and between May and September 1997 in Wisconsin (WI). Calves with patent nematode infections were equally allocated to treatments (doramectin pour-on, at 500 microg/kg body weight or untreated control) and pastures as randomized complete-block designs (LA and TN studies) or completely at random (WI study). There were six pasture replicates per treatment at each site, with each pasture replicate accommodating six calves at the TN site (36 calves per treatment), five calves at the LA site (30 calves per treatment), and seven calves at the WI site (42 calves per treatment). Fecal samples for nematode egg counts were collected on Day 0, and at 28-day intervals thereafter. Body weights were recorded on Day 0 and at 28-day intervals until study termination. Nematode egg output of the doramectin-treated groups was reduced over the entire grazing period compared to those in the untreated control groups, resulting in average daily weight-gain advantages of 0.055 kg (p < or = 0.05) for the TN study, 0.208 kg (p < or = 0.05) for the LA study, and 0.116 kg (p < or = 0.05) for the WI study.     

Gastrointestinal nematode parasites in Saskatchewan cattle: egg count distributions in beef animals.

Fecal samples were collected systematically in the spring from cows and yearlings entering, and in the fall from calves leaving, five community pastures in central Saskatchewan. Fecal samples were also collected systematically in the spring from cows entering, and in the fall from calves leaving, an experimental rotational grazing system. Samples were collected from 1398 animals and were examined by a quantitative fecal flotation technique with a sensitivity of ten eggs per gram. Distributions of nematode egg counts for 11 of the 12 cattle populations sampled were well described by a series of negative binomial distributions. A common value of k (a measure of aggregation) could be fitted to the counts from animals of all ages in four of the five community pastures, as well as to the counts from the cows from the fifth community pasture and from the rotational grazing system. A second value of k could be fitted to the counts from the calves from these two pasture. In addition, in three of the community pastures animals in the different age groups had the same mean count.     

Survival of Oocysts of Eimeria alabamensis on Pastures under Different Climatic Conditions in Sweden

The extent to which oocysts of the coccidian parasite Eimeria alabamensis can survive the winter and cause clinical coccidiosis in different parts of Sweden was investigated. Fecal samples were collected between May and July 1993 from calves on 59 farms where calves had grazed the same pasture for at least 5 consecutive years. The farms were situated in 9 regions of Sweden with different climatic conditions in the winter. On each farm, 5 samples of feces were collected from the floor of the calf-house before the calves were turned out in the spring, and again from the pasture on days 4 or 5, 8 or 9 and 10 or 11 after they were turned out. Overwintering of oocysts of E. alabamensis was considered to have occurred if an increase in the excretion rate of oocysts of this species could be demonstrated 8 to 11 days after calves had been turned out to pastures that had not been grazed since the previous autumn. Oocysts were shown to have overwintered on 27 farms, representing all 9 regions. Samples from 20 (34%) of the farms representing all the climatic regions contained more than 850000 oocysts per g of feces. This was comparable with the numbers found in animals with clinical coccidiosis due to E. alabamensis. Delaying turnout until the beginning of July did not affect the infection rate of the calves. However, calves which were turned out to pastures that had been grazed by older cattle or horses, either earlier in the spring or in previous years, excreted significantly fewer oocysts than calves which were turned out to pastures that had been grazed only by calves. A questionnaire answered by 321 dairy farmers revealed that of the 298 farmers who turned their first-season grazing cattle out to traditional pastures, 179 (60%) had used the same pasture for at least 5 years. These 179 farmers had experienced a significantly higher incidence of diarrhoea in their calves during the first 2 weeks at pasture than those farmers who had used different pastures.     

Overwintering of larvae of the cattle lungworm (Dictyocaulus viviparus) on pasture in Kentucky

Seventeen dairy calves, raised lungworm-free, were used in an experiment to determine whether lungworm (Dictyocaulus viviparus) larvae survived on a pasture in central Kentucky during the winter of 1979/1980. On Apr 22, 1980, the calves were placed on pasture. Three calves were put on pasture A, on which no cattle had grazed for over 20 years. Fourteen calves were put on pasture B, which had been vacant since Dec 12, 1979 (132 days before beginning of experiment), when several lungworm-infected calves had been removed from the pasture. Fecal samples from the 17 calves were examined for lungworm larvae at weekly intervals for about 6 weeks; lungworm larvae were not found in any of the 3 calves on pasture A, but were found in 12 of 14 (86%) calves on pasture B. One calf from pasture A and 3 calves from pasture B were euthanatized 37 days after being placed on pasture; lungworms were recovered from 1 calf from pasture B.     

Dictyocaulus viviparus in calves: effect of rotational grazing on the development of infections.

A study was made of the possibility of reducing lungworm infections in young grazing calves by rotational grazing for weekly periods on six paddocks. For this purpose three groups of four calves each were grazed on separate pastures in 1989, whereas a fourth group served as a permanently housed control group. Two groups of calves were infected experimentally with six doses of 10 larvae of Dictyocaulus viviparus during the first 3 weeks on pasture. In the third group, low natural infections with overwintered larvae occurred. One of the experimentally infected groups was rotationally grazed for weekly periods on six small plots while both other groups were set-stocked. Faecal larval counts and worm counts in tracer calves demonstrated lower lungworm infections in the rotationally grazed group than in both set-stocked groups. However, the numbers of worms found after challenge infection and subsequent necropsy were relatively high in the rotationally grazed group, indicating that development of immunity was less than in both other groups. Owing to the dry weather conditions in the summer of 1989, no serious clinical signs of husk developed in any of the three groups. These dry conditions, however, did not prevent the build-up of heavy pasture infectivity with gastrointestinal nematodes resulting in heavy worm burdens and serious clinical signs in tracer calves grazing for 4 days in August and September-October, respectively. This implies that rotational grazing did not have a clear effect on build-up of gastrointestinal nematode infections.     

Grazing study in Ireland using the morantel sustained release bolus for controlling nematodiasis in calves

The morantel sustained release bolus was administered at turnout to first-season grazing calves in order to assess its efficacy in the seasonal control of infection by nematode parasites in Ireland. The pastures grazed by control calves showed a marked increase in gastrointestinal trichostrongylid infective larvae by September, while numbers of infective larvae on pasture grazed by bolus-treated calves remained at a low level throughout the grazing season. In consequence, the controls showed significantly higher worm egg counts in late season and significantly higher worm burdens (mainly Ostertagia spp) at necropsy carried out in November on representative number of principal animals selected from each group. These reduced worm burdens were attributed to the suppression of egg output during the early part of the season as a result of treatment with the morantel sustained release bolus at turnout in the spring. Pasture contamination with Dictyocaulus viviparus larvae was present on all treatment pastures. The bolus-treated calves however were subjected to an increase in D. viviparus infection which occurred on their pasture in late season after the active life of the bolus had expired. It was concluded that bolus treatment delayed (rather than prevented) the buildup of D. viviparus infection on the pasture by 60-90 days.     

Epidemiological study of parasite infection in a cow-calf beef herd in Quebec.

The patterns of gastrointestinal and pulmonary nematode infections in a previously untreated Aberdeen Angus cow-calf herd were observed between May 1988 and December 1990. The cow-calf herd and replacement heifers were on separate pastures. The relatively high mean faecal egg counts of cows and heifers at the time of turnout were mainly owing to the maturation of hypobiotic worms. The strongyle egg counts of calves began to rise soon after turnout onto pasture and reached peak levels at the end of the grazing season. The number of infective larvae on pasture was highest during September/October. Ostertagia, Cooperia and Nematodirus were the most prevalent genera found at necropsy and on pasture. Larvae of these nematodes were able to overwinter on pasture and Ostertagia larvae, additionally, were able to overwinter in the host as arrested early fourth stage larvae. The high egg output of cows at the time of turnout may serve as a source of infection for their calves and be responsible for the late-season rise in pasture larval counts.     

Excretion of Eimeria alabamensis oocysts in grazing calves and young stock

The aims of the present study were to investigate the excretion of Eimeria alabamensis oocysts by young cattle during their first grazing season and during the first 16 days of their second grazing period. In trial 1, nine first-season grazing heifers were studied and found to have become infected with E. alabamensis shortly after turnout. The next grazing period they were turned out on to a permanent pasture together with two first-season grazing calves. Faecal samples were collected before turnout and then daily from day 3 to day 16. The second-season grazing heifers excreted insignificant numbers of E. alabamensis oocysts, whereas one of the two first-season grazing calves excreted up to 703,000 oocysts/g of faeces (OPG), indicating that the pasture was contaminated. In trial 2, faecal samples were collected from 12 calves before their first turnout in May, daily from day 2 to day 20 after turnout and then once a week until the end of September. The calves grazed pastures used in previous years by first-season grazing calves. Nine of the calves developed clinical E. alabamensis coccidiosis 4-7 days after turnout and excreted more than 950,000 OPG on days 9-10. By day 17 the oocyst excretion had decreased below 900 OPG and remained low throughout the rest of the grazing season. The results of the two studies indicate that reinfections with E. alabamensis are of little clinical importance in calves grazing contaminated pastures, and that young stock infected with E. alabamensis during their first grazing season may be used to cleanse contaminated pastures without risk of developing clinical coccidiosis.     

On the Natural Seeding of Marshland Pastures with Bovine Gastrointestinal Parasites

By placing parasite-free calves in paddocks grazed by infected animals for 18 day periods at various times during the previous season it was shown that eggs of Ostertagia ostertagi, Cooperia oncophora and Nematodirus helvetianus deposited on pastures from early July to October of one year were able to survive in the Maritime area of Canada over winter either as eggs and/or larvae and contribute to residual infections on these pastures the following spring. The greatest deposition and/or survival of those eggs that were shed on pasture occurred in August and September for Cooperia and in September and October for Ostertagia. Greatest deposition of Nematodirus occurred in July and August and relatively few Nematodirus eggs shed in late September or early October were infective early in the next season.

The number of generations of worms per year was low, ranging from one to two or perhaps three per year depending on the species. There was a delay in the maturation of many worm eggs.

Residual overwintering infections play a significant role in the establishment of initial infections each summer in susceptible stock. These animals recontaminate the pastures leading to the subsequent development of large numbers of infective larvae by late summer and autumn.