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.     

Differences in susceptibility to gastrointestinal nematode infection between Angus and Brangus cattle in south Louisiana

Breed susceptibility to nematode infection was evaluated in Angus (Bos taurus) and Brangus (B. indicus crossbreed) cattle. A cow-calf herd and a yearling replacement heifer herd were monitored during one grazing season. Calves were born in March and were weaned in October. Individual rectal fecal samples were collected monthly from the two herds and processed for fecal egg counts (FEC) and coprocultures. Cow and calf FEC increased from April, reaching maximum values during the summer. Angus cows and calves had significantly (p<0.05) greater FEC than Brangus cows and calves, and Haemonchus and Cooperia were the predominant genera. Replacement heifer FEC showed a similar pattern with maximum levels during late summer/fall, and Haemonchus was the predominant genus. No significant differences were seen between breeds, however, infection levels were consistently lower in Brangus heifers. Ostertagia was present in cows and heifers only in fall/winter, which is consistent with summer inhibition. The data suggested that cows were an important source of pasture contamination for their susceptible calves and that the Brangus breed was relatively more resistant to infection. The use of B. indicus crossbreeds may help in alleviating reliance on chemical control by reducing the rate of pasture contamination and subsequent infection losses.     

Effect of ivermectin on performance of beef cattle on Georgia pastures

A total of 469 cows and calves from 2 herds, each on 6 pastures, was used to evaluate the anthelmintic efficacy and animal-performance benefits of ivermectin given subcutaneously at a dosage of 200 micrograms/kg to nursing beef calves and their dams during a grazing season. Pastures were paired across the 2 herds. Three pasture groups from 1 herd were randomly assigned to either a nonmedicated control or to a medicated group. Treatment assignments were reversed in the other herd. The control groups comprised 110 cows and 108 calves, whereas 127 cows and 124 calves were treated with ivermectin (200 micrograms/kg). The cows were treated once, in late spring, and the calves were treated twice, once in late spring and again in midsummer. Cattle from one herd were weighed on days - 12, 21, 49, 77 (day of 2nd treatment for calves), and 105, and the other herd was weighed on days - 6, 23, 57, 86 (day of 2nd treatment for calves), and 113. Rectal fecal samples for nematode egg counts were obtained from approximately 25% of the cattle in each pasture on weighing days; usually, the same cattle were sampled each time. Calves treated with ivermectin gained (P less than 0.05) more weight than control calves up to the 2nd treatment date and up to the termination of the study. There was no significant difference between treated and control cows, with regard to weight gain over either interval. Treated calves had fewer positive fecal egg counts (P less than 0.01) and passed fewer eggs (P less than 0.05) after both treatments than did control calves. There were no differences in either number of eggs or number of negative cows between treatment groups. Adverse reactions attributable to treatment were not seen.     

The use of negative binomial modelling in a longitudinal study of gastrointestinal parasite burdens in Canadian dairy cows

The epidemiology of bovine gastrointestinal nematodes was investigated through a 1-year (October 1999 to September 2000) longitudinal study in 38 Canadian dairy herds from 4 different provinces (Prince Edward Island, Quebec, Ontario, Saskatchewan). For each herd, fecal egg counts from 8 randomly selected animals were performed on a monthly or quarterly basis. Larval cultures were performed once, to determine the species breakdown of the parasites. All producers were interviewed regarding herd management practices. The observed fecal egg counts were low in this study, with a range from 0 to 419 nematode eggs per 5 g of feces. The mean count was 9.8 and the median was 1. Standard transformations failed to normalize the data, which followed an over-dispersed Poisson distribution. A zero inflated negative binomial model was applied to assess factors that would influence the fecal egg counts. Identified associations were: egg counts were lowest in the winter and highest in the late spring; first-lactation cattle had higher counts than older cows; if manure was spread mechanically on pastures used by lactating cattle the egg counts were higher; and if manure was spread on heifer-pastures, the adult cows had lower counts. In herds where pasture use was more extensive, the cattle had higher fecal egg counts. The difference in pasture exposure was found to be a main contributor to an observed difference in fecal egg counts among herds in the 4 provinces.     

Endemic avian toxoplasmosis on a farm in Illinois: clinical disease, diagnosis, biologic and genetic characteristics of Toxoplasma gondii isolates from chickens (Gallus domesticus), and a goose (Anser anser)

This study evaluated potential relationships between parasite egg/oocyst outputs in cow-calf beef herds located within the United States Northern Great Plains and herd longitude and latitude. Management of study herds was typical of herds from this region. Parasite egg/oocyst counts were measured from 10 cows and 5 calves selected from each herd near the end of the traditional grazing season (October 1993). The types and numbers of eggs and oocysts recovered from both cows and spring-born calves were consistent with those described in other studies. No significant relationship between fecal egg/oocyst counts and latitude was observed in calves or cows. Monezia egg output exhibited no significant correlation with longitude for calves or cows. In cows, a significant negative correlation was detected between coccidian oocyst counts and herd longitude but not between helminth egg counts and longitude. In calves, Nematodirus, trichostrongyle and Trichuris egg output and coccidian oocyst output were all negatively correlated with longitude. This negative correlation suggests that nematode populations within the study area decreased slightly from an east to west direction.     

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.     

Effect of a single strategically timed dose of fenbendazole on cow and calf performance

A 168-day study was conducted to evaluate the effect of a strategically timed treatment with fenbendazole on anthelmintic efficacy and performance of beef cows and calves. Eight groups of 10 Angus cow/calf pairs were allotted on 7 May 1987 to eight similarly managed 4.86-ha pastures (bermudagrass/tall fescue) on the basis of cow age, and calf sex and weight. At that time, four groups of cows received a dose of fenbendazole (5 mg kg-1) with their calves receiving fenbendazole at the same dosage 28 days later. Treated calf average daily gain (ADG) was 0.04 kg greater (P less than 0.05) than control calves (0.82 vs. 0.78 kg) during the 168-day study. Treated cow ADG was 0.09 kg greater (P less than 0.05) than control cows (0.40 vs. 0.31 kg). Although there was a reduction (P less than 0.05) in fecal egg counts following treatment of the cows, the numbers of eggs generally were low compared with egg counts of calves. From Day 28 through Day 112 post-treatment, fecal egg counts of treated calves were lower (P less than 0.05) than those of control calves. However, fecal egg counts from treated calves increased post-treatment until there were no differences (P greater than 0.05) between treated and control calves at the end of the study. The pregnancy rate tended to be higher (P = 0.12) for treated cows (98%) than for untreated control cows (75%). The actual calving rate was higher (P = 0.03), for treated cows (90%) than for untreated control cows (68%). Results indicated that a strategic anthelmintic treatment can improve cow and calf performance, but that calves born in late winter or early spring may need more than one therapeutic dose during the nursing period on pasture.     

Comparison between tracer calves and herbage samplings for the assessment of pasture infectivity in trichostrongylosis of cattle

Two trials were designed in “Haute Normandie” to assess the value of the number of third stage larvae in herbage samples for monitoring the infection of cattle. Two techniques of sampling were used and were compared to the actual infection of tracer calves.An index of infectivity of the pasture was defined: the number of third stage larvae in 1 kg of dry matter of herbage multiplied by the quantity of grass (dry matter) ingested by calves. There was a significant correlation between this index and the actual worm burdens of tracer calves when parasites were numbered by genera, and for heerbage samplings done according to “classical” techniques. The correlation is improved when data are combined from samples taken “close to fecal pats” and “far from fecal pats”.     

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.     

Effect of ivermectin delivered from a sustained-release bolus on the productivity of beef cattle in Oregon

The effect of ivermectin delivered from a sustained-release bolus (I-SRB) on the weight gain of beef cattle through a grazing season was evaluated using 20 yearling beef steer calves randomly divided into two groups of ten animals each. Calves in the control group each received a placebo bolus, while those in the treatment group each received an I-SRB designed to release 12 mg ivermectin day-1 for approximately 90 days. All animals were weighted and samples of feces were collected from the rectum at monthly intervals, beginning on Day 0, until trial termination (Day 148). Pasture larval counts were also conducted on herbage collected on each sampling date. On Day 119, two control and two treated calves were removed from pasture, housed in isolation for 3 weeks, then necropsied for recovery of gastrointestinal nematodes. Three sets of parasite-naive tracer calves were utilized to evaluate the initial, interim and final levels of pasture contamination by nematode larvae. A fourth set was used to evaluate the level of pasture contamination the following spring. The use of the I-SRB resulted in a greater than 99% reduction in fecal egg counts of trichostrongyles and numbers of gastrointestinal nematodes in the treated principals, as well as an average daily gain advantage of 0.114 kg over the 148 day period. A 67-98% reduction in pasture larval nematode contamination occurred on pastures grazed by the treated animals, as indicated by the parasite burden in tracer calves and pasture larval counts. The treatment effect was eventually lost by the following spring since tracer calves on the treated pasture had only 33% fewer nematodes than those on the control pasture.     

Recirculating elutriator for extracting gastrointestinal nematode larvae from pasture herbage samples

Gastrointestinal nematode (GIN) parasites present an important limitation to ruminant production worldwide. Methods for quantifying infective larvae of GIN on pastures are generally tedious, time-consuming, and require bulky equipment set-ups. This limitation to expedient data collection is a bottleneck in development of pasture management practices that might reduce pasture infectivity. We modified a soil elutriator concept for extracting GIN larvae from fresh herbage samples. Elutriators were constructed from readily available parts and compared to the Baermann funnel sedimentation method for larvae extraction. More samples could be extracted per day in the elutriator than in a Baermann unit with extraction times of 8 min versus 24h, respectively. Accuracy, measured as maximum recovery of larvae seeded onto herbage samples, did not differ between extraction methods (62.3 vs. 69.8% for elutriator and Baermann, respectively, P>0.05). Larvae recovery from herbage in elutriators showed a strong log(e) relationship with extraction time (r(2)>0.98), which will allow development of accurate correction factors for specific herbages to predict total larvae densities at extraction times less than those needed for maximum recovery. An extraction time of 8 min per sample gave the best compromise of speed, accuracy, and precision as measured by regression confidence bands and root mean square error of analysis of variance. Precision of the elutriator extraction for pasture samples was comparable to published methods and was not affected by forage species or canopy strata. The elutriator method was sensitive enough to detect differences in larvae density as small as 8 larvae g(-1) DM among pasture treatments. Elutriators extracted nematode larvae from herbage samples with accuracy and precision similar to existing methods, but did it much faster. Elutriation shows promise as a rapid method for extracting infective GIN larvae from pasture herbage.     

Control of gastrointestinal parasitism with an oxfendazole pulse-release anthelmintic device

The efficacy of a pulse-release oxfendazole bolus (OPRB) against gastrointestinal nematodes was evaluated under field conditions and compared with a sustained release morantel bolus (MSRB). Three groups of 10 calves were grazed from May to September on adjacent, similarly contaminated 3-acre paddocks. One group was dosed at turnout with the OPRB, the second group with the MSRB and the third group left as nontreated controls. Pasture larval counts peaked at greater than 60,000 larvae/kg dry weight of herbage in September on the control paddock, associated with a mean egg count of 1040 eggs/g faeces and clinical symptoms. A low rise in larval counts occurred on the MSRB plot, and also low helminth egg counts. On the OPRB plot, pasture larvae and faecal egg counts were recorded only intermittently; the September egg counts were only 3.5% of those of the controls; serum pepsinogen data showed a similar picture. At the end of the experiment, the OPRB calves had a mean weight advantage of 40 kg over the controls, and 12 kg over the MSRB group. Feed intakes were highest in the OPRB group in July and September.     

Effect of calving period on herbage intake and nutrient turnover of Simmental and Angus suckler cows with Angus sired calves grazing subalpine and alpine pastures

Herbage intake and utilisation were measured in 12 Simmental and 12 Angus suckler cows with Angus sired calves grazing one subalpine (1000 m o.d. (ordinance datium)) and two alpine pastures (first and secondary growth; 2000 m). Calving periods were late autumn and late winter for both breeds. Herbage dry matter intake of cows and calves, determined with slow-release alkane capsules, increased from subalpine to alpine pastures from 11.9 to 15.8 and 1.1 to 3.5 kg/day, respectively. Nitrogen (N) intake was highest on regrowth pasture. Simmental cows consumed more herbage than Angus cows, even when corrected for metabolic body weight. Their calves did not differ in herbage consumption although crossbred calves had significantly higher daily gains (+16%) than Angus calves. Dam breed effects on N and phosphorous (P) excretion and N utilisation were small when corrected for differences in intake (higher in the Simmental groups). Compared to winter-calving, autumn-calving resulted in cows gaining weight but also resulted in lower daily gains of the calves despite higher herbage intake. This increased N and P losses per unit of weight gain even when calculated for cows and calves together. Accordingly, late-winter calving is advantageous for this type of alpine grazing system.     

The effectiveness of doramectin pour-on in the control of gastrointestinal nematode infections in cow-calf herds

Two field studies were conducted in the USA to determine the efficacy of a single strategically-timed dose of doramectin pour-on in the control of gastrointestinal nematodosis in beef cow-calf herds and the resultant effects on calf productivity. One study was carried out between May and October 1996 in a spring-calving herd at a site located in Idaho (ID) and the other between January and July 1997 in a fall-calving herd at a site located in Mississippi (MS). In each study, cow-calf pairs were randomly allotted by sex of calf to pastures and one of two treatment groups (doramectin pour-on at the recommended dose rate of 500 microg/kg body weight or untreated control). There were four pasture replicates per treatment at each site. Each pasture contained 12 cow-calf pairs at the ID site and 15 cow-calf pairs at the MS site. Treatment was administered to cows and calves on 21 May 1996 (ID) or 23 January 1997 (MS). Following treatment, cow-calf pairs were assigned to their designated pastures where they remained until the calves were weaned 140 (ID) or 168 (MS) days later. Cow and calf fecal egg counts and calf body weights were recorded on treatment day and then at monthly intervals until study termination. Doramectin treatment reduced nematode egg output in cows and calves over the entire grazing season compared to untreated controls and resulted in calf weight gain improvements of 9.8kg (p=0.295) at the ID site and 17.4kg (p=0.0002) at the MS site.     

The effect of turn-out to pasture on blood plasma iron concentrations in beef cattle

Beef cows, bred to calve in the spring, were housed indoors over the winter. On May 25, 48 of the cows, and their calves, were put out to pasture while the other 24 cows and calves remained confined.Plasma iron concentrations in the pasture cows were higher (P<0.01) than the levels of the barn cows for several weeks after turn-out, but in September there was no difference (P>0.05). In contrast, the pasture calves showed significantly lower (P<0.01) levels than did the barn calves during the first two weeks, however, there was no difference (P>0.05) in September. No difference in plasma iron levels between male and female calves was found.     

Epidemiology of strongyles in ponies in Ontario.

The transmission of strongyles among 54 Shetland-cross mature ponies was examined from May 30 to November 22, 1983 when the ponies were on pasture and over the ensuing winter when they were in loose housing. Fecal and pasture herbage samples were taken fortnightly through the pasture season and periodically thereafter. Three foals born and reared on pasture were weaned and removed from pasture, two in early August and one in mid-September, and housed for a period before necropsy. Daily maximum and minimum air temperature and total precipitation were recorded. The mean fecal strongyle egg count was highest in the spring and early summer and lowest over the winter. Few larvae were found on the herbage in late May and their numbers were near zero by the third week in June. Subsequently, the numbers increased, were highest from late August through to mid-October and then declined and were low over the winter. Few strongyles were found in two foals removed earlier in the season, and many in the one later. The transmission of strongyles appeared to occur, therefore, principally from mid-summer to mid-fall.     

Effects of ivermectin on control of gastrointestinal nematodes and weight gain in weaner-yearling beef cattle

Four groups of 16 crossbred beef calves were used in evaluating different anthelmintic treatment schedules: group 1 was given ivermectin (IVM) at weaning only (October 31) and grazed on initially safe pasture; group 2 was given IVM at weaning, on January 28, and on April 22, and grazed on contaminated pasture; and group 3 was given IVM at weaning and on April 22, and grazed on contaminated pasture; and group-4 was group treated with fenbendazole (FBZ) at weaning only, with provision for individual salvage treatment, and grazed on contaminated pasture. The investigation was from Oct 31, 1984, to Oct 9, 1985. Initially high fecal egg counts at weaning were more effectively reduced by IVM than by FBZ, and the effect of safe pasture was evident in minimal worm burdens in tracer calves grazed with group-1 cattle during November and least amount of weight loss in group-1 yearlings during winter. Fecal egg counts, pasture larval counts, and plasma pepsinogen concentrations remained low in group 2 after the January treatment. Fecal egg counts of the other groups increased substantially during late winter and spring, but pasture larval counts increased only on group-1 and group-4 pastures. During spring, highest worm burdens were found in group-1 and group-4 tracer calves (grazed in April) and in group-3 and group-4 yearlings (slaughtered in early April). Six cattle of group 4 were salvage treated with FBZ in February and April. Greatest gains were observed from March through June, with group-2 and group-1 cattle gaining the most.(ABSTRACT TRUNCATED AT 250 WORDS)     

Control of gastrointestinal nematodes in first season grazing calves by two strategic treatments with eprinomectin

A study was carried out to evaluate the effects of strategic early-season treatments with eprinomectin on first-season grazing calves exposed to strongyle infections on a naturally contaminated pasture. Two groups of first grazing season (FGS) calves were turned out in mid-May on two plots that were similar with respect to size and herbage infectivity. They grazed separately until housing at the end of October. One of these groups was given eprinomectin pour-on at turnout and 8 weeks later, while the other group served as untreated controls. The results showed that the treatments reduced gastrointestinal strongyle infections throughout the season as evidenced by lower faecal egg counts and serum pepsinogen levels compared with the controls. Furthermore, the results of herbage larval counts and postmortem worm counts in tracer animals demonstrated that the treatment had reduced herbage infectivity on the 'treated' plot. Finally, the chemoprophylactically treated calves had a better weight gain over the duration of the study than the untreated controls.     

Epidemiological studies of Fasciola gigantica infections in cattle in the highveld and lowveld communal grazing areas of Zimbabwe

During the period between January 1999 and December 2000, the distribution and seasonal patterns of Fasciola gigantica infections in cattle in the highveld and lowveld communal grazing areas of Zimbabwe were determined through monthly coprological examination. Cattle faecal samples were collected from 12 and nine dipping sites in the highveld and lowveld communal grazing areas respectively. Patterns of distribution and seasonal fluctuations of the intermediate host-snail populations and the climatic factors influencing the distribution were also determined by sampling at monthly intervals for a period of 24 months (November 1998 to October 2000) in six dams and six streams in the highveld and in nine dams in the lowveld communal grazing areas. Each site was sampled for relative snail density and the vegetation cover and type, physical and chemical properties of water, and mean monthly rainfall and temperature were recorded. Aquatic vegetation and grass samples 0-1 m from the edges of the snail habitats were collected monthly to determine the presence or absence of F. gigantica metacercariae. Snails collected at the same time were individually checked for the emergence of larval stages of F. gigantica. A total of 16264 (calves 5418; weaners 5461 and adults 5385) faecal samples were collected during the entire period of the study and 2500 (15.4%) of the samples were positive for F. gigantica eggs. Significantly higher prevalences were found in the highveld compared to the lowveld (P < 0.001), for adult cattle than calves (P < 0.01) and in the wet season over the dry season (P < 0.01). Faecal egg output peaked from August/September to March/April for both years of the study. Lymnaea natalensis, the snail intermediate host of F. gigantica was recorded from the study sites with the highveld having a significantly higher abundance of the snail species than the lowveld (P < 0.01). The snail population was low between December and March and started to increase in April reaching a peak in September/October. The number of juvenile snails peaked between April and August. The mean number of snails collected was negatively correlated with rainfall and positively correlated with temperature. Mean number of snails collected was also positively correlated with Potamogeton plant species and negatively correlated with Cyperus plant species. However, none of the L. natalensis collected from the habitats were found shedding Fasciola cercariae. Metacercariae were found on herbage from the fringes of the snail habitats between February and August for both years, with most of the metacercariae concentrated on herbage 0-1 m from the banks of the habitats. Based on the findings of this study, anthelmintic treatment should be administered in December/January to control chronic and mature fasciolosis. A second treatment should be given in April/May to reduce pasture contamination and subsequently snail infection, as this is the time the snail population starts to build up. To control acute fasciolosis due to the immature liver flukes a third treatment should be given in August. The first application of molluscicides to control the snail intermediate hosts can be done in June the time when the snail is harbouring the parasite and a second application in September in order to kill new generations of infected snails     

Pilot project to investigate over-wintering of free-living gastrointestinal nematode larvae of sheep in Ontario,Canada

This study investigated the overwintering survival and infectivity of free-living gastrointestinal nematode (GIN) stages on pasture. The presence of GIN larvae was assessed on 3 sheep farms in Ontario with a reported history of clinical haemonchosis, by collecting monthly pasture samples over the winter months of 2009/2010. The infectivity of GIN larvae on spring pastures was evaluated using 16 tracer lambs. Air and soil temperature and moisture were recorded hourly. Free-living stages of Trichostrongylus spp. and Nematodirus spp. were isolated from herbage samples. Gastrointestinal nematodes were recovered from all tracer lambs on all farms; Teladorsagia sp. was the predominant species. Very low levels of Haemonchus contortus were recovered from 1 animal on 1 farm. The results suggest that Haemonchus larvae do not survive well on pasture, while Teladorsagia sp., Trichostrongylus spp. and Nematodirus spp. are able to overwinter on pasture in Ontario and are still infective for sheep in the spring.