Control of gastrointestinal nematodes in dairy heifers by two strategic treatments with ivermectin

Dairy replacement heifers given two strategic treatments with ivermectin (0.2 mg/kg) three and eight weeks after turnout to spring pastures in northern USA had mean adjusted weight gains (62.3 kg) that were 62 per cent (P less than 0.02) greater than those of control heifers (38.5 kg) at the time of winter housing. Pasture infectivity was consistently higher in control pastures and there was a sixfold difference between treatment (56 L3/kg) and control (358 L3/kg) pastures by the time of winter housing on October 18. This study confirmed earlier studies in northern USA demonstrating the value of two strategic treatments in achieving significant increases in weight gains and hastening the time of first breeding by one to three months at a saving of $40 to $140 per heifer. It was concluded that this dosing strategy is a satisfactory method of parasite control for dairy replacement heifers in northern USA without undue selection for drug resistance.     

Efficacy of a morantel sustained-release bolus for the control of gastrointestinal nematodes in Florida dairy heifers

The effectiveness of a morantel sustained-release bolus (MSRB) in controlling gastrointestinal nematode infections was determined in 70 Holstein heifer calves with no prior grazing experience. Calves were allotted to 2 treatment groups and were maintained in Florida during the grazing season on divided pastures of equal area. One MSRB was administered to each calf in 1 group at the time of turnout onto spring pasture, whereas calves in the other group remained as nonmedicated controls. By the end of the grazing season, treatment resulted in significantly (P less than 0.05) lower worm burdens and significantly improved weight gains. The MSRB-treated calves were able to reach breeding weight 2 to 4 weeks earlier than did nonmedicated calves.     

Effect of feeding urea-molasses blocks with incorporated fenbendazole on grazing dairy heifers naturally infected with gastrointestinal nematodes

Between June 1999 and August 2000, the effects of feeding medicated urea-molasses supplement blocks on the growth of dairy heifers in a marginal area of central Kenya were assessed by comparing the live-weight gain of supplemented and unsupplemented heifers grazing the same pasture. Thirty-nine heifers with an average age of 9.6 months were initially treated orally with albendazole (10 mg/kg body weight) and assigned to 3 groups: group I was fed urea-molasses blocks with incorporated fenbendazole (MUMB), group II was fed urea-molasses blocks (UMB) and group III heifers (control) received no block supplementation (NBS). Body weights of the heifers and faecal egg counts (FECs) were measured monthly and larval cultures were made of positive faecal samples of each group. The mean cumulative live-weight responses of the MUMB and UMB groups were significantly greater than the NBS group (P < 0.05). However, at the end of the experimental period, the mean weight gain of the MUMB group did not differ from that of the UMB group (P > 0.05). The FECs were moderate to low in all groups and decreased progressively with increasing age of the animals; FECs for the urea-molasses-supplemented groups remained significantly lower than those of the NBS group throughout the experimental period (P < 0.05). Haemonchus and Trichostrongylus were the predominant nematode genera found in the heifers, but Cooperia, Bunostomum and Oesophagostomum were also present. These results indicate that feeding of urea-molasses blocks substantially reduced production losses attributable to nematode infection of young grazing cattle, and confirms previous observations that well-fed animals are better able to overcome the effects of helminth infections.     

Anthelmintic efficacy of netobimin against naturally acquired gastrointestinal nematodes in yearling heifers

The efficacy of netobimin (Coded SCH 32481, Schering Corporation) in removing naturally acquired gastrointestinal nematode infections was evaluated in 10 treated and 10 untreated (control) yearling beef heifers. The anthelmintic was administered as an oral drench at a dose level of 7.5 mg kg-1 body weight. Fecal egg per gram (EPG) counts were reduced with netobimin by 98% (P less than or equal to 0.01) at both 1 and 2 weeks post-treatment (PT). The compound was highly effective in removing Oesophagostomum radiatum (100% at P less than or equal to 0.01), Cooperia spp. (97.66% at P less than or equal to 0.01) and Nematodirus helvetianus (100%, although not significant), but was ineffective against immature Ostertagia ostertagi (3.19%) and only moderately effective against adult forms (66.14% at P less than or equal to 0.05). The low efficacy against adult O. ostertagi was partially attributed to the maturation of fourth-stage larvae, not removed by the 7.5 mg kg-1 treatment, during the 14-day treatment-slaughter interval. Efficacy against Trichuris spp. could not be evaluated due to low levels and unequal numbers of worms recovered in the groups. The overall efficacy against adult species, excluding Trichuris spp., was 67.40% (P less than or equal to 0.05). No adverse reactions or signs of toxicosis were observed in heifers treated with netobimin.     

Evaluation of the effect of eprinomectin in young dairy heifers sub-clinically infected with gastrointestinal nematodes on grazing behaviour and diet selection

Inappetence is commonly associated with parasitism and has been observed in both housed and pastured ruminants. In seeking a functional explanation for these observations, it has been hypothesised that parasitized animals may feed more selectively in order to proportionally increase the protein content of their diet and thus partially compensate for their reduced feed intake. Support for this theory is found principally in studies in housed animals under carefully controlled experimental conditions. Grazing animals face a far more heterogeneous environment and a multiplicity of potentially confounding factors that could influence diet selection. Controlled grazing of adjacent monocultures of grass and clover can mitigate some of these variables and was used in the current study to examine the dietary preference of dairy heifers with sub-clinical parasitic gastroenteritis when compared to those receiving regular anthelmintic treatments. Grazing behaviour and herbage intake rates were determined through the use of jaw-movement recorders, direct observation and short-term liveweight change. Consistent with previous observations and despite evidence that nematode burdens were low in the untreated control heifers, a reduction in daily grazing time of 56 min (P = 0.054) was observed in the control animals. There was, however, no evidence that the control heifers showed greater preference for clover compared with ryegrass: partial preference for clover was 73.0% in the untreated controls and 75.5% in the treated heifers. Furthermore control heifers were observed grazing the clover swards significantly (P = 0.032) less frequently than the treated heifers. This study provides additional evidence in grazing cattle for parasite-induced inappetence, manifest as a reduction in grazing time and in subtle changes in ingestive behaviour. The observed partial preference for clover in both treated and control cattle was not significantly affected by the level of parasitism.     

Control of nematodes in dairy heifers by prophylactic treatments with albendazole in the spring

The effect of 2 prophylactic anthelmintic treatments with albendazole (7.5 mg/kg) was evaluated in 2 groups of Holstein dairy replacement heifers treated 3 and 6 weeks after turnout to spring pasture on May 2, 1983. The lightweight group consisted of twelve 7- to 9-month-old heifers with a mean initial weight of 201.1 kg. The heavyweight group consisted of ten 11- to 15-month-old heifers with a mean weight of 319.4 kg. Within each group, the heifers were paired by initial weight, and one member of each pair was randomly assigned to the treatment group. Each of the 4 resulting groups grazed separate, contaminated pastures until winter housing on Oct 31, 1983. The albendazole-treated, lightweight heifers had bodyweight gains 28.9% greater than that of the control heifers at the end of 23 weeks (P less than 0.001). There was no significant difference in gain for the treated heavyweight heifers, which had a lower feeding rate/kg of bodyweight than did the lightweight heifers. At the end of the study, there was a sevenfold difference in mean pasture L3 counts between treatment (1,303 L3/kg) and control (9,153 L3/kg) replicates. It was concluded that it is desirable to treat all heifers in northern regions during their first spring at pasture. This strategy would likely provide substantial economic returns to the farmer in years with a wet summer, which would favor early migration of L3 to herbage, but would provide smaller returns in dry seasons, which would delay this pattern of migration.     

Local inflammation as a possible mechanism of resistance to gastrointestinal nematodes in Angus heifers

Understanding mechanisms of resistance to gastrointestinal nematodes is important in developing effective and sustainable control programs. A resource population of Angus cattle consisting of approximately 600 animals with complete pedigree records has been developed. The majority of these animals were completely characterized for their resistance to natural challenge by gastrointestinal nematodes. As the first step towards understanding the molecular basis of disease resistance, we investigated expression profiles of 17 cytokines, cytokine receptors, and chemokines using real-time RT-PCR in animals demonstrating resistance or susceptibility to pasture challenge. The animals exposed to natural infection for approximately 6 months were treated to remove existing parasites and then experimentally challenged with both Ostertagia ostertagi and Cooperia oncophora. The mRNA expression profiles of these genes in abomasal and mesenteric lymph nodes (ALN, MLN), fundic and pyloric abomasa (FA, PA), and small intestine (SI) were compared between resistant and susceptible animals. Resistant heifers exhibited elevated expression of inflammatory cytokines such as TNFalpha, IL-1beta, and MIP-1alpha in fundic and pyloric abomasa 7 days post infection. Expression levels of IL-10, polymeric immunoglobullin receptor gene (PIGR), and WSX-1 were also 2.7-19.9-folds higher in resistant than susceptible heifers in these tissues. No difference in expression of CXCL6, CXCL10, IFN-gamma, IL-2, IL-4, IL-6, IL-8, IL-12 p40, IL-13, IL-15 and IL-18 was observed between the two groups. The expression of MIP-1alpha, IL-6, and IL-10 was also elevated in small intestines in resistant animals. In contrast, little difference in expression of these genes was detected between resistant and susceptible groups in the draining lymph nodes. These data indicate that resistant animals can better maintain inflammatory responses at the site of infection, suggesting a possible novel mechanism of resistance.     

Prevalence of gastrointestinal nematodes in growing pigs in Kabale District in Uganda

During the last 30 years, pig production in Uganda and neighbouring counties has increased markedly. Pigs are mainly kept as a source of income for small-scale farmers; however, the pig production is subject to several constraints, one of them being worm infections. A study was carried out in rural communities in Kabale District in the South Western part of Uganda in September and October 2007 in order to estimate the prevalence of gastrointestinal nematode parasites in pigs based on coprological examination. Fifty-six households were randomly selected and visited. Housing system and deworming history were recorded. Faeces was sampled from rectum of one to five pigs (age, 3–12 months) per household. A total of 106 pigs were examined coprologically of which 91% excreted nematode eggs. The following prevalences of nematode eggs were recorded: strongyles (89%), Ascaris suum (40%), Trichuris suis (17%) and spiruroid eggs (48%). On household level, rearing pigs on slatted floors in pens significantly reduced the faecal egg excretion of strongyle eggs with almost 80% (p = 0.010) and a significant interaction between floor type and anthelmintic treatment was found for spiruroids (p = 0.037). Fifteen T. suis egg positive pigs were selected for post-mortem examination of the gastrointestinal tract. The post-mortem examinations revealed that 93% pigs were infected with Oesophagostomum spp. (worm burden, min–max 10–2,180), 73% with A. suum (1–36), 67% with T. suis (6–58), and 20% with Hyostrongylus rubidus (worms not quantified). In general, nematode infections were widespread and polyparasitism common in pigs in Uganda. However, worm burdens were moderate which may be related to recent deworming or to the practice of rearing pigs on slatted floors in wooden elevated pens.     

Effects of farm management practices and environmental factors on bulk tank milk antibodies against gastrointestinal nematodes in dairy farms across Canada

Enzyme-linked immunosorbent assays (ELISAs) have been used as a diagnostic tool to quantify levels of gastrointestinal nematodes in dairy cattle by measuring Ostertagia ostertagi antibodies in milk. Higher levels of O. ostertagi antibodies measured by ELISA methods, referred to as optical density ratios (ODRs), are associated with decreased milk production in dairy cattle. On-farm management practices (e.g. pasturing techniques and anthelmintic usage) can influence the exposure of cattle to nematode infections and the magnitude of acquired worm burdens. Additionally, environmental and climatic factors, such as land elevation and precipitation, may also influence the levels of gastrointestinal parasitism. This repeated cross-sectional study investigated the effect of farm management practices and surrounding environmental factors on bulk tank (BT) ODRs in herds from provinces across Canada, and further examined the potential effects of various anthelmintic treatment protocols on BT ODRs. A total of 195 herds contributed an average of 3.5 BT samples between December 2003 and April 2005. The farm management practices were recorded from a questionnaire asking producers about their pasturing methods (confined, pastured, etc.), pasture sharing practices (e.g. mixing heifers with milking cows) and anthelmintic treatments. Environmental data were downloaded online from various governmental databases (e.g. Natural Resources Canada, Statistics Canada, Environment Canada, etc.). Statistical models, accounting for repeated measures (multiple BT ODRs for each farm) and for clustering of farms within a region (province or ecoregion), were used to analyze environmental and farm management data. Overall, the greater the exposure that heifers and milking cows had to pasture, the higher the levels of anti-parasite antibodies detected in BT samples. Treating the entire herd or treating milking cows at calving reduced BT ODR values. Farms in areas with higher number of rainy days, higher normalized difference vegetation index (NDVI) values, and lower land surface temperatures (LSTs), were also likely to have higher BT ODRs. Seasonal variation was such that late summer and early fall, when parasite load was at its highest, yielded larger BT ODRs. Due to the high clustering effect at the herd level, factors at the herd level (e.g. pasturing methods, anthelmintic administration) had a higher potential impact on bulk-tank measurements than the herd's surrounding environmental factors.     

Prevalence of Cryptosporidium infection in dairy calves in western Washington

The prevalence and intensity of Cryptosporidium infection were examined in 445 Holstein calves at 10 dairy farms in western Washington, near Seattle. Fifty-one percent (176) of calves in the 7- to 21-day-old age group (n = 342) were positive for oocysts in the feces by carbolfuchsin staining. Prevalence and intensity of infection were highest in calves 8 to 14 days old; prevalence was 60% in this group, and 48% of the Cryptosporidium-positive calves had oocyst shedding at a 4+ level. A seasonal pattern in prevalence was not evident.     

A retrospective investigation of feline gastrointestinal parasites in western Canada

Between 1998 and 2008, feline fecal specimens were submitted to provincial veterinary diagnostic laboratories in Regina and Saskatoon, Saskatchewan, for sucrose centrifugation-flotation (n = 635), parasite identification (n = 17), and/or Giardia (n = 283) or Cryptosporidium (n = 266) commercial direct immunofluorescence assay (IFA). The most commonly detected parasites on flotation were Toxocara cati (4.7%), Isospora (3.8%), and taeniid eggs (Echinococcus or Taenia) (1.3%). Cats less than 2 years of age were twice as likely to have a positive parasite test as cats older than 2 years. Using IFA, Giardia was detected in 9.9% of samples, and Cryptosporidium in 2.3% of samples. Relative to IFA, flotation had sensitivity values of 39% and 50% for detection of Giardia and Cryptosporidium, respectively. Giardia and Isospora were detected in a higher proportion of samples in our study population than reported in the general cat population in western Canada. This study highlights the importance of sensitivity when interpreting diagnostic tests and provides information to guide region-specific recommendations for helminth parasite prevention and treatment.     

Prevalence and intensity of gastrointestinal nematodes in slaughter lambs from central Alberta

Two trichostronglyes, Teladorsagia ostertagi and Nematodiru helvetianus, accounted for > 99% of nematodes recovered from gastrointestinal tracts of 47 lambs pastured in central Alberta during the summer of 2000. Their prevalence and mean intensity increased from < 10% and < 50 worms/host, in late June, to > 80% and approximately 1000 worms/host, by mid-July, respectively.     

Prevalence of paratuberculosis in the dairy goat and dairy sheep industries in Ontario,Canada

A cross-sectional study was undertaken (October 2010 to August 2011) to estimate the prevalence of paratuberculosis in the small ruminant dairy industries in Ontario, Canada. Blood and feces were sampled from 580 goats and 397 sheep (lactating and 2 y of age or older) that were randomly selected from 29 randomly selected dairy goat herds and 21 convenience-selected dairy sheep flocks. Fecal samples were analyzed using bacterial culture (BD BACTEC MGIT 960) and polymerase chain reaction (Tetracore); serum samples were tested with the Prionics Parachek enzyme-linked immunosorbent assay (ELISA). Using 3-test latent class Bayesian models, true farm-level prevalence was estimated to be 83.0% [95% probability interval (PI): 62.6% to 98.1%] for dairy goats and 66.8% (95% PI: 41.6% to 91.4%) for dairy sheep. The within-farm true prevalence for dairy goats was 35.2% (95% PI: 23.0% to 49.8%) and for dairy sheep was 48.3% (95% PI: 27.6% to 74.3%). These data indicate that a paratuberculosis control program for small ruminants is needed in Ontario.     

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.     

Subclinical laminitis in dairy heifers

By causing poorer horn quality, subclinical laminitis is considered to be a major predisposing cause of other hoof problems, particularly sole ulcers in newly calved heifers. In this study the hind hooves of 136 female Friesian/Holstein cattle aged between four months and two years were examined to discover at what age the signs of subclinical laminitis appeared. Sole haemorrhages were found in the hoof horn of calves as young as five months. The consistent finding of these lesions in heifers of all ages indicated that subclinical laminitis of varying degree was a common condition during the early growing period of young dairy heifers.     

Epidemiology of gastrointestinal nematodes in cattle on traditional, small-scale dairy and large-scale dairy farms in Iringa district, Tanzania

A longitudinal study was carried out to determine the prevalence, distribution and intensity of gastrointestinal (GI) nematodes in traditional, small-scale dairy and large-scale dairy cattle farms in Iringa district, Southern highlands of Tanzania. Coprological examination of cohorts for GI nematode eggs in faeces, tracer worm counts and pasture larval counts were performed monthly for 1 year. Results indicated that the type of management, especially the grazing habit has a significant influence on the prevalence and intensity of GI nematodes. The predominant nematodes were Cooperia spp. (51.6%), Oesophagostomum radiatum (35.7%) and Haemonchus placei (10.2%). The worm burden in tracers was mainly composed of Cooperia spp. (83%) in large-scale dairy farms, while O. radiatum was dominant (60.8%) in traditional farms. Faecal egg counts (FEC) and tracer worm counts were generally low and FEC peaked only in calves and weaners/yearlings. Adults and all age groups in small-scale dairy farms had very low FEC throughout the year. Pasture larval counts, FEC and tracer worm counts peaked towards the end of the rainy season. Based on conditions of the study area, farmers could save substantial amount of money through strategic treatments as opposed to the previous routine of treating the whole herd at least four times a year. Strategic treatments are recommended in calves and weaners only in traditional and large-scale dairy farms. Strategic treatment of adults and small-scale dairy cattle might be not necessary. Strategic treatments at the end of the rainy/early dry season (May/June) and at the end of the dry/early rainy season (November/December) are recommended in the district. An additional treatment against GI nematodes in calves during the mid rainy season (February/March) might be important.     

Efficacy of morantel sustained release trilaminate bolus against gastrointestinal nematodes in grazing dairy calves in Kenya

Summary The efficacy of morantel sustained release trilaminate (MSRT) bolus against gastrointestinal nematodes was evaluated under field conditions over a 10-month period. Twenty weaner calves were randomly divided into 2 groups of 10 calves each and grazed from March to December on adjacent, similarly contaminated paddocks. Group 1 calves (T-1) served as untreated controls while group 2 calves (T-2) were dosed at turnout with MSRT bolus designed to release morantel tartrate continuously for 90 days. The efficacy of MSRT was assessed by comparison of parasitological data (faecal worm egg counts, herbage larval counts, worm counts from tracer calves and set-stocked trial calves, determination of haematological parameters and pepsinogen levels), weight gains and clinical status of the animals. Faecal egg counts from the treated group (T-2) were reduced by 100% (P < 0·001) following treatment and remained significantly (P < 0·05) lower than counts from T-1 calves up to trial termination. The use of MSRT bolus resulted in a reduction of 92% (P < 0·001) in the number of gastrointestinal nematodes in set-stocked calves at the end of the study and a 55 to 85·7% reduction in herbage larval infectivity as reflected in lowered parasite burdens in tracer calves. At the trial termination, the control calves had gained on average (± s.d.) 59·4 ± 4·8 kg (200·0 ± 7·4 g day⁻¹) and the treated ones on an average 128·6 ± 10·5 kg (530·0 ± 13·1 g day⁻¹).

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Eficacia De La Utilizacion De Bolos Trilaminados De Morantel Frente A Nematodos Gastrointestinales En Vacuno De Leche En Pastoreo En Kenya

Resumen Se evaluó la eficacia de los bolos trilaminados de liberación continua de morantel (MSRT) frente a nematodos gastrointestinales en condiciones de campo y durante un período de 10 meses. Un total de 20 terneros recién destetados fueron divididos al azar en dos grupos de 10 animales cada uno y mantenidos en pastoreo desde marzo hasta diciembre en parcelas adyacentes y con una carga parasitaria similar. Los terneros del grupo 1 (T-1) fueron los animales control y no recibieron ningun tratamiento, mientras que los terneros del grupo 2 (T-2) fueron tratados con MSRT al inicio del período de pastoreo; los MSRT estaban dise?ados para liberar tartrato de morantel de forma contínua durante 90 días. La eficacia de los MSRT se evaluó comparando datos parasitológicos (huevos en heces, larvas en el pasto, parásitos en los animales, parámetros hematológicos y niveles de pepsinógeno), ganancias de peso y datos clínicos. El número de huevos en heces en los animales T-2 se redujo en un 100% (P < 0·001) después del tratamiento y se mantuvo significativamente más bajo (P 0·05) que el de los animales T-1 durante todo el experimento. La utilización de MSRT resultó en una reducción del 92% (P < 0·001) en el número de nematodos gastrointestinales y en una reducción del 55 al 85·7% en el número de larvas en el pasto. La ganancia de peso final fue de 59·4 ± 4·8 kg en los animales T-1 (200·0 ± 7·4 g/día) y de 128·6 ± 10·5 kg en los animales T-2 (530·0 ± 13·1 g/día).

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Efficacite Du Morantel Por Voie Orale Contre Des Nematodes Gastro-Intestinaux Chez Des Veaux Laitiers Au Kenya

Résumé L’efficacité du Morantel distribué par voie orale, contre des nématodes intestinaux fut évaluéein situ sur plus de 10 mois. 20 veaux sevrés furent répartis au hasard dans 2 groupes de 10 veaux chacuns et broutèrent de Mars à Décembre sur 2 parcelles adjacentes et contaminées de fa?on identique. Le premier groupe (T-1) servit de temoin alors que le deuxième groupe (T-2) re?ut du morantel de fa?on continue pendant 90 jours. L’efficacité du Morantel fut analysée par comparaison des données parasitologiques (nombre d’oeufs de nématode dans les faèces, nombre de larve dans l’herbe, nombre de nematodes chez des veaux de contr?le mobiles et non mobiles, determination des paramètres hématologiques et des tereurs en pepsinogène), des gains de poids et des caractéristiques cliniques des animaux. Le nombre d’oeufs dans les faeces furent réduits de 100% dans le groupe (T-2) (P < 0,001) après le traitement et perdura de fa?on significative (P < 0,05) en dessous des valeurs pour les veaux du groupe (T-1) et cela jusqu’à la fin de l’éxpérience. L’utilisation du Morantel par voie orale entra?na une réduction de 92% dans le nombre des nématodes intestinaux dans les veaux immobilisés à la fin de l’experimentation ainsi qu’une réduction de 55 à 85,7% des larves dans les herbages témoin d’une diminution des parasites rejetés par les animaux sentinels. A la fin de l’expérimentation, les veaux du groupe de contr?le gagnèrent en moyenne 59,4 kg ± 4,8 kg (200,0 ± 7,4 g/jour) alors que les animaux traités gagnèrent en moyenne 128,6 ± 10,5 kg (530,0 ± 13,1 g/jour).