Gastrointestinal Nematodes Of Cattle Research Articles

Efficacy of ivermectin against gastrointestinal nematodes of cattle in Denmark evaluated by different methods for analysis of faecal egg count reduction

The efficacy of ivermectin (IVM) against gastrointestinal nematodes in Danish cattle was assessed by faecal egg count reduction test (FECRT). Six cattle farms with history of clinical parasitism and avermectin use were included. On the day of treatment (Day 0), 20 naturally infected calves per farm (total n = 120) were stratified by initial faecal egg counts (FEC) and randomly allocated to a treatment group dosed with 0.2 mg IVM kg−1 body weight s.c. (IVM; n = 10) or an untreated control group (CTL; n = 10). Individual FEC were obtained at Day 0 and Day 14 post-treatment and pooled faeces by group were cultured to isolate L3 for detection of Ostertagia ostertagi and Cooperia oncophora by qPCR. Treatment efficacies were analysed using the recommended WAAVP method and two open-source statistical procedures based on Bayesian modelling: ‘eggCounts’ and ‘Bayescount’. A simulation study evaluated the performance of the different procedures to correctly identify FEC reduction percentages of simulated bovine FEC data representing the observed real data. In the FECRT, reduced IVM efficacy was detected in three farms by all procedures using data from treated animals only, and in one farm according to the procedures including data from treated and untreated cattle. Post-treatment, O. ostertagi and C. oncophora L3 were detected by qPCR in faeces of treated animals from one and three herds with declared reduced IVM efficacy, respectively. Based on the simulation study, all methods showed a reduced performance when FEC aggregation increased post-treatment and suggested that a treatment group of 10 animals is insufficient for the FECRT in cattle. This is the first report of reduced anthelmintic efficacy in Danish cattle and warrants the implementation of larger surveys. Advantages and caveats regarding the use of Bayesian modelling and the relevance of including untreated cattle in the FECRT are discussed.

Host protective ASP-based vaccine against the parasitic nematode Ostertagia ostertagi triggers NK cell activation and mixed IgG1-IgG2 response.

The mucus-dwelling parasite Ostertagia ostertagi is one of the most important gastrointestinal nematodes in cattle. Our group has previously demonstrated the protective capacity of a vaccine against this parasite based on a native activation-associated secreted protein ASP1 (nASP) in combination with the saponin adjuvant QuilA. The aim of the current study was to analyse the effect of both antigen and adjuvant on the cellular and humoral vaccine-induced immune responses by comparing the native ASP to a recombinant version expressed in Pichia pastoris (pASP) and replacing QuilA by Al(OH)3. Immunization of cattle with the protective nASP+QuilA vaccine was associated with antigen-induced proliferation of natural killer (NK) cells combined with IFN-γ secretion and the induction of a mixed IgG1/IgG2 antibody response. ASP-specific activation and proliferation of NK cells was also observed in mice following the same vaccination regime. Replacing QuilA by Al(OH)3 or nASP by pASP significantly decreased the capacity of the vaccines to trigger both NK cell activation and antibody responses and failed to induce protection against a challenge infection. Reduction of the structurally anchoring disulphide bonds of the nASP completely abolished its ability to induce NK cell activation and antibody responses, highlighting the importance of protein conformation for the immunostimulatory activity.

Anthelmintic effects of forage chicory (Cichorium intybus) against gastrointestinal nematode parasites in experimentally infected cattle.

Two experiments studied the effects of dietary chicory against gastrointestinal nematodes in cattle. In Experiment (Exp.) 1, stabled calves were fed chicory silage (CHI1; n = 9) or ryegrass/clover hay (CTL1; n = 6) with balanced protein/energy intakes between groups. After 16 days, all calves received 10 000 Ostertagia ostertagi and 66 000 Cooperia oncophora third-stage larvae (L3) [day (D) 0 post-infection (p.i.)]. In Exp. 2, calves were assigned to pure chicory (CHI2; n=10) or ryegrass/clover (CTL2; n = 10) pastures. After 7 days, animals received 20 000 O. ostertagi L3/calf (D0 p.i.) and were moved regularly preventing pasture-borne infections. Due to poor regrowth of the chicory pasture, CHI2 was supplemented with chicory silage. At D40 p.i. (Exp. 1) and D35 p.i. (Exp. 2) calves were slaughtered for worm recovery. In Exp.1, fecal egg counts (FEC) were similar between groups. However, O. ostertagi counts were significantly reduced in CHI1 by 60% (geometric mean; P < 0·01), whereas C. oncophora burdens were unaffected (P = 0·12). In Exp. 2, FEC were markedly lowered in CHI2 from D22 p.i onwards (P < 0·01). Ostertagia ostertagi adult burdens were significantly reduced in CHI2 by 66% (P < 0·001). Sesquiterpene lactones were identified only in chicory (fresh/silage). Chicory shows promise as an anti-Ostertagia feed for cattle and further studies should investigate its on-farm use.

Predatory Capacity in vitro of Native Nematophagous Fungi from Cundinamarca on Gastrointestinal Nematodes of Cattle

Predatory Capacity in vitro of Native Nematophagous Fungi from Cundinamarca on Gastrointestinal Nematodes of Cattle

Anthelmintic resistance to ivermectin and moxidectin in gastrointestinal nematodes of cattle in Europe

Anthelmintic resistance has been increasingly reported in cattle worldwide over the last decade, although reports from Europe are more limited. The objective of the present study was to evaluate the efficacy of injectable formulations of ivermectin and moxidectin at 0.2 mg per kg bodyweight against naturally acquired gastro-intestinal nematodes in cattle. A total of 753 animals on 40 farms were enrolled in Germany (12 farms), the UK (10 farms), Italy (10 farms), and France (8 farms). Animals were selected based on pre-treatment faecal egg counts and were allocated to one of the two treatment groups. Each treatment group consisted of between 7 and 10 animals. A post-treatment faecal egg count was performed 14 days (±2 days) after treatment. The observed percentage reduction was calculated for each treatment group based on the arithmetic mean faecal egg count before and after treatment. The resistance status was evaluated based on the reduction in arithmetic mean faecal egg count and both the lower and upper 95% confidence limits. A decreased efficacy was observed in half or more of the farms in Germany, France and the UK. For moxidectin, resistance was confirmed on 3 farms in France, and on 1 farm in Germany and the UK. For ivermectin, resistance was confirmed on 3 farms in the UK, and on 1 farm in Germany and France. The remaining farms with decreased efficacy were classified as having an inconclusive resistance status based on the available data. After treatment Cooperia spp. larvae were most frequently identified, though Ostertagia ostertagi was also found, in particular within the UK and Germany. The present study reports lower than expected efficacy for ivermectin and moxidectin (based on the reduction in egg excretion after treatment) on European cattle farms, with confirmed anthelmintic resistance on 12.5% of the farms.

Multispecies resistance of cattle gastrointestinal nematodes to long-acting avermectin formulations in Mato Grosso do Sul

The use of long-acting avermectins (AVMs) in cattle to treat infections with gastrointestinal nematodes was common in Brazil until its prohibition by state authorities. The prohibition; however, was rescinded in 2015, but a scientific discussion of the pros and cons of the use of these formulations is necessary. We evaluated the levels of resistance to 1.0 and 3.5% doramectin and to 3.15% ivermectin in cattle. The worms in animals treated with 3.5% doramectin were characterized by the suppression of oviposition and by a higher proportion of adult females carrying no eggs. Haemonchus placei, Cooperia punctata, C. pectinata, C. spatulata, and Oesophagostomum radiatum were resistant to the above compositions. The administration of long-acting AVM formulations did not result in a higher efficacy against these helminth populations.

Analysis of putative inhibitors of anthelmintic resistance mechanisms in cattle gastrointestinal nematodes

Effects of the cytochrome P450 inhibitor piperonyl butoxide and the P-glycoprotein inhibitor verapamil on the efficacy of ivermectin and thiabendazole were studied in vitro in susceptible and resistant isolates of the cattle parasitic nematodes Cooperia oncophora and Ostertagia ostertagi. The effects of combined use of drug and piperonyl butoxide/verapamil, respectively, were investigated in the Egg Hatch Assay, the Larval Development Assay and the Larval Migration Inhibition Assay. The effects of piperonyl butoxide and verapamil as inhibitors of thiabendazole and ivermectin responses were particularly marked for larval development, where both inhibitors were able to completely eliminate all differences between susceptible and resistant isolates. Even the lowest concentrations of anthelmintics used in combination with inhibitors caused complete inhibition of development. Differences and/or similarities among responses in different isolates were only obtained in the two other assays: in the Egg Hatch Assay piperonyl butoxide caused a shift in concentration–response curves obtained with thiabendazole to the left for all isolates tested, changing relative differences between isolates. In contrast, an effect of verapamil in the Egg Hatch Assay was only apparent for benzimidazole-resistant isolates. In the Larval Migration Inhibition Assay only ivermectin was tested and piperonyl butoxide shifted the concentration–response curves for all isolates to the left, again eliminating differences in EC50 values between susceptible and resistant isolates. This was not the case using verapamil as an inhibitor, where curves for both susceptible and benzimidazole-resistant isolates shifted to the left in Ostertagia isolates. In Cooperia the picture was more complex with ivermectin-resistant isolates showing a larger shift than the susceptible isolate. Single nucleotide polymorphisms in the β-tubulin isotype 1 gene were investigated. Significantly increased frequencies of resistance-associated alleles were observed for the codons 167 and 200 in one benzimidazole-resistant isolate but not in an isolate selected for benzimidazole resistance at an early stage of selection.

Risk factors for anthelmintic resistance development in cattle gastrointestinal nematodes in Argentina.

Risk factors for anthelmintic resistance (AR) on bovine ranches were studied. Data were derived from a survey made to 50 ranch owners, who had conducted a faecal egg-count-reduction test. The questionnaire contained descriptors of bovine ranch management and nematode control. A case-control design study was undertaken and AR cases were present in 26 herds. Associations between the binary outcome variable (AR versus not AR) and risk factors recorded in the questionnaire were evaluated. Variables associated with the presence of AR at P< 0.15 and/or odds ratio (OR) > 2 were subjected to a multivariable logistic regression model. The main effects contributing to general AR (avermectin AVM and/or benzimidazole) in the final model were total number of annual treatments (OR 7.68; 95% CI 2.4 to 28.3) and use of more than 75% of AVM in the past (OR= 18.6; 95% CI 1.3 to 97.3), whereas for AVM resistance alone were total number of AVM annual treatments (OR= 11.5; 95% CI 2.9 to 45.5) and number of AVM Nov-Jan treatments (OR= 5.8; 95% CI 1.71 to 47.9). The results showed that treatment frequency, date of treatment and frequency of treatment in the past with a single drug were the main risk factors involved in AR development.

POTENCIAL OVICIDA DE Origanum vulgare (Lamiaceae) EM NEMATÓDEOS GASTRINTESTINAIS DE BOVINOS

Due to anthelmintic resistance in nematodes, several research studies have been developed seeking control alternatives to these parasites. This study evaluated the in vitro action of Origanum vulgare on gastrointestinal nematode eggs of cattle. In order to evaluate the ability to inhibit egg hatch, different dried leaves extracts of this plant were tested, such as dye, hydroalcoholic and aqueous extracts at concentrations varying from 0.62 to 80 mg/mL. Each assay was accompanied by control containing levamisole hydrochloride (0.2 mg/mL), distilled water and 70o GL grain alcohol at the same concentration of the extracts. Test results showed that the different O. vulgare extracts inhibited egg hatch of cattle gastrointestinal nematodes at a percentage that varied from 8.8 to 100%; dye and hydroalcoholic extract were the most promising inhibitors. In view of this ovicidal property, O. vulgare may be an important source of viable antiparasitic compounds for nematodiosis control in ruminants. KEYWORDS: Haemonchus spp.; in vitro; oregano; phytotherapic.

Efficacy of oral, injectable and pour-on formulations of moxidectin against gastrointestinal nematodes in cattle in New Zealand

The efficacy of moxidectin administered by different routes, against naturally acquired infections of gastrointestinal nematode parasites of cattle, was compared using faecal egg count reduction tests on 14 commercial farms throughout New Zealand. On each farm, groups of 15 calves were sampled for faecal nematode egg count and then treated with ivermectin administered orally, or with moxidectin administered either by the oral, subcutaneous injection or topical (pour-on) route. Samples were again collected 14 days after treatment and efficacy was calculated as the percentage reduction in-group mean egg count between the pre- and post-treatment samples. In addition, efficacy was calculated for individual animals, in order to compare the variability of the different treatments. On four farms untreated control groups were run and five animals from each of the control and all of the moxidectin-treated groups were bled over time to estimate plasma–moxidectin concentrations.Averaged across all tests, the reduction in faecal egg count was significantly greater after treatment with moxidectin oral (91.1%) than following treatment with moxidectin injection (55.5%) or with moxidectin pour-on (51.3%). Low efficacies were invariably against Cooperia oncophora. The oral treatments were significantly less variable in efficacy than the injection and pour-on treatments. Moxidectin concentrations in plasma were highest following subcutaneous injection and lowest following pour-on administration. Plasma levels following oral administration were intermediate, being significantly lower than post-injection and significantly higher than post-pour-on. There was no evidence of transfer of moxidectin to untreated animals through licking. Based on these results, along with those of other studies, it is proposed that oral administration of macrocyclic lactone anthelmintics results in higher concentrations of active reaching the target worms in the gastrointestinal tract than following either administration by injection or by pour-on.

Assessing resistance against macrocyclic lactones in gastro-intestinal nematodes in cattle using the faecal egg count reduction test and the controlled efficacy test

The main objective of the present study was to evaluate the accuracy of the faecal egg count reduction test (FECRT) to assess the resistance status of ivermectin (IVM)-resistant isolates of the cattle nematodes Ostertagia ostertagi and Cooperia oncophora, using the controlled efficacy test (worm counts) as a reference. The second objective was to investigate whether both IVM-resistant isolates showed side-resistance against moxidectin (MOX) under controlled conditions.Thirty male Holstein calves were experimentally infected with 25,000 L3 of an IVM-resistant O. ostertagi isolate and 25,000 L3 of an IVM-resistant C. oncophora isolate. Twenty-eight days later the calves were randomly divided into 2 treatment groups and 1 untreated control group. Animals in groups 1 and 2 received MOX (Cydectin® 1%, Pfizer) and IVM (Ivomec® 1%, Merial) respectively, by subcutaneous injection at a dose rate of 0.2mg/kg bodyweight. Faecal samples were collected 7 and 14days after treatment and animals were necropsied 14/15days post-treatment.Both the FECRT and the controlled efficacy test demonstrated that the O. ostertagi and C. oncophora isolates were resistant against IVM, with efficacies below 90%. The IVM-resistant O. ostertagia isolate was still susceptible to MOX treatment, as shown by over 99% reduction in egg counts and worm burden. The FECRT suggested borderline resistance against MOX in the IVM-resistant C. oncophora isolate, with egg count reductions between 97% (95% CI: 76; 100) at day 7 and 86% (95% CI: 49; 96) at day 14. However, the controlled efficacy test clearly showed MOX-resistance, with a decrease of only 31% (95% CI: −12; 57) in C. oncophora worm numbers. After MOX treatment, a significantly lower number of eggs per female C. oncophora worms was counted compared to the control group (43% reduction). Due to this reduced fecundity, the FECRT may fail to detect MOX-resistance.

Observations on the free-living stages of cattle gastrointestinal nematodes

A 4-year study on the free-living stages of cattle gastrointestinal nematodes was conducted to determine (a) the development time from egg to infective larvae (L3) inside the faecal pats, (b) the pasture infectivity levels over time, and (c) the survival of L3 on pasture. Naturally infected calves were allowed to contaminate 16 plots on monthly basis. Weekly monitoring of eggs per gram of faeces (epg) values and faecal cultures from these animals provided data for the contamination patterns and the relative nematode population composition. At the same time, faecal pats were shaped and deposited monthly onto herbage and sampled weekly to determine the development time from egg to L3.Herbage samples were collected fortnightly over a 16-month period after deposition to evaluate the pasture larval infectivity and survival of L3 over time. The development time from egg to L3 was 1–2 weeks in summer, 3–5 weeks in autumn, 4–6 weeks in winter, and 1–4 weeks in spring. The levels of contamination and pasture infectivity showed a clear seasonality during autumn–winter and spring, whilst a high mortality of larvae on pasture occurred in summer. Ostertagia spp., Cooperia spp. and Trichostrongylus spp. were predominant and a survival of L3 on pasture over a 1-year period was recorded in this study.

Assessment of ivermectin efficacy against gastrointestinal nematodes in cattle on four Scottish farms

CURRENT control strategies targeted against gastrointestinal nematode infections in cattle rely heavily on the use of anthelmintics. Three drug classes are licensed for this purpose in the UK: benzimidazoles, imidazothiazoles...

Characterization of the abomasal transcriptome for mechanisms of resistance to gastrointestinal nematodes in cattle

The response of the abomasal transcriptome to gastrointestinal parasites was evaluated in parasite-susceptible and parasite-resistant Angus cattle using RNA-seq at a depth of 23.7 million sequences per sample. These cattle displayed distinctly separate resistance phenotypes as assessed by fecal egg counts. Approximately 65.3% of the 23 632 bovine genes were expressed in the fundic abomasum. Of these, 13 758 genes were expressed in all samples tested and likely represent core components of the bovine abomasal transcriptome. The gene (BT14427) with the most abundant transcript, accounting for 10.4% of sequences in the transcriptome, is located on chromosome 29 and has unknown functions. Additionally, PIGR (1.6%), Complement C3 (0.7%), and Immunoglobulin J chain (0.5%) were among the most abundant transcripts in the transcriptome. Among the 203 genes impacted, 64 were significantly over-expressed in resistant animals at a stringent cutoff (FDR < 5%). Among the 94 224 splice junctions identified, 133 were uniquely present: 90 were observed only in resistant animals, and 43 were present only in susceptible animals. Gene Ontology (GO) enrichment of the genes under study uncovered an association with lipid metabolism, which was confirmed by an independent pathway analysis. Several pathways, such as FXR/RXR activation, LXR/RXR activation, LPS/IL-1 mediated inhibition of RXR function, and arachidonic acid metabolism, were impacted in resistant animals, which are potentially involved in the development of parasite resistance in cattle. Our results provide insights into the development of host immunity to gastrointestinal nematode infection and will facilitate understanding of mechanism underlying host resistance.

Evaluation of reduction in egg shedding of gastrointestinal nematodes in cattle following administration of anthelmintics

To evaluate the necessary time and to identify the differences among anthelmintics for the reduction of parasite eggs shed in feces, five groups of cattle were treated with moxidectin, ivermectin, levamisole phosphate, and albendazole sulphoxide. Levamisole promoted a reduction in egg count per gram (EPG-R) of 97.4% after 24 hours, moxidectin 98.3% after 36 hours, and albendazole sulphoxide 95.9% after 36 hours post- treatment. Cooperia spp. and Haemonchus spp. showed resistance to ivermectin. The results demonstrated that the diagnosis of parasite resistance in cattle can be based on a count of eggs per gram (EPG) carried out as soon as seven days after the treatment.

Adaptation and evaluation of three different in vitro tests for the detection of resistance to anthelmintics in gastro intestinal nematodes of cattle

Three different in vitro methods, the Larval Development Test (LDT), the Larval Migration Inhibition Test (LMIT) and the Micromotility Meter Test (MMT) have been adapted to detect anthelmintic resistance in cattle nematodes. Nematode eggs and third stage larvae of different Ostertagia ostertagi and Cooperia oncophora isolates were obtained from faecal cultures of experimentally infected calves. Additionally, adult C. oncophora were evaluated in the MMT for the detection of resistance to ivermectin (IVM). For all three in vitro tests standard operating procedures (SOPs) were established and successfully used for the detection of responses of non-parasitic and parasitic stages to different anthelmintic substances and the description of dose–response curves. In the LDT ivermectin (IVM) and thiabendazole (TBZ) were tested, in the LMIT IVM and levamisole (LEV) and in the MMT only IVM was evaluated. Susceptible isolates of C. oncophora and O. ostertagi, an IVM-resistant isolate of C. oncophora and a TBZ-selected isolate of O. ostertagi were used in all ( C. oncophora) or only some of these tests ( O. ostertagi). For all isolates sigmoidal dose–response curves and EC 50 values for the tested substances were obtained using a four-parameter logistic model. For the LDT, the previously reported problem in development of larvae was successfully overcome with mean development rates between 80% and 87% in negative controls. Following optimization of incubation times, temperatures, mesh sizes (LMIT only), nutritive medium (LDT only) and group size (MMT only) all three test systems reliably detected significant differences in the response to IVM between the susceptible and IVM-resistant isolate of C. oncophora ( p < 0.0001), resulting in an resistance ratio (RR) value of approximately 5 for IVM and 2.8 for LEV in C. oncophora. The LDT also detected differences in the response to TBZ between the susceptible and BZ-selected O. ostertagi isolates ( p < 0.001) with an RR of 2 for TBZ. With the standardization of the described tests we report reproducible and reliable in vitro methods for the detection of resistance to IVM (LDT, LMIT and MMT) and TBZ (LDT) for cattle parasitic nematodes.

The Socio-Demographic Characteristics of Population Ages 65 and Above Living in Burdur Province

The present study was conducted to detect the status of anthelmintic resistance for fenbendazole against gastrointestinal nematodes in cattle under field conditions. For this, 10 cattle from village Bhimewala, district Fatehabad and 12 cattle from village Talwandi Rana, district Hisar were selected having eggs per gram (EPG) of faeces > 150. The cattle from each district were divided into two group of equal number i.e. T1, T2 of Fatehabad and T3, T4 of Hisar. Animals of T1 and T3 were administered with fenbendazole @ 5 mg/kg b. wt, orally while T2 and T4 served as untreated control. Faecal samples were collected on 12th day after treatment from animals of all groups and individual faecal egg counts were determined by modified McMaster technique. Faecal egg count reduction percentage in groups T1 and T3 were 100 and 100%, respectively. Identification of infective larvae from pre-treatment faecal cultures revealed the predominance of Haemonchus spp. larvae followed by Trichostrongylus spp. and Strongyloides spp. No larvae were recovered from post treatment feacal culture of treated groups. The study indicates no resistance of fenbendazole to Haemonchus spp. in cattle of these villages of Haryana.

Monitoring the efficacy of ivermectin and albendazole against gastro intestinal nematodes of cattle in Northern Europe

Faecal egg count reduction tests (FECRT) using ivermectin (IVM) and benzimidazole (BZ) were conducted to investigate the prevalence of anthelmintic resistance in gastro-intestinal nematodes on cattle farms in Germany, Belgium and Sweden in 2006 and 2007. Based on sufficient numbers of eggs prior to the study, between 3 and 10 farms per country were selected. 10–15 animals were randomly selected per farm and subcutaneously treated with 0.2 mg IVM/kg bodyweight (Ivomec ®, Merial). Faecal samples were collected individually from every animal on day 0 (treatment), day 7 (Belgium & Sweden) or 14 (Germany), and day 21 (Germany, Belgium and Sweden). Faecal egg counts (FEC) were performed at each sampling occasion to estimate the eggs per gram of faeces (EPG) and the reduction of eggs after treatment. The FECRT using IVM in 2006 revealed mean reduction of egg counts between 69–100% on day 7/14 (95% confidence interval (CI) 19–102) and 35–96% (95% CI 0–102) on day 21. Farms with a suggested problem of anthelmintic resistance have been re-visited in 2007 and except for one case all results obtained in 2006 were confirmed in 2007. Larvae obtained from faecal cultures were identified using microscopic identification keys or genus-specific real time PCR. Cooperia oncophora was the predominant species detected after treatment, but Ostertagia ostertagi was found in samples on 3 farms in Germany and 3 farms in Sweden post-treatment. In 2007 additionally a FECRT using benzimidazoles was conducted in Germany and Sweden. In Germany oral Valbazen ® (albendazole, 10%, Pfizer) was used at a concentration of 7.5 mg albendazole/kg bodyweight; in Sweden Valbazen Vet ® (albendazole, 10%, Orion Pharma) at a dose of 8 mg/kg was used. For benzimidazoles an efficacy of 100% was obtained on all tested farms in both countries. This is the first report of a multinational anthelmintic efficacy investigation in cattle in Europe. The results suggest that testing of anthelmintic efficacy should be performed more intensively due to possible insufficient efficacy of current drugs.

Effects of neem (Azadirachta indica) leaves against gastrointestinal nematodes in cattle

Effects of neem (Azadirachta indica) leaves against gastrointestinal nematodes in cattle

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.