Chandra Bhushan

Anthelmintic efficacy of oral trichlorfon solution against ivermectin resistant nematode strains in cattle

Infected calves from two different rural estates in Brazil were studied to assess the anthelmintic efficacy of oral trichlorfon against naturally occurring ivermectin resistant parasitic nematode strains. In experiment I, infected animals were from a region where ivermectin resistant populations of Haemoncus placei, Cooperia punctata, Cooperia spatulata and Trichuris discolor have recently been identified. Six calves with natural gastrointestinal nematode infections were treated with 48.5mg/kg aqueous trichlorfon administered orally and six calves acted as a non-treated control group. In experiment II 24 naturally infected calves were selected to enter one of four treatment groups, six animals each received: 48.5mg/kg oral trichlorfon; 200 microg/kg subcutaneous 1% ivermectin; 630 microg/kg subcutaneous 3.15% ivermectin; or no treatment (control group). Gastrointestinal helminths were counted and identified post-mortem at 7 days (trichlorfon and 1% ivermectin treated and untreated animals) or 14 days (3.15% ivermectin treated and untreated animals) after administration of the test agents. Experiment I identified a high level efficacy for oral trichlorfon against four helminth species that have previously been shown to be ivermectin resistant in this geographical region: percentage efficacy was 99.82% against adult H. placei, 99.18% against C. punctata, 99.33% against C. spatulata, 81.06% against T. axei, 98.46% against Oesophagostomum radiatum and 100% against T. discolor. Trichlorfon also showed activity against the ivermectin (1% and 3.15%) resistant helminth species identified in experiment II, attaining efficacy levels of 99.17% against H. placei, 98.46% against C. punctata and 100.00% against T. discolor. These findings indicate that oral trichlorfon is an effective treatment option in the management of cattle infected with ivermectin resistant helminths.

Treatment of experimentally induced Theileria annulata infection in cross-bred calves with buparvaquone

Twenty cross-bred (Bos taurus X Bos indicus) calves, 7-21 days old, were infected by a ground-up tick supernate of Hyalomma anatolicum anatolicum infected with the Hisar isolate of Theileria annulata. Six calves acted as untreated controls and they all died of theileriosis within 17 days of infection. The remaining 14 calves were divided into Group A and B, each consisting of seven calves. All the calves of Groups A and B were treated intramuscularly with buparvaquone (BW 720C) on Day 11 post-infection, when clinical signs of theileriosis were apparent. Each calf received 2.5 mg BW 720 C kg-1 body weight as a single injection. In addition, each calf of Group B was given proprietary haematinics by intramuscular injection, daily for 12 days. In Group A, two calves died of cerebral theileriosis and five were clinically cured. However, four of these five calves later died of anaemia. In Group B, all the calves were clinically cured and none died during the observation period of 1 month. The parasitaemia declined to less than 1% within a fortnight of treatment. The initial declines in haemoglobin concentration and packed cell volume were halted and preinfection values were soon restored. No toxic signs attributable to treatment with buparvaquone were observed.

Strategies for the control of Rhipicephalus microplus ticks in a world of conventional acaricide and macrocyclic lactone resistance

Infestations with the cattle tick, Rhipicephalus microplus, constitute the most important ectoparasite problem for cattle production in tropical and subtropical regions worldwide, resulting in major economic losses. The control of R. microplus is mostly based on the use of conventional acaricides and macrocyclic lactones. However, the intensive use of such compounds has resulted in tick populations that exhibit resistance to all major acaricide chemical classes. Consequently, there is a need for the development of alternative approaches, possibly including the use of animal husbandry practices, synergized pesticides, rotation of acaricides, pesticide mixture formulations, manual removal of ticks, selection for host resistance, nutritional management, release of sterile male hybrids, environmental management, plant species that are unfavourable to ticks, pasture management, plant extracts, essential oils and vaccination. Integrated tick management consists of the systematic combination of at least two control technologies aiming to reduce selection pressure in favour of acaricide-resistant individuals, while maintaining adequate levels of animal production. The purpose of this paper is to present a current review on conventional acaricide and macrocyclic lactone resistance for better understanding and control of resistant ticks with particular emphasis on R. microplus on cattle.

Comparison of Three Different Treatment Schedules for Praziquantel (Cestocur ® , Bayer) in the Treatment of Tapeworm Infections (Moniezia spp.) and Their Impact on Body Weight Gains in a German Sheep Flock

In an observational study, three different treatment schedules with praziquantel were assessed in a Merino land sheep flock from southern Germany. The herd had a known history of severe recurrent Moniezia spp. infections. After turnout to pasture, three hundred lambs between 8 and 14 weeks old were weighed and randomly allocated to three different groups. They were treated with praziquantel (Cestocur®) at a dose of 3.75 mg/kg body weight using the following schedules: group 1 treated four times at monthly intervals (Days 1, 31, 59, 91); group 2 treated three times at six-week intervals (Days 16, 59, 105), group 3 treated twice at an eight-week interval (Days 31, 91). Based on faecal examinations, all lambs were negative for Moniezia spp. on Day 1. At study end (Day 126), higher body weights were seen in group 1 (49.9 ± 5.8 kg; 49.9 kg) than in group 2 (48.7 ± 5.5 kg; 49.0 kg) and in group 3 (47.5 ± 5.4 kg; 47.5 kg) (mean ± SD; median). Overall weight gains were significantly higher in group 1 (22.5 ± 1.8 kg; 22.3 kg) compared to group 2 (20.8 ± 1.4 kg, 21.0 kg; p < 0.0001) and group 3 (19.3 ± 2.2 kg, 19.6 kg; p < 0.0001). The results show that praziquantel treatments applied early in the grazing season and in monthly intervals were more beneficial for body weight developments in lambs than applied at six-weekly or eight-weekly intervals.

Prevention of coccidiosis in dairy cows

WE read with interest the paper entitled ‘Efficacy of diclazuril and toltrazuril in the prevention of coccidiosis in dairy cows under field conditions’ by Zechner and others published online in Veterinary Record on November 7, 2014, and further summarised in Veterinary Record of January 31, 2015 (Zechner and others 2015). We wish to draw attention to the paucity of information in both the study design and method, together with inconsistencies in the data and its interpretation. The study was designed so that calves were treated after being moved to the housing commonly …

Evaluation of 40 % Diazinon Impregnated Ear Tag (Patriot™) for Controlling Horn Flies and Face Flies among Cow-Calf Pairs in the United States

Horn flies (Haematobia irritans irritans) and face flies (Musca autumnalis) are common insects in grazing animals in most of the world. The current study was designed to evaluate the efficacy of 40 % diazinon impregnated eartags (PatriotTM) in reducing horn fly and face fly pressure in cow calf pairs in Missouri, USA. Seventy cow calf pairs were randomly assigned to one of two treatment groups i.e. Patriot Group and Placebo Group. On study day 0, cows in Patriot treatment group were tagged with two insecticide impregnated ear tags (Patriot Ear Tags), while the calves were administered one tag. Placebo group animals were administered placebo ear tags in a similar manner as Patriot treatment groups. Fly counts were performed on ten randomly identified cows within each group throughout the study. Beginning on Day -10, fly counts were performed three times (day -7, -3 and 0) to ensure that fly pressure was sufficient prior to Day 0. Post-treatment fly counts were performed weekly on the same 10 cows within each group. The mean horn fly counts per animal in Patriot group were below economic threshold during first 13 week of study period and were slightly above, 215.5 in week 14 and 209.6 in week 15. The highest percent face fly efficacy was observed in study week 5 which was 72.93. The results indicate that 40 % diazinon impregnated (Patriot Ear Tags) were highly effective in mitigating horn fly and face fly pressure for up to 15 weeks. WAAVP_2017.indb 123 29.06.17 15:35 S124 EctoparasitEs EctoparasitEs

Field Evaluation of the Effectiveness of an Oral Toltrazuril and Iron Combination (Baycox® Iron) in Maintaining Weaning Weight by Preventing Coccidiosis and Anaemia in Neonatal Piglets

Effectiveness of an oral combination of toltrazuril and iron dextran (Baycox® Iron) to maintain weaning weight by preventing coccidiosis caused by Isospora suis and iron-deficiency anaemia in neonatal piglets was investigated on three commercial pig farms with a history of coccidiosis: two in Mexico and one in Brazil. On day (SD) 2 of life, piglets were randomised within litter by bodyweight to treatment or control group. On SD 3 piglets allocated to the control group (CG) each received 1 mL Baycox®, containing 50 mg/mL toltrazuril orally and commercially available iron (200 mg/piglet) by intramuscular injection. Piglets allocated to the treatment group (TG) each received 1 mL toltrazuril and iron combination orally (Baycox® Iron) containing 50 mg/mL toltrazuril and 228 mg iron as iron dextran. All piglets had access to creep feed. 6493 piglets completed the study. Bodyweight at weaning on SD 21 of piglets treated with the oral toltrazuril and iron combination was confirmed to be non-inferior to the control treatment with <1 % difference between group mean body weights. Faecal samples from at least 10 % of litters on SD 14 demonstrated control of coccidiosis. Haemoglobin levels on SD 21 were lower in the oral toltrazuril and iron combination treated piglets compared to control levels but above minimum haemoglobin levels to maintain health. There was no difference in mortality between the two groups. This large scale field evaluation clearly demonstrated the effectiveness of a combination of oral toltrazuril and iron (Baycox® Iron) in maintaining body weight at weaning compared to conventional treatment. The combination was effective in preventing coccidiosis and anaemia and thus provides a valuable alternative that reduces stressful events in neonatal piglets. There were no product related adverse events.

The Effects of a Pour-on Formulation of Fluazuron 2.5 % and Flumethrin 1 % on Populations of Rhipicephalus decoloratus and Rhipicephalus microplus Both on and off Bovine (Bonsmara Breed) Hosts

The present study demonstrated the efficacy of a pour-on formulation of fluazuron 2.5 % and flumethrin 1 % (Drastic Deadline eXtreme®) against Rhipicephalus decoloratus and Rhipicephalus microplus on cattle on pasture previously grazed by experimentally infested animals. Six tick-free cattle were placed on the pasture and treated 7 days later (Day 0) with the pour-on. They were retreated on Days 63, 126 and 189 and monthly tick counts were done. Mean numbers of adult R. decoloratus and/or R. microplus decreased from 53 and 14 on Days 56 and 112 respectively to 2 or less on all other occasions including Day 254. Compared to the numbers of R. decoloratus and/or R. microplus larvae collected from vegetation in the previous year, larval numbers declined by 40.7 % on Day 28, and thereafter reduction remained between 84 % and 100 %. Pairs of tracer calves placed on the pasture for 7 days each month were then held in pens and adult ticks that detached collected. Reduction in the numbers of R. decoloratus collected from tracer animals was 75 % on Day 56 and remained above 93 % except for Day 224 when it temporarily decreased to 78.5 %. Reduction in the numbers of R. microplus was 97.5 % on Day 28 and remained above 98 % until the conclusion of the study on Day 254. Treatment with the pour-on formulation of fluazuron and flumethrin resulted in a marked decrease in the numbers of R. decoloratus and/or R. microplus on treated cattle followed by a reduction in the numbers of larvae questing on the vegetation and ticks picked up by tracer calves. No other potential host species for R. decoloratus and/or R. microplus were present in the camps.

Immunization of neonatal bovines against Theileria annulata by an infection and treatment method.

Sixty three cross-bred (Bos taurus X Bos indicus) 4-5-day-old calves were divided into 16 groups (A-P). Each calf in Groups A and B was given ground-up-tick supernate prepared from Theileria annulata-infected or non-infected Hyalomma anatolicum anatolicum (GUTS) equivalent to 5 ticks (50 infected acini). Groups D and E received infected GUTS equivalent to 2 ticks (20 infected acini) and Groups G and H were given infected GUTS equivalent to 1 tick (10 infected acini). Each calf in Groups J, K and L received infected GUTS equivalent to 5 infected acini (0.035 tick), and Group O was inoculated with non-infected GUTS equivalent to 5 ticks. Each calf in Groups A, D, G, J, K and O was also given a single intramuscular injection of long acting oxytetracycline, 20 mg kg-1 body weight just after inoculation of GUTS. Severe reactions resulted in the death of five of eight, three of eight, five of six, one of five and one of five calves in Groups A, D, G, J and K respectively and all of the calves in Groups B, E, H, and L. The surviving calves of Groups A, D, G, J, K and O were challenged on Day 45 post-immunization along with freshly introduced susceptible control calves of Groups C, F, I, M, N and P. All the calves of Groups A, G, J and K withstood the challenge dose; in Group D four of five and in Groups C, F, I, M, N, O, and P all the calves died of theileriosis. It is concluded that though the infection and treatment method of immunization may be used for neonatal bovines, the dose of immunogen should be based on actual counts of infected salivary acini of ticks instead of the number of ticks.