Trichostrongylus colubriformis and Ostertagia circumcincta resistant to levamisole, morantel tartrate and thiabendazole: occurrence of field strains

Field strains of Trichostrongylus colubriformis and Ostertagia circumcincta, designated PF4 and PF5 respectively, were recovered from a farm on which the sole use of levamisole over a preceding 12 year period led to the development of anthelmintic resistance. The results of field observations and preliminary critical trials in both Merino and crossbred sheep showed that both species have varying degrees of resistance to three major anthelmintics; levamisole, morantel tartrate and thiabendazole. Mean worm count reductions for adult T colubriformis (PF4) for therapeutic doses of morantel tartrate, thiabendazole and levamisole in crossbreds were 45.7 per cent, 97.3 per cent and zero respectively, and for Merinos 80.7 per cent, 88.3 per cent and 92.0 per cent respectively. Against O circumcincta the corresponding reductions for crossbreds were 51.4 percent, 95.4 per cent and 20.3 per cent and for Merinos, 52.5 per cent, 73.1 per cent and 29.8 per cent. There was no statistically significant difference in the responses of both parasite species to either levamisole or morantel. This result suggests that resistance to the two chemically unrelated drugs may be co-inherited.     

The efficiency of levamisole, thiabendazole and fenbendazole against naturally acquired infections of Ostertagia ostertagi in cattle

In two experiments, conducted in cattle with naturally acquired infections of Ostertagia ostertagi, comparative assessments were made of the anthelmintic efficiency of levamisole, thiabendazole and fenbendazole, each at 1.0, 1.5 and 2.0 times the recommended dose rate. Variable efficiencies of 81 and 49 per cent for levamisole, 86 and 56 per cent for thiabendazole were obtained against adult O ostertagi. Neither drug showed substantial activity against early fourth stage larvae. Efficiency of fenbendazole against adult O ostertagi was consistently high; 85 and 89 per cent in the two experiments respectively. In the first experiment in which cattle were slaughtered two to three days after treatment, only 22 per cent of inhibited early fourth stage larvae were removed whereas in the second experiment when slaughter took place 10--11 days after treatment, this efficiency was 89 per cent. There was no increased effect of increased dose rates on treatments with thiabendazole or fenbendazole. The activity of levamisole against adult worms and inhibited larvae was increased at twice the recommended dose rate.     

Protection developed against reinfection by Dictyocaulus viviparus following anthelmintic treatment of a one-day-old primary infection in cattle

Single doses of 7.5 mg/kg levamisole subcutaneously and 5 mg/kg oxfendazole per os and three daily doses of diethylcarbamazine intramuscularly were 86.9, 82.1 and 46.6 per cent efficient, respectively, against one-day-old Dictyocaulus viviparus. These three dosage regimes were also associated, respectively, with 92.5, 36.4 and 56.0 per cent protection against reinfection following anthelmintic treatment. It is suggested that the high degree of protection following the use of levamisole may be a consequence of rapid and effective anthelmintic activity combined with immunomodulating effects.     

Evidence of multiple anthelmintic resistance in a strain of Teladorsagia circumcincta (Ostertagia circumcincta) isolated from goats in Scotland

The efficacy of ivermectin, fenbendazole and levamisole was determined in lambs individually infected with 5000 third stage larvae of Teladorsagia (Ostertagia) species isolated from a herd of goats with a history of benzimidazole resistance and where the efficacy of ivermectin had also suffered an apparent decline. Efficacies, calculated using geometric means, for groups where treatments were directed against adult worms were 90.3 per cent (ivermectin), 43.4 per cent (fenbendazole) and 100 per cent (levamisole). The efficacy of ivermectin against immature stages was 83.2 per cent. Ivermectin was highly effective (99.9 per cent) against a known susceptible ovine strain of Teladorsagia.     

Clinical findings in cattle with dilatation and torsion of the caecum

Dilatation and torsion of the caecum is usually an acute illness with signs of ileus and this paper presents the clinical findings from 111 heifers and cows with the condition. On admission 61 per cent of the animals had been ill for less than 24 hours; the general condition was disturbed in 58 per cent of the animals, 39 per cent showed signs of colic; the rectal temperature was abnormal in 55 per cent, the heart rate in 40 per cent and the respiration rate in 52 per cent of the animals; rumen motility was reduced or absent in 85 per cent. One or more tests for foreign bodies were positive in 58 per cent, and swinging auscultation and percussion auscultation on the right side, either alone or in combination, were positive in 83 per cent of the animals. On rectal examination it was possible to palpate a pathologically distended, displaced or twisted caecum in 95 per cent of the animals. In 87 per cent defecation was reduced or absent. The most reliable diagnostic investigations were rectal examination and swinging and percussion auscultation on the right side.     

Evaluation of oxfendazole against natural infections of gastro-intestinal nematodes and lung-worms in calves.

The anthelmintic activity of oxfendazole (Syntex) was tested in calves at dosages of 2-5 and 5-0 mg per kg. At both dose levels, oxfendazole showed 100 per cent efficacy against adult Ostertagia ostertagi, O lyrata, O cremensis, fifth stage Ostertagia spp and adult Haemonchus spp. Against adult Cooperia oncophora, efficacy was 99.8 per cent and 100 per cent at doses of 2.5 mg per kg and 5.0 mg per kg respectively while at both dose levels 100 per cent activity was recorded against C surnabada and fourth and fifth stage Cooperia spp. One hundred per cent efficacy was obtained with both dose levels against adult and fifth stage Dictyodaulus viviaprus; against Trichuris spp, percentage efficacy was 92 and 100 per cent at doses 2.5 and 5.0 mg per kg respectively. Oxfendazole showed higher efficacy than levamisole against Ostertagia spp but against the other species encountered, both anthelmintics possessed similar efficacy. Both anthelmintics significantly increased the calves' weight gains.     

Plasma nitrate/nitrite concentrations in dogs with naturally developing sepsis and non-infectious forms of the systemic inflammatory response syndrome

The aim of this prospective observational study was to evaluate the differences in plasma nitrate/nitrite concentrations between dogs with sepsis and those with non-infectious forms of the systemic inflammatory response syndrome (SIRS). Eighteen dogs with sepsis, 20 dogs with SIRS and 29 healthy control dogs were enrolled. Blood samples were obtained from the dogs within 12 hours of admission to the University of Missouri Veterinary Medical Teaching Hospital (MU VMTH) Intensive Care Unit (ICU) in lithium heparin blood tubes. Plasma nitrate/nitrite concentrations were measured using the Greiss reaction. Plasma nitrate/nitrite concentrations at presentation, clinical parameters, organ dysfunction and in-hospital mortality were compared between groups. Plasma total nitrate/nitrite was significantly greater in the sepsis group compared with the control group (P=0.005) and SIRS group (P=0.037). There was no statistical difference in plasma nitrate/nitrite concentration between the SIRS and control groups (P=0.489). The sensitivity was 66.7 per cent (95 per cent CI, 41 to 87 per cent) and the specificity was 75.5 per cent (95 per cent CI, 61 to 87 per cent) for differentiating dogs with sepsis from dogs without sepsis.     

Evaluation of a new non-hormonal substance for terminating pregnancy in bitches in clinical trials

A new non-hormonal contragestational agent (DL 717-IT), the 2-(4 chlorophenyl)-s-triazole |5,1-a|-isoquinoline, was tested in clinical trials to determine its efficacy for interrupting the pregnancy in the bitch. Five hundred and sixty-five bitches were given a single intramuscular injection of the drug between the first and 15th day after the mating. Of the 475 bitches that received 2–5 mg/kg, 430 (90-5 per cent) did not whelp at all, 15 (3-2 per cent) delivered a few stillborn or weak puppies that died some hours after birth, and 30 (6-3 per cent) delivered at least one normal live pup. Of 90 bitches treated with 3–5 mg/kg, 87 (96-7 per cent) did not whelp at all, two (2-2 per cent) delivered a few stillborn or weak puppies that died some hours after birth, and one (1 1 per cent) delivered normal live puppies. DL 717-IT, owing to the high effectiveness and minimal side effects, must be considered a very reliable drug for the interruption of pregnancies in the bitch.     

Seasonal comparisons of anthelmintic activity of levamisole pour-on in cattle in the USA

Anthelmintic activity of a pour-on formulation of levamisole, applied during warm weather (16 degrees to 36 degrees C) at 10 mg/kg bodyweight, was evaluated in groups of naturally parasitised calves. This activity was compared to that obtained in similar groups of calves treated in the winter (-4 degrees to +7 degrees C). Controlled efficacy of the pour-on formulation was determined for each season by comparing mean worm burdens in treated calves sacrificed seven to nine days after treatment to non-treated controls. In these trials, burdens of Bunostomum phlebotomum, Cooperia species, Haemonchus placei, Nematodirus species, Oesophagostomum radiatum, Ostertagia ostertagi and Trichostrongylus axei in treated calves were reduced by 83.3 to 100 per cent in the summer and 89.2 to 100 per cent in the winter. Field investigations at nine locations across the USA compared changes in faecal egg counts for cattle treated and evaluated during warm summer months (27 degrees to 36 degrees C) to those treated during cold winter months (-18 degrees to +10 degrees C). Overall, faecal egg counts were reduced by 90.2 per cent in the summer trials and 94.0 per cent in the winter trials. The results of these trials indicate that there is no seasonal variation in the anthelmintic activity of this pour-on formulation of levamisole.     

Comparison of the efficacy of dermal formulations of ivermectin and levamisole for the treatment and prevention of Dictyocaulus viviparus infection in cattle

Four groups of six parasite-naive calves were infected at seven day intervals with three doses of infective larvae of Dictyocaulus viviparus. Twenty-one days after the first dose three of the groups were treated either with an injectable formulation of ivermectin at a dose rate of 200 micrograms/kg bodyweight, or with pour-on preparations of levamisole at 10 mg/kg or ivermectin at 500 micrograms/kg. On day 28 two calves from each group were slaughtered and their burdens of lungworms counted. On day 35 the remaining calves were reinfected with D viviparus infective larvae at a rate of 80 L3/kg. The levamisole preparation was 94.6 per cent effective and both ivermectin preparations were 100 per cent effective against the initial infections. The ivermectin-treated calves were protected from the reinfection which subsequently became patent in the levamisole-treated and control calves.     

Controlled trials of the anthelmintic oxfendazole in ewes and lambs naturally infected with gastrointestinal nematodes.

Oxfendazole doses at a rate of 5 mg per kg, before or after lambing, reduced nematode egg output to insignificant levels in ewes, most of which were not exposed to re-infection. Ewes treated with oxfendazole had a significantly lower egg output than those treated with levamisole, although the latter anthelmintic was also highly effective. In lambs, oxfendazole at a dose rate of 5 mg per kg, showed 100 per cent efficacy for Ostertagia circumcincta, O trifurcata, Teledorsagia davtiani, Trichostrongylus axei, T vitrinus, T colubriformis, Nematodirus battus, N filicollis, immature Nematodirus, Chabertia ovina, and 93 per cent efficacy for Trichuris spp. Levamisole showed similar efficacies but did not remove Trichuris.     

Effect of condensed tannins extracted from four forages on the viability of the larvae of deer lungworms and gastrointestinal nematodes

The inhibitory activity of condensed tannins extracted from four forage legume plants were evaluated by using a larval migration inhibition assay. The first (L1) and third (L3) stages of deer lungworm (Dictyocaulus viviparus), and the third stage (L3) of deer gastrointestinal nematodes were incubated with tannins extracted from Lotus pedunculatus, Lotus corniculatus, sulla (Hedysarum coronarium) and sainfoin (Onobrychus viciifolia). The tannins extracted from all the forages had inhibitory activity as measured by their ability to paralyse the larvae and inhibit them from passing through sieves. At the highest concentration used (1200 microg/ml) the tannins extracted from sainfoin had the highest activity against ensheathed L1 lungworm larvae (58 per cent), followed by L. pedunculatus (45 per cent), sulla (42 per cent) and L. comiculatus (35 per cent) when the larvae were incubated at 37 degrees C. The same trend, but with lower activities, was observed when the larvae were incubated at 22 degrees C. Anthelmintic activity against L3 lungworm larvae was evaluated by measuring the death rate of ensheathed L3 larvae after incubation with condensed tannins for two, 24 and 48 hours at room temperature (22 degrees C). The death rate was significantly higher (P<0.001) after 48 hours incubation than after two hours or 24 hours, and significantly higher (P<0.001) after 24 hours than after two hours incubation. Condensed tannins from sainfoin had the highest inhibitory activity followed by L. pedunculatus, sulla and L. comiculatus. The tannins from sainfoin also had the highest activity against L3 larvae of gastrointestinal nematodes, followed by L. pedunculatus, sulla and L. comiculatus. Exsheathed larvae of gastrointestinal nematodes were significantly more susceptible to the action of the tannins than ensheathed larvae.     

Studies of the effect of synthetic oxytocin and neurohypophyseal extract on diuresis of water-laden cattle

The action of synthetic oxytocin and Glanduphen, a neurohypophyseal extract preparation, on the diuresis of six heads of cattle in lactation was studied, following intraruminal application of water. Intravenous injection of something between 10 and 30 I.U. of oxytocin reduced diuresis by 54 per cent on average, within 30 minutes from treatment. Urine-borne Cl- -concentrations went up by 315 per cent on average and quantitative Cl- -secretion by 87 per cent. The values recorded in response to the administration of doses between 10 and 40 I.U. of Glanduphen were 44, 785, and 344 per cent. Additional application of Glanduphen within 30 minutes from oxytocin injection caused less pronounced inhibition of diuresis or even some activation of diuresis. Literature on renal effects of vasopressin and of oxytocin was analysed, in that context, and the conclusion was drawn that antidiuretic effects were recordable neither from man nor from animals unless they were exposed to excessive application of water. The same hormone preparations, however, caused increase of diuresis in thirty animals with low rates of diuresis and higher osmotic urine pressure. Rise in saluresis was a most common result of vasopressin or oxytocin administration and did in no way depend on the diuresis level.     

Detection of levamisole and ivermectin in organ samples from a dead collie.]

A collie, known for its breed-dependent adverse reaction to ivermectin, was without any clinical signs. The dog was prophylactically treated with 3 mg/kg KG (s.c.) of levamisole. Within 15 minutes, the dog showed convulsions, vomitus, and dyspnea, and perished 2.5 hours after injection of the drugs. The pathological findings were not informative as to the cause of death, and with regard to the adverse reactions, additional application of ivermectin was not excluded. Therefore, organ samples were submitted for toxicological analysis of both levamisole and ivermectin. For detection of levamisole and ivermectin, modified GC/MS and HPLC procedures were developed. Concentrations up to 535 micrograms levamisole and up to 26 ng ivermectin were found per g tissue. Both analytical methods are sensitive enough to detect these drugs after application of low doses. This study elucidates that combination of low-dosed ivermectin and levamisole is no recommendable means against adverse effects of ivermectin, with respect to collies. Moreover, the synergistic effects of ivermectin and levamisole suggests the same drug incompatibility in other dog breeds and animal species.     

The Duration of Farrowing in Relation to the Reproductive Performance of Yorkshire Sows

Records for 212 attended farrowings by 38 Yorkshire sows were examined. Eighty per cent of the farrowings were less than six hours, 18 per cent between six and 12 hours and two per cent between 12 and 17 hours duration. There appeared to be no marked relationship between the duration of farrowing and the size of litter.

In spite of a higher stillbirth rate in males, there were more male (52.3 per cent) than female piglets born alive. As the time taken to farrow increased from within 1-3 hours to more than eight hours, the percentage of stillborn piglets and the percentage of litters with stillbirths increased to 10.5 from 2.4 and to 61.1 from 18.2 per cent respectively.

Twenty-nine per cent of the litters were farrowed on the 114th day of gestation. As the gestation period lengthened to 117 days or more, from 113 days or less, there were corresponding increases in the duration of farrowing and the incidence of stillbirths, and a decrease in litter size.

A need to investigate the use of hormones to control parturition in sows was suggested.

     

Forms of employment and species caseload of veterinary practitioners in New Zealand

A survey by means of a postal questionnaire was undertaken to investigate the patterns of work and the need for information of veterinary practitioners in New Zealand. Of the 670 eligible veterinarians, 399 practitioners (60 per cent) participated in the survey. Of these, 38 per cent were in large animal practice (less than 20 per cent of work devoted to cats and dogs) and 31 per cent were in small animal practice (more than 80 per cent of work with cats and dogs). The remaining 31 per cent were in mixed practice, with a workload intermediate between the other two groups. Across the entire sample of practitioners, cats and dogs took up the largest number of veterinary hours per person (1092 hours per year). Dairy cattle were second (438 hours), and horses third (302 hours). Deer and goats ranked next, and each used more veterinary hours per person than did either sheep or beef cattle. Other species comprised very minor parts of the overall workload. Women spent a much higher proportion of their working hours with small animals and a much lower proportion with horses than did men. For other species workload patterns were similar between men and women. In relation to employment of the practitioner group, women were under represented, compared with men, among those with responsibilities for the management of practices, even when account was taken of the fact that the women in the sample were younger. Fewer than one per cent of men in the sample were not employed full-time, whereas 15 per cent of the women were in part-time employment. The survey indicates that there has been a substantial change in the demographic structure of the veterinary profession and the forms of veterinary work carried out. It also shows that the differences in work and career patterns between men and women need more intensive study to improve the accuracy of predictions of future requirements for veterinary manpower.     

Immunogenicity of a Locally Produced Newcastle Disease I-2 Thermostable Vaccine in Chickens in Uganda

A locally-produced Newcastle disease (ND) I-2 thermostable vaccine of embryo-infective dose (EID50) 10(8.5) per ml was administered to 100 laboratory chickens in four test groups, each of 25 birds. It was given by the eye-drop method, in drinking water, in drinking water freshly medicated with levamisole, or using millet grains as a vaccine carrier. A fifth control group consisting of 25 birds received the heat-sensitive La Sota vaccine (EID50 10(9) per ml) by the eye-drop method. The immunological responses were monitored by the enzyme-linked immunosorbent assay (ELISA) ND antibody technique using serum samples collected from 18 birds in each group at 3-week intervals for 3 months. The overall mean ND antibody log(10) titres and percentage positivities were 3.1, 88%; 2.9, 70%; 3.0, 83%; 3.2, 87% and 3.3, 87%, respectively. The use of water alone or medicated with levamisole for vaccine administration produced significantly lower ND antibody titres only in the first 3 weeks. The immunogenicity shown by the I-2 vaccine as a potential vaccine is discussed in relation to free-range poultry management conditions in Uganda.     

Specific immunoglobulins in serum of newborn lambs fed with a single dose of colostrum containing anti-peroxidase IgG

The apparent efficiency of absorption and the decrease of specific colostral IgG after its passage into the blood stream were determined in newborn lambs fed with a single dose of colostrum containing anti-peroxidase IgG at 30 minutes, 12 hours and 24 hours after birth. When colostrum was given at 30 minutes after birth, a value of 16.9+/-4.0 per cent of anti-peroxidase IgG ingested appeared in lamb circulation. This percentage was reduced to 9.8+/-0.8 per cent when the feeding was done at 12 hours after birth and no specific IgG was detected in lambs fed at 24 hours after birth. The concentration of anti-peroxidase IgG in lambs' serum declined quickly within 96 hours of age to about 48 per cent of the initial value, and afterwards the level decreased slowly reaching a value of 10 per cent at 32 days of age. This behaviour probably reflects the protein distribution and use of absorbed antiperoxidase IgG.     

Evaluation of measurements of the conductivity of quarter milk samples for the early diagnosis of mastitis

Measurements of the conductivity of quarter milk samples were made in 31 cows in a 70-cow herd in southeast England, for a period of 15 weeks. Over this period, 42 per cent of cow-weeks and 20 per cent of quarter-weeks had an increase in quarter milk conductivity of 10 per cent of more compared with the mean conductivity of the previous 14 milkings. Fourteen per cent of quarter-weeks had an increase in conductivity of 15 per cent or more. The geometric mean somatic cell count (cell count) was higher in quarter-weeks with a 10 per cent or greater increase in conductivity than in quarter-weeks with a conductivity change of less than 10 per cent. At a conductivity threshold of 10 or 15 per cent and a cell count threshold of 200,000 or 400,000 cells/ml the specificity of this system was estimated to be 85 to 92 per cent, the sensitivity 40 to 54 per cent, the negative predictive value 87 to 93 per cent and the positive predictive value 33 to 55 per cent. The positive predictive value of the individual quarter milk conductivity was insufficiently accurate to be used as the sole criterion for the selection of quarters for early antibiotic treatment.     

Duration of protective immunity against ovine haemonchosis following vaccination with the nematode gut membrane antigen H11

To establish for how long protective antibody levels may be maintained, lambs were vaccinated with the gut membrane antigen H11 and challenged with Haemonchus contortus 14, 84, 126 or 168 days later. Compared to controls, mean faecal egg counts of vaccinated lambs were reduced by 97 per cent, 99 per cent, 92 per cent and 86 per cent respectively. Total worm burdens at postmortem five weeks after infection were reduced by 87 per cent, 94 per cent, 92 per cent and 62 per cent respectively. In vaccinated lambs, antibody levels to H11 peaked at about 60 days after the first vaccination and were maintained for the duration of the experiment. There was evidence of secondary antibody responses to H11 following challenge.