[Gastrointestinal helminths of wild ruminants: observations on the chamois (Rupicapra rupicapra L.) in the Val Belviso reserve]

The results obtained in a survey on the gastrointestinal helminths of 32 chamois of the Riserva of Valbelviso on the Alpi Orobie are reported. All the animals were infested: the species identified with more frequence were O. circumcinta, M. marshalli, N. filicollis. Of great significance was the diffusion of N. filicollis, compared with other species of this genus, typical of the wild ruminants; Oe. radiatum, never previously observed in chamois, was also found. These results show that the promiscuity of wild and domestic ruminants in the pasture could interfere with the natural focality of the respective gastrointestinal nematodes.

The trichostrongyloid parasites of sheep in South Australia and their regional distribution

The species of trichostrongyloid nematodes present in 376 sheep from different agricultural regions of the state of South Australia were determined. Parasites encountered in the abomasum were Teladorsagia circumcincta, T. trifurcata, T. davtiani, Camelostrongylus mentulatus, Haemonchus contortus and Trichostrongylus axei. T. circumcincta was the species most commonly encountered, but C. mentulatus was widespread in arid areas. H. contortus was present in a small number of sheep only, mainly in southern areas. In the small intestine, Trichostrongylus vitrinus predominated in the wetter, southern districts, and T. rugatus in dry, northern areas. T. colubriformis was common, but was rarely dominant. T. probolurus was found in one sheep. Nematodirus filicollis was restricted to wetter, southern areas, while N. spathiger and N. abnormalis were widespread and predominated in dry areas. N. helvetianus was found once. Cooperia species were uncommon; species encountered were C. oncophora, C. surnabada and C. pectinata.

Worm burdens in cows. II. An analysis of the population of nematodes in the abomasa of adult dairy cows

Over a period of one year, from February 1979-February 1980, the abomasa of four dairy cows were examined each week for the presence of parasitic nematodes. Based on the identification of adult male worms, Ostertagia ostertagi (94%) and Trichostrongylus axei (75%) were the most prevalent species, and Haemonchus contortus was absent. Total worm burdens varied from zero (one cow) to 100,890. The geometric mean total number was 3011. The geometric mean number of arrested larval stages was 685. Of the adult worm burden, more than 85% consisted of O. ostertagi, about 12% of T. axei, the remaining 3% was other species. No relationship could be found between worm burdens and the age of cow, the weight of the abomasum or the milk yield. The adult Ostertagia burden was highest in winter, lowest in summer. Besides those of O. ostertagi, small numbers of arrested larvae of T. axei were observed from September onwards. Cows from farms with a zero-grazing system had significantly fewer worms than cows from other farms independently of the time of the year.

Multiple infections with Nematospiroides dubius in mice selected for liability to a single infection

The faecal egg counts and worm burdens of mice selected over 7 generations as refractory (R), random (Rd) or liable (L) to primary infection with Nematospiroides dubius were significantly different, but the antibody titres (generation 8 mice) after 21 days infection were similar, demonstrating that selection had separated populations of mice which differed in their innate immunity. Variations in adaptive immunity were also shown between the three colonies in terms of protection after challenge infections, self-cure reactions, humoral antibody titres and ability of immune serum from R, Rd and L donors to passively protect recipient Quackenbush (Q) strain mice. R mice were more refractory to primary infection and more proficient in acquiring protective levels of adaptive immunity than L colony mice. Correlation of the faecal parasite egg count after primary with that after secondary infection supported the conclusion that the genetic control of liability to primary infection and of the adaptive immune response following challenge infections were at least partially linked.

[The effects of postparturient anthelmintic treatment on ewes and their lambs (author's transl)]

Anthelmintic treatment of ewes after lambing resulted in partial suppression of the spring rise in egg counts in Frisian milch-sheep, lambing early in March and a rather satisfactory suppression of the spring rise in Texel ewes lambing late in March. The Frisian and Texel sheep were treated with 44 mg/kg and 66 mg/kg thiabendazole respectively. Beneficial effects of treatment were not observed in the ewes or their lambs compared with the controls. Particularly, treatment failed to produce any improvement of the gain in weight in the lambs. In the Frisian ewes, the haemoglobin content was determined at regular intervals. Both in the treated and in the untreated group, the haemoglobin content decreased significantly. Moreover, this decrease was correlated with the increase in faecal Haemonchus egg counts These results and those of previous experiments in conjunction with findings reported in the literature, lead to the general conclusion that farm management is highly decisive in answering the question as to how serious trichostrongylid and strongylid infections will be and the extent to which anthelmintic treatment of the ewes could have a beneficial effect.

Evaluation of the Cornell-Wisconsin centrifugal flotation technique for recovering trichostrongylid eggs from bovine feces

Several variables in the Cornell-Wisconsin centrifugal flotation technique were studied using helminthologically sterile bovine feces to which known numbers of Haemonchus contortus eggs had been added. Neither mode of mixing (levigation versus conventional), volume (15-60 mL) of water used for making the feces water suspension nor specific gravity (1.20-1.33) of the sucrose flotation solution affected egg recovery. Optimal times for centrifugation at 264 x g of first the feces water and then the feces sucrose suspension were three and five minutes respectively. Under these conditions 62.6% of the eggs were recoverable and there was a linear relationship between the number of eggs recovered and those added to the feces. About 30% of the unrecovered eggs were found in the fecal debris retained on the strainer. About 5% of the unrecovered eggs were found in the supernatant discarded after the feces water centrifugation and also in the matrix of the viscous sucrose solution. Addition of the detergent Triton X-100 caused a decrease in egg recovery. False negatives were not encountered between 3 to 70 epg; at 1.44 epg there was only one in 14 samples. Optimum procedures for the technique are presented.

[Macro-Baermann--a method for parasitological examination of herbage samples]

A Baermann technique for extraction of trichostrongylide larvae (L3) from herbage samples is described. The technique is a modification/simplification of a technique previously described by Persson (1974). On examination of 150-200 g samples 30-60% of larvae of Ostertagia ostertagi and Cooperia oncophora were recovered.

Quantitative studies of ovine haemonchosis. 3. The interpretation and diagnostic significance of the changes in serial egg counts of Haemonchus contortus in a sheep flock

An examination of the level and distribution of egg counts of H. contortus within an extensively managed flock of Merino sheep in south-east Queensland was carried out on three occasions over a ten week period. During this time the geometric mean egg count increased from 527 to 1331 eggs per gram, and although 26.3% of the flock were responsible for this increase, clinical evidence of haemonchosis was not observed. Examination of the distribution of counts supported the hypothesis that counts followed a negative binomial distribution. The values obtained for "k" (the index of over-dispersion), ranged from 0.5 to 1.4. However, on the two latter examinations, counts showed a divergence from the expected pattern (P = 0.015; P = 0.014). Further examinations of flocks at higher mean levels of count are required to establish if the trend towards a more normal distribution were maintained. The evidence from the present study and from outbreaks previously reported, suggested that in extensively managed sheep, the level of variance remained high as the mean egg count increased. It therefore appeared likely that in outbreaks of acute haemonchosis under grazing conditions, only a small proportion of the flock may become seriously affected.

The seasonal incidence of the major nematode genera recovered from sheep, cattle, impala and blesbok in the Transvaal

The seasonal incidence of helminth infestation in sheep, cattle, impala and blesbok was determined from fluctuations in the worm burdens of these animals exposed to natural infestation at particular localities in the Transvaal and slaughtered at various fairly regular intervals. The nematodes considered to be of major importance were Haemonchus spp. and Trichostrongylus spp. in all four hosts, Ostertagia spp. in sheep, Longistrongylus spp. in impala, Cooperia spp. in sheep, cattle and impala, Cooperioides spp. in impala, Impalaia spp. in impala and blesbok and Oesophagostomum spp. in sheep, cattle and impala.

Studies on the control of bovine ostertagiasis using a morantel sustained release bolus

The efficacy of a morantel sustained release bolus to control ostertagiasis in grazing calves was assessed. Administration of the bolus into the rumen of calves immediately before turnout on to spring pasture in May substantially reduced the level of pasture contamination with infective larvae later in the season. Compared with controls there was a 71 per cent reduction in worm burdens acquired over the entire grazing season with a mean improvement in weight gain of 24 kg. When administration was delayed until midsummer (July) a good anthelmintic effect was obtained but there was little reduction in pasture contamination levels. Worm burdens acquired over the grazing season were reduced by only 48 per cent with a mean weight gain advantage of only 9 kg compared with controls. The control obtained against Dictyocaulus viviparus by both treatments was not absolute, failing to prevent the development of mild parasitic bronchitis.

Studies on the anthelmintic effect of a sustained release pre-grazing treatment with morantel in grazing cattle in Sweden

The effect of a morantel sustained release bolus (MSRB) to control gastrointestinal parasitism in cattle grazing their first season was assessed under field conditions in Sweden. The MSRB was administered orally to calves immediately prior to turnout onto spring pastures in May 1978. The level of pasture contamination of infective larvae was decreased by 73 per cent in August and by 98 per cent in September. There was a 72 per cent reduction in worm burdens acquired over the entire grazing season. During the same period the mean improvement in weight gain was 21.5 kg per animal. Weight gains were also recorded during housing until slaughter in April 1979, i.e. 335 days after MRSB administration at which time the treated animals were on an average 17.1 kg heavier than controls.

Further studies on the anthelmintic effect of a sustained release pre-grazing treatment with morantel in grazing cattle in Sweden

The efficacy of a morantel sustained release bolus (MSRB) to control gastrointestinal parasitism in first season grazing cattle was assessed under field conditions in Sweden. The MSRB was administered orally to calves immediately prior to turnout onto spring pastures in May, 1979, or in mid-season (July). The level of pasture contamination with infective larvae was reduced by 99 per cent in September by treatment at turnout. The corresponding figure was 89 per cent when the MSRB was administered in July. There was a 95 per cent reduction in worm burdens acquired over the entire grazing season in cattle treated in the early season and a 44 per cent reduction in worm burdens of cattle treated in the mid-season. During the 132 days grazing period a 19.1 kg (p less than 0.01) mean weight gain advantage was achieved by the early season treated animals, while a 10.0 kg mean weight gain advantage was achieved by the mid-season treatment. The weight gain advantage at the end of the grazing season in the early treated cattle increased continually during the winter with a resultant mean difference of 44.4 kg (p less than 0.01) by April 1980. Over the same period the mean weight gain advantage of the mid-season treated animals gradually fell to a final of 5.5 kg.

The epizootiology of nematode parasites of sheep in a high-rainfall area of Zimbabwe

Fifty-two untreated lambs from a contaminated flock were slaughtered at regular intervals throughout the year, and their gastro-intestinal tracts were examined for the presence of nematode parasites. Haemonchus contortus and Oesophagostomum columbianum were found to be of major importance. The incidence of Haemonchus rose to a peak and remained at a high level throughout the winter through the fourth larval stages of the parasite predominated at this stage. Oesophagostomum columbianum was recovered in numbers unusually high for this species, the incidence of which remained at a relatively high level from March until October. The minor genera recovered were Trichostrongylus spp., Cooperia spp., Strongyloides papillosus and Trichuris ovis.

Nematodirus battus: scanning electron microscope studies of the duodenal mucosa of infected lambs

Lambs given 60 000 third-stage larvae of Nematodirus battus were killed on days 16, 20 22, 24 and 32 of the infection and the duodenal mucosa was examined by scanning electron microscopy (SEM). On day 16 of the infection the villi were long and finger-like and, although goblet cells were visible, the surface of the villi was not extensively folded, as is the surface of villi of uninfected control animals. By day 20 of the infection the villi had been reduced to flattened, plate-like structures or had formed low, irregular-shaped ridges. On this day of the infection the nematodes appeared to be enclosed by mucus-like material. As the infection progressed the intestinal damage was repaired, so that, by day 24 of the infection, the surface of the intestine was covered by short, smooth, finger-like projections and, by day 32 of the infection, the morphology of the intestine was somewhat similar to that of the control lamb. The possible role of villus atrophy and of mucus in the rejection of N. battus from the intestine is discussed.

The effect of a preparturient fenbendazole treatment on lactation yield in dairy cows

Studies carried out on nine farms in north-west England indicated that fenbendazole treatment of adult winter calving dairy cows in the dry period caused an overall increase of 173 kg in their subsequent lactation yield. There was some evidence to suggest that a correlation existed between pasture Ostertagia ostertagi larval burdens and subsequent serum pepsinogen and milk yield responses post treatment. Marked interherd and regional differences existed in the milk yield response to anthelmintic treatment and possible reasons for such results are discussed.

Observations on ostertagiasis in young cattle over two grazing seasons with special reference to plasma pepsinogen levels

The epidemiology of ostertagiasis in south west Scotland was studied in groups of cattle grazed through two successive grazing seasons separated by a period of winter housing. Towards the end of the first grazing season (September) the numbers of infective larvae (L3) on the pasture had increased to high levels (up to 24,000 L3 per kg) which resulted in high faecal egg counts, worm burdens, plasma pepsinogen levels and the occurrence of clinical ostertagiasis in the calves. By late spring (May) at the onset of the second grazing season, there was an almost complete mortality of the overwintered L3 on the pasture followed by the appearance of moderately high numbers of a new population of L3 in September (up to 9000 L3 per kg). The latter increase in the numbers of L3 was reflected by negligible faecal egg counts, low worm burdens and a moderate elevation of plasma pepsinogens in the second year animals. It therefore seems that although young cattle acquire a good immunity to Ostertagia ostertagi after one season at grass the small infections established in the early part of the second season are capable of contaminating the pasture to levels which could be dangerous for susceptible stock. An allergic reaction in the abomasal mucosa could be the basis of the elevated pepsinogens present in the second year animals.

Anthelmintic efficiency of oxfendazole, fenbendazole and levamisole against naturally acquired infections of Ostertagia ostertagi and Trichostrongylus axei in cattle

The anthelmintic efficiencies of oxfendazole, fenbendazole and levamisole, each at 4 dose rates spanning the manufacturers' recommended dosages were compared in beef cattle with naturally acquired infections of Ostertagia ostertagi and Trichostrongylus axei. In 8 of the 9 cases tested there was no significant increase in anthelmintic efficiency due to increased dose rates of any of the drugs. Percentage efficiencies and their standard errors, calculated from mean worm counts of pooled data for adult worms, developing 4th stage and early 4th stage larvae of O. ostertagi, were respectively, 86.9+/-4.2, 77.4+/-6.1, 74.5+/-7.3 for oxfendazole, 93.7+/-2.0. 80.7+/-6.8, 59.6+/-13.9 for fenbendazole and 69.7+/-6.9, 39.4+/-14.8, 31.2+/-22.6 for levamisole. Counts of O. ostertagi from cattle treated with oxfendazole and fenbendazole were not significantly different, but both were significantly lower than those from cattle given levamisole. Efficiency against T. axei exceeded 99% for all drugs. Practical implications for therapy and preventative control of ostertagiasis are discussed.

Field observations on the epidemiology of abomasal parasites in young sheep during winter and spring

A flock of spring born lambs was continuously exposed to natural parasite infection from birth until selected for slaughter in groups of two or three, at monthly intervals throughout winter and spring for abomasal worm counts. Meteorological data were recorded and regular estimates of infective pasture larval availability were made. Parasite population changes and inhibition patterns for Ostertagia spp, Haemonchus contortus and Trichostrongylus axei were recorded. Ostertagia spp were found to survive well both on the pasture and within the host, principally as arrested larvae. H contortus overwintered almost entirely in the host in the inhibited form and T axei overwintered mainly in the host, but in the adult stage.

Parasites of domestic and wild animals in South Africa. XII. Artificial transmission of nematodes from blesbok and impala to sheep, goats and cattle

Sheep were successfully infested artificially with the larvae of Haemonchus contortus, Trichostrongylus axei, Trichostrongylus falculatus and Impalaja nudicollis, cultured from the faeces of blesbok naturally infested with these nematodes. Haemonchus placei, Longistrongylus sabie, Trichostrongylus colubrifomis, T. falculatus, Impalaia tuberculata and Cooperia hungi likewise became established in sheep, goats and calves dosed with larvae cultured from the faeces of infested impala. Sheep and goats could also be infested with Cooperioides hamiltoni and Oesophagostomum columbianum of impala origin, but Cooperioides hepaticae could not be transmitted either to these hosts or to calves.