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Eighteen oestrus-synchronised ewes were infected experimentally with 1500 sporulated oocysts of Toxoplasma gondii between 80 and 90 days of gestation. The infection induced pyrexia and specific antibody in all the ewes. One ewe resorbed its fetus, five ewes aborted and 12 delivered live, congenitally-infected lambs whose pre-colostral serum was antibody-positive. Tissues from the aborted fetuses and placentae from the live lambs were examined for toxoplasma infection by polymerase chain reaction (PCR) amplification of the Bi gene and by mouse inoculation. Using a simple protocol of tissue preparation without DNA extraction and a nested format, PCR was as sensitive as mouse inoculation. Placental cotyledon gave a higher sensitivity of detection than brain, lung or liver, and 16 of 19 placentae were positive by PCR compared with 13 of 18 by mouse inoculation. In mock-infected tissues, as few as 10 tachyzoites could be detected. The PCR could be applied to tissues unfit for mouse inoculation.

A survey was made of 37 dairy farms in Wirral, mid-Cheshire, mid-Somerset and Dyfed, Wales, to assess the incidence and prevalence of lameness in the cows between May 1989 and September 1991. The incidence was obtained from records made whenever a cow was examined for lameness or received preventive foot-trimming. The mean annual incidence was 54.6 new cases per 100 cows with a range from 10.7 to 170.1 and the mean values during summer and winter were 22.9 and 31.7, respectively. The prevalence of lameness was measured by regular visits at which locomotion was scored on a scale of 1 to 5, and the prevalence of lameness was calculated for each visit as the proportion of cows with scores of 3 or more. The mean annual prevalence over the whole period was 20.6 per cent with a range from 2.0 to 53.9 per cent for the 37 farms. The mean prevalences during summer and winter were 18.6 and 25.0 per cent, respectively. The prevalence measured at a single visit in midsummer or midwinter was significantly correlated with the mean prevalence over the whole corresponding period and may be useful as an assessment of the extent of lameness in a herd and the efficacy of control measures. There was evidence that training farmers to recognise early cases of lameness and request veterinary treatment resulted in a marked reduction in the duration of cases of lameness.

BACKGROUND--Nitric oxide is a potent dilator of the pulmonary vasculature. There have been no previous reports on the action of nitric oxide on the arterial duct. OBJECTIVES--To determine the responses of isolated post-term arterial duct rings from lambs to oxygen, prostaglandin E2 (PGE2) and the nitric oxide donor, 3-morpholinosydnonimine (SIN-1). SETTING--Experimental laboratory. SUBJECTS--Six neonatal lambs. METHODS--Lambs aged 1-5 days were killed and the arterial duct and aorta excised and cut into rings. These were mounted on tension gauges in organ baths containing Krebs-Henseleit solution. Rings were exposed to increasing concentrations of oxygen, PGE2 and after preconstriction with potassium (40 mmol/l) to SIN-1. Tension and relaxation responses were recorded. RESULTS--Increased oxygen tension resulted in increased tension in the ductal rings above 88.9 mm Hg as previously described. No response to PGE2 occurred before or after ductal rings were exposed to oxygen. SIN-1 caused relaxation of smooth muscle in the arterial duct to a similar degree as that in the aortic rings. CONCLUSIONS--As previously shown, oxygen is a potent constrictor of the arterial duct. The post-term arterial duct does not relax in response to PGE2 possibly as a result of inactivation by oxygen of the special sensitivity of the duct to PGE2. SIN-1 is a potent smooth muscle relaxing agent in the term arterial duct and may have a role in the initial management of neonates with duct dependent pulmonary circulation.

BACKGROUND Long-term maintenance of arterial duct patency by a catheter technique would be a valuable nonsurgical method of palliation for duct-dependent circulations. We used a new method: percutaneous radiofrequency thermal balloon angioplasty of neonatal lamb arterial ducts. METHODS AND RESULTS Radiofrequency balloons 5 or 6 mm in diameter were introduced via the femoral vein of 32 neonatal lambs and inflated to 4 atm. In 28, a radiofrequency generator was used to heat the saline/contrast mixture in the balloon to 65 degrees C (n = 2), 75 degrees C (n = 2), 85 degrees C (n = 10), 100 degrees C (n = 8), and 120 degrees C (n = 6). In 4 lambs, angioplasty alone was performed. Lambs were recatheterized to assess patency at intervals up to 78 weeks. Immediate results showed the arterial duct to be patent in all cases, with a mean rise in systolic pulmonary artery pressure of 13 +/- 8 mm Hg and a mean rise in pulmonary artery oxygen saturation of 12 +/- 15%. With a mean follow-up of 45.7 +/- 28 weeks, 3 of the 4 (75%) angioplasty alone ducts closed, but only 5 of the 28 (18%) radiofrequency-treated ducts (P < .05). The mean rise in oxygen saturation between the superior vena cava and the pulmonary artery was 7.6 +/- 7% at last follow-up. Follow-up angiography of the arterial ducts showed the development of stenoses in all patent ducts. CONCLUSIONS Radiofrequency thermal balloon angioplasty leads to long-term arterial duct patency in lambs in > 80% of the treated group and is significantly more effective than balloon angioplasty alone.

Activation of transcription within chromatin has been correlated with the incorporation of the essential histone variant H2A.Z into nucleosomes. H2A.Z and other histone variants may establish structurally distinct chromosomal domains; however, the molecular mechanism by which they function is largely unknown. Here we report the 2.6 A crystal structure of a nucleosome core particle containing the histone variant H2A.Z. The overall structure is similar to that of the previously reported 2.8 A nucleosome structure containing major histone proteins. However, distinct localized changes result in the subtle destabilization of the interaction between the (H2A.Z-H2B) dimer and the (H3-H4)(2) tetramer. Moreover, H2A.Z nucleosomes have an altered surface that includes a metal ion. This altered surface may lead to changes in higher order structure, and/or could result in the association of specific nuclear proteins with H2A.Z. Finally, incorporation of H2A.Z and H2A within the same nucleosome is unlikely, due to significant changes in the interface between the two H2A.Z-H2B dimers.

Within 13 days of the experimental infection of 15 oestrussynchronised ewes with 2000 sporulated oocysts of Toxoplasma gondii at 80 to 90 days of gestation 11 had aborted. The infection induced pyrexia and specific antibody in all the ewes. One ewe resorbed its fetus, 11 ewes aborted and three delivered, at full term, live congenitally infected lambs whose pre-colostral serum was antibody-positive. Tissues from the aborted fetuses and placentae from the live lambs were examined for toxoplasma infection by polymerase chain reaction (PCR) amplification of the B1 gene and by mouse inoculation. The live lambs were all shown to be infected by both methods, but there was no evidence of infection in any of the tissues from the acute phase abortions, suggesting that these fatalities occurred before the placenta or the fetus had been invaded by T gondii . Such toxoplasma-induced, acutephase abortions are likely to be impossible to diagnose from fetal tissues. These results have implications not only for the diagnosis of naturally occurring ovine abortions but also for the understanding of the pathogenesis of toxoplasma-induced abortion.

Information from 37 dairy farms, in four regions of England and Wales provided data on 8991 lesions and the preventive trimming of 4837 cows' feet., American Association of Bovine Practitioners Proceedings of the Annual Conference, 1996

A survey of cubicles and indoor and outdoor walking surfaces on 37 farms served by four veterinary practices in Somerset, Cheshire, Wirral and west Wales was carried out in 1989 to 1991. A study of the space requirements of Friesian/Holstein cows at pasture showed that they required approximately 240 cm x 120 cm lying space and a further 60 cm lunging space for rising. By these standards, 87 per cent of the cubicles were too short and 50 per cent were too wide or too narrow. Over 1500 observations on cows lying down, rising and standing indicated that only 12 per cent of the cubicles permitted real freedom of movement; 91 per cent of top partition rails were judged to be too low and 70 per cent of bottom rails too low or too high. In addition, the kerb was very high in 76 per cent of the cubicles. As a result, 10 per cent of cows appeared moderately or severely restricted when lying down, 33 per cent when rising and 55 per cent when standing. Over 2000 cubicle beds were also studied; 75 per cent had a concrete base and of those, 63 per cent were judged to have too little bedding and 11 per cent next to none. Higher incidences and prevalences of lameness were associated with limited borrowing space (P

Four separate experiments were carried out by dosing dogs (Beagles and Border collies) and red foxes with protoscoleces obtained from hydatid cysts in sheep from mid-Wales. The dogs and foxes were killed at intervals over a period from 34-180 days after infection and the intestines were examined for Echinococcus granulosus. Border collie dogs were efficient hosts in that large numbers of worms developed, with gravid segments present by 55 days after infection; but Beagle dogs were poor hosts in that only small numbers of immature worms developed. Foxes were poor hosts in that few or no worms developed, but gravid segments were seen in three of 29 foxes. The worms showed morphological features similar to the 'sheep' rather than the 'horse' strain.

The antigenic relationships of seven stocks of Trypanosoma vivax from different geographical areas were compared by immune lysis, passive protection and crossed immunoelectrophoresis.Sera from calves infected with T. vivax were titrated against trypanosome populations isolated early in infection by the immune lysis test. The results showed that three stocks isolated from one area of Nigeria were closely related and had antigens in common with stocks from other areas. Sera from cattle naturally infected with trypanosomes in Zambia contained lytic antibody to three Nigerian and one East African stock. Lytic antibody to African stocks was not detected in the sera of calves infected with a stock of South American origin. The detection of inter- and intra-area cross-reactions suggest that there may be a limited number of antigenic types in nature.Sera from five selected calves which contained lytic antibody to homologous and heterologous stocks were injected into mice. Subsequent challenge showed that the inje...

SUMMARYThe epidemiology of hydatid disease in man in England and Wales, based on the data collected between 1981 and 1983 at the Hydatid Reference Laboratory of the Public Health Laboratory Service, is presented. The incidence of hydatid disease was 42 cases per annum, with 2 cases per million population occurring in Wales and 0·2 per million in England. The highest prevalence was in London amongst the immigrant population. The incidence in the indigenous population was 15·5 cases per annum, with 5·6 cases per million occurring in South Powys, parts of South Wales and Herefordshire. The population most at risk is the rural, farming community in that area, but the West Midlands is also an apparent focus of the disease.

Albendazole was given orally to sheep with naturally occurring live pulmonary and hepatic cysts. The viability of pulmonary cysts was established before treatment by thoracotomy and needle puncture. Both 10 and 20 mg/kg/day doses were found effective in that no viable protoscoleces were found after six weeks' treatment in either group while untreated controls still had viable cysts. In addition, treated animals showed macroscopic and electron microscopic changes. Bone marrow toxicity probably occurred in two sheep.

(1959). The Parasites of Domestic Animals in the Bahama Islands. Annals of Tropical Medicine & Parasitology: Vol. 53, No. 3, pp. 341-346.

(1971). Critical tests of levamisole as an anthelmintic in the horse. Annals of Tropical Medicine & Parasitology: Vol. 65, No. 1, pp. 87-91.

The life cycle and pathogenicity of a strain of Eimeria isolated in Great Britain from turkey poults by single cell inoculation are described and, using the criteria laid down by Tyzzer, the species is identified as E. adenoeides.The life cycle is of the same general pattern as in other Eimeria species, consisting of two asexual and one sexual generations.The organism is highly pathogenic for young poults, a dose of 200,000 oocysts producing 100 % mortality in 3-week-old birds and smaller doses causing reduced weight gain. Birds 11 weeks old resisted a dose of 3 million oocysts.The gross and microscopic pathology of the infection is described. No changes were found in the blood picture.

(1971). The epidemiology of Echinococcus infection in Great Britain. Annals of Tropical Medicine & Parasitology: Vol. 65, No. 1, pp. 71-79.

Two Friesian cows were used to attempt to produce colostrum containing a high concentration of clostridial antibodies which could be fed to newborn lambs in order to passively transfer immunity to diseases caused by clostridia. One cow was given a commercial multicomponent clostridial sheep vaccine in two successive pregnancies and the second cow in one pregnancy. The first cow produced a low concentration of epsilon antitoxin (Clostridium perfringens, type D) in its blood and colostrum after the first course of three injections of vaccine. A higher concentration was produced by cow 2 after a course of six injections and by cow 1 after a further course of four injections in its next pregnancy. Two hundred ml of colostrum from cow 1 (after the second course of vaccine) was given to 12 newborn colostrum-deprived lambs. All showed a high concentration of antitoxin 48 hours later. The lambs were actively immunised by injections of the same clostridial vaccine at three and nine weeks or six and 12 weeks old and all produced sufficient antitoxin to protect up to slaughter at 24 weeks. It is concluded that colostrum from cows vaccinated with sheep clostridial antigens can be fed to protect lambs passively.

The presence of benzimidazole-resistant strains of equine small strongyles was confirmed in horses at two properties in north west England by a series of faecal egg counts and larval cultures after treatment with mebendazole. A trail formulation of mebendazole in combination with piperazine citrate gave greater reductions in faecal egg counts than mebendazole alone but was much less effective than pyrantel embonate or dichlorvos.

1. A method is described for the measurement of liver blood flow without hepatic venous catheterization by the injection of a single dose of bromosulphthalein and the analysis of the graph of the plasma disappearance of the indicator. 2. The rationale of the method was tested in three systems which covered a wide range of flow rates. The first system was a physical model with a haemodialyser in which the calculated flow could be compared with the flow measured directly. The second was in anaesthetized dogs, in which the calculated flow was compared with that measured by continuous infusion and hepatic venous catheterization, based on the Fick principle. The third system was in unanaesthetized turkeys, in which metabolism of bromosulphthalein does not occur. The calculated flow was compared with the flow measured simultaneously by the uptake of colloidal particles by the Kupffer cells. 3. In all three systems the correspondence between the two methods of measuring liver blood flow was good, the differences between them being not statistically significant. 4. The method has been applied to measurements of liver blood flow in man and animals and gives results comparable with those reported by other workers.

The immune status of a group of sheep naturally infected with hydatid cysts was investigated. Low specific anti-hydatid antibody (Sab) titres and negative results in intradermal and leucocyte migration tests occurred in hosts with high hydatid antigen-stimulated lymphocyte transformation(LT). Total(non-specific) IgG was elevated in infected sheep and was positively correlated with LT. Circulating hydatid antigen (cAg) was detectable in some infected sheep, but not in all of those with low Sab. Relationships between eAg, Sab and immune complex levels suggest that most eAg is present in immune complexes.

In a field survey of ovine infectious keratoconjunctivitis, the microbiological flora of 240 clinically unaffected eyes from sheep in 10 flocks was compared with the flora of an equivalent number of clinically affected eyes from 12 natural outbreaks of the disease. Totals of 16 and 17 genera of bacteria were recovered from unaffected and affected eyes, respectively. Staphylococcus, bacillus and branhamella were isolated significantly more often than the other genera of bacteria, in both the unaffected and affected eyes (P less than 0.05). Branhamella ovis and Escherichia coli occurred more frequently in affected eyes, and Staphylococcus aureus occurred more frequently in severely than mildly affected eyes. The genera Mycoplasma and Acholeplasma were isolated from both groups, and Mycoplasma conjunctivae occurred in 92 affected eyes (38.3 per cent), and 27 unaffected eyes (11.3 per cent).

A description is given of the life history and pathogenicity of a species of Eimeria, derived from a single oocyst infection in a coccidia-free bird, and subsequently identified as E. meleagridis.There are two asexual generations followed by the sexual generation. The first schizogony cycle occurs in the small intestine and the second and sexual generations are restricted to the caeca.The organism is not pathogenic but the sexual stages produce marked caseous lesions in the caeca. It is immunologically distinct from a pure strain of E. adenoeides and cannot be transmitted to chickens.

A probable new member of the herpes virus group caused an outbreak of fatal infections in captive vervet monkeys. The pathological findings and some of the properties of the virus are described.

A species of Trichuris is described from domestic cats in the Bahama Islands, and identified as T. campanula. Previous descriptions of the two species of Trichuris in the domestic cat are summarised, and it is concluded that both are valid species.

The immune responses of the turkey and fowl to intra-rectal infections with tissue containing Histomonas meleagridis were studied.