Chronic infection with Trichostrongylus vitrinus in sheep. Pathological changes in the small intestine

Eight four-month-old sheep were infected daily for 90 days with 2500 Trichostrongylus vitrinus larvae. Infections were patent by week 3; mean faecal egg counts reached a peak of 645 epg at week 5, then subsequently declined. Mean worm burden at slaughter was 6100 (range 60--25,080). Two sheep had visible lesions in the small intestine at slaughter. In both sheep, numerous shallow red depressed areas extended for 5 to 7 metres distal to the pylorus while, in one, more extensive irregular depressed areas occupied the first 1.5 metres. Microtopographical examination and scanning electron microscopy showed that these affected areas were devoid of villi and contained numerous worms embedded in the mucosa. Histological examination revealed many similarities with the lesions caused by T colubriformis. Subtotal villous atrophy and crypt elongation were present in the intestines from five of the remaining six sheep, and in these the mucosa contained numerous mononuclear cells and intraepithelial globule leucocytes.     

Seroepidemiological survey of maedi-visna virus infection in sheep and goat flocks in Quebec.

Maedi-visna, a chronic viral disease of adult sheep characterized by progressive dyspnoea or neurological manifestations, was first recognized and described clinically in Canada in 1970. Seroepidemiological study was conducted in sheep and goats in various areas of Quebec. Sera of 10% of the animals of selected flocks were collected and specific antibodies against maedi-visna virus were tested by a modified direct complement fixation test. Results show seropositive rate of 67.6% for Sherbrooke sheep; of 40.5, 41.1 and 47.1% for Quebec, Saint-Hyacinthe and Nicolet sheep respectively and only 29.2 and 20.0% positive sera in l'Assomption and Rimouski animals. Prevalence rate of positive goats varied according to geographic areas (0 to 36.8%). Statistical analysis of various factors, e.g. age, breed, mode of raising, origin and size of flock showed no relation between these factors and the geographic areas. But, some clinical problems in the sheep flocks such as cough, rapid breathing, mortality and abortion were associated with high infection rate (greater than or equal to 50%) to maedi-visna virus. In goats, no correlation was demonstrated between these clinical signs and serological results. Our results suggest that it is important to consider this disease in an adequate program of preventive medicine in Quebec.     

Seroprevalence of maedi-visna in Canadian sheep.

A serological survey of Canadian sheep over one year of age was conducted to estimate the seroprevalence of maedi-visna. An indirect enzyme-linked immunosorbent assay was used. An analysis of 14,047 sera from 286 randomly selected flocks provided an estimate of the seroprevalence of 19% and a mean flock prevalence of 12%. Sixty-three percent of the sampled flocks had one or more seropositive sheep. There appeared to be higher prevalences in sheep in Quebec (40%) and Nova Scotia (27%). An increased prevalence with increased age and flock size was noted.     

Pathological changes in kidneys of dogs with natural Leishmania infection.

A study was made of the nephropathy in canine leishmaniasis produced in ten adult dogs naturally infected with Leishmania infantum. Renal function analyses were performed (uraemia, creatinaemia, plasma proteins, biochemistry and urinary sediment), the humoral immune response (fluorescent antibodies and levels of serum IgG, IgM and IgA) was assessed and histopathological studies were carried out. Correlation of the results showed acute renal insufficiency which was reversible in two animals (endotheliomesangial glomerulonephritis) and irreversible in four cases corresponding to glomerulonephritis in its Type I and Type II proliferative forms; extensive increase in the glomerular basal membrane, proliferation of mesangial cells and growth of the mesangial matrix were observed, as was a widespread incidence of immune complex deposits. Two animals showed chronic renal insufficiency. Lack of renal changes (minimal-changes glomerulonephritis) in two dogs was accounted for in one animal by an almost complete absence of symptoms and in the other by chronic viscerocutaneous symptoms; neither showed more than a slight immunoglobulin response.     

The occurrence and distribution of maedi-visna virus infection in lower Austrian sheep breeding establishments

In a period of one year blood samples of 374 sheep of Lower Austrian flocks were examined in intervals of two months for antibodies against Maedi-Visna (MV). Further on specific attention was paid to the prevalence of MV-infection in the flocks. The antibody-titers were determined by means of agar gel-immunodiffusion test. In 5 (23.8%) of 21 flocks 45 (12.0%) of the sheep were seropositive. Seroprevalence varied within the examined breeds: 19 (27.1%) of 70 Karakul-sheep, 18 (28.1%) of 64 East-Friesian milk-sheep, 7 (9.4%) of 74 Merino sheep and 1 (0.9%) of 111 mountain sheep. None of 55 black-headed sheep showed MV seropositive reaction. Clinical symptoms of Maedi-disease were especially observed in milk-sheep and for the first time in Austria in Karakul-sheep. Unfavorable housing conditions (insufficient room, bad climatic conditions), breed specific behavior patterns (crowding of Karakul-sheep) and a high prevalence of MV infections promote a high incidence the disease.     

The seroprevalence of maedi-visna in Ontario sheep flocks and its relationship to flock demographics and management practices.

The objectives of this study were to describe the serological prevalence of maedi-visna in a sample of Ontario sheep flocks, and to identify management and demographic variables that were associated with seroprevalence for maedi-visna. A sample of 103 sheep flocks in Ontario was randomly selected from those flocks participating in the Red Meat Plan. The owners of these flocks were surveyed regarding management procedures on their farms, and blood samples were taken from a random sample of ewes in each flock. At least one ewe tested serologically positive, based on the agar gel immuno-diffusion test, in 69.9% of the farms. Positive serological reactions occurred in 20.9% of the 3880 sheep tested. Flock demographics and farm management variables were considered in a multiple regression model, and several factors were positively associated with higher maedi-visna seroprevalence rates. These included the average age of the flock, the number of years the owner had been sheep farming, the practice of using foster ewes, the practice of allowing lambs to have contact with other ewes that are lambing, and the average pasture acreage per ewe.     

The effect of a natural maedi-visna virus infection on the productivity of South African sheep

A cohort study was conducted in order to measure the effect of the chronic indurative lymphocytic mastitis caused by the South African strain of maedi visna virus (MVV) on the pre-weaning growth of lambs born either of naturally infected or uninfected ewes kept under similar conditions. Fifty naturally infected ewes as well as another 40 from a maedi-visna-free source to be used as control animals, were purchased and kept in separate flocks which were managed in a similar way. All the ewes were of the same breed and 3-4 years old. During the adaptation period, and through the mating, pregnancy and lactation periods they were periodically monitored for the presence of MVV serum antibodies. The lambs were weighed at birth and thereafter every 2 weeks until the age of 90 days, when they were weaned. The ewes were then slaughtered, and their udders examined histologically and the number of lymphocytic follicles were counted and assessed. Although the calculated values indicated a correlation between the number of follicles in the udder and the reduction in the growth rate of the lambs, this was not statistically significant. Similarly, despite higher counts of lymphoid follicles in the udders of sero-positive ewes as compared to those that were sero-negative and the lower ewe productivity indexes in infected ewes, no statistically significant differences were found in the indexes of ewes in different follicle categories.     

实验性鸭疫里氏杆菌病病理学动态变化

对90只11日龄鸭通过颈部皮下人工接种鸭疫里氏杆菌,分别在感染后12h、24h、36h、48h、60h、72h剖杀,观察其动态病理变化。结果表明,鸭在感染24h后就开始出现浆液纤维素性心包炎、肝周炎、气囊炎,并持续整个病理过程。组织学病变主要为肝脏、心脏、脾脏、气囊等表面增厚,有大量浆液纤维素性渗出物,其中有嗜中性粒细胞和单核细胞浸润;心肌细胞和肾小管上皮细胞颗粒变性,肝细胞脂肪变性和凝固性坏死,脾脏淋巴细胞减少,脑膜水肿充血。证实了鸭疫里氏杆菌主要侵害浆膜和肝脏,引起多发性浆膜炎和肝坏死。     

Experimental infection of bovine mammary glands with Streptococcus agalactiae during the nonlactating period

Two experiments were done to determine the rate of intramammary infection (IMI) in dairy cows during the nonlactating period. In experiment 1, all glands were equally exposed to Klebsiella pneumoniae and Streptococcus agalactiae for the first 3 weeks after the start of the nonlactating period. Nearly all new IMI was caused by S agalactiae. In experiment 2, the susceptibility of nonlactating mammary glands to new IMI by S agalactiae after direct inoculation into the lactiferous sinus was determined. During the 1st month of the nonlactating period, 30% of inoculated glands became infected. During the last month of the nonlactating period, 90% of inoculated glands became infected.     

Physiological and morphological changes in bovine mammary glands following intramammary infusion of recombinant interferon-gamma.

Eleven lactating dairy cows were used to evaluate the response of bovine mammary glands to increasing doses of recombinant bovine interferon (rBoIFN)-gamma. Right front and rear quarters were intramammarily infused with eight different doses (10(2) U to 2 x 10(8) U/quarter) of rBoIFN-gamma; each dose was tested in at least two quarters. Left udder halves served as within animal controls in which quarters were injected with a saline placebo or were not infused at all. Milk secretion samples for compositional analysis were collected from each quarter prior to infusion and at 6, 24, 36 and 48 h following infusion. Animals were slaughtered immediately following the 48 h sampling period and mammary tissue was obtained for morphometric analyses. Milk composition was similar between control quarters and those quarters infused with up to 10(5) U of rBo-IFN-gamma during the entire sampling period. Quarters infused with 10(6) U and 10(7) U of rBoIFN-gamma had higher milk somatic cell counts (SCC) following treatment compared with preinfusion values. Changes in the composition of mammary secretion were most dramatic in quarters infused with greater than or equal to 10(8) U of rBoIFN-gamma as indicated by the significant increase in SCC and milk pH with a concomitant decrease in lactose concentration when compared with pre-infusion values or with control quarters. Morphometric analysis of tissue demonstrated an increase in stroma, a decrease in luminal area, and a marked increase in the number of infiltrating leukocytes in those quarters infused with the higher doses of rBoIFN-gamma.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serological survey and epidemiological investigation of maedi-visna in sheep in Finland

A survey for antibodies to maedi-visna virus (MV) in the Finnish sheep surveillance flocks was conducted in 1994. Examination of a total of 12931 serum samples from animals over 1 year of age from 545 flocks (81% of all flocks) revealed eight seropositive flocks and the subsequent epidemiological investigation yielded one additional seropositive flock, indicating a low prevalence of 1.6%. The infection was very probably imported from Sweden in 1981, but it was not detected until the survey was conducted 13 years later. The entire primary infection flock was slaughtered in 1995. 77% of the sheep were seropositive but the animals were clinically healthy and only one (5%) of the contact flocks of the primary infection flock had contracted the infection. This secondary infection flock, 77% of which was seropositive, was slaughtered in 1994; however, animals in this flock had respiratory problems and the lungs of three sheep showed typical MV lesions. Seven (24%) of its contact flocks had contracted the infection and these each had one or two seropositive animals except for one flock which had seven (18%) seropositive animals. The results show that the initial spread of MV can be insidious and wide before infection is revealed in surveys or any clinical cases are encountered.     

Age changes in extramural digestive glands of sheep and rabbits in the postembryonic period

Background:The study of the peculiarities of the anatomy of sheep and rabbits’ digestive systems is an important way to improve the efficiency of these animals’ breeding.Aim:The aim of the presented research was to study structural changes of such digestive glands as the liver and the pancreas which occur in the process of ontogenesis in sheep and rabbits.Methods:Sheep of the “Kazakh fat-tailed semi-coarse-wooled” breed (n = 8) raised in the “Sayan” private peasant agriculture and rabbits of the “Grey Giant” breed (n = 8), raised on the mini rabbit farm of the Agriculture Faculty of Shakarim University were used in the research.Two experimental animal groups were formed (of sheep, “Kazakh fat-tailed semi-coarse-wooled” breed, n = 8; rabbits, “Grey Giant” breed, n = 8). The liver and pancreas’ ontogenesis development has been studied in these animals.Results:The study presents a holistic view of the macro-microscopic structure of the liver and the pancreas of animals in crucial age periods, stages, and phases of postembryonic ontogenesis (by the example of sheep and rabbits). The authors have traced age stages of adaptive change and structural-functional change of stromal-parenchymatous structures of the liver in sheep and rabbits taking into account stages and crucial phases of development.Conclusion:Development of the liver and the pancreas are characterized by discontinuous growth in the process of postnatal ontogenesis. A crucially important period is the first months after birth, during which the weight and functionality of these organs grow rapidly.     

The expression of intermediate filaments in canine mammary glands and their tumors

Monoclonal antibodies specific for different types of intermediate filaments (cytokeratin, vimentin, desmin and neurofilaments) were used to study the histogenesis of canine mammary glands and 57 canine mammary tumors by immunocytochemistry. The intra- and interlobular duct epithelium, acinar, and intralobular myoepithelial cells stained positively for cytokeratin. Peripheral ductal and acinar cells, as well as interstitial cells, stained positively for vimentin. A similar staining pattern was seen in adenomas, complex adenomas, benign mixed tumors, ductular carcinomas, and one myoepithelioma-like tumor. Additionally, cytokeratin positive cells were scattered interstitially in one single adenoma, most complex adenomas, some benign mixed tumors, complex carcinomas, and in the malignant mixed tumors. All stromal cells stained positively for vimentin. The fibrosarcomas were positive only for vimentin, while the following expressed both desmin and cytokeratin: epithelial-like cells in one adenoma, three complex adenomas, the myoepithelioma-like tumor, the single comedo carcinoma, two complex carcinomas, the single lobular carcinoma, one malignant mixed tumor, and three osteosarcomas. Epithelial-like cells in one adenoma, six complex adenomas, two benign mixed tumors, two complex carcinomas, the lobular carcinoma, and the malignant schwannoma stained for neurofilaments. Three tumors, one adenoma, one complex adenoma, and the lobular carcinoma expressed both desmin and neurofilaments in addition to cytokeratin and vimentin. The results show the expression of different types of intermediate filaments and indicate that there might be a stem cell origin in most of the canine mammary tumors.     

Incidence of indurative lymphocytic mastitis in a flock of sheep infected with maedi-visna virus

Sheep in a flock in which 88 per cent of the ewes had antibodies to maedi-visna virus were clinically examined for udder induration during lactation and after drying off. On both occasions about half of the ewes had indurated udders. Histological examination revealed lymphocytic mastitis associated with maedi-visna virus infection, in the udders of six of 25 hoggs (24 per cent), 21 of 39 shearlings (53.8 per cent) and 42 of 67 ewes (62.7 per cent). Distinct lung lesions were found in 8 per cent of the hoggs, 12.5 per cent of the shearlings and 10 per cent of the ewes. The results of a clinical examination of dry udders were correlated with the histological findings.     

Serological studies of antibodies against maedi-visna virus in sheep in Austria

883 sheep from 68 flocks were tested for the prevalence of antibodies against Maedi/Visna-(M/V)virus. As serological method the Agar Gel Immunodiffusion Test (AGID) was performed, 9.5% of the blood samples were positive against M/V, 1.7% showed questionable results. The highest incidence of serum-antibodies showed the Texel (47.7%) and Milk sheep (26.1%). No antibody titers were found in Mountain and Suffolk sheep. Merino sheep had antibody titers against M/V in 2.6% and Mountain sheep crossbreeds in 1.7%.     

Clinicopathological investigation of primary, uncomplicated maedi-visna virus infection.

Maedi-visna virus infection in a flock of sheep in Scotland was associated with respiratory disease, neurological disease, mastitis and lameness. The major clinical signs were dyspnoea (particularly on exercise), progressive fore- and hindlimb ataxia and balance defects, mammary induration and multilimb lameness, occasionally with enlarged carpal joints. Pathological examinations revealed lesions in the lungs, central nervous system, mammary glands and joints which were consistent with those induced by maedi-visna virus. The was no clinical or pathological evidence of concurrent sheep pulmonary adenomatosis, and pulmonary bacterial infections, when they occurred, were superimposed on the lesions due to maedi-visna virus.