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Biomedical subjects

E F Logan

Publications and source records attributed to E F Logan.

At least 37 records · Page 2Linked to original sources
PubMed1983

The pathology of neonatal enteritis in calves with observations on E. coli, rotavirus and Cryptosporidium.

The mucosa of the small intestine of neonatal calves responds in a similar way to a variety of infectious agents. However, samples should be removed under general anaesthesia to avoid post-mortem artefacts. These include the separation of epithelium from the villous lamina propria and denudation of villous tips within a few minutes of death, and occur more rapidly in challenged animals. Pathological changes consist of blunting and fusion of the villi with a reduction of the columnar epithelium to cuboidal and occasionally squamous epithelium. A surface inflammatory exudate may be present, especially within 24 hours of challenge with enteropathogenic E. coli. Examination of several sites from the small intestine indicates a variable distribution for enteropathogens. Rotavirus is seen by immunofluorescence microscopy in epithelial cells principally in the proximal half of the small intestine, although they may occasionally be found in the distal half. By contrast, E. coli organisms adhere to enterocytes in the distal half of the small intestine. Cryptosporidia inhabit the brush border of the enterocytes enclosed within host cell microvillous membranes, principally in the distal half of the small intestine. Examination of the small intestine of neonatal calves for pathological changes and the presence and distribution of infectious agents complements bacteriological, virological and immunological techniques in the diagnosis of neonatal enteritis.

Animals↗
PubMed1983

Respiratory syncytial virus pneumonia in young calves: clinical and pathologic findings.

Nine young calves given respiratory syncytial virus by a combined intranasal and intratracheal route developed a severe respiratory tract disease in which coughing, tachypnea, and hyperpnea were prominent clinical features. Calves were euthanatized on postinoculation (initial) days (PID) 1 to 13. At necropsy, large areas of consolidation were present in the cranial, middle, accessory, and cranial parts of the caudal lung lobes of calves killed between PID 4 and 13. Histopathologic examination revealed widespread and severe lesions in small bronchi, bronchioli, and alveoli. Multinucleate epithelial syncytia on bronchiolar and alveolar walls, many containing eosinophilic intracytoplasmic inclusion bodies, were present in the lungs of calves killed on PID 4, 5, and 6. Necrosis and epithelial loss, hyperplasia, and metaplasia were also observed in the epithelium of small bronchi and bronchioli. The lumina of these airways were occluded to varying degrees with exudate. Exudate was present within alveoli, and interalveolar septa were markedly thickened. Collapse of the thickened septa produced large areas where alveolar air spaces were totally obliterated. Repair was evident in the lungs of calves killed at PID 10 and 13 with reepithelialization of damaged bronchiolar mucosa, organization of bronchiolar exudate leading to bronchiolitis obliterans, and peribronchial and peribronchiolar fibrosis. Inoculation of 3 calves by an intranasal route alone produced a less severe clinical disease with only minimal lesions present at necropsy.

Animals↗
PubMed1983

Scanning and transmission electron microscopic observations on the host-parasite relationship in intestinal cryptosporidiosis of neonatal calves.

The association of cryptosporidia with the intestinal epithelium of three neonatal calves was studied by scanning (SEM) and transmission (TEM) electron microscopy. Trophozoites and schizonts were observed embedded in the microvillous brush border of epithelial cells. Merozoites, released from schizonts, were seen free in the lumen and penetrating epithelial cells by SEM and TEM. Incorporation of microvilli into the parasitophorous envelope of trophozoites was seen by TEM. These findings indicate that cryptosporidia develop at an intracellular position in the apex of the epithelial cells following merozoite penetration.

Animals↗
PubMed1982

Isolation of Mycoplasma californicum from an outbreak of bovine mastitis and the experimental reproduction of the disease.

A mycoplasma-like organism was isolated from five cows with chronic incurable mastitis from one dairy herd. This organism was shown to be Mycoplasma californicum and was used to infect three cows by intramammary inoculation. The challenge organism was reisolated from all the infected quarters and the ensuing inflammatory response produced a chronic mastitis with a permanent drop in milk yield. Antibiotic treatment in one animal was unsuccessful.

Animals↗
PubMed1982

Enzyme-linked immunosorbent assay for Streptococcus agalactiae antibodies in bovine milk.

An enzyme-linked immunosorbent assay (ELISA) for the detection of Streptococcus agalactiae antibodies in bovine milk was developed using whole bacterial cells as antigen. Microtitre wells were coated overnight at room temperature with a 1:64 dilution of antigen in 0.05M carbonate-bicarbonate buffer at pH 9.6. After washing, milk whey samples diluted 1:40 were added, incubated overnight and again washed. After incubation with rabbit antibovine serum, bound antibody was detected with alkaline phosphatase conjugated sheep antirabbit serum. Using the ELISA, the levels of Str agalactiae antibodies in the individual quarters of the mammary glands of cows in a severely infected dairy herd were measured. A high proportion of cows had specific antibody to Str agalactiae in one or more quarters. Using ELISA in association with electronic cell count and bacterial isolation, it was possible to identify latent and subclinical carriers of infection.

Age Factors↗
PubMed1982

Mastitis in dairy cows associated with an aerotolerant campylobacter.

During the course of a study of an outbreak of mastitis in a dairy herd, an aerotolerant campylobacter was isolated from a milk sample. This organism was cultured and the right front quarters of four young Friesian cows were infected by intramammary inoculation. Each infected quarter developed an acute clinical mastitis which resolved spontaneously after 120 hours. The challenge organism was reisolated from one of the quarters.

Animals↗
PubMed1982

Ultrastructural changes in the small intestine of neonatal calves with enteric colibacillosis.

The small intestines of calves inoculated orally with the enteropathogenic strain of Escherichia coli 0101:K'B41',K99 were examined by electron microscopy at 3, 6, 12, 16, 21, 36, 69, 70 and 72 hours after inoculation. The challenge organism adhered to the mucosa of the distal small intestine from six hours post-inoculation. Bacteria were separated from the microvillous brush border by a gap of 200 to 300 nm in which bacterial fimbriae and the microvillous glycocalyx were seen. Bacteria never were found in epithelial cells but were present in macrophages in the lamina propria from 12 hours. At three and six hours, cytopathic changes were not seen in the small intestine, but from 12 hours epithelial cells on affected villi had blunt and thick microvilli and contained cytoplasmic inclusions. Epithelial cells were seen frequently in the process of extrusion from the villi, either singly, in small groups, or as ribbons of cells. Intervillous bridges, characteristic of villous fusion, were seen frequently from 69 hours.

Animals↗
PubMed1982

Electron microscopic visualisation of the in vitro phagocytosis of group B streptococci by bovine polymorphonuclear leucocytes.

The phagocytosis of group B streptococci by bovine blood polymorphonuclear leucocytes, after 30 minutes at 37 degrees C, was visualised using scanning and transmission electron microscopy. Several polymorphonuclear leucocytes were seen to have phagocytosed more than one bacterium, despite the initial ratio of bacteria to cells being unity. All bacteria within the cells appeared to be viable and some were undergoing multiplication.

Animals↗
PubMed1982

Distribution of cryptosporidia within the gastrointestinal tract of young calves.

Natural cryptosporidial infection of the gastrointestinal tract was recognised in four young calves by light microscopy and correlated with scanning and transmission electron microscopy in two of the calves. Seven to 10 sites of the small intestine were examined in each calf and cryptosporidia were most numerous in the posterior 50 per cent. None were found in the anterior 20 per cent of the small intestine, the abomasum or the colon, but they were present in the mucosa of the caecum of three calves.

Animals↗
PubMed1981

Effect of immunising pregnant sows with different Escherichia coli vaccines on the antibody levels in the piglet sera.

Six groups of pregnant sows were immunised with four different commercial Escherichia coli vaccines. Five groups were vaccinated parenterally while the other group was vaccinated orally and then parenterally. The colostral antibody titres to E coli O149 K91(B) K88 as measured by indirect haemagglutination were significantly higher in the vaccinated sows than in the controls. Oral priming by vaccine feeding as opposed to parenteral administration did not appear to produce an anamnestic response. Antibody levels in the piglets born to vaccinated sows were higher than in those born to control sows. Nevertheless a substantial proportion of piglets born to all sows had very low levels of passively acquired immunity.

Administration, Oral↗
PubMed1979

The pathogenesis of enteric colibacillosis in neonatal unsuckled calves.

The development of pathological lesions in the small intestine of neonatal calves is described. Seven newborn calves were challenged orally with a known enteropathogenic strain of E coli 0101k?(A) and killed at varying times after inoculation. Adhesion of bacteria to the mucosa of the small intestine was observed in all calves. A few organisms were seen in the distal small intestine at three hours after inoculation and thereafter adhesion progressed anteriorly along the intestine in calves killed from six to 36 hours. In these calves pathological changes occurred between six and 12 hours after inoculation. Villi were stunted and thickened and the epithelial surface was irregular. A further calf, anaesthetised from five-and-a-half to 10 hours after inoculation and repeatedly sampled from the distal small intestine, developed similar lesions abruptly at nine hours after inoculation. Villus and crypt lengths in the challenged calves were compared with those in three normal uninoculated control calves.

Animals↗
PubMed1979

Quantitative observations on experimental reo-like virus (rotavirus) infection in colostrum-deprived calves.

Ten calves were challenged with one of two strains of reo-like virus (rotavirus). Changes in the daily faecal and urinary outputs were monitored and packed cell volume, plasma sodium, potassium and urea levels were measured. Faeces were examined for the presence of rotavirus by direct electron microscopy and immunofluorescence in cultures of PK(15) cells. All calves excreted rotavirus in the faeces for several days. Two calves remained clinically normal throughout the experiment, but in the remaining calves, faeces became mucoid in consistency and yellow-white in colour. In only two calves did the daily faecal output exceed 500 g with a fall in the dry matter content to less than 10 per cent. Slightly elevated blood urea levels and hyperkalaemia were the only changes observed in blood chemistry and these quickly returned to normal. Virus antigen was observed in the epithelial cells by immunofluorescence in the proximal and middle small intestine of calves. Pathological lesions occurred predominantly in the proximal small intestine of nine calves examined.

Animals↗
PubMed1978

Antibodies to Leptospira in the sera of aborted bovine fetuses.

Antibodies to Leptospira serotypes were detected in sera from 15 (6.9 per cent) of 218 aborted fetuses, but were not detected in the sera from 196 non-aborted fetuses. Fourteen (6.4 per cent) sera from the aborted fetuses had antibodies to strains belonging to the Hebdomadis serogroup and 1 (0.5 per cent) had antibodies to a strain belonging to the Icterohaemorrhagiae serogroup. These antibodies were predominantly immunoglobulin M whereas in the dams, antibodies belonged to both immunoglobulin M and G classes.

Abortion, Veterinary↗