Experimental infection of the mouse mammary gland with Campylobacter coli.

Campylobacter coli strains of bovine and avian origin were inoculated into the mammary gland of mice. A bovine strain isolated from a case of mastitis produced gross and histological changes in most of the glands; one bovine and one avian faecal isolate did not. Histologically, lesions were characterised by neutrophil infiltration in the alveolar spaces and necrosis and oedema in the interalveolar tissue. On bacteriological examination, the bovine mastitis strain could be isolated from most of the glands, but neither of the faecal strains. The mouse, therefore, appears to provide a convenient model for studying campylobacter mastitis.     

Immune globulin studies of the "collapse syndrome" in suckled calves.

A total of 351 single suckled beef calves were blood sampled during the first three days of life and thereafter twice weekly until five samples had been obtained. Eighty four calves suffered from diarrhoea and 23 of these died. No relationship could be found between the total circulating immune globulin level of a calf and its subsequent fate, suggesting that the syndrome with which many calves were affected is different in character from other forms of neonatal bovine diarrhoea.     

Experimental infection of guinea pigs with Chlamydia. 1. Pathomorphological studies]

The changes that occurred following nasal instillation of a bovine strain of Chlamydia psittaci were characterized by hypertrophy and proliferation of epithelial cells and exudates containing polymorphonuclear leukocytes, with acute bronchopneumonia and less intense inflammatory reactions in nasal and tracheal mucosa, spleen and pulmonary lymph nodes. The intestines, liver, kidney and brain were scarcely affected. There was little prospect of complete recovery from the clinically mild, or even subclinical, pneumonia within the period of observation since the causal agent was present continuously from the 12th hour to the 91st day after infection.     

Some studies on equine strains of Escherichia coli.

A detailed study was made of 194 equine strains of E. coli, involving biochemical and serological characters. In these, the equine strains closely resembled E. coli from other sources, and shared antigenic characters with strains isolated from different animal species.     

Experimental studies with Stronglyloides papillosus in goats

Unusual clinical and pathological observations in the field in goats and sheep suffering from Strongyloides papillosus infection prompted experimental work on this parasite. Goats were infected percutaneously with either single or multiple, low or high levels of S. papillosus. Young goats up to 12 months of age were found to be the most susceptible. Some animals, however, showed substantial resistance to infective doses. Clinical signs included transient diarrhoea, misshapen, elongated faecal pellets terminally, dehydration, anorexia, cachexia, gnashing of teeth, foaming at the mouth, anaemia and nervous signs such as ataxia, a wide-based stance, stupor and nystagmus. A 'pushing syndrome' was seen in 22% of the animals. The pathological changes are described and included enteritis, status spongiosus in the brain, hepatosis leading to rupture of the liver, nephrosis, pulmonary oedema, interstitial pneumonia and pneumonia. About 6% of the goats died acutely from fatal hepatic rupture. The development of an acquired immunity was determined. The immunity elicited an allergic skin reaction at the application site of larvae or injection sites of larval metabolites. This immunity, however, could be breached by large doses of larvae. The most profound clinicopathological changes induced by the parasites were an anaemia (most pronounced in the young goats) and hypophosphataemia. Trace element analyses provided evidence of Cu, Mn and possibly Se deficiencies in some goats.     

Experimental udder infections with Escherichia coli. 4. Discussion of the pathogenesis of acute mastitis

The correlations among findings obtained from experimental Escherichia coli udder infection and reported in the three previous communications are discussed in this paper. The defence capabilities elucidated included specific and unspecific activities of non-epithelial cells, primarily neutrophilic granulocytes, macrophages, lymphocytes, plasma cells, and mast cells, as well as the capability of epithelial cells proper of absorbing pathogenic material from lumens of lactiferous ducts and milk cisterns and of storing such material within intracytoplasmic vacuoles. Hence, alterations in the course of pathogenesis of acute coli mastitis were found to be of complex nature and could be properly followed up by their morphological patterns.     

Experimental fetal infection with bovine viral diarrhea virus. I. Virological and serological studies.

The serological and virological results of an experimental infection of bovine fetuses with bovine viral diarrhea virus are presented. Four fetuses, 120-165 days gestational age, were inoculated in utero with a second passage virus strain. Two fetuses received a sham-inoculum. A humoral immune response in the virus-inoculated fetuses, was demonstrated three weeks later. In three fetuses only IgM and IgG1 were detectable. The serum from the fourth fetus also contained IgG2 and IgA. Bovine viral diarrhea virus-neutralizing antibodies were detected in two fetuses. These two fetuses inoculated at 135-150 days gestational age, represent the youngest reported bovids, giving a specific response in three weeks following an experimental infection with bovine viral diarrhea virus. The fetal sera did not contain heat-labile factors, which could mediate the neutralization. The virus was not reisolated from any of the fetuses, but viral antigen was nevertheless demonstrated by immunocytochemical methods in sections of several of the fetal organs, primarily lymphoid tissues.     

Arthropathy associated with Brucella abortus strain 19 vaccination in cattle. II. Experimental studies

Attempts to reproduce in calves the arthropathy associated with Brucella abortus strain 19 (S19) vaccination by direct intra-articular injection of S19 or virulent Brucella cells were unsuccessful. Intra-articular injection of rabbits and a calf with immune complexes isolated from the synovial fluid of a field case produced clinical and histological signs of arthropathy accompanied by the development of rheumatoid factor.     

Experimental bedsonia infections in calf. 2. Pathomorphologic studies]

Tracheal inoculation of bovine strains of Bedsonia was often followed by inflammatory processes in lung, trachea, nasal mucosa and also spleen, lymph nodes and brain. Lesions in the duct system and alveoli of the lung consisted of exudates containing neutrophilic granulocytes and proliferation of epithelial and mesenchymal cells. The initial changes were evidently located in the bronchioli. Elementary bodies were present in variable numbers. The formation of lesions seemed to be influenced by route of infection and concentration of the causal organisms in the inoculum.     

Epidemiological studies of congo red Escherichia coli in broiler chickens.

This prospective cohort study was designed to confirm the association between Congo red binding Escherichia coli (CREC) and E. coli air sacculitis in commercial broilers. It was also designed to evaluate CREC as an air sacculitis risk factor and to explore the CREC relationship to other air sacculitis risk factors (poultry house temperature, air-ammonia levels, and presence of other diseases). In addition, this study was used to assess a possible role of the broiler-breeder flocks and hatchers in the spread of CREC air sacculitis. Congo red E. coli-associated airsacculitis risk was based on CREC exposure of the chicks in the hatchers. Breeder flocks with greater than 30 CREC colonies/plate from hatcher air sampling tests were placed in the high risk group; flocks with less than five CREC colonies/plate were placed in the low risk group. Increased risks of death due to air sacculitis (RR = 2.26), and increased death rates due to CREC air sacculitis (RR = 9.45) in high-risk flocks, identified CREC as an important air sacculitis risk factor. The attributable risk percent of CREC airsacculitis from hatcher exposure of CREC was 89.4%, pointing to the hatcher as the source of CREC infection. The association of specific broiler-breeder flocks to high levels of CREC in the hatchers, and subsequent air sacculitis, suggests that the broiler-breeders are the ultimate source of CREC.     

Experimental studies on maedi-visna

In order to study pathogenicity of sheep lentiviruses, to obtain monospecific sera and to perfect ELISA, 3 experiments with different strains were carried out for 4 yr. In expt 1, one clone only of a French maedi-visna strain (564-79) elicits a clear seroconversion in inoculated sheep. In expt 2, K1514 is more immunogenic than K796 and PPV: intratracheal route seems more efficient than intracerebral route. Sheep infected by ts mutants (expt 3) are early positive as wild strain K796. Nevertheless, the level of positivity is less important than for the parental strain, suggesting that the defect of the ts mutants is not limiting their replication in vivo. An important result is the lack of clinical signs and anatomical and histopathological lesions, in spite of frequent isolations of virus from buffy coat cells. These results suggest that: different enhancing factors have to be taken in account in the apparition of clinical signs; all the clones are not infectious; viral infection might be effective with several types of virions.