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Biomedical subjects

I G Wright

Publications and source records attributed to I G Wright.

At least 91 records · Page 5Linked to original sources
PubMed1981

The transmission of Babesia bovis in herds of European and Zebu x European cattle infested with the tick, Boophilus microplus.

Transmission of Babesia bovis by the tick Boophilus microplus was studied in 4 breeding herds of European and Zebu x European cattle under different levels of tick infestation. The observations consisted of weekly counts of female ticks on the cattle, monthly serological tests for antibodies to B. bovis, examination of tick larvae from the pasture to determine B. bovis infection rates and comparison of the suitability of paddocks for tick reproduction. The rate of transmission (inoculation rate) was estimated in terms of the daily probability of infection and consisted of the product of the mean daily tick infestation head-1 and the babesial infection rate in tick larvae. The theoretical value of the minimum inoculation rate required to produce stability of babesiosis is 0.01. This value was exceeded only in a herd of European cattle with minimal tick control and grazing on a pasture favourable for tick reproduction. Instability of babesiosis occurred in the other herds of European cattle after tick numbers had been reduced by pasture spelling and strategic dipping and after reduction in the babesial infection rate in ticks apparently caused by unfavourable environmental conditions. Over a period of years, the tick infection rates also declined as a consequence of the reduction in numbers of ticks. The Zebu x European cattle failed to generate inoculation rates greater than the minimum level, even though no tick control measures were applied. This was attributed to lower babesial infection rates in the ticks than those observed in a comparable herd of European cattle and to the high tick resistance of the Zebu crosses which maintained the tick populations at low levels. Both factors combined to produce a low inoculation rate.

Administration, Oral↗
PubMed1980

Changes in the haemolytic activity of serum complement during acute Babesia bovis infection in cattle.

The haemolytic activity of serum complement was measured in cattle during acute Babesia bovis infection. The level fell significantly on day 5 post infection (p.i.) and was not detectable by day 10 p.i. After clinical recovery between days 15 and 20 p.i. haemolytic activity was again detected in serum and gradually returned to the pre-infection level. The components of both classical and alternative pathways were involved in complement depletion and factors such as protease secretion by the parasites, antigen-antibody reactions, and the release of haemoglobin were implicated as causes of the decline. The absence of complement activity during the acute phase of the disease may interfere with immune mechanisms at a critical time for the host.

Animals↗
PubMed1980

Serum carboxypeptidase B levels during acute and mild Babesia bovis and acute Babesia bigemina infections of cattle.

Serum carboxypeptidase B (SCPB) levels were measured in splenectomised calves and in non-splenectomised cattle infected with three virulent and one avirulent strains of Babesia bovis, and in splenectomised calves infected with virulent Babesia bigemina parasites. SCPB levels commenced falling three days post-infection in animals infected with virulent B. bovis strains and fell significanttly terminally. In animals infected with the avirulent B. bovis strain, the SCPB levels were not significantly altered. Animals infected with B. bigemina had no significant changes in their SCPB levels. Fatal infections were uniformly observed in animals with virulent B. bovis, but only two of six animals infected with B. bigemina and none infected with avirulent B. bovis, died.

Acute Disease↗
PubMed1980

The irradiation of Babesia bovis. 1. The difference in pathogenicity between irradiated and non-irradiated populations.

Babesia bovis parasites attenuated by 35 krads gamma irradiation and parasites not exposed to irradiation, were injected into intact 2-year-old Hereford steers. All five animals receiving non-irradiated blood died but the five animals which received irradiated blood were only mildly affected. Highly significant differences were observed in changes to plasma fibrinogen, serum fibrinogen-like proteins, packed cell volume, partial thromboplastin time, prothrombin time, blood kinins, and plasma kininogen levels in the control animals but non-significant changes in these parameters occurred in the group receiving iradiated blood. Significant changes in the antiplasmin alpha 2M, and the antithrombin levels occurred in control cattle but not in the group receiving irradiated blood. Parasite multiplications rates and maximum parasitaemias were similar in both groups. Irradiation reduced the dose of living parasites from 1 x 10(8) to 2.5 x 10(3), but this was not the reason for the mild reactions. It was concluded that irradiation had selected an avirulent parasite population.

Animals↗
PubMed1980

Babesia bovis (Argentina): analysis of paracoagulation proteins in acutely infected cattle.

The proteins in plasma and serum from cattle infected with Babesia bovis that react with protamine sulphate and ethanol have been characterized. Their sizes and chain structures suggest they are intermediates in the conversion of fibrinogen to cross-linked fibrin. In addition, comparison with reference proteins and in vitro systems strongly indicate the proteins are, in the main, the products of thrombin activation in vivo and not those of fibrinolysis.

Animals↗
PubMed1979

Babesia bovis (argentina): analysis of fibrinogen-like proteins during infection.

Fibrinogen and fibrinogen-like proteins (FLP) were isolated from plasma and serum of cattle acutely infected with Babesia bovis. The sizes and chain structures of these proteins were examined and clotting assays performed. The results indicated that the blood was in a hypercoagulable state due mainly to enhanced production of hydrogen bonded fibrin and offset partly by slight inhibition of chain cross-linking. The latter appeared due to a Factor XIII inhibitor. Reduction of A alpha chains of plasma FLP was not evident, nor could lower molecular weight remnants be regularly detected strongly suggesting that fibrin(ogen) lysis rarely occurred. Similarly the size and chain structure of the majority of noncoagulable FLP of serum was consistent with their being the product of coagulation and not fibrinolysis. Only in heavily infected splenectomized cattle were products from lysed cross-linked fibrin detected and these constituted only about 3% of total serum FLP.

Animals↗
PubMed1979

Acute Babesia bovis infections: renal involvement in the hypotensive syndrome.

Splenectomised calves in metabolism cages were infected with Babesia bovis. During the infection, urine samples were collected and analysed for electrolytes, proteins, kinin, and urinary kallikrein. During the later stages of the infection there were significant reductions in urinary volume, water intake, urinary kinin, kallikrein, and electrolytes. Proteinuria was detected from 3--8 days postinfection of which 15--20% was haemoglobin and most of the remainder was albumin (70--75%). Fibrin degradation products, fibrinogen-like products, and haptoglobin were not detected. Degeneration of cortical tubules was detected by histological studies. As these tubules produce urinary kallikrein it seems probable that diminished glomerular blood flow and hence glomerular filtration rate are due to decreased production of this enzyme.

Animals↗
PubMed1979

Immunity in cattle to Babesia bovis after single infections with parasites of various origin.

Sixty calves, 3 to 6 months old, were vaccinated once against Babesia bovis in groups of 10, by the following methods: (a) tick infestation; (b) inoculation of virulent parasites obtained from the tick-infested animals immediately after infection; (c) inoculation of the parasites used in (b) attenuated by passage through splenectomised calves; (d) inoculation of commercially-available, living, attenuated vaccine; (e) inoculation of virulent parasites obtained from the tick-infested animals in (a) one year after infection; (f) inoculation of the parasites used in (e) attenuated by passage. All vaccinated animals were maintained tick-free and were strongly immune to challenge with a heterologous strain of B. bovis approximately 4 years after vaccination. There was no difference in immunogenicity between any of the B. bovis populations.

Animals↗
PubMed1978

Babesia bovis (argentina): components of the cryofibrinogen complex and their contribution to pathophysiology of infection in splenectomized calves.

A cryofibrinogen complex, found in the plasma of cattle acutely infected with Babesia bovis (argentina), was characterized. The fibrinogen-like proteins of the complex were isolated and the structure of their polypeptide chains analysed. In general, the chain structure was similar to that of soluble non-crosslinked fibrin (fibrinogen) although chains indicating some degree of fibrin crosslinking were often detected. Only rarely did the chain structure suggest that fibrinolysis occurred. It was concluded that the complex was produced by activation of the coagulation system but that fibrinolysis did not occur to any marked degree. The complex was implicated in assistance to the sludging of erythrocytes in the internal organs which is a feature of the pathogenesis of the disease.

Animals↗
PubMed1977

Babesia bovis (argentina): observations of coagulation parameters, fibrinogen catabolism and fibrinolysis in intact and splenectomized cattle.

The results of this paper indicate that cattle infected with B. bovis (argentina) have a markedly altered and activated coagulation system. A degree of thrombin activation occurs due partly to release of thromboplastin-like substances from lysed erythrocytes but due primarily to activation of kallikrein by babesial proteases. This produces a hyperfibrinogenaemia, particularly in intact cattle, with soluble fibrin complexes constituting up to one-third of the total fibrinogen concentration. High molecular weight non-coagulable fibrinogen-like proteins are detected terminally but more so in splenectomized cattle. Plasminogen concentration decreases in splenectomized but not intact cattle while low molecular weight fibrinogen degradation products are not easily detected. It is suggested that a hypercoagulable intermediate state with little or no fibrin deposition occurs rather than terminal disseminated intravascular coagulation.

Animals↗
PubMed1977

Acute Babesia bigemina infection: changes in fibrinogen catabolism.

Plasma from cattle infected with Babesia bigemina contained soluble fibrin in monomer and high molecular weight complex forms. Fibrin(ogen) degradation products were not constantly detected and there appeared to be little or no evidence to suggest fibrinolysis or fibrin deposition. It is suggested that classical disseminated intravascular coagulation does not occur during B. bigemina infection.

Animals↗