E.R. Young

The in vitro uptake of tritiated nucleic acid precursors by Babesia spp. of cattle and mice

Abstract Irvin A. D. , Young E. R. and Purnell R. E. 1978. The in vitro uptake of tritiated nucleic acid precursors by Babesia spp. of cattle and mice. International Journal for Parasitology 8 : 19–24. Blood and mice infected with Babesia microti and B. rodhaini , and from cattle infected with B. divergens and B. major , was incubated in Eagles medium for 24 h in the presence of tritiated purines and pyrimidines. Uptake of these compounds was assessed by liquid scintillation counting and by autoradiography. Hypoxanthine, adenosine and adenine were readily incorporated by all four species of parasites. Thymine, thymidine and uridine were generally not incorporated. Uptake of [ 3 H]hypoxanthine by B. microti occurred within minutes of exposure to the precursor. The amount of [ 3 H]hypoxanthine incorporated by B. rodhaini -infected erythrocytes was proportional to the percentage of parasitized cells The results suggest that structural analogues of hypoxanthine and other purines may be incorporated and act against intra-erythrocytic Babesia .

Further studies on the uptake of tritiated nucleic acid precursors by Babesia spp. of cattle and mice

Abstract Irvin A. D. and Young E. R. 1979. Further studies on the uptake of tritiated nucleic acid precursors by Babesia spp. of cattle and mice. International Journal for Parasitology 9 : 109–114. An in vitro culture technique developed earlier was used to study the metabolism of nucleic acid precursors by Babesia microti and B. rodhaini of mice and by B. divergens and B. major of cattle. [ 3 H]Hypoxanthine was readily incorporated by all species of parasite, and the presence of leucocytes did not affect this uptake. When parasites were maintained in culture their ability to incorporate [ 3 H]hypoxanthine fell rapidly after 24 h, but when B. major was maintained at 4°C its subsequent ability to incorporate [ 3 H]hypoxanthine persisted for at least 3 days. This finding could be of practical value in assessing infectivity of stored blood in vitro . On autoradiography, [ 3 H]hypoxanthine appeared to be incorporated into both DNA and RNA of parasites. Salvage pathways for purine metabolism appeared to be important in all species of Babesia whereas for pyrimidine metabolism salvage pathways were more important for murine babesias and the de novo pathway more important for bovine species. This difference may relate to different permeabilities of bovine and murine erythrocyte membranes or may be a more fundamental species difference.

Babesia divergens infection of the Mongolian gerbil: titration of infective dose and preliminary observations on the disease produced.

Abstract A tritration of Babesia divergens piroplasms in the Mongolian gerbil was carried out in which 10 8 , 10 7 , 10 6 , 10 5 and 10 4 , B. divergens -infected erythrocytes were inoculated intraperitoneally into groups of 5 gerbils. Generally, the inoculation of decreasing numbers of parasites resulted in proportionately increased prepatent periods and severe, usually fatal disease, but gerbils which received 10 4 , B. divergens -infected erythrocytes had minimal disease reactions and a subsequent sterile immunity to challenge. Preliminary observations on the pathogenesis of the disease in the gerbil showed a significant fall in PCV and rectal temperature prior to death, an increase in the weight of the spleens of infected animals and the presence of B. divergens -infected erythrocytes in the spleen, liver, brain and bone marrow on post-mortem examination.

Experimental Haemonchus placei infection in calves: Influence of anaemia and numbers of larvae on worm development

Differences in the pre-patent period and egg production of Haemonchus placei in calves with single infections of 50,000, 125,000 or 500,000 third stage larvae, are described. These differences, together with increased egg production following transfusion and delayed development of the parasite in the anaemic host, suggest that the severe anaemia in the host caused by large numbers of H. placei larvae, can be detrimental to parasitic development.

A comparison of Babesia infections in intact, surgically splenectomised, and congenitally asplenic (Dh/+) mice

Abstract Infections with Babesia rodhaini and B. microti were studied in congenitally asplenic (Dh/+) mice, surgically splenectomised mice and intact mice. Mice without spleens were more susceptible to infections than intact mice, but Dh/+ mice were less susceptible than surgically splenectomised mice, indicating that some functional splenic activity had been taken over by other tissues in Dh/+ mice. It is suggested that this functional activity may be mediated by natural killer (NK) cells, and that Dh/+ mice could prove of value in the study of babesiosis in general and NK activity in particular. Male mice were more susceptible to infection than females.

Babesia major in Britain: Blood-induced infections in splenectomized and intact calves

Abstract A strain of Babesia major, originally isolated from field collections of Haemaphysalis punctata in Kent, England was maintained in splenectomized calves by the intravenous inoculation of infected blood. Rapid passage from carrier calves, that had recovered from a tick-induced infection, resulted in a marked increase in virulence; 4 out of 6 calves of the second passage underwent fatal infections and the others suffered severe reactions. Five splenectomized and 5 intact calves of the same breed and age were infected with the same number of infected erythrocytes (RBC). The intact calves reacted mildly with maximum parasite counts ranging from 1 1000 RBC to 5 1000 RBC; haemoglobin levels and packed cell volume values, however, fell sharply but recovered swiftly. The group of splenectomized calves exhibited one fatal case, 2 severe reactions and 2 mild infections; maximum parasitaemias varied from 7 1000 RBC to 322 1000 RBC. Packed cell volumes and haemoglobin concentrations declined to low levels and took several weeks to return to normal. It is concluded that B. major should be regarded as a potential pathogen of British cattle.

The effect of treatment with imidocarb diproprionate on the course of Babesia divergens infections in splenectomized calves, and on their subsequent immunity to homologous challenge

Abstract The drug imidocarb diproprionate (IMDP) was injected intramuscularly into groups of splenectomized calves at 2·4 mg per kg body weight at various times before and during their reactions to syringe-passaged Babesia divergens infections. When the drug was given 1 or 2 weeks before infection it had a prophylactic effect, inducing appreciably milder B. divergens reactions in the calves and complete immunity to challenge. When it was given simultaneously with the parasites, the development of the infection was almost completely suppressed and no immunity to challenge developed. If B. divergens infections were allowed to develop for 7, 14 or 21 days before treatment, the infections were sterilized by the drug but the animals retained an immunity to challenge. The strength of this immunity increased with the length of time that the parasites had been allowed to exist before treatment. These results demonstrate that IMDP is an effective drug against B. divergens infections but suggest that blanket-treatment of all animals in a herd at the first sign of the disease may not invariably prevent further redwater cases.

A statistical comparison of the behaviour of five British isolates of Babesia divergens in splenectomized calves

Abstract Isolates of B. divergens were obtained from redwater cases in England, Eire, Scotland and Wales, and their pathogenicity for splenectomized Friesian calves compared with that of the Weybridge strain by statistical means. The reactions of the calves were measured by observing their parasitaemia, febrile response, and change in haematological values. A principal component analysis of this data indicated that the reactions could be described in two dimensions. The principal component representing one dimension consisted largely of four variables (maximum parasitaemia, maximum febrile response, highest MCV and lowest PCV) whilst the principal component representing the other dimension consisted largely of two variables (maximum febrile response and total febrile response above 39·4°C.). The analysis showed that the Weybridge strain of B. divergens was not similar in its pathogenicity to the four field isolates. Its closest similarity was to the Hampshire isolate, which was made in the area where the laboratory strain was originally isolated. There was some indication that similarities between the isolates revealed in the analysis could have some geographical significance.

A comparison of anticoagulants for the analysis of glucose concentration and for haematological measurements in bovine blood

Abstract Blood samples were taken from 18 cows into a potassium oxalate-sodium fluoride mixture, or a potassium oxalate-ammonium oxalate-ammonium fluoride mixture, or into ethylene diamine tetraacetate. Haematocrit, and the concentrations of glucose in the blood and blood plasma, were determined in each sample. Blood samples from another 6 cows were taken into the same anticoagulant mixtures and stored at 4 °C., room temperature, or 37 °C. The concentrations of glucose in the blood and plasma, haematocrit, mean corpuscular volume, erythrocyte count, and haemoglobin concentrations were determined at intervals of up to 96 h. after collection. Blood taken into the potassium oxalate-sodium fluoride mixture had reduced values for haematocrit, but there were no significant differences in haematocrit between samples taken into the other 2 anticoagulants. Little difference in the glucose concentrations of whole blood was apparent in samples taken into the 2 fluoride containing anticoagulant mixtures, but plasma concentrations of glucose were significantly lower in the samples taken into the potassium oxalate-sodium fluoride mixture. Consistent values for all determinations were obtained up to 96 h. when samples were stored at 4 °C. Some haemolysis and glycolysis occurred during storage at higher temperatures. This was more severe in the potassium oxalate-sodium fluoride mixture than in the potassium oxalate-ammonium oxalate-ammonium fluoride mixture. It is concluded that the latter is preferable for blood to be used for the determination of glucose concentrations and for haematological measurements in the metabolic profile testing of dairy herds.

Reactions of splenectomized calves to the inoculation of blood containing Babesia divergens from an infected animal during its reaction and carrier phases

Abstract A series of experiments was carried out to see if there was any change in the virulence of B. divergens parasites harvested from an infected animal at intervals after its original infection. Groups of cattle were inoculated with low and high doses of parasites 10, 48, 105 and 196 days after inoculation of the donor. Eight parameters of their reactions were measured, and subjected to statistical analysis. The only significant differences between groups were those related to parasite dose, notably the prepatent periods to detectable parasites in blood smears and to a febrile response. There was a suggestion that an avirulent population of parasites was becoming predominant in the donor 196 days after inoculation, but this tendency was not sufficiently marked to be detected by statistical analysis.