Metabolic energy pathways in Theileria annulata sporozoites and their significance in sporozoite-bovine lymphocyte interactions in vitro.

The existence of metabolic energy pathways has been studied in extracellular T. annulata sporozoites using chemicals known to inhibit specific energy-generating pathways, and their role during invasion of bovine peripheral blood lymphocytes (PBL) by the sporozoites determined in an in vitro system. An inverse relationship was depicted between the dose of various chemicals and the number of T. annulata sporozoites invading PBL: as the concentrations of the inhibitor drugs increased, the number of T. annulata sporozoites within the lymphocytes decreased. An ultracytochemical study demonstrated the presence of the respective pathway marker enzymes, i.e., lactic dehydrogenase (LDH) in the cytosol and within mitochondria, succinic dehydrogenase (SDH) on the mitochondrial membranes and in the contiguous matrix, and cytochrome oxidase (CO) between the inner and outer mitochondrial membranes, in infective T. annulata sporozoites fixed in situ within whole salivary glands of 3-day fed Hyalomma anatolicum anatolicum ticks.

Bovine babesiosis: steps towards an irradiated vaccine.

A series of experiments leading towards the field trial of an irradiated blood-derived vaccine against Babesia divergens, common cause of redwater in cattle in Europe, is described. Initially a number of isolates of B. divergens were made from the blood of sick animals in a variety of localities in the british Isles. These isolates were cryopreserved and then characterised by inoculation into groups of spenectomised Friesian calves, whose reactions were statistically analysed. Attempts were made to prepare a vaccine against B. divergens infection using diluted infected blood, but when these failed it was found that irradiation of infected blood within the range of 24 to 32 kilorads and its intravenous inoculation into calves produced the required immune response without pathogenic effects. An irradiated blood-derived vaccine produced by the irradiation of infected blood at 25 or 30 kilorads was used in a field trial in Ireland, and vaccinated calves were protected against a field challenge which caused redwater in 10 control cattle, six of which had severe reactions.

Serological comparison of British Theileria mutans and Japanese T sergenti.

A serological comparison between British Theileria mutans and Japanese T sergenti using the indirect fluorescent antibody test, showed that the two parasites were indistinguishable. On the basis of this and previous findings it is suggested that the British parasite is identical with the Japanese one and that its name should therefore be changed to T sergenti.

Babesia divergens: the immunisation of splenectomised calves during irradiated piroplasms.

Groups of three splenectomised calves were inoculated with 1 . 2 x 10(10) Babesia divergens-infected erythrocytes irradiated at 24, 28, 32, 36 and 40 kilorads. Control calves were inoculated with 1 . 2 x 10(7) or 1 . 2 x 10(4) non-irradiated parasites. While control animals all experienced severe reactions, animals receiving blood irradiated at 24, 28 and 32 kilorads had mild reactions and were solidly immune to an homologous challenge of 1 . 1 x 10(4) Babesia-infected erythrocytes. Animals receiving parasites irradiated at 36 and 40 kilorads had limited ability to resist the challenge.

Protection of cattle against Babesia major by the inoculation of irradiated piroplasms.

Two experiments were carried out on Babesia major in splenectomised calves. In the first one, the parasite was titrated and a linear relationship was observed between infective dose (10(2)--10(7) parasites) and onset of disease. In the second experiment aliquots of 1.2 X 10(10) parasites were irradiated at doses of 24, 28, 32, 36 and 40 krads and inoculated into groups of calves, while control calves received 1.2 X 10(7) or 1.2 X 10(4) parasites. Animals which received parasites irradiated at 24 or 28 krads had mild reactions and were immune to homologous challenge. Animals receiving parasites irradiated at the higher dose levels had limited ability to resist the challenge.

Isolation of a virulent strain of Ehrlichia phagocytophila from the blood of cattle in the Isle of Man.

A blood sample from a cow in the Isle of Man caused a severe Ehrlichia phagocytophila infection when inoculated into a splenectomised calf. The parasite was passaged successively into a further splenectomised calf and then into two intact animals. One of the splenectomised calves and one of the intact animals died of the infection which was characterised by causing a sustained febrile response apparently correlated with a marked invasion of monocytes by the rickettsiae.

Ultrastructure of Babesia major vermicules from the tick Haemaphysalis punctata as demonstrated by negative staining.

The ultrastructure of Babesia major vermicules was studied in samples derived from the haemolymph of Haemaphysalis punctata adults and negatively stained with phosphotungstic acid. Most of the organelles observed were typical of those found in apicomplexan parasites. These were the apical complex with the polar ring and the ribs, micronemes and subpellicular microtubules. The number of ribs was 27 or 28. The outer membrane of the pellicle was composed of a large number of fibrils running along the length of the parasite. The inner membrane had large numbers of irregularly scattered holes. A cytoplasmic organelle similar to the granular body described in Theileria annulata ookinetes was seen for the first time in a B. major vermicule.

Babesia divergens in splenectomised calves: immunogenicity of lyophilised plasma from an infected animal.

An experiment was carried out in which three groups of splenectomised calves were inoculated on three occasions at fortnightly intervals with lyophilised plasma from an animal reacting to Babesia divergens infection. Two weeks later these three groups of calves, together with three control groups, were challengpd with isologous, homologous or heterologous isolates of B divergens. Limited protection to isologous and homologous challenge was observed in the calves inoculated with plasma.

Experimental transmission of Babesia major by Haemaphysalis punctata.

Using a newly isolated strain of Babesia major and a clean strain of laboratory reared Haemaphysalis punctata it was shown that adult female ticks could be alimentarily infected by feeding on infected calves but that larvae and nymphae could not. All stages were able to transmit the parasite. Two syringe passages of B major resulted in a complete loss of infectivity to ticks.

The ultrastructure of penetrating stages of Babesia major infecting the ovary of Haemaphysalis punctata.

The ultrastructure of penetrating stages of Babesia major merozoites responsible for causing trans-ovarian infection of the tick Haemaphysalis punctata was studied. These merozoites were different from forms of other Babesia species previously described in the tick in that they were highly pleomorphic. Most of the organelles found in these forms were similar to those found in other stages: however, the apical complex was found to be very active. Micronemes were found to be predominant in the cytoplasm of these merozoites and a cytoplasmic projection anterior to the polar ring and bounded by concentric rings was visible. A polar ring with radiating ribs, and microtubules was present. It is thought that the apical complex of these merozoites plays an important role in assisting the parasite to infect the ovary of the tick.

A differential diagnostic criterion for Babesia major and Babesia bigemina vermicules from tick haemolymph.

Babesia major mature and immature vermicules in the haemolymph of Haemaphysalis punctata were measured and found to be significantly larger than vermicules of Babesia bigemina. Mature B. major vermicules had a mean length of 15.53 micrometer and mature B. bigemina vermicules had a mean length of 11.79 micrometer. This difference provides a new criterion for the differentiation of the two species.

Babesia divergens in splenectomised calves: titration of the infective dose.

Two experiments were carried out in which Babesia divergens was titrated in splenectomised calves. In the first experiment, a linear relationship was observed between infective dose (10(5)--10(9)) parasites) and onset of disease. In the second experiment, a similar trend was observed for infective doses of 10(2)--10(6) parasites, but 10(3) parasites appeared to be the minimum dose required to produce overt disease or resistance to homologous challenge in inoculated animals.

Evaluation of the indirect fluorescent antibody test for Babesia major and Theileria mutans in Britain.

Use of the indirect fluorescent antibody (IFA) tests is described to detect antibodies to Theileria mutans and Babesia major in the sera of infected cattle. When antisera against T mutans and B major were tested against homologous antigens high antibody titres were recorded: when they were tested against each other or against Babesia divergens antigen insignificant titres (1/40 or less) were recorded. Thus the test was found to be species specific. Animals recovered from T mutans and B major infections retained significant levels of IFA titres for 22 and 11 months respectively. It is suggested that the IFA test could be used for field survey of the piroplasms of cattle in Britain.