A simple procedure for the extraction of trypanosome DNA and host protein from dried blood meal residues of haematophagous diptera

A two step elution method is described for the extraction of host serum proteins and trypanosome DNA from a single dried insect gut smear preparation. The first low temperature elution yields material suitable for use in ELISA to determine the host species on which the fly last fed while the results of the second, high temperature, elution can be used in a PCR assay to detect the presence of trypansosomal DNA. The method can be used to extract material from both fly squashes and blood spots dried onto filter paper and could simplify the collection and processing of samples for epidemiological studies on trypanosomoses and other vector borne pathogens.

Electrophoretic and antigenic characterisation of Dermatophilus congolensis extracellular products

Dermatophilus congolensis is the causative agent of bovine dermatophilosis and lumpy wool in sheep. Two field isolates of D. congolensis, one each from a cow in Ghana and a sheep in Scotland, were cultured for 24-72 h in a synthetic medium based on RPMI-1640. Culture filtrates were examined by SDS-PAGE and considered to contain extracellular products released by growing hyphae and filaments. Electrophoretic profiles of culture filtrates of the two isolates contained common bands and bands that were unique to each isolate. The composition of extracellular products altered with increasing culture periods indicating that specific products were released at different stages of growth. Culture filtrate prepared in the presence of serine protease and metalloprotease inhibitors contained more and better defined bands than that prepared without protease inhibitors indicating the presence of proteases in culture filtrates. Western blot analysis of extracellular products using a panel of sera showed that the two isolates from different host species and distant geographical locations contained cross-reactive antigens. Natural and experimental infections stimulated antibody responses to antigens in culture filtrates, sera from animals that were disease free but in-contact with dermatophilosis-infected animals also contained antibodies to extracellular antigens. The antigens recognised by most sera had molecular weights of 200 kDa in the bovine isolate, 170 kDa in the ovine isolate and 67, 27 and 52-55 kDa in both isolates. The number of antigenic bands of both isolates was positively correlated with the intensity of challenge and the severity of infection: antibodies in sera from disease-free cattle in Ghana recognised more antigens than sera from disease-free sheep in Scotland and more antigens were recognised by sera from chronically-infected Ghanaian cattle than by sera from experimentally-infected calves and sheep. The latter developed antibodies to antigens of 27 and 24 kDa during the course of infection. The electrophoretic profiles of extracellular products of D. congolensis are less complex than those of other structures of the bacterium yet they exhibit differences between the two isolates. Extracellular products contain antigens recognised by sera from naturally exposed and experimentally-infected animals that may be involved in immunity to D. congolensis or immunopathogenesis of dermatophilosis.

Protective immune responses to Theileria annulata of relevance to vaccine development

A series of projects on Theileria annulata funded by the European Union (STD1/STD2/STD3) have provided convincing evidence that macrophage and natural killer (NK) cell-dependent immune mechanisms may directly control the proliferation of different stages of T. annulata in cattle. The evidence for this conclusion and the implications for vaccine development are discussed in the following paper.

Trypanosomosis research at the Centre for Tropical Veterinary Medicine (CTVM) 1970 to 1995

This review covers aspects of research work carried out on animal trypanosomes at the Centre for Tropical Veterinary Medicine (CTVM) during the last 25 years. The review covers work on antigenic variation, tissue culture, drug resistance, immunology, biochemistry and pathology of Trypanosoma brucei, T. congolense, T. gambiense and T. evansi. It is not intended as an exhaustive review of the subject but focuses on certain aspects of these areas which are presented in relation to work carried out within the broader scientific community.

Differences in cloning and sub-cloning success rates in four stocks of Trypanosoma evansi and variation in suramin resistance of the clones

Four Trypanosoma evansi stocks with sensitivity to suramin in mice ranging from 0.05 to 160 mg kg-1 were cloned and sub-cloned and the sensitivity of the clones determined. The results suggest that it is easier to clone and sub-clone trypanosome stocks which are sensitive to suramin than those that are resistant to the action of the drug. The clones obtained from the four stocks had sensitivities to suramin which were similar to or different from the parent stocks. These results are important in view of the development of resistance for, in the presence of suramin, these resistant yet heterogeneous populations would provide the material from which selective processes could operate. These observations also suggest that the maintenance and spread of suramin-resistant trypanosomes might be curtailed by their comparative inability to establish themselves in a new host.

Characterization of Lawsonia intracellularis gen. nov., sp. nov., the obligately intracellular bacterium of porcine proliferative enteropathy

A novel obligately intracellular bacterium, ileal symbiont intracellularis, which was obtained from the intestines of pigs with proliferative enteropathy disease, was grown in pure cocultures with tissue cultures of rat cells. An examination of the 16S ribosomal DNA gene sequence revealed that the isolates which we obtained are members of the delta subdivision of the Proteobacteria and that the sequences of these organisms exhibit a level of similarly of 91% with the sequence of Desulfovibrio desulfuricans ATCC 27774. These isolates were homogeneous and differed in cellular morphology, acid fastness, phenotype, electrophoretic protein profile, and habitat from Desulfovibrio species. On the basis of the results of an integrated study of the phenotype and genotype of a consistent morphological entity found in particular porcine cells and associated with a well-defined clinical condition, we concluded that these bacteria belong to a previously undescribed genus and species, for which we propose the name Lawsonia intracellularis gen. nov., sp. nov. A species-specific recombinant DNA probe was cloned previously, and this probe was used to identify the bacterium in tissue culture cells and in the ileal epithelia of pigs with proliferative enteropathy disease. Coculture of the organism with a rat enterocyte cell line allowed us to designate strain NCTC 12656 the type strain and to describe the new genus and species. The organism which we cultured is pathogenic for pigs and causes proliferative enteropathy lesions in their ilea and colons, and Koch's postulates were fulfilled for this organism.

Efficacy of Cymelarsan in Friesian Holstein calves infected with Trypanosoma evansi

Two studies on the efficacy of mel Cy (Cymelarsan, Rhone Merieux, France) for the treatment of cattle infected with Trypanosoma evansi were carried out with groups of 5 Friesian Holstein calves infected with an Indonesian stock of T. evansi and treated 14 days after infection. In the first study 3 groups were injected subcutaneously with Cymelarsan at dose rates of 0.125, 0.25 and 0.50 mg/kg and in the second study 2 i/m at 0.50 and 0.75 mg/kg. The response to treatment was monitored parasitologically by daily microhaematocrit centrifugation technique and weekly mouse inoculation. Enzyme linked immunosorbent assays were used to monitor trypanosomal antibodies and trypanosomal antigens in serum samples collected weekly. Relapse infections occurred in all the groups given the drug s/c whilst all the animals treated i/m remained parasitologically negative up to 80 days after treatment. Results from serological assays, however, suggested the possible persistence of trypanosome infection in the animals treated at a dose rate of 0.50 mg/kg i/m although trypanosomes could not be demonstrated parasitologically. A dose rate of 0.75 mg/kg administered i/m is recommended, therefore, for the treatment of T. evansi infection in Friesian Holstein cattle.

Experimental induction of suramin-resistance in cloned and uncloned stocks of Trypanosoma evansi using immunosuppressed and immunocompetent mice

Suramin-resistance was experimentally induced in cloned or uncloned T. evansi populations using both immunosuppressed and immunocompetent mice by administration of subcurative doses of the drug. The highest level of resistance achieved was 3,000 fold using cloned trypanosomes in immunosuppressed mice. In the absence of suramin, suramin-resistance in T. evansi was observed to be stable for ten passages in mice. The results obtained in this study imply that induction of suramin resistance is by a mutational event followed by selection of resistant mutants by the presence of the drug. Immunosuppression of animals by heavy parasite burden or stressful conditions in conjunction with underdosing may therefore play an important role in the development of drug resistance under field conditions.

Synthesis of tumour necrosis factor-alpha and interferons by mononuclear cells from Theileria annulata-infected cattle

Bovine macrophage-derived tumour necrosis factor-alpha/cachectin (TNF-alpha) was synthesized when peripheral blood mononuclear cells (PBMC) and purified adherent PBMC from naive and Theileria annulata-infected cattle were incubated in vitro with concanavalin A (Con-A) or bovine recombinant interferon gamma (Bo rIFN-gamma). TNF-alpha production was also induced when adherent PBMC were cultured with T. annulata macroschizont-infected cells. In contrast, non-adherent PBMC from sublethally infected cattle produced interferon (IFN) when incubated with Hu rIL-2, Con-A, phytohaemagglutinin (PHA) or T. annulata macroschizont-infected cells growing as cell lines in vitro. Whilst PBMC from lethally infected cattle spontaneously produced IFN-gamma during advanced stages of infection, the sera of such animals contained type 1 IFN (alpha/beta). IFN was also produced by T. annulata macroschizont-infected cell lines maintained in vitro. This work suggests that cytokines serve as crucial links between proliferating Theileira-infected cells and the characteristic clinical symptoms of tropical theileriosis.

Class-specific antibody response in rabbits experimentally infected with Trypanosoma evansi

The antibody response to Trypanosoma evansi antigens in rabbits experimentally infected with T. evansi was monitored by SDS-PAGE and "Western" blotting. As defined by the number of antigenic components recognised and the intensity with which they were labelled, responses were predominantly IgG, followed by IgM and IgA. During infection and subsequent drug treatment seven major antigenic components (94, 85, 75.5, 67, 60.5, 43, and 28.6 kDa) were identified by IgG. Antibodies to a 32.4 kDa and three other components (30, 28.6 and 12.5 kDa) appeared during infection and after chemotherapy respectively. Three components (94, 67 and 60.5 kDa) recognised by IgG were also detected by IgM and IgA. Furthermore, two bands (30 and 12.5 kDa) were identified by IgM and one (12.5 kDa) by IgA only after drug treatment, while a 28.6 kDa component was recognised by IgM and IgA during the same period. These findings constitute a basis for the exploration of class-specific antibody responses to T. evansi antigens with relevance to diagnosis, protection and pathology.

Antibody patterns in rabbits showing different levels of susceptibility to an experimental Trypanosoma evansi infection

Using SDS-PAGE and Western blotting, the antibody spectrum of rabbits infected with Trypanosoma evansi to homologous T. evansi antigens was monitored. Animals that developed parasitaemia later or had lower levels of parasitaemia as the infection progressed were considered to have a degree of resistance to the infection. Sera of these resistant animals recognised the T. evansi antigens earlier and subsequently identified more antigens than their susceptible counterparts. The susceptible animals developed patent parasitaemia earlier and had higher parasite counts as the infection progressed, and their sera recognised T. evansi antigens later with fewer parasite components labelled during the course of the infection. These observations demonstrate clear differences between animals in response to T. evansi infections. Selection of T. evansi-tolerant animals on an individual basis may be possible as has been suggested for other trypanosome species.

Some viral and protozool diseases in the European wildcat (Felis silvestris)

Ten European wildcats (Felis silvestris) were examined at necropsy and an additional 23 were examined clinically for evidence of viral diseases in Scotland. Two plasma samples taken from live free-living wildcats showed positive ELISA reactions to feline leukemia antigen. A feline leukemia virus of subgroup A was isolated from one of these samples, taken from a wildcat in north-western Scotland. No antibodies to feline coronavirus or feline immunodeficiency virus were detected in any sample. Three of the live wildcats and one of the dead had chronic mucopurulent rhinotracheitis suggestive of "cat flu." One other dead wildcat had diffuse enlargement of anterior lymph nodes. The findings indicated that feline leukemia virus infection can occur in free-living Felis silvestris. It is possible that the disease exists as a sustained infection in some wildcat populations, although the close interaction between wildcat and the domestic cat means that the latter could act as a continual source of infection.

Trypanosoma evansi infection in cattle, buffaloes and horses in Indonesia

Cattle, buffaloes and horses in several areas of Indonesia were examined for evidence of infection with Trypanosoma evansi by the microhaematocrit centrifugation technique (MHCT) and an enzyme-linked immunosorbent assay (ELISA) for detection of antibodies to T. evansi. Evidence of infection was found in animals at each sampling site although differences were seen in prevalence rates between sites. Prevalence rates in buffalo were usually higher than in cattle in the same area while in horses they were much lower than in cattle or buffalo. An age-dependent prevalence rate was seen in buffalo and cattle with the highest rates seen in animals older than 2 years. These results concur with the view that T. evansi infection is widespread throughout most of the livestock-producing areas of Indonesia. The apparent lack of any obvious disease owing to T. evansi infection in the sampled animals suggests that a form of stability exists in most endemic areas which serves to ameliorate the effect of T. evansi infection and has an immunological basis linked to the parasite's limited antigenic diversity.

Seroepidemiological studies of bovine babesiosis on Pemba Island, Tanzania

Serological evidence of infection with Babesia bovis and Babesia bigemina at a number of sites in Pemba was obtained using an enzyme-linked immunosorbent assay (ELISA) capable of detecting the appropriate parasite-specific antibody. Overall, 96% of animals were found to be positive for B. bovis, 88% were positive for B. bigemina and 88% were positive for both Babesia species. Antibody to B. bovis and B. bigemina was detected early in life in a number of calves born on Pemba, and was considered to be of maternal origin. The amount of maternal antibody in the serum of individual animals fell throughout the first 3 months of life. Later in life, antibody levels increased, probably in response to Babesia infection from natural tick challenge. These results suggest that infection with both Babesia parasites is widespread throughout Pemba and that both parasites probably exist in an enzootically stable situation.

DNA analysis of intracellular Campylobacter-like organisms associated with the porcine proliferative enteropathies: novel organism proposed

Intracellular Campylobacter-like organisms are a consistent feature of the porcine proliferative enteropathies. The relationship between these organisms and known Campylobacter sp. previously associated with the disease was studied using restriction enzyme analysis and DNA-DNA blot hybridization techniques. BglII restriction enzyme fragment patterns of DNA of the Campylobacter-like organisms were fundamentally different from those of C. mucosalis, C. hyointestnalis, C. jejuni, and C. coli. Crude DNA preparations from Campylobacter-like organisms hybridized strongly with homologous preparations, weakly with porcine DNA and not at all with DNA from Campylobacter sp. Fragment specific DNA probes prepared from Campylobacter-like organisms only hybridized with homologous preparations. This work suggests that the intracellular Campylobacter-like organisms are not one of the known Campylobacter sp. It is possible that they are a novel, uncultured organism worthy of a new name, such as HC. intracellulare'.

Malic enzyme type VII isoenzyme as an indicator of suramin resistance in Trypanosoma evansi

This study analysed the suramin sensitivity of 29 stocks of Trypanosoma evansi isolated from Egypt, Sudan, and Indonesia and compared the results with the isoenzyme banding patterns of 20 soluble enzymes in these stocks of T. evansi. The results showed that the type VII banding pattern of malic enzyme was found only in T. evansi stocks which were highly resistant to suramin.

Antigenic analysis of Campylobacter species and an intracellular Campylobacter-like organism associated with porcine proliferative enteropathies

Whole-cell and outer membrane preparations of Campylobacter mucosalis, C. hyointestinalis, C. jejuni, and C. coli isolated from porcine intestines were compared with preparations of intracellular Campylobacter-like organisms extracted directly from the lesions of pigs with proliferative enteropathy. By gradient polyacrylamide gel electrophoresis, outer membrane and total protein profiles of C. mucosalis, C. hyointestinalis, C. jejuni, and C. coli were significantly different from each other and from those of the Campylobacter-like organisms. Immunoblotting of these preparations with rabbit antisera or monoclonal antibodies prepared against the intracellular Campylobacter-like organisms showed strong reactions only with a 25,000- to 27,000-molecular-weight component of preparations of the intracellular organisms. Antisera to cultivable Campylobacter species isolates did not react with preparations of intracellular organisms. Isoelectric focusing of sonicated preparations showed protein profile differences and an immune-reactive component in the intracellular organisms with a pI of 4.5. This study suggests that the intracellular Campylobacter-like organism associated with proliferative enteropathy may be a novel bacterium with significant antigenic differences from the Campylobacter species previously associated with the disease.

Isoenzyme characterisation of 15 stocks of Trypanosoma evansi isolated from camels in the Sudan

Fifteen stocks of T. evansi isolated in Sudan were compared using isoenzyme banding patterns. Differences between the stocks were found but overall they formed a homogeneous group. The results were similar to those obtained for other stocks of T. evansiisolated from Kenya, W. Africa, S. America and Kuwait and indicate that little genetic variation occurs in T. evansi over its geographical range. This low variation may have important implications in the development of new methods of controlling trypanosomiasis caused by T. evansi.

Isolation and characterization of salivary antigens from Hyalomma anatolicum anatolicum

This study demonstrates the involvement of a large number of salivary proteins in the acquisition of resistance to Hyalomma anatolicum anatolicum. Using immunoblotting, sera from hypersensitized rabbits were shown to react with nine proteins in the saliva and 17 in salivary gland extracts (SGE) from 96 h fed female ticks. The salivary antigens had molecular weights in the range of 14 400 to 130 000. All the antigens identified in the saliva and 12 of the SGE antigens were glycoprotein in nature and a majority of them appeared to be common to different stages of feeding. In addition antigen I (molecular weight 130 000) showed acid phosphatase and antigen III (molecular weight 96 000) showed both non-specific esterase and aminopeptidase activity. Three high molecular weight proteins isolated from saliva (antigen I, antigen II--molecular weight 103 000 and antigen III), gave immediate hypersensitivity reactions in intradermal inoculation into rabbits which had previously been exposed to ticks. Antigens II and III also elicited a strong delayed hypersensitivity reaction. These results may help to explain the nature of the immune mechanisms which effect resistance against H. a. anatolicum.

Isoenzyme analysis of stocks of trypanosomes isolated from cattle in Indonesia

Three trypanosome stocks isolated from cattle in Indonesia were shown to differ markedly from an Indonesian stock of Trypanosoma evansi on the basis of the isoenzyme banding patterns of 12 soluble enzymes. The results obtained for these stocks were not consistent with those reported for typical forms of T evansi but were very similar to enzyme patterns obtained for rodent adapted stocks of T vivax.

Mechanism of formation of the A/B cis ring junction of ecdysteroids in Polypodium vulgare

1. The fates of the alpha-, 4 alpha- and 4 beta-hydrogen atoms of cholesterol during formation of the A/B cis ring junction of ecdysteroids was investigated by administration of [4-14C, 3 alpha-3H], [4-14C, 4 alpha-3H]- and [4-14C, 4 beta-3H]cholesterol species to the fern, Polypodium vulgare, and isolation of the 20-hydroxyecdysone formed in each case. 2. The 3H was retained in the ecdysteroid formed from each substrate. 3. Location of the 3H in the 20-hydroxyecdysone indicated that migration of 3H from the 3 alpha- and 4 beta-positions to C-4 and C-5, respectively, had occurred, whereas the 4 alpha-3H atom was retained at C-4. 4. A possible mechanism for the formation of the A/B cis ring junction of ecdysteroids in P. vulgare is presented.

Changes in the levels of some serum enzymes in dromedary camels infected with Trypanosoma evansi

The serum levels of sorbitol dehydrogenase, alkaline phosphatase, glutamic pyruvic transaminase and glutamic oxaloacetic transaminase in healthy male dromedary camels were determined. The camels were then infected with Trypanosoma evansi and the same enzymes determined at intervals, both during the period of infection and after treatment with the trypanocidal drugs suramin and quinapyramine sulphate. Increases in the serum levels of sorbitol dehydrogenase, glutamic pyruvic transaminase and glutamic oxaloacetic transaminase were recorded, together with a decrease in the serum level of alkaline phosphatase during the period of patent parasitaemia. The levels of the enzymes returned to normal after drug treatment.

Serodiagnosis of infection with Trypanosoma evansi in camels in the Sudan

Five diagnostic tests for infection with Trypanosoma evansi have been compared in groups of camels experimentally infected or exposed to natural infection in the Sudan. The correlation of positive results obtained by assays of IgM levels, the mercuric chloride test and the formol gel test with the presence of active infection was unsatisfactory, but there was a good correlation between results obtained using IFAT and ELISA and proven infection. Sera from a high proportion of apparently uninfected camels from endemic areas gave positive reactions with all 5 tests, possibly indicating inadequate parasitological diagnosis or persistence of antibody after unsatisfactory chemotherapy. It was concluded that serological tests using trypanosomal antigens to detect antibodies were more sensitive for diagnosis than indirect tests based on raised euglobulin levels. Serodiagnostic tests may therefore have a place in future programmes for surveillance and control of T. evansi infections in camels.