Phenotypic and genotypic alterations associated with the attenuation of a Theileria annulata vaccine cell line from Turkey

Attenuated vaccines, produced by prolonged in vitro culture of the macroschizont stage of the life-cycle, are the main method of controlling Theileria annulata infections. Little is known about the mechanism(s) of attenuation. Here we present data from a Turkish cell line demonstrating that attenuation is associated with reduced ability to differentiate into microschizonts and a reduction in matrix metalloproteinase activity. We also show that attenuation results in a change in the structure of the parasite population. Using the technique of differential mRNA display, we demonstrate that gene expression profiles differ between non-attenuated and attenuated macroschizont infected leucocytes. One differentially expressed gene is of parasite origin. These data are discussed in the context of a multifactorial model for virulence.

Cost analysis of immunisation against east coast fever on smallholder dairy farms in Kenya

A spreadsheet model was developed and used to estimate the total cost of immunising cattle against East Coast fever (ECF) based on the infection-and-treatment method. Using data from an immunisation trial carried out on 102 calves and yearlings on 64 farms in the Githunguri division, Kiambu district, Kenya, a reference base scenario of a mean herd of five animals, a 10% rate of reaction to immunisation and a 2-day interval monitoring regimen (a total of 10 farm visits) was simulated. Under these conditions, the mean cost of immunisation per animal was US$16.48 (Ksh 955.78); this was equivalent to US$82.39 (Ksh 4778.90) per five-animal farm. A commonly reported reactor rate of 3% would decrease the cost of US$14.63 (Ksh 848.29) per animal. Reducing the number of farm monitoring visits from 10 to 7 would reduce the total cost by 10%, justified if farmers are trained to undertake some of the monitoring work. The fixed costs were 53% of the total cost of immunisation per farm. The cost of immunisation decreased with increasing number of animals per farm, showing economies of scale.

Delayed type hypersensitivity theilerin test in cattle vaccinated against Theileria annulata infection

Theilerin was prepared and its total nitrogen was determined at level of 1 mg/ml. Seventy-two Holstein Friesian cattle recovered from acute theileriosis or vaccinated received 0.1 ml of theilerin intradermally at normal concentration of total nitrogen or other dilutions (1 / 10 and 1 / 100). Some 60(% of calves and 66.67% of milking cows receiving normal theilerin showed more than 1 mm increase in skin thickness at the site of inoculation (mean value of 1.86 mm for calves and 3.46 mm for milking cows). The pathological examination of the inoculation site showed infiltration of lymphocytes. No changes of general condition were observed in animals under study. The result indicated that the test is positive and could be used for checking Immunity in vaccinated animals.

Development of an experimental tissue culture vaccine against Mediterranean theileriosis in Spain

Vaccines against Mediterranean theileriosis have been developed in several countries where the disease is an economic problem. Tissue culture vaccines have been widely and successfully used to immunize cattle. Although Mediterranean theileriosis represents a constraint to dairy cattle production in Spain, no vaccines against this disease have been developed previously. The successful development of a tissue culture vaccine consisting of attenuated Theileria annulata schizont infected cells from an enzootic area of Spain and its efficacy under experimental conditions is reported. Vaccinated calves were resistant to homologous challenge showing no signs of theileriosis while non-vaccinated calves showed typical signs of disease.

Effect of different East Coast Fever control strategies on fertility, milk production and weight gain of Sanga cattle in the Central Province of Zambia

Five different East Coast Fever (ECF) (Theileria parva infection) control strategies, based on tick control and/or ECF immunization, were tested in groups of traditionally managed Sanga cattle in the Central Province of Zambia over a period of 2.5 years. Two groups were kept under intensive tick control (sprayed weekly), one group immunized and one non-immunized. Two further groups were under no tick control, one group immunized and one non-immunized, while a fifth group was immunized against ECF and maintained under strategic tick control (18 sprays per year). Tick control increased milk production and weight gain but not fertility. Immunization had neither marked detrimental nor beneficial effects on the cattle productivity. The combination of strategic tick control and immunization resulted in the highest level of production and at the same time reduced the potential risk from other tick-borne diseases.

Responses in animals vaccinated with the Theileria annulata (Hisar) cell culture vaccine

Bovine tropical theileriosis caused by Theileria annulata is an economically important disease of cattle in India. The disease has assumed paramount importance with the intensification of cross-breeding programmes aimed at enhancing milk production in the country. To control this disease, a cell culture vaccine was developed in this department by continuous passaging of T. annulata (Hisar) schizonts in vitro. Current work in this department has concentrated on the epidemiology of theileriosis: development of the cell culture vaccine for very young calves and pregnant cows; evaluation of serological responses using immunofluorescent antibody (IFA) tests and Enzyme-linked immunosorbent antibody assays (ELISA); studies on the duration of immunity stimulated by the cell culture vaccine; the immune/susceptible status of calves born to vaccinated dams. Results have shown the following. Clinical cases of theileriosis were mainly observed in young calves below two months of age followed by adults in exotic and cross-bred animals. Amongst indigenous animals, only young calves below two months of age suffered from clinical disease. Clinical cases of theileriosis mainly occurred between the months of April to October. The T. annulata schizont cell culture vaccine developed in the department was extensively used in the susceptible calves and pregnant/lactating cows in the field. Sufficiently high antibody titres were detected by both schizont as well as piroplasm antigen using both ELISA and IFAT. The results indicated that the vaccine was safe, potent and effective for all breeds and age groups of cattle under field conditions. ELISA was standardised for T. annulata using three antigens, viz.: soluble piroplasm, soluble schizont and cellular schizont antigens. Comparison of results with IFAT showed that ELISA is more sensitive, objective, reliable and specific as well as less cumbersome than IFAT. Piroplasm, cellular schizont and soluble schizont antigens were found to be suitable for the detection of antitheilerial antibodies as per their order in ELISA. Studies on the duration of immunity stimulated by the T. annulata schizont cell culture vaccine indicated that immunity started waning after six months. Calves born of dams immunised against T. annulata with the cell culture vaccine were found to be fully susceptible to theileriosis soon after birth. This indicated that there was no passive transfer of immunity from dams to their offspring through colostrum.

Cattle theileriosis in China

Amongst the piroplasmoses of livestock in China, the commonest theilerioses are caused by Theileria annulata, T. sergenti and T. mutans. Research carried out over many years has shown these to be distributed mainly in Northern China but they also occur in Southern China. T. annulata and T. sergenti are the most troublesome, affecting large numbers of cattle, especially those of exotic breeds. The incident rate and numbers of fatalities vary widely between areas and breeds of cattle. T. annulata is the most virulent species having an incident rate of 11-46% for indigeneous cattle and causing death rates of between 11-40.8%. For exotic cattle in areas free of T. annulata the sickness rate is up to 61% and mortality rates up to 31%. T. sergenti is avirulent in cattle and clinical symptoms are rarely observed, however, in some areas the infection rate could possibly be as high as 97.5%. Dairy and hybrid cattle imported from other places proved highly susceptible, with mortality rates possibly reaching 14%. The pathogenic forms, clinical signs, tick vectors and the effects of chemical and immune intervention are also discussed in this paper.

Vaccines against hemoparasitic diseases in Israel with special reference to quality assurance

Four vaccines against hemoparasitic diseases (anaplasmosis, babesiosis and theileriosis) and a vaccine against besnoitiosis are currently used in Israel. These vaccines contain live attenuated parasites derived from cell culture (Theileria annulata and Besnoitia besnoiti) or from blood of infected, splenectomized calves (Babesia bigemina, B. bovis and Anaplasma centrale). Cryopreserved master seed is used to initiate production of the vaccines. Quality control performed during the preproduction period is particularly important with blood-derived vaccines. Post production quality control comprises sterility, potency (viability of immunizing organisms), safety (degree of attenuation) and efficacy (capacity to protect against virulent parasite stock). All vaccines are stored and dispatched to the field in a concentrated frozen state. The culture-derived vaccines are safe for all varieties of cattle, regardless of age or physiological condition, whereas the blood-derived vaccines are recommended mainly for young cattle, the age limit varying with the type of vaccine and breed of cattle. The viability of T. annulata infected cells in the anti-theilerial vaccine is tested after thawing by in vitro plating efficiency and the infectivity of blood-derived vaccines is tested by titration in susceptible cattle.

Induction of protective immunity to Theileria annulata using two major merozoite surface antigens presented by different delivery systems

Allelic forms (Tams1-1 and Tams1-2) of the major merozoite surface antigen gene of Theileria annulata have recently been expressed in Escherichia coli and in Salmonella typhimurium aroA vaccine strain SL3261. To test the potential of subunit vaccines against T. annulata infection, we immunized four groups of three calves with either recombinant (re-) (Tams1-1 and Tams1-2) proteins or naked DNA encoding these antigens. Group I was immunized intramuscularly with both re-proteins incorporated into immunostimulating complexes (ISCOMs). Group II was inoculated intramuscularly with naked plasmid DNA encoding Tams1-1 and Tams1-2. Groups III and IV received S. typhimurium SL3261 [pSTams1-1][pIP5] and SL3261 [pSTams1-2] [pIP5] subcutaneously and orally, respectively. A final group of three animals (Group V) served as an unimmunized control group. Four weeks after the last immunization all calves were challenged with a T. annulata stabilate generated from blood of an infected animal with 30% piroplasm parasitaemia. All calves vaccinated with ISCOMs proved to be protected from T. annulata infection and had generated antibodies against both re-(Tams1-1 and Tams1-2) at the time of challenge. In two of these animals the antibody had a surface binding profile by IFAT. Two of three calves immunized with naked DNA also proved to be protected, but none of the animals had generated any detectable antibodies against the recombinants. Salmonella-based delivery of the recombinants did not induce any protection; two of six animals died of theileriosis and there was no difference between subcutaneous or oral administration. These preliminary results show that re-(Tams1-1 and/or Tams1-2) may elicit protective immune responses in cattle, depending on the antigen delivery system.

Lowered vaccine dose for immunisation of calves against tropical theileriosis using Theileria annulata lymphoblasts

Bovine tropical theileriosis is of high incidence in calves below 2 months old in India. The Theileria cell culture vaccine evolved by the Punjab Agricultural University (PAU) was evaluated previously for its efficiency and safety in younger calves, both experimentally and in the field. The dose of cells used for vaccination was regulated at 1.75 to 2 x 10(6) cells. This study, which was undertaken to assess the minimum number of cells which would be effective and safer for vaccination, showed that optimal protection was given by a dose of 1 x 10(6) cells.

Research on the schizont cell culture vaccine against Theileria annulata infection in Xinjiang, China

Theileria annulata infection (TAI) is one of the most serious diseases of cattle in Xinjiang Autonomous Region of Uigur Minority Nationality. It has been recorded in 14 prefectures, except the Tulufan Prefecture, but the enzootic areas are mainly distributed around the Zhunger Basin and Talim Basin. According to the records collected in the ten years before vaccination with the schizont cell culture vaccine was carried out, the average incidence rate of TAI in enzootic areas was 7.22% and the mortality rate was 24%. The milk production of cattle suffering from TAI was sharply decreased, and there were usually abortions in pregnant cows. The incidence rate and mortality rate were greater in high grade cattle, so TAI was a constraint to improving cattle breeds. To control this disease effectively in Xinjiang, researchers at the Xinjiang Academy of Animal Science began to study the schizont cell culture vaccine in 1972. In 1977 an immortalised cell line was achieved from a primary cell culture starting with white blood cells from cattle suffering from acute TAI caused by an artificial tick bite. The cell culture medium mainly consisted of calf serum, lactalbumin-hydrolysate, Eagles' medium DMEM and three antibiotics. As a vaccine, the above cells were mixed with preserving medium containing gelatin. This paper describes the experiments on the immunological properties of the vaccine carried out in subsequent years. Up to 1996, vaccine doses for 1,186,150 cattle have been produced and sold. This vaccine has had a critical effect on the control of TAI in Xinjiang. Owing to the sharp decrease in the incidence rate and mortality rate of TAI after cattle were vaccinated, the annual economic benefit of the vaccine is at least 1,620,000 yuan.

Theileriosis of sheep and goats in China

Theileriosis is an important disease of sheep and goats in West China. Its main distribution includes Qinghai, Gansu, Ningxia, Inner Mongolia, Shaanxi and Sichuan. The epidemic period is from late March to July with April-May being the peak months. This is the period of most intensive tick attack by Haemaphysalis qinghaiensis (77.2-99.24%) during the year. It has been proved that the nymphs and adults, which develop from larvae and nymphs engorged on infected sheep or goats can transmit the pathogen. Experimental infections revealed the incubation period, clinical signs and the pathogen's morphological characteristics. The disease was more serious in lambs and exotic adult animals than native adult animals. The sickness rates of lambs, exotic and native adult animals were 78-85%, 41% and 9% respectively; death rates were 81.41%, 62.5% and 65% respectively. Clinical prophylaxis, chemical therapy and destruction of ticks have been carried out with antiparasitic compounds to control the disease since 1982. Experiments demonstrated that the curative rate was up to 76-86%, but no satisfactory prophylactic methods were found.

Control of Theileria sergenti infection by vaccination

Bovine piroplasmosis caused by Theileria sergenti is a major cause of economic loss in grazing cattle in Japan. Infected calves show chronic anaemia with intraerythrocytic piroplasms and occasionally die in severe cases. We found that parasite stocks and isolates consist of genetically and antigenically mixed populations. To differentiate parasite populations bearing 3 allelic forms of p32/34, an immunodominant piroplasm surface protein, 3 sets of oligonucleotide primers were designed to amplify either of 3 alleles by polymerase chain reaction (PCR). By using this allele-specific PCR, we found that the majority of T. sergenti-infected calves in Japan harbored mixed parasite populations bearing C and I type parasites. To control Theileria infection, we produced 2 vaccine candidates: recombinant baculovirus p32 and synthetic peptide containing Lys-Glu-Lys (KEK) motif. Immunization with either recombinant p32 or synthetic peptide containing KEK sequences with Freund's complete adjuvant resulted in low parasitemia and reduced the clinical symptoms compared to control calves. Interestingly, the parasite with the p32 allelic form corresponding to the one used as the immunogen was suppressed.

A polymorphism observed in the experimentally successful peptide vaccine sequence derived from Theileria sergenti piroplasm major surface antigen (p33)

A polymorphism in the experimentally successful peptide vaccine sequence (EVVWKEKKEVKDLDA, amino acids 134-148) derived from the 33 kDa piroplasm major surface antigen (p33) of Theileria sergenti was examined. The vaccine sequences obtained by PCR amplification and sequencing of the p33 gene from a total of 15 parasite-infected cattle blood samples collected from 4 prefectures through Hokkaido to Kumamoto revealed the two major sequences (Ikeda and Chitose stock types) either of which was identified in all samples. Since the peptide vaccine develops the parasite species- or stock-specific immunity in the animals, an application of the two major peptide sequences as cocktailed vaccine should be evaluated for a practical use of this strategy to controlling T. sergenti infection in Japan.

Field trial of immunization with an experimental vaccine against Mediterranean theileriosis in Spain

Vaccines against Mediterranean theileriosis have been developed in several countries where this disease is of economic concern. Until recently, tissue culture vaccines were a suitable method for immunizing cattle and they have been widely applied with success. In Spain, Mediterranean theileriosis is an obstacle to the improvement of dairy cattle productivity. No vaccines against this disease have been applied until recently. This report concerns the field trial of an available experimental tissue culture vaccine consisting of attenuated Theileria annulata schizont infected cells from an enzootic area of Spain. The vaccinated cattle developed a typical post-vaccination immunological response and were resistent to a field challenge. They showed no clinical signs of theileriosis while 50% of the control cattle showed typical signs of the disease and two of them died (12.5% of control cattle). This vaccine may be useful to protect cattle against Mediterranean theileriosis in enzootic areas of Spain.

Allograft responses can interfere with the development of immunity against Theileria annulata following vaccination with parasite infected cell lines

Theileria annulata macroschizont-infected cell lines are successfully used as vaccines in several countries. The inoculated animals produce a strong allogeneic response against the MHC antigens of the immunizing cell line followed by an anti-parasite response. Immunity against the parasite wanes in the absence of challenge and re-immunization is sometimes recommended. However, it is not known if allogeneic responses generated by the first immunization with a T. annulata infected cell line will interfere with the boosting of immunity against the parasite at the time of re-immunization with the same cell line. Animals were primed against MHC antigens by skin grafting, followed by immunization with a T. annulata infected cell line prepared from the skin donor. A strong anti-MHC response was produced. This interfered with parasite transfer and the development of an anti-parasite immune response; the effect was more marked when a low vaccine cell dose was used. There was a negative correlation between the ease of isolating infected cells from the animals after cell line immunization, and the subsequent response to challenge. Where no cell lines could be isolated, the animals were fully susceptible to sporozoite challenge. These observations are of immediate importance in endemic areas where cell lines of T. annulata schizonts are being used as vaccines to control the disease.

Subunit vaccines for the control of tick-borne diseases: implications for the future

Tick-borne parasites are a major constraint to the improvement of livestock productivity in the developing world. These parasites include Theileria parva, T. annulata, Babesia bigemina, B. bovis, Anaplasma marginale and Cowdria ruminantium. The impact of these diseases is currently limited by the use of acaricides to decrease transmission by the tick vectors and immunization of the host animals using live vaccines. The use of acaricide is hampered by the development of acaricide resistance and live vaccines are dependent on cold chain facilities, which are generally unreliable in developing countries. There is therefore a requirement for improved vaccines that circumvent these problems. Candidate vaccine antigens have been identified for most of these parasites and are currently being evaluated for their capacity to induce solid protection.

Tick-borne diseases of sheep and goats and their related vectors in Iran

Haemoparasitic diseases have long been considered as a major problem to efficient sheep and goats production in Iran. Theileriosis due to Theileria hirci and babesiosis due to Babesia ovis and B. motasi are the most pathogenic protozoa. B. crassa, Anaplasma ovis and Eperythrozoon ovis are usually non-pathogenic and do not cause any apparent problem. The major tick genera found on sheep and goats are Hyalomma, Rhipicephalus, Haemaphysalis, Ixodes and rarely Dermacentor distributed in all part of Iran. Our studies indicate that only Hyalomma ticks transmit Theileria species but the others transmit Babesia, Anaplasma and Eperythrozoon. The two latter ones can also be transmitted through some biting flies and mechanical means. Control methods presently available in Iran rely almost entirely on: (i) vaccination of sheep and goats with cell culture vaccine for theileriosis; (ii) chemotherapeutic treatment for babesiosis and anaplasmosis; (iii) acaricides for control of tick vectors.

Conventional vaccines for tick-borne haemoparasitic diseases of sheep and goats

Of the many tick-borne haemoparasites of sheep and goats, three may be controlled by vaccination. A live virulent blood vaccine for Cowdria ruminantium infection (heartwater) is used widely in southern Africa in an infection and treatment procedure. A live vaccine for Babesia ovis attenuated by passage in splenectomised sheep has been used extensively in Bulgaria with good results. A live vaccine for Theileria hirci, consisting of schizonts propagated in a lymphoid cell culture and attenuated by passage, has been used successfully in the Middle East.

A general review on the prevention and treatment of Theileria annulata in China

A review is given of the prevention and treatment of Theileria annulata infection of cattle in China. Primaquine phosphate has been shown to be an effective drug for the elimination of gametocytes of T. annulata and an attenuated strain of virulent parasites is used as a vaccine. This vaccine has proved to be 100% safe and over 90% effective. Since the use of these two methods of control, the disease caused by T. annulata in cattle in China has been controlled.

Immunisation of cattle in Zimbabwe using Theileria parva (Boleni) without concurrent tetracycline therapy

Five hundred and ten cattle were immunised using the Theileria parva (Boleni) stock without concurrent chemotherapy with tetracycline on 2 farms in Zimbabwe, both of which had a history of theileriosis. The stabilate had been titrated in Friesian calves to determine a 50% protective dose (PD50) and 2 or 3 (PD50s) were used to immunise the cattle. None of the cattle showed a clinical reaction following the immunisation procedure. However, the cattle were shown to have responded immunologically on testing for antibodies to a T. parva antigen in an indirect fluorescent antibody test. The immunised cattle were then exposed to a natural field challenge causing severe theileriosis in control cattle. Immunisation against theileriosis without the need for concurrent chemotherapy is much less expensive than the infection and treatment method (US $2.72) compared to US $10.23 in the first year) and would be much more attractive to commercial and traditional farmers.

Integrated tick and tick-borne disease control trials in crossbred dairy cattle in Malawi

Crossbred dairy heifers on a farm in an East Coast fever (ECF) endemic area in Malawi were immunised against Theileria parva, Anaplasma spp., Babesia bigemina, Babesia bovis and Cowdria ruminantium. They were treated at infrequent intervals with chlorfenvinphos to limit infestation with adult ticks, without providing complete tick control. In one trial, which tested a threshold dipping regimen, 20 heifers were dipped only once in 6 months to control a flush of Boophilus microplus. Unimmunised controls showed serological evidence of exposure to T. parva and B. bigemina, and one died of ECF, but there were no incidents of tick-borne disease in the immunised group. In a second trial, which tested a strategic dipping regimen, 107 animals were dipped 9 times over a 6 month period. Despite heavy challenge by B. bovis and moderate challenge by B. bigemina and Anaplasma spp. demonstrated serologically, there was only a single clinical case of babesiosis. The observations provide encouragement for the introduction of integrated tick and tick-borne disease control programmes in improved cattle in ECF endemic areas.

Prospects for subunit vaccines against tick-borne diseases

Tick-borne parasites are a serious impediment to the improvement of live-stock production in the developing world. The major parasites affecting cattle include Theileria parva, T. annulata, Babesia bigemina, B. bovis, Anaplasma marginale and Cowdria ruminantium. The control of these infections is dependent on the use of acaricides to decrease transmission by the tick vectors, and immunization of susceptible animals with live vaccines. The use of acaricide is hampered by the development of resistance, and live vaccines require cold chain facilities, which are generally unreliable in developing countries. There is therefore a need for improved vaccines that can circumvent these problems. There is a subunit vaccine being developed for T. parva based on the major surface antigen of the sporozoite (p67). A similar antigen, SPAG 1, has been identified as a candidate for T. annulata. Although several candidate antigens have been identified for Babesia spp., progress towards development of a subunit vaccine based on these antigens has been hampered by polymorphism among isolates and between species, and lack of knowledge of the immune effector mechanisms responsible for protection. The search for protective antigens of A. marginale has focused on outer membrane proteins; immunization with a variety of these antigens alone or in combination, has yielded promising results. As with Babesia, further definition of immune effector mechanisms is needed to optimize immunization strategies. The work on identifying the protective antigens of C. ruminantium is in its embryonic stages; however, two antigens have been identified and are currently being evaluated. There is high expectancy for subunit vaccines for all these diseases; however there is need for further work to elucidate the immune mechanisms in order to select appropriate antigen delivery systems.

A preliminary study on the attenuation of Tunisian schizont-infected cell lines of Theileria annulata

Four Theileria annulata cell lines were characterised at low passage levels using two polymorphic markers and then used to infect calves. Their virulence seemed to be related to the number of genotypes present within the cell line. In all, 3 of the 4 cell lines were cultured up to passage 100 or 200 and inoculated into calves. Their characterisation using the same markers indicated that the attenuation was related to a reduction in the parasite polymorphism down to a single genotype. The immunogenicity of the three attenuated cell lines was assessed in calves using two types of challenge. Optimal protection was observed against homologous challenges. The level of immunity to heterologous challenges appeared to decrease with attenuation and seemed to depend on the cell line used.