牛瑟氏泰勒虫病致病机理的研究进展

牛瑟氏泰勒虫病是由蜱传染的一种血液原虫病。近年来,随着养牛业的发展,牛瑟氏泰勒虫病的发生呈上升趋势,尤其是引进牛和改良牛的发病率和致死率均较高,给养牛业带来了巨大的经济损失。本文对近年来牛瑟氏泰勒虫病的病原体、流行病学、病理学和致病作用等与此病的致病机理相关的方面的研究进展作一总结,以便广大兽医工作者对此病有更加深入的认识。     

Variation in cardiac markers and electrocardiographic alterations in young calves naturally infected with bovine tropical theileriosis

The present study was designed to assess the deleterious effects of bovine tropical theileriosis on the cardiovascular system and the consequent myocardial involvement in young calves. Myocardial effects in parasitic diseases are often neglected. Hemolytic anemia, associated secondary hypoxia, and vasculitis are cardinal features of bovine theileriosis. In the present study, electrocardiogram (ECG) alongside serum cardiac troponin I (cTnI) and creatinine phosphokinase-myocardial band (CPK-MB) concentrations were analyzed in infected, treated, and control groups of young calves. Non-significant alterations were noticed in ECG. However, certain signs like sinus tachycardia, first-degree AV block, atrial premature complex, left atrial hypertrophy, and right atrial hypertrophy were found on consistent basis in infected calves. A significant increase in the serum concentration levels of cTnI and CPK-MB was noticed in infected calves followed by significant fall in both these biomarkers post treatment. cTnI and CPK-MB can definitely be used as myocardial markers in theileriosis-affected animals.     

Tropical theileriosis in Bos taurus and Bos taurus cross Bos indicus calves: response to infection with graded doses of sporozoites of Theileria annulata.

This work extends basic knowledge of tropical theileriosis in taurine and crossbred cattle. Infection of Bos taurus and Bos taurus cross Bos indicus (Sahiwal) calves with graded doses of sporozoites of Theileria annulata (Hissar), an Indian stock of the parasite, showed the following to be dose dependent in both cattle types: the time to appearance and population size of macroschizonts, microschizonts and piroplasms, time and severity of pyrexia, anaemia manifested by erythrocyte counts and haematocrit. All infections were accompanied by a prompt and severe panleucopenia. This effect was dose related in both the taurine and the Sahiwal crossbred calves. Lymphocyte counts returned to preinfection levels in the blood of animals which recovered, but death from theileriosis was characteristically accompanied by a persistent and severe lymphocytopenia. Flow cytometry using monoclonal antibodies to bovine mononuclear cells was used to identify the lymphocyte subsets involved in lymphocytopenia. The outcome of infection was dose dependent in the crossbred calves but not in taurine calves. Although the results obtained did not differ qualitatively between the two cattle types, they provided some preliminary evidence for resistance to tropical theileriosis in Sahiwal crossbred calves.     

牛环形泰勒焦虫裂殖体胶冻细胞苗应用效果观察

河南省桐柏县是牛环形泰勒虫病流行的多发区,对养牛业危害十分严重,1985年该县从宁夏农林科学院畜牧兽医研究所引进“虫苗”2万头份,在区域试验的基础上在全县16个乡（镇）进行了大面积防疫注射,经年终统计表明：虫苗安全性100%,注苗15000头（其中有水牛45000头）,发病3头,发病率0.02%;未注苗36000头,发病2060头,发病率5.7%,实际有效保护率达99.98%,取得了明显的社会经济效益。     

Epidemiological aspects and economic impact of bovine theileriosis (East Coast fever) and its control: a preliminary assessment with special reference to Kibaha district, Tanzania

A cross-sectional study based on clinical examination, inspection of herd health records and a questionnaire was designed to determine the epidemiology, economics and potential impact of immunisation against theileriosis in Tanzania. The results showed annual theileriosis costs to be US$ 205.40 per head, whereas the introduction of immunisation reduced this by 40-68% depending on the post immunisation dipping strategy adopted. Morbidity risk due to theileriosis was 0.048 in immunised and 0.235 in non-immunised cattle, and the difference was significant (chi(2)=66.7; P=0.000). The questionnaire results indicated that immunised cattle had a significantly (chi(2)=6; P=0.015) higher risk of anaplasmosis compared with non-immunised cattle, whereas the risk of bovine babesiosis did not differ significantly (chi(2)=0.06; P=0.807) between the two groups. Mortality risk due to anaplasmosis was 0.046 in immunised and 0.018 in non-immunised cattle and this difference was statistically significant (chi(2)=4.48; P=0.043). The theileriosis mortality risk was 0.203 in the non-immunised cattle, while the risk was 0.009 in the immunised cattle and these differences were also significant (chi(2)=103; P=0.000). It was concluded that farmers who have immunised their cattle may cautiously cut down acaricide application by 50% for extensively grazed herds and by 75% for zero grazed animals depending on the level of tick challenge at the herd level.     

A study about tick vectors of bovine theileriosis in an endemic region of Iran

The aim of this study was to determine the population of ticks in infected cattle and to identify the tick vectors of bovine theileriosis in an endemic area of Iran from 1998 to 1999. A total of 120 suspected cattle suffering from theileriosis were clinically examined and investigated for the presence of Theileria annulata in blood smears and the presence of any tick species on the body of cattle. In this study, 680 ticks were collected from 107 cattle infected with T. annulata. The prevalence of ticks infesting cattle was 92.35% Hyalomma anatolicum excavatum, 5.14% H. marginatum marginatum, 1.17% H. asiaticum asiaticum and 1.32% Rhipicephalus sanguineus. The examination of 510 tick salivary glands revealed that 51% of H. a. excavatum and 1.3% of H. a. asiaticum were infected with sporozoites of T. annulata.     

Cell-mediated immune responses to sporozoites and macroschizonts of Theileria annulata.

The nature of cell-mediated immune (CMI) responses was studied in cross-bred bovine calves, immunised by attenuated and allogeneic macroschizonts of Theileria annulata. The CMI responses were also investigated in calves, destined to survive or die of tropical theileriosis (Theileria annulata) induced by a virulent dose of sporozoites or macroschizont-infected lymphoblasts. Calves suffering fatal theileriosis showed poor CMI response. Microcytotoxicity assay revealed an enhanced population of specific cytotoxic cells amongst the peripheral blood lymphocytes (PBL) of calves resolving the infection successfully. The E rosette assay showed proliferation of T cells and the assay for macrophage migration inhibition factor (MIF) demonstrated antigen sensitised cells in the PBL. Calves, immunised by allogeneic and attenuated macroschizont-infected lymphoblasts or those recovering from virulent macroschizont-induced infection, showed protective CMI responses with patterns similar to those appearing after non-fatal sporozoite infection.     

Haemaphysalis qinghaiensis ticks transmit at least two different Theileria species: one is infective to yaks,one is infective to sheep

Adult Haemaphysalis qinghaiensis ticks from Gannan area, where ovine theileriosis is prevalent but bovine theileriosis has not been reported, transmitted Theileria parasites to yaks and sheep. Blood from the infected yak contained Theileria parasites that were infective to yaks, but not sheep. In contrast, blood from the infected sheep did not contain Theileria parasites infective to yaks. These results suggested that the ticks from the Gannan area were infected with two species of Theileria one which specifically parasitises yaks, one which parasitises sheep. Both infections were more aggressive in splenectomised hosts as compared to intact host. Adult H. qinghaiensis ticks from Zhanjiachuan area, where ovine theileriosis is prevalent but where no yaks are raised, transmitted Theileria parasites to ovine, but not yaks. Taken together these results indicate that H. qinghaiensis ticks may be infected with two different Theileria species. The species infective for sheep could be related to the newly recognised, but not yet named, pathogen recently reported in small ruminants in China. The species infective for yaks appears to be benign and is morphologically similar to parasites of the Theileria sergenti/orientalis/buffeli group.     

Diagnostic value of rectal temperature of African cattle of variable coat colour infected with trypanosomes and tick-borne infections

Diagnosis of major endemic bovine parasitic diseases in sub-Saharan Africa such as trypanosomosis, theileriosis, anaplasmosis, babesiosis and cowdriosis is increasingly relying on clinical diagnosis due to deterioration of veterinary services and laboratory facilities. Pyrexia is a common clinical feature of aforementioned diseases whose detection relies on measurement of rectal temperature. The research undertaken in this study was aimed at assessing the effects of diurnal changes and variable coat colour of indigenous Nkedi Zebu cattle on the diagnostic value of rectal temperature under tropical conditions. The results revealed that variation in rectal temperature was significantly influenced by time of day it was taken and by the coat colour of the Nkedi Zebu cattle (P < 0.001). Rectal temperature experienced diurnal changes: steadily rising to reach a peak at 17.00 h before declining. The mean rectal temperature of unhealthy cattle was significantly higher (P < 0.05) than that of the healthy ones only between 13.00 and 17.00 h of the day. During which period the proportion of unhealthy cattle having a rectal temperature of 39.4 °C or higher was significantly higher than that of healthy ones (P < 0.001). Regarding the variable coat colour of indigenous breeds, rectal temperature among cattle of different coat colours was significantly different (P < 0.05). In conclusion it is important to consider diurnal changes in rectal temperature and differences due to variable coat colour of indigenous African breeds when measuring rectal temperature for assessing pyrexia, during clinical diagnosis of bovine trypanosomosis and tick-borne diseases that are endemic in many countries in sub-Saharan Africa.     

我国羊泰勒虫病及其基因工程疫苗研究进展

羊泰勒虫病是由羊的泰勒虫引起的绵羊和山羊的一种蜱传性血液原虫病.疫苗预防是控制和根除羊泰勒虫病的一种最安全、有效的方法.然而我国目前还没有任何预防羊泰勒虫的疫苗,疫苗的研制还处于抗原基因筛选阶段.论文就目前羊泰勒虫病及其基因工程疫苗的研究进展进行综述,并对其未来的发展趋势进行展望.     

Presence of Theileria annulata in Mauritania

A fatal case of bovine theileriosis by Theileria annulata is reported from Mauritania in a Friesian cow born in a dairy farm in Nouakchott. The farm was originally established with cattle imported from France. Specific diagnosis was based on piroplasm morphology and on high specific antibody titres in some of the animals. The only tick found in the herd was Hyalomma dromedarii. Four of 49 local zebus sampled at random in the south of the country had high specific antibody titres to T. annulata, while 14 had lower or doubtful titres. The infection therefore appears to be autochthonous.     

Progress in research on tick‐borne diseases: Theileriosis and heartwater

Summary

The rapid population growth in subsaharan Africa necessitates a great increase in animal production in the more humid zones. Vector‐borne diseases occurring in these zones will assume more importance, but are difficult to control. They include theileriosis and heartwater. Recent developments in research on these diseases are presented. Indigenous animal populations in endemic areas, subjected to natural selection, are far less susceptible than exotic stock.

Heartwater, caused by the rickettsia Cowdria ruminantium, transmitted by Amblyomma ticks, causes high mortality in exotic ruminants. It has received much attention in recent years, partly because the disease has been introduced from Africa into the Caribbean and threatens the American mainland. Since the recent success of in vitro culture, much progress in research has been made, but so far prevention still relies mainly on acaricidal tick control; an infection and treatment method is used on a limited scale. Antigenic diversity is a complication for immunization procedures.

Theileria parva (East Coast fever, Corridor disease and January disease) and T.annulata (Mediterranean or tropical theileriosis) are the most pathogenic of the 6 species of this protozoan genus that infect cattle. Great progress has been made in recent years in knowledge on the immunology, the epidemiology, the taxonomy and the chemotherapy of theileriosis. Intensive acaricidal tick control can now be supplemented by an attenuated schizont vaccine against T.annulata, while immunization against East Coast fever is carried out on a limited scale using virulent sporozoite infection and treatment. Research on recombinant vaccines is promising. Antigenic diversity in T.parva is a serious complication.     

Tick-borne parasitic diseases in cattle: current knowledge and prospective risk analysis related to the ongoing evolution in French cattle farming systems

Parasitic diseases, like babesiosis and theileriosis are transmitted by ticks: their occurrence is therefore linked to the size of the tick stock and the seasonality of the vectors. Babesia divergens bovine babesiosis transmitted by Ixodes ricinus is widespread and often reported in France. Serological prevalence is high, ranging from 20 to 80% according to the farms. Clinical incidence is low: around 0.4% for the whole cattle population. The endemic situation is unstable and clinical cases occur more frequently with farming system modifications. L. ricinus is a tick essentially found in woodlands and so, for the most part, is found in closed rural areas. The situation of the other bovine babesiosis (Babesia major) and theileriosis (Theileria orientalis) is not well documented in France. However, the epidemiology of parasitic diseases is changing, especially because of changes in the environmental characteristics, i.e. both farm and herd management conditions and also climatic conditions. These modifications can provoke an increase in the tick stocks, an increase in the contact rate between cattle and ticks, and an increase in the contact rate between cattle and the wild fauna, especially deer. This results in likely modifications of the endemic situation, with a higher risk of clinical babesiosis in the medium term.     

Four p67 alleles identified in South African Theileria parva field samples

Previous studies characterizing the Theileria parva p67 gene in East Africa revealed two alleles. Cattle-derived isolates associated with East Coast fever (ECF) have a 129 bp deletion in the central region of the p67 gene (allele 1), compared to buffalo-derived isolates with no deletion (allele 2). In South Africa, Corridor disease outbreaks occur if there is contact between infected buffalo and susceptible cattle in the presence of vector ticks. Although ECF was introduced into South Africa in the early 20th century, it has been eradicated and it is thought that there has been no cattle to cattle transmission of T. parva since. The variable region of the p67 gene was amplified and the gene sequences analyzed to characterize South African T. parva parasites that occur in buffalo, in cattle from farms where Corridor disease outbreaks were diagnosed and in experimentally infected cattle. Four p67 alleles were identified, including alleles 1 and 2 previously detected in East African cattle and buffalo, respectively, as well as two novel alleles, one with a different 174 bp deletion (allele 3), the other with a similar sequence to allele 3 but with no deletion (allele 4). Sequence variants of allele 1 were obtained from field samples originating from both cattle and buffalo. Allele 1 was also obtained from a bovine that tested T. parva positive from a farm near Ladysmith in the KwaZulu-Natal Province. East Coast fever was not diagnosed on this farm, but the p67 sequence was identical to that of T. parva Muguga, an isolate that causes ECF in Kenya. Variants of allele 2 were obtained from all T. parva samples from both buffalo and cattle, except Lad 10 and Zam 5. Phylogenetic analysis revealed that alleles 3 and 4 are monophyletic and diverged early from the other alleles. These novel alleles were not identified from South African field samples collected from cattle; however allele 3, with a p67 sequence identical to those obtained in South African field samples from buffalo, was obtained from a Zambian field isolate of a naturally infected bovine diagnosed with ECF. The p67 genetic profiles appear to be more complex than previously thought and cannot be used to distinguish between cattle- and buffalo-derived T. parva isolates in South Africa. The significance of the different p67 alleles, particularly the novel variants, in the epidemiology of theileriosis in South Africa still needs to be determined.     

Infectivity of ground-up tick supernates prepared from Theilerai annulata infected Hyalomma anatolicum anatolicum.

Groups of Theileria annulata infected Hyalomma anatolicum anatolicum adults prefed on a calf for 1 to 6 days were separately ground in tissue culture medium-199, supplemented with bovine albumin powder, Fraction-V. Supernatant fluid was collected, made up with additional medium, so that each millilitre represented material from 25 ticks, and was injected subcutaneously into groups of cross-bred male calves. The results indicated that ground-up tick supernate (GUTS) prepared from unfed ticks was not infective, whereas that prepared from 1 to 6 days prefed ticks was infective. GUTS prepared from 3 days prefed ticks appeared to contain highest infectivity and 1 ml of it induced fatal theileriosis.     

Quantitative analysis of pro-inflammatory cytokine mRNA expression in Theileria annulata-infected cell lines derived from resistant and susceptible cattle

The pathogenic mechanisms involved in tropical theileriosis, caused by the tick-borne protozoan parasite Theileria annulata, are unclear. Pathology is associated with the schizont stage of the parasite, which resides within bovine macrophages. Breed-specific differences in pathology have been observed in cattle, several Bos indicus breeds are relatively resistant to tropical theileriosis whilst Bos taurus cattle are highly susceptible. Infected cells express pro-inflammatory cytokines and it has been hypothesized that these cytokines play a major role in the pathology of the disease. Therefore, using quantitative RT-PCR we investigated the expression of the key candidates, interleukin 1 beta (IL-1beta), IL-6 and tumour necrosis factor alpha (TNF-alpha), in T. annulata low passage infected cell lines derived ex vivo from experimental infection of resistant and susceptible cattle. mRNA for each cytokine was detected in all cell lines investigated at levels higher than those observed in resting monocytes. However, the analyses did not identify any breed-specific differences. Therefore, these results are not consistent with the hypothesis that differential regulation of infected cell derived pro-inflammatory cytokines (IL-1beta, IL-6 and TNF-alpha) accounts for the breed-related differences in resistance and susceptibility to T. annulata infection. Other, currently unknown mechanisms may be of greater importance.     

Molecular Analysis and Risk Factors Associated With Theileria equi Infection in Domestic Donkeys and Mules of Punjab,Pakistan

Theileriosis is an important disease of economic significance which badly affects the equine husbandry of developing countries. The present study was planned to investigate the molecular prevalence of theileriosis, associated risk factors, and alterations in hematological parameters of donkeys and mules from district Mianwali, Punjab, Pakistan. Blood samples from 150 equids (n = 75 donkeys; n = 75 mules) were examined microscopically, and the genomic DNA from each sample was processed for the amplification of the 18S rRNA gene of Theileria. The polymerase chain reaction confirmed isolates were purified followed by sequencing. The data regarding the analysis of risk factors were collected in a predesigned questionnaire and statistically analyzed by logistic regression analysis. An overall prevalence of 17.33% was noted in this study. Donkeys showed more prevalence followed by mules being 20.0% and 14.7%, respectively. The study isolates showed high resemblance (99%) with isolates from the United States of America, Spain, Brazil, Israel, Cuba, France, South Africa, Korea, Turkey, Tunisia, India, E. Caribbean, and Nigeria. The potential risk factors found to be significantly associated (P < .05) with disease dynamics were tick infestation on study animals, previous tick history, and house hygiene. A significant (P < .05) decrease in the number of platelets, erythrocytes, hemoglobin level, and packed cell volume was observed in donkeys and mules suffering from theileriosis compared with the healthy ones. The study is the first report regarding the molecular characterization of theileriosis in donkeys and mules in Pakistan. The findings will be effectual in designing effective control strategies for this disease in Punjab, Pakistan.     

Acquired methemoglobinemia in anemic cattle infected with Theileria sergenti.

To investigate the mechanism of anemia accompanying Japanese bovine theileriosis, we examined whether production of methemoglobin (MetHB), an indicator of erythrocyte oxidation, was associated with anemia in cattle experimentally infected with Theileria sergenti. The percentage of MetHB, which is an oxidized form of hemoglobin, increased according to the onset of anemia. During severe anemia, high levels of acquired methemoglobinemia were observed in all infected cattle. A significant correlation (r=-0.649; P<0.01) between an increase in MetHB concentration and a decrease in packed cell volume (PCV) was observed. It was considered that hemoglobin oxidation may be one of the aggravating factors of anemia in T. sergenti infection.     

Evaluation of antioxidant status and oxidative stress in cattle naturally infected with Theileria annulata

To assess the antioxidant status and oxidative stress in bovine theileriosis due to Theileria annulata blood samples were collected from 35 clinically affected cattle referred to Veterinary Teaching Hospital, School of Veterinary Medicine, Urmia University, Urmia, Iran. Complete blood count, piroplasm parasitemia percentage, erythrocyte glutathione peroxidase, superoxide dismutase, catalase and glucose-6-phosphate dehydrogenase activities, malondialdehyde concentration, osmotic fragility test and median corpuscular fragility were determined and the results were compared with those of 50 healthy controls. Of 35 affected cattle, 12 (34.28%) had severe anemia and 23 had mild to moderate anemia and parasitemia varied from 5 to 40%. The activities of erythrocyte glutathione peroxidase, superoxide dismutase and glucose-6-phosphate dehydrogenase were significantly lower (P<0.0001) and the activity of catalase was significantly higher in the affected cattle than in healthy ones (P<0.001). Malondialdehyde concentration in erythrocytes of affected cattle was significantly more than those of healthy cattle (P<0.001). The affected cattle showed increased fragility of erythrocytes, so that median corpuscular fragility (MCF) in affected group was significantly lower than those of healthy group (P<0.0001). Median corpuscular fragility showed a positive correlation with the severity of parasitemia (r=0.81, P<0.0005) and a negative correlation with the activities of GSH-Px (r=-0.78, P<0.0001), SOD (r=-0.71, P<0.0005), catalase (r=-0.53, P<0.018) and G6PD (r=-0.58, P<0.0005). The results of this study suggest that oxidative damage to RBCs may contribute to the pathogenesis of anemia in bovine theileriosis.     

Occurrence of Theileria parva infection in cattle on a farm in the Ladysmith district, KwaZulu-Natal, South Africa

Theileria parva causes widespread morbidity and mortality in cattle in endemic regions. An outbreak of theileriosis occurred on a farm near Ladysmith in KwaZulu-Natal, South Africa, which is not a declared Corridor disease-infected area. A survey of Red Brangus cattle from all age groups and areas of the farm was performed. Transmission of the parasite from infected animals on the farm to susceptible animals by tick transmission and tick-stabilate injection, was attempted. The survey indicated high numbers of animals with antibody titres to T. parva but only 6 infected animals, based on real-time PCR and RLB analysis. The transmission experiments failed to transmit the parasite. The study shows the difficulty in elucidating a source of infection and determining the dynamics of new infections in a herd where multiple possible sources are present and treatment with tetracyclines has taken place.