In sub-Saharan Africa,limited studies have investigated zoonotic pathogens that may be harboured by ticks infesting reptiles such as tortoises.Here,we report the presence of pathogenic Rickettsia in ticks(Amblyomma ma...In sub-Saharan Africa,limited studies have investigated zoonotic pathogens that may be harboured by ticks infesting reptiles such as tortoises.Here,we report the presence of pathogenic Rickettsia in ticks(Amblyomma marmoreum)collected from the leopard tortoise(Geochelone pardalis)in rural Zambia.Using polymerase chain reaction,56%(49/87)of ticks were positive for the Rickettsia outer membrane protein(ompB)gene.Multi-locus sequence and phylogenetic analysis based on the ompB,ompA,and citrate synthase(gltA)genes showed that the ticks carried R.africae,and other Rickettsia spp.closely related to R.raoultii,R.massiliae,R.tamurae and R.monacensis.Given the proximity between humans,livestock,and wildlife in these habitats,there exists a considerable risk of transmission of zoonotic Rickettsia to human populations in this rural setting.These results call for heightened awareness and further research into the dynamics of tick-borne diseases in regions where humans and animals coexist,particularly in the context of tortoise-associated ticks as vectors.Understanding and addressing these potential disease vectors is crucial for effective public health measures and the prevention of Rickettsia zoonoses.展开更多
【目的】检测Q型烟粉虱Bemisia tabaci(Gennadius)体内Rickettsia的感染情况,研究分析Rickettsia共生菌经烟粉虱传入豇豆植物后的分布、转移效率等。【方法】以Q型烟粉虱为实验材料,利用常规PCR及荧光原位杂交技术(FISH),检测了烟粉虱体...【目的】检测Q型烟粉虱Bemisia tabaci(Gennadius)体内Rickettsia的感染情况,研究分析Rickettsia共生菌经烟粉虱传入豇豆植物后的分布、转移效率等。【方法】以Q型烟粉虱为实验材料,利用常规PCR及荧光原位杂交技术(FISH),检测了烟粉虱体内Rickettsia的感染率,以及Rickettsia传入豇豆植物体内后的存留情况。【结果】Q型烟粉虱可以通过取食将Rickettsia传至豇豆植株内;接虫数量与Rickettsia传入效率及其在取食部位相邻的下部叶片中检测到的起始时间呈负相关;Rickettsia经烟粉虱取食传入豇豆叶片后,集中分布在叶片的韧皮部筛管中;基于16S r RNA的系统发育分析结果表明,Q型烟粉虱体内的Rickettsia与经取食传入豇豆叶片的Rickettsia高度同源。【结论】Rickettsia可以通过烟粉虱的取食传入植物体内,并且可以在相邻叶片之间转移传播,Rickettsia在由寄主昆虫向植株传播过程中高度保守。展开更多
目的确认长角血蜱是否具有经卵传播斑点热群立克次体(Spotted fever group rickettsia,SFGR)新基因型Candidatus Rickettsia longicornii的能力。方法采集牛体表饱血长角血蜱,在实验室诱导产卵,并采用聚合酶链式反应检测蜱卵中Candidatu...目的确认长角血蜱是否具有经卵传播斑点热群立克次体(Spotted fever group rickettsia,SFGR)新基因型Candidatus Rickettsia longicornii的能力。方法采集牛体表饱血长角血蜱,在实验室诱导产卵,并采用聚合酶链式反应检测蜱卵中Candidatus R. longicornii核酸。扩增长角血蜱母体和蜱卵中Candidatus R. longicornii基因序列,分析同源性和遗传进化关系。结果共采集55只饱血长角血蜱(雌性成蜱),检测Candidatus R. longicornii核酸,21只阳性,阳性率为38.18%。共收集约2 500只长角血蜱蜱卵,分成50组检测Candidatus R. longicornii,6组阳性,蜱卵最低感染率为0.24%。经同源性分析,长角血蜱母体和蜱卵Candidatus R. longicornii基因序列与首次在韩国发现的蜱源ROK-HL727株Candidatus R. longicornii基因序列同源性均达到99.79%以上。母体和蜱卵2个Candidatus R. longicornii基因序列间同源性达到99.69%以上,在系统进化关系上均与ROK-HL727株基因序列处于同一个分支,且遗传关系较近。结论长角血蜱母体SFGR Candidatus R. longicornii基因型感染率较高,且可经卵传播该基因型。展开更多
Objective:To identify members of genera of rickettsia and O.tsutsugammhi simultaneously.Methods:Rapid and duplex and nested PCR methods have been established by designing primers based on the conserved regions of heat...Objective:To identify members of genera of rickettsia and O.tsutsugammhi simultaneously.Methods:Rapid and duplex and nested PCR methods have been established by designing primers based on the conserved regions of heat shock protein GroEL gene.345 mouse viscera samples including liver,spleen and kidney,96 Xenopsylla cheopis and 32 chiggers collected from Hongta areas of Yuxi city,Yunnan province were tested by the new PCR methods.Results:The result of the study showed that the new PCR methods could identify most members of genera -Rickettsia and Orientia simultaneously with 100%specificity and its sensitivity could test one copy per microliter.The results of detection prevalence of rickettsioses in mouse,flea and mites DNA samples showed that the total rickettsia infection rate in mouse was 34.78%(120/345).The total infection rates in R.typhi,O.t Karp and R.sibirica of mouse samples were 28.12%(97/345),19.71%(68/345) and O. 29%(1/345) respectively.Co-infection rates in R.typhi and 0.t Karp of mouse samples were 13.33%(46/ 345).O.t Karp type has been the main epidemic strain in these areas.Conclusion:We concluded that this PCR method could be used to detect multi-genera rickettsia simultaneously.Molecular evidences provided in this and previous studies strongly support that Hongta areas of Yuxi city are a natural focus for typhus and scrub typhus with the common occurrence of their confection.展开更多
The death which occurred in juvenile population was a severe problem in the course ofPinctada maxima artificial culture. With the methods of field investigation, histological study and statistic analyses, the epidemio...The death which occurred in juvenile population was a severe problem in the course ofPinctada maxima artificial culture. With the methods of field investigation, histological study and statistic analyses, the epidemiological study was carried out on the disease and death in juvenile populations of Pinctada maxima in the Xinying Pearl Oyster Mariculture Farm of Lingao County (for the A, B and C batches of cultured juveniles hanged in the sea) and the Xincun Pearl Oyster Mariculture Farm of Lingshui County (for the D batch of cultured juvenile hanged in the pond), Hainan Province from November 1993 to April 1995.The results show that the deaths which occurred in juvenile populations of Pinctada maxima presented an outbreak pattern. The peak of mortality rates, in general, occurred in 4-to 6-month old pearl oyster juveniles, and the mortality rates gradully declined with the extention of pearl oyster age after cul-turing 8 months. The correlation between the mortality rates of juvenile populations and mean body lengths of juvenile populations show that the mortality rate become higher under 4 cm of mean body lengths of juvenile population and become obvious declined over 5 cm of mean body lengths. The peak of mortality rate occurred in 1-3 cm of mean body lengths. The results of histological observation showed that rickettsia-like organism inclusions were common, histological widespread infective agent among every batches (A, B, C and D) of cultured juvenile populations. The mean severity indices (SI) of rickettsia-like organism (RLO) infection were positively correlated with mortality rates of juvenile populations. After or within every peaks of RLO infection were all accompanied with the peaks of mortality rates of host populations and the mortality rates declined with decreased RLO infection. So the evidences of histological observation and epidemiology in this study indicated that rickettsia-like organism (RLO) may be as an important pathogenic organism of disease and death of cultured Pinctada maxima. In addition, a few ciliates were discovered only in part of batch A of cultured juvenile population. The mortality rates in juvenile populations were not correlated with the weekly mean temperature and salinity of sea water.展开更多
The epidemiological investigations on the disease and death in mature eggs, embryonic de- velopmental periods and larvae populations [including oocytes, fertilized ovum, early embryonic phase larvae (6 h), D-shaped ph...The epidemiological investigations on the disease and death in mature eggs, embryonic de- velopmental periods and larvae populations [including oocytes, fertilized ovum, early embryonic phase larvae (6 h), D-shaped phase larvae (24 h), early umbo phase larvae, umbo phase larvae, post um- bo phase larvae and eyespot phase larvae] in the Luhuitou Pearl Oyster Mariculture Farm of Sanya City, Hainan Province in April 1995 showed that there were two peaks of mortality rates which occurred in early umbo phase or umbo phase and post umbo phase (Figs 3-5 and Table 1) respectively from pre- embryonic developmental periods to larvae phases. It indicated that the onset and death of Pinctada maxima larvae populations followed a pattem of outbreak. Between the prevalence, intensity of RLO infection and the mortality rates of larvae populations were of obvious positively correlations. Generally, every peak of RLO infection is always follwed by a peak of mortality rate of larvae hosts, and the mor- tality rates of larvae hosts declined with the decreased RLO infection (see Figs 3-5 ). Under the trans- mission electron microscopy (TEM), no rickettsia-like organisms were discovered in oocytes, fertilized ovum and early embryonic phase larvae (6 h). The RLO inclusions occurred first in the D-shaped phase larvae (24 h) under histological examination. Absences of RLO in transmission electron exami- nation of oocytes of RLO-infected adult females, ferilized ovum and early embryonic phase larvae (6 h) indicated that RLO may not be transmitted transovarially. But RLO for host infection may be trans- mitted by contact transmission since RLO inclusions were first identified regularly in D-shaped phase larvae (24 h), while these D-shaped phase larvae were still unable to take food during hatching 24 hours. In addition, the result of epidemiological investigation showed that no odservable death occurred in D-shaped larvae populations, but early obvious death occurred in larvae populations in the seventh day after fertilization, in a rate of about 21. 8%. It indicated that there was a incubation peried from RLO infection for host (D-shaped phase larvae) to host onset and death occurred clinically.展开更多
Objective:To determine the prevalence of tick-borne pathogens with a particular focus on Rickettsia spp.in ticks collected from cattle in Gauteng and Limpopo Provinces,South Africa.Methods:A total of 200 ticks were co...Objective:To determine the prevalence of tick-borne pathogens with a particular focus on Rickettsia spp.in ticks collected from cattle in Gauteng and Limpopo Provinces,South Africa.Methods:A total of 200 ticks were collected from cattle within the Madala livestock,Pretoria,Gauteng Province and in Mankweng Township,Polokwane,Limpopo Province in 2019.The ticks were morphologically identified and processed individually for a total genomic DNA extraction.Specific primers targetting ompA,ompB,and the 17KDa genes were used for a molecular screening and delineation of Rickettsia from the extracted genetic materials using polymerase chain reaction(PCR)technique.PCR amplicons of positive samples were sequenced bidirectionally using the Sanger sequencing method.Sequences generated were processed and analysed using appropriate bioinformatics software.Results:The ticks were morphologically identified as Amblyomma spp.PCR profiling of the genomic DNA samples revealed the presence of the Rickettsia pathogen in 42(21%)of the ticks collected from both Provinces.Out of the genes profiled,14(7%)were positive for 17KDa,42(21%)for ompA and 32(16%)were positive for ompB genes respectively.The nucleotide blast of the sequenced genomes showed high similarity,as high as 100% with other reference Rickettsia(R.)africae in the GenBank.The phylogenetic analysis of the sequences further validated them as R.africae with their characteristic clustering pattern with related reference sequences.Conclusions:There is an abundance of R.africae in Amblyomma ticks collected from cattle in the study areas.This has serious public health implications as individuals who accidentally get infested with the ticks could acquire R.africae.Hence,adequate precautions in terms of sensitization of farmers about the risk and mass mobilization drive to control the vectors in the areas are highly recommended to safeguard public health.展开更多
A molecular survey of 230 serum samples from cattle was studied by PCR-amplification of the citrate synthase gene gltA, the gene coding for protein 190 kDa—ompA—and the gene ompB. The study was carried out in the Ju...A molecular survey of 230 serum samples from cattle was studied by PCR-amplification of the citrate synthase gene gltA, the gene coding for protein 190 kDa—ompA—and the gene ompB. The study was carried out in the Junta of Castilla y León (northern Spain). The results suggest that the molecular study of the serum cattle would not make a good method in epidemiological studies on rickettsiae in this region. But it is necessary to continue and expand the work with more sensitive molecular methods.展开更多
Tick-Borne Rickettsial Diseases (TBRD) are emerging zoonotic diseases, and a problem of human health and veterinary medication. The distribution of these diseases is related to the distribution of vector. The presence...Tick-Borne Rickettsial Diseases (TBRD) are emerging zoonotic diseases, and a problem of human health and veterinary medication. The distribution of these diseases is related to the distribution of vector. The presence of pathogens in the host is a risk indicator of population exposure to these areas. A total of 478 tissues samples from rodents, A. phagocytophilum 18 (3.7%), E. canis 47 (9.8%), Rickettsia rickettsii 18 (3.7%) and E. chaffeensis 19 (3.9%) were detected using species-specific PCR assay. It is the first report in Mexico the presence of rodents infected with A. phagocytophilum and E. chaffeensis. The rodent Peromyscus spp. were the most commonly prevalent host of infection for all the bacteria’s. We have to consider as host of TBRD transmitter and provide a useful contribution to understanding their epidemiology. The health sector should be considered all the fevers of unknown causes in humans and animals in Mexico as infections by these vector-borne rickettsial pathogens.展开更多
A series of mass mortalities of the cultured blood clam, Tegillarca granosa, occurred in the Yueqing Bay of China from 2005 to 2009. An obligate intracellular prokaryote, designated as rickettsia-like organism （RLO）...A series of mass mortalities of the cultured blood clam, Tegillarca granosa, occurred in the Yueqing Bay of China from 2005 to 2009. An obligate intracellular prokaryote, designated as rickettsia-like organism （RLO）, was frequently found in the moribund or dead blood clam sample during ultra- structural examination. These organisms were usually round, ellipsoid or occasionally dumbbell- shaped, ranged from approximately 0.28 to 0.71 #m in size and had a trilaminar cell wall. Two reproductive modes of organisms, transverse binary fission and budding, were observed. The or- ganisms were able to form eosinophilic inclusions. Most inclusions were found within epithelial and connective tissues of the mantle, gills and digestive tube. The biological and morphological char- acteristics indicate that these organisms may belong to the family Rickettsiaceae. RLOs exhibited significant pathogenicity. Cytopathological examinations revealed extensive necrosis and destruc- tion in the infected cell. The degree of tissue destruction was positively related to the number of RLO inclusions in the tissues, and the cytopathological effects were positively related to the number of intracellular RLO. RLOs and their inclusions were discovered throughout different disease areas and in different time periods. The infection intensity of the RLOs was positively correlated with the mortality rate of clams. Therefore, RLO infection might be associated with mass mortalities of cultured blood clams in the Yueqing Bay.展开更多
Background Rickettsia and related diseases have been identified as significant global public health threats.This study involved comprehensive field and systematic investigations of various rickettsial organisms in Yun...Background Rickettsia and related diseases have been identified as significant global public health threats.This study involved comprehensive field and systematic investigations of various rickettsial organisms in Yunnan Province.Methods Between May 18,2011 and November 23,2020,field investigations were conducted across 42 counties in Yunnan Province,China,encompassing small mammals,livestock,and ticks.Preliminary screenings for Rickettsiales involved amplifying the 16S rRNA genes,along with additional genus-or species-specific genes,which were subse-quently confrmed through sequencing results.Sequence comparisons were carried out using the Basic Local Align-ment Search Tool(BLAST).Phylogenetic relationships were analyzed using the default parameters in the Molecular Evolutionary Genetics Analysis(MEGA)program.The chi-squared test was used to assess the diversities and compo-nent ratios of rickettsial agents across various parameters.Results A total of 7964 samples were collected from small mammals,livestock,and ticks through Yunnan Province and submitted for screening for rickettsial organisms.Sixteen rickettsial species from the genera Rickettsia,Anaplasma,Ehrlichia,Neoehrlichia,and Wolbachia were detected,with an overall prevalence of 14.72%.Among these,11 species were identifed as pathogens or potential pathogens to humans and livestock.Specifically,10 rickettsial organisms were widely found in 42.11%(24 out of 57)of small mammal species.High prevalence was observed in Dremomys samples at 5.60%,in samples from regions with latitudes above 4000 m or alpine meadows,and in those obtained from Yuanmou County.Anaplasma phagocytophilum and Candidatus Neoehrlichia mikurensis were broadly infect-ing multiple genera of animal hosts.In contrast,the small mammal genera Neodon,Dremomys,Ochotona,Anouro-sorex,and Mus were carrying individually specific rickettsial agents,indicating host tropism.There were 13 rickettsial species detected in 57.14%(8 out of 14)of tick species,with the highest prevalence(37.07%)observed in the genus Rhipicephalus.Eight rickettsial species were identified in 2375 livestock samples.Notably,six new Rickettsiales variants/strains were discovered,and Candidatus Rickettsia longicorni was unambiguously identified.Conclusions This large-scale survey provided further insight into the high genetic diversity and overall prevalence of emerging Rickettsiales within endemic hotspots in Yunnan Province.The potential threats posed by these emerging tick-borne Rickettsiales to public health warrant attention,underscoring the need for effective strategies to guide the prevention and control of emerging zoonotic diseases in China.展开更多
文摘In sub-Saharan Africa,limited studies have investigated zoonotic pathogens that may be harboured by ticks infesting reptiles such as tortoises.Here,we report the presence of pathogenic Rickettsia in ticks(Amblyomma marmoreum)collected from the leopard tortoise(Geochelone pardalis)in rural Zambia.Using polymerase chain reaction,56%(49/87)of ticks were positive for the Rickettsia outer membrane protein(ompB)gene.Multi-locus sequence and phylogenetic analysis based on the ompB,ompA,and citrate synthase(gltA)genes showed that the ticks carried R.africae,and other Rickettsia spp.closely related to R.raoultii,R.massiliae,R.tamurae and R.monacensis.Given the proximity between humans,livestock,and wildlife in these habitats,there exists a considerable risk of transmission of zoonotic Rickettsia to human populations in this rural setting.These results call for heightened awareness and further research into the dynamics of tick-borne diseases in regions where humans and animals coexist,particularly in the context of tortoise-associated ticks as vectors.Understanding and addressing these potential disease vectors is crucial for effective public health measures and the prevention of Rickettsia zoonoses.
文摘【目的】检测Q型烟粉虱Bemisia tabaci(Gennadius)体内Rickettsia的感染情况,研究分析Rickettsia共生菌经烟粉虱传入豇豆植物后的分布、转移效率等。【方法】以Q型烟粉虱为实验材料,利用常规PCR及荧光原位杂交技术(FISH),检测了烟粉虱体内Rickettsia的感染率,以及Rickettsia传入豇豆植物体内后的存留情况。【结果】Q型烟粉虱可以通过取食将Rickettsia传至豇豆植株内;接虫数量与Rickettsia传入效率及其在取食部位相邻的下部叶片中检测到的起始时间呈负相关;Rickettsia经烟粉虱取食传入豇豆叶片后,集中分布在叶片的韧皮部筛管中;基于16S r RNA的系统发育分析结果表明,Q型烟粉虱体内的Rickettsia与经取食传入豇豆叶片的Rickettsia高度同源。【结论】Rickettsia可以通过烟粉虱的取食传入植物体内,并且可以在相邻叶片之间转移传播,Rickettsia在由寄主昆虫向植株传播过程中高度保守。
文摘目的确认长角血蜱是否具有经卵传播斑点热群立克次体(Spotted fever group rickettsia,SFGR)新基因型Candidatus Rickettsia longicornii的能力。方法采集牛体表饱血长角血蜱,在实验室诱导产卵,并采用聚合酶链式反应检测蜱卵中Candidatus R. longicornii核酸。扩增长角血蜱母体和蜱卵中Candidatus R. longicornii基因序列,分析同源性和遗传进化关系。结果共采集55只饱血长角血蜱(雌性成蜱),检测Candidatus R. longicornii核酸,21只阳性,阳性率为38.18%。共收集约2 500只长角血蜱蜱卵,分成50组检测Candidatus R. longicornii,6组阳性,蜱卵最低感染率为0.24%。经同源性分析,长角血蜱母体和蜱卵Candidatus R. longicornii基因序列与首次在韩国发现的蜱源ROK-HL727株Candidatus R. longicornii基因序列同源性均达到99.79%以上。母体和蜱卵2个Candidatus R. longicornii基因序列间同源性达到99.69%以上,在系统进化关系上均与ROK-HL727株基因序列处于同一个分支,且遗传关系较近。结论长角血蜱母体SFGR Candidatus R. longicornii基因型感染率较高,且可经卵传播该基因型。
基金supported by National Natural Science Foundation of China(No. 30771854)China-U.S.Collaborative Program on Emerging and Re-emerging Infectious Diseases(No. 1U2GGH000018-01)
文摘Objective:To identify members of genera of rickettsia and O.tsutsugammhi simultaneously.Methods:Rapid and duplex and nested PCR methods have been established by designing primers based on the conserved regions of heat shock protein GroEL gene.345 mouse viscera samples including liver,spleen and kidney,96 Xenopsylla cheopis and 32 chiggers collected from Hongta areas of Yuxi city,Yunnan province were tested by the new PCR methods.Results:The result of the study showed that the new PCR methods could identify most members of genera -Rickettsia and Orientia simultaneously with 100%specificity and its sensitivity could test one copy per microliter.The results of detection prevalence of rickettsioses in mouse,flea and mites DNA samples showed that the total rickettsia infection rate in mouse was 34.78%(120/345).The total infection rates in R.typhi,O.t Karp and R.sibirica of mouse samples were 28.12%(97/345),19.71%(68/345) and O. 29%(1/345) respectively.Co-infection rates in R.typhi and 0.t Karp of mouse samples were 13.33%(46/ 345).O.t Karp type has been the main epidemic strain in these areas.Conclusion:We concluded that this PCR method could be used to detect multi-genera rickettsia simultaneously.Molecular evidences provided in this and previous studies strongly support that Hongta areas of Yuxi city are a natural focus for typhus and scrub typhus with the common occurrence of their confection.
基金Major State Basic Research Development Program of China under contract No. G1999012001Key Science Foundation of the Chinese Academy of Sciences contract KS85-121.
文摘The death which occurred in juvenile population was a severe problem in the course ofPinctada maxima artificial culture. With the methods of field investigation, histological study and statistic analyses, the epidemiological study was carried out on the disease and death in juvenile populations of Pinctada maxima in the Xinying Pearl Oyster Mariculture Farm of Lingao County (for the A, B and C batches of cultured juveniles hanged in the sea) and the Xincun Pearl Oyster Mariculture Farm of Lingshui County (for the D batch of cultured juvenile hanged in the pond), Hainan Province from November 1993 to April 1995.The results show that the deaths which occurred in juvenile populations of Pinctada maxima presented an outbreak pattern. The peak of mortality rates, in general, occurred in 4-to 6-month old pearl oyster juveniles, and the mortality rates gradully declined with the extention of pearl oyster age after cul-turing 8 months. The correlation between the mortality rates of juvenile populations and mean body lengths of juvenile populations show that the mortality rate become higher under 4 cm of mean body lengths of juvenile population and become obvious declined over 5 cm of mean body lengths. The peak of mortality rate occurred in 1-3 cm of mean body lengths. The results of histological observation showed that rickettsia-like organism inclusions were common, histological widespread infective agent among every batches (A, B, C and D) of cultured juvenile populations. The mean severity indices (SI) of rickettsia-like organism (RLO) infection were positively correlated with mortality rates of juvenile populations. After or within every peaks of RLO infection were all accompanied with the peaks of mortality rates of host populations and the mortality rates declined with decreased RLO infection. So the evidences of histological observation and epidemiology in this study indicated that rickettsia-like organism (RLO) may be as an important pathogenic organism of disease and death of cultured Pinctada maxima. In addition, a few ciliates were discovered only in part of batch A of cultured juvenile population. The mortality rates in juvenile populations were not correlated with the weekly mean temperature and salinity of sea water.
基金This study was supported by the Projects under the Major State Basic Research Development Program under contractNo.G199012001,
文摘The epidemiological investigations on the disease and death in mature eggs, embryonic de- velopmental periods and larvae populations [including oocytes, fertilized ovum, early embryonic phase larvae (6 h), D-shaped phase larvae (24 h), early umbo phase larvae, umbo phase larvae, post um- bo phase larvae and eyespot phase larvae] in the Luhuitou Pearl Oyster Mariculture Farm of Sanya City, Hainan Province in April 1995 showed that there were two peaks of mortality rates which occurred in early umbo phase or umbo phase and post umbo phase (Figs 3-5 and Table 1) respectively from pre- embryonic developmental periods to larvae phases. It indicated that the onset and death of Pinctada maxima larvae populations followed a pattem of outbreak. Between the prevalence, intensity of RLO infection and the mortality rates of larvae populations were of obvious positively correlations. Generally, every peak of RLO infection is always follwed by a peak of mortality rate of larvae hosts, and the mor- tality rates of larvae hosts declined with the decreased RLO infection (see Figs 3-5 ). Under the trans- mission electron microscopy (TEM), no rickettsia-like organisms were discovered in oocytes, fertilized ovum and early embryonic phase larvae (6 h). The RLO inclusions occurred first in the D-shaped phase larvae (24 h) under histological examination. Absences of RLO in transmission electron exami- nation of oocytes of RLO-infected adult females, ferilized ovum and early embryonic phase larvae (6 h) indicated that RLO may not be transmitted transovarially. But RLO for host infection may be trans- mitted by contact transmission since RLO inclusions were first identified regularly in D-shaped phase larvae (24 h), while these D-shaped phase larvae were still unable to take food during hatching 24 hours. In addition, the result of epidemiological investigation showed that no odservable death occurred in D-shaped larvae populations, but early obvious death occurred in larvae populations in the seventh day after fertilization, in a rate of about 21. 8%. It indicated that there was a incubation peried from RLO infection for host (D-shaped phase larvae) to host onset and death occurred clinically.
文摘【目的】通过研究烟粉虱Bemisia tabaci取食传入植物体内的昆虫内共生菌种类,探明其在不同植物中的分布形态及时空动态。【方法】以B型烟粉虱、棉花、番茄、豇豆为实验材料,利用常规PCR检测烟粉虱取食后传入植物体内的共生菌种类;利用透射电镜(Transmission electron microscope,TEM)检测Rickettsia传入植物后的分布及形态;利用q-PCR技术检测豇豆叶片中Rickettsia含量的动态变化。【结果】B型烟粉虱体内含有原生共生菌Portiera、次生共生菌Rickettsia,Hamiltonella和Hemipteriphilus,但只检测到Rickettsia可经烟粉虱传入棉花、番茄、豇豆植物体内,并可在植物体内存活、转移。在3种植物体内Rickettsia均分布于叶片韧皮部的筛管细胞中。烟粉虱、棉花、番茄组织内的Rickettsia形态基本一致,但豇豆中Rickettsia在形态上较小而钝圆。相同数量的烟粉虱取食,在豇豆体内最先检测到Rickettsia。随着烟粉虱取食时间的增加,豇豆体内的Rickettsia含量先增加后下降;而当无烟粉虱持续取食时,一定时间段内豇豆体内的Rickettsia先下降再小幅度上升,并可以在一定时间内保持不变。基于16S rDNA序列的系统发育分析表明,传入棉花、番茄、豇豆叶片中的Rickettsia与B型烟粉虱体内的Rickettsia高度同源。【结论】Rickettsia可经烟粉虱取食传入植物体内,分布并存活于韧皮部的筛管细胞中,并可在植物不同叶片之间转移;在不同植物宿主中,Rickettsia的形态会发生轻微变化;烟粉虱对Rickettsia的传播效率受到植物种类的影响。
基金funded by SAMRC with grant number RDG2017/18 and the APC was funded by SMU.
文摘Objective:To determine the prevalence of tick-borne pathogens with a particular focus on Rickettsia spp.in ticks collected from cattle in Gauteng and Limpopo Provinces,South Africa.Methods:A total of 200 ticks were collected from cattle within the Madala livestock,Pretoria,Gauteng Province and in Mankweng Township,Polokwane,Limpopo Province in 2019.The ticks were morphologically identified and processed individually for a total genomic DNA extraction.Specific primers targetting ompA,ompB,and the 17KDa genes were used for a molecular screening and delineation of Rickettsia from the extracted genetic materials using polymerase chain reaction(PCR)technique.PCR amplicons of positive samples were sequenced bidirectionally using the Sanger sequencing method.Sequences generated were processed and analysed using appropriate bioinformatics software.Results:The ticks were morphologically identified as Amblyomma spp.PCR profiling of the genomic DNA samples revealed the presence of the Rickettsia pathogen in 42(21%)of the ticks collected from both Provinces.Out of the genes profiled,14(7%)were positive for 17KDa,42(21%)for ompA and 32(16%)were positive for ompB genes respectively.The nucleotide blast of the sequenced genomes showed high similarity,as high as 100% with other reference Rickettsia(R.)africae in the GenBank.The phylogenetic analysis of the sequences further validated them as R.africae with their characteristic clustering pattern with related reference sequences.Conclusions:There is an abundance of R.africae in Amblyomma ticks collected from cattle in the study areas.This has serious public health implications as individuals who accidentally get infested with the ticks could acquire R.africae.Hence,adequate precautions in terms of sensitization of farmers about the risk and mass mobilization drive to control the vectors in the areas are highly recommended to safeguard public health.
文摘A molecular survey of 230 serum samples from cattle was studied by PCR-amplification of the citrate synthase gene gltA, the gene coding for protein 190 kDa—ompA—and the gene ompB. The study was carried out in the Junta of Castilla y León (northern Spain). The results suggest that the molecular study of the serum cattle would not make a good method in epidemiological studies on rickettsiae in this region. But it is necessary to continue and expand the work with more sensitive molecular methods.
文摘Tick-Borne Rickettsial Diseases (TBRD) are emerging zoonotic diseases, and a problem of human health and veterinary medication. The distribution of these diseases is related to the distribution of vector. The presence of pathogens in the host is a risk indicator of population exposure to these areas. A total of 478 tissues samples from rodents, A. phagocytophilum 18 (3.7%), E. canis 47 (9.8%), Rickettsia rickettsii 18 (3.7%) and E. chaffeensis 19 (3.9%) were detected using species-specific PCR assay. It is the first report in Mexico the presence of rodents infected with A. phagocytophilum and E. chaffeensis. The rodent Peromyscus spp. were the most commonly prevalent host of infection for all the bacteria’s. We have to consider as host of TBRD transmitter and provide a useful contribution to understanding their epidemiology. The health sector should be considered all the fevers of unknown causes in humans and animals in Mexico as infections by these vector-borne rickettsial pathogens.
基金Scientific Projects of Zhejiang Province,China under contract Nos 2004C23041 and 20080123
文摘A series of mass mortalities of the cultured blood clam, Tegillarca granosa, occurred in the Yueqing Bay of China from 2005 to 2009. An obligate intracellular prokaryote, designated as rickettsia-like organism （RLO）, was frequently found in the moribund or dead blood clam sample during ultra- structural examination. These organisms were usually round, ellipsoid or occasionally dumbbell- shaped, ranged from approximately 0.28 to 0.71 #m in size and had a trilaminar cell wall. Two reproductive modes of organisms, transverse binary fission and budding, were observed. The or- ganisms were able to form eosinophilic inclusions. Most inclusions were found within epithelial and connective tissues of the mantle, gills and digestive tube. The biological and morphological char- acteristics indicate that these organisms may belong to the family Rickettsiaceae. RLOs exhibited significant pathogenicity. Cytopathological examinations revealed extensive necrosis and destruc- tion in the infected cell. The degree of tissue destruction was positively related to the number of RLO inclusions in the tissues, and the cytopathological effects were positively related to the number of intracellular RLO. RLOs and their inclusions were discovered throughout different disease areas and in different time periods. The infection intensity of the RLOs was positively correlated with the mortality rate of clams. Therefore, RLO infection might be associated with mass mortalities of cultured blood clams in the Yueqing Bay.
文摘Background Rickettsia and related diseases have been identified as significant global public health threats.This study involved comprehensive field and systematic investigations of various rickettsial organisms in Yunnan Province.Methods Between May 18,2011 and November 23,2020,field investigations were conducted across 42 counties in Yunnan Province,China,encompassing small mammals,livestock,and ticks.Preliminary screenings for Rickettsiales involved amplifying the 16S rRNA genes,along with additional genus-or species-specific genes,which were subse-quently confrmed through sequencing results.Sequence comparisons were carried out using the Basic Local Align-ment Search Tool(BLAST).Phylogenetic relationships were analyzed using the default parameters in the Molecular Evolutionary Genetics Analysis(MEGA)program.The chi-squared test was used to assess the diversities and compo-nent ratios of rickettsial agents across various parameters.Results A total of 7964 samples were collected from small mammals,livestock,and ticks through Yunnan Province and submitted for screening for rickettsial organisms.Sixteen rickettsial species from the genera Rickettsia,Anaplasma,Ehrlichia,Neoehrlichia,and Wolbachia were detected,with an overall prevalence of 14.72%.Among these,11 species were identifed as pathogens or potential pathogens to humans and livestock.Specifically,10 rickettsial organisms were widely found in 42.11%(24 out of 57)of small mammal species.High prevalence was observed in Dremomys samples at 5.60%,in samples from regions with latitudes above 4000 m or alpine meadows,and in those obtained from Yuanmou County.Anaplasma phagocytophilum and Candidatus Neoehrlichia mikurensis were broadly infect-ing multiple genera of animal hosts.In contrast,the small mammal genera Neodon,Dremomys,Ochotona,Anouro-sorex,and Mus were carrying individually specific rickettsial agents,indicating host tropism.There were 13 rickettsial species detected in 57.14%(8 out of 14)of tick species,with the highest prevalence(37.07%)observed in the genus Rhipicephalus.Eight rickettsial species were identified in 2375 livestock samples.Notably,six new Rickettsiales variants/strains were discovered,and Candidatus Rickettsia longicorni was unambiguously identified.Conclusions This large-scale survey provided further insight into the high genetic diversity and overall prevalence of emerging Rickettsiales within endemic hotspots in Yunnan Province.The potential threats posed by these emerging tick-borne Rickettsiales to public health warrant attention,underscoring the need for effective strategies to guide the prevention and control of emerging zoonotic diseases in China.
