中西药物防制微小牛蜱成蜱的比较性研究

目的观察中药百部、枫树果对微小牛蜱的防制作用。方法湘南林区9个采样点对带有微小牛蜱的耕牛12头随机分为2组,分别用百部、枫树果乙醇提取液;1%的敌百虫溶液观察比较其对微小牛蜱的击倒作用以及对微小牛蜱的中枢神经团、生殖系统的影响。结果中药组较敌百虫组对微小牛蜱中枢神经团、雄蜱生殖孔有明显的损害作用(P<0.01),中草药组和敌百虫组对微小牛蜱的击倒作用两组比较差异无显著性(P>0.05)。结论中药组和敌百虫组对微小牛蜱均有明显的击倒作用,但对神经系统、生殖系统的影响前者明显优于后者,中草药且有对人畜几乎无毒等优点。     

Peripheral cellular and humoral responses to infestation with the cattle tick Rhipicephalus microplus in Santa Gertrudis cattle

Resistance to cattle tick infestation in single‐host ticks is primarily manifested against the larval stage and results in the immature tick failing to attach successfully and obtain a meal. This study was conducted to identify immune responses that characterize the tick‐resistant phenotype in cattle. Thirty‐five tick‐naïve Santa Gertrudis heifers were used in this study, thirty of which were artificially infested for thirteen weeks with tick larvae while five animals remained at a tick‐free quarantine property to serve as a control group. Following thirteen weeks of tick infestation, the animals in this trial exhibited highly divergent tick‐resistant phenotypes. Blood samples collected throughout the trial were used to measure peripheral immune parameters: haematology, the percentage of cellular subsets comprising the peripheral blood mononuclear cell (PBMC) population, tick‐specific IgG₁ and IgG₂ antibody titres, IgG1 avidity for tick antigens and the ability of PBMC to recognize and proliferate in response to stimulation with tick antigens in vitro. The tick‐susceptible cattle developed significantly higher tick‐specific IgG₁ antibody titres compared to the tick‐resistant animals. These results suggest that the heightened antibody response either does not play a role in resistance or might contribute to increased susceptibility to infestation.     

Local immune response to larvae of Rhipicephalus microplus in Santa Gertrudis cattle

This study investigated the local immune response at larval attachment sites in Santa Gertrudis cattle with low and high levels of tick resistance. Skin samples with tick larvae attached were collected from Santa Gertrudis cattle at the end of a period of 25 weekly infestations, when the animals manifested highly divergent tick‐resistant phenotypes. There was a tendency for more CD3⁺, CD4⁺, CD8⁺, CD25⁺, γδ T cells and neutrophils to concentrate at larval tick attachment site in susceptible cattle than in resistant cattle but the differences were significant only for γδ T cells and CD4⁺ cells. Most of the cattle developed intra‐epidermal vesicles at the larval attachment site but the predominant cell within or around the vesicles was the neutrophil in susceptible animals and eosinophil in the resistant animals. The monoclonal antibodies (mAbs) specific for CD45 and CD45 RO antigens reacted with skin leucocytes from a higher number of susceptible cattle than resistant cattle. Our data suggest that some of the cellular responses mounted at larval attachment site are not involved in tick protection. The mAbs specific for CD45 and CD45 RO directly, or a test for CD45 genotype might be developed as markers of tick susceptibility or resistance.     

海南微小牛蜱(Boophilus micloplus)Q热立克次体的分离

1986-1987两年来,我们从海南岛的洛南、西榕地区水牛身上捕捉的微小牛蜱(Boo-philus mieroplus),分为21组接种豚鼠,其中4组分离出立克次体,总阳性率为19.04％。该立克次体经鉴定是属于Q热立克次体。提示微小牛蜱是海南Q热宿主之一。     

四川省南川县莱姆病的调查

四川东部南川县是莱姆病流行区。本文对300例居民进行了血清学调查,抗莱姆病螺旋体IgG抗体阳性54人,人群自然感染率为18%。35例经临床和血清学确诊的莱姆病患者,其临床表现为慢性游走性红斑7例,关节炎13例,面神经麻痹7例,多发性神经炎7例,脑膜炎2例和心脏异常1例。47只微小牛蜱的中肠标本,有3只检出了螺旋体,带菌率为6.4%。     

Expression and immunolocalization of a Boophilus microplus cathepsin L-like enzyme

Efforts are being undertaken to control tick infestations that cause important economic losses. A cathepsin L-like endopeptidase of Boophilus microplus was expressed in Escherichia coli; the recombinant enzyme was capable of hydrolysing gelatin, tick vitellin and bovine haemoglobin. In this paper we focus on the expression and local of synthesis of this enzyme in the tick. RT-PCR experiments showed that this endopeptidase is transcribed in the gut of partially engorged tick females. In immunoblotting, polyclonal antibodies against the recombinant enzyme reacted with proteins of larvae older than 5 days, of fully and partially engorged female gut. In immunolocalization experiments the enzyme was localized in probable secretory cells of the gut. Based on our findings we postulate that BmCL1 may be involved in haemoglobin degradation in the B. microplus gut. This enzyme may be used as target for the control of this parasite.     

Serial analysis of gene expression in the southern cattle tick following acaricide treatment of larvae from organophosphate resistant and susceptible strains

Organophosphate resistant and susceptible tick larvae from laboratory strains of the southern cattle tick, Rhipicephalus (Boophilus) microplus were exposed to low doses of the organophosphate (OP) acaricide, coumaphos. Serial analysis of gene expression (SAGE) was used to analyse differential gene expression in response to OP treatment and to compare the responses of OP-treated and -untreated resistant and susceptible tick larvae. An R. microplus Gene Index was used as an EST database to identify genes which corresponded to SAGE tags whose abundance changed in response to acaricide exposure. Relative quantitative RT-PCR was used to confirm the differential expression results from the SAGE experiments. Of particular interest is a SAGE tag which corresponds to a cytochrome P450-like EST in the Gene Index which was more abundant in untreated OP resistant larvae compared to untreated OP susceptible larvae. This SAGE tag was also more abundant in OP resistant larvae treated with OP compared to OP susceptible larvae treated with OP.     

Tick saliva inhibits differentiation, maturation and function of murine bone-marrow-derived dendritic cells

Haematophagous arthropod vectors such as mosquitoes, tsetse flies, sandflies and ticks have evolved salivary immunomodulatory factors that prevent the vertebrate host from rejecting them meanwhile enhancing pathogen transmission. As dendritic cells (DC) play a major role in host immune responses, we studied the effects of Rhipicephalus sanguineus tick saliva on DC differentiation and maturation. Flow cytometry analysis revealed that the addition of saliva to bone marrow cells inhibits the differentiation of DC and decreased the population of differentiated immature DC, increasing the levels of major histocompatibility complex (MHC) class II while not altering the expression of costimulatory (CD40, CD80 and CD86) and adhesion (CD54) molecules. Furthermore, maturation of DC stimulated by lipopolysaccharide (LPS) in the presence of saliva resulted in a lower expression of costimulatory molecules, but did not alter the up-regulation of MHC class II and CD54. The lipopolysaccharide (LPS)-matured DC cultured with saliva also presented reduced production of interleukin-12, whereas interleukin-10 production was unaltered. Assessment of the function of DC cultured with tick saliva revealed them to be poor stimulators of cytokine production by antigen-specific T cells. Our data indicate a novel modulatory role for the saliva of arthropod vectors at an initial step of the immune response through the inhibition of differentiation and maturation of DC into functional antigen-presenting cells.     

Rocky Mountain Spotted Fever in a Large Metropolitan Center,Mexico–United States Border, 2009–2019

Epidemic levels of Rocky Mountain spotted fe­­­ver (RMSF) have persisted in Mexicali, Mexico, since the initial outbreak was first reported in December 2008. We compared clinical and epidemiologic data of cases in Mexicali during 2009–2019 between patients with an IgG titer reactive with Rickettsia rickettsii bacteria by indirect immunofluorescence antibody (IFA) assay and those who demonstrated DNA of R. rickettsii in a whole blood sample when tested by PCR. We identified 4,290 patients with clinical and epidemiologic features compatible with RMSF; of these, 9.74% tested positive by IFA and 8.41% by PCR. Overall, 140 patients died (11-year case-fatality rate 17.97%). Substantial differences in the frequency of commonly recognized clinical characteristics of RMSF were identified between PCR-positive and IFA-positive cases. The Mexicali epidemic is unique in its size and urban centralization. Cases confirmed by PCR most accurately reflect the clinical profile of RMSF.