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At least 163 records · Page 9Linked to original sources
PubMed1991

Tick-bite fever in Zimbabwe. Survey of antibodies to Rickettsia conorii in man and dogs, and of rickettsia-like organisms in dog ticks.

As part of a study of tick-bite fever in Zimbabwe, the prevalence of antibodies to Rickettsia conorii in dogs and humans was examined. Blood samples were obtained from 184 dogs in different parts of the country and tested by indirect immunofluorescence. In all, 150 (82%) were positive at a titre of 1/40 or higher. Dogs from the south and east of the country showed very high seroprevalence compared with dogs from the main urban centre, Harare. Human serum was obtained from blood donors, from people attending clinics with non-febrile illness and from agricultural workers. Antibodies to R. conorii were found in a high proportion of samples from the south and east, with 100% of blood donor samples in one area being positive. As with the dogs, a much lower proportion of samples from Harare were positive. The exact role of dogs and their ticks (Rhipicephalus sanguineus, R. simus and Haemaphysalis leachi) in the epidemiology of human tick-bite fever remains unclear, since dog ticks were seldom found to harbour rickettsia-like organisms and man is not one of their preferred hosts. While dogs may be of little importance in disease transmission, their value as sentinels of spotted-fever group rickettsias in the environment was confirmed.

Animals↗
PubMed1982

Corticosteroid therapy of tick-borne fever.

Treatment of sheep infected with tick-borne fever with betamethasone injection BP abated thermal reactions and induced neutrophilia. The therapeutic effects were, however, transient and the haematological and thermal changes returned to pretreatment levels after 24 hours.

Animals↗
PubMed1987

Tick-bite fever in pregnancy. A case report.

Despite the frequency of tick-bite fever in southern Africa and its doubtless occurrence in pregnancy, this report documents the first case in a pregnant woman. Consequently, the natural history of tick-bite fever in pregnancy and concomitant placental involvement must be regarded as conjectural. Accordingly a register has been opened by the Department of Obstetrics and Gynaecology, University of the Witwatersrand, for recording similar cases. At this stage of our knowledge, erythromycin 500 mg 6-hourly until 3-5 days after defervescence is the therapy of choice for such patients.

Adult↗
PubMed1966

Electron microscopy of tick-borne fever agent in bovine and ovine phagocytizing leukocytes.

Tuomi, Jaakko (University of Helsinki, Helsinki, Finland), and C.-H. von Bonsdorff. Electron microscopy of tick-borne fever agent in bovine and ovine phagocytizing leukocytes. J. Bacteriol. 92:1478-1492. 1966.-Two strains of tick-borne fever agent, one more virulent to cattle and the other more virulent to sheep, were studied in thin sections of leukocyte concentrates of an affected calf and sheep, respectively. The calf was partially immune from previous infections. To obtain leukocyte concentrate, erythrocytes were lysed by ammonium chloride solution. Glutaraldehyde fixation and osmium tetroxide postfixation were used. Agent particles were detected in neutrophil and eosinophil granulocytes (occasionally also in monocytes) inside cytoplasmic vacuoles. The preparation from the sheep revealed that the tick-borne fever agent has a life cycle; it appeared as large particles, intermediate forms, and small particles. In the preparation from the calf, only large particles were observed, probably as a result of partial immunity. Large particles had a cell wall, plasma membrane, cytoplasm with ribosome-like granules, and nucleoid. They were often elongated, bearing closer resemblance to rickettsiae than to psittacosis-lymphogranuloma-trachoma (PLT) agents. The arrangement of large particles in vacuoles was variable and provided an explanation for the different forms of light microscopic tick-borne fever bodies. The intermediate forms and small particles resembled those of PLT organisms. Release of particles occurred by rupture of inclusions. In the calf also extrusion of whole inclusions was observed. This phenomenon was thought to reflect increased resistance of the cells. The large particle was considered to be the usual infective form of the agent. A middle-ground position of the agent between the genus Rickettsia and the PLT group is suggested.

Animals↗
PubMed1983

Tick-bite fever in South Africa. The occurrence of severe cases on the Witwatersrand.

Tick-bite fever, the variety of tick typhus occurring in southern Africa, is caused by Rickettsia conori var. pijperi and is transmitted by hard or ixodid ticks. It is usually a mild disease, especially in children and young adults, but in middle-aged and elderly patients (and sometimes in young adults) it may assume a severe form. This is characterized by high fever, severe headache, delirium, stupor and occasionally coma, and a profuse maculopapular rash which becomes haemorrhagic and is associated with petechiae in the skin and later, but rarely, by the development of gangrene of the fingers and toes. During these severe attacks the central nervous system may be involved and marked disorders of liver and kidney function sometimes lead to kidney failure and the need for treatment and dialysis in an intensive care unit. Three illustrative cases are described in which diagnosis was delayed. One patient died; 2 patients responded to administration of tetracycline. The danger of allowing tick-infested dogs onto one's bed is stressed. Infections transmitted by dog ticks tend to be more severe than those acquired via ticks from the bushveld, possibly because they so often occur in middle-aged and elderly patients. Serological tests have recently indicated that there are antigenic differences between 'suburban' and 'bushveld' strains; these clearly require further study.

Adult↗
PubMed1993

The effects of tick-borne fever on the susceptibility of ovine polymorphonuclear cells to P. haemolytica cytotoxin.

Tick-borne fever predisposes sheep to secondary infections by Pasteurella haemolytica. Polymorphonuclear (PMN) cells obtained from sheep 2 to 7 days after the onset of parasitaemia due to Cytoecetes phagocytophila, the causative agent of tick-borne fever, were significantly more susceptible in vitro to the cytotoxin of P. haemolytica than PMN obtained from age-matched control sheep.

Animals↗
PubMed1984

Treatment of tick-bite fever with erythromycin.

Because of the occasional need for an alternative drug for the treatment of tick-bite fever, a study of the value of erythromycin for the variety of tick-borne typhus fever occurring in southern Africa was undertaken. In guinea-pigs erythromycin 125 mg/kg for 5 days largely prevented the fever and other signs of the infection, but did not prevent the serological reaction as determined by the rickettsial complement fixation test. A series of 17 human patients were treated for 4 days with erythromycin 500 mg 6-hourly for adults and 30-50 mg/kg/d in 4 divided doses for children. Eleven patients appeared to respond favourably. It was concluded that erythromycin does not have as specific a value as tetracycline in the treatment of tick-bite fever, but that when tetracycline is contraindicated erythromycin is a useful alternative drug.

Adolescent↗
PubMed1997

African tick-bite fever. An imported spotless rickettsiosis.

OBJECTIVES: To characterize the clinical presentation and course of African tick-bite fever, a recently rediscovered rickettsiosis caused by Rickettsia africae (a new species within the spotted fever group of rickettsiae), to establish its relationship with Amblyomma tick species, and to discuss its role in the etiology of fever in patients who are returning from the tropics. PATIENTS: Seven patients who returned from Zimbabwe of the Republic of South Africa and presented with fever. METHODS: Cases were recognized clinically by the presence of multiple taches noire and were diagnosed as having a rickettsial infection by identification of the organisms in circulating endothelial cells. The causative role of R africae was further demonstrated using cross-absorption and immunoblotting of patients' serum samples and isolation of the agent from blood and skin biopsy specimens. Isolates were characterized using the restriction fragment length polymorphism-polymerase chain reaction and sequence analysis of the gene that encodes for the 190-kd Rickettsia-specific antigen. RESULTS: All 7 patients presented with fever and multiple taches noire. Further physical examination of patients revealed lymphadenopathy, lymphangitis, and edema, but there were virtually no signs of a rash. These findings are characteristic of R africae-infected patients and are distinct from those observed in patients with Rickettsia conorii-induced Mediterranean spotted fever. All 7 patients were infected with R africae as demonstrated by immunoblotting or isolation of the agent, and all were cured. CONCLUSIONS: With increasing international travel, a need for the recognition of rickettsial diseases by physicians is becoming more important. Tick-bite fever, a disease caused by R africae and transmitted by Amblyomma ticks, is characterized by multiple taches noire, lymphadenopathy, lymphangitis, and edema, but no rash or a discrete rash. It is a frequent but benign disease that physicians should consider when presented with febrile patients returning from southern Africa.

Adult↗
PubMed2003

Systemic inflammatory responses in African tick-bite fever.

Information regarding the inflammatory response in African tick-bite fever (ATBF), an emerging spotted-fever-group rickettsiosis, in international travelers to sub-Saharan Africa, is scarce. Plasma/serum levels of von Willebrand factor (vWF), soluble (s) E-selectin, tumor necrosis factor-alpha, interleukin (IL)-6, interferon-gamma, IL-10, IL-13, IL-8, RANTES, macrophage inflammatory protein-1alpha, and C-reactive protein were studied, at both first presentation and follow-up, in 15 patients with travel-associated ATBF and in 14 healthy travelers who served as control subjects. Our main and novel findings are the following: (1) patients with ATBF had increased levels of vWF and sE-selectin, with a subsequent decrease at follow-up; (2) with the exception of IFN-gamma, levels of cytokines and chemokines were also increased in these patients at the first presentation; and (3) IL-10 and IL-13 tended to increase during follow-up, whereas most of the inflammatory cytokines decreased. The induction of these mediators and the balance between them may be critical both for the regulation of inflammation and for protective immunity in ATBF.

Adult↗
PubMed1990

Severe tick-bite fever in young children. A report of 3 cases.

Tick-bite fever in young children is usually a mild illness with few complications and no mortality. That it may assume a severe form is illustrated by the occurrence of 3 cases admitted to Johannesburg Hospital within 1 week in which 2 patients, 3 and 5 years old respectively, had severe involvement of the central nervous system with epileptiform fits and deep coma and loss of power of speech on recovering consciousness. The third patient, aged 5 years, developed an incipient haemorrhagic state as well as serious involvement of the central nervous system. The severe form of the disease in these patients appears to have been due to unusually virulent strains of Rickettsia conorii, probably acquired from dog ticks in their homes. All patients recovered on appropriate treatment. Two regained their normal speech after many weeks while the third patient's incipient haemorrhagic state rapidly resolved.

Child↗
PubMed2001

An estimate of the economic effects of cattle tick (Boophilus microplus) infestation on Queensland dairy farms.

OBJECTIVE: To establish the cost to the Queensland dairy industry of cattle tick infestation and its control, excluding the costs incurred from control measures directed specifically at tick fever and morbidity and mortality arising from tick fever. STUDY DESIGN: Economic models are described that have been based on empirical data relating to liveweight and milk yield loss, and on a survey of control practices and tick infestation. The first two models were designed to estimate costs of control and losses resulting from tick infestation on a single dairy farm. The third model developed estimates of the cost of tick infestation for each of four regions within the tick-infested area of Queensland. RESULTS: The overall cost to the Queensland dairy industry of the cattle tick (excluding the costs associated specifically with tick fever) and based on 1998 management practices, was $4,096,000 per annum. About 49% of this cost was related to the costs of control and 51% to losses in production. CONCLUSION: Cattle tick infestation represents a significant impost on dairy producers in Queensland, and although the actual cost will change as deregulation results in economic changes in the industry, infestations of ticks will continue to be expensive to control.

Animal Husbandry↗
PubMed2002

Outbreak of African tick-bite fever in six Italian tourists returning from South Africa.

In May 1999, a cluster of cases of African tick-bite fever was detected in six Italian tourists who had returned from South Africa. All of the patients had moderate fever and cutaneous eschars. Regional lymphangitis was observed in three of the patients and skin rash in two. By comparing the number of eschars with the number of detectable bite sites it was suggested that at least two-thirds of the biting vectors were capable of transmitting Rickettsia africae. The clinical course of disease was mild in all cases, and all but one of the patients recovered spontaneously before antibiotic treatment was initiated. The diagnosis of African tick-bite fever was confirmed serologically using both microimmunofluorescence and Western blot tests.

Animals↗
PubMed1999

Imported African tick bite fever: a case report.

We describe a patient with African tick-bite fever who acquired his infection while visiting rural areas of South Africa and then became sick after returning to the United States. The dominant clinical feature of his illness was the presence of multiple, ulcerated lesions (tache noires). Physicians in the United States and other non-African countries who see travelers returning from southern parts of Africa who give a history of recent tick bite and/or present with multiple, crusted or vesicular skin lesions should be alert to this diagnosis and institute treatment with doxycycline.

Aged↗
PubMed1991

Lymphocyte subpopulations in peripheral blood of sheep experimentally infected with tick-borne fever.

The lymphocyte subpopulations in the peripheral blood of normal sheep and sheep experimentally infected with Cytoecetes phagocytophila, the causative agent of tick-borne fever, were analysed by flow cytometry, using a panel of monoclonal antibodies against specific lymphocyte epitopes. Experimental infection with tick-borne fever was characterised by a significant reduction in the total number of circulating lymphocytes six days after experimental infection (P less than 0.001). This lymphocytopenia was associated with a significant reduction in the number of B (LCAp220+) and T (CD5+) lymphocytes (P less than 0.001) but there was a significant increase in the number of cells which were neither T nor B (CD5-LCAp220-) cells (P less than 0.01). The reduction in the number of T lymphocytes was due to reduced numbers of circulating CD4+ (helper) T cells, CD8+ (cytotoxic/suppressor) T cells and those with the pan T cell marker (CD5+) but without CD4 or CD8 epitopes (CD4-CD8-). All lymphocytes returned to preinoculation levels 13 to 16 days after experimental infection.

Animals↗
PubMed2004

Comparison of immunofluorescence, Western blotting, and cross-adsorption assays for diagnosis of African tick bite fever.

In testing paired serum samples from 40 consecutive cases of African tick bite fever, we detected diagnostic antibodies against spotted fever group rickettsiae in 45% of the patients by immunofluorescence assay (IFA) and in 100% of the patients by Western blotting (WB) (P < 0.01). A specific diagnosis of Rickettsia africae infection could be established in 15% of the patients by IFA and in 73% of the patients by a combination of WB and cross-adsorption assays (P < 0.01).

Adolescent↗