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PubMed1984

The immunization of calves against heartwater: subsequent immunity both in the absence and presence of natural tick challenge.

Cattle, vaccinated as calves with Cowdria ruminantium-infected tick stabilate, were challenged 6, 12 and 24 months later. In the absence of tick challenge, vaccination of calves induced a partial immunity against subsequent challenge at 12 and 24 months. In animals exposed to ticks, the resistance was no better than that of control, unvaccinated cattle. When they were challenged at 6 months of age there was no difference between vaccinated and unvaccinated calves, either in the absence or presence of tick challenge, and all the animals manifested a high degree of natural resistance. This study therefore suggests that the value of vaccinating Afrikander-cross calves in heartwater endemic areas should be further investigated. The indirect fluorescent antibody (IFA) test proved to be a valuable means of monitoring the serological response of vaccinated animals and detecting the sero-conversion of animals exposed to tick infection. On one hand, there was good correlation between the febrile reaction and the results of the IFA test on the sera of vaccinated and control cattle challenged with the heartwater agent, in that all sero-positive animals were resistant to challenge. On the other hand, though, a considerable percentage of the animals that were serologically negative were also resistant to challenge.

Age Factors↗
PubMed1999

[Three Swedish cases of African tick-bite fever. Can our native Rickettsia species cause disease in humans?].

The article consists in a report of three cases of African tick-bite fever in Swedish tourists returning from brief visits to South Africa. The clinical course included eschar, regional lymphadenopathy, fever and, in two cases, maculopapular rash. Two cases were characterised by significant increases in anti-Rickettsia conorii IgG and IgM antibody titres. However, the aetiological agent was assumed to be Rickettsia africae, based on reports by others and the widespread serological cross-reactivity among spotted fever Rickettsia spp. The third case was diagnosed on clinical grounds. During the past ten years, 50 per cent (41/80) of cases diagnosed serologically as rickettsial (R. conorii antigen) spotted fever at the Swedish Institute for Infectious Disease Control were associated with travel to South Africa. Parallels are drawn to the recent finding of R. helvetica in Swedish ticks (Ixodes ricinus), and the possibility of its pathogenicity to humans is discussed, though no such clinical cases have been reported to date.

Adult↗
PubMed1999

Variability in the 28-kDa surface antigen protein multigene locus of isolates of the emerging disease agent Ehrlichia chaffeensis suggests that it plays a role in immune evasion.

Infections caused by rickettsial pathogens persist in vertebrate hosts for long periods of time, despite the active host immune response. We recently described the multigene locus encoding 28 kDa surface antigen proteins (28 kDa SAPs) for two closely related rickettsials, Ehrlichia chaffeensis and Ehrlichia canis (Reddy, G. R., et al. (1998) Biochem. Biophys. Res. Commun. 247, 636-643), that share extensive structural homology to antigenic variant surface protein genes of Neisseria and Borrelia species. In this study, we describe motifs for recombinase binding sites and a high frequency of repeat elements in the cloned 28 kDa SAP genes. The locus for two newly established E. chaffeensis isolates also was characterized, and immunological specificity of the 28 kDa SAPs was investigated. The study identified variant forms of the 28 kDa SAPs and extensive restriction fragment length polymorphisms among isolates. The molecular data suggest that the locus is influenced by short-term evolutionary changes such as genetic recombinations leading to the generation of antigenic variants. Antigenic variation could contribute to the mechanism of immune evasion and the emergence of new diseases.

Amino Acid Sequence↗
PubMed1982

Macrophages in resistance to rickettsial infection: strains of mice susceptible to the lethal effects of Rickettsia akari show defective macrophage Rickettsicidal activity in vitro.

Activation of macrophages was assessed in strains of mice inoculated intraperitoneally with 1,000 times the 50% lethal dose of Rickettsia akari. Macrophages from mice resistant to R. akari infection (C3H/HeN, C57BL/10J, and BALB/cN) were nonspecifically tumoricidal 2 to 4 days after rickettsial inoculation. Moreover, these macrophages were microbial for R. akari in vitro; cells were resistant to infection with the bacterium and were capable of killing intracellular rickettsiae. In contrast, macrophages from strains of mice susceptible to R. akari (C3H/HeJ, C57BL/10SnCR, and A/J) failed to develop nonspecific tumoricidal activity over the course of lethal disease and became infected with R. akari in vivo within 2 days of rickettsial inoculation. Macrophages from uninfected mice of strains susceptible to R. akari also could not be activated for rickettsicidal or tumoricidal activities by treatment with macrophage-activating agents (Mycobacterium bovis BCG) in vivo or by treatment with lymphokines in vitro.

Animals↗
PubMedDate not supplied

Etiology and outcome of fever after a stay in the tropics.

BACKGROUND: Information on epidemiology and prognosis of imported fever is scarce and almost exclusively limited to hospital settings. METHODS: From 2000 to 2005, all travelers presenting at our referral outpatient and inpatient centers with ongoing fever within 12 months after a stay in the tropics were prospectively followed. Case definitions and treatment were based on international recommendations. Outcome was assessed by at least 1 follow-up consultation or telephone call within 3 months after initial contact. RESULTS: A total of 1842 fever episodes were included, involving 1743 patients. Regions of exposure were mainly sub-Saharan Africa (68%) and the Southeast Asia-Pacific region (12%). Tropical diseases accounted for 39% of all cases and cosmopolitan infections for 34%. Diagnosis often remained unknown (24%). The pattern of tropical diseases was mainly influenced by the travel destination, with malaria (35%, mainly Plasmodium falciparum) and rickettsial infection (4%) as the leading diagnoses after a stay in Africa; dengue (12%), malaria (9%), and enteric fever (4%) after travel to Asia; and dengue (8%) and malaria (4%) on return from Latin America. Disease pattern varied also according to the category of travelers, the delay between exposure and fever onset, and the setting. Hospitalization was required for 503 fever episodes (27%). Plasmodium falciparum malaria accounted for 36% of all admissions and was the only tropical cause of death (5 of 9 patients). Fever of unknown cause had invariably a favorable outcome. CONCLUSION: The clinical spectrum of imported fever is highly destination specific but also depends on other factors. Plasmodium falciparum malaria was the leading cause of mortality in the study population.

Adolescent↗
PubMed2002

Molecular diagnosis of theileriosis and heartwater in bovines in Africa.

The advent of the polymerase chain reaction (PCR) coupled with the specificity of deoxyribocucleic acid (DNA)-DNA hybridization has led to the development of specific and sensitive molecular diagnostic tests to detect and characterize the organisms that cause theileriosis and heartwater. Theileriosis is a widespread disease of wild and domestic ruminants caused by apicomplexan parasites of the genus Theileria. Species-specific variations in small subunit ribosomal ribonucleic acid genes (SSUrRNA) have been used to develop probes that can distinguish between Theileria species such as T. parva, T. annulata, T. mutans, T. buffeli and T. taurotragi. Routine application of this test has led to the discovery of previously unknown species, such as Theileria sp. (buffalo) which is apparently apathogenic to both buffalo and cattle, and Theileria sp. (sable) which is pathogenic to sable and possibly also to roan antelope. In addition, characterization probes located in the internal transcribed spacer (ITS) can be used to distinguish between most isolates of the causative agents of East Coast fever (T. p. parva) and Corridor disease (T. p. lawrencei). Heartwater is an economically important disease of livestock and some wild ruminants, caused by the intracellular rickettsial parasite Ehrlichia (ex Cowdria) ruminantium. DNA probes used to detect and characterize E. ruminantium isolates include SSUrRNA (16S) probes, the pCS20 probe and map1 probes. A panel of eight 16S probes has been developed for the detection of E. ruminantium and related Ehrlichia species. There are probes for 5 different E. ruminantium genotypes, one which will detect all 5 of these genotypes, one to detect any Ehrlichia species other than E. ruminantium, and one for any Anaplasma species. The pCS20 probe is specific for E. ruminantium and is the most sensitive of the probes for E. ruminantium detection, but it is not able to distinguish among the different genotypes. The map1 gene has also been used for diagnosis, but the extensive polymorphism of this gene means that it is most useful for characterization of different genotypes of the parasite. Routine application of these tests has led to the discovery of new genotypes that are probably not E. ruminantium but are probably new species of Ehrlichia.

Animals↗
PubMed1975

Biohazards in the field of microbiology.

Eighty cases of laboratory infection observed in our institute during 25 years were summarized. They were mostly research workers. Cases include not only manifestation of disease but also incidence of allergic responses. Causal agents were viral 22, rickettsial 14, bacterial or fungi 33, and toxin 11. Air contamination was considered to be the main cause of the above biohazard. Therefore, most of those accidents must be avoided by careful installation of the laboratory. Special attention should be given in laboratories where field specimens are treated and experimental animals housed. It was pointed out that most of the autopsy halls in Japan are little equipped to protect biohazard.

Bacterial Infections↗
PubMed1983

The histology of "taches noires" of boutonneuse fever and demonstration of Rickettsia conorii in them by immunofluorescence.

The recent increase in the incidence of boutonneuse fever in Italy provided the opportunity to study the pathology of six "taches noires," the lesions at the site of tick bite. The center of the lesion has either an ulcer or an area of necrosis of the epidermis and superficial dermis; in some cases the epidermis is intact. The alterations are mainly in the dermis and subcutaneous tissues where the small vessels show endothelial swelling and intramural and perivascular oedema and inflammation with macrophages, lymphocytes and smaller numbers of plasma cells, PMNs and eosinophils. In a few small arteries and fewer veins there are either nonocclusive mural or occlusive thrombi; there is no spatial or quantitative correlation between thrombosis and necrosis. We propose that cutaneous necrosis results from severe injury to many small vessels. Rickettsiae which had not been previously observed in "taches noires" were demonstrated in blood vessels by immunofluorescence, a finding that may be used as a means for early aetiological diagnosis of the disease. The "tache noire" is an excellent human model for localized rickettsial injury.

Adult↗
PubMed2006

Phylogenetic analysis of Anaplasma marginale strains from Paraná State, Brazil, using the msp1alpha and msp4 genes.

Anaplasma marginale is an obligate intraerythrocytic rickettsial pathogen (order, Rickettsiales: family, Anaplasmataceae) that causes bovine anaplasmosis. This disease is widely distributed in tropical and sub-tropical regions of the world and causes important economic losses to cattle production. Major surface protein (MSP)1a (msp1alpha gene) is one of the six MSPs identified on A. marginale from cattle, whose sequence and size vary according to the number of tandem 28- to 29-amino acid repeats. This study characterized the msp1alpha and msp4 genes obtained from three distinct Brazilian herds from the State of Paraná. Three strains of the msp1alpha and one strain of the msp4 gene were sequenced. The strains evaluated revealed PCR products of different size, representing three, five and six internal repeats. Sequence analyses confirmed the number of tandem sequence copies and revealed a high degree of sequence identity with strains from other Brazilian States, as well as strains from the USA, Europe and Israel. The msp1alpha DNA and amino acid sequences from A. marginale and DNA sequences of msp4 strains did not reveal distinct phylogeographical segregation. However, the amino acid sequences of msp4 demonstrated definite phylogeographical relationship. These results suggest that the amino acid sequences of msp4 should be used for phylogenetic identification of A. marginale strains and may be an important tool for the epidemiology and control of anaplasmosis. Additionally, the close similarity of the Paraná strains of A. marginale with strains from USA, Europe and Asia may reflect the introduction of these genes during the development of the Brazilian bovine herd.

Amino Acid Sequence↗
PubMed2004

Etiologies of acute undifferentiated febrile illness in Thailand.

BACKGROUND: Acute pyrexia of unknown origin (Acute PUO) was reported to affect approximately 200,000-400,000 patients each year reported by the national Annual Epidemiological Surveillance Report. The patients usually present with fever of less than two-week duration and non-specific symptoms such as malaise, myalgia, headache and loss of appetite. Its mortality rate is less than 0.02 percent. It would be interesting to find the etiologies and propose a management plan if the etiologies are discovered. OBJECTIVE: This prospective epidemiologic study aimed to discover the etiologies of acute undifferentiated febrile illness in a tropical region like Thailand. SUBJECTS AND METHOD: Ten community-based hospitals were chosen as representatives in each part of Thailand to enroll patients into the study. Patients aged over two years old who presented with fever at the participating hospitals during year 1991-1993 were eligible for the study. Entry criteria of acute undifferentiated febrile illnesses (AUFI) included oral temperature over 38.3 degrees C within the last 24 hours, duration of fever ranging from 3-14 days, no specific single organ involvement by history taking and physical examination, normal or non-specific results of the following investigations: complete blood count, thick film for malaria, urinalysis and chest roentgenogram. The patients were hospitalized and a preset diagnostic protocol was performed. Other diagnostic procedures deemed necessary by attending physicians were perform. Patients were followed up within one month after hospital discharge. RESULTS: 1,240 patients were enrolled but only 1,137 case records and results of the serological tests were available for analysis. Etiologies could be found in 471 cases (38.7%). Primary bacteremia was detected in 36 cases (3.2%). E. coli, streptococci, salmonella, Enterobacter spp. and S. aureus were the five most common blood isolates. Serological studies revealed positive results for scrub typhus (7.5%), influenza (6.0%), dengue fever (5.7%), murine typhus (5.3%), enteric fever (1.9%), chikunkunya infection (1.1%), leptospirosis (1.1%) and melioidosis (0.9%). Thirteen cases succumbed (1.1%) in this study. CONCLUSION: The etiologies in the majority (61.3%) of AUFI remained unknown. Rickettsial infection, influenza and dengue fever are the most common identifiable diseases in a tropical country like Thailand especially during the rainy season. A management guideline for diagnosis and treatment of the AUFI with emphasis on primary bacteremia and antimicrobial-treatable AUFI was proposed.

Acute Disease↗
PubMed2004

[Marseille fever imported from Spain].

The authors are presenting a case of young female with Marseille fever contracted in Spain. The clinical manifestation of the illness was characterized by fevers, exanthema, headache and a typical skin rash ("the black spot") and prompted the authors to strongly consider the diagnosis of Marseille fever and to initiate appropriate antibiotic therapy. The diagnosis was confirmed later by serology. The article introduces new taxonomy of Rickettsial species and presents an overview and epidemiological aspects of specific diseases caused by them. The clinical manifestation, diagnosis and treatment of Marseille fever are discussed in greater detail.

Adult↗