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Summary: The investigation included three aspects:1.the
overallseroprevalence of antibodies to Rickettsia conorii,
Coxiellaburnetii and Rickettsia typhi;2. clinical characteristics of
therickettsioases, and 3.investigation of ecological andentomological
factors of the rickettsial diseases.
Ad 1. A seroepidemiological survey was performed on a group of982 healthy
blood donors and other individuals of variousprofessions, wtih no known
history of any rickettsial diseases ortick bite, living in the Adriatic
coastal region including Istra(Pula, Umag, Pazin, Labin, Poreč, Buje),
n=85; Rijeka, n=90;island Pag, n=85; Zadar, n=380; Šibenik, n=ll9;, Split,
n=99 andDubrovnik, n=l24.
Sera were tested by indirect immunofluorescence assay (IFA).
The results showed an endemic presence of the three rickettsiaein the area,
with average prevalence rate for C.burnetiiantibodies of 23.67%, for
R.conorii of 19.95% and for R.typhi of
l3.1%. The highest prevalence rate of R.conorii and C.burnetiiantibodies
was found in the Zadar area (4l.6% and 36.9%,respectively) and for R.typhi
antibodies in the Split area(33.3%). In general, the lowest overall
prevalence rate was notedon the island Pag (R.conorii l.2%, C.burnetii 2.3%
and R.typhi3.5%) whoile antibodies to R.typhi were practically absent in
thesera from Istra and Dubrovnik (O% and O.8%, respectively).
Ad 2. The clinical spectrum of Mediterranean spotted fever (MSF)was
prospectively evaluated in the North Dalmatian (Zadar) area.
The classic clinical feature of MSF was predominant, with
fever,maculopapulous rash and headache. The pathognomonic skin lesion"tache
noire" was present in l6 cases (26.2%). We also noticed agrat number of
unusual clinical manifestations as nodous, annularand infectious erythema,
urticarial rash, oculoglandualrParinaud's syndrome, relapsing rash. The
highest incidence of thedisease was in spring and summer, although it
even in winter. The highest was noticed in children (24%). Inmost of cases
the MSF intensity was moderate, but in threepatients it was severe.
Particularly, a high proportion ofasymptomatic infections (seroconversion)
in 30 of 86 patients(35%) with anamnesis of an antecendents tick bite must
beemphasized. In 60 patients the diagnosis was also confirmed bydirect
immunofluorescent assay, which proved to be enoughsensitive and specific,
and reliable in early diagnosis of MSF.
These results showed not only the width of clinical spectrum ofMSF in the
Zadar area but also the possibility of an antigenicvariant of R.conorii
that differs from those circulating in otherparts of Mediterranean basin.
Besides, the results obtainedemphasize the problem of inadequate assesment
of unreported/undiagnosed cases of MSF (in general, it has been estimated
thatunlisted cases outnumbered recorded ones by nearly 3-4 to l).
Ad 3. The investigation of ecological and entomological factors of
rickettsial diseases showed that North Dalmatia has idealclimatic, biotic
and abiotic conditions for maintainingrickettsiae, a very high
seroprevalence of antibodies to spottedfever group of rickettsiae in dogs
(55.5%) and sheep (77.2%) anda very high percentage of ticks infected with
rickettsiae (thepredominant species of 10 different tick species
wasRhipicephalus sanguineus, with infection rate of 70.5%).
Research goals: Rickettsiae are obligate intracellular bacteria
which are closely associated with ticks, mites, lice, flies, chiggers. In
recent years the number of new rickettsial strains isolated from humans or
from ticks throughout the world has increased. At the same time the known
areas of distribution of the well known rickettsial species have been
changing. In the eastern coast of Adriatic sea, as in many parts of the
world, rickettsioses had part due to difficulty in the clinical diagnosis
and in part to the frequent lack of availability of specific laboratory
diagnostic tests. Since l985, there has been remarkable increase in the
number of reported cases of Mediterranean spotted fever along the Adriatic
coast. In addition, our previous investigation documented the presence of
antibodies to spotted fever group rickettsiae in healthy population too.
Finally, the ecology of this area provides in principle excellent
protection for rickettsial vectors and/or reservoirs. Specific Aims:
1. to determine the epidemiology of human exposure and illness caused by
rickettsiae by means of specific serologic assays, 2. to
characterize the clinical spectrum of rickettsioses along the eastern coast
of Adriatic sea, particularly of Mediterranean spotted fever, and
3. to survey the ecosistem of coastal Croatia for the arthropod vectors and
reservoirs of R.conorii by rickettsial isolation and identification and
presence of antibodies in mammals. This study performed under
this fellowship will formed a major contribution to the biomedical
knowledge of the epidemiology, clinic and ecology of R.conorii and other
rickettsiae in our region.
COOPERATION - INSTITUTIONS
Name of institution
: Medicinski fakultet Ljubljana,Mikrobiološki
institut Type of institution: Economical/Production City: 61000 - Ljubljana, Slovenija