Dieter Hassler

Transmission risk of Borrelia burgdorferi sensu lato from Ixodes ricinus ticks to humans in southwest Germany

The risk of Borrelia burgdorferi infection and the value of antibiotic prophylaxis after tick bite are controversial. In this study, performed in two areas of southwestern Germany, ticks were collected from 730 patients and examined by the polymerase chain reaction (PCR) for B. burgdorferi. To assess whether transmission of B. burgdorferi occurred, the patients were clinically and serologically examined after tick removal and during follow-up examinations. Data from all tick bites gave a total transmission rate of 2.6% (19 patients). Eighty-four ticks (11.3%) were PCR positive. Transmission occurred to 16 (26.7%) of 60 patients who were initially seronegative and could be followed up after the bite of an infected tick. These results indicate that the transmission rate from infected ticks in Europe is higher than previously assumed. Examination of ticks and antibiotic prophylaxis in the case of positivity appears to be indicated.

TICK INFESTATION PATTERNS AND PREVALENCE OF BORRELIA BURGDORFERI IN TICKS COLLECTED AT A VETERINARY CLINIC IN GERMANY

A total of 4803 domestic and wild animals which were presented for examination at a veterinary clinic in north Baden, Germany over a period of 1 year were examined for tick infestation. A total of 434 nymphal and adult ticks were collected from 175 hosts. Ticks found belonged to the species Ixodes ricinus (385), Ixodes hexagonus (48), and Ixodes ventalloi (one). The polymerase chain reaction was used to examine 132 I. ricinus and 21 I. hexagonus for the presence of Borrelia burgdorferi. Twenty-two per cent of adult I. ricinus were infected as were one female and one larval I. hexagonus.

Evaluation of the detection of Borrelia burgdorferi DNA in urine samples by polymerase chain reaction.

SummaryIt is difficult in some cases to identify an infection caused byBorrelia burgdorferi and to monitor the effect of therapy. Seropositivity will persist even after successful treatment and therefore may suggest ongoing infection. For direct detection ofB. burgdorferi DNA in human urine samples, the polymerase chain reaction (PCR) was evaluated. A published primer system was selected, which amplifies a 259 bp fragment from the gene encoding the 23S rRNA. The lower detection limit of the primer system was 10 fg of extractedB. burgdorferi DNA. Several methods for the pretreatment of urine sample were tested. Of these, the Geneclean® kit (Bio 101, USA) showed the best results. A total of 114 urine samples from 74 patients belonging to three clinical groups was investigated: (i) 51 samples from 26 patients with active Lyme disease, (ii) 36 samples from 27 patients with previous infection but no symptoms at the time the urine was collected, and (iii) 27 samples from 21 seronegative control patients without Lyme disease.B. burgdorferi DNA was detected in 25 urine samples of 17 patients with active disease, whereas 26 samples from this group of patients were negative. Only one asymptomatic case with previous infection showed a positive result, and the urine samples of the patients without Lyme disease were uniformly negative. Two of four patients from whom samples before and directly after onset of therapy were available converted from negative to positive PCR results after initiation of therapy, accompanied by the symptoms of a Jarisch-Herxheimer reaction. It can be concluded from these results that a positive PCR from urine is with high probability an indicator of active Lyme disease. On the other hand, as only 17 of the 26 patients with active infection were positive, a negative PCR result does not exclude active infection.ZusammenfassungIn manchen Fällen ist es schwierig, Infektionen mitBorrelia burgdorferi zu diagnostizieren und den Effekt einer Therapie abzuschätzen. Seropositivität bleibt selbst nach erfolgreicher Therapie bestehen und kann deshalb ein weiterbestehendes Infektionsgeschehen vortäuschen. Zum Direktnachweis vonB. burgdorferi-DNA in menschlichen Urinproben wurde das Verfahren der Polymerase-Kettenreaktion (PCR) evaluiert. Zur Anwendung kam ein Primersystem, dessen Zielsequenz auf dem Gen für die 23S rRNA liegt (Schwartz et al., J. Clin. Microbiol. 30: 3082–3088; 1992). Die Nachweisgrenze des Primersystems betrug 10 fg an extrahierter DNA vonB. burgdorferi. Zur Probenvorbereitung von Urinproben wurden mehrere Methoden getestet. Davon erwies sich das Geneclean® Kit (Fa. Bio 101) als am besten geeignet. Damit wurden insgesamt 114 Urinproben von Patienten aus drei klinischen Gruppen untersucht: (i) 51 Proben von 26 Patienten mit aktiver Lyme-Borreliose, (ii) 36 Proben von 27 symptomlosen Patienten mit vorangegangener Infektion, und (iii) 27 Proben von 21 seronegativen Kontrollpatienten ohne Lyme-Borreliose. Mit Hilfe der PCR bei Probenaufbereitung mit Geneclean® gelang ein Nachweis von Borrelien-DNA in 25 Proben von 17 Patienten mit aktiver Erkrankung, während 26 Proben aus dieser Gruppe negativ waren. Ein asymptomatischer Fall zeigte ein positives Resultat, und die Proben der Patienten ohne Lyme-Borreliose waren einheitlich negativ. Zwei von vier Patienten, von denen Urinproben vor und direkt nach Therapie verfügbar waren, zeigten eine Konversion von negativen zu positiven PCR-Resultaten nach Therapiebeginn, was auf einen Erregerzerfall und vermehrte Ausscheidung von Borrelien-DNA schließen läßt. Die Positivität unter Therapie war korreliert mit dem klinischen Auftreten einer Jarisch-Herxheimer-Reaktion. Die vorliegenden Ergebnisse lassen schließen, daß zwar ein negatives PCR-Ergebnis nicht gegen Krankheitsaktivität spricht, da nur 17 der 26 Patienten mit aktiver Erkrankung positive Resultate zeigten, jedoch daß ein positives PCR-Resultat als Hinweis auf eine aktive Infektion gewertet werden kann.