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Infectiousness for humans of Ixodes ricinus containing Borrelia burgdorferi
Zbl. Bakt. Hyg. A 263,473-476 (1 986)
Infectiousness for Humans of Ixodes ricinus Containing Borrelia burgdorferi HERMA N N PAUL I, H A N S-J O A CHI M G E R T H I and R UDOLF A CK ER M A N N l I
2
Department of Medica l Virology an d Epidemio logy of Vira l Diseases, Institute of Hygiene 0 -74 00 T iibingen University Hospital for Neuro logical Diseases, Department of Viro logy 0-5000 Cologne 41, FRG
Summary We stu died th e rate of transmission of Borrelia burgdorferi from ticks (Ixodes ricinus) to man under field cond itio ns in a case control study. At a ho liday camp in southern Germany 38 4 ticks were removed from 272 person s. Informat ion on sympto ms poss ibly related to Borreli a infection were obtai ned by a qu estionn aire to be sent back six weeks after the tick bite. Ticks wer e exam ined by immunoflu orescence micro scop y (1FT) for Borrel ia and 49 (12.8%) were found positive. Bloo d was obtai ned fro m 41 person s bitten by Bor relia positive and 41 age and sex matched persons bitte n by Borrelia negative ticks. Sera fro m age and sex matc hed patients of local hospi tals and clinics served as addi tio nal controls. Anti body tite rs were obtained by indirec t 1FT about 13 weeks after tick bite. Tite rs I : > 32 suggeste d recent infection and 1 : 32 immu nity. In the exposed gro up there were about half as man y persons wit h titers 1 : < 32 (n = 14) than in the co ntrol gro up (n = 27) suggesting that eithe r par t of the infected ticks was in a no n-infectious sta te or the hosts were immune. In the exposed grou p there were 46.4 % (n = 19) and in the control group, bitten by Borrelia nega tive ticks, 14.7% (n = 6) persons with titers I : > 32, but 5/ 6 of these persons in the control gro up recalled additio nal tick bites in 1984 . Only one child (in the exposed gro up) develop ed an Erythema chronicum migrans, and no other Borrel ia related man ifestat ion s were reported. Th e man ifestat ion rate of the Borrelia-related disease wa s 4% .
Introduction Diseases caused by Borreliaburgdorferi have been shown to be widely distributed in Central Europe (2). In addition, highl y suggestive sero logical evidence for a lar ge percentage of asymptomatic infections has been reported (3) but no pro specti ve investigati on s con cerning th e manifestation rate of Borreli a-related diseases nor the infectiou sness of Borrelia carrying tick s for humans have been publi shed. In this paper we communicate observations concern ing the sero logica l and clinical respon se of participants of a holid ay camp in southern Germany bitten by tick s in or der to help to clar ify th e qu estion s of infect iou sness of Borrel ia infected ticks and th e manifestat ion rate of Bor relia related disease in Eur op e.
474
H. Paul, H.-]. Gerth, and R. Ackermann
Study Population and Methods The study population consisted of two groups of children aged 6-15 years and the staff attending a holiday camp in August 1984 in southwestern Germany. Each groupnumbered about 1100 children and stayed in the camp for 12 days. The children were cared for by about 100 young adults. 272 persons - mainly children but alsomembers of the staff- consulted one of use (H. P.) for tick bites, and 384 ticks (Ixode s ricinus) in different developmental stages were removed. These 272 persons were enrolled in the study. They receiveda questionnaire concerning possible Borrelia infection related symptoms to besent back six weeks afterthe tick bite. 74.1% of the questionnaires were returned. Smears of the ticks were prepared on microscopic slides using a stereo microscope, stored at -20 °C and examined later with the direct immunofluorsecent technique using a conjugated rabbit immune serum. After obtaininginformed consent capillary bloodwasobtainedbymicrotainer (Becton Dickinson, Heidelberg FRG) from participants bitten by ticks in which Borrelia were found (group A) and stored in the refrigerator. An age- and sex matched group was formed from participants bitten by Borrelia negative ticks (group B). The average number of ticks removed from participants of group A was 2.1, of group B 1.9. A second controlgroup (group C) consisted of seraof age and sex matched patients with acute conditions received from hospitals and clinics of the University of Tubingen for diagnostic purposes. Antibodies were determined by the indirect immunofluorescent technique as described by Ackermann et at. (1).
Results and Discussion
In 49 of 394 ticks (12.8 % ) Borrelia were detected. 20 ticks (5.2%) were questionably positiv e and no further evaluation of these cases was attempted. From 41 parti cipants bitten by Borrelia containing ticks (exposed group ) blood was obtained. The results of the serological evaluation of the exposed and two control groups are shown in figure 1. There were almost equal numbers of persons with titers 1 : 32 in the exposed and the two control groups, suggesting that this titer indicates immunity. In about half of the participants of the exposed group (14 in group A as compared with 27 cases in group B) the titres remain below the threshold of the method and presumably no fresh infection has taken place. There are 46.3 % person s with titers 1 : ~ 64 in the exposed group as compared with 14.6 % and 9.8% in the control groups B and C. Actually, titers 1 : ~ 64 in the control group are probably also the result of recent infections: 5/6 of these titers in group B were found in a subgroup of 16 persons which reported at least one additional tick bite in 1984 not covered by our study (Table 1). Only one 8 1/2 year old girl belonging to the exposed group had symptoms presum ably related to Borrelia infection. She noticed redness at the neck at a site where 24 days before a Borrelia positive tick had been removed and developed a typical Erythema chronicum migrans (ECM). 13 days after the first symptoms the child was seen by one of us (H . P.) and treated with Penicillin. Three days after the beginning of the therapy, the erythema faded away. Five weeks after the ticks bite and 13 days after the beginning of ECM her sera showed an anti-Borrelia IgG titer of 1 : 256, and an IgM
Infectiousness of Borrelia Containing Ticks
475
IF antibod y titre to Borrelia b. after tick bite
•
exposed to Borrelia b. by tick bite
~
D
controls with bites of ticks without Borrelia b.
~
~
hosplt. patients with unknown expo sure
o
Co
40
20 10
32
<32
64
>
64
reclpr . titre
Fig. 1. Indirect immunofluorescent antibody titers of 41 persons from which Borrelia ticks were removed, a control group with patients bitten by ticks without detectable Borrelia and a second control group made up of sera of age- and sex matched patients of hospitals and clinics in Tiibingen.
titer of 1 : 32, eigh t weeks later the IgG titer had increased to 1 : 1024 and the IgM titer ha d fallen to 1 : < 16 . No other cases of Borrelia rela ted disease were reported fro m the 272 persons observed. Assuming that tite rs of 1 : 32 indicate immunity an d above 1 : 32 recent infection th e manifestation ra te (calculated from group A and B) was 1/25 (4 % ). It remains open the question, why on ly about half of the exposed persons with titers 1 : < 32 became infected. There is the possiblity th at part of the Borrelia-carrying ticks were in an noninfectio us sta te. On the other hand, our data p ro vide highly suggestive evidence that previous infection - as indicated by IF antibody titers of 1 : 32 - p revents reinfection and it
Table 1. Antibody titers and additional tick bites in control persons Rec. titer
<32 32 64 >64
Additional exposure
No additional exposure n
%
18 6
72.0 24.0
1 25
4.0
n
%
9 2 1 4 16
56.3 12.5 6.3 25.0
476
H. Paul, H.-J. Gerth, and R. Ackermann
cannot be excluded that our 1FT was too insensitive to detect markers of a remote but unimmunizing Borrelia infection. This suspicion is supported by the observation of one child which though being bitten by four ticks - two of them Borrelia positive and all of them engorged with blood - showed no detectable antibodies by 1FT. Use of an ELISA, however, revealed low titered anti-Borrelia antibodies (not shown). Acknowledgement Part of this work will be submitted by H. Paul in partial fulfillment of the requirements for the degree of Doctor of Medicine at the University of Tiibingen.
References 1. Ackermann, R., G. Kabatzki, H. P. Boisten, A. C. Steere, R. L. Grodzichi, S. Hartung, and U. Runne: Spirochaten-Atiologie der Erythema-chronicum-migrans-Krankheit. Dtsch. med:
Wschr. 109 (1984), 92. 2. Schmidt, R., R. Ackermann, ]. Kabatzki, H. Hartung: Epidemiologic aspects of erythema chronicum migrans disease in the Federal Republic of Germany. Second International Symposium on Lyme disease and related disorders. Vienna, Austria, September 17-19, 1985 3. Wilske, B., P. Miinchhoff, G. Schietz, V. Preac-Mursic, M. Roggendorf, and G. Zoulek: Zur Epidemiologie der Borrelia burgdorferi-Infektion. Munch. med. Wschr. 127/8 (1985), 171. H. Paul, Dept. of Medical Virology and Epidemiology of Viral Diseases, Institute of Hygiene, Silcherstr. 7, D-7400 Tubingen, FRG
Infectiousness for Humans of Ixodes ricinus Containing Borrelia burgdorferi HERMA N N PAUL I, H A N S-J O A CHI M G E R T H I and R UDOLF A CK ER M A N N l I
2
Department of Medica l Virology an d Epidemio logy of Vira l Diseases, Institute of Hygiene 0 -74 00 T iibingen University Hospital for Neuro logical Diseases, Department of Viro logy 0-5000 Cologne 41, FRG
Summary We stu died th e rate of transmission of Borrelia burgdorferi from ticks (Ixodes ricinus) to man under field cond itio ns in a case control study. At a ho liday camp in southern Germany 38 4 ticks were removed from 272 person s. Informat ion on sympto ms poss ibly related to Borreli a infection were obtai ned by a qu estionn aire to be sent back six weeks after the tick bite. Ticks wer e exam ined by immunoflu orescence micro scop y (1FT) for Borrel ia and 49 (12.8%) were found positive. Bloo d was obtai ned fro m 41 person s bitten by Bor relia positive and 41 age and sex matched persons bitte n by Borrelia negative ticks. Sera fro m age and sex matc hed patients of local hospi tals and clinics served as addi tio nal controls. Anti body tite rs were obtained by indirec t 1FT about 13 weeks after tick bite. Tite rs I : > 32 suggeste d recent infection and 1 : 32 immu nity. In the exposed gro up there were about half as man y persons wit h titers 1 : < 32 (n = 14) than in the co ntrol gro up (n = 27) suggesting that eithe r par t of the infected ticks was in a no n-infectious sta te or the hosts were immune. In the exposed grou p there were 46.4 % (n = 19) and in the control group, bitten by Borrelia nega tive ticks, 14.7% (n = 6) persons with titers I : > 32, but 5/ 6 of these persons in the control gro up recalled additio nal tick bites in 1984 . Only one child (in the exposed gro up) develop ed an Erythema chronicum migrans, and no other Borrel ia related man ifestat ion s were reported. Th e man ifestat ion rate of the Borrelia-related disease wa s 4% .
Introduction Diseases caused by Borreliaburgdorferi have been shown to be widely distributed in Central Europe (2). In addition, highl y suggestive sero logical evidence for a lar ge percentage of asymptomatic infections has been reported (3) but no pro specti ve investigati on s con cerning th e manifestation rate of Borreli a-related diseases nor the infectiou sness of Borrelia carrying tick s for humans have been publi shed. In this paper we communicate observations concern ing the sero logica l and clinical respon se of participants of a holid ay camp in southern Germany bitten by tick s in or der to help to clar ify th e qu estion s of infect iou sness of Borrel ia infected ticks and th e manifestat ion rate of Bor relia related disease in Eur op e.
474
H. Paul, H.-]. Gerth, and R. Ackermann
Study Population and Methods The study population consisted of two groups of children aged 6-15 years and the staff attending a holiday camp in August 1984 in southwestern Germany. Each groupnumbered about 1100 children and stayed in the camp for 12 days. The children were cared for by about 100 young adults. 272 persons - mainly children but alsomembers of the staff- consulted one of use (H. P.) for tick bites, and 384 ticks (Ixode s ricinus) in different developmental stages were removed. These 272 persons were enrolled in the study. They receiveda questionnaire concerning possible Borrelia infection related symptoms to besent back six weeks afterthe tick bite. 74.1% of the questionnaires were returned. Smears of the ticks were prepared on microscopic slides using a stereo microscope, stored at -20 °C and examined later with the direct immunofluorsecent technique using a conjugated rabbit immune serum. After obtaininginformed consent capillary bloodwasobtainedbymicrotainer (Becton Dickinson, Heidelberg FRG) from participants bitten by ticks in which Borrelia were found (group A) and stored in the refrigerator. An age- and sex matched group was formed from participants bitten by Borrelia negative ticks (group B). The average number of ticks removed from participants of group A was 2.1, of group B 1.9. A second controlgroup (group C) consisted of seraof age and sex matched patients with acute conditions received from hospitals and clinics of the University of Tubingen for diagnostic purposes. Antibodies were determined by the indirect immunofluorescent technique as described by Ackermann et at. (1).
Results and Discussion
In 49 of 394 ticks (12.8 % ) Borrelia were detected. 20 ticks (5.2%) were questionably positiv e and no further evaluation of these cases was attempted. From 41 parti cipants bitten by Borrelia containing ticks (exposed group ) blood was obtained. The results of the serological evaluation of the exposed and two control groups are shown in figure 1. There were almost equal numbers of persons with titers 1 : 32 in the exposed and the two control groups, suggesting that this titer indicates immunity. In about half of the participants of the exposed group (14 in group A as compared with 27 cases in group B) the titres remain below the threshold of the method and presumably no fresh infection has taken place. There are 46.3 % person s with titers 1 : ~ 64 in the exposed group as compared with 14.6 % and 9.8% in the control groups B and C. Actually, titers 1 : ~ 64 in the control group are probably also the result of recent infections: 5/6 of these titers in group B were found in a subgroup of 16 persons which reported at least one additional tick bite in 1984 not covered by our study (Table 1). Only one 8 1/2 year old girl belonging to the exposed group had symptoms presum ably related to Borrelia infection. She noticed redness at the neck at a site where 24 days before a Borrelia positive tick had been removed and developed a typical Erythema chronicum migrans (ECM). 13 days after the first symptoms the child was seen by one of us (H . P.) and treated with Penicillin. Three days after the beginning of the therapy, the erythema faded away. Five weeks after the ticks bite and 13 days after the beginning of ECM her sera showed an anti-Borrelia IgG titer of 1 : 256, and an IgM
Infectiousness of Borrelia Containing Ticks
475
IF antibod y titre to Borrelia b. after tick bite
•
exposed to Borrelia b. by tick bite
~
D
controls with bites of ticks without Borrelia b.
~
~
hosplt. patients with unknown expo sure
o
Co
40
20 10
32
<32
64
>
64
reclpr . titre
Fig. 1. Indirect immunofluorescent antibody titers of 41 persons from which Borrelia ticks were removed, a control group with patients bitten by ticks without detectable Borrelia and a second control group made up of sera of age- and sex matched patients of hospitals and clinics in Tiibingen.
titer of 1 : 32, eigh t weeks later the IgG titer had increased to 1 : 1024 and the IgM titer ha d fallen to 1 : < 16 . No other cases of Borrelia rela ted disease were reported fro m the 272 persons observed. Assuming that tite rs of 1 : 32 indicate immunity an d above 1 : 32 recent infection th e manifestation ra te (calculated from group A and B) was 1/25 (4 % ). It remains open the question, why on ly about half of the exposed persons with titers 1 : < 32 became infected. There is the possiblity th at part of the Borrelia-carrying ticks were in an noninfectio us sta te. On the other hand, our data p ro vide highly suggestive evidence that previous infection - as indicated by IF antibody titers of 1 : 32 - p revents reinfection and it
Table 1. Antibody titers and additional tick bites in control persons Rec. titer
<32 32 64 >64
Additional exposure
No additional exposure n
%
18 6
72.0 24.0
1 25
4.0
n
%
9 2 1 4 16
56.3 12.5 6.3 25.0
476
H. Paul, H.-J. Gerth, and R. Ackermann
cannot be excluded that our 1FT was too insensitive to detect markers of a remote but unimmunizing Borrelia infection. This suspicion is supported by the observation of one child which though being bitten by four ticks - two of them Borrelia positive and all of them engorged with blood - showed no detectable antibodies by 1FT. Use of an ELISA, however, revealed low titered anti-Borrelia antibodies (not shown). Acknowledgement Part of this work will be submitted by H. Paul in partial fulfillment of the requirements for the degree of Doctor of Medicine at the University of Tiibingen.
References 1. Ackermann, R., G. Kabatzki, H. P. Boisten, A. C. Steere, R. L. Grodzichi, S. Hartung, and U. Runne: Spirochaten-Atiologie der Erythema-chronicum-migrans-Krankheit. Dtsch. med:
Wschr. 109 (1984), 92. 2. Schmidt, R., R. Ackermann, ]. Kabatzki, H. Hartung: Epidemiologic aspects of erythema chronicum migrans disease in the Federal Republic of Germany. Second International Symposium on Lyme disease and related disorders. Vienna, Austria, September 17-19, 1985 3. Wilske, B., P. Miinchhoff, G. Schietz, V. Preac-Mursic, M. Roggendorf, and G. Zoulek: Zur Epidemiologie der Borrelia burgdorferi-Infektion. Munch. med. Wschr. 127/8 (1985), 171. H. Paul, Dept. of Medical Virology and Epidemiology of Viral Diseases, Institute of Hygiene, Silcherstr. 7, D-7400 Tubingen, FRG