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Acaricidal bacteria infecting laboratory colonies of the tick Boophilus decoloratus (Acarina: Ixodidae)
JOURNAL
OF INVERTEBRATE
PATHOLOGY
38, 149-
151
(1981)
NOTE Acaricidal
Bacteria Boophilus
Infecting Laboratory Colonies of the Tick deco/or&us (Acarina: Ixodidae) produced 100% mortality when injected into a second batch of healthy females. However, the virulence was lost after passage through a Sartorius SM 11306 0.45~pm-poresize filter, suggesting that the pathogen was bacterial and not viral. Extracts from diseased ticks, when streaked onto Oxoid blood agar base, yielded five distinct isolates upon microscopical examination (Table l), whereas extracts from healthy ticks produced no colonies. Each isolate in pure culture caused 100% mortality when reinjected into healthy ticks, from which the same organism could be reisolated, thereby satisfying Koch’s postulates for each being a pathogen. Using Analytical Profile Index 20E identification strips (API System SA, La Balme les Grottes, 38390 MontalieuVercieu, France), the four Gram-negative isolates were identified as a Proteus sp., Klebsiella pneumoniae, a Pseudomonas sp., and P. mirabilis. The Gram-positive isolate was identified as a Staphylococcus sp. Common laboratory strains of S. nzarcescens, K. pneumoniae, a Proteus sp.. Staphylococcus aureus, and Pseudomonas aeruginosa were able to produce the symptoms when injected into healthy females, whereas strains of Shigella, Escherichia coli, Sarcina lutea, and Bacillus cereus had no effect. Although ticks can acquire bacteria from the skin of the host (E. A. Steinhaus, J. Bacterial. 44, 397-404, 1942), in this study infection probably occurred after the engorged females had dropped to the floor, as diseased ticks were never seen on the host, and ticks prevented from falling to the floor after feeding did not develop the disease.
A number of bacterial species have been reported to be pathogenic for ticks, usually causing blackening, swelling, and weakening of the cuticle. These include Bacillus fhuringiensis (0. G. H. Fiedler, “Proceedings, Symposium on Biology and Control of Ticks in Southern Africa,” pp. 170- 174, 1969), Salmonella enteridis (E. A. Steinhaus, “Principles of Insect Pathology,” McGraw-Hill, New York, 19491, Proteus mirabilis and Serratia marcescens (H. Hoogstraal, Bull. WHO 55 (Suppl. l), 337-342, 1977). We report a blackening disease affecting about 5- 10% of ticks in laboratory colonies of Boophilus decoloratus reared on tethered calves and then maintained in an environment room at 26” ? 1°C and 80 + 5% RH. Smears of the body contents of diseased females which had been surface sterilized with ethanol showed the presence of both cocci and bacilli upon microscopical examination (Figs. la-g). No bacteria could be detected in smears from healthy ticks (Fig. lh). The symptoms could be reproduced by injecting healthy engorged females with 5~1 aliquots of a suspension of diseased body contents in 0.05 M phosphate buffer, pH 7.2, containing 0.9% NaCl. Per batch of 40 ticks injected, at least 90% reproducibly developed the symptoms, whereas injecting phosphate-buffered saline or body contents from healthy ticks had no effect. This effect was not restricted to B. decolorutus, but could be obtained by injecting engorged females of Amblyomma hebraeum, Hyalomma marginatum ru$pes, and Rhipicephalus evertsi evertsi with extracts from diseased B. decoloratus. The virulence was not lost upon passage, as extracts from injected ticks 149
0022-2011181/040149-03$01.00/O Copyright All rights
@ 1981 by Academic Press, Inc. of reproduction in any form reserved
150
NOTE
PIG. 1. Light micrographs of Gram-stamed smears of body contents of engorged Boophrlus decoforatus females. The smears from naturally occurring diseased ticks (a-g) showed numerous cocci and bacilli (arrows), large aggregates of bacteria (c), and also Yersinia-like organisms (d, e). Smears from healthy ticks (h) showed numerous dense circular bodies (hematin? erythrocyte “ghosts”?), but no bacteria could be detected. The bar = 5 @m.
ISI
NOTE TABLE CELL
Bacterial sp. Proteus sp. K. pneumoniue Pseudomonus P. mirubili.s Stuphylococcus
sp. sp.
MORPHOLOGY OFTHE
1 FIVE BACTERIAL
ISOLATES
Cell morphology
Motility
Gram stain
Endospores
Small coccobacilli Bacilli Slender bacilli Bacilli Cocci
++ + + -
Negative Negative Negative Negative Positive
Absent Absent Absent Absent Absent
Our results suggest that the gut of B. decolovatus is devoid of bacteria, the blood on which they feed being essentially sterile, and that the syndrome observed is a nonspecific reaction of the ticks to bacterial infection. Although very effective acaricida1 agents, the probability of bacteria being used in biological control is low, as an effective method of infecting ticks in the field is not yet available. KEY WORDS: Boophilus decoloratus; Proteus mirabilis; Klebsiella pneumoniae;
sp.; Staphylococcus sp.; laboratory tick colonies; bacterial infection; blackening disease.
Pseudomonas
DONALD Department
A. HENDRY
of Microbiology
YIGAL Tick Reseurch Unit Department oj‘Zoology Rhodes University Grahamstown 6140 South Africu Received
March
und Entomolog?
26, 1979
RECHAV
OF INVERTEBRATE
PATHOLOGY
38, 149-
151
(1981)
NOTE Acaricidal
Bacteria Boophilus
Infecting Laboratory Colonies of the Tick deco/or&us (Acarina: Ixodidae) produced 100% mortality when injected into a second batch of healthy females. However, the virulence was lost after passage through a Sartorius SM 11306 0.45~pm-poresize filter, suggesting that the pathogen was bacterial and not viral. Extracts from diseased ticks, when streaked onto Oxoid blood agar base, yielded five distinct isolates upon microscopical examination (Table l), whereas extracts from healthy ticks produced no colonies. Each isolate in pure culture caused 100% mortality when reinjected into healthy ticks, from which the same organism could be reisolated, thereby satisfying Koch’s postulates for each being a pathogen. Using Analytical Profile Index 20E identification strips (API System SA, La Balme les Grottes, 38390 MontalieuVercieu, France), the four Gram-negative isolates were identified as a Proteus sp., Klebsiella pneumoniae, a Pseudomonas sp., and P. mirabilis. The Gram-positive isolate was identified as a Staphylococcus sp. Common laboratory strains of S. nzarcescens, K. pneumoniae, a Proteus sp.. Staphylococcus aureus, and Pseudomonas aeruginosa were able to produce the symptoms when injected into healthy females, whereas strains of Shigella, Escherichia coli, Sarcina lutea, and Bacillus cereus had no effect. Although ticks can acquire bacteria from the skin of the host (E. A. Steinhaus, J. Bacterial. 44, 397-404, 1942), in this study infection probably occurred after the engorged females had dropped to the floor, as diseased ticks were never seen on the host, and ticks prevented from falling to the floor after feeding did not develop the disease.
A number of bacterial species have been reported to be pathogenic for ticks, usually causing blackening, swelling, and weakening of the cuticle. These include Bacillus fhuringiensis (0. G. H. Fiedler, “Proceedings, Symposium on Biology and Control of Ticks in Southern Africa,” pp. 170- 174, 1969), Salmonella enteridis (E. A. Steinhaus, “Principles of Insect Pathology,” McGraw-Hill, New York, 19491, Proteus mirabilis and Serratia marcescens (H. Hoogstraal, Bull. WHO 55 (Suppl. l), 337-342, 1977). We report a blackening disease affecting about 5- 10% of ticks in laboratory colonies of Boophilus decoloratus reared on tethered calves and then maintained in an environment room at 26” ? 1°C and 80 + 5% RH. Smears of the body contents of diseased females which had been surface sterilized with ethanol showed the presence of both cocci and bacilli upon microscopical examination (Figs. la-g). No bacteria could be detected in smears from healthy ticks (Fig. lh). The symptoms could be reproduced by injecting healthy engorged females with 5~1 aliquots of a suspension of diseased body contents in 0.05 M phosphate buffer, pH 7.2, containing 0.9% NaCl. Per batch of 40 ticks injected, at least 90% reproducibly developed the symptoms, whereas injecting phosphate-buffered saline or body contents from healthy ticks had no effect. This effect was not restricted to B. decolorutus, but could be obtained by injecting engorged females of Amblyomma hebraeum, Hyalomma marginatum ru$pes, and Rhipicephalus evertsi evertsi with extracts from diseased B. decoloratus. The virulence was not lost upon passage, as extracts from injected ticks 149
0022-2011181/040149-03$01.00/O Copyright All rights
@ 1981 by Academic Press, Inc. of reproduction in any form reserved
150
NOTE
PIG. 1. Light micrographs of Gram-stamed smears of body contents of engorged Boophrlus decoforatus females. The smears from naturally occurring diseased ticks (a-g) showed numerous cocci and bacilli (arrows), large aggregates of bacteria (c), and also Yersinia-like organisms (d, e). Smears from healthy ticks (h) showed numerous dense circular bodies (hematin? erythrocyte “ghosts”?), but no bacteria could be detected. The bar = 5 @m.
ISI
NOTE TABLE CELL
Bacterial sp. Proteus sp. K. pneumoniue Pseudomonus P. mirubili.s Stuphylococcus
sp. sp.
MORPHOLOGY OFTHE
1 FIVE BACTERIAL
ISOLATES
Cell morphology
Motility
Gram stain
Endospores
Small coccobacilli Bacilli Slender bacilli Bacilli Cocci
++ + + -
Negative Negative Negative Negative Positive
Absent Absent Absent Absent Absent
Our results suggest that the gut of B. decolovatus is devoid of bacteria, the blood on which they feed being essentially sterile, and that the syndrome observed is a nonspecific reaction of the ticks to bacterial infection. Although very effective acaricida1 agents, the probability of bacteria being used in biological control is low, as an effective method of infecting ticks in the field is not yet available. KEY WORDS: Boophilus decoloratus; Proteus mirabilis; Klebsiella pneumoniae;
sp.; Staphylococcus sp.; laboratory tick colonies; bacterial infection; blackening disease.
Pseudomonas
DONALD Department
A. HENDRY
of Microbiology
YIGAL Tick Reseurch Unit Department oj‘Zoology Rhodes University Grahamstown 6140 South Africu Received
March
und Entomolog?
26, 1979
RECHAV