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Detection of Human Blood in the Bat Tick Carios (Ornithodoros) kelleyi (Acari: Argasidae) in Iowa

J. S. Gill, W. A. Rowley, P. J. Bush, J. P. Viner, M. J. R. Gilchrist
DOI: http://dx.doi.org/10.1603/0022-2585-41.6.1179 1179-1181 First published online: 1 November 2004


The argasid tick Carios (Ornithodoros) kelleyi Cooley & Kohls is a common ectoparasite of bats and has been found in massive numbers in homes with associated bat colonies in eastern Iowa. This tick feeds nearly exclusively on bats in nature. Several inhabitants of infested homes complained of “bug bites" at night while asleep that may have resulted in erythematous, edematous, urticaric skin lesions and constitutional signs and symptoms. We provide laboratory evidence that a single, engorged C. kelleyi nymph contained host blood from a human female. The clinical implications of our findings are intriguing but unclear.

  • human blood
  • Carios kelleyi
  • home infestation
  • skin lesions
  • bats

We recently investigated several, massive infestations of the common bat tick Carios (Ornithodoros) kelleyi Cooley & Kohls in homes located along the Mississippi River in eastern Iowa. Occupants of these homes reported seeing as many as several hundred ticks daily throughout their homes, occurring on walls, ceilings, carpeting, and floors, as well as in beds and on furniture. Daily cleaning and vacuuming were ineffective in eliminating the ticks. Residents complained of "bug bites" at night, which apparently resulted in expanding, erythematous, edematous, urticaric skin lesions and constitutional signs and symptoms that included lymphadenopathy, irritability, fever, weight loss, malaise, and fatigue.

The argasid tick C. kelleyi has been identified in several states, as well as Canada, Mexico, Cuba, and Costa Rica (Cooley and Kohls 1944, Wilkinson et al. 1980). Its primary host in nature is bats and under laboratory conditions C. kelleyi will feed on a limited number of animals other than bats (Sonenshine and Anastos 1960). It had not been judged to feed on humans; however, there is a single published article (Vargas 1984) reporting circumstantial evidence that five individuals experienced bites from these ticks (but possibly other arthropods) in Costa Rica.

In this report, we provide evidence that a single, engorged C. kelleyi nymph, collected from a home (occupied by a father, mother, two daughters, and pet cat) in eastern Iowa known to have bats, contained blood from a human female.

Materials and Methods

Identification of primate hemoglobin was performed using the ABAcard HemaTrace system (Abacus Diagnostics, West Hills, CA) according to the manufacturer’s protocol. This assay system is highly specific and sensitive for primate hemoglobin, detecting concentrations as low as 0.05 μg/ml. Approximately 5 μl of blood was removed from a single, live, engorged C. kelleyi nymph by making a small puncture wound on the dorsal surface. The collected blood was diluted in 1 ml of buffer. One hundred and fifty microliters of the suspension was placed in the sample well of the immunochromatographic test kit, and the result was observed after 10 min. Blood from the little brown bat, Myotis lucifugus LeConte, and the big brown bat, Eptesicus fuscus Palisot de Beauvois, also was tested.

Blood from the engorged tick was further analyzed by nucleic acid techniques by using the PowerPlex 16 system (Promega, Madison, WI) according to the manufacturer’s protocol to determine the presence of human DNA. This system is designed to detect up to 15 human short tandem repeat (STR) sequence loci and a human sex locus, Amelogenin. Briefly, DNA was extracted from ≈5 μl of blood removed from the engorged tick by using the Chelex 100 system (Bio-Rad, Hercules, CA) and subjected to proteinase K (Fisher, Fairlawn, NJ) digestion. Polymerase chain reaction (PCR) amplification was performed according to PowerPlex instructions by using the PerkinElmer 9700 Thermal cycler (PerkinElmer Life and Analytical Sciences, Downers Grove, IL). Detection of amplified PCR products was performed on the ABI Prism 310 Genetic Analyzer (Applied Biosystems, Foster City, CA) by capillary electrophoresis and analyzed by ABI Genescan software and Genotyper.


The single, live, engorged C. kelleyi nymphal tick contained human blood. Immunochromatographic tests were positive for primate hemoglobin (Fig. 1A). Blood samples from the little brown bat and the big brown bat were negative when tested in the immunochromatographic assay (Fig. 1B). DNA analysis performed on the blood from the tick was consistent with blood of a human female. A partial profile from the extracted DNA was positive for seven of the 15 STR loci and positive for Amelogenin locus located on the X chromosome. The seven STR loci include D3S1358, D18S51, D5S818, D13S317, D16S539, CSF1PO, and D8S1179. DNA extracted from bat blood (big brown bat) and subjected to STR loci and Amelogenin locus analysis was negative.

Fig. 1

Immunochromatographic analysis of blood. (A) Detection of primate blood obtained from C. kelleyi nymph. Line C, positive internal control; line T, positive sample response. (B) Analysis of blood obtained from E. fuscus showing lack of reactivity. Line C, positive internal control; line T, negative response.


C. kelleyi occurs throughout the United States, Canada, Cuba, Mexico, and Costa Rica (Cooley and Kohls 1944, Wilkinson et al. 1980). It is an ectoparasite of several species of bats (Knight and Marr 1983, Ritzi et al. 2001, Steinlein et al. 2001). Under laboratory conditions, it feeds on relatively few animals other than bats and prefers to feed in subdued light or darkness (Sonenshine and Anastos 1960). Thus, human observation is limited.

Vargas (1984) reported several people in Costa Rica were bitten by C. kelleyi. This report, however, did not provide laboratory evidence that C. kelleyi had fed on humans. Our results by two independent analytical procedures demonstrate human blood for the first time in this species. Four humans were the only primate inhabitants of the house from which this tick was collected, and thus the positive result in the immunochromatographic test is due to human hemoglobin. DNA analysis of the tick blood yielded a positive result in seven of the 15 STR loci and the Amelogenin locus. It is likely that only seven STR loci and not all 15 STR loci reacted positively because of the relatively small amounts of DNA used in the analysis. DNA analysis of blood taken from the hard tick Ixodes ricinus L. has been used to determine the host species upon which ticks have fed (Kirsten and Gray 1996, Pichon et al. 2003).

The health implications of our findings are unclear. Several individuals who may have been bitten by C. kelleyi ticks reported skin lesions and vague constitutional symptoms. Given that C. kelleyi is not a commonly reported tick and that it infrequently bites humans, it has not escaped our attention that the signs and symptoms seemingly associated with C. kelleyi bites may represent a disease(s) not previously described.


We are grateful to Jim Mertins (National Veterinary Services Laboratory, Ames IA) for expert tick identification; Thomas F. Gahan and James P. Nelson (University of Iowa Hygienic Laboratory, Iowa City, IA) for technical assistance and photographic assistance, respectively; Russell W. Currier and M. Patricia Quinlisk (Iowa Department of Public Health, Des Moines, IA) for excellent advice; and Frank Frieburg (Jackson County Board of Health, Maquoketa, IA) for tick collecting assistance. This publication was supported by Cooperative Agreement No. E11/CCE721861 from the Centers for Disease Control and Prevention.


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References Cited

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