Comparison of DNA and Carbon and Nitrogen Stable Isotope-based Techniques for Identification of Prior Vertebrate Hosts of Ticks

Abstract

Identification of the vertebrate hosts upon which hematophagous arthropods feed provides key information for understanding the ecology and transmission of vector-borne diseases. Bloodmeal analysis of ticks presents unique challenges relative to other vectors, given the long interval between bloodmeal acquisition and host-seeking, during which DNA degradation occurs. This study evaluates DNA-based and stable isotope-based bloodmeal analysis methodologies for the lone star tick, Amblyomma americanum (Linneaus, 1758), in an experimental study with chicken as the known host. We subjected ticks of different ages and environmental rearing conditions to three DNA-based approaches and a stable isotopic analysis, which relies on the natural variation of nitrogen ((15)N/(14)N) and carbon ((13)C/(12)C) isotopes. While all three DNA-based approaches were successful in identifying the bloodmeal host of the engorged nymphs, only the probe-based RT-PCR was able to detect host DNA in aged ticks, the success of which was low and inconsistent across age and rearing treatments. In contrast, the stable isotope analysis showed utility in determining the host across all ages of ticks when isotopic values of ticks were compared with a panel of candidate vertebrate species. There was a positive shift in both δ(13)C and δ(15)N in adult A. americanum until 34 wk postnymphal bloodmeal. Through analyzing the isotopic signatures of eight potential vertebrate host species, we determined that the magnitude of this isotopic shift that occurred with tick age was minor compared with the heterogeneity in the δ(15)N and δ(13)C signatures among species. These results suggest that stable isotopes are a useful tool for understanding tick-host interactions.

High Rate of Non-Human Feeding by Aedes aegypti Reduces Zika Virus Transmission in South Texas

“…The Sella score was used to identify the engorged mosquitoes that had the highest likelihood of yielding a DNA sequence. To minimize exogenous DNA on the mosquito exoskeleton, each whole mosquito was washed in 10% bleach followed by two rinses with nuclease-free water [21][22][23][24]. On a clean, chilled microscope slide, the abdomen was carefully separated from the rest of the mosquito body, and the abdominal contents were expressed into a new, labeled, DNA-free 1.5 mL microcentrifuge tube.…”

Host identification in unfed ticks from stable isotope compositions (δ13C and δ15N)

“…This takes advantage of the fact that the isotopic composition of a host is transferred to a blood‐feeding arthropod via the host's blood. In three proof‐of‐concept studies using small sets of laboratory animal species, the host isotopic signature of the blood was shown to be replicated in unfed stages of the ticks, Ixodes ricinus (Schmidt et al , ), Ixodes scapularis (LoGiudicea et al , ) and Amblyomma americanum (Hamer et al , ).…”

Characterization of triatomine bloodmeal sources using direct Sanger sequencing and amplicon deep sequencing methods

“…While this approach allows for species-specific host identification to the level of resolution afforded by the GenBank sequence database 10 , it has posed particular challenges in bloodmeal analysis of vectors with multiple bloodmeals and those that molt through several stages. For example, determination of bloodmeal sources of hard ticks is difficult due to degradation of vertebrate DNA while molting from one life stage to the next 11 , 12 . Bloodmeal analysis methods which detect only a single host may lead to a biased characterization of the host community.…”