Determination of the detection time limit of blood meal host DNA in a tick, Rhipicephalus
(Boophilus), post feeding

Tanatswa X N Gara

Abstract

Determination of the detection time limit of blood meal host DNA in a tick, Rhipicephalus (Boophilus), post feeding

The tick genus, Rhipicephalus (Boophilus), is a common
hematophagous parasite found feeding on animals. This
study examined the extent to which host DNA in a blood
meal in Rhipicephalus, can be identified post feeding using
a cytochrome b polymerase chain reaction (PCR) assay.
Female adult ticks (0.2 and 0.25 grams) were collected
from cows and divided into 2 groups, one group was
kept alive so as to analyse DNA degradation due to digestion
and the other group was euthanized to analyse degradation
due to decomposition. Morphological changes of
the ticks were tracked and the presence/absence of cow
DNA was analysed over time. Live ticks were analysed daily
until they died and the dead ticks were analysed up to
290 days post feeding (PF). The ticks’ gut contents were
placed on Whatman® filter paper and dried before Chelex
® DNA extraction. A 561 base pair region on the cytochrome
b gene of the cow mitochondrial DNA was amplified
and PCR products were visualized using agarose gel
electrophoresis. Cow DNA was detected in the live ticks
up to day 23 PF, however, probability of successful detection
went down to at least 33% after day 15 PF. The live
ticks started dying from day 40 PF and the last one died
52 days PF. Cow DNA was detected with bright bands in
the dead ticks from day 1 PF to day 290 PF which is when
the last sample was run, so the detection limit of DNA
in dead ticks could not be determined. The persistence
of host DNA in ticks showed the utility of ticks in forensic
investigations. The methods used in this study can be
used in forensic acarology to identify the host species of
an arthropod when it is found at a crime scene.