Identification of Ixodes ricinus blood meals using an automated protocol with high resolution melting analysis (HRMA) reveals the importance of domestic dogs as larval tick hosts in Italian alpine forests

Abstract

BackgroundIn Europe, Ixodes ricinus L. is the main vector of a variety of zoonotic pathogens, acquired through blood meals taken once per stage from a vertebrate host. Defining the main tick hosts in a given area is important for planning public health interventions; however, until recently, no robust molecular methods existed for blood meal identification from questing ticks. Here we improved the time- and cost-effectiveness of an HRMA protocol for blood meal analysis and used it to identify blood meal sources of sheep tick larvae from Italian alpine forests.MethodsNine hundred questing nymphs were collected using blanket-dragging in 18 extensive forests and 12 forest patches close to rural villages in the Province of Trento. Total DNA was either extracted manually, with the QIAamp DNA Investigator kit, or automatically using the KingFisher™ Flex Magnetic Particle Processors (KingFisher Cell and Tissue DNA Kit). Host DNA was amplified with six independent host group real-time PCR reactions and identified by means of HRMA. Statistical analyses were performed in R to assess the variables important for achieving successful identification and to compare host use in the two types of forest.ResultsAutomating DNA extraction improved time- and cost-effectiveness of the HRMA protocol, but identification success fell to 22.4% (KingFisher™) from 55.1% (QIAamp), with larval hosts identified in 215 of 848 questing nymphs; 23 mixed blood meals were noted. However, the list of hosts targeted by our primer sets was extended, improving the potential of the method. Host identification to species or genus level was possible for 137 and 102 blood meals, respectively. The most common hosts were Rodentia (28.9%) and, unexpectedly, Carnivora (28.4%), with domestic dogs accounting for 21.3% of all larval blood meals. Overall, Cetartiodactyla species fed 17.2% of larvae. Passeriformes (14.6%) fed a significantly higher proportion of larvae in forest patches (22.3%) than in extensive forest (9.6%), while Soricomorpha (10.9%) were more important hosts in extensive forest (15.2%) than in forest patches (4.3%).ConclusionsThe HRMA protocol for blood meal analysis is a valuable tool in the study of feeding ecology of sheep ticks, especially with the cost- and time- reductions introduced here. To our knowledge, we show for the first time that domestic dogs are important larval hosts in the Alps, which may have possible implications for tick-borne disease cycles in urbanized areas.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1901-y) contains supplementary material, which is available to authorized users.

Broad-range survey of vector-borne pathogens and tick host identification of Ixodes ricinus from Southern Czech Republic

“…Similar results were reported for questing nymphal I. ricinus (Moran Cadenas et al. 2007 ; Collini et al 2015 , 2016 ) and questing nymphal Amblyomma americanum (Allan et al. 2010 ).…”

“… 2006 ; Wodecka, Rymaszewska and Skotarczak 2013 ; Collini et al. 2016 ) but higher than in studies using the same method of analysis (49%, 43% and 39% as reported in Humair et al. 2007 ; Moran Cadenas et al.…”

“…Although we have used a relatively old method (Humair et al. 2007 ) of host identification, a recently presented PCR—high-resolution melting analysis brings very similar results concerning identification success (65% and 55% using Qiagen silica-based extraction kit) and portion of samples with multiple host species detected (24% and 11%) (Collini et al 2015 , 2016 ).…”

“… 2010 ; Collini et al. 2016 ) with differences due to final concentration of the target DNA in the homogenate or eluate, extent of contamination with PCR inhibitors, or extent of damage to the integrity of the DNA during extraction.…”

Reviewing the Ecological Evidence-Base for Management of Emerging Tropical Zoonoses: Kyasanur Forest Disease in India as A Case Study

“…Although it seems very unlikely that only the immediate area around a dead or dying infected monkeys supports high density of KFDV-infected partially fed ticks or fully-fed larvae (which would then feed again as nymphs after moulting) that may pass infection to humans, this should be con rmed empirically. Priority should be given to quantifying the tick burden on dead and dying monkeys, assessing the number, species, stage and KFDV infection rate of these attached ticks, as well as determining the number, KFDV infection rate and blood meal identity [73] of ticks sampled from the habitat or off people near the monkey death site. (Priority 10, Table 2).…”