Source: KANSAS STATE UNIV submitted to
POPULATION OUTBREAKS OF AN INTRODUCED SPECIES OF ITCH MITES
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
0203473
Grant No.
2005-37610-15641
Project No.
KS9541
Proposal No.
2005-04072
Multistate No.
(N/A)
Program Code
NI
Project Start Date
May 15, 2005
Project End Date
May 14, 2007
Grant Year
2005
Project Director
Broce, A.
Recipient Organization
KANSAS STATE UNIV
(N/A)
MANHATTAN,KS 66506
Performing Department
ENTOMOLOGY
Non Technical Summary
The first reports in the summer of 2004 about outbreaks of unusual itchy and painful insect bites on humans were from Pittsburg, KS; these were soon followed by reports from other communities in KS, NE, MO, OK, and most recently, TX (Dallas and Houston). Typical bites are raised, reddened 1 inch diam welts, with a pimple in their center; itchy but painful if scratched, which often results in secondary infections. The cause of these bites was found to be an introduced European species of itch mites, Pyemotes herfsi, in oak leaf galls, preying upon the larvae of two Cecidomyiid midges, that make the leaf marginal roll galls and smooth vein pocket galls on, mainly, pin oak, but also on red and black oaks. There were cases of affected people with severe reactions to the bites; some had to visit with their physicians; however, little or no information is available on how to prevent the bites of these mites. We propose to conduct studies on the bionomics of these mites; and obtain information that will be immediately useful to people in reducing the risk of bites from these mites. Studies will be aimed at determining if the manifestation of bites is a function of the time P. herfsi is exposed to the vertebrate host and the value of DEET-based repellents in protecting against this mite; determining P. herfsi's geographical distribution in the USA; determining important life cycle parameters of P. herfsi; and developing Extension publications on how best to deal with this mite's health threat.
Animal Health Component
60%
Research Effort Categories
Basic
40%
Applied
60%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
21131201130100%
Goals / Objectives
A. To investigate bionomical parameters of Pyemotes herfsi important for dealing with this introduced itch mite 1)Determine if the manifestation of bites is a function of the time P. herfsi is exposed to the vertebrate host and the value of DEET-based repellents in protecting against this mite 2)Determine P. herfsis geographical distribution in the USA 3)Determine important biological parameters of P. herfsi 4)Develop Extension publications on how best to deal with this mites health threat.
Project Methods
The relationship between time of mite exposure and manifestation of bites will be studied using cats as hosts (after the proper permits are obtained from the universitys animal use and compliance offices), on the assumption that cats and dogs respond to bites of itch mites similarly as humans do. Mated female mites will be confined in plastic cells against the cats shaved skin for varying periods of time and the appearance of bites will be correlated to the length of time of mite exposure; each cat receiving a treatment of mites (in cell) and a control (empty cell). Evaluation of bite development will be by the number of bite pimples, as the welts will most likely coalesce into a single one. The efficacy of DEET in repelling itch mites will be evaluated also using cats and exposing mites to patches of shaved skin treated with high (>50%) and low (<40%) commercial formulations of DEET. Description of the geographical distribution of this mite in the USA will be initiated by obtaining from Extension personnel samples of oak leaves with marginal leaf roll galls. Self addressed/stamped envelopes with Ziplock bags for enclosing leaves will be sent to county Extension personnel in Midwestern states and in adjacent ones. This information should provide a baseline for future efforts applying Geographical Information System to explain the mites current distribution and to predict its potential future expansion. There is little published information on the life histories of P. herfsi, so efforts will be devoted to describing some of the most basic bionomical parameters of this mite and its midge host. Experiments will be conducted to estimate the relationship between wind speed and direction and downwind dispersal of mites using adhesive-coated panels positioned at various distances downwind from documented mite-infested trees; and exposed for a given period of time. The methods mites use to survive the winter and to reinfest leaf galls will be investigated by inspecting galls on trees and on the ground throughout the winter months. Pyramidal emergence traps positioned over leaf litter under oaks determined to be mite-infested the previous fall should yield adult midges which will be inspected for phoretic mites and will be submitted to the proper systematic experts for classification. Survey of galls on leaves as a function of height should indicate if the incidence (frequency) of mite-infested galls varies with their height on the trees. Results of these studies will be used to develop recommendations on how to deal with this mite to reduce or avoid their troublesome bites; and will be disseminated through existing Extension programs and networks, as well as in peer-reviewed journals.

Progress 05/15/06 to 05/15/07

Outputs
Populations of Pyemotes herfsi in the Midwestern U.S.A. were significantly lower than those in 2004 and 2005. Whereas in the two previous years high populations of midges and high incidence of bite outbreaks over large areas characterized this problem, the mite situation in 2006 was characterized by high mite incidence over small areas. In addition, a high incidence of at least two species of parasitic wasps (yet to be identified) were recorded parasitizing midge larvae in Nebraska and Kansas with up to 46.7% of the leaf marginal roll galls in Manhattan, KS having at least one wasp larva/gall. Weather might have also affected the mites and/or their midge hosts given that temperatures of the early summers of 2004 and 2005 were considerably lower than those of 2006. Likewise, unconfirmed records of the mite presence in Kansas in 1994-96 show a similar population decline in 1996 after high bite outbreaks in the two previous years; temperature patterns in those three years mirrored those in 2004-06. A life cycle covering midges' and mites' biology has been constructed, with a significant gap on the mites' whereabouts from November to late July when their presence is felt by their bites inflicted on humans. The hypothesis that the mites do not appear until late July is due to the size of their host midges was reinforced with additional data. Several formulations of various insecticides were field-evaluated as treatments applied to lawns to prevent the emerging midges from reaching the tree foliage. Several of the treatments gave 94-96% control. However, although these chemical treatments would give high percentage control of emerging midges, they would not protect the trees from the attack (gall forming) by midges from neighboring untreated lawns. Thus, a systemic insecticide was also evaluated to protect trees from midge attack. However, this treatment did not give any significant midge control. Plans are for testing additional insecticide formulations during the spring of 2007.

Impacts
Drastic decline in the populations of the mite Pyemotes herfsi supports the idea that this mite has been in the Midwestern U.S.A, for several years. Information obtained on the biology of this mite and its main host, a Cecydomiid midge larva, will be useful in designing recommendations on how to avoid these mites and managing practices for this itch mite by controlling the populations of its host.

Publications

  • No publications reported this period


Progress 05/15/05 to 05/14/07

Outputs
Populations of Pyemotes herfsi in the Midwestern U.S.A. were significantly lower than those in 2004 and 2005. Whereas in the two previous years high populations of midges and high incidence of bite outbreaks over large areas characterized this problem, the mite situation in 2006 was characterized by high mite incidence over small areas. In addition, a high incidence of at least two species of parasitic wasps (yet to be identified) were recorded parasitizing midge larvae in Nebraska and Kansas with up to 46.7% of the leaf marginal roll galls in Manhattan, KS having at least one wasp larva/gall. Weather might have also affected the mites and/or their midge hosts given that temperatures of the early summers of 2004 and 2005 were considerably lower than those of 2006. Likewise, unconfirmed records of the mite presence in Kansas in 1994-96 show a similar population decline in 1996 after high bite outbreaks in the two previous years; temperature patterns in those three years mirrored those in 2004-06. A life cycle covering midges' and mites' biology has been constructed, with a significant gap on the mites' whereabouts from November to late July when their presence is felt by their bites inflicted on humans. The hypothesis that the mites do not appear until late July is due to the size of their host midges was reinforced with additional data. Several formulations of various insecticides were field-evaluated as treatments applied to lawns to prevent the emerging midges from reaching the tree foliage. Several of the treatments gave 94-96% control. However, although these chemical treatments would give high percentage control of emerging midges, they would not protect the trees from the attack (gall forming) by midges from neighboring untreated lawns. Thus, a systemic insecticide was also evaluated to protect trees from midge attack. However, this treatment did not give any significant midge control. Plans are for testing additional insecticide formulations during the spring of 2007.

Impacts
Drastic decline in the populations of the mite Pyemotes herfsi supports the idea that this mite has been in the Midwestern U.S.A. for several years. Information obtained on the biology of this mite and its main host, a Cecydomiid midge larva, will be useful in designing recommendations on how to avoid these mites and managing practices for this itch mite by controlling the populations of it host.

Publications

  • No publications reported this period


Progress 05/15/05 to 05/14/06

Outputs
Outbreaks of red, itching and painful welts on people in the Midwestern US in the summer of 2004 led to the discovery of an European species of mite, Pyemotes herfsi. Typical bites were red welts about 2 cm diameter with a central vesicle and were itchy and painful when scratched, often resulting in secondary bacterial infection. The frequency of bite reports shifted from persons engaged in summer activities to homeowners involved in fall gardening activities, especially leaf raking; this pattern of bite outbreaks was repeated in 2005. These mites prey on Cecydomiid midge larvae responsible for the marginal leaf roll and smooth vein pocket galls on, preferentially, pin oaks, but also on red and black oaks. Pyemotes herfsi are 0.2 mm long; barely visible to the naked eye. Newly-emerged and mated females inject a neurotoxin-containing saliva into their hosts, which paralyzes the host and enables the gravid female mites to feed on the host haemolymph. The posterior portion (opisthosoma) of the female enlarges (physogastry) as its progeny develops inside and, within 7-14 days, up to 250 adult mites emerge from the gravid female, of which ca. 90% are females. Wind dispersal of female mites was demonstrated by trapping on vertical adhesive-coated cards. Oak trees were sampled in 30 different areas in Pittsburg, KS, and on 17 of these areas, the oaks had 48% of their leaves infested with these mites at the rate of 4.5 gravid females/leaf. Of 229 fallen oak leaves collected in February 2005 in Lincoln, NE, 193 (84%) were infested with these mites. Massive emergence of overwintering midges was recorded in mid-April 2005 in Lincoln, NE which resulted in 100% of the oak leaves in some of the trees to be infested with galls. However, mites were not found in leaf galls until August; apparently due to midge larvae not being large enough to provide nourishment to gravid female mites until such a date. Mites presence has been documented in KS, NE, IL, OK, IN; and suspected to also occur in TX and KY. Insect repellents, according to numerous reports from patients, failed to provide protection from the mites bites. Plans are to evaluate the efficacy of systemic pesticides against midge larvae as a strategy for controlling these Pyemotes mites.

Impacts
It appears that this Pyemotes itch mite had been the cause of other previous, but restricted outbreaks of bites. Information on how to manage this pest is important and urgently needed as homeowners with mite-infested pin oaks are indicating interest in cutting down the oaks on their property to avoid the painful bites. Thus, the identification of the bites causative agent and information on its biology will allow research on how to manage this pest.

Publications

  • No publications reported this period