Pyemotes herfsi

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Pyemotes herfsi

Scientific classification

Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Arachnida
Order:	Acari
Family:	Pyemotidae
Genus:	Pyemotes
Species:	P. herfsi

Binomial name

Pyemotes herfsi
(Oudemans, 1936)

Pyemotes herfsi, also known as the oak leaf gall mite or itch mite, is an ectoparasitic mite, identified in central Europe in 1936, whose presence in the United States was confirmed during the 1990s. Their bites often cause red, itchy, and painful wheals (welts). The mites are barely visible, measuring about 0.2 millimeters; their great reproductive potential, small size, and high capacity for dispersal by wind make them difficult to control or avoid.^[1] The United States Centers for Disease Control estimated that during an outbreak in August 2004, 54% of the population of Crawford County, Kansas, or about 19,000 people, suffered from its bites.^[2] Other states in the US where humans have been affected during the 2000s are Nebraska, Oklahoma, Missouri, Texas,^[3] and Illinois.^[4]

1 Life cycle
2 Distribution
3 Impact on humans
4 Footnotes
5 External links

[edit] Life cycle

The mites' reported hosts have included Anobium punctatum, the pink bollworm, Grapholita molesta, Tineola bisselliella and various pests of stored grain, as well as humans and their pets.^[5] Their usual hosts in the United States are oak midge larvae.^[6] Newly emerged and mated females inject a neurotoxin-containing saliva into their hosts, which paralyzes the host and enables the pregnant female mites to feed on the host's hemolymph. A single mite can paralyze and kill an insect larva 166,000 times its own weight; within a few days, up to 250 adult mites emerge from the female. A life cycle can be completed within seven days.^[7] Conditions that are cooler and moister than average favor its population growth. Outbreaks of attacks on humans in the United States have been attributed to fluctuations in the supply of oak midge larvae.

[edit] Distribution

P. herfsi has been recorded in Czechoslovakia,^[8] Egypt, ^[9] Australia,^[10] northern India,^[11] and the United States. It is a regulated pest in Germany.^[12]

[edit] Impact on humans

Itch mite bites

Rashes resulting from the bite of P. herfsi were first documented in Europe in 1936. The first documented outbreak in the US is thought to have occurred in 1994 in Kansas City, Kansas. The closely related straw itch mite (Pyemotes tritici), was initially suspected, but no specimens of this species were found. The reports indicated that the bites occurred on people after being outdoors in or near wooded areas. Based on this information, a search was initiated and resulted in the discovery of Pyemotes herfsi preying on midge larvae in leaf galls on pin oak trees.

Humans typically report itching from mite bites within 10 to 16 hours after contact. The victims often do not recall being bitten. The rash that results from the bites is usually described as a red patch with a small blister in the center, most often found on the neck, face, arms, or upper torso. A secondary bacterial infection sometimes arises when the bite is scratched. The suggested treatments include the application of calamine lotion, an antihistamine cream such as Benadryl, or a corticosteroid cream; a suggested preventive measure is the application of DEET before outdoor activity.^[13] Anecdotal reports from the Kansas outbreak, however, suggest that DEET might not provide complete protection against P. herfsi.^[14]

The bites are not life-threatening, but a few individuals suffering 100 or more bites have undergone brief hospitalizations.^[15]