Pyemotes herfsi
Encyclopedia
Pyemotes herfsi, also known as the oak leaf gall mite or itch mite, is an ectoparasitic
mite
identified in central Europe
in 1936 and subsequently found in India, Australia, and the United States. The mite parasitizes a variety of insect hosts and bites humans, causing red, itchy, and painful wheal
s (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.
-containing saliva into their hosts, which paralyzes the host and enables the gravid female mites to feed on the host's hemolymph
. The posterior portion (opisthosoma) of the female enlarges as its progeny develops inside, and, within a few days, up to 250 adult mites emerge from the gravid female. Bruce and Wrensch (1990) found that progeny of the straw itch mite averaged 254 offspring of which 92% were females. Males emerge before the females, position themselves around the mother's genital opening, and mate with emerging females. Then, mated females disperse to find new hosts. These mites often are dispersed by wind, and when they land on vertebrate hosts, they attempt to feed, resulting in the bites. A life cycle can be completed within seven days, and progeny emergence can be extended to 15 days.
The mites' reported hosts have included Anobium punctatum, the pink bollworm
, Grapholita molesta, Tineola bisselliella, Apis cerana
(Asiatic honey bee), periodic cicadas, and various pests of stored grain, as well as humans and their pets. Their usual hosts in the United States are oak
midge larva
e. 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.
, Egypt
, Australia
, northern India
, and the United States. It is a regulated pest in Germany
.
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.
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. Other states in the US where humans have been affected during the 2000s are Nebraska
, Oklahoma
, Missouri
, Tennessee Shelby County, Texas
, and Illinois
. In August 2008 an outbreak was reported in the northern suburbs of Cincinnati, Ohio
by the Hamilton County
Public Health Department.
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. Anecdotal reports from the Kansas outbreak, however, suggest that DEET might not provide complete protection against P. herfsi.
The bites are not life-threatening, but a few individuals suffering 100 or more bites have undergone brief hospitalizations.
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
mite
Mite
Mites, along with ticks, are small arthropods belonging to the subclass Acari and the class Arachnida. The scientific discipline devoted to the study of ticks and mites is called acarology.-Diversity and systematics:...
identified in central Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
in 1936 and subsequently found in India, Australia, and the United States. The mite parasitizes a variety of insect hosts and bites humans, causing red, itchy, and painful wheal
Wheal
Wheal may refer to:*Wheal response, a cutaneous condition left by a blow or as part of an allergic reaction*Wheal, a Cornish mine...
s (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.
Life cycle
Newly emerged and mated females inject a neurotoxinNeurotoxin
A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...
-containing saliva into their hosts, which paralyzes the host and enables the gravid female mites to feed on the host's hemolymph
Hemolymph
Hemolymph, or haemolymph, is a fluid in the circulatory system of some arthropods and is analogous to the fluids and cells making up both blood and interstitial fluid in vertebrates such as birds and mammals...
. The posterior portion (opisthosoma) of the female enlarges as its progeny develops inside, and, within a few days, up to 250 adult mites emerge from the gravid female. Bruce and Wrensch (1990) found that progeny of the straw itch mite averaged 254 offspring of which 92% were females. Males emerge before the females, position themselves around the mother's genital opening, and mate with emerging females. Then, mated females disperse to find new hosts. These mites often are dispersed by wind, and when they land on vertebrate hosts, they attempt to feed, resulting in the bites. A life cycle can be completed within seven days, and progeny emergence can be extended to 15 days.
The mites' reported hosts have included Anobium punctatum, the pink bollworm
Pink bollworm
The pink bollworm , , is an insect known for being a pest in cotton farming. The adult is a small, thin, gray moth with fringed wings. The larva is a dull white, eight-legged caterpillar with conspicuous pink banding along its dorsum...
, Grapholita molesta, Tineola bisselliella, Apis cerana
Apis cerana
Apis cerana, or the Asiatic honey bee , is a species of honey bee found in southern and southeastern Asia, such as China, India, Japan, Malaysia, Nepal, Bangladesh and Papua New Guinea. This species is the sister species of Apis koschevnikovi, and both are in the same subgenus as the Western honey...
(Asiatic honey bee), periodic cicadas, and various pests of stored grain, as well as humans and their pets. Their usual hosts in the United States are oak
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...
midge larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e. 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.
Distribution
P. herfsi has been recorded in CzechoslovakiaCzechoslovakia
Czechoslovakia or Czecho-Slovakia was a sovereign state in Central Europe which existed from October 1918, when it declared its independence from the Austro-Hungarian Empire, until 1992...
, Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, northern India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, and the United States. It is a regulated pest in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
.
Impact on humans
Kansas City, Kansas
Kansas City is the third-largest city in the state of Kansas and is the county seat of Wyandotte County. It is a suburb of Kansas City, Missouri, and is the third largest city in the Kansas City Metropolitan Area. The city is part of a consolidated city-county government known as the "Unified...
. The closely related straw itch mite (Pyemotes tritici
Pyemotes tritici
Pyemotes tritici is a species of mite known as the grain itch mite or straw itch mite. There is some evidence that it may be associated with dermatitis in humans....
), 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
Pin oak
Quercus palustris, the Pin oak or Swamp Spanish oak, is an oak in the red oak section Quercus sect. Lobatae.-Distribution:...
trees.
The United States Centers for Disease Control estimated that during an outbreak in August 2004, 54% of the population of Crawford County, Kansas
Crawford County, Kansas
Crawford County is a county located in southeastern Kansas in the United States. As of the 2010 census, the county population was 39,134. Its county seat is Girard, and its most populous city is Pittsburg. The county was named in honor of Samuel J. Crawford, Governor of Kansas...
, or about 19,000 people, suffered from its bites. Other states in the US where humans have been affected during the 2000s are Nebraska
Nebraska
Nebraska is a state on the Great Plains of the Midwestern United States. The state's capital is Lincoln and its largest city is Omaha, on the Missouri River....
, Oklahoma
Oklahoma
Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...
, Missouri
Missouri
Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...
, Tennessee Shelby County, Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
, and Illinois
Illinois
Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...
. In August 2008 an outbreak was reported in the northern suburbs of Cincinnati, Ohio
Cincinnati, Ohio
Cincinnati is a city in the U.S. state of Ohio. Cincinnati is the county seat of Hamilton County. Settled in 1788, the city is located to north of the Ohio River at the Ohio-Kentucky border, near Indiana. The population within city limits is 296,943 according to the 2010 census, making it Ohio's...
by the Hamilton County
Hamilton County, Ohio
As of 2000, there were 845,303 people, 346,790 households, and 212,582 families residing in the county. The population density was 2,075 people per square mile . There were 373,393 housing units at an average density of 917 per square mile...
Public Health Department.
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
Calamine
Calamine is a mixture of zinc oxide with about 0.5% ferric oxide . It is the main ingredient in calamine lotion and is used as an antipruritic to treat mild pruritic conditions such as sunburn, eczema, rashes, poison ivy, chickenpox, and insect bites and stings...
lotion, an antihistamine
Antihistamine
An H1 antagonist is a histamine antagonist of the H1 receptor that serves to reduce or eliminate effects mediated by histamine, an endogenous chemical mediator released during allergic reactions...
cream such as Benadryl
Benadryl
Benadryl is a brand name allergy medicine marketed over-the-counter by Johnson & Johnson subsidiary McNeil Consumer Healthcare. Prior to 2007, Benadryl was marketed by Pfizer Consumer Healthcare...
, or a corticosteroid
Corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
cream; a suggested preventive measure is the application of DEET
DEET
N,N-Diethyl-meta-toluamide, abbreviated DEET, is a slightly yellow oil. It is the most common active ingredient in insect repellents...
before outdoor activity. Anecdotal reports from the Kansas outbreak, however, suggest that DEET might not provide complete protection against P. herfsi.
The bites are not life-threatening, but a few individuals suffering 100 or more bites have undergone brief hospitalizations.