Gras-Ernte-Herbst-Südstadt-Milbe by J.-Th. Franz

Diese Milbe gehört zur Familie (;

Arachnida, ; Acariformes (= Actinotrichida); Prostigmata;

Trombidioidea; Trombiculidae).

In unseren Breiten ist die Erntemilbe (Neotrombicula) autumnalis (Erntemilbe,Grasmilbe, Herbstmilbe, Chigger (engl.)) ein zunehmend auftretender Quälgeist insbesondere in den Monaten

Juli bis Oktober.

Trombicula

Trombiculidae sind Bodenbewohner. Die Nymphen und Adulti stellen kleinen Arthropoden nach. Die Larven jedoch sind bis auf wenige Ausnahmen Wirbeltierparasiten (Ecto), die die Haut anbohren und Blut saugen. Einige Arten haben sich auf die äußeren und inneren Luftwege von Kleinsäugern und marinen Reptilien spezialisiert, wo sie ebenso wie bei

Fledermäusen als internasale Parasiten leben (Larven).

Die Larven einiger Arten, die üblicherweise Reptilien,

Kleinsäuger oder Vögel befallen, können auch auf den

Menschen übergehen.

Die Larven injizieren eine die Haut lysierende Speichel- flüssigkeit, so daß ein für die Trombiculidae charakter- istisches sogenanntes Stylostom entsteht. Dadurch können sie die sogenannte Trombidiose (Trombidiosis, Trombiculiasis) erzeugen, die nicht selten von heftigen Reaktionssymptomen begleitetet wird. Erntekrätze, Beiß, Erntebeiß: Stropholus- artige Knötchen, Quaddeln oder Erytheme insbesondere an den

Unterschenkeln.

Saugende Larve.

Cheliceren-Harken

Soweit bekannt, werden von der einheimischen Grasmilbe

(besserer Name, da Grasmilben schon ab dem April auftreten) keine Infektionskrankheiten übertragen. Bei einem extremen

Befall (hundert bis über tausend Bisse) kann es aber zu

(vorübergehenden) Lähmungs- und Ausfallerscheinungen kommen.

In Japan, Sumatra, Malaysia, Indien und Australien hingegen treten andere anthropogen wichtige Vertreter der Trombi- culidae auf. So Trombicula akamushi oder Trombicula delhiensis. Sie sind die Überträger der fieberhaften, lebensgefährlichen Infektionskrankheit Tsutsugamushi-Fieber

(scrub typhus) (Erreger: Rickettsia tsutsugamushi).

Trombicula autumnalis (Grasmilbe, Erntemilbe, Herbstmilbe):

Die Grasmilbe wird bis zu zwei mm lang und ihr Körper ist mit vielen langen (weißen) Haaren bedeckt. Sie lebt im

Boden und kommt bei warmen, feuchten Witterungsverhältnis- sen nahe an die Oberfläche. Bei Dürre, Kälte (Winter) und starken Regenfällen dringt sie bis in Bodentiefen von 60 -

90 cm vor.

Im Hoch- bzw. Spätsommer schlüpfen die ca. 0,25 mm großen

Larven (sechs Beinpaare). Diese reagieren lichtpositiv und aggregieren an mäßig feuchten Wiesenstellen bzw. Gärten auf insbesondere Grashalmen (Massenansammlungen sind möglich).

Bei warmen und sonnigem Wetter sind sie sehr aktiv und be- fallen vorbeikommende Wirbeltiere (Warmblüter, in der Regel

Mäuse, Ratten, Kaninchen und Igel, aber auch Hunde und

Katzen) sofort, um an insbesondere dünnen Hautstellen zu saugen.

Da der Mensch ebenfalls ein Warmblüter ist, befällt die Larve auch den Menschen, wobei sie hauptsächlich an den Knöcheln, den Weichen und und den Achselhöhlen saugen. Dabei stößt die

Larve ihre Cheliceren-Haken durch die Haut bis in die Epidermis- zellen. Anschließend löst der in die Wunde gedrückte Speichel die oberste Zellschicht auf. Die dabei entstehende Flüssigkeit

(+ Plasmastücke) wird aufgesaugt. Durch erneute Speichelabgaben wird die Wunde vertieft. Die Epidermiszellen bilden eine dünne

Hornschicht, die bei jeder erneuten Speicheleinpressung durch- stoßen wird. Hierdurch kommt es zu einer jeweils vertieften

Hornschicht, die sich letztendlich zu einem bis ca. 0,2 mm langen Rohr ausprägen (Stylostom), wobei die Cheliceren-Haken der Larve eigentlich nur 0,03 mm lang sind.

Der abgegebene Speichel enthält Stoffe, die fürchterlich jucken.

Es gibt nur wenige Stiche oder Bisse anderer Quälgeister, die dermaßen jucken und der Juckreiz kann mehr als eine Woche an- halten, so daß es aufgrund des unwillkürlichen Kratzens fast immer zu Entzündungen kommt.

Insgesamt saugt die Larve 2 - 3 Tage, wobei sie bis auf 0,75 mm anschwillt. Anschließend läßt sich die Larve vom Wirt abfallen und dringt in den Boden ein. Hier entwickelt sich die Larve innerhalb von fünf bis sechs Wochen zur achtbeinigen Nymphe.

Diese unterscheidet sich nur die geringere Größe (1 mm) und das

Fehlen der Geschlechtsorgane vom Adultus. Nymphen und Adulti

überwintern im Boden.

Gegenmaßnahmen:

1. Wiesen mit bekannten Milbenbefall meiden (zumeist Kuhweiden,

ausgesprochene Hundewiesen bzw. Wiesen, auf denen sich viele

Tiere bewegen). Ansonsten hochreichendes Schuhwerk (z.B.:

Gummistiefel) und geschlossene Bekleidung benutzen sowie den

Bodenkontakt vermeiden ("Hinsetzen" und "Hinlegen"). Zuhause

anschließend möglichst schnell duschen und neue Kleider an-

ziehen.

2. Einsatz von Repellents ("Insektenabwehrmittel"). Damit Schuhe,

Socken und Hosen imprägnieren. Allerdings reagieren manche

Menschen darauf sensitiv.

3. Im eigenem Garten (Rasen): Rasen bzw. Wiese oft mähen (die

Larven sitzen oben auf den Grashalmen). Den Grasschnitt nicht

auf dem Rasen liegen lassen (vernichten). Dieses führt zu einer

Minderung/Abwanderung der Grasmilben. Rasen nicht sonnen-

exponiert anlegen (Südseite). Der Abstand Rasens/Haus sollte

mindestens zwei bis drei Meter betragen.

4. Der Befall mit Grasmilben kann durch das Besprühen der be-

lasteten Rasenareale mit Carbaryl (Insektizid), Chlorpyrifos

(Insektizid) oder Diazinon (Antiparasitika) vermindert werden.

5. Nach erfolgten Bissen die Stellen unbedingt desinfizieren und

den Juckreiz mit Salben, Essig oder auch Zitronensaft lindern. (Bryboria graminum)

Vorkommen, Lebensweise

· Sie leben in Rasenflächen an den Gräsern - besonders in trockenem Rasen an der Südseite von Häusern vermehren sie sich massenhaft.

· Wenn die Rasenflächen bis an die Gebäude reichen, wandern die Milben bis in die Gebäude hinein, das kann bis in die Wintermonate andauern. Bekämpfung · Vorbeugend sollte der Rasen, oder die Gehwegplatten bzw. Kiesflächen zurückgenommen werden, der entstehende Streifen (ca. 2,00 m) sollte mit schattenspendenden Pflanzen besetzt werden.

· Damit wird die Temperatur herabgesetzt und die Milben werden die "kalte" Zohne nicht gern duchwandern.

· Eine chem. Bekämpfung außen sollte mit Spritzpulvern oder mikroverkapselten Präparaten ab etwa 50 cm Höhe erfolgen. (zum Schutz von Kindern und Haustieren)

· Chem. Bekämpfung innen mit Naturpyrethrum (nur wenn unbedingt notwendig) Milben gehören zu den Spinnentieren. Die meisten der über 60000 Arten sind so klein, daß sie mit bloßem Augen kaum wahrgenommen werden. Im Nahbereich des Menschen sind es jedoch nur 40 Milbenarten (darunter 6 Zeckenarten, die zu den Milben gerechnet werden), die Probleme oder sogar gesundheitliche Beeinträchtigungen verursachen können. Diese Arten finden sich in den folgenden drei der insgesamt sechs Milben-Unterordnungen: · Sarcoptiformes: Krätzmilbe, Hausstaubmilbe, Horn-u. Moosmilben sowie fast alle vorratsschädliche Milben

· Parasitiformes: Zecken und Vogelmilben

· : Laufmilben, z.B. Herbstmilben, Haarbalgmilben und Spinnmilben

· Notostigmata:

· Holothyroidea:

· Tetrapolidi:

Entwicklung allgemein: Milben durchlaufen zwischen Ei und adulten Tiermeist vier Entwicklungsstadien,bei manchen Arten sind es weniger. Damit sieht der Milbenzyklus wie folgt aus: Ei > sechsbeinig Larve > achtbeinige Proto > Deutonymphe > Tritonymphe > adultes Tier Mänchen und Weibchen können sehr verschieden aussehen. Milben können Dauernymphen bilden, die sich wenig oder gar nicht bewegen und sehr unempfindlich gegen Trockenheit und Extremtemperaturen sind.Das Dauerstadium der Mehlmilbe Acarus siro bleibt z.B. monatelang in trockenem Mehl am Leben, verträgt 14 Tage lang 34°C und bei 24h in -7°C werden nur 50% Abtötung erreicht. Schaden: · Das wichtigste Gesundheitsproblem, das im Zsammenhang mit Milben auftritt, ist die Allergieauslösung beim Menschen (Hausstaubmilbenallergie).

· Darüber hinaus ist der Genuß milbenhaltiger Lebensmittel schädlich.

Chiggers by Frederick P. Baxendale, Shripat T. Kamble and David L. Keith

Chiggers, also known as "redbugs, jiggers or harvest ", are the immature stages of a tiny red . They inhabit areas of tall grass, associated with low, wet spots, ponds and stream banks, wild berry patches and forest underbrush. The larvae attach themselves to the clothing of people or to the fur of passing . Before settling down to feed, chiggers move to a constriction such as sock tops, waist bands or armpits. Feeding chiggers inject a salivary fluid which dissolves the host's cells, then suck up the liquefied tissue. Within a few hours, small, reddish, intensely itching welts appear. These bites may continue to itch for several days up to two weeks after the chigger is dislodged. Following these suggestions should provide some protection from chiggers: Stay out of areas where chiggers are likely to be present including woodlots, pastures, roadside ditches or other areas with tall grasses and weeds. Chiggers are especially common in moist low-lying areas. Wear loose-fitting clothing and avoid sitting or reclining on the ground when camping, picnicking or working outdoors. Apply a repellent containing DEET (N,N-diethyl- meta-toluamide) to shoes, socks and trousers before entering chigger-infested areas. Caution: some individuals may be sensitive to DEET. Always read and follow label directions. Immediately after possible exposure to chiggers take a bath, thoroughly scrubbing the body with hot soapy water. This will kill or dislodge many of the chiggers. When bites begin to itch, one course of treatment is to apply rubbing alcohol, followed by one of the non-prescription local anesthetics. A baking soda paste, calamine lotion or product such as "After- Bite" also will help reduce discomfort. Avoid scratch- ing bites since this only increases irritation and may lead to secondary infection of the bite. Where chiggers are a problem in landscapes, keep lawns and shrubbery well manicured especially in areas adjacent to dwellings. Eliminate tall grasses and weeds. Chiggers also can be reduced by spraying infested foliage with carbaryl (Sevin), chlorpyrifos (Dursban) or diazinon.

File NF269 under: INSECTS AND PESTS H-1, Other Pests Issued May 1996 Electronic version issued August 1996

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Kenneth R. Bolen, Director of Cooperative Extension, University of Nebraska, Institute of Agriculture and Natural Resources. University of Nebraska Cooperative Extension educational programs abide with the non-discrimination policies of the University of Nebraska-Lincoln and the United States Department of Agriculture.

CHIGGERS

Chiggers are the larval form of a specific family of mites and are closely related to ticks. Chiggers are almost invisible to the naked eye, but when clustered together can be seen because of their natural bright red color. A widespread misconception is that chiggers burrow into the skin and eventually die there. The fact is they're not equipped to burrow under skin, and they don't drink blood. The chigger's mouth parts are short and delicate and can only penetrate thin skin or where skin wrinkles or folds: usually around ankles, backs of knees, waistline and armpits. The chigger injects a digestive enzyme that dissolves skin cells it contacts . The chigger then sucks up the liquified tissue. It can take 3 to 4 days to complete a meal if left undisturbed. If the chigger is removed before it completes its meal, it can't bite again and will eventually die. Chiggers are most active in temperatures between 77 - 86 degrees fahrenheit. Itching peaks in a day or two after the bite occurs and is a result of your body's defense against a foreign body. The longer the chigger feeds, the larger the welt surrounding the bite and the greater the intensity of itching. Your first line of defense is to wear proper clothing. Tightly woven socks and clothes, long pants, long sleeved shirts and high shoes or boots are ideal. Change clothes as soon as possible when you get home and wash them before wearing them again. The best precaution against chigger bites is a warm soapy shower/bath as soon as possible after exposure. You can wash them off before they bite and remove any attached chiggers before you start itching. If you can't bathe right away, you can remove chiggers by rubbing down with a towel or cloth. Attached chiggers are removed by even the lightest rubbing. Mosquito repellants can be used to repel chiggers, but must be replenished every 2 to 3 hours. No substance is completely effective in relieving the itch of a chigger bite, although there are many products available. Over the counter antihistamines, hydrocortisone creams and Calamine lotion may help, but be sure to read the labels as not everyone should use these medications. The only real danger from chigger bites is secondary infection that develops after scratching with dirty fingernails. If you do scratch, disinfect the bite with an antiseptic soap. Chiggers in North America do not carry Lyme disease or Rocky Mountain Spotted Fever. If you think your chigger bites are infected or if you have questions about medications, come to Student Health or see your health care provider. Signs of infection could include swelling, redness, fever and green/yellow discharge from bites.

http://sol.virologie.med.uni-giessen.de/drc/health/ebel9-3.html#chiggers MITES · Mites Species List · Fehler! Textmarke nicht definiert. (Trombiculidae) · common chigger, Fehler! Textmarke nicht definiert. (Oudemans) · Fehler! Textmarke nicht definiert. · Fehler! Textmarke nicht definiert. Ewing · Fehler! Textmarke nicht definiert. (Wolfenbarger) · Fehler! Textmarke nicht definiert. Gould · Fehler! Textmarke nicht definiert. (L.) · straw itch mite, Fehler! Textmarke nicht definiert. (Newport) (Pyemotidae) · tropical rat mite, Fehler! Textmarke nicht definiert. (Hirst) (Macronyssidae) · house mouse mite, Fehler! Textmarke nicht definiert. (Hirst) (= Allodermanyssus) (Macronyssidae) · northern fowl mite, Fehler! Textmarke nicht definiert. (Canestrini and Fanzago) (Macronyssidae) · chicken mite, Fehler! Textmarke nicht definiert. (De Geer) (Dermanyssidae) · human itch mite, Fehler! Textmarke nicht definiert. (Hering) (Sarcoptidae) · canine mange mite, Fehler! Textmarke nicht definiert. Gerlach, on Dogs and Humans Mites (order Acarina) are very small , with head and thorax fused into a cephalothorax. They have sucking mouthparts, no antennae, and those of interest as household pests have 4 pairs of legs as adults. Although most of these species have only 3 pairs of legs in the first (larval) stage after hatching from the egg, they gain a fourth pair in the second (nymphal) stage. The life cycle generally consists of the egg, larval stage, one or more nymphal instars or stages, and an adult stage. The life cycle usually requires only 2 or 3 weeks, and results in rapid increase and huge populations of mites under favorable conditions. A thorough discussion on the morphology and development of the free-living mites, on their role as parasites of animals and plants, and as vectors of disease, may be found in Mites, or the Acari by T. E. Hughes (1959). Chiggers (Trombiculidae) Chiggers or "red bugs," called "harvest mites" in Europe, are.the larvae of mites belonging to the suborder Trombidiformes, which are worldwide in distribution. There are over 200 families of mites, but the family to which chiggers belong (Trombiculidae) contains about 10% of all mite species (Sasa, 1961). Some species attack humans and cause a dermatitis (trombidiosis). The red welts and severe itching do not appear until several hours or even a day after exposure; therefore, it is difficult to know exactly when or where the infestation occurred. Several chiggers transmit a rickettsial disease called "scrub typhus" or "tsutsugamushi disease" in the Orient and various areas of the Pacific. Description. The members of the suborder Trombidiformes are characterized by the respiratory system, when present, opening in the region of the gnathosoma, the portion of the body bearing the mouth and its appendages. Chiggers are very small, 150 to 300 microns (0.15 to 0.3 mm) long when unengorged, and are red to pale yellow or white, depending on the species. Like all mite larvae, they have 6 legs. They are parasitic, but later stages are free-living, 8-legged mites. Only the larvae are harmful and only they are correctly referred to as "chiggers." The adults are bright red, hairy, or granular (Michener, 1946; Wharton and Fuller, 1952; Baker et al., 1956). The various stages of the trombiculid mites in general are adequately represented by Fehler! Textmarke nicht definiert., which shows an unengorged and engorged larva, a nymph, and an adult of Trombicula batatas (L.). common chigger, Trombicula alfreddugesi (Oudemans) In the Western Hemisphere, this is the most common and widespread species, ranging from Canada to South America and the West Indies. Trombicula alfreddugesi parasitizes many species of , , reptiles, and amphibians, as well as man. On humans, chiggers tend to congregate in areas constricted by clothing, such as ankles, crotch, waistline, and armpits. It is unfortunate that when chiggers attach to humans they are not noticed for some time, for they are easily removed. According to Baker et al. (1956): Itching is usually noted 3 to 6 hours after the chiggers have attached, and may persist for as long as 2 weeks. Part of the irritation is thought to be an allergic response to the salivary secretions of the mite. A papule forms at the site of attachment which may develop into a vesicle. Scratching usually removes the offending mite but, if repeated often enough, may result in an infection. In some regions, this mite is a.pest of chickens and turkeys, affecting the younger birds most seriously. When heavily parasitized, the birds become droopy, refuse to feed, and may eventually die from starvation and exhaustion (Baker et al., 1956). A much more important chigger pest of chickens and turkeys, however, is Neoschongastia americana (Hirst), which ranges across the southern United States from California to Georgia, but does not attack man (Kunz et al., 1969). Description. Chigger larvae are 0.15 to 0.25 mm long before engorgement, and are red to reddish orange, rarely white. Their mouthparts include 2 pairs of grasping palps provided with forked claws. The nymphs are much more hirsute than the larvae. The body is constricted behind the second pair of legs, giving them and the adults the characteristic shape of trombiculid mites shown in Fehler! Textmarke nicht definiert.. The adults are much larger than the nymphs, and are even more hirsute. They are 0.9 to 1.1 mm long, and brilliant red (Jenkins, 1949; Baker et al., 1956). Life Cycle. The spherical eggs, approximately 0.1 to 0.2 mm in diameter, are usually laid in the soil. The larva crawls about on the surface of the soil until it finds a suitable vertebrate host. It attaches to the host by means of its chelicerae and sucks blood, but as a rule does not burrow under the skin. Engorgement usually takes about 3 days. The larva then drops, enters the soil, and changes, via the nymphochrysalis, to the nymphal stage. The nymphs probably feed on the eggs and young instars of small arthropods. The adult emerges from a dorsal split in the imagochrysalis and nymphal cuticle (Baker et al., 1956). The life cycle may require 2 to 12 months or longer, depending on the temperature. There may be 1 to 3 generations per year in temperate climatic zones, but reproduction may be continuous throughout the year in warmer regions, with as many as 6 generations. Females kept at suitable temperatures and supplied with water and food were observed to live more than a year and to produce larvae throughout that period. The time when chiggers are active varies from 2 months in Minnesota and Massachusetts to the entire year in southern Florida. Chiggers are most abundant during rainy spells in the area from Kansas to Texas, and may disappear during hot, dry weather (Jenkins, 1948). Some Related Species Trombicula splendens Ewing is a related species in the eastern United States. It prefers moister habitats, such as swamps and rotten logs or stumps. It is one of the most common causes of trombidiosis in the southeastern states. Trombicula lipovskyana (Wolfenbarger) may be found in similar places in Tennessee, Kansas, Oklahoma, and Arkansas. Trombicula belkini Gould is widely distributed in California, and has also been collected in Utah. Reptiles seem to be its favored hosts, but it also infests rodents and ground birds. It sometimes annoys humans and their pets (CEIR, 1960). This species is closely related to T. alfreddugesi, but the larvae lack nude, whiplike setae on the tarsus of leg II (Baker et al., 1956; Gould, 1956). Trombicula batatas (L.) (Fehler! Textmarke nicht definiert.) is common in Central and South America, the state of Puebla, Mexico, and has been reported from the southeastern United States (Michener, 1946; Jenkins, 1948). It has been collected on humans and many domestic and wild animals. One 12-year-old boy had 138 attached larvae (Michener, 1946). It has been reported to attack humans in the San Joaquin Valley of California (Doetschman and Furman, 1949). Gould (1956) published an extensive monographic study of the larval trombiculid mites of California. Favored Habitats. Chiggers are most abundant in areas that support thickets or scrub- type vegetation and where the ground is undisturbed, supporting many rabbits, other rodents, and various small host animals. They are generally eliminated automatically by habitat destruction in areas that are heavily populated or intensively farmed. In new urban subdivisions, however, chiggers may persist in lawns for several years. To determine the exact area of chigger infestation, a piece of black cardboard can be placed edgewise on the ground where an infestation is suspected. If chiggers are present, the tiny yellow or pink larvae will crawl rapidly over the cardboard and accumulate on the upper edge. Chiggers can also be easily detected on black, polished shoes (USDA, 1963). Jenkins (1948) suggested the possibility that chiggers might be of value in decreasing mosquito populations. The adults were often abundant in depressions in the ground which had become temporary pools containing Aedes and Psorophora larvae in the spring. Mosquito eggs laid in such depressions probably were serving as food for Trombicula adults. Repellents. In areas where chiggers are known to be a problem, the avoidance of their favored habitats is, of course, a way of minimizing infestation. Protective clothing and repellents are recommended as already described for protection against mosquitoes and ticks. If infested, a thorough soapy bath as soon as possible is a highly effective treatment. Repeat the lathering and rinsing several times. Most of the chiggers, attached or unattached, will be killed. Among the best repellents for chiggers are those containing diethyl toluamide (OFF), ethyl hexanediol (6-12), and dimethyl phthalate, applied to the skin and clothing around the ankles, waist, and armpits. To apply dusting sulfur to skin and clothing is an old but effective method of preventing chiggers. Repellents should be applied particularly to the legs, ankles, cuffs, waist, and sleeves. Some relief from itching can be obtained by applying a solution of 5% benzocaine, 2% methyl salicylate, 0.5% salicylic acid, 73% ethyl alcohol, and 19.5% water. This can be prepared by a druggist. It may be applied to each welt with a piece of cotton. Each treatment gives relief for an hour or more (USDA, 1963). Control. Good control of chiggers in the field can be obtained for 1 or 2 months with toxaphene at 2 lb (0.91 kg) or lindane at 0.25 lb (0.11 kg) of actual toxicant per acre, preferably as emulsions. The amount of water used as a carrier of such quantities depends, of course, on the type of spray equipment available. A given quantity of insecticide can be used with either a large or small quantity of water, as long as the toxicant is thoroughly and uniformly distributed. The following quantities (stated as emulsifiable concentrates) of 4 insecticides that are effective against chiggers as well as insects have been recommended (Anonymous, 1970d). Insecticide and formulation For 1,000 sq ft (93 sq m) For 1 acre (0.405 ha) Chlordane 45% 10 tsp (50 cc) 3 pt (1,440 cc) Toxaphene 60% 7 tsp (35 cc) 2 pt (960 cc) Diazinon 25% 0.5 pt (240 cc) 2.50 gal (9.50 1) Malathion 57% 0.5 pt (240 cc) 2.50 gal (9.50 1) A convenient way to treat 1,000 sq ft (93 sq m) of lawn would be to mix any one of the formulations shown in the table with 3 gal (11 L) of water, but if weeds or tall grass were present, the same quantities of insecticide could be more effectively applied in 6 gal (22 L) of water. To spray an acre (0.405 ha), at least 25 gal (95 L) of water are required. Malathion treatments may need to be repeated because malathion is nonpersistent. There are also dust formulations of these insecticides that can be used effectively for chigger control. (Consult appropriate authorities about pesticides currently authorized.)

http://entmuseum9.ucr.edu/ent133/ebeling/ebel9-3.html

MITES · Mites Species List · Fehler! Textmarke nicht definiert. (Trombiculidae) · common chigger, Fehler! Textmarke nicht definiert. (Oudemans) · Fehler! Textmarke nicht definiert. · Fehler! Textmarke nicht definiert. Ewing · Fehler! Textmarke nicht definiert. (Wolfenbarger) · Fehler! Textmarke nicht definiert. Gould · Fehler! Textmarke nicht definiert. (L.) · straw itch mite, Fehler! Textmarke nicht definiert. (Newport) (Pyemotidae) · tropical rat mite, Fehler! Textmarke nicht definiert. (Hirst) (Macronyssidae) · house mouse mite, Fehler! Textmarke nicht definiert. (Hirst) (= Allodermanyssus) (Macronyssidae) · northern fowl mite, Fehler! Textmarke nicht definiert. (Canestrini and Fanzago) (Macronyssidae) · chicken mite, Fehler! Textmarke nicht definiert. (De Geer) (Dermanyssidae) · human itch mite, Fehler! Textmarke nicht definiert. (Hering) (Sarcoptidae) · canine mange mite, Fehler! Textmarke nicht definiert. Gerlach, on Dogs and Humans Mites (order Acarina) are very small arthropods, with head and thorax fused into a cephalothorax. They have sucking mouthparts, no antennae, and those of interest as household pests have 4 pairs of legs as adults. Although most of these species have only 3 pairs of legs in the first (larval) stage after hatching from the egg, they gain a fourth pair in the second (nymphal) stage. The life cycle generally consists of the egg, larval stage, one or more nymphal instars or stages, and an adult stage. The life cycle usually requires only 2 or 3 weeks, and results in rapid increase and huge populations of mites under favorable conditions. A thorough discussion on the morphology and development of the free-living mites, on their role as parasites of animals and plants, and as vectors of disease, may be found in Mites, or the Acari by T. E. Hughes (1959). Chiggers (Trombiculidae) Chiggers or "red bugs," called "harvest mites" in Europe, are.the larvae of mites belonging to the suborder Trombidiformes, which are worldwide in distribution. There are over 200 families of mites, but the family to which chiggers belong (Trombiculidae) contains about 10% of all mite species (Sasa, 1961). Some species attack humans and cause a dermatitis (trombidiosis). The red welts and severe itching do not appear until several hours or even a day after exposure; therefore, it is difficult to know exactly when or where the infestation occurred. Several chiggers transmit a rickettsial disease called "scrub typhus" or "tsutsugamushi disease" in the Orient and various areas of the Pacific. Description. The members of the suborder Trombidiformes are characterized by the respiratory system, when present, opening in the region of the gnathosoma, the portion of the body bearing the mouth and its appendages. Chiggers are very small, 150 to 300 microns (0.15 to 0.3 mm) long when unengorged, and are red to pale yellow or white, depending on the species. Like all mite larvae, they have 6 legs. They are parasitic, but later stages are free-living, 8-legged mites. Only the larvae are harmful and only they are correctly referred to as "chiggers." The adults are bright red, hairy, or granular (Michener, 1946; Wharton and Fuller, 1952; Baker et al., 1956). The various stages of the trombiculid mites in general are adequately represented by Fehler! Textmarke nicht definiert., which shows an unengorged and engorged larva, a nymph, and an adult of Trombicula batatas (L.). common chigger, Trombicula alfreddugesi (Oudemans) In the Western Hemisphere, this is the most common and widespread species, ranging from Canada to South America and the West Indies. Trombicula alfreddugesi parasitizes many species of mammals, birds, reptiles, and amphibians, as well as man. On humans, chiggers tend to congregate in areas constricted by clothing, such as ankles, crotch, waistline, and armpits. It is unfortunate that when chiggers attach to humans they are not noticed for some time, for they are easily removed. According to Baker et al. (1956): Itching is usually noted 3 to 6 hours after the chiggers have attached, and may persist for as long as 2 weeks. Part of the irritation is thought to be an allergic response to the salivary secretions of the mite. A papule forms at the site of attachment which may develop into a vesicle. Scratching usually removes the offending mite but, if repeated often enough, may result in an infection. In some regions, this mite is a.pest of chickens and turkeys, affecting the younger birds most seriously. When heavily parasitized, the birds become droopy, refuse to feed, and may eventually die from starvation and exhaustion (Baker et al., 1956). A much more important chigger pest of chickens and turkeys, however, is Neoschongastia americana (Hirst), which ranges across the southern United States from California to Georgia, but does not attack man (Kunz et al., 1969). Description. Chigger larvae are 0.15 to 0.25 mm long before engorgement, and are red to reddish orange, rarely white. Their mouthparts include 2 pairs of grasping palps provided with forked claws. The nymphs are much more hirsute than the larvae. The body is constricted behind the second pair of legs, giving them and the adults the characteristic shape of trombiculid mites shown in Fehler! Textmarke nicht definiert.. The adults are much larger than the nymphs, and are even more hirsute. They are 0.9 to 1.1 mm long, and brilliant red (Jenkins, 1949; Baker et al., 1956). Life Cycle. The spherical eggs, approximately 0.1 to 0.2 mm in diameter, are usually laid in the soil. The larva crawls about on the surface of the soil until it finds a suitable vertebrate host. It attaches to the host by means of its chelicerae and sucks blood, but as a rule does not burrow under the skin. Engorgement usually takes about 3 days. The larva then drops, enters the soil, and changes, via the nymphochrysalis, to the nymphal stage. The nymphs probably feed on the eggs and young instars of small arthropods. The adult emerges from a dorsal split in the imagochrysalis and nymphal cuticle (Baker et al., 1956). The life cycle may require 2 to 12 months or longer, depending on the temperature. There may be 1 to 3 generations per year in temperate climatic zones, but reproduction may be continuous throughout the year in warmer regions, with as many as 6 generations. Females kept at suitable temperatures and supplied with water and food were observed to live more than a year and to produce larvae throughout that period. The time when chiggers are active varies from 2 months in Minnesota and Massachusetts to the entire year in southern Florida. Chiggers are most abundant during rainy spells in the area from Kansas to Texas, and may disappear during hot, dry weather (Jenkins, 1948). Some Related Species Trombicula splendens Ewing is a related species in the eastern United States. It prefers moister habitats, such as swamps and rotten logs or stumps. It is one of the most common causes of trombidiosis in the southeastern states. Trombicula lipovskyana (Wolfenbarger) may be found in similar places in Tennessee, Kansas, Oklahoma, and Arkansas. Trombicula belkini Gould is widely distributed in California, and has also been collected in Utah. Reptiles seem to be its favored hosts, but it also infests rodents and ground birds. It sometimes annoys humans and their pets (CEIR, 1960). This species is closely related to T. alfreddugesi, but the larvae lack nude, whiplike setae on the tarsus of leg II (Baker et al., 1956; Gould, 1956). Trombicula batatas (L.) (Fehler! Textmarke nicht definiert.) is common in Central and South America, the state of Puebla, Mexico, and has been reported from the southeastern United States (Michener, 1946; Jenkins, 1948). It has been collected on humans and many domestic and wild animals. One 12-year-old boy had 138 attached larvae (Michener, 1946). It has been reported to attack humans in the San Joaquin Valley of California (Doetschman and Furman, 1949). Gould (1956) published an extensive monographic study of the larval trombiculid mites of California. Favored Habitats. Chiggers are most abundant in areas that support thickets or scrub- type vegetation and where the ground is undisturbed, supporting many rabbits, other rodents, and various small host animals. They are generally eliminated automatically by habitat destruction in areas that are heavily populated or intensively farmed. In new urban subdivisions, however, chiggers may persist in lawns for several years. To determine the exact area of chigger infestation, a piece of black cardboard can be placed edgewise on the ground where an infestation is suspected. If chiggers are present, the tiny yellow or pink larvae will crawl rapidly over the cardboard and accumulate on the upper edge. Chiggers can also be easily detected on black, polished shoes (USDA, 1963). Jenkins (1948) suggested the possibility that chiggers might be of value in decreasing mosquito populations. The adults were often abundant in depressions in the ground which had become temporary pools containing Aedes and Psorophora larvae in the spring. Mosquito eggs laid in such depressions probably were serving as food for Trombicula adults. Repellents. In areas where chiggers are known to be a problem, the avoidance of their favored habitats is, of course, a way of minimizing infestation. Protective clothing and repellents are recommended as already described for protection against mosquitoes and ticks. If infested, a thorough soapy bath as soon as possible is a highly effective treatment. Repeat the lathering and rinsing several times. Most of the chiggers, attached or unattached, will be killed. Among the best repellents for chiggers are those containing diethyl toluamide (OFF), ethyl hexanediol (6-12), and dimethyl phthalate, applied to the skin and clothing around the ankles, waist, and armpits. To apply dusting sulfur to skin and clothing is an old but effective method of preventing chiggers. Repellents should be applied particularly to the legs, ankles, cuffs, waist, and sleeves. Some relief from itching can be obtained by applying a solution of 5% benzocaine, 2% methyl salicylate, 0.5% salicylic acid, 73% ethyl alcohol, and 19.5% water. This can be prepared by a druggist. It may be applied to each welt with a piece of cotton. Each treatment gives relief for an hour or more (USDA, 1963). Control. Good control of chiggers in the field can be obtained for 1 or 2 months with toxaphene at 2 lb (0.91 kg) or lindane at 0.25 lb (0.11 kg) of actual toxicant per acre, preferably as emulsions. The amount of water used as a carrier of such quantities depends, of course, on the type of spray equipment available. A given quantity of insecticide can be used with either a large or small quantity of water, as long as the toxicant is thoroughly and uniformly distributed. The following quantities (stated as emulsifiable concentrates) of 4 insecticides that are effective against chiggers as well as insects have been recommended (Anonymous, 1970d). Insecticide and formulation For 1,000 sq ft (93 sq m) For 1 acre (0.405 ha) Chlordane 45% 10 tsp (50 cc) 3 pt (1,440 cc) Toxaphene 60% 7 tsp (35 cc) 2 pt (960 cc) Diazinon 25% 0.5 pt (240 cc) 2.50 gal (9.50 1) Malathion 57% 0.5 pt (240 cc) 2.50 gal (9.50 1) A convenient way to treat 1,000 sq ft (93 sq m) of lawn would be to mix any one of the formulations shown in the table with 3 gal (11 L) of water, but if weeds or tall grass were present, the same quantities of insecticide could be more effectively applied in 6 gal (22 L) of water. To spray an acre (0.405 ha), at least 25 gal (95 L) of water are required. Malathion treatments may need to be repeated because malathion is nonpersistent. There are also dust formulations of these insecticides that can be used effectively for chigger control. (Consult appropriate authorities about pesticides currently authorized.) straw itch mite, Pyemotes ventricosus (Newport) (Pyemotidae) This extremely small mite, almost invisible to the unaided eye, is primarily a parasite of certain insects, including 3 moths, 10 beetles, 4 wasps and bees, a bug, a fly, and a termite. Some of these host insects infest straw, wheat, stored food products, straw mattresses, and wood, and are therefore found in the home. The straw itch mite has also been called "grain itch," "hay itch," and "straw mattress" mite. Humans can become infested, with resulting dermatitis, by coming in contact with materials such as straw, hay, grasses, grains, and even beans, peas, cottonseed, tobacco, and broomcorn that have been infested with insect larvae upon which the mites feed. These mites also attack horses, cattle, and possibly other mammals (Goldberger and Schamberg, 1909; Baker et al., 1956; A. M. Hughes, 1961; Fine and Scott, 1963, 1965; Scott and Fine, 1963, 1964, 1967; Butler, 1972).

Description. The female is an almost microscopically small,. elongate mite (Fehler! Textmarke nicht definiert.), 0.22 mm long and white to yellow in color. When gravid, she becomes greatly distended behind the fourth pair of legs, and attains a length of up to 2 mm. Her abdomen shows traces of lateral segmentation, and she has clublike hair between the first and second pairs of legs. The male is only 0.16 mm long, but is wider than the female. Life Cycle. This mite has a strange and unusual biology. The males wander continuously over the distended body of the pregnant female, feeding on it parasitically. The large eggs hatch, and 206 to 300 mites develop to adulthood within the female's enlarged abdomen. They are extruded at the rate of about 50 per day. Only some 3% are males, but they emerge first and remain clustered around the genital opening. With the aid of their hind legs, they drag the females through the opening, even though they can emerge unassisted, and copulation takes place immediately. The females then search for hosts. Only 6 to 10 days are required from the time of fertilization to the hatching of eggs. The mites are active during the warmer months of the year at 80 °F (27 °C) or above (Baker et al., 1956; Scott and Fine, 1963). Distribution of Bites. The bites of straw itch mites are characteristically distributed almost exclusively on clothed portions of the body, although they occur rarely on other areas, with the exceptions of the palms, soles, and mucous membranes. There is no tendency for the mites to be grouped, although this sometimes occurs fortuitously. A person may feel a prickling sensation at the time of the bite, but otherwise no immediate reaction seems to occur. The period between the time of the bite and the delayed reaction has been variously reported as 10 to 16, 16, 27, and 17 to 28 hours (Fine and Scott, 1965). Straw Itch Mite Dermatitis. A considerable number of epidemics of dermatitis have been traced to infestation by Pyemotes ventricosus. Since many such outbreaks have not been recorded or correctly diagnosed, it is likely that this ailment is more common than is generally realized. Straw itch mite dermatitis is usually associated with sleeping on straw mattresses, harvesting grain, or otherwise handling or coming in contact with grain, straw, hay or other substances such as those just mentioned. The possibility of infestation is particularly strong if there are large numbers of the mites' host insects present, such as the Angoumois grain moth (Sitotroga cerealella) and the wheat jointworm (Harmolita tritici). The host insect need not necessarily be a species associated with hay or grain. For example, cases of straw itch mite dermatitis have been associated with severe infestations of furniture beetles (Anobium punctatum) in the floor joists of houses. The recurrence of such cases during the same season for 3 successive years led investigators to conclude that the mites migrated in search of new hosts as the adult beetles emerged and left the wood. The mites apparently were not able to penetrate the thick exoskeletons of the beetles when the latter were in the pupal and adult stages, and therefore they left and sought new hosts. In one house, the mites were controlled by treating the floors with 2% deodorized malathion emulsion (Fine and Scott, 1963, 1965; Scott and Fine, 1963). Treatment and Prevention. The treatment of symptoms is not the solution to the problem. Either a person must avoid infested areas, or the mites and their host insects must be eliminated.

Institut für medizinische Parasitologie

Merkblatt zum Problem der Trombidiose des Menschen Erreger: Die Verursacher der Trombidiose sind verschiedene Arten von Laufmilben (lat. Trombiculiden), von denen mehrere den Menschen befallen können. Die deutschen Bezeichnungen wie Herbstmilbe, Herbstlaus, Erntemilbe stellen einen Bezug zu bestimmten Jahreszeiten her, Namen wie Grasmilbe, Heumilbe, Stachelbeermilbe, Pfirsichlaus, Birkenlaus etc. zum Vorkommen in bestimmter Vegetation. Die in Deutschland vermutlich häufigste Art heißt Neotrombicula autumnalis oder Herbstmilbe. Der Name täuscht jedoch, denn je nach Art oder Unterart, aber auch in Abhängigkeit vom Standort und von den Witterungsbedingungen, können Belästigungen von März bis Oktober auftreten. Lebenszyklus: Die erwachsenen Milben und die Nymphen (letztes Larvenstadium), z. B. von Neotrombicula autumnalis, leben räuberisch von anderen Kleinstlebewesen. Nur die ca. 0,3 mm großen sechsbeinigen Larven nehmen als echte Parasiten Gewebsflüssigkeit und Lymphe auf. Nach dem Saugen am natürlichen Wirt (Kleinsäuger, v. a. Mäuse, und Vögel) fallen sie ab und häuten sich im Boden nach einiger Zeit zur Nymphe. In Wohnungen können sie sich offenbar nicht weiterentwickeln. Klinische Erscheinungen: Der Mensch wird beim Aufenthalt in Vegetationsgebieten, die von Milben besiedelt sind, bei zufälligem Kontakt befallen. Auf dem Menschen laufen die Milben dann oft größere Strecken, bis sie zum Stich ansetzen. Bevorzugte Stichstellen sind Hautareale, an denen die Kleidung eng anliegt, z. B. Knöchel und Taille. Mit ihren Mundwerkzeugen verletzen sie unbemerkt die obere Hautschicht und injizieren Speichel in die Wunde, der das epitheliale Gewebe verdaut. Das verflüssigte Gewebe wird aufgesogen. Meist bleiben die Milbenlarven nur wenige Stunden auf dem Menschen, da sie durch scheuernde Kleidung, Kratzen oder Hygienemaßnahmen entfernt werden. Sie werden deswegen oft nicht gefunden, wenn 4-36 Stunden nach dem Stich heftiger Juckreiz auftritt, der sein Maximum meist am 2.-3. Tag erreicht und länger als eine Woche andauern kann. Manche Personen erreichen einen hohen Grad an Desensibilisierung, d. h. sie erkranken nicht mehr bei Wiederbefall. Therapie und Prophylaxe: Zur Linderung des Juckreizes und Verhinderung von Sekundärinfektionen, die meistens für länger anhaltende Reaktionen verantwortlich sind, empfiehlt sich eine sofortige Behandlung mit 70%igem Alkohol und speziellen juckreizstillenden Mitteln, wie Soventol-Gel® u. ä.. Prophylaktisch können Repellentien (Autan®) oder Insektizide (pflanzliches Pyrethrum) auf Schuhe oder Kleidung aufgetragen werden. Vorkommen der Milben im Freien: Die Milben sind von ausreichender Boden- und Luftfeuchtigkeit sowie Lufttemperatur abhängig. Darin begründet ist vermutlich das oft „inselartige“ Vorkommen der Milbenplage. Ein entsprechendes Mikroklima können Moos- oder Humusschichten, Mulch, Grasschnitt etc. bieten, andererseits müssen aber auch die natürlichen Wirte im selben Lebensraum vorkommen. Dies sind vor allem Waldmaus (Apodemus sylvaticus), Gelbhalsmaus (Apodemus flavicollis), Feldmaus (Microtus arvalis) und Erdmaus (Microtus agrestis) sowie die Ratte (Rattus norvegicus). Bekämpfung: Aussichtsreich erscheint eine Beseitigung der Nistplätze von Nagetieren. Wichtig ist auch ein regelmäßiges Umsetzen von Komposthaufen, die Mäusenester beherbergen können und dann eine zentrale Rolle für die Verbreitung der Trombiculiden einnehmen. Vom Einsatz von Insektiziden resp. Akariziden muß wegen der Umweltbelastung und ungenügender Wirkung dringend abgeraten werden. Pauschale Empfehlungen zur Milbenbekämpfung können nicht gegeben werden, da bisherige Bekämpfungsmaßnahmen sehr widersprüchliche Ergebnisse lieferten. Für eine Problemlösung sind weitere Erkenntnisse zur Milbenbiologie erforderlich, die Gegenstand aktueller Forschung ist.

Weitere Auskünfte: Dr. rer. nat. Helge Kampen, e-mail: Fehler! Textmarke nicht definiert.

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