Family. Tyroglyphidæ.

Sub-family. Tyroglyphinæ.

Genus. Aleurobius, Canestrini.

Aleurobius (Tyroglyphus) farinæ, de Geer (part), Koch.

The male measures 0·33 mm. in length by 0·16 mm. in breadth; the female 0·6 mm. in length by 0·3 mm. in breadth. These mites possess five pairs of suctorial organs of a light colour; the legs are reddish. Moniez observed them in Lille on the skin of labourers who had been unloading Russian corn. A few of the species generally mentioned under the designation of Tyroglyphus siro are probably the common flour-mite, which also occurs on dry cheese.

[The farinæ of de Geer is an Aleurobius described by him in 1778 (“Mém. Hist. Ins.,” vii, t. 5, f. 15, p. 97) as Acarus farinæ.—F. V. T.]

Genus. Tyroglyphus, Latreille.

Tyroglyphus siro, L., 1756.
(Defined by Gervais, 1844.)

Male 0·5 mm. in length by 0·25 mm. in breadth; female 0·53 mm. in length by 0·28 mm. in breadth; the males have two suckers on the tarsi of the fourth pair of legs. Penis straight, colour whitish or reddish.

Tyroglyphus longior, Gervais, 1844.

White or yellowish, with two black spots on the abdomen. Male 0·55 mm. in length, 0·28 mm. in breadth; penis bent. Female 0·61 mm. in length and 0·28 mm. in breadth.

T. siro and T. longior live on dry cheese, in flour, on dried fruits, etc., and have been occasionally observed in the stools, urine, or pus of human beings, and also on their skin. The so-called vanillismus is to be attributed to these species.

[T. siro and T. farinæ of Schrank (non Geer) are the same. They are described under other names, such as Acarus lactis, Linn.; A. favorum, Herm., etc.; A. lactis in milk, farinæ in flour, and siro in cheese; and as A. dysenteriæ, Linnæus (“Syst. Nat.,” ed. 12, pp. 1024–1767).]

It is to these species that a case of dysentery was referred. Rolander, who studied under Linnæus, was attacked by what was called dysentery. The complaint soon gave way to treatment, but eight days after it returned, soon disappeared, but again came a third time. All the time Rolander had been living like the other inmates of the house, who all escaped. Linnæus, aware that Bartholemy had attributed dysentery to insects which he said he had seen, advised his student to examine his stool. The result was that innumerable mites were found to be present. Their presence was easily accounted for by the fact that they were found in numbers in a cup made of juniper wood from which the student alone drank of a night, and they were found to be of the same species. What this species is we do not know. Linnæus called it Acarus dysenteriæ, but it was the same as his Acarus siro. No records have occurred since. It cannot be, as Latreille supposed, the cheese mite, for they have been eaten by millions since, and it is strange no such case has occurred again.

[Tyroglyphus minor var. Castellani, Hirst,

causes the copra itch in persons employed in the copra mills in Ceylon. The skin of the hands, arms, legs and even body becomes covered with pruriginous papules, papulo-pustules and pustules near the head. The eruption begins as a rule on the hands. The mites live in the copra dust. They produce dermatitis. Castellani produced the disease experimentally by rubbing copra dust containing mites on the skin of healthy people. Beta-naphthol ointment (5 to 10 per cent.) proved useful in treatment (Journ. Trop. Med. and Hyg., December 16, 1912, Castellani and Hirst).—F. V. T.]

Genus. Glyciphagus, Hering, 1838.

Glyciphagus prunorum, Her., and G. domesticus, de Geer.

The Glyciphagi are differentiated from the Tyroglyphi in that the chitinous hairs on the body are fringed or feathered, and that they lack a furrow dividing the cephalothorax from the abdomen. They live under similar conditions to the Tyroglyphi and are occasionally found on man or in fæces.

[Sugar merchants and grocers are frequently troubled by swarms of G. domesticus, which leave the stores when being handled, and especially shopmen, who handle sugar kept in small stores for some time. These are the Acari that cause that irritating temporary affection known as “grocer’s itch.”—F. V. T.]

Glyciphagus cursor, Gervais.

Under this name Signor Moriggia figures a horny excrescence of great length growing from a woman’s hand, and containing in its cavities quantities of Acarus. This species is really G. domesticus, de Geer. G. domesticus has also been described by Gervais (Ann. Sci. Nat., 1841, ser. 2, xv, p. 8) as G. hippopodes.

Glyciphagus buski, Murray.350

[This is a mite found by Busk and named after him by Murray. It was taken from beneath the cuticle of the sole of the foot of a negro in the Seamen’s Hospital Ship on the Thames in 1841, in large sores of a peculiar character confined to the soles of the feet. It appeared that the disease was caused by its burrowing beneath the thick cuticle. The disease was attributed to the wearing of a pair of shoes which had been lent to another negro whose feet had been similarly affected for nearly a year. The negro to whom the shoes were lent came from Sierra Leone. Mr. Busk stated that some water brought by Dr. Stranger from the River Sinoe, on the coast of Africa, contained one nearly perfect specimen, and fragments of others very similar to if not identical with this Acarus. Mr. Busk adds that he had been informed by Staff-Assistant Surgeon P. D. Murray that at Sierra Leone there is a native pustular disease called craw-craw—a species of itch breaking into open sores.

[From Busk’s original figure I see no reason to doubt that this is a Glyciphagus.—F. V. T.]

Genus. Rhizoglyphus, Claparède, 1869.

Rhizoglyphus parasiticus, Dalgetty, 1901.

This species has been observed on the feet of Indian coolies working in the tea plantations; they produce a skin disease which always commences with blebs between the toes, and which almost always extends to the malleoli, but not beyond. The Acari have an elliptical body, which is grey, but varies from greenish-yellow to greenish-brown when the stomach is full. Eyes are absent. The legs are composed of five segments and terminate with a claw. The males measure 0·18 mm. in length by 0·08 mm. in breadth, and possess genital and anal pores; the females measure 0·2 mm. in length by 0·09 mm. in breadth.351 [This is also known as coolie itch and is common in Indian tea plantations.—F. V. T.]

Genus. Histiogaster, Berlese, 1883.

Histiogaster (entomophagus?) spermaticus, Trouessart, 1900.

This species has been described by Trouessart,352 who found numerous specimens, some adult, others in the developmental stage (larvæ, nymphs), and ova, in the fluid removed by puncture from a cyst of the right testis. The males measure 0·25 mm., the females 0·32 mm., and the larvæ 0·1 mm. in length. The author is of opinion that the animal—perhaps a fertilized female—was introduced by a catheter, and, as a matter of fact, it was afterwards found that the patient had once had the catheter passed in India while suffering from pernicious fever.

It would here rather appear to be the case of a facultative parasitism of an otherwise free-living species. Histiogaster entomophagus, Laboulbène, is found occasionally in collections of insects feeding on larger species containing much fat; the species also occurs on dry cantharides; it appears to belong to the region of South Europe, where, however, it is widely spread.

[Entomophagus occurs all over Europe and in America. It has been described under the following names: Acarus malus, Shimer, 1868 (Trans. Illinois Hort. Soc.); Dermaleichus mali, Riley, 1873 (Rep. Ins. Missouri, v, p. 87); Tyroglyphus mali, Murray, 1877 (“Eco. Ent. Apt.,” p. 275); T. corticalis, Michael, 1885 (Trans. Roy. Micros. Soc., ser. 2, v, 3, p. 27, figs. 1 to 14); Histiogaster corticalis, Canestrini, 1888 (Prosp. Acarof., iii, p. 397); H. aleurophagus, Sicherin, 1894, Canestrini, Prosp. Acarof., vi, p. 815. Trouessart’s species is evidently distinct.—F. V. T.]

Genus. Cheyletus.

Cheyletus mericourti, Lab.

Acaropsis mericourti, Moq. Tand.

[This mite has been described from three specimens found in pus which flowed from an abscess in the ear of a naval officer, produced by inflammation of the auditory passage. Where the mites came from we do not know, as they were found near the Bank of Newfoundland. This genus of Acari has enormous mandibles and a peculiar tracheal system; two ungues and appendages to the tarsi.—F. V. T.]

Family. Sarcoptidæ (Itch Mites).

Sub-family. Sarcoptinæ.

Genus. Sarcoptes, Latreille.

Sarcoptes scabiei, de Geer, 1778.

Syn.: Acarus scabiei, de Geer, 1778; A. psoricus, Pallas, 1760; A. siro, L., 1778; Sarcoptes exulcerans,? Linn., 1758, Nitsch, 1818; S. hominis, Raspail, 1834, and Hering, 1838; S. galei, Owen, 1853; S. communis, Delaf. et Bourg., 1862; S. scabiei var. hominis, Mégnin, 1880.

The body is oval or nearly circular and whitish in colour, with transverse rows of striæ partly interrupted on the back. There are transverse rows of small bristles on the dorsal surface, and groups of trichomæ on the front, sides and back. There are chitinous hairs at the base of the legs; the two first pairs are provided with pedunculated ambulacra in both sexes, the two posterior pairs terminate each with a long bristle in the female; in the male the third pair of legs terminate in a bristle, the fourth pair with a pedunculated ambulacrum. The anus is situated at the posterior border of the dorsal surface.

At one time numerous species were differentiated, according to the form of the Acarus, the number, position and size of the hairs and spines, even according to the hosts, etc. All these characteristics, however, fluctuate so considerably that absolute differentiation is impossible; the supposed species may be regarded in the same light as Mégnin did, as varieties. It is also hardly possible to distinguish the mite of human scabies (S. hominis) from that of a number of domestic animals (S. squamiferus). It is best, therefore, to accept one single species (S. scabiei), which may give rise to different races or castes by living in the skin of man and mammals, but can pass from one host to the other.

[Canestrini and Kramer, in their monograph of the Sarcoptidæ, enumerate eighteen distinct species of this genus, from the dog, goat, camel, horse, ferret, lion, wolf, sheep, pig, etc., and two species parasites of man (scabiei and scabiei-crustosæ). There is no doubt that they are distinct species.—F. V. T.]

The S. scabiei of man (S. scabiei var. hominis) (length of male 0·2 to 0·3 mm., and breadth 0·145 to 0·190 mm.; length of female 0·33 to 0·45 mm., and breadth 0·25 to 0·35 mm.) lives in the tunnels that it excavates in the epidermis, and attacks by preference places with thin skin, such as between the fingers, in the bend of the elbows and knees, in the inguinal region, on the penis, on the mammæ, but may also affect other parts. The tunnels, which vary from a few millimetres to a centimetre and more long, do not run straight, but are somewhat tortuous; the female is found at the terminal end. The tunnels contain the excrement and oval eggs (0·14 mm. in length) of the parasite; the males are rarely met with, as they die off after copulation; the females die after depositing their eggs. The six-legged larvæ hatch out after four to eight days, and after about a fortnight, during which time they change their skins three times and undergo metamorphosis, they begin themselves to burrow. Transmission from person to person rarely is effected through linen, but by direct contact (as in coitus); transmission can be artificially effected on horses, dogs and monkeys, but not on cats.

The smaller S. scabiei-crustosæ, Fürstenberg, is the cause of the itch that occurs chiefly in Norway; it is not certain whether this is a distinct species of itch mite.

[This is quite a distinct species, which is recorded from Germany and France. Mégnin (Parasitology, 1880, p. 165) described this as S. scabiei var. lupi. The female is 140 µ long, 340 µ broad; the male is 170 µ long by 150 µ broad. In Science (March 3, 1893, p. 125) is recorded that at the Indiana Academy of Science Dr. Robert Hessler referred to “a case of that extremely rare and almost extinct form of itch known as ‘Norway itch,’ the scabies norvegica of Hebra, 1852.” The afflicted man was covered with thick, creamy white, leathery scales; some of these scales measured over an inch in diameter and  1/10 in. thick. A constant shedding of scales went on, a handful being gathered daily. They were found full of mites and eggs and riddled with passages. Under treatment the mites were killed and the skin became normal. Dr. Hessler made a calculation of the number of eggs and mites, amounting to ova and shells 7,004,000, mites in all stages 2,009,000.—F. V. T.]

The following forms may be transmitted from DOMESTIC ANIMALS to MAN:—

Sarcoptes minor, Fürstenberg, 1861.

Anus situated on the back, legs short, pedunculated ambulacra broad; living on cats (S. minor var. cati) and rabbits (S. minor var. cuniculi). In cats this mite usually lives in the cervical region, and thence spreads to the ears and head; it usually causes the death of the infected animals; it is easily transferable from cat to cat, is difficult to transmit to rabbits, but once settled on them can easily infect other rabbits. On the other hand, the transmission of the itch mite of the rabbit to the cat does not succeed. In man S. minor induces an eruption that disappears after about a fortnight.

[S. minor, Fürstenberg, 1861 (“Krätzm.,” viii, p. 218), comes in Railliet’s sub-genus Notoedres, 1893 (“Zool.,” ed. 2, p. 660). Canestrini raised this to generic rank in 1894 (Prosp. Acarof., vi, p. 724).

[There are three species: (1) N. notoedres, Mégnin = Sarcoptes alepis, Railliet and Lucet (Compt. rend. Soc. de Biol., 1893, xlv, p. 404), and Sarcoptes notoedres var. muris, Mégnin (Parasitology, 1880, pp. 172–174). This occurs on the black and brown rats and the water-vole.

[(2) N. cati, Hering, 1838 (N. acta. ac. Leop., ii, 18, xliv, p. 605, figs. 9 and 10), = Sarcoptes minor, Fürstenberg (“Krätzm.,” 1861, viii, p. 215). Found on the cat in Germany, France, Italy, and Britain.

[(3) N. cuniculi, Gerlach, 1857, “Krätzm.,” iii, figs. 20, 21. It lives on the rabbit and is found in Germany and France.—F. V. T.]

The itch mites of domestic animals, which belong to the genera Psoroptes (= Dermatodectes = Dermatocoptes) and Chorioptes (Symbiotes = Dermatophagus), as a rule do not infest and live on man, even when artificially transmitted. It is, however, possible for this to occur. Moniez (“Traité de par.,” 1896, p. 559) mentions that a species of Chorioptes—probably Ch. bovis—had been found on man, as had also Demodex folliculorum. This author also includes Dermatophagoides scheremetewskyi, Bogdanoff (Bull. soc. imp. d. natural., Moscou, 1864, xxxvii, p. 341), which has repeatedly been found on man in Moscow and Leipzig (Zürn, Ber. d. med. Ges., Leipzig, 1877, p. 38), as Chorioptes bovis.

Other References to Scabies crustosæ AND norvegica, ETC.

(1) “Ein Fall von Scabies crustosa norvegica,” Würzb. med. Zeitschr., l, pp. 134–139, pl. 3, H. Bamberger.

(2) “Ueber die Krätzmilbe (Acarus scabiei),” Notiz. a. d. Geb. d. Nat. u. Heilk., Weimar (1913), xlii (11), Oct., pp. 161–166 (1834), de Blainville.

(3) “Rapport sur le ciron de la gale (Acarus scabiei),” Ann. de Mus. d’Hist. nat., 1831; Parasitology, iv, pp. 213–232, de Blainville.

Family. Demodicidæ (Mites of the Hair-follicles).

Genus. Demodex, Owen.

Demodex folliculorum, Simon, 1842.

Syn.: Acarus folliculorum, Sim., 1843; Demodex folliculorum, Owen, 1843; Macrogaster platypus, Miescher, 1843; Simonea folliculorum, P. Gervais, 1844; Steatozoon folliculorum, Wilson, 1847.

As in Sarcoptes scabiei, numerous varieties of this species are known; the form parasitic on man lives in the hair-follicles, the meibomian and sebaceous glands, and hardly ever causes inconvenience; the male measures 0·3 mm. in length and the female about 0·4 mm. in length. The eggs 0·06 to 0·08 mm. in length, 0·04 to 0·05 mm. in breadth, and are thin-shelled. The creatures are always attached with the head end downwards in the parts mentioned; they are most frequent in the sebaceous glands of the face, by the nose, lips and forehead, but they may be present on the abdomen and on other parts of the body. They may occasionally obstruct the excretory gland ducts, thus causing inflammation of the gland (comedones); their agglomeration in the meibomian glands sets up inflammation of the margins of the eyelids. There are generally only a few specimens in a gland. According to some statements Demodex occurs in 50 per cent. of mankind and even in children; they survive the death of their hosts by several days.

[Ten distinct species of Demodex are given by Canestrini and Kramer (“Demodicidae und Sarcoptidae,” Das Tierreich, 1899, vii). The species are certainly distinct.

[The species living on the dog (D. canis, Leydig, 1844) is cosmopolitan. According to the British Medical Journal (February 22, 1913, p. 407), dog mange may be caught by humans. Whitfield and Hobday describe in the Veterinary Journal seventeen cases which have come under their observation.—F. V. T.]

Order. Pentastomida.

Family. Linguatulidæ.

[As adults they live as internal blood feeders in various birds, reptiles and mammals, especially in the nasal and respiratory passages. The larval stage occurs in another host in an encysted condition; this host is usually an animal preyed upon by the species in which the sexual forms are found. The larvæ bore through the walls of the host’s stomach and enter liver and spleen or brain, where they encyst; here they grow until they assume almost the appearance of the adult. These encysted larvæ on being eaten later make their way into the nasal passages and lungs, where they mature. Both adults and larvæ occur in man, as mentioned later.

Genus. Linguatula, Fröhlich.

Linguatula rhinaria, Pilger, 1802.

Syn.: Tænia rhinaria, Pilger, 1802; Polystoma tænioides, Rud., 1810; Linguatula tænioides, Lam., 1816; Pentastoma tænioides, Rud., 1819.

The male is white in colour, 18 to 20 mm. in length, anterior portion 3 to 4 mm. in breadth, posterior part 0·5 mm. in breadth. The female is of a yellowish colour, 8, 10, or 13 cm. long, anterior part 8 to 10 mm. and posterior part 2 mm. wide. The brownish eggs can be seen in the median line. The body is elongated, rather flat, and exhibits about ninety rings or segments with crenellated borders. The hooks round the mouth are strongly curved and are articulated to a basilar support. Eggs oval, 0·09 µ in length, 0·07 µ in breadth.

L. rhinaria, in the adult condition, lives in the nasal cavity and frontal sinus of the dog, wolf, fox, horse, goat, and occasionally of man; it causes severe catarrh, epistaxis and suppuration.

Development.—The ova, which are found in masses in the nasal mucus, already possess an embryo; they are expelled with the nasal secretion, and are swallowed by herbivorous mammals with their food, mostly by hares and rabbits, but also by sheep, goats, oxen, horses, antelopes, fallow deer, pigs, cats, and occasionally also by human beings. The young larvæ hatch out in the stomach; they possess a thickened anterior body with rudimentary mouth parts and two pairs of limbs; the body gradually tapers to a short tail.

The larvæ of the Linguatulidæ bore through the intestinal wall and reach the liver, more rarely the mesenteric glands, etc.; they here become encysted and enter a sort of pupal stage in which they lose their limbs; after several moultings and gradual growth the second larval stage, having the appearance of the adult Linguatula, sets in. About five to six months after infection the creatures have become 4 to 6 mm. long, possess eighty to ninety rings, which have a series of fine points on their posterior border; the mouth and intestine are formed, the sexual organs mature and the two pairs of hooks are near the mouth. This larval stage (fig. 372) has been known for a long time, but it was regarded as an independent species of animal, and therefore had a separate name (Linguatula serrata, Fr.; Pentastoma denticalatum, Rud., etc.).

Later these Linguatula larvæ make an attempt to escape from their hosts, and this, of course, can only be effected by means of an active migration; they leave the cysts, and according to their respective positions in the abdominal or pleural cavities they reach the bronchi or the intestine, and finally pass out; they may be again sniffed up by dogs and settle in their nasal cavities. Still this outward migration does not appear to be necessary for further development. A portion of the larvæ gain access to the nasal cavities directly through the trachea, and thus herbivorous mammals certainly become directly infected. In most cases the infection of dogs, wolves and foxes, that is, of carnivorous mammals, takes place through consuming the bodies of mammals, or parts of them, such as the liver and lungs, which are affected with the second larval form; in any case most larvæ obtain access first to the stomach of their host, from here they make an active migration through the œsophagus to the oral and nasal cavities, in which they settle. It is possible also that the same larvæ which are free in the oral cavity when the food is being eaten migrate into the nasal cavities. After being stationary a fresh skin is formed and the spine-bearing cuticula are thrown off. The male attains its full size in the fourth, and the female in the sixth month. The duration of life is stated to be from fifteen months to several years.

L. rhinaria has been observed in man in the adult as well as in the larval condition (Pentastoma denticulatum). Zenker first called attention to the occurrence of the larva in man, having found it nine times in the liver in 168 autopsies. Heschl found it twice in Vienna in twenty autopsies, Virchow found it in Würzburg and Berlin, Wagner in Leipzig (10 per cent.), and Frerichs in Breslau five times in forty-seven autopsies. The parasite is much less frequent in Switzerland. According to Klebs, one case occurs in 900 autopsies, and according to Zaeslin two cases occurred in Basle to 1,914 autopsies. In the Seamen’s Hospital in Kronstadt P. denticulatum has been found six times in 659 autopsies. It was almost always the liver that contained one or a few specimens. The parasite was very rarely found in the kidney or spleen, or encysted in the intestinal wall. The adult L. rhinaria is far more rarely observed in man.

A case reported by Landon that related to a blacksmith of Elbing is particularly interesting. This man accompanied the campaign of 1870; he soon, however, fell ill with pains in the liver, accompanied by icterus and intestinal disorders. Soon after the war, and after the symptoms were reduced to icterus and weakness, bleeding of the nose set in and continued with slight intermissions for seven years; an unpleasant sensation of pressure in the left nasal cavity set in, with inflammatory swelling of the mucous membrane. At last, in the summer of 1878, when the pressure in the nose had considerably increased, a Linguatula was expelled from the nose with a violent attack of sneezing, and lived for three days longer in water. The bleeding of the nose then ceased and the patient soon recovered. There can be no doubt that the first illness was connected with the invasion in the liver of numerous larvæ of Pentastoma, and disappeared after their encystment; one or a few of these must subsequently have found its way to the nose and settled there.

Genus. Porocephalus.

Porocephalus constrictus, v. Siebold, 1852.

Syn.: Nematoideum hominis, Diesing, 1851; Pentastomum constrictum, v. Sieb., 1852; Porocephalus constrictus, Stiles, 1893.

Porocephalus is distinguished from Linguatula by its cylindrical body and by certain internal structures. Porocephalus constrictus is at present only known in its larval stage. It is milk white in colour with golden-yellow hooklets. Number of rings, twenty-three. Length 13 mm., breadth 2·2 mm. There are no prickles on the posterior border of the annulations of the body.