Handbook of Medical Entomology Part 16

The case was complicated by various other disorders, but the symptoms given above seem to be in large part attributable to the myasis. There is nothing in the case to justify the a.s.sumption that larvae were continuously present, for years. It seems more reasonable to suppose that something in the habits of the patient favored repeated infestation. Nevertheless, a study of the various cases of intestinal myasis caused by these and other species of dipterous larvae seems to indicate that the normal life cycle may be considerably prolonged under the unusual conditions.

The best authenticated cases of myasis of the urinary pa.s.sage have been due to larvae of _Fannia_. Chevril (1909) collected and described twenty cases, of which seven seemed beyond doubt. One of these was that of a woman of fifty-five who suffered from alb.u.minuria, and urinated with much difficulty, and finally pa.s.sed thirty to forty larvae of _Fannia canicularis_.

It is probable that infestation usually occurs through eating partially decayed fruit or vegetables on which the flies have deposited their eggs. Wellman points out that the flies may deposit their eggs in or about the a.n.u.s of persons using outside privies and Hewitt believes that this latter method of infection is probably the common one in the case of infants belonging to careless mothers. "Such infants are sometimes left about in an exposed and not very clean condition, in consequence of which flies are readily attracted to them and deposit their eggs."

[Ill.u.s.tration: 101. Larva of Fannia scalaris.]

MUSCINae--The larvae of the common house-fly, _Musca domestica_, are occasionally recorded as having been pa.s.sed with the feces or vomit of man. While such cases may occur, it is probable that in most instances similar appearing larvae of other insects have been mistakenly identified.

_Muscina stabulans_ is regarded by Portschinsky (1913) as responsible for many of the cases of intestinal myasis attributed to other species.

He records the case of a peasant who suffered from pains in the lower part of the breast and intestines, and whose stools were mixed with blood. From November until March he had felt particularly ill, being troubled with nausea and vomiting in addition to the pain in his intestines. In March, his physician prescribed injections of a concentrated solution of tannin, which resulted in the expulsion of fifty living larvae of _Muscina stabulans_. Thereafter the patient felt much better, although he suffered from intestinal catarrh in a less severe form.

[Ill.u.s.tration: 102 Muscina stabulans (4). After Graham-Smith.]

CALLIPHORINae--Closely related to the Sarcophagidae are the _Calliphorinae_, to which group belong many of the so-called "blue bottle" flies. Their larvae feed upon dead animals, and upon fresh and cooked meat. Those of _Protocalliphora_, already mentioned, are ectoparasitic on living nestling birds. Larva of _Lucilia_, we have taken from tumors on living turtles. To this sub-family belongs also _Aucheromyia luteola_, the Congo floor maggot. Some of these, and at least the last mentioned, are confirmed, rather than faculative parasites. Various species of Calliphorinae are occasionally met with as facultative parasites of man.

[Ill.u.s.tration: 103. Lucilia caesar, (3). After Howard.]

_Chrysomyia macellaria_, the screw worm fly (fig. 107), is the fly which is responsible for the most serious cases of human myasis in the United States. It is widely distributed in the United States but is especially abundant in the south. While the larvae breed in decaying matter in general, they so commonly breed in the living flesh of animals that they merit rank as true parasites. The females are attracted to open wounds of all kinds on cattle and other animals and quickly deposit large numbers of eggs. Animals which have been recently castrated, dehorned, or branded, injured by barbed wire, or even by the attacks of ticks are promptly attacked in the regions where the fly abounds. Even the navel of young calves or discharges from the v.u.l.v.a of cows may attract the insect.

[Ill.u.s.tration: 104. Calliphora erythrocephala, (6). After Graham-Smith.]

Not infrequently the fly attacks man, being attracted by an offensive breath, a chronic catarrh, or a purulent discharge from the ears. Most common are the cases where the eggs are deposited in the nostrils. The larvae, which are hatched in a day or two, are provided with strong spines and proceed to bore into the tissues of the nose, even down into or through the bone, into the frontal sinus, the pharynx, larynx, and neighboring parts.

Osborn (1896) quotes a number of detailed accounts of the attacks of the _Chrysomyia_ on man. A vivid picture of the symptomology of rhinal myasis caused by the larvae of this fly is given by Castellani and Chalmers: "Some couple of days after a person suffering from a chronic catarrh, foul breath, or ozaena, has slept in the open or has been attacked by a fly when riding or driving,--_i.e._, when the hands are engaged--signs of severe catarrh appear, accompanied with inordinate sneezing and severe pain over the root of the nose or the frontal bone.

Quickly the nose becomes swollen, and later the face also may swell, while examination of the nose may show the presence of the larvae. Left untreated, the patient rapidly becomes worse, and pus and blood are discharged from the nose, from which an offensive odor issues. Cough appears as well as fever, and often some delirium. If the patient lives long enough, the septum of the nose may fall in, the soft and hard palates may be pierced, the wall of the pharynx may be destroyed. By this time, however, the course of the disease will have become quite evident by the larvae dropping out of the nose, and if the patient continues to live all the larvae may come away naturally."

For treatment of rhinal myasis these writers recommend douching the nose with chloroform water or a solution of chloroform in sweet milk (10-20 per cent), followed by douches of mild antiseptics. Surgical treatment may be necessary.

[Ill.u.s.tration: 105. Larva of a flesh fly (Sarcophaga). Caudal aspect.

Anterior stigmata. Pharyngeal skeleton.]

SARCOPHAGIDae--The larvae (fig. 105) of flies of this family usually feed upon meats, but have been found in cheese, oleomargerine, pickled herring, dead and living insects, cow dung and human feces. Certain species are parasitic in insects. Higgins (1890) reported an instance of "hundreds" of larvae of _Sarcophaga_ being vomited by a child eighteen months of age. There was no doubt as to their origin for they were voided while the physician was in the room. There are many other reports of their occurrence in the alimentary ca.n.a.l. We have recorded elsewhere (Riley, 1906) a case in which some ten or twelve larvae of _Sarcophaga_ were found feeding on the diseased tissues of a malignant tumor. The tumor, a melanotic sarcoma, was about the size of a small walnut, and located in the small of the back of an elderly lady. Although they had irritated and caused a slight haemorrhage, neither the patient nor others of the family knew of their presence. Any discomfort which they had caused had been attributed to the sarcomatous growth. The infestation occurred in mid-summer. It is probable that the adult was attracted by the odor of the discharges and deposited the living maggots upon the diseased tissues.

[Ill.u.s.tration: 106. A flesh fly (Sarcophaga), (4). After Graham-Smith.]

According to Kuchenmeister, _Sarcophaga carnaria_ (fig. 106), attracted by the odor, deposits its eggs and larvae in the v.a.g.i.n.a of girls and women when they lie naked in hot summer days upon dirty clothes, or when they have a discharge from the v.a.g.i.n.a. In malignant inflammations of the eyes the larvae even nestle under the eyelids and in Egypt, for example, produce a very serious addition to the effects of small-pox upon the cornea, as according to Pruner, in such cases perforation of the cornea usually takes place.

[Ill.u.s.tration: 107. Chrysomyia macellaria, (3).]

_Wohlfartia magnifica_ is another Sarcophagid which commonly infests man in the regions where it is abundant. It is found in all Europe but is especially common in Russia, where Portschinsky has devoted much attention to its ravages. It deposits living larvae in wounds, the nasal fossae, the ears and the eyes, causing injuries even more revolting than those described for _Chrysomyia_.

CHAPTER V

ARTHROPODS AS SIMPLE CARRIERS OF DISEASE

The fact that certain arthropods are poisonous, or may affect the health of man as direct parasites has always received attention in the medical literature. We come now to the more modern aspect of our subject,--the consideration of insects and other arthropods as transmitters and disseminators of disease.

The simplest way in which arthropods may function in this capacity is as _simple carriers_ of pathogenic organisms. It is conceivable that any insect which has access to, and comes in contact with such organisms and then pa.s.ses to the food, or drink, or to the body of man, may in a wholly accidental and incidental manner convey infection. That this occurs is abundantly proved by the work of recent years. We shall consider as typical the case against the house-fly, which has attracted so much attention, both popular and scientific. The excellent general treatises of Hewitt (1910), Howard (1911), and Graham-Smith (1913), and the flood of bulletins and popular literature render it unnecessary to consider the topic in any great detail.

THE HOUSE-FLY AS A CARRIER OF DISEASE

Up to the past decade the house-fly has usually been regarded as a mere pest. Repeatedly, however, it had been suggested that it might disseminate disease. We have seen that as far back as the sixteenth century, Mercurialis suggested that it was the agent in the spread of bubonic plague, and in 1658, Kircher reiterated this view. In 1871, Leidy expressed the opinion that flies were probably a means of communicating contagious diseases to a greater degree than was generally suspected. From what he had observed regarding gangrene in hospitals, he thought flies should be carefully excluded from wounds. In the same year, the editor of the _London Lancet_, referring to the belief that they play a useful role in purifying the air said, "Far from looking upon them as dipterous angels dancing attendance on Hygeia, regard them rather in the light of winged sponges spreading hither and thither to carry out the foul behests of Contagion."

These suggestions attracted little attention from medical men, for it is only within very recent years that the charges have been supported by direct evidence. Before considering this evidence, it is necessary that we define what is meant by "house-fly" and that we then consider the life-history of the insect.

There are many flies which are occasionally to be found in houses, but according to various counts, from 95 per cent to 99 per cent of these in warm weather in the Eastern United States belong to the one species _Musca domestica_ (fig. 108). This is the dominant house-fly the world over and is the one which merits the name. It has been well characterized by Schiner (1864), whose description has been freely translated by Hewitt, as follows:

"Frons of male occupying a fourth part of the breadth of the head.

Frontal stripe of female narrow in front, so broad behind that it entirely fills up the width of the frons. The dorsal region of the thorax dusty grey in color with four equally broad longitudinal stripes.

Scutellum gray with black sides. The light regions of the abdomen yellowish, transparent, the darkest parts at least at the base of the ventral side yellow. The last segment and a dorsal line blackish brown.

Seen from behind and against the light, the whole abdomen s.h.i.+mmering yellow, and only on each side of the dorsal line on each segment a dull transverse band. The lower part of the face silky yellow, shot with blackish brown. Median stripe velvety black. Antennae brown. Palpi black.

Legs blackish brown. Wings tinged with pale gray with yellowish base.

The female has a broad velvety back, often reddishly s.h.i.+mmering frontal stripe, which is not broader at the anterior end than at the bases of the antennae, but become so very much broader above that the light dustiness of the sides is entirely obliterated. The abdomen gradually becoming darker. The s.h.i.+mmering areas on the separate segments generally brownish. All the other parts are the same as in the male."

The other species of flies found in houses in the Eastern United States which are frequently mistaken for the house or typhoid fly may readily be distinguished by the characters of the following key:

_a._ Apical cell (R_5) of the wide wing open, i.e., the bounding veins parallel or divergent (fig. 100). Their larvae are flattened, the intermediate body segments each fringed with fleshy, more or less spinose, processes. _Fannia_

b. Male with the sides of the second and third abdominal segments translucent yellowish. The larva with three pairs of nearly equal spiniferous appendages on each segment, arranged in a longitudinal series and in addition two pairs of series of smaller processes (fig. 100) _F. canicularis_

bb. Male with blackish abdomen, middle tibia with a tubercle beyond the middle. The larva with spiniferous appendages of which the dorsal and ventral series are short, the lateral series long and feathered (fig. 101) _F. scalaris_

aa. Apical cell (R) of the wing more or less narrowed in the margin; i.

e., the bounding veins more or less converging (fig. 108).

b. The mouth-parts produced and pointed, fitted for piercing.

c. Palpi much shorter than the proboscis; a brownish gray fly, its thorax with three rather broad whitish stripes; on each border of the middle stripe and on the mesal borders of the lateral stripes is a blackish brown line. Abdomen yellowish brown; on the second, third and fourth segments are three brown spots which may be faint or even absent. The larvae live in dung. The stable-fly (fig. 110) _Stomoxys calcitrans_

cc. Palpi nearly as long as the proboscis. Smaller species than the house-fly. The horn-fly (fig. 167) _Haematobia irritans_

bb. Mouth-parts blunt, fitted for lapping.

c. Thorax, particularly on the sides and near the base of the wings with soft golden yellow hairs among the bristles. This fly is often found in the house in very early spring or even in the winter. The cl.u.s.ter-fly, _Pollenia rudis_

cc. Thorax without golden yellow hairs among the bristles.

d. The last segment of the vein M with an abrupt angle. (fig.

108). The larvae live in manure, etc. House-fly, _Musca domestica_