THE MEDICAL CHRONICLE. A MONTHLY RECORD OF THE Progress of Medical Science. HIGHER ANIMAL PARASITES. A REVIEW. By I. WALKER HALL, M.D., Assistant Lecturer in Pathology, The Owens College; THE advantages of travel are advocated widely. Many of the disadvantages come under the ken of the physician. Amongst these may be mentioned the dissemination of parasitic diseases. New types of these diseases are making their appearance in Europe and in England, and the practitioner can no longer leave the knowledge and practice of tropical medicine to his brethren in the torrid zone, but must of necessity be acquainted with the symptoms, course and sequelae of many equatorial ailments. As so many of the latter are directly associated with parasitic infection, the plea of several recent writers for the more frequent examination of fæces, and particularly of those passed by patients hailing from areas of known infection, cannot be disregarded. Similarly, the extension of prophylactic measures must not be delayed. The mass of recent literature upon the higher animal parasites is somewhat explained by these considerations and is at all events a distinct manifestation of the spread of parasites, of their more frequent diagnosis and of the need for some combined effort to limit the opportunities for infection. The dwarf tapeworm, common enough in Central and Southern Europe, has now appeared in America. Ankylostoma duodenale has infected many English and some Scottish mines. An American cousin of the ankylostoma duodenale, the uncinaria (ankylostoma) americana, has been met with in Texas and the United States, and it exhibits distinctly racial characteristics. In Birmingham and the surrounding districts there is considerable irritation, itching and general restlessness, due not to political reasons but to the introduction of a nematode from the African Colonies. Bilharzia hæmatobia has been of late frequently noted and the infection is carried by those who have recently resided in Egypt, India and South Africa, particularly in the Rustenberg district of the Transvaal. This paper does not pretend to be more than an attempt to shortly review and recount some of the publications upon the higher animal parasites which have appeared during the last few months. There is little that is absolutely new, but the records are of interest in that they recall scattered facts, indicate the freshly infected areas and enumerate the variations. in clinical conditions. ANATOMY AND LIFE HISTORY. The tænia nana (hymenolepsis nana) or dwarf tapeworm is one-half to two inches in size and has 150 to 200 segments. On the head are four suckers and a rostellum with 24 to 30 hooklets. The lateral borders of the proglottides are serrated, and present one laterally situated genital pore. About 100 ova are present in each segment and their characters are so distinct that they almost invite examination. Between an inner and an outer membrane is a thick clear layer into which a number of filaments pass from the upper and lower poles. The tænia cucumerina has been met with in a child only six weeks old. In the fæces it appeared as small yellow granules like blood or drops of fat. Three weeks are necessary for its full development. The intermediate host is generally the dog or cat, but it has been found in the droppings of rats and mice, and in this case fleas or flies were suspected. The nematode found in the blood of the Birmingham patients is similar to that which occurs in "craw-craw," a disease endemic in Western Africa. It is 56 micro-millimetres long and possesses a distinct alimentary canal. Forms resembling ova are described. They are round or oval and taper slightly to form a short filament. Sometimes they surround or pass into the large lymphocytes. Heller gives some admirably clear drawings of the mature oxyuris vermicularis (pin worm), their ova and the development of embryos. About five weeks are necessary for the full growth of the worm. The life span of the filaria medinensis (guinea worm) is about twelve months, less the three weeks necessary for the preparatory metamorphosis in cyclops, so that this period must elapse between the date of infection and the appearance of the mature embryo at the surface of the body of the host, a fact of importance in diagnosis. The propagation of ankylostoma depends upon the favourable deposition of the ova. Segmentation commences as soon as the Ova are ejected, but oxygen and moisture are absolutely necessary for their development, and their growth is considerably affected by the temperature. The optimum temperature is about 25°C., although they develop rapidly between 20°C. and 30°C. The uncinaria americana or new world hook worm differs from the old world hook worm, ankylostoma duodenale, in the larger size of its eggs, in the possession of a dorsal conical median tooth projecting prominently into the buccal cavity and in the position of the vulva, which is placed in the anterior half instead of in the posterior third. The trichina spiralis is apparently resting on its laurels. No special outbreaks or variations have been recorded of late, although three cases have been examined in our own departments of Pathology and Public Health. The cercariæ of the distomum spathulatum have been found in mussels, canal fish and water plants. FREQUENCY AND DISTRIBUTION. In the fæces of 500 insane patients examined in Washington, parasites were present in 13-2 per cent. There were 15 cases with ankylostoma duodenale, 54 cases with trichuria, four cases with oxyuris vermicularis, three cases with strongyloides stercoralis, and two cases with ascaris lumbricoides. Amongst the patients were a number of soldiers who had served in the Phillipines, and in these the frequency was 42:46 per cent. The ankylostoma duodenale has appeared in high as well as in low lying lands, in tunnels and in mines, and in Porto Rico about 90 per cent. of the population are affected. It has been suggested that the filaria perstans belongs to some species of tylenchus, and that its frequency is determined by the extent of banana cultivation, but others consider that these factors do not affect either its appearance or its distribution. The symptoma tology, complications, diagnosis, prognosis and therapy of 600 cases of distoma sinense (d. spathulatum) have been described. In contrast to the distribution of the distoma pulmonale (d. ringeri), the parasite is chiefly found in low lying boggy districts. Men are attacked more frequently than women. 66 ROUTE OF INFECTION. The tænia nana may be conveyed by the food. The excreta of patients in whose blood the nematode of 99 craw-craw occurs are supposed to contaminate the food of cows and the organism is then spread by milk. The entrance of the ankylostoma duodenale is more frequently effected through the skin than was formerly thought. The filaria often follow the same route. Bilharzia hæmatobia may reach the tissues by either the mouth, anus, urethra or skin. In all cases the parasite extends rapidly, and passes into the urogenital veins producing inflammatory lesions in the kidneys, intestines and liver. The gravid females lay their eggs chiefly in the mucous coats of the bladder and rectum. The tænia cucumerina may be communicated by a flea-bite or by small insects in water or milk, as well as by the ordinary methods, and the distomum spathulatum is introduced by drinking canal water or by eating infected vegetables and raw fish. PATHOLOGY. Parasitic worms are protected from the action. of the body ferments by the production of specific anti-ferments. The latter bodies have been isolated after mechanical expression and precipitation by alcohol; they do not lose their active properties until heated to about 80°C., and when kept in sodium fluoride for a year or so can still inhibit the action of pepsin and trypsin upon fibrin. It has also been shown that extracts of ascaris lumbricoides give off considerably more CO2 than could possibly arise from normal processes, and this excess taken with the simultaneous production of valerianic and other acids is thought to indicate the presence of a ferment. The higher parasites not only act mechanically, but also give off substances injurious to the host. Those produced by the ankylostoma duodenale are thought to be hæmolytic in character, since anæmia is often present and the hæmoglobin percentage is always low. But exact estimations of the metabolism in this condition reveal none of the nitrogen changes met with in pernicious anæmia although there is a marked increase in the excretion of neutral sulphur. When blood serum, obtained from patients suffering from ankylostomiasis, is injected into rabbits, hæmoglobinæmia and hæmoglobinuria are produced. Such conditions do not follow the introduction of the serum of pernicious anæmia, malaria or the malignant cachexias into animal tissues. In the human subject the toxins are not remarkably hæmolytic, there is no urobilinuria, and the blood changes are not always characteristic, so that the toxins apparently vitiate the reparative processes by lowering the functions of the blood-forming organs. In young people ankylostomiasis is associated with a delay in the advent of puberty. Bothriocephalus latus forms substances which act similarly as regards alterations in metabolism and in the production of severe anæmia. Toxins are apparently produced by the ascaris lumbricoides, but they vary very considerably in their virulence. The mechanical action of these parasites by their wandering propensities is the more serious factor. The presence of some parasites leads to the development of a certain degree of immunity which lasts for some time. Although not strictly within the present survey, the pathology of balantidium (paramecium) coli deserves mention. Under favourable conditions this organism may become markedly pathogenetic and cause death. A patient suffered from severe diarrhoea, and the stools contained blood, mucus and the balantidium coli. Red blood corpuscles were observed within the parasite. At the autopsy the mucosa of the colon was congested, swollen and ulcerated. Microscopically, the infusoria were found in great numbers between the mucosa and submucosa, and both these layers showed acute catarrhal inflammation, necrosis and hæmorrhages. The organisms appear to act mechanically at first but at present it is not known whether they emit any chemical irritant or simply injure the vitality of the tissues and predispose to the attacks of other organisms. SYMPTOMATOLOGY. The dwarf tapeworm (tænia nana) is associated with nausea, vomiting, colic, severe diarrhoea (16 to 24 |