Tropical Diseases/Chapter 38
CHAPTER XXXVIII
VERRUCA PERUANA
Definition.— A specific disease attended with a high mortality and characterized by fever, profound anæmia, and the development of yaws-like, fungating, prone-to-bleed, granulomatous growths on the skin and mucous membranes.
Geographical distribution. Between the 9th and 16th parallels of S. latitude, and at an elevation of from 3,000 to 10,000 feet, in certain narrow valleys of the western slopes of the Andes, an aggravated form of a peculiar disease, locally known as " verruga," is endemic.
The topical as well as the geographical range of verruga is singularly limited; it is confined to certain hot, narrow valleys or ravines, the inhabitants of neighbouring places being exempt. It is said that the disease may be acquired in merely journeying through the endemic districts, more especially if the traveller passes the night there.
Etiology.— Although out-of-door workers are most liable, all ages, classes, and both sexes, including infants, are liable to attack. In the endemic centres nearly everyone sooner or later gets the disease, and thus acquires a considerable though not absolute immunity.
The fatal experiment of Carrion, who inoculated himself with the virus from one of the characteristic sores, proved that the disease is communicable. Formerly it was believed that it attacked various domestic animals; this has been disproved. Recently monkeys have been successfully inoculated.
During the initial fever certain rod-like bodies are to be found in a large proportion of the red blood-corpuscles. They disappear when the eruption comes out, and are probably associated with or are an effect of the rapid and extreme degree of blood destruction occurring at the early stage of the disease. A paratyphoid bacillus having pathogenic properties has been isolated at this stage; it, too, vanishes on the appearance of the eruption. Chlamydozoa-like bodies have recently been described as occurring in certain spindle cells in the verruga tumours.
The disease is most prevalent during the summer months when the streams are in flood, the air hot, still, and moist, when malaria is epidemic, and when insect life is abundant. An insect transmitter is suspected, but as yet not determined. Townsend, who has made special studies locally on this point, dismisses ticks, bugs, and the ordinary human ectozoa, and inclines to regard a species of phlebotomus as the carrier.
Pathology,— A remarkable feature of this disease is the rapidity and extreme degree of blood-destruction. In bad cases the blood-count may drop in three or four days to 500,000 per c.mm., the picture being that of a pernicious anæmia. There is a marked polymorphonuclear leucocytosis with disappearance of eosinophiles; and during the later eruptive stage an eosinophilia with a mononuclear leucocytosis.
The granuloma begins as a neoplasm round the capillaries and resembles in its histology that of yaws (p. 665).
Symptoms.— The peculiar initial rheumatic-like pains and fever are apparently the same in character as those of yaws, only more severe, and, as in yaws, the constitutional symptoms subside on the appearance of the skin lesion— a granuloma macroscopically as well as microscopically identical with that of yaws. Just as in the latter disease, the eruption may be sparse or abundant, discrete or confluent. As in yaws, individual granulomata may fail to erupt; others may subside rapidly; others, again, may continue to increase, and then, after remaining stationary for a time, gradually wither, shrink, and drop off without leaving a scar. If difference there be in their clinical features between verruga and yaws, apparently it is more one of degree than of kind. In verruga the initial fever may continue for weeks, or even for months. It is very severe in many instances. Often it exhibits features like those of a malarial infection, including intermittency, profound anæmia, and sometimes enlargement of the spleen and liver. Very probably in such cases it is the outcome of a double infection— verruga attacking a malarial subject. Not infrequently in the endemic district a certain type of fever, believed to be verruga fever, proves fatal before the appearance of definite skin manifestations such as would justify a positive diagnosis. This was apparently the case with Carrion. The symptoms in his case closely resembled those of the very deadly fever referred to, which is known locally as Oroya fever.
In addition to the severity of the fever and rheumatic pains, the Peruvian disease is remarkable for the tendency to spontaneous hæmorrhage exhibited by the skin lesions. Apparently this peculiarity is attributable, like the hæmorrhages in the affection known as " mountain fever," to the diminished atmospheric pressure at great altitudes; for when the patients descend to the lower valleys, or to the sea-level, the tendency to bleeding ceases. Possibly the unusual vascularity of the swellings, which are sometimes permeated by a network of cavernous sinuses, also arises from the same circumstance.
In yaws we find no mention made of the occurrence of fungating granulomata in any situation but the skin. In verruga it would seem that the tumours may develop on mucous surfaces— in the œsophagus, the stomach, intestine, bladder, uterus, and vagina. Hence the dysphagia— a common symptom— and the occasional occurrence of hæmatemesis, melæna, hæmaturia, and bleeding from the vagina in this disease. Relapses both of the fever and of the eruption may occur.
Mortality.— The mortality ranges from 10 to 40 per cent, of those attacked. The risk is very much lessened on the appearance of the eruption.
Treatment.— Salvarsan seems to exert a specific influence, but its exact value has not been determined. Cold, it is said, tends to repress the development of the eruption; until this appears, fever and pain persist. For this reason, as well as to avoid the hæmorrhage from the lesions when they do erupt, the patients should quit the heights and descend to near the sea-level. External hæmorrhages, when they occur, must be treated by graduated pressure; otherwise the local as well as the general treatment is the same as for yaws.
Where possible, workmen in endemic districts should quit the locality before sunset. On a certain railway running through the endemic zone, on which the mortality from this disease was enormous, by Dr. Giana's advice the workmen were obliged to quit the locality before sunset; the case-incidence immediately diminished.
NOTE. Since the foregoing was written Strong has published (New York Med. Journ., March, 1914) the results of his investigations on this disease in Peru. He comes to the conclusion that Oroya fever and verruga Peruana are two distinct diseases, the former produced by a special bacillus, the germ of the latter being still unknown. He succeeded in conveying verruga Peruana to monkeys.