Cause of the Tsetse Fly Plague

Cause oj the Tsetse Fly Plague. en able him t o carry the m to a successful issue, for we feel that, apart from their m a nifest economic importa nce, thi s and si milar s tudies in compa rative pathology are full of lessons and g uidance to the student of human pathology.Brtizslz 111edzcal Journal. CAUSE OF THE TSETSE FLY PLA GUE. AN in structive article is contributed by Mr. H. Blandford in a recent number of Nature, in which he d eals in an exhaustive manner with the r avages committed by this diminutive but m ost t e rrible scourge to live stock, and which is the most fo rmidable impediment t o colonisation in Equatorial and South Africa. The t setse is rather larger than the house fly, but is n arrower when at rest, the wings overlapping. The mouth parts form a powerful, piercing, and suctoria l beak. Local in d istribution, the fly occurs in numerous detached regions of Africa south of the E quator, its headquarters appearing to be along the Zambesi and its tributa ry the Ch ob e. "Fly coun t ry" is hot, m oist, and low alluvial g round, along rive r banks, covered with for est or scrub veg etation, a nd un in h abited save by wild animals. Within its· sharply d efined limits, w hich may extend alon g one bank only of a river, the t setse swarms ; it is .extremely a ctive, and eagerly attack s m a n or animals for the purpose of sucking blood. On m a n no effect is produced beyond t emporary irritation of which th e ext ent h as b een variously described, probably in accordance with the idiosy ncrasy of the victims. \ iVild an imals do n ot suffer; b ut domestic animals which have e ~te red fly di st rict , are seized in the course of a few days. with feve r a nd wastin g, and almos t invariably die. Book s of Africa n t ravel a re full of record s of horses, t eam s of oxen, or h e rd s of n ative cattle h aving b een d estroyed by entering fly di stricts, and on one occasion a Masai a rmy proceeding to th e attack of a n eighbo uring tribe, w as effectually routed by having incautiously crossed fly-country. R esult 0/ I nvesftgatt"o1Z. On b ehalf of the Nat al Government a research is b eing mad e by Surgeon-Major B ruce, a nd the r esults of the first three m onths' work a re just publish ed. Dr. Bruce, in a somewh at brief recap itula tion of th e characteristics and habits of th e fly, adds one important n ew fact, of which h e appears scarcely to recogni se the sig nifi cance. The fly investi g ated,.

The Veterinary Jou rnal. which is not necessarily Westwood's species, is vIvIparous, giving birth to an adult larva, which creeps about actively in search of a hiding place, where in the course of a few hours, it changes by the usual skin-hardening, to a jet black puparium. Fly disease or Nagana (a Zulu term, aptly signitying to be low or depressed in spirits) is due, according to Dr. Bruce, to the presence in the blood of a flagellate infusorian. This hcematozoon is of elon gate form, furnished with a membrane or fin running along one side of th e body, and a flagellum at one end.

Cause of tlte Disease. The hcematozoa of Nagana make their appearance, which is signalised by a rise in t emperature, in the blood after an incubation period of seven to twenty days, swimming actively among, and apparently" worrying," the corpuscles. With the progress of the disease they increase in numbers, and, at the time of their host's death, may amount in the dog, to 310,000 per cub. mm. of blood! Neither reproductive nor any other stages of the parasite are yet known, nor has it been found in the blood of any wild animal, inoculation of which (the best test for the presence of the hcematozoon) has hitherto failed to produce disease. Dr. Bruce has demonstrated that it is possible repeatedly to feed tsetse on a healthy dog without producing disease in that animal-that is, the flies possess no specific venom; but that, if allowed to draw blood from a diseased animal or the carcase of one, they will communicate Nagana to any healthy animals on which they are subsequently fed, and the same result is obtained by inoculation of diseased blood, or, in dogs, by feeding them on the flesh of an animal dead of Nagana. Thus far is the cause of the disease ascertained, as is the fact that the tsetse can serve as a transmissive agent; but the natural source, other than diseased animals, which are not known to occu.r in a wild state, whence the flies obtain the parasite is still undermined, nor is it proved that, unlike m alaria, the disease cannot be acquired by breathing the air of the fly-country. RED WATER IN QUEENSLAND. UNDER the heading of" The Cattle Tick Plague" we find the following in a recent Australasia1z :-There is every r eason to fear that the tick insect is spreading rapidly in Queensland, and from what has transpired in the matter we may conclude that the insect has become established along every route