Another loss which is indirectly sustained by the southern cattle industry through increased freight rates is the cost, to the railroad companies, of cleaning and disinfecting the cars that carry cattle and in providing separate pens for them at various places.
These statements are sufficient to indicate that the loss to the quarantined section from the cattle tick is something enormous. Such a series of encumbrances as those recorded could be carried by the cattle industry of no other section of the country than the South, whose excellent pastures, rich soil, and salubrious climate are the only reasons for its ability to overcome such obstacles in meeting the competition of the West; and it is the inherent capacity of the South for greatly increasing its herds and enlarging its pasture lands that makes the actual loss even secondary to the potential loss from restrictions necessitated by the presence of the cattle tick. This potential loss may be described as the difference between the value of the cattle industry of the South to-day and the extent to which this industry would be increased if farmers and ranchmen were assured that their lands and cattle would not become infested with fever ticks. Could this assurance be given, the beneficial effects would extend over the entire country, because the market of the northern breeder would thereby become greatly extended.
These appalling losses and annual sacrifices of the cattle raisers of the infected district can be entirely effaced, and this at a small proportionate cost; for, with enthusiastic stockmen, satisfactory State legislation, sufficient money, and a corps of trained inspectors, the cattle tick may be exterminated, and every dollar expended in this work will be returned many times during each succeeding year.
The so-called period of incubation.—After the young ticks have attached themselves to cattle the fever appears about 10 days thereafter in midsummer. When the weather is cool, as in autumn, this period may be a little longer. The actual period of incubation may be shorter, for if blood from a case of Texas fever is injected into the blood vessels of healthy cattle the fever may appear within five days. When cattle graze upon pastures over which southern cattle have passed, the time when the disease appears varies within wide limits. When the animals have been put upon pastures immediately after southern cattle have infected them with ticks, it may take from 30 to 60 days, or even longer, before the disease appears. This will be readily understood when we recall the life history of ticks. The southern cattle leave only matured ticks which have dropped from them. These must lay their eggs and the latter must be hatched before any ticks can get upon native cattle. The shortest period is thus not less than 30 days if we include 10 days for the period of incubation after the young ticks have attached themselves to native cattle. When the infection of pastures with ticks has taken place early in the season, or when it is cold, the period is much longer, because it takes longer for the eggs to hatch.
If native cattle are placed upon pastures which have been infected with ticks some time before, the disease will appear so much sooner, because the young ticks may be already hatched and attack the cattle at once. It will be evident, therefore, that the length of time between the exposure of native cattle on infected fields and the appearance of the disease depends on the date of original infection, and on the weather, whether cold or hot. When native cattle are placed upon fields on which young ticks are already present, they will show the fever in 13 to 15 days if the season is hot.
The fever appears before the ticks have matured. In fact, they are still small enough to be overlooked. In any case very careful search should be made for them in those places which they prefer—the thighs, escutcheon, and udder. After the acute stage of the fever has passed the ticks begin to swell up and show very plainly. ([Pl. XLVI], figs. 6 and 7.)
Prevention.—It is generally accepted that if southern cattle are entirely free from that species of tick known as Margaropus annulatus they can be allowed to mingle with the most susceptible animals without danger. Furthermore, it has been learned from the study of the life history of the cattle tick and by observation that this tick infests pastures only transiently, never permanently, and will not mature except upon cattle or equines, that its extermination is possible, and that the disease it causes may be prevented. Therefore the various methods with these results in view should be directed toward the destruction of ticks on cattle as well as their eradication from the pastures.
METHODS OF ERADICATING THE TICKS.[7]
In undertaking measures for eradicating the tick it is evident that the pest may be attacked in two locations, namely, on the pasture and on the cattle.