PARASITIC DISEASES OF CATTLE IN PUEBTO RICO 11 
disease. Probably the safest method for pure-bred cattle is by in- 
jecting blood from immune animals into those that arc susceptible. 
To insure the success of this method, natural infestations with the 
tick must be avoided. It is recommended that animals from 6 to L5 
months of age be selected for inoculation, as they are more readily 
immunized than adults. The treatment with trypan-blue should 
be used to ease the severe reactions and to reduce the Losses result- 
ing from the immunization. 
A control measure that has been tried in Puerto Rico, with vary- 
ing results, is to allow only a limited number of ticks to infest the 
susceptible imported animals. These animals are isolated, at the 
time of arrival, in a stable or bare corral, and sprayed every week 
or two with an arsenical solution. They become infested with a few 
or several ticks for a short interval, and the disease is produced, but 
the proportion of deaths is usually small when compared with the 
fatalities among uncontrolled animals. The ticks infesting these 
animals are picked up from the forage grasses. The animals should 
receive medicinal treatment as soon as they show signs of the 
disease. 
Calves of 1 year of age or less can be introduced with considerable 
safety, as the disease is usually mild and less fatal in young ani- 
mals. The importation of mature cows in an advanced stage of 
pregnanc} r should be avoided, as they are likely to succumb to the 
disease. 
ANAPLASMOSIS 
The organism Anaplaxma marginale associated with anaplas- 
mosis (fig. 2, Be) appears in stained blood smears, as a small, dark, 
dotlike object, usually on the margin of the red blood cells. The 
disease itself resembles piroplasmosis in many respects, and the two 
diseases are being confused. 
Life history. — The disease is spread by cattle ticks and other ticks. 
As in the case of piroplasmosis, the cattle tick (Boophilus cmnulatus) 
engorged on anaplasmosis carriers can transmit the disease to sus- 
ceptible animals in the next generation. Various biting flies have 
also been reported as carriers of the disease. In connection with 
the transmission of this disease it should be mentioned that anaplas- 
mosis can be carried from one animal to another by instruments 
such as hypodermic needles, lancets, and dehorning shears. 
Importance. — Apparently this disease occurs much more frequently 
among native and acclimated cattle than does piroplasmosis. Among 
these animals the percentage of fatalities is low. The higher pro- 
ducing milk cows seem to be more predisposed to the disease and 
are often attacked at the time of parturition. Animals may recover 
from the disease, but the milk production is lowered or may cease, 
and is not resumed until the next parturition. As with piroplas- 
mosis, the disease may spread rapidly among susceptible imported 
cattle and may result in a high mortality. As the period of incu- 
bation of anaplasmosis is longer than that of tick fever, an imported 
animal may recover from the latter and then in a few days or a 
few weeks suffer from an attack of anaplasmosis. 
Symptoms. — The symptoms are similar to those of tick fever ex- 
cept that the urine is rarely, if ever, blood-colored, although it may 
