ABSTRACTS
43
Str. agalactiae was found in 6,406 (38.8 per cent) of the group of samples previously
mentioned. Clinical mastitis was present in 1, 284 (7.8 per cent) of these cases, but 31. 3
per cent of these clinical cases failed to yield the organism. Another disturbing factor
brought out was the fact that examinations vary so widely from week to
week even when conducted regularly by the same workers. In any group of cows
subjected to weekly examination of the milk and of teat swabs, a very high percentage
showed the organism to be present at one or more examinations. The best group of
cows in this respect showed 45.7 per cent of infection, while the poorest group showed
100 per cent. Some cows showed positive milk samples repeatedly without skin infection,
while others consistently showed skin infection without any positive results in the
milk.
It is clear that other factors may be concerned, and that a more adequate knowledge
of the pathogenesis of bovine mastitis is needed before a successful attack can be
launched. Segregation and elimination is too slow, too uncertain, and too costly.
[USIS No. 23]
Fluctuations in Numbers of Trichomonas Foetus. HAMMOND, DATUS MAND
BARLETT, DAIRD E. Amer. J. vet. Res. 6, 19.
I NITIAL infections, when induced by coitus with infected bulls, resulted in the
appearance of Trichomonas in the vagina in about one week. Counts ran
consistently high for ten days, then the numbers declined gradually, and most
cases were negative in 80 days. Early return to ostrum was characteristic of all cases
that did not develop pyometra, and all during this later period of infection Trichomonas
were scarce early in the cycle, became abundant two or three days before ostrum, and
then receded abruptly.
The authors (Hammond and Bartlett, Boltsville, Maryland) believe that when
Trichomonas does not appear in the vagina until several weeks or months following
exposure, then the females involved have been previously infected one or more times.
This is also true of females that become pregnant and than about in two to five months,
or else complete the pregnancy uninterrupted.
Initial infection is followed by rapid multiplication in the vagina, corvix and uterus,
because these organs are susceptible. This infection induces a resistance in the tissues
involved in the course of two or three weeks. Thereafter they no longer support
multiplication. The infection in the uterus persists for a longer time, because more time
is required to render the uterus resistant, and possibly because the uterus does not
always become infected at the time of exposure, but only later as a result of invasion by
organisms from the vagina.
Periodic appearance of Trichomonas in the vagina in the later stages of infection is
due to contraction of the uterus at the onset of ostrum, and a consequent discharge of
its contents. On this basis, examinations are made to best advantage in from 7 to 19 days
following initial exposure, but should be made two or three days before the expected
onset of ostrum in animals that have been previously infected (USIS, No. 32).
Hormonal Stimulution of Estrus and Ovulation in Sheep and Goats (a Review).
RALPH W. PHILLIPS, PH. D., RICHARD M. FRAPS, PH. D., AND ARCHIE H. FRANK,
D. V. M., M. A. (1945). Amer J. Vet. Res., 6, 165-179
T HE results of the many attempts to induce estrus and ovulation in anestrous sheep and
goats by the use of gonadotropic hormones may be summarized as follows:
(1) Follicular growth and ovulation can be induced in a high percentage of
animals injected with gonadotropins.
(2) Induction of estrus in conjunction with ovulation, as a result of treatments
with gonadotropins, has been quite erratic, and no satisfactory explanation of the
variable results has been found.