ABSTRACTS
257
of high grade neutral paraffin oil up to the cork, thus eliminating the air space. Paraffin
wax plugs pressed into the vial down to the layer of the semen may also be employed,
if the use of oil is not desired. The vial is then wrapped in two thicknesses of paper,
covered with two rubber thumb-stalls and placed in a refrigerator or thermos flask at
3° to 8°C. This method of preservation is suitable for semen obtained from bulls, rams
and goats but the more watery types of semen such as those of the horse and the boar,
are more satisfactorily stored at 0° to 3°C. after separating out the glairy and viscous
portion of the ejaculate and then centrifuging the sperm. Boar's sperm has been pre-
served for 56 hours after separating the gelatinous lumps and mixing it with special
dilutors. More elaborate precautions are necessary when semen is intended to be shipped
to long distances. For this, vials containing semen are wrapped in a layer of cotton wool
after which they are placed in screwcap, watertight glass-vials, which in turn are well
wrapped in cotton, held in position by rubber belts. The package is then placed in a,
vacuum bottle and tightly packed with chipped ice (no salt). In this way the sperm
can be kept alive for 30 hours. After removing the semen from the refrigerator or the
flask, its temperature should be allowed to rise very slowly by keeping it in room tem-
perature for 30 minutes and then setting it in a tepid water bath at 33° to 35°C. [S.K.S.]
The study and control of the vectors of rabies in South Africa. P. S.
SNYMAN (1940). Onderstepoort. J. Vet. Sci. and Anim. Indust. 15, 1
and 2, 9—140
T HE author in this article which has been approved for the degree of D. V. Sc. by
the University of South Africa has exhaustively dealt with the prevalence of rabies
in the Union of South Africa, the problem of vectors concerned in its spread and the
several methods investigated for their destruction. He has eventually evolved a scheme
aiming at total eradication of rabies in the Union.
In general, it has been pointed out, the control of rabies consists in preventing the
rabid animal from biting persons and other animals. Where the dog plays the principal
role in the epizootology of the disease, the methods adopted to check dissemination of
rabies are comparatively easy as dogs can be placed under proper restraint by their
owners, can be muzzled and prevented from transmitting the disease, and ownerless
dogs can be rounded up and destroyed. In addition compulsory immunization of dogs
is employed in some countries with success in spite of the fact that this method
may produce occult carriers. In countries where wild animals act as vectors, e.g. certain
species of vampire bats in parts of South America where the disease occurs mainly in
cattle, certain wild carnevora such as meercats in South Africa and jackals in some other
countries, the control problem assumes a totally different aspect. Results of observa-
tions for the past ten years show that, though the disease is identical with that found in
Europe and other countries, yet dogs play a negligible role in the dissemination of rabies
in the Union. Of the twenty cases in dogs observed by the author only two could be
accounted for by the bites of rabid dogs. This is mainly due to the comparatively small
dog population owing to the heavy tax of ten shillings per head and the severity with
which the tax is imposed and the general fear of mad dogs which causes the majority of
owners to destroy their pets on the slightest suspicion of madness. Eradication of rabies
in South Africa depends on the possibility of destroying the wild carnivora, which dis-
seminate and propagate the disease amongst themselves.
The wild animals which so far have been proved to carry and transmit rabies in
the Union are the following in order of their relative importance :—
1. Cynictis penicillata. (Yellow mongoose, yellow meercat, red meercat).
2. Genetta felina. (Spotted genet, Genet cat).
3. Felis ocreata and Felis negripes. (Wild cat, black footed cat).
4. Suricata suricatta. (Suricate, common meercat, slender-tailed meercat).
5. Geosciurus capensis. (Ground squirrel, bush tailed or fan-tail meercat).
6. Myonax pulverulentus. (Small grey mongoose, pepper and salt cat).
7. Ictonyx orangiae. (Pole cat, skunk).
8. Cynalopex chama. (Silver jackal).
In addition to the several species of animals named above, cases of rabies in the jackal
and hyena have been reported from the neighbouring territories of Rhodesia and Angola.