For some weeks after the larvæ have penetrated the muscular tissues the animals show stiffness of the limbs, difficulty in moving, and in mastication, etc., but these troubles disappear in a short time.
The above facts explain why trichinosis in the pig is almost unknown in France, Italy, and Spain. It is commoner in Germany and in certain States of Europe, such as Holland and Russia, although investigations had previously shown that in Paris about 7 per cent. of the sewer rats were sufferers from trichinosis and that in Germany the percentage rose as high as 15 to 20. In Chicago and Cincinnati, U.S.A., the proportion of rats suffering from trichinosis has been as high as 50 to 70 per cent., and as in some of the Northern States pigs were bred in complete freedom, it follows that at one time very large numbers of American pigs must have suffered from trichinosis.
In consequence of sanitary precautions this proportion has since greatly diminished.
Diagnosis. During the animal’s life diagnosis is a difficult matter, though, on the other hand, simple microscopic examination of suspected meat is sufficient at once to settle the question. In dealing with the living animal, however, it is necessary, as in examining suspected meat, to obtain a fragment of muscle in order to submit it to microscopic examination. This fragment can be obtained by the method known as “harpoonage,”—a trocar provided with a cutting hook, or a trocar the canula of which has a sharp-edged opening near its end, being thrust into the muscle. On removing the trocar the elasticity of the tissues causes a fragment to project into the opening in the canula, and on withdrawing the latter a fragment sufficient for examination is obtained. One may proceed in the same way by harpoonage when examining large masses of suspected meat the surface of which reveals no lesion.
The specimen having been obtained, a few fragments of the muscular fasciculi are crushed between two glasses and examined with a low power.
The trichinæ will be found towards the ends of the muscle near the region of the tendons; few or none exist in the fat. These parasites are most readily discovered in the diaphragm, in the muscles of the shoulders and quarters, and in the psoas muscles.
Prognosis. The prognosis is relatively favourable so long as infestation is only moderate. But it is very grave from the point of view of public hygiene, on account of the possibility of persons becoming infected by eating the diseased meat.
Treatment. There is no curative treatment. Formerly it was believed that, provided the condition were early diagnosed, the intestinal form might possibly be cured by administering purgatives and vermifuges so as to prevent the embryos penetrating the system.
After Askanazy’s discoveries this view had to be abandoned, and the practitioner is necessarily powerless in dealing with the muscular form. Time alone effects improvement and a relative cure by causing caseo-calcareous degeneration of the cysts. With a prophylactic object, every precaution should be taken to prevent the possibility of pigs being contaminated. This question particularly interests America, because of the extreme prevalency of pig trichinosis there.
From the point of view of public hygiene all infected meat should be seized and destroyed, despite the fact that perfect cooking destroys the vitality of the parasites, which perish at 120° Fahr.