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Note on immunity in cattle trypanosomiasis
GENERAL ARTICLES.
NOTE ON IMMUNITY IN CATTLE TRYPANOSOMIASIS.
By JOHN L. TODD, M.D., Associate Professor of Parasitology, M'Gill University, Montreal. 1T has long been known that the larger wild animals in Africa are often infected with trypanosomes which are pathogenic for domestic animals. The wild animals found to be infected are apparently in perfect health. For this reason it has usually been believed that they suffer very little or no harm from trypanosome infections.l It has also been known that trypanosome infections may run a very chronic course in cattle. l & 2 Indeed, it is certain that herds of cattle may thrive in apparent health although they are infected with trypanosomiasis, and for this reason it has seemed possible that cattle may possess a relative immunity to some strains of trypanosomes, and that they may even recover from infections by them. 2 At Kasongo, in the Congo Free State, there is a herd which contains about 260 cattle. The animals composing the herd were in 1904 in excellent condition, and deaths amongst them from disease were exceedingly rare. One hundred of these animals were carefully examined for trypanosomiasis, and five of them were found to be infected. One of these ~nimals \Vas kiJIed; the remaining four were removed from the herd in order that they might no longer be a source of infection for it. For the purpose of ascertaining whether these four cattle would resist exposure to a reinfection by trypanosomes they were sent to Lokandu. Lokandu is a station placed on the banks of the Congo at a distance of about 120 miles from Kasongo. The country surrounding the post is wooded and well watered, and glossin:e palpales are exceedingly plentiful. At this time there was a small herd of about eight head of cattle there; probably more than half of them were infected with trypanosomes. The parasite by which they were infected was morphologically identical with that which was found in the cattle at Kasongo. The trypanosomes seen in both of these places were thought to be trypanosoma dimorphon. The four animals found to be infected with trypanosomes at Kasongo in the fall of 1904 were sent to Lokandu in November 1905. When they reached there they were in perfect condition, and two of the cows were accompanied by healthy calves which had been dropped since their mothers had been found to be infected with trypanosomes. One of the calves died within a month after reaching Lokandu of an indefinite wasting disease. In 1906 three of the cattle originally found to be infected died of a similar disease; one died in April, the other two in November. The last of the four cattle sent from Kasongo died in January 1907. In 1908 there were at Lokandu only two animals originating from those sent from Kasongo; one of them was one of the calves sent from Kasongo, the other was a calf dropped by it. 1 Laveran and Mesnil: "Trypanosomes antI Trypanosomiasis." Translated by Nabarro. London: Bailliere, Tindall & Cox, 1907. 2 Dutton, Todd, and Kinghorn: Cattle Trypanosomiasis in the Congo Free State. " Annal& of Tropical Medicine and Parasitology," Vol. I., No 2, p. 245.
REVIEWS.
277
Since no examination was made of these cattle, it is impossible to state certainly of what disease they died. All that it is possible to be certain of, from the records furnished, is that the disease to which they succumbed was not an acute one, but that it was a more or less chronic wasting, which resembled trypanosomiasis; but, because of the frequency of trypanosomia'lis at Lokandu, it is almost certain that these animals died from that disease. Even if it is assumed that these animals did die of trypanosomiasis, it is impossible, because of the conditions of the experiment, to say with certainty whether they died of a new infection acquired at Lokandu or from the old one which they had at Kasongo; but, since all of them became ill and died within about two years after leaving Lokandu, and since none of them reached the average age attained by cattle in the Kasongo herd, it is probable that the infection which killed them was a new one. This observation certainly suggests that African cattle in fair health and apparently tolerant to one strain of a trypanosome may succumb to an infection by another strain of apparently the same parasite. 1 The practical conclusion to be drawn from this observation is that there should be great hesitation in moving cattle from place to place in Africa until very much more has been learned concerning cattle trypanosomiasis and the means of preventing and curing it. -
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!tttritws. Board of Agriculture and Fisheries. Annual Reports of the Proceedings under the Diseases of Animals Acts, Etc., for the year 1909. As usual, the bulk of this annual publication is made up by the reports of the Chief Veterinary Officer and the Assistant Secretary of the Animals Division. In these reports the experience of the Board in connection with the principal diseases dealt with under the Contagious Diseases of Animals Acts is reviewed, and many interesting facts are recorded. Among these may be noticed the fact that, out of 1484 outbreaks of swine fever confirmed during the past year, in 166 cases a definite diagnosis could not be made on the occasion of the first visit by the veterinary inspector; in 127 cases the diagnosis of swine fever was made on the second viSIt, and in nineteen of these it appears that on the occasion of the first visit the disease had been diagnosed as pneumonia and broncho-pneumonia. The fact is of interest as confirming evidence from other sources to show that the so·called swine pneumonia is in most ca&es not an independent contagious disease, but swine fever with secondary pneumonic lesions. For the first time the Chief Veterinary Officer contributes abo a Laboratory Report, in which an outline is given of the investigations which were conducted in the Board's veterinary laboratory during the past year. The report of the Assistant Secretary opens with an account of the principal provisions of the Tuberculosis Order which was introduced in 1909, and subsequently withdrawn. It is observed that the Order received a J
::'tlartin, G. : "LeH trypanosomiaBes ,Ie la Guince fraIlI;aise." Paris: A. Maloine, 190n.
NOTE ON IMMUNITY IN CATTLE TRYPANOSOMIASIS.
By JOHN L. TODD, M.D., Associate Professor of Parasitology, M'Gill University, Montreal. 1T has long been known that the larger wild animals in Africa are often infected with trypanosomes which are pathogenic for domestic animals. The wild animals found to be infected are apparently in perfect health. For this reason it has usually been believed that they suffer very little or no harm from trypanosome infections.l It has also been known that trypanosome infections may run a very chronic course in cattle. l & 2 Indeed, it is certain that herds of cattle may thrive in apparent health although they are infected with trypanosomiasis, and for this reason it has seemed possible that cattle may possess a relative immunity to some strains of trypanosomes, and that they may even recover from infections by them. 2 At Kasongo, in the Congo Free State, there is a herd which contains about 260 cattle. The animals composing the herd were in 1904 in excellent condition, and deaths amongst them from disease were exceedingly rare. One hundred of these animals were carefully examined for trypanosomiasis, and five of them were found to be infected. One of these ~nimals \Vas kiJIed; the remaining four were removed from the herd in order that they might no longer be a source of infection for it. For the purpose of ascertaining whether these four cattle would resist exposure to a reinfection by trypanosomes they were sent to Lokandu. Lokandu is a station placed on the banks of the Congo at a distance of about 120 miles from Kasongo. The country surrounding the post is wooded and well watered, and glossin:e palpales are exceedingly plentiful. At this time there was a small herd of about eight head of cattle there; probably more than half of them were infected with trypanosomes. The parasite by which they were infected was morphologically identical with that which was found in the cattle at Kasongo. The trypanosomes seen in both of these places were thought to be trypanosoma dimorphon. The four animals found to be infected with trypanosomes at Kasongo in the fall of 1904 were sent to Lokandu in November 1905. When they reached there they were in perfect condition, and two of the cows were accompanied by healthy calves which had been dropped since their mothers had been found to be infected with trypanosomes. One of the calves died within a month after reaching Lokandu of an indefinite wasting disease. In 1906 three of the cattle originally found to be infected died of a similar disease; one died in April, the other two in November. The last of the four cattle sent from Kasongo died in January 1907. In 1908 there were at Lokandu only two animals originating from those sent from Kasongo; one of them was one of the calves sent from Kasongo, the other was a calf dropped by it. 1 Laveran and Mesnil: "Trypanosomes antI Trypanosomiasis." Translated by Nabarro. London: Bailliere, Tindall & Cox, 1907. 2 Dutton, Todd, and Kinghorn: Cattle Trypanosomiasis in the Congo Free State. " Annal& of Tropical Medicine and Parasitology," Vol. I., No 2, p. 245.
REVIEWS.
277
Since no examination was made of these cattle, it is impossible to state certainly of what disease they died. All that it is possible to be certain of, from the records furnished, is that the disease to which they succumbed was not an acute one, but that it was a more or less chronic wasting, which resembled trypanosomiasis; but, because of the frequency of trypanosomia'lis at Lokandu, it is almost certain that these animals died from that disease. Even if it is assumed that these animals did die of trypanosomiasis, it is impossible, because of the conditions of the experiment, to say with certainty whether they died of a new infection acquired at Lokandu or from the old one which they had at Kasongo; but, since all of them became ill and died within about two years after leaving Lokandu, and since none of them reached the average age attained by cattle in the Kasongo herd, it is probable that the infection which killed them was a new one. This observation certainly suggests that African cattle in fair health and apparently tolerant to one strain of a trypanosome may succumb to an infection by another strain of apparently the same parasite. 1 The practical conclusion to be drawn from this observation is that there should be great hesitation in moving cattle from place to place in Africa until very much more has been learned concerning cattle trypanosomiasis and the means of preventing and curing it. -
--- -- -----~
!tttritws. Board of Agriculture and Fisheries. Annual Reports of the Proceedings under the Diseases of Animals Acts, Etc., for the year 1909. As usual, the bulk of this annual publication is made up by the reports of the Chief Veterinary Officer and the Assistant Secretary of the Animals Division. In these reports the experience of the Board in connection with the principal diseases dealt with under the Contagious Diseases of Animals Acts is reviewed, and many interesting facts are recorded. Among these may be noticed the fact that, out of 1484 outbreaks of swine fever confirmed during the past year, in 166 cases a definite diagnosis could not be made on the occasion of the first visit by the veterinary inspector; in 127 cases the diagnosis of swine fever was made on the second viSIt, and in nineteen of these it appears that on the occasion of the first visit the disease had been diagnosed as pneumonia and broncho-pneumonia. The fact is of interest as confirming evidence from other sources to show that the so·called swine pneumonia is in most ca&es not an independent contagious disease, but swine fever with secondary pneumonic lesions. For the first time the Chief Veterinary Officer contributes abo a Laboratory Report, in which an outline is given of the investigations which were conducted in the Board's veterinary laboratory during the past year. The report of the Assistant Secretary opens with an account of the principal provisions of the Tuberculosis Order which was introduced in 1909, and subsequently withdrawn. It is observed that the Order received a J
::'tlartin, G. : "LeH trypanosomiaBes ,Ie la Guince fraIlI;aise." Paris: A. Maloine, 190n.