ABSTRACTS 405
Methylene blue as an antidote for poisoning by oat hay and other plants
containing nitrates. W. B. BRADLEY, H. F. EPPSON AND O. A. BEATH (1940).
J. Amer. Vet Med. Assoc. 96, 41-42.
I N a number of states, sudden death of cattle fed on oat hay or straw had often been
reported. The authors maintain that the cause of poisoning was due to the pre¬
sence of a high concentration of potassium nitrate in these roughages. Besides oat
hay, they found very large amounts of nitrate in a number of other plants like pigweed,
specimens of sorghum, etc. Nothing is known about the factors which are responsible
for the development of such high concentration of potassium nitrate in these plants.
When ingested by cattle, some of this potassium nitrate is reduced to nitrite which con-
verts haemoglobin into methemoglobin. This methemoglobin is incapable of giving
up its oxygen to the tissues and thus causes an anoxaemia and in severe cases death.
In order to find out an antidote against this methemoglobinaemia produced in cattle
by the ingestion of nitrates, the authors performed some feeding experiments. Three
calves were given by means of stomach tube different amounts of potassium nitrate,
the doses varying from 0.5 to 1.6 gm. per kg. body-weight. All the three animals died
and it was found that 80-90 per cent of the haemoglobin of the blood had been converted
into methemoglobin.
Ten other calves were also given similar amounts of potassium nitrate. When
the animals were showing typical symptoms of nitrate poisoning and had fallen down
due to weakness, varying amounts of a 4 per cent solution of methylene blue were in-
jected intravenously. All the animals thus treated were back on their feet within ten
to twenty minutes, but the calves which received only 0.5-0.6 gm. of methylene blue
had recurrence of the symptoms and died if allowed to go untreated any further. Two
gm. of methylene blue was quite sufficient to protect an animal weighing up to 500 lb.
against an ingestion of 14 lb. of plant materials containing about 5 per cent potassium
nitrate. Further the animals treated with 2 gm. methylene blue did not show any
recurrence of symptoms, provided any further feeding of a forage containing high per-
centage of nitrate was stopped. [S. N. R.]
Johne's disease infection in laboratory animals with aid of paraffin oil.
W. M. MOHLER (1939). J. Amer. Vet. Med. Assoc. 94, 590-594.
I N this paper the author records experiments in connection with the reproduction of
Mycobacterium paratuberculosis infection in small laboratory animals.
It has always been possible to transmit the disease to cattle and sheep by feeding
virulent cultures or ground up intestines taken from cattle immediately after death.
Early attempts to infect rabbits and guinea-pigs either by feeding or by subcutaneous
or intraperitoneal inoculations of aqueous or saline suspensions of the organism, had
failed. A new method of infection is since claimed to have been tried with success.
My. paratuberculosis was grown for one month in a liquid medium (details not given),
filtered through paper and emulsified with 2 parts of paraffin oil. This emulsion when
inoculated intraperitoneally in doses of 2 c.c. killed all guinea-pigs inoculated (7) within
32 days. P. M. lesions consisted of grayish-white foci and nodules of various size on
the surface of the liver, spleen, diaphragm and lungs, with enlargement of lymph glands.
The infection was reproduced in rabbits and guinea-pigs by using paraffin oil emulsions
or even simple saline suspensions of material from these lesions. The nodules frequently
attained some size and infiltrated deeply in those animals that lingered for some 4 to 5
months ; as a rule, the guinea-pigs thus infected died in 30 to 90 days.
Intestinal scrapings from affected cattle, antiforminised and emulsified in paraffin
oil, also killed rabbits and guinea-pigs within 6 weeks. Similar results were obtained
by using faecal material from a herd of goats in which Johne's disease had been suspected.
Rats, mice and pigeons were also found susceptible but chickens proved more re-
fractory. An instance of prenatal infection in the guinea-pig is recorded. Smears of
whole blood drawn directly from the heart of two infected guinea-pigs just before death
showed acid-fast organisms. Attempts to vaccinate guinea-pigs with heat killed cultures
of My. paratuberculosis proved unsuccessful. [R. N. M.]