Etiological research on the Blindness in Calces broke out in Ehime Prefecture

Since March 1968,195 calves, mainly Holstein and partly Japanese native breeds, were kept in the paddocks in the three farms in Ehime prefecture. At the begining of March 1969,44 calves of 12 to 18 months old suddenly suffered from blindness without showing any general symptoms. The blind calves were reported as Rigiditas pupollae amaurotica, that is, the pupols of affected eyes were dilated and exhibited no response to light. By the ophtalmoscopic investigation, papilledema with hyperaemia, haemorrhage and cloudy thickening of their optic disc was found. The result of analysis on blood plasma and livers of the blind calves showed vitamin A deficiency. The histopathplogical investigations of the eyes of 12 calves showed that regressive changes, such as papilledema, intrabubar neuroatrophy, demyelinization of optic nerve and prominent atrophy of M.Sphinctor pulillae were characteristic in all cases. In one of all cases, the narrowed optic canal was also revealed. In three cases, which were examined 180 and 280 days after got sick, retinal atrophy and progressive retrobulbar neuroattrophy were foun. As congenital abnormality and lesion, frequently Arteria hyaloidea persistens was revealed and perfect atrophy of optic nerve of right side was also found in one case. The pathological chnges accompanied hypovitaminosis A in the blind calves were as follows : 1. the lesion in the retina, 2. the lesion on the optic disc, and 3. the constriction of optic nerve caused by the nerrowed optic canal. All of the blind calves in Ehime affected the lesion on the optic disc and some of them affected the lesion on the retina and optic canal. It was considered that there was a close relationship between the age of calves and these three different lesons in hypovitaminosis A. If they are kept in the condition of vitamin A deficiency immediately after birth, the calves will affect the lesion on the optic canal at the age of 5 to 12 months, and suffer from hypovitaminosis A later, the changes will appear on the optic disc, and still later, until 24 months, they will affect the lesion on the retina. Because all of the blind calves were born in the southern part of Ehime prefecture and their eyes showed a high rate of congenital abnormality, such as Arteria hyaloidea persistens, it was supposed that hereditary predisposition plays perhaps in some parts of the cause to the blindness in calves in Ehime perfecture. Furthemore, they were raised under the unfavorable conditions of outdoor feeding in the paddocks throughout the year and unusual weather, especially from January to March 1969, so they parhaps have lost physocal strength, and decreased resistance to the disease. Moreober, after the hypovitaminosis continued for long time, when the vitamin A level in the blood fell down to the lowest, simultaneously the cerebrospinal fluid pressure rose to the highest and papilledema appeared. It is concluded that the blindness in calves broke out suddenly in the condition that three factors above mentioned conbined one another. Furthemore it was supposed that hypovitaminosis D following the deficiency of sunshine plays some parts of cause of the occurrence of blindeness in calves.