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The dystrophic RCS rat is one of the most important animal models available for investigating retinal degeneration. In addition to the characteristic progressive loss of neural retina the strain is hampered by a high rate of mortality during the first week of life. Death rate during this period is greatly influenced by diet. A 69% reduction in mortality was achieved by supplementing a purified diet with double the amount of AIN-76 vitamin mix. The objective of this study was to identify vitamin(s) in the AIN-76 mix responsible for the enhanced survival. The experiment determined the effect on survival of independently doubling the concentration of each vitamin present in the AIN-76 vitamin mix. This was done by single addition of individual vitamins to a complete purified diet. Survival was determined in litters whose mothers and grandmothers had been provided the supplemented diets as their sole source of food. Supplementation with riboflavin increased mortality by 19%, whereas RRR-alpha-tocopheryl acetate supplementation reduced the mortality by 73%. The effect of RRR-alpha-tocopheryl acetate was equivalent to that achieved by supplementation with complete vitamin mix. First-week survival of pups (born alive) rose from 72.3% +/- 11.0 to 92.5% +/- 3.8 when the level of vitamin E was increased from 50 to 100 IU/kg diet.

Severe degenerative myocardial disease occurred in female C3H/OUJ mice fed purified diets for 36 weeks; the diet contained 5% or 20% fat as non-hydrogenated soybean oil. Deaths of lactating females of this group (17/35 high fat diet and 7/35 low fat diet animals) were due to sudden cardiovascular collapse. Cardiomegaly with marked atrial and ventricular myocardial mineralization was seen at necropsy. Histologically, the random, myopathic foci were characterized by severe myocardial degeneration, mineralization, and fibrosis. Mural thrombosis, pulmonary arteriosclerosis, and mild myocardial inflammatory cell infiltrates were also present. Pathological changes were similar to those of dystrophic cardiac calcinosis, an incidental necropsy finding in certain mouse strains.

Clinico-pathological and parasitological studies have been performed on spontaneous and experimental coccidiosis in guinea pigs. Among 11,244 Hartley guinea pigs purchased from suppliers during 1968, 410 (3.6%) of the animals had diarrhea due to coccidiosis. The incidence rate was high in the spring and fall with a mortality rate of 14.4 per cent. A particularly high number of fatal cases were found in the spring. In experimentally induced coccidiosis, clinical signs observed were diarrhea, dehydration, weight loss and death. The diarrhea developed in all animals on the eleventh day after infection and continued for one to five days. Food and water intakes were markedly reduced after the appearance of diarrhea, followed by anorexia and dehydration. Correlating with the appearance of diarrhea was a striking drop in body weight of the guinea pigs. Death usually occurred on the third to fifth day after the onset of diarrhea. The mortality rate was 30 per cent. The major macroscopic findings were characterized by a markedly thickened wall from the ascending to the descending colon and gelatinous edema of the mesenterium of the spiral of the ascending colon. Histologically, there was marked hyperplasia of the mucosal epithelium in the colon and numerous coccidia at different stages of development within the mucus membrane. In the advanced stages of the disease, there was degeneration and desquamation of the epithelia, marked edematous change and infiltration of neutrophil leukocytes and lymphocytes into the lamina propria and submucosa, many oocysts in the lumen of the intestine and in the intestinal glands.(ABSTRACT TRUNCATED AT 250 WORDS)

2 years experience with Acomys in one laboratory confirmed the slow breeding rate found by other workers. On moving the animals to another laboratory there was a 2-5 fold increase in breeding rate. The most likely explanation of this change was the presence of copper in the drinking water at the 1st laboratory, due to the use of copper water pipes. The data relating to maintenance and breeding of acomys for 2 years at the 2nd laboratory were analyzed to provide a more representative picture of the species.

Two strains of Mongolian gerbils (Meriones unguiculatus), Tumble Brook (TUM) and Japan Medical Science (JMS), were intraperitoneally inoculated with the D variant of encephalomyocarditis virus (EMC-D) and killed 3 days later. Mortality was significantly higher in females than in males. Evidence of viral replication was detected in the heart of both strains and in the pancreas of the TUM strain. Histopathological alterations were found in the heart and pancreas. Heart lesions involved foci of necrosis with inflammatory cell infiltration and calcification in both strains. Pancreatic lesions were restricted to the exocrine glands; islets of Langerhans were rarely and secondarily involved in the extensive destruction of exocrine glands. Severe acinar cell necrosis with marked inflammatory edema was conspicuous in TUM, whereas only slight acinar cell involvement was detected in JMS gerbils. Immunoperoxidase staining showed viral antigens in intracytoplasmic vacuoles in damaged acinar cells.

Sendai virus infected a hysterectomy derived, barrier maintained breeding colony and a conventional aging rat colony. The virus produced seroconversion in the colonies followed by a 7-month period of decreasing titers. Clinical signs were absent during the months when titers were highest, and there was no increase in mortality, but multifocal interstitial pneumonia with perivascular and peribronchial cuffing by lymphocytes and plasma cells was present in rat lungs examined histologically. Such lesions were absent before the period of seroconversion. During the months of declining titers, the interstitial and perivascular lesions decreased in frequency and severity. The peribronchial lesions did not decrease, however, and were still present in many rats 7 months after the acute infection. Attempts to isolate the virus from weanling rats were unsuccessful.

Surveillance for sylvatic plague (Yersinia pestis) was conducted near Meeteetse, Wyoming (USA) from 24 May to 14 June 1985. Ten species of fleas were collected from white-tailed prairie dogs (Cynomys leucurus), and from their burrows and associated rodents. Five of these flea species and two adult prairie dogs were positive for plague. The progression of this plague epizootic appeared to be slower and the intensity was less than in previous epizootics in other prairie dog colonies. The plague epizootic occurred within the only known colony of black-footed ferrets (Mustela nigripes) and was a potential threat to the food source of this endangered species.

The possibility of production of an effective vaccine against Pseudomonas aeruginosa infections in fur-bearing animals was investigated. Twenty-three strains of Pseudomonas aeruginosa isolated from diseased chinchillas and mink were tested in mice for their immunogenic properties. Nineteen of these strains produced good immunity against homologous strains, and three of these produced also good immunity against heterologous strains. Of the remaining four strains two produced moderate immunity and two no immunity. It was found that 0.05% or 0.5% formalin added to suspensions of Pseudomonas aeruginosa or ultrasonification of the suspension produced better results than 0.5% phenol, 0.3% alcohol or heat at 100 degrees C for half an hour. Chinchillas vaccinated with two doses of formolized Pseudomonas aeruginosa bacterins were immune for 36 weeks after the second dose, while all controls died within 48 hours after being challenged. It was found that the protection afforded by the polyvalent bacterin extended beyond the strains included in the vaccine.A field survey on 34 ranches which included over 7,700 chinchillas showed very promising and encouraging results.