Serum biochemical changes in calves with Johne's disease

Residual effects of Mycobacterium avium infection on susceptibility of sheep to copper toxicity and efficacy of treatment with tetrathiomolybdate

Posthaemolytic copper poisoning (post-HCP) in one of six, one-year-old, uninfected sheep (group O) on a Mycobacterium avium experiment prompted an evaluation of copper status and hepatotoxicity in 17 surviving cohorts. Group O had higher mean plasma Cu and δ-glutamyl transferase (GGT) activity and more variable bile acid (BA) concentrations and glutamate dehydrogenase activities (GDH) than two groups infected with M avium soon after birth. Ammonium tetrathiomolybdate (TTM; 3 x 1.7 mg/kg LW) was given subcutaneously over seven days and the pelleted, complete diet replaced by hay, low in copper. Plasma BA immediately declined and was followed by GDH, but erythrocyte superoxide dismutase activity (ESOD) became severely inhibited and took 18 days to recover. Plasma BA and GDH rose sharply after 18 days in uninfected sheep and they became hypercupraemic. TTM treatment was repeated from day 42 and had removed all group differences by day 110 but only after further inhibition of ESOD. M avium infections probably lessened the severity of pre-HCP by reducing copper retention but may predispose grazing livestock to hypocupraemia. The capacity of TTM to reduce liver Cu has probably been overestimated and side effects on cuproenzyme activity underestimated.

Review of possible links between the clinical expression of paratuberculosis and deficiency of macro and micro-nutrients

Published information on aspects of the epidemiology of paratuberculosis was reviewed to examine the hypothesis that clinical expression of disease may be induced by deficiencies or imbalances of micronutrients. The progression of paratuberculosis and the development of clinical signs, although innately linked with the process of becoming infected with Mycobacterium avium subsp paratuberculosis, are mostly controlled by factors other than those predisposing to the acquisition of the organisms. There is strong evidence in the literature reviewed to suggest that soil acidification, excesses of iron and molybdenum, and deficiencies in copper and selenium and possibly other minerals and trace elements have a role in the disease process. The fact that no single nutritional supplement has been consistently found to produce clinical recovery suggests that the causal role of these factors is complex and may vary depending upon the geochemical environment. Altering the nutritional environment by appropriate trace element supplementation and liming, as well as decreasing the reliance on shallow-rooted pastures needing frequent fertiliser applications may assist in controlling the clinical expression of paratuberculosis. Such measures could produce a significant decrease in the incidence of clinical expression across flocks and herds.

Some diagnostic features of the pathogenesis of bovine paratuberculosis (Johne's disease) and serum biochemical changes after oral reinfection

Ten bull-calves were infected with 10(8) viable cells of Mycobacterium paratuberculosis per os. During the 400-day period of observation faecal and blood samples were taken from animals at 30-day intervals. Faecal samples were examined microscopically, blood samples by the CFT, AGID and LST tests. Intradermal allergic tests were carried out at PI (post infection) days 92, 217, 336, using mammalian, avian and johnin PPD. In the period of study, these efficiency indices showed fluctuations characteristic of the given tests. In the period between PI day 160 and 400 fifteen biochemical parameters were measured monthly, TRP, ALP, TRIG and CHOL were reduced by day 400, pointing to disorders of digestion and absorption. Increased activities of CK, ALD, LDH, alpha-HBDH and ALT indicated skeletal muscle and/or liver damage in the first place. Serum CK, ALD activities and TRIG and TRP concentrations may serve as useful complementary values to the specific diagnosis of paratuberculosis, particularly in the advanced stage of the disease.

Studies of the pathogenesis of Rhodococcus equi infection in foals

Pyogranulomatous pneumonia was induced in Thoroughbred foals by intranasal challenge with freeze-dried cultures of Rhodococcus equi (previously Corynebacterium equi). The incubation period was about 18 days and clinical signs were not seen for a further week. There were marked seasonal and individual foal differences in responses to infection. Elevations in serum caeruloplasmin oxidase activity and copper concentrations appeared to be sensitive indicators of infection. Serum zinc concentrations and serum alpha-mannosidase and alkaline phosphatase activities fell in the more severely infected foals. Use of trace elements and trace element-related parameters along with faecal culture for R. equi could prove useful for early diagnosis of field cases.